Glossary

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• AbdomenThe area of the body between the bottom of the ribs and the top of the thighs.
• Abdominal AnginaAn acute attack of severe abdominal pain, commonly occurring after eating and often associated with weight loss, nausea, vomiting and diarrhoea. It is caused by narrowing or obstruction of the mesenteric arteries, primarily atherosclerotic in origin
• Abdominal AortaThe portion of the aorta in the abdomen
• AblationElimination or removal.
• Abnormal Heart RhythmAnother term for an arrhythmia
• Acceptance and Commitment Therapy (ACT)Acceptance and Commitment Therapy (ACT) is a form of psychological therapy that helps people develop a different relationship with difficult thoughts and feelings, rather than trying to eliminate them. In cardiac arrest recovery, ACT teaches skills to notice and accept distressing thoughts about health, vulnerability, and the future without being controlled by them, while clarifying personal values and committing to actions that make life meaningful despite ongoing uncertainty. Core(...)
• Access to WorkAccess to Work is a UK government grant scheme administered by the Department for Work and Pensions (DWP) that provides practical and financial support to disabled people or those with a long-term health condition who are in work, starting work, or doing an apprenticeship or work trial. It is designed to help people overcome disability-related barriers that standard reasonable adjustments made by an employer cannot fully address. What Access to Work can fund The scheme can contribute to(...)
• ACE InhibitorsACE inhibitors are commonly used to treat heart failure and high blood pressure and often prescribed to patients following a heart attack.
• AcetylcholineA type of chemical (called a neurotransmitter) that transmits messages among nerve cells and muscle cells.
• Acquired Brain InjuryAcquired brain injury (ABI) is any injury to the brain that occurs after birth, in contrast to congenital brain conditions present from birth. It encompasses a wide range of causes including stroke, traumatic brain injury (TBI) from falls or road accidents, brain tumours, infections such as meningitis or encephalitis, and hypoxic-ischaemic injury resulting from loss of oxygen supply to the brain. Cardiac arrest is one of the most common causes of hypoxic ABI in adults.When the heart(...)
• ABIAcquired brain injury (ABI) is any injury to the brain that occurs after birth, in contrast to congenital brain conditions present from birth. It encompasses a wide range of causes including stroke, traumatic brain injury (TBI) from falls or road accidents, brain tumours, infections such as meningitis or encephalitis, and hypoxic-ischaemic injury resulting from loss of oxygen supply to the brain. Cardiac arrest is one of the most common causes of hypoxic ABI in adults.When the heart(...)
• Acquired Heart DiseaseDisease of the heart that develops after birth, due to an infection or other disease affecting the heart muscle, heart valves or coronary arteries (compare with 'Congenital Heart Disease').
• Acute Coronary SyndromeMedical term for acute conditions associated with possible or actual heart damage due to restricted blood supply. Incorporates unstable angina, NSTEMI and STEMI. The latter two terms are also called a heart attack.
• Acute Myocardial InfarctionMedical term for a Heart Attack. The myocardium (heart muscle) is damaged, usually as a result of acute restriction of the coronary blood supply.
• Acute Respiratory Distress SyndromeWhen the lungs do not work sufficiently leading to rapid and shallow breathing.
• ARDSWhen the lungs do not work sufficiently leading to rapid and shallow breathing.
• Acute Stress ReactionAn immediate psychological response to a traumatic event, occurring within days to weeks of the experience. Symptoms can include shock, disbelief, emotional numbness, intrusive memories, nightmares, difficulty sleeping, irritability, and difficulty concentrating. An acute stress reaction is a normal response to an abnormal situation and does not necessarily mean the person will go on to develop PTSD — many people recover naturally with time, rest, and the support of those around them.(...)
• Adjustment DisorderA psychological response to a significant life change or stressor — such as surviving a cardiac arrest, receiving an ICD, or a major change in health — in which the person experiences emotional or behavioural symptoms that are distressing or interfere with daily functioning, but do not meet the full criteria for another diagnosis such as PTSD or depression. Symptoms may include low mood, tearfulness, worry, difficulty concentrating, and withdrawing from usual activities. Adjustment(...)
• Adrenaline This hormone is secreted by the adrenal glands in response to stress and other challenges to the body. The release of adrenaline causes a number of changes throughout the body, including the metabolism of carbohydrates to supply the body’s energy demands and increased arousal or alertness
• Advance Care PlanningThe process of thinking about, discussing, and documenting wishes and preferences for future healthcare, particularly in the event of serious illness or loss of capacity to make decisions. Advance care planning may include making an Advance Decision to Refuse Treatment (ADRT), appointing a Lasting Power of Attorney for health and welfare, or simply having conversations with loved ones and healthcare professionals about preferences. For people with an ICD, advance care planning often(...)
• ACPThe process of thinking about, discussing, and documenting wishes and preferences for future healthcare, particularly in the event of serious illness or loss of capacity to make decisions. Advance care planning may include making an Advance Decision to Refuse Treatment (ADRT), appointing a Lasting Power of Attorney for health and welfare, or simply having conversations with loved ones and healthcare professionals about preferences. For people with an ICD, advance care planning often(...)
• Advance Decision to Refuse TreatmentAn advance decision to refuse treatment (ADRT), sometimes called a living will, is a legally binding document in England and Wales that sets out specific medical treatments a person does not want to receive in the future, in case they are unable to make or communicate that decision at the time. Legal status Under the Mental Capacity Act 2005, a valid and applicable ADRT has the same legal force as a contemporaneous decision made by a person with full capacity. Healthcare professionals must(...)
• Advance Life SupportA structured and algorithm-driven method of life support for use in the severest of medical emergencies, especially cardiac arrest. Doctors, nurses and paramedic personnel involved in ALS receive special training in the use of equipment.
• ALSA structured and algorithm-driven method of life support for use in the severest of medical emergencies, especially cardiac arrest. Doctors, nurses and paramedic personnel involved in ALS receive special training in the use of equipment.
• Advance Trauma Life SupportThis is specifically for patients who have been subjected to major trauma, such as a serious road traffic accident
• ATLSThis is specifically for patients who have been subjected to major trauma, such as a serious road traffic accident
• Automated External DefibrillatorAn Automated External Defibrillator. A portable, battery-powered device that analyses the heart's rhythm and, if a shockable rhythm (such as ventricular fibrillation) is detected, delivers an electric shock to attempt to restore a normal heartbeat. AEDs are designed for use by non-medical bystanders — they give clear spoken and visual instructions and will only allow a shock to be delivered if the rhythm requires it. AEDs are located in many public places including railway stations,(...)
• AEDAn Automated External Defibrillator. A portable, battery-powered device that analyses the heart's rhythm and, if a shockable rhythm (such as ventricular fibrillation) is detected, delivers an electric shock to attempt to restore a normal heartbeat. AEDs are designed for use by non-medical bystanders — they give clear spoken and visual instructions and will only allow a shock to be delivered if the rhythm requires it. AEDs are located in many public places including railway stations,(...)
• Aerobic ExerciseRepetitive, rhythmic exercise involving your muscles e.g. brisk walking, cycling and swimming.
• Agonal Breathing Agonal breathing is when someone who is not getting enough oxygen is gasping for air. It is usually due to cardiac arrest or stroke. It's not true breathing. It's a natural reflex that happens when your brain is not getting the oxygen it needs to survive.  Agonal breathing is a sign that a person is near death. It's also a sign that the brain is still alive. People who have agonal breathing and are given CPR are more likely to survive cardiac arrest than people without agonal breathing.
• AirwayThe passage(s) through which the patient breathes. Naturally this is a patient’s nose and mouth. When patients are sedated and ventilated this can refer to the endotracheal tube or tracheostomy. Occasionally used as a shorthand reference to an oropharyngeal or nasopharyngeal airway – these are smaller plastic tubes that can be inserted into the patient’s nose or mouth to help keep their natural ‘airway’ open
• AlgorithmA set of precise rules or procedures programmed for example into an implantable device (pacemaker, CRT, ICD or ILR) that are designed to solve a specific problem.
• AlveoliAir sacs in the lungs where oxygen and carbon dioxide are exchanged.
• AmiodaroneAmiodarone is a powerful antiarrhythmic medication used to treat and prevent a range of serious heart rhythm disturbances, including ventricular fibrillation, ventricular tachycardia, and atrial fibrillation. It is one of the most effective antiarrhythmic drugs available but requires careful monitoring due to its complex side effect profile.Amiodarone works through multiple mechanisms (it is a class III antiarrhythmic but has properties of all four Vaughan Williams classes). It prolongs(...)
• AmnesiaFailure of memory
• Amygdala Part of the brain’s limbic system, this primitive brain structure lies deep in the centre of the brain and is involved in emotional reactions, such as anger or fear, as well as emotionally charged memories. It also influences behaviour such as feeding, sexual interest, and the immediate “fight or flight” stress reaction that helps ensure the person’s needs are met.
• AnaemiaAnaemia is a condition in which the number of red blood cells, or the amount of haemoglobin within them, is below normal, resulting in reduced oxygen-carrying capacity of the blood. Haemoglobin is the protein inside red blood cells that binds oxygen in the lungs and releases it to tissues throughout the body. When haemoglobin levels fall, the body's tissues receive less oxygen than they need, producing the characteristic symptoms of fatigue, breathlessness, pallor, and reduced exercise(...)
• Aneurysm A swelling/dilation sac-like protrusion from a blood vessel or the heart, resulting from a weakening of the vessel wall or heart muscle.
• AnginaAngina is chest pain or discomfort caused by reduced blood flow to the heart muscle, usually because of narrowed or partially blocked coronary arteries (coronary artery disease). The heart muscle is temporarily starved of oxygen, particularly during exertion or stress when demand increases.Typical angina feels like pressure, tightness, squeezing, or heaviness in the chest, often radiating to the left arm, neck, jaw, or back. It usually comes on with physical activity or emotional stress(...)
• AngiogramX-ray picture of blood vessels and cardiac chambers using contrast.
• AngiographyAn x-ray technique in which dye is injected into the chambers of your heart or the arteries that lead to your heart (the coronary arteries). The test lets doctors measure the blood flow and blood pressure in the heart chambers and see if the coronary arteries are blocked.
• AngioplastyAngioplasty is a minimally invasive, catheter-based procedure used to open narrowed or blocked blood vessels without open surgery. A thin, flexible tube (catheter) is guided through the bloodstream to the site of the blockage, where a small balloon at the catheter tip is inflated to compress the plaque or clot against the artery wall and widen the vessel. In the majority of cases, a metal mesh tube called a stent is then deployed to keep the artery open.In cardiology, the term most(...)
• ACE Inhibitor (Angiotensin-Converting Enzyme Inhibitor)An ACE inhibitor (angiotensin-converting enzyme inhibitor) is a class of medication that lowers blood pressure and reduces the workload on the heart by blocking the enzyme that converts angiotensin I into angiotensin II. Angiotensin II is a powerful vasoconstrictor: it narrows blood vessels and stimulates the release of aldosterone, a hormone that causes the kidneys to retain sodium and water, raising blood pressure. By blocking this conversion, ACE inhibitors cause blood vessels to relax(...)
• ACEAn ACE inhibitor (angiotensin-converting enzyme inhibitor) is a class of medication that lowers blood pressure and reduces the workload on the heart by blocking the enzyme that converts angiotensin I into angiotensin II. Angiotensin II is a powerful vasoconstrictor: it narrows blood vessels and stimulates the release of aldosterone, a hormone that causes the kidneys to retain sodium and water, raising blood pressure. By blocking this conversion, ACE inhibitors cause blood vessels to relax(...)
• Angiotensin II Receptor BlockerA medicine that lowers blood pressure by blocking the action of angiotensin II, a chemical in the body that causes the blood vessels to tighten (constrict)
• AnnulusThe ring around a heart valve where the valve leaflet merges with the heart muscle.
• AnomiaA problem with word finding. Impaired recall of words with no impairment of comprehension or the capacity to repeat the words. A common difficulty following acquired brain injury, including hypoxic brain injury after cardiac arrest.
• AnosmiaLoss of sense of smell.
• AnoxiaAnoxia is the complete absence of oxygen supply to a tissue or organ. It is distinguished from hypoxia, which describes a partial reduction in oxygen supply rather than total deprivation. In clinical practice, however, the terms are sometimes used interchangeably, and the boundary between severe hypoxia and true anoxia is often blurred in the context of conditions such as cardiac arrest.The brain is particularly vulnerable to anoxia. Cerebral oxygen stores are exhausted within seconds of(...)
• Anti-Tachycardia PacingAnti-tachycardia pacing (ATP) is a therapy delivered by an implantable cardioverter defibrillator (ICD) or cardiac resynchronisation therapy defibrillator (CRT-D) that attempts to stop a fast ventricular arrhythmia by delivering rapid, precisely timed pacing pulses to the heart. ATP is painless and, when effective, terminates the tachycardia without the patient being aware that any therapy was delivered. How it works When the ICD detects a ventricular tachycardia (VT) at a rate within the(...)
• Anti-Tachycardia PacingAnti-Tachycardia Pacing (ATP) is a therapy delivered by an ICD to terminate certain types of ventricular tachycardia (VT) without delivering a painful high-energy shock. The device delivers a series of rapid, precisely timed pacing pulses to interrupt and reset the abnormal rhythm. ATP is painless or barely perceptible to most patients. If ATP fails to correct the rhythm, the ICD will escalate to a shock.
• ATPAnti-Tachycardia Pacing (ATP) is a therapy delivered by an ICD to terminate certain types of ventricular tachycardia (VT) without delivering a painful high-energy shock. The device delivers a series of rapid, precisely timed pacing pulses to interrupt and reset the abnormal rhythm. ATP is painless or barely perceptible to most patients. If ATP fails to correct the rhythm, the ICD will escalate to a shock.
• Antiarrhythmic DrugsAntiarrhythmic drugs are medications used to prevent or terminate abnormal heart rhythms (arrhythmias). They work by modifying the electrical properties of heart muscle cells, affecting the ion channels that control how electrical signals are generated and conducted through the heart. Because arrhythmias arise through several different mechanisms, antiarrhythmic drugs are classified into groups based on their predominant mechanism of action.The Vaughan Williams classification is the most(...)
• AntibioticsA medicine, which may be taken by mouth as a syrup, tablet or capsule, or may be given through a drip into a vein, to prevent or treat a bacterial infection.
• Anticipatory AnxietyWorry or fear focused on something that might happen in the future, rather than on a past event. While anxiety about recurrence is common after cardiac arrest, anticipatory anxiety is distinct in that it attaches to specific forthcoming situations — for example, dreading a clinic appointment in case of bad news, anxiety before an ICD check, or fear about returning to the location of the arrest. For co-survivors, anticipatory anxiety is often present when leaving the survivor alone for the(...)
• AnticoagulantAn anticoagulant is a medication that reduces the blood's ability to clot, lowering the risk of dangerous clot formation within blood vessels. Anticoagulants are sometimes called blood thinners, although they do not literally thin the blood; they interrupt part of the clotting cascade so that clots form more slowly or not at all.Anticoagulants are used to prevent and treat a range of conditions including [atrial fibrillation](/glossary/atrial-fibrillation/) (where clots can form in the(...)
• AnticoagulationAnticoagulation refers to the use of medication to reduce the blood's ability to clot, lowering the risk of dangerous clot formation within the heart, blood vessels, or veins. Anticoagulant drugs are commonly prescribed to cardiac patients, including some cardiac arrest survivors, for conditions where clot risk is elevated. Why anticoagulation is used The most common reasons for prescribing anticoagulation in the context of cardiac and cardiac arrest care include:Atrial fibrillation(...)
• AntidepressantsAntidepressants are medicines prescribed to treat depression, anxiety disorders, obsessive-compulsive disorder (OCD), and certain other conditions. They work by affecting levels of chemical messengers (neurotransmitters) in the brain, including serotonin, noradrenaline, and dopamine. The most commonly prescribed types are selective serotonin reuptake inhibitors (SSRIs, such as sertraline, citalopram, and fluoxetine) and serotonin-noradrenaline reuptake inhibitors (SNRIs, such as(...)
• AntihypertensiveAny medicine or other therapy that lowers blood pressure.
• Antiplatelet TherapyAntiplatelet therapy refers to medications that reduce the tendency of platelets (small blood cells involved in clotting) to clump together and form blood clots within blood vessels. By inhibiting platelet aggregation, antiplatelet drugs reduce the risk of heart attacks, stroke, and stent thrombosis in people with [coronary artery disease](/glossary/coronary-artery-disease/) and related conditions.The most commonly used antiplatelet drugs in cardiac care are:- **Aspirin:** a low-dose(...)
• Antitachycardia PacingRecognized as a way to pace-terminate certain types of arrhythmias, especially slow monomorphic VT involving a reentry circuit. The idea is to deliver a few seconds of pacing stimuli to the heart at a rate faster than tachycardia
• ATPRecognized as a way to pace-terminate certain types of arrhythmias, especially slow monomorphic VT involving a reentry circuit. The idea is to deliver a few seconds of pacing stimuli to the heart at a rate faster than tachycardia
• AnxietyThis is the term used to describe experiences such as chronic fear, tension and panic attacks. Some people have an overwhelming feeling of dread that prevents them getting on with everyday life. Sleepless nights and recurring thoughts are common, as well as nausea, palpitations, dizziness and difficulty in breathing. Anxiety is the most common mental health problem people experience.
• Anxiety disordersAnxiety disorders are a group of mental health conditions in which excessive fear, worry or apprehension causes significant distress and interferes with daily life. Unlike ordinary anxiety, which is a normal response to stress, anxiety disorders involve a level of fear or worry that is disproportionate to the situation and persists over time. They are among the most common mental health conditions in the UK and are particularly prevalent in people who have survived a life-threatening event(...)
• AortaThe largest artery in the body and the main vessel to supply blood from the heart.
• Aortic ArchThe head and neck vessels arise from this part of the aorta, directing blood from the heart; the remainder of the blood then goes down to the rest of the body.
• Aortic AtresiaComplete obstruction to the aortic valve or the aorta (usually associated with Hypoplastic Left Heart Syndrome)
• Aortic Regurgitation (reflux)Backwards leakage of circulating blood from the aorta into the left ventricle due to failure of the valve to close properly or to perforation. The leak can be trivial, mild, moderate, or severe.
• Aortic StenosisNarrowing of the aortic valve resulting from a congenital defect of the valve leaflets or disease of the valve.
• Aortic ValveThe valve at the origin of the aorta, which controls flow of blood out of the heart and prevents backflow.
• ApathyA direct result of brain injury to frontal lobe structures which concern emotion, motivation and forward planning.
• AphasiaAphasia is an acquired language disorder caused by brain injury or disease that affects a person's ability to speak, understand spoken language, read or write. It arises from damage to the language-processing areas of the brain, which in most people are located in the left hemisphere, specifically in and around Broca's area (frontal lobe) and Wernicke's area (temporal lobe). Aphasia does not affect intelligence but profoundly affects the ability to communicate.Several types of aphasia(...)
• ApnoeaTemporary cessation of breathing from any cause, formally defined as a reduction in nasal airflow to less than 30% of normal for more that 10 seconds
• ApoptosisApoptosis is a form of programmed cell death, a tightly regulated biological process by which cells that are damaged, no longer needed, or potentially dangerous are dismantled in an orderly way without triggering inflammation. Unlike necrosis (which is uncontrolled cell death caused by injury or oxygen deprivation), apoptosis is a normal and essential part of development, tissue maintenance, and immune function.In the context of cardiac arrest and hypoxic brain injury, apoptosis has(...)
• Appropriate ShockA shock delivered by an ICD (Implantable Cardioverter Defibrillator) in response to a genuine life-threatening arrhythmia, such as ventricular fibrillation (VF) or ventricular tachycardia (VT). An appropriate shock means the device has correctly detected and treated a dangerous heart rhythm. Receiving an appropriate shock can be a frightening experience, and psychological support is often recommended afterwards.
• Apraxia Inability to plan and perform purposeful movements, while still having the ability to move and be aware of movements.
• ArachnoidThe middle of the three membranes covering and protecting the brain and spinal cord. The arachnoid membrane lies below the DURA mater and directly above the SUBARACHNOID SPACE.
• Cardiac ArrestCardiac arrest is the sudden cessation of the heart's normal electrical and mechanical activity, causing an immediate and complete loss of cardiac output. Without blood flowing to the brain and vital organs, consciousness is lost within seconds and death will follow within minutes unless treatment is started immediately.For a comprehensive description of cardiac arrest, its causes, what happens during and after an arrest, and the Chain of Survival, see [Cardiac(...)
• ArrhythmiaAn abnormal heartbeat.
• Arrhythmogenic cardiomyopathy Arrhythmogenic cardiomyopathy (ACM) is a rare condition where the heart’s structure can become weak. This is because the cells of the muscle tissue don’t develop as they should.The walls of your heart can become weak. And your heart might not be able to pump blood as well as it should. Sometimes you might see ACM (arrhythmogenic cardiomyopathy) being called ARVC (arrhythmogenic right ventricular cardiomyopathy). The condition used to be called ARVC because it was thought to only(...)
• ACM Arrhythmogenic cardiomyopathy (ACM) is a rare condition where the heart’s structure can become weak. This is because the cells of the muscle tissue don’t develop as they should.The walls of your heart can become weak. And your heart might not be able to pump blood as well as it should. Sometimes you might see ACM (arrhythmogenic cardiomyopathy) being called ARVC (arrhythmogenic right ventricular cardiomyopathy). The condition used to be called ARVC because it was thought to only(...)
• Arrhythmogenic Right Ventricular CardiomyopathyArrhythmogenic right ventricular cardiomyopathy (ARVC), also known as arrhythmogenic cardiomyopathy (ACM), is an inherited heart muscle disease in which the muscle of the right ventricle (and sometimes the left ventricle) is progressively replaced by fatty and fibrous tissue. This disrupts the heart's electrical conduction, creating a substrate for life-threatening ventricular arrhythmias, including ventricular tachycardia and ventricular fibrillation. Inheritance ARVC is most commonly(...)
• Arrhythmogenic Right Ventricular DysplasiaARVD is a type of cardiomyopathy with no known cause. It appears to be a genetic condition (passed down through a family’s genes). ARVD causes ventricular arrhythmias
• ARVDARVD is a type of cardiomyopathy with no known cause. It appears to be a genetic condition (passed down through a family’s genes). ARVD causes ventricular arrhythmias
• Art therapyArt therapy aims to support people’s recovery using art as a creative process and as a therapy to help people resolve emotional conflicts, be more aware about themselves, develop social skills, reduce anxiety and increase their self-esteem.
• Arterial LineAn arterial line (also called an arterial catheter or 'art line') is a thin, flexible tube inserted directly into an artery to provide continuous, real-time blood pressure monitoring and easy access for blood sampling. Unlike the intermittent readings given by a standard blood pressure cuff, an arterial line displays a beat-to-beat pressure waveform on the bedside monitor, allowing intensive care staff to detect even brief changes in blood pressure instantly. This level of precision is(...)
• Arterial lineA very thin tube (catheter) inserted into an artery to allow direct measurement of the blood pressure, the amount of oxygen and carbon dioxide in the blood.
• ArteriographyA test that is combined with cardiac catheterization to visualize an artery or the arterial system after injection of a contrast dye.
• ArteriolesSmall, muscular branches of arteries. When they contract, they raise resistance to blood flow, and blood pressure in the arteries increases.
• ArteriosclerosisA disease process, commonly called “hardening of the arteries”, which includes a variety of conditions that cause artery walls to thicken and lose elasticity.
• ArteritisInflammation of the arteries.
• ArteryAn artery is a blood vessel that carries blood away from the heart to the body's tissues and organs. Most arteries carry oxygenated blood: the left side of the heart pumps oxygen-rich blood into the aorta, the largest artery in the body, which branches progressively into smaller arteries, arterioles and finally capillaries throughout the body. The exception is the pulmonary artery, which carries deoxygenated blood from the right ventricle to the lungs.Arteries are built to withstand high(...)
• Artificial HeartA manmade heart. Also called a total artificial heart (TAH)
• Artificial ValvesThese are man made substitutes for heart valves, used to replace a defective valve.
• Ascending AortaThe first portion of the aorta, emerging from the heart’s left ventricle
• AspirinAcetylsalicylic acid; a medicine used to relieve pain, reduce inflammation, and prevent blood clots.
• AsystoleAsystole is a form of cardiac arrest in which the heart shows no electrical activity: the ECG displays a flat or near-flat line, indicating that the heart's electrical system has completely ceased to function. Asystole is a non-shockable cardiac arrest rhythm, meaning defibrillation is not an appropriate treatment, and resuscitation focuses entirely on CPR and addressing any reversible underlying cause. Distinction from ventricular fibrillation and PEA There are three broad categories of(...)
• AtaxiaAbnormal movements due to loss of co-ordination of the muscles.
• Arterial ValveArterial valve is a general term occasionally used to describe either of the two valves that control the outflow of blood from the heart's ventricles into the arterial circulation. These are the aortic valve (between the left ventricle and the aorta) and the pulmonary valve (between the right ventricle and the pulmonary artery). They are more precisely described as semilunar valves, named for the crescent shape of their three cusps.Both valves open when the ventricles contract during(...)
• AtherectomyA nonsurgical technique for treating diseased arteries with a rotating device that cuts or shaves away material that is blocking or narrowing an artery.
• AtheromaAtheroma is the fatty material that accumulates within the inner wall (intima) of an artery, forming an atherosclerotic plaque. It consists of lipid deposits, cholesterol crystals, inflammatory cells, calcium, and fibrous tissue. The term comes from the Greek word for porridge, reflecting the soft, lipid-rich content of early plaques.Atheroma develops through a process that begins with injury or dysfunction of the arterial endothelium (inner lining), triggered by risk factors including(...)
• AtherosclerosisA disease process that leads to the buildup of a waxy substance, called plaque, inside blood vessels.
• AthetosisAbnormal writhing movements, particularly of the hands, seen in a number of brain disorders and following brain injury.
• AtorvastatinAtorvastatin is a statin medication that lowers LDL (low-density lipoprotein) cholesterol and total cholesterol by inhibiting HMG-CoA reductase, an enzyme involved in cholesterol production in the liver. Reducing LDL cholesterol slows the progression of atherosclerotic plaques in the coronary arteries and significantly reduces the risk of heart attack, stroke, and cardiovascular death.Atorvastatin is commonly prescribed to cardiac arrest survivors whose event was caused by coronary(...)
• AtresiaComplete obstruction to a valve or blood vessel, so that blood cannot get past this point in the circulation and has to take an alternative route.
• Atrial FibrillationAtrial fibrillation (AF) is the most common sustained heart rhythm disorder, affecting around 1.4 million people in the UK. It occurs when disorganised electrical impulses fire from multiple sites in the atria (the heart's upper chambers), causing them to quiver rapidly and irregularly instead of contracting in a coordinated sequence. The result is an irregular, and often fast, heartbeat.AF significantly increases the risk of stroke, because blood can pool and clot in the left atrial(...)
• AFAtrial fibrillation (AF) is the most common sustained heart rhythm disorder, affecting around 1.4 million people in the UK. It occurs when disorganised electrical impulses fire from multiple sites in the atria (the heart's upper chambers), causing them to quiver rapidly and irregularly instead of contracting in a coordinated sequence. The result is an irregular, and often fast, heartbeat.AF significantly increases the risk of stroke, because blood can pool and clot in the left atrial(...)
• Atrial FlutterA type of arrhythmia in which the upper chambers of the heart (the atria) beat very fast, causing the walls of the lower chambers (the ventricles) to beat inefficiently as well
• Atrial Myxomathis is a tumour of the heart, usually of the left side, arising from septum dividing the two upper chambers.
• Atrial Natriuretic PeptideThis is produced in the artria of the heart in response to a rise in atrial pressure
• ANPThis is produced in the artria of the heart in response to a rise in atrial pressure
• Atrial Septal DefectA defect (hole) in the atrial septum which allows blood to shunt from one atrium to the other.
• ASDA defect (hole) in the atrial septum which allows blood to shunt from one atrium to the other.
• Atrial SeptumThe atrial septum is the muscular wall that separates the two upper chambers of the heart (the right atrium and the left atrium). It acts as a partition preventing the mixing of oxygenated blood returning from the lungs on the left side with deoxygenated blood arriving from the body on the right. Maintaining this separation is essential for efficient oxygenation of the blood.During fetal development, the atrial septum has an opening called the foramen ovale, which allows blood to bypass(...)
• Atrial TachycardiaA type of arrhythmia that begins in the heart’s upper chambers (the atria) and causes a very fast heart rate of 160 to 200 beats a minute. A resting heart rate is normally 60 to 100 beats a minute
• AtrioventricularRelating to the junction between the atriums and the ventricles of the heart.
• Atrioventricular BlockAn interruption or disturbance of the electrical signal between the heart’s upper two chambers (the atria) and lower two chambers (the ventricles)
• Atrioventricular BundleA bundle of modified heart muscle fibres (Purkinje fibres) passing from the atroventricular node forward to the septum between the ventricles, where it divides into right and left bundles, one for each ventricle, The fibres transmit contraction waves from the atria, via the AV node to the ventricles
• AVNRT (Atrioventricular Nodal Re-Entrant Tachycardia)AVNRT (atrioventricular nodal re-entrant tachycardia) is the most common form of paroxysmal supraventricular tachycardia (SVT) in adults. It occurs when electrical impulses travel in a rapid, self-sustaining circuit within or around the atrioventricular (AV) node, causing the heart to beat suddenly at a fast rate, typically between 140 and 220 beats per minute. Most people with AVNRT have a structurally normal heart.AVNRT arises because of dual pathways within the AV node: a fast pathway(...)
• AVNRTAVNRT (atrioventricular nodal re-entrant tachycardia) is the most common form of paroxysmal supraventricular tachycardia (SVT) in adults. It occurs when electrical impulses travel in a rapid, self-sustaining circuit within or around the atrioventricular (AV) node, causing the heart to beat suddenly at a fast rate, typically between 140 and 220 beats per minute. Most people with AVNRT have a structurally normal heart.AVNRT arises because of dual pathways within the AV node: a fast pathway(...)
• Atrioventricular NodeA group of cells in the heart located between the upper two chambers (the atria) and the lower two chambers (the ventricles) that regulates the electrical current that passes through it to the ventricles
• Atrioventricular NodeThe atrioventricular node (AV node) is a small cluster of specialised cardiac cells located at the junction between the atria (upper chambers) and the ventricles (lower chambers) of the heart. It plays a critical role in the normal cardiac conduction system, acting as both a relay station and a gatekeeper for electrical signals passing from the atria to the ventricles. Function of the AV node In a normal heartbeat, an electrical impulse begins in the sinus node (the heart's primary(...)
• AVRT (Atrioventricular Reciprocating Tachycardia)AVRT (atrioventricular reciprocating tachycardia) is a form of paroxysmal supraventricular tachycardia (SVT) caused by a re-entrant circuit that includes an accessory pathway, an abnormal electrical connection between the atria and ventricles that exists outside the normal AV node. This accessory pathway allows electrical impulses to bypass the AV node and travel directly between the atria and ventricles. The circuit loops between the normal conduction system travelling in one direction(...)
• AVRTAVRT (atrioventricular reciprocating tachycardia) is a form of paroxysmal supraventricular tachycardia (SVT) caused by a re-entrant circuit that includes an accessory pathway, an abnormal electrical connection between the atria and ventricles that exists outside the normal AV node. This accessory pathway allows electrical impulses to bypass the AV node and travel directly between the atria and ventricles. The circuit loops between the normal conduction system travelling in one direction(...)
• Atrioventricular Septal DefectAn atrioventricular septal defect (AVSD), also called an atrioventricular canal defect or endocardial cushion defect, is a congenital heart condition in which there is a defect involving both the atrial septum (the wall between the upper chambers) and the ventricular septum (the wall between the lower chambers), combined with abnormality of the mitral and tricuspid valves. In a complete AVSD, the four chambers of the heart share a common central opening, and there is a single large(...)
• Atrioventricular Synchrony The normal activation sequence of the heart in which the atria contract and then, after a brief delay, the ventricles contract. AV Synchrony optimizes the heart's output of blood and produces the greatest efficiency in the cardiovascular system
• AV synchrony The normal activation sequence of the heart in which the atria contract and then, after a brief delay, the ventricles contract. AV Synchrony optimizes the heart's output of blood and produces the greatest efficiency in the cardiovascular system
• Atrioventricular ValveAtrioventricular valves are the two valves that control blood flow from the atria (the heart's upper chambers) into the ventricles (the lower chambers), preventing backflow. The mitral valve lies between the left atrium and left ventricle, and the tricuspid valve lies between the right atrium and right ventricle. Together with the arterial (semilunar) valves at the ventricular outflow tracts, the atrioventricular valves ensure that blood flows in one direction through the heart.Both(...)
• AtriumThe atria (singular: atrium) are the two upper chambers of the heart. The right atrium receives deoxygenated blood returning from the body through the superior and inferior vena cavae, and passes it to the right ventricle. The left atrium receives oxygenated blood returning from the lungs through the pulmonary veins, and passes it to the left ventricle.The atria are thinner-walled and generate lower pressures than the ventricles, as they only need to move blood the short distance into(...)
• Austin Flint MurmurA heart murmur that is loudest in diastole and associated with a third heart sound. It is a sign of aortic regurgitation, which allows retrograde filling and rapid rise in left intraventricular pressure
• AutologousAutologous is a medical term meaning derived from oneself or relating to the patient's own body. It is used to describe procedures, tissues, or biological materials sourced from the same individual who will receive them, eliminating the risk of immune rejection or disease transmission that exists when materials are taken from another person (allograft or allogeneic source).In cardiac surgery, autologous tissue is used in several contexts. Autologous pericardium (the patient's own(...)
• Automated External DefibrillatorAn automated external defibrillator (AED) is a portable, lightweight medical device designed to deliver a controlled electric shock to the heart to restore a normal cardiac rhythm during cardiac arrest caused by ventricular fibrillation or pulseless ventricular tachycardia. AEDs are specifically designed for use by non-medical bystanders with minimal or no prior training, making them a critical component of the chain of survival for out-of-hospital cardiac arrest.When switched on, an AED(...)
• AEDAn automated external defibrillator (AED) is a portable, lightweight medical device designed to deliver a controlled electric shock to the heart to restore a normal cardiac rhythm during cardiac arrest caused by ventricular fibrillation or pulseless ventricular tachycardia. AEDs are specifically designed for use by non-medical bystanders with minimal or no prior training, making them a critical component of the chain of survival for out-of-hospital cardiac arrest.When switched on, an AED(...)
• Automatic Implantable Cardioverter DefibrillatorAutomatic Implantable Cardioverter Defibrillator (AICD) is an older term for what is now commonly called an ICD (Implantable Cardioverter Defibrillator). The word "automatic" was included in the original terminology to distinguish these devices from external defibrillators that require manual operation, but the term has been largely superseded in modern clinical practice.An AICD or ICD is a surgically implanted device that continuously monitors heart rhythm and delivers electrical(...)
• AICDAutomatic Implantable Cardioverter Defibrillator (AICD) is an older term for what is now commonly called an ICD (Implantable Cardioverter Defibrillator). The word "automatic" was included in the original terminology to distinguish these devices from external defibrillators that require manual operation, but the term has been largely superseded in modern clinical practice.An AICD or ICD is a surgically implanted device that continuously monitors heart rhythm and delivers electrical(...)
• Autonomic DysfunctionAutonomic dysfunction refers to disruption of the autonomic nervous system, which controls involuntary body functions including heart rate, blood pressure, breathing, digestion, and temperature regulation. Following cardiac arrest and hypoxic brain injury, autonomic dysfunction can arise as part of the wider neurological sequelae. Symptoms may include postural hypotension (dizziness or lightheadedness on standing), abnormal sweating, temperature dysregulation, gastrointestinal problems,(...)
• Autonomic Nervous System Part of the central nervous system that controls internal organ functions (e.g., blood pressure, respiration, intestinal function, urinary bladder control, perspiration, body temperature). Its actions are mainly involuntary.
• AutopulseThe AutoPulse is a brand of mechanical chest compression device designed to perform CPR automatically without the need for continuous manual effort from a rescuer. It applies a band across the chest that compresses the sternum rhythmically at the correct rate and depth, delivering consistent compressions that are difficult to sustain with manual CPR during a prolonged resuscitation.Mechanical CPR devices provide several advantages over manual compressions in specific situations. They(...)
• AutoregulationAutoregulation is the ability of an organ's blood vessels to maintain a relatively constant blood flow despite changes in the driving blood pressure. When blood pressure rises or falls within a certain range, the vessels in the organ automatically constrict or dilate to compensate, keeping perfusion stable.The brain has particularly powerful autoregulatory capacity. Cerebral autoregulation normally maintains stable brain blood flow across a mean arterial pressure (MAP) range of roughly(...)
• Atrioventricular Septal DefectAn atrioventricular septal defect (AVSD), also called an AV canal defect or atrioventricular canal defect, is a congenital heart condition in which there is a hole in both the atrial septum (between the upper chambers) and the ventricular septum (between the lower chambers), combined with abnormalities of the mitral and tricuspid valves, which may form a single common atrioventricular valve opening. The condition encompasses a complete form (all components present) and a partial form(...)
• AvoidanceIn the context of anxiety and PTSD, avoidance refers to behaviours aimed at preventing contact with people, places, situations, activities, or thoughts that cause distress because they are associated with a traumatic event or feared outcome. While avoidance provides short-term relief, it reinforces anxiety in the long term by preventing the person from learning that the feared situation can be tolerated. For cardiac arrest survivors and ICD patients, avoidance may include not exercising,(...)
• Avoidance BehaviourAvoidance behaviour is the tendency to steer clear of situations, activities, thoughts, feelings, or physical sensations that are associated with anxiety, distress, or perceived threat. While avoidance provides short-term relief, it typically maintains and worsens anxiety in the longer term by preventing the person from discovering that the feared situation is manageable. It is a central feature of anxiety disorders and PTSD, and is very commonly seen in cardiac arrest survivors. How(...)
• AVPUAVPU is a simple clinical assessment tool used to describe a patient's level of consciousness. The letters stand for: Alert (the patient is fully awake and aware of their surroundings), Voice (the patient responds to verbal stimulation but is not fully alert), Pain (the patient responds only to painful stimuli such as pressure or a sternal rub), and Unresponsive (no response to any stimuli). AVPU provides a rapid, standardised way to communicate a patient's neurological status between(...)
• AxonParts of nerve cells in the brain which look like small hair-like tentacles. The cells receive information via the dendrites and communicate with each other by passing electrical signals down the axons and releasing chemical signals at their ends.

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• BacteriaBacteria are single-celled microorganisms found throughout nature, including on and within the human body. The vast majority of bacteria are harmless or beneficial, but certain pathogenic bacteria can infect tissues, triggering an immune response and illness.In cardiovascular medicine, bacteria are the cause of several serious conditions. Infective endocarditis occurs when bacteria enter the bloodstream and colonise the heart's inner lining or valves, causing infected deposits(...)
• Bacterial EndocarditisBacterial endocarditis is an infection of the endocardium (the inner lining of the heart, including the heart valves) caused by bacteria. It is the most common form of infective endocarditis (IE), which is the broader term used in modern medical practice to encompass infections caused by bacteria, fungi, and other organisms.The condition occurs when bacteria enter the bloodstream and colonise the endocardial surface, particularly where there is pre-existing structural abnormality such as(...)
• Balloon AngioplastyA procedure to open a narrowed (stenosed) blood vessel using a balloon-tipped catheter threaded through the vessel. The balloon is inflated to open the diseased vessel. For cardiology, most commonly is referring to angioplasty of a coronary artery.
• Balloon CatheterA balloon catheter is a long, flexible tube with a small inflatable balloon at its tip, designed to be threaded through a blood vessel to a specific site within the circulatory system or heart. When positioned correctly, the balloon is inflated under controlled pressure to achieve a therapeutic or diagnostic purpose, then deflated and the catheter withdrawn.In coronary artery disease, balloon catheters are central to balloon angioplasty (part of percutaneous coronary intervention): the(...)
• Balloon ValvuloplastyA procedure to repair a heart valve. A balloon-tipped catheter is threaded through an artery and into the heart. The balloon is inflated to open and separate any narrowed or stiffened flaps (called leaflets) of a valve
• Basal GangliaCollections of grey matter in the deep areas of the brain, below the cerebral cortex. They are involved in the control of movement and injury may produce a disturbance resembling Parkinson's disease.
• Basic Life SupportThe provision of treatment designed to maintain adequate circulation and ventilation to a patient in cardiac arrest, without the use of drugs or specialist equipment.
• BLSThe provision of treatment designed to maintain adequate circulation and ventilation to a patient in cardiac arrest, without the use of drugs or specialist equipment.
• Benefits and Financial Support After Cardiac ArrestCardiac arrest survivors may be unable to work during recovery or may have long-term limitations that affect their earning capacity. Several benefits and financial support schemes are available through the UK benefits system. Key benefits to consider include: Employment and Support Allowance (ESA) or the equivalent Universal Credit Limited Capability for Work element, for those unable to work; Personal Independence Payment (PIP), for those with ongoing physical or cognitive difficulties(...)
• Beta-blockerBeta-blockers are a class of medication that block the effects of adrenaline (epinephrine) on the heart and blood vessels by occupying beta-adrenergic receptors. This slows the heart rate, reduces the force of the heart's contractions, lowers blood pressure, and reduces the electrical irritability of the heart muscle.In cardiac care, beta-blockers are prescribed for a wide range of conditions. After cardiac arrest, they are commonly used to suppress arrhythmias, protect the heart muscle,(...)
• BicuspidA valve that has two cusps.
• BiomarkersA biomarker (biological marker) is a measurable substance, molecule, or characteristic that indicates the presence, severity, or progression of a disease, or the body's response to a treatment. In cardiac medicine, biomarkers are blood tests that provide objective information about heart function, damage, or risk that would otherwise require more invasive investigation.Troponin (troponin I and troponin T) is the cornerstone cardiac biomarker: these proteins are released by damaged heart(...)
• BiopsyThe process by which a small sample of tissue is taken for examination.
• BisoprololBisoprolol is a cardioselective beta-blocker that primarily targets beta-1 adrenergic receptors in the heart, with minimal effect on the airways. This selectivity makes it the preferred choice over non-selective beta-blockers in patients who also have asthma or COPD, though caution is still required.Bisoprolol is one of the most widely prescribed heart medications in the UK. It is used to treat heart failure with reduced ejection fraction (where it forms part of the foundational(...)
• Blalock-Taussig ProcedureA shunt between the subclavian and pulmonary arteries used to increase the supply of oxygen-rich blood in “blue babies”
• Blood ClotA jelly-like mass of blood tissue formed by clotting factors in the blood. Clots stop the flow of blood from an injury. Clots can also form inside an artery when the artery’s walls are damaged by atherosclerotic buildup, possibly causing a heart attack or stroke
• Blood GasCommonly used shorthand for ‘blood gas analysis’. Core monitoring tool widely used in intensive care. Small blood samples (1-2mls) are taken regularly from a patient’s arterial line and processed through an analyser on the unit. Measures blood pH and levels (partial pressures) of oxygen and carbon dioxide. Results are used to adjust organ support therapies.
• Blood Gas MachineA machine that measures the blood gases.
• Blood GasesBlood gas analysis (arterial blood gas, or ABG) is a blood test that measures the levels of oxygen, carbon dioxide, and acid-base balance in the bloodstream. A small sample of arterial blood (usually taken from the radial artery at the wrist) is analysed within minutes by a bedside machine in the critical care unit or emergency department.The key values measured include: pH (blood acidity, normal 7.35 to 7.45; acidosis below 7.35 indicates poor tissue perfusion or metabolic disturbance,(...)
• Blood Oxygen LevelThe level of oxygen in the blood
• PO2The level of oxygen in the blood
• Blood PressureBlood pressure is a measure of the force that the heart and blood vessels exert on the walls of the arteries as blood flows through them. It is expressed as two numbers: systolic pressure (the peak pressure when the heart contracts and pumps blood out) over diastolic pressure (the pressure during relaxation between beats), measured in millimetres of mercury (mmHg). A normal adult blood pressure is typically around 120/80 mmHg.Blood pressure is determined by two main factors: cardiac(...)
• Blood Pressure CuffA blood pressure cuff (also called a sphygmomanometer cuff or BP cuff) is the inflatable component of a blood pressure measurement device, placed around the upper arm or occasionally the wrist to measure arterial blood pressure. When inflated, the cuff temporarily occludes blood flow in the brachial artery; as it deflates, the pressure at which blood flow returns is detected either by a stethoscope (manual technique), an electronic sensor (automated device) or a mercury or aneroid(...)
• Blood TestsBlood tests are laboratory analyses of a blood sample, used to measure substances in the blood that indicate how organs are functioning, whether disease is present, and how the body is responding to treatment. A wide range of blood tests is used in cardiac care, both during acute hospital admission and in ongoing outpatient management.Commonly used blood tests in cardiac and post-arrest care include:- **Full blood count (FBC):** measures red blood cells (including(...)
• Blood TransfusionUsually refers to an infusion of donated red blood cells (RBCs)
• Blood VesselsBlood vessels are the hollow tubular structures through which blood circulates throughout the body. There are three main types: arteries (which carry oxygenated blood away from the heart under high pressure), veins (which return deoxygenated blood to the heart under lower pressure), and capillaries (the smallest vessels, forming a network in the tissues where oxygen, nutrients, and waste products are exchanged between the blood and cells).Arterial walls are thick and muscular, allowing(...)
• Blue Baby (Cyanotic Infant)A 'blue baby' is an informal term for a newborn or infant who has a blue or purple tinge to the skin, lips or fingernails, known as cyanosis. Central cyanosis occurs when the level of deoxygenated haemoglobin in the arterial blood is elevated, giving the blood a darker colour that shows through the skin. In a newborn, this most commonly indicates a congenital heart defect that allows deoxygenated blood to bypass the lungs and enter the arterial circulation without being oxygenated,(...)
• Blue BloaterBlue bloater is an older clinical term describing one of two classically described patterns of chronic obstructive pulmonary disease (COPD). The blue bloater pattern is characterised by cyanosis (bluish discolouration from chronically low blood oxygen levels), oedema (fluid retention causing swelling, the 'bloating'), and relatively less severe breathlessness at rest compared to advanced emphysema. The underlying pathology is predominantly chronic bronchitis.In severe COPD, chronic(...)
• Body Mass IndexBody mass index (BMI) is a numerical measure used to classify body weight relative to height. It is calculated by dividing weight in kilograms by height in metres squared (kg/m²). While it is not a direct measure of body fat or health, it is widely used as a population-level screening tool to identify underweight, healthy weight, overweight and obesity.The standard BMI classifications used in the UK are: underweight (below 18.5), healthy weight (18.5 to 24.9), overweight (25 to 29.9),(...)
• BMIBody mass index (BMI) is a numerical measure used to classify body weight relative to height. It is calculated by dividing weight in kilograms by height in metres squared (kg/m²). While it is not a direct measure of body fat or health, it is widely used as a population-level screening tool to identify underweight, healthy weight, overweight and obesity.The standard BMI classifications used in the UK are: underweight (below 18.5), healthy weight (18.5 to 24.9), overweight (25 to 29.9),(...)
• BrachytherapyA procedure using radiation treatment to prevent re-blockage following angioplasty or stent placement in a coronary artery.
• BradyPrefix meaning 'slow'.
• BradycardiaAbnormally slow heartbeat.
• Brain FogA colloquial term used by many cardiac arrest survivors to describe a cluster of cognitive difficulties experienced during recovery, including mental fatigue, difficulty concentrating, slowed thinking, word-finding problems, and a general sense of mental cloudiness. Brain fog is not a clinical diagnosis but is a widely recognised and valid description of how cognitive impairment feels from the inside. It can be caused by hypoxic brain injury, the physiological effects of critical illness,(...)
• Brain Imaging Refers to various techniques, such as magnetic resonance imaging (MRI), diffusion tensor imaging (DTI), and positron emission tomography (PET), that enable scientists to capture images of brain tissue and structure and to reveal what parts of the brain are associated with behaviours or activities. Structural brain imaging is concerned with identifying the anatomy of the brain and its changes with disease. Functional brain imaging is concerned with identifying the pattern of activity in(...)
• Brain Natriuretic PeptideBlood enzyme which can be measured to diagnose Heart Failure (HF)
• Brain plasticityBrain plasticity, also known as neuroplasticity, is the brain's ability to reorganise itself by forming new neural connections in response to learning, experience, or injury. It encompasses synaptic plasticity (changes in the strength of connections between existing neurons) and structural plasticity (the growth of new connections, axonal sprouting, and in limited regions the generation of new neurons). Plasticity is the biological foundation of learning, memory, and recovery from brain(...)
• Brain Stem DeathThe irreversible cessation of all brain stem function, confirmed by specific clinical tests carried out by two senior doctors. Brain stem death means the person has permanently lost the capacity for consciousness, breathing, and all other brain stem functions — they cannot recover. In the UK, brain stem death is legally and medically accepted as death, even if the heart continues to beat with ventilator support. When brain stem death is diagnosed, the clinical team will explain the(...)
• BrainstemThe lower extension of the brain where it connects to the spinal cord. Neurological functions located in the brain stem include those necessary for survival (breathing, heart rate) and for arousal (being awake and alert).
• Mechanical VentilatorA mechanical ventilator (sometimes called a breathing machine or life support machine) is a device that delivers controlled breaths to a patient who cannot breathe effectively on their own. It connects to the patient via an endotracheal tube (passed through the mouth into the windpipe) or a tracheostomy tube.The ventilator can take over all breathing (controlled ventilation, used when the patient is heavily sedated or paralysed), assist the patient's own breathing efforts while providing(...)
• Bridge to TransplantUse of mechanical circulatory support to keep heart failure patients alive until a donor heart becomes available
• Broca's areaAn area of the brain crucial to language processing, speech production and understanding
• BronchoscopeThis procedure is carried out using a fibre-optic camera device. The bronchoscope is passed through the patient’s breathing tube into the air passages leading to the lungs allowing the doctor to see into the airways of the lungs
• Brugada SyndromeA genetic heart condition in which the electrical system of the heart malfunctions despite the heart's structure appearing normal. Caused by mutations in the SCN5A gene (which controls sodium channels in heart cells), Brugada syndrome produces a characteristic pattern on an ECG and predisposes affected individuals to potentially fatal ventricular arrhythmias, most often at rest or during sleep. It is more common in men and in those of South-East Asian descent. An ICD is the main treatment(...)
• BruitA sound made in the blood vessels resulting from turbulence, perhaps because of a buildup of plaque or damage to the vessels.
• Bundle Branch BlockBundle branch block (BBB) is an abnormality of the heart's electrical conduction system in which one of the two main branches carrying electrical impulses to the ventricles (the left or right bundle branch) is partially or completely blocked. This forces the affected ventricle to depolarise more slowly via an alternative route, producing a characteristic widened QRS complex on the ECG.There are two main types. Left bundle branch block (LBBB) affects the left ventricle and is more often(...)
• BypassSurgery that can improve blood flow to the heart (or other organs and tissues) by providing a new route, or “bypass” around a section of clogged or diseased artery.
• Bypass OperationAn operation needing 'Heart Lung Bypass'. This refers to the use of the heart lung bypass machine, which takes over the function of the heart and the lungs, pumping blood round the body and supplying oxygen to the blood. (When people refer to a 'double bypass' or 'triple bypass' operation, etc., they are usually referring to an operation to provide a bypass for blocked coronary arteries, usually in adults with Coronary Heart Disease. This is not the same as a Bypass Operation, although(...)
• BystanderIn the context of cardiac arrest, a bystander is anyone who is present at the scene when a cardiac arrest occurs — whether or not they take action. A bystander may be a stranger in a public place, a colleague at work, or a family member at home. The term is used without judgement: many bystanders are overwhelmed or untrained, and any response — including calling 999 — is valuable. When a bystander does perform CPR or uses an AED, they significantly improve the survivor's chances. For(...)
• Bystander CPRCPR (cardiopulmonary resuscitation) performed by a member of the public — a bystander — before emergency services arrive. Bystander CPR can double or triple the chance of survival from out-of-hospital cardiac arrest by maintaining blood flow to the brain and vital organs until defibrillation can be delivered. Current UK guidelines (Resuscitation Council UK) recommend hands-only CPR for bystanders — 30 hard, fast chest compressions in the centre of the chest, repeated continuously. Anyone(...)

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• Calcium Channel BlockerA medicine that lowers blood pressure by regulating calcium-related electrical activity in the heart
• Calcium Channel Blocker (or calcium blocker)A class of drug used to treat angina, hypertension and sometimes arrhythmias.
• CannulaA very small tube introduced into a vein to provide access for a 'drip'
• CapillaryA microscopic blood vessel connecting arteries to veins. The blood constituents seep through these tiny vessels in the systemic (body) circulation and pulmonary (lung) circulation. Their walls are extremely thin and allow oxygen, carbon dioxide, glucose and other chemicals to pass to and fro between the blood and the surrounding cells in the body organs, or air sacs in the lungs.
• Carbon DioxideCarbon dioxide (CO2) is a colourless gas produced as a waste product of cellular metabolism when cells use oxygen to generate energy from glucose. It is transported in the blood (mainly as bicarbonate) to the lungs, where it is exhaled.In the context of cardiac and critical care, monitoring carbon dioxide levels is important for several reasons. The level of CO2 in arterial blood (PaCO2, measured by blood gas analysis) reflects the adequacy of ventilation. A rising PaCO2 indicates that(...)
• CardiacPertaining to the heart.
• Cardiac AmyloidosisCardiac amyloidosis is a condition in which abnormal misfolded proteins (called amyloid fibrils) accumulate within the heart muscle, disrupting its structure and function. As amyloid deposits build up in the myocardium, the heart walls become abnormally thick and rigid, impairing the heart's ability to fill during diastole and, in advanced disease, its ability to pump during systole. The resulting heart failure is called restrictive cardiomyopathy, and the condition is sometimes described(...)
• Cardiac ArrestCardiac arrest is the sudden and unexpected cessation of effective pumping by the heart, causing blood flow to the brain, lungs, and body to stop. It is a medical emergency: without immediate treatment, irreversible brain damage begins within 4 to 6 minutes, and death follows within minutes. Cardiac arrest is distinct from a heart attack, which is caused by a blockage in the coronary arteries; a heart attack may trigger cardiac arrest, but cardiac arrest can also occur for many other(...)
• Cardiac Arrest at WorkCardiac arrest at work describes a sudden cardiac arrest that occurs in a workplace setting. It raises specific considerations for both the survivor and employer, including legal duties, return to work planning, and psychological recovery. For employers, a cardiac arrest at work triggers duties under health and safety legislation. All workplaces with 50 or more employees are encouraged to have a trained first-aider and an accessible AED. Following an arrest, the employer may need to(...)
• Cardiac Arrest SurvivorA person who has experienced a cardiac arrest and survived. Survival rates from out-of-hospital cardiac arrest remain low overall, though outcomes are improving with greater public awareness of CPR and wider availability of AEDs. Survivors face a wide range of physical, cognitive, and psychological challenges during recovery, including fatigue, memory difficulties, anxiety, PTSD, and adjustment to living with an ICD. Each survivor's experience is unique, and peer support — connecting with(...)
• Cardiac Arrest Survivorship ClinicA cardiac arrest survivorship clinic is a specialist follow-up service designed to address the full range of needs of cardiac arrest survivors, including physical, cognitive, psychological, and practical concerns. These clinics have developed in recognition that standard cardiology follow-up, which typically focuses on the underlying cardiac condition and device management, often does not adequately address the broader challenges of life after cardiac arrest. What a survivorship clinic(...)
• Cardiac CachexiaCardiac cachexia is a syndrome of involuntary and progressive loss of body weight, muscle mass, and fat stores occurring as a direct consequence of severe heart disease, most commonly advanced heart failure. It represents a complex metabolic disturbance rather than simple malnutrition: cachexia occurs even when caloric intake appears adequate, driven by a chronic inflammatory state, neurohormonal activation, and reduced gut absorption.The mechanisms include chronically elevated(...)
• Cardiac CatheterisationCardiac catheterisation is a procedure in which a thin, flexible tube (catheter) is inserted into a blood vessel and guided to the heart or coronary arteries under X-ray imaging (fluoroscopy). It allows the heart's structure, pressures, and blood flow to be directly measured and visualised, and forms the basis for most interventional cardiac procedures.The catheter is most commonly inserted through the radial artery at the wrist (radial access), which has become the preferred approach in(...)
• Cardiac Device and Airport SecurityPeople with implanted cardiac devices including ICDs and pacemakers are generally safe to travel through airports, but need to be aware of security screening procedures. Modern implanted devices are not triggered by standard walk-through metal detectors or airport body scanners, and the devices themselves are not adversely affected by the security process. However, there are some practical considerations. Walk-through metal detectors and body scanners should not cause device interference(...)
• Cardiac DopplerCardiac Doppler refers to the use of Doppler ultrasound technology specifically within the heart to assess blood flow through the cardiac chambers and valves. It is a core component of every echocardiogram (heart ultrasound) and provides information that anatomical imaging alone cannot supply.By detecting the velocity and direction of blood movement within the heart, cardiac Doppler allows clinicians to: quantify the severity of valve narrowing or leaking; estimate pressures on the right(...)
• Cardiac Enzyme TestsBlood tests which measure the level of certain enzymes (usually Troponin but also CK) in your blood which are released by heart muscle (myocardium) during a heart attack.
• Cardiac EnzymesComplex substances capable of speeding up certain biochemical processes in the heart muscle. Abnormal levels of these enzymes signal heart attack
• Cardiac Heart FailureCardiac heart failure is an alternative term for heart failure, sometimes used in clinical documentation and older medical literature. The word 'cardiac' is occasionally added to distinguish the condition from other forms of organ failure (such as renal or hepatic failure), though in current clinical use 'heart failure' is the standard term. The condition is also sometimes called congestive heart failure (CHF), reflecting the accumulation of fluid that builds up in the lungs and body when(...)
• Cardiac MRICardiac magnetic resonance imaging (cardiac MRI, or CMR) is an advanced imaging technique that provides detailed pictures of the heart's structure, function, and tissue characteristics without using ionising radiation. It is one of the most informative investigations available in cardiology and plays an important role in diagnosing the cause of cardiac arrest and guiding ongoing management. What cardiac MRI can show Unlike an echocardiogram, which primarily shows structure and movement,(...)
• Cardiac Navigation SystemThree-dimensional mapping of electromechanical function of the heart to assess blood flow.
• Cardiac Nurse SpecialistA cardiac nurse specialist (CNS) is an advanced practice nurse with specialist training and expertise in a specific area of cardiology. Cardiac nurse specialists play a central role in the care of cardiac arrest survivors, providing clinical support, patient education, coordination of care, and a key point of contact between patients and the wider cardiology team. What cardiac nurse specialists do Depending on their area of specialisation, a CNS may:Run specialist clinics (for example,(...)
• Cardiac OutputCardiac output (CO) is the total volume of blood the heart pumps per minute. It is the product of heart rate (beats per minute) and stroke volume (the volume of blood ejected with each heartbeat): CO = heart rate x stroke volume. In a healthy adult at rest, cardiac output is typically 4 to 6 litres per minute, rising substantially during exercise as both heart rate and stroke volume increase.Cardiac index (CI) adjusts cardiac output for body size by dividing by body surface area (litres(...)
• Cardiac RehabilitationCardiac rehabilitation (often called "cardiac rehab") is a structured programme of exercise, education, and psychological support designed to help people recover from heart events and reduce the risk of future problems. It is recommended for cardiac arrest survivors as part of their recovery pathway. What cardiac rehab involves A standard cardiac rehabilitation programme typically includes:Supervised exercise sessions: gradually increasing physical activity in a monitored environment,(...)
• Cardiac Resynchronisation TherapyCardiac resynchronisation therapy (CRT) is a specialised form of pacemaker treatment used in people with heart failure whose ventricles beat in an uncoordinated way. By pacing both ventricles simultaneously, CRT resynchronises the heart's pumping action, improves cardiac output, and reduces heart failure symptoms. Why the ventricles can fall out of sync In a healthy heart, the left and right ventricles contract at almost exactly the same time, producing an efficient, coordinated beat. In(...)
• Cardiac Resynchronisation Therapy-Defibrillator (CRT-D)A cardiac resynchronisation therapy-defibrillator (CRT-D) is a combined device that provides both ICD protection against life-threatening arrhythmias and biventricular pacing to resynchronise the heart's contractions in patients with heart failure and electrical dyssynchrony.In some patients with heart failure and a reduced ejection fraction, the left and right ventricles do not contract in a coordinated way, most commonly because of a left bundle branch block (LBBB) on the ECG. This(...)
• CRT-DA cardiac resynchronisation therapy-defibrillator (CRT-D) is a combined device that provides both ICD protection against life-threatening arrhythmias and biventricular pacing to resynchronise the heart's contractions in patients with heart failure and electrical dyssynchrony.In some patients with heart failure and a reduced ejection fraction, the left and right ventricles do not contract in a coordinated way, most commonly because of a left bundle branch block (LBBB) on the ECG. This(...)
• Cardiac Resynchronization Therapy-Pacemaker A device that sends small electrical impulses to both lower chambers of the heart to resynchronize the ventricles.
• CRT-PA device that sends small electrical impulses to both lower chambers of the heart to resynchronize the ventricles.
• Cardiac TamponadeCardiac tamponade is a life-threatening emergency in which fluid accumulates within the pericardial sac (the membrane surrounding the heart) under sufficient pressure to compress the heart chambers and prevent them from filling normally. The pericardium is a relatively inelastic sac; once it contains enough fluid, even small additional volumes cause a steep rise in intrapericardial pressure, compressing the thin-walled atria and right ventricle and severely reducing cardiac output.Fluid(...)
• Cardiogenic ShockCardiogenic shock is a life-threatening condition in which the heart is unable to pump enough blood to meet the body's needs, causing a critical fall in blood pressure and inadequate oxygen delivery to vital organs. It is the most severe form of cardiac failure and a recognised complication following cardiac arrest, large heart attacks, and severe cardiomyopathy. How it differs from cardiac arrest Cardiac arrest is the sudden cessation of effective heart pumping, resulting in no pulse and(...)
• CardiologistA doctor who specializes in the study of the heart and its function in health and disease.
• CardiologyThe study of the heart and its function in health and disease.
• CardiomegalyCardiomegaly is the term for an enlarged heart. Rather than being a diagnosis in itself, it is a sign of an underlying cardiac or systemic condition. Cardiomegaly is typically identified on a chest X-ray, where the cardiac silhouette is wider than normal relative to the width of the chest (cardiothoracic ratio above 0.5), or on echocardiography, which can characterise the chambers more precisely.Common causes include: dilated cardiomyopathy, in which the left ventricle is enlarged and(...)
• CardiomyopathyA disease of the heart muscle that leads to generalized deterioration of the muscle and its pumping ability.
• CardiomyopexyCardiomyopexy is a historical cardiac surgical procedure in which a skeletal muscle (typically the pectoralis major) was surgically detached from its normal attachment and sutured directly onto the cardiac muscle, with the aim of improving blood supply to the heart by encouraging new blood vessels to grow from the skeletal muscle into the myocardium.The procedure was developed in the era before coronary artery bypass grafting became available, as a means of treating angina and heart(...)
• CardiomyoplastyReinforcement of cardiac muscle contractility by transfer of lattismus dorsi to surround the heart and to contract synchronously with cardiac muscle
• CardioplegiaTechnique in which the heart is stopped by injecting it with a solution of salts, by hypothermia, or by an electrical stimulus, this helps with complex cardiac surgery and transplants to be performed safely
• Cardiopulmonary BypassCardiopulmonary bypass (CPB) is the technique used in most open heart surgery to temporarily take over the functions of the heart and lungs, allowing surgeons to operate on a still, bloodless heart. The patient is connected to a heart-lung bypass machine, which draws blood from the venous system (usually through a large cannula in the right atrium), passes it through an oxygenator (which adds oxygen and removes carbon dioxide), and returns it to the arterial system (usually via the aorta).(...)
• Cardiopulmonary ResuscitationAn emergency measure that can maintain a person’s breathing and heartbeat. The person who performs CPR actually helps the patient’s circulatory system by breathing into the patient’s mouth to give them oxygen and by giving chest compressions to circulate the patient’s blood. Hands-only CPR involves only chest compressions
• CPRAn emergency measure that can maintain a person’s breathing and heartbeat. The person who performs CPR actually helps the patient’s circulatory system by breathing into the patient’s mouth to give them oxygen and by giving chest compressions to circulate the patient’s blood. Hands-only CPR involves only chest compressions
• Cardiopulmonary resuscitation–induced consciousness It has been hypothesized that owing to a variety of physiologic variables, such as autoregulation, comorbidities, and cerebral ischemic thresholds, it is possible for patients receiving high-quality cardiopulmonary resuscitation (CPR) to maintain consciousness
• CPRIC It has been hypothesized that owing to a variety of physiologic variables, such as autoregulation, comorbidities, and cerebral ischemic thresholds, it is possible for patients receiving high-quality cardiopulmonary resuscitation (CPR) to maintain consciousness
• CardiovascularCardiovascular is an adjective combining 'cardio' (from the Greek kardia, meaning heart) and 'vascular' (from the Latin vascularis, meaning vessel). It describes anything pertaining to the heart and the network of blood vessels (arteries, veins, and capillaries) that together make up the circulatory system.The cardiovascular system works as a closed circuit: the heart pumps blood through the arteries to deliver oxygen and nutrients to the body's tissues, and deoxygenated blood returns to(...)
• CVCardiovascular is an adjective combining 'cardio' (from the Greek kardia, meaning heart) and 'vascular' (from the Latin vascularis, meaning vessel). It describes anything pertaining to the heart and the network of blood vessels (arteries, veins, and capillaries) that together make up the circulatory system.The cardiovascular system works as a closed circuit: the heart pumps blood through the arteries to deliver oxygen and nutrients to the body's tissues, and deoxygenated blood returns to(...)
• Cardiovascular DiseaseA general term referring to conditions affecting the heart (cardio) and blood vessels (vascular system). May also simply be called heart disease. Examples include coronary artery disease, valve disease, arrhythmia, peripheral vascular disease, congenital heart defects, hypertension, and cardiomyopathy. Refer to specific conditions for detailed explanations.
• CVDA general term referring to conditions affecting the heart (cardio) and blood vessels (vascular system). May also simply be called heart disease. Examples include coronary artery disease, valve disease, arrhythmia, peripheral vascular disease, congenital heart defects, hypertension, and cardiomyopathy. Refer to specific conditions for detailed explanations.
• Cardiovascular SystemDescribes the heart and all the blood vessels in the body.
• CardioversionA technique of applying an electrical shock to the chest to convert an abnormal heartbeat to a normal rhythm.
• CardioverterA cardioverter is a device that delivers a controlled electrical shock to the heart to restore a normal heart rhythm. The term is closely related to defibrillator, but cardioversion specifically refers to a synchronised shock (timed to coincide with the heart's own electrical cycle) used to treat arrhythmias such as atrial fibrillation or ventricular tachycardia, whereas defibrillation uses an unsynchronised shock to treat the chaotic rhythm of ventricular fibrillation.Cardioversion can(...)
• Caregiver BurnoutCaregiver burnout is a state of physical, emotional, and mental exhaustion that can develop in people who provide significant care and support to a loved one with a serious illness or disability over an extended period. Partners, parents, and other family members of cardiac arrest survivors frequently take on substantial caring responsibilities, often without adequate support for themselves. Why it is common after cardiac arrest Cardiac arrest affects the whole family system, not just the(...)
• Carotid ArteryA major artery (right and left) in the neck supplying blood to the brain
• Catecholaminergic Polymorphic Ventricular TachycardiaCatecholaminergic polymorphic ventricular tachycardia (CPVT) is a rare inherited heart rhythm disorder in which dangerous arrhythmias are triggered specifically by physical exertion or emotional stress. Unlike most arrhythmia conditions where problems arise at rest, CPVT is characterised by ventricular arrhythmias that appear only when catecholamines (adrenaline and related stress hormones) are released during exercise or excitement.CPVT is most commonly caused by mutations in the(...)
• CPVTCatecholaminergic polymorphic ventricular tachycardia (CPVT) is a rare inherited heart rhythm disorder in which dangerous arrhythmias are triggered specifically by physical exertion or emotional stress. Unlike most arrhythmia conditions where problems arise at rest, CPVT is characterised by ventricular arrhythmias that appear only when catecholamines (adrenaline and related stress hormones) are released during exercise or excitement.CPVT is most commonly caused by mutations in the(...)
• Catecholaminergic Polymorphic Ventricular TachycardiaA rare inherited arrhythmia syndrome in which the heart's structure is normal but certain triggers — particularly physical exertion or emotional stress — can provoke dangerous ventricular arrhythmias, including polymorphic ventricular tachycardia. CPVT is caused by mutations affecting calcium regulation within heart cells, most commonly in the RYR2 gene. It typically presents in childhood or adolescence and can cause sudden cardiac arrest. Treatment includes beta-blockers, lifestyle(...)
• CPVTA rare inherited arrhythmia syndrome in which the heart's structure is normal but certain triggers — particularly physical exertion or emotional stress — can provoke dangerous ventricular arrhythmias, including polymorphic ventricular tachycardia. CPVT is caused by mutations affecting calcium regulation within heart cells, most commonly in the RYR2 gene. It typically presents in childhood or adolescence and can cause sudden cardiac arrest. Treatment includes beta-blockers, lifestyle(...)
• CatheterA catheter is a thin, hollow, flexible tube that can be inserted into a body cavity, duct, or blood vessel to allow passage of fluids, deliver medications, drain secretions, or perform measurements. Catheters are among the most widely used devices in modern medicine and appear across virtually every clinical specialty.In cardiovascular medicine, the term catheter most commonly refers to cardiac catheters used during cardiac catheterisation procedures. A thin catheter is passed through a(...)
• Catheter Ablation TherapyA procedure used to correct certain types of abnormal heart rhythms.
• Catheter (Cardiac)A 'tube' used to perform heart tests, by introducing it through an artery or vein into the heart (Catheter Tests)
• Urinary CatheterA urinary catheter is a thin, flexible tube inserted through the urethra into the bladder to drain urine continuously. It is connected to a sealed collection bag, allowing accurate measurement of urine output without the patient needing to use a toilet. A balloon at the tip, inflated with sterile water after insertion, holds the catheter in place within the bladder. This type is called a Foley catheter and is the most commonly used in hospital settings.In critical care following cardiac(...)
• CatheterisationThe process of inserting a catheter into a vein or artery and guiding it through the heart chambers and surrounding vessels for purposes of examination or treatment.
• CathlabA cath lab is where tests and procedures including ablation, angiogram, angioplasty and implantation of pacemakers/ICDs are carried out
• CentralCentral venous access refers to the placement of a catheter with its tip positioned in one of the large veins close to the heart, known as central veins. These include the superior vena cava, inferior vena cava, and right atrium. This is distinct from a peripheral intravenous line, which is placed in a smaller vein in the arm or hand.A central line (central venous catheter, CVC) provides reliable, long-term access for administering medications that would damage smaller peripheral veins,(...)
• Central LineA line is inserted into the patient in order for liquids/drugs to be passed into their veins.
• CerebellumArea at the back of the brain, below the cerebral hemispheres, involved in the control of movement, co-ordination, posture and balance.
• CerebralConcerning the brain.
• Cerebral angiogramAn X-ray picture of the blood vessels inside the head. A drug is injected via the groin artery to outline these cerebral vessels.
• Cerebral anoxiaA complete interruption of the supply of oxygen to the brain.
• Cerebral EmbolismA blood clot formed in one part of the body and then carried by the bloodstream to the brain, where it blocks an artery
• Cerebral HaemorrhageCerebral haemorrhage is bleeding within or around the brain resulting from rupture of a blood vessel. It is a form of stroke (specifically a haemorrhagic stroke) and is a serious medical emergency. There are two main types: intracerebral haemorrhage, in which bleeding occurs directly within the brain tissue, and subarachnoid haemorrhage, in which bleeding occurs in the space between the brain and the surrounding membranes (subarachnoid space), usually from a ruptured aneurysm.Causes(...)
• Cerebral hypoxiaA partial interruption of the supply of oxygen to the brain, which becomes inadequate to maintain normal brain function.
• Cerebral ischaemiaA deficiency of blood supply to brain tissue, due to an interruption or reduction of arterial blood flow.
• Cerebral ThrombosisFormation of a blood clot in an artery that supplies part of the brain
• Cerebro-spinal fluidLiquid which fills the ventricles of the brain and surrounds the brain and spinal cord.
• CerebrovascularCerebrovascular refers to the blood vessels of the brain and the blood supply to brain tissue. The term appears in several important medical conditions, including cerebrovascular accident (CVA, the clinical term for stroke), cerebrovascular disease (disease affecting the arteries supplying the brain), and cerebrovascular autoregulation (the brain's ability to maintain a constant blood supply despite changes in systemic blood pressure).The brain receives its blood supply from four main(...)
• Cerebrovascular AccidentA cerebrovascular accident (CVA), more commonly called a stroke, occurs when the blood supply to part of the brain is suddenly cut off or significantly reduced, causing brain cells to die from lack of oxygen. There are two main types: ischaemic stroke (caused by a clot blocking a blood vessel, accounting for around 85% of cases) and haemorrhagic stroke (caused by a blood vessel rupturing and bleeding into the brain).Strokes are relevant to cardiac arrest in several ways. Hypoxic brain(...)
• Cerebrovascular OcclusionThe blocking or closing of a blood vessel in the brain
• CerebrumThe cerebrum is the largest and most complex part of the human brain, occupying most of the skull cavity. It is divided into two hemispheres (left and right) connected by a thick bundle of nerve fibres called the corpus callosum. Each hemisphere is further divided into four lobes: the frontal lobe (reasoning, planning, personality, voluntary movement), the parietal lobe (sensory processing, spatial awareness), the temporal lobe (memory, language, hearing) and the occipital lobe (vision).(...)
• Chain of SurvivalA framework describing the sequence of actions that, when performed quickly and effectively, give a person the best chance of surviving an out-of-hospital cardiac arrest. The chain has four links: (1) Early recognition and call for help — recognising cardiac arrest and calling 999; (2) Early CPR — bystander cardiopulmonary resuscitation to maintain circulation; (3) Early defibrillation — use of an AED or defibrillator to restore a normal rhythm; (4) Early advanced care — handover to(...)
• ChannelopathyAn umbrella term for a group of inherited heart conditions in which the heart's electrical channels — the proteins that control the flow of ions in and out of heart muscle cells — do not function correctly, despite the heart having a normal structure. Channelopathies can predispose individuals to life-threatening arrhythmias and sudden cardiac arrest. Examples include Long QT Syndrome, Short QT Syndrome, Brugada Syndrome, and Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT).(...)
• ChaplaincyHospital chaplains provide spiritual, pastoral, and emotional support to patients, families, and staff, regardless of faith or belief — including those with no religious belief at all. Chaplaincy is available in most NHS hospitals and is free to access. During a critical illness or bereavement, a chaplain can offer a quiet, non-judgmental presence, help with practical matters such as contacting a faith leader, or simply sit with a family member who needs someone to talk to. Co-survivors(...)
• Children of Cardiac Arrest SurvivorsChildren of cardiac arrest survivors face their own significant emotional and psychological challenges following a parent's sudden cardiac arrest. The experience of seeing or being told that a parent nearly died, combined with the disruption to family life and uncertainty about the future, can have a lasting impact on children of all ages. Common responses in children include anxiety (particularly separation anxiety and worry that the parent may die again), sleep difficulties, changes in(...)
• CholesterolCholesterol is a waxy, fat-like substance found in every cell of the body. It has essential functions: it is a component of cell membranes, helps produce vitamin D, bile acids (for digestion), and hormones including oestrogen and testosterone. The body makes cholesterol in the liver, and additional cholesterol is absorbed from food.Cholesterol is transported in the blood by lipoproteins, which are particles made of fat and protein. The two most clinically important types are low-density(...)
• Cholesterol Lowering DrugCholesterol-lowering drugs are medications that reduce the level of cholesterol in the blood, primarily by lowering low-density lipoprotein (LDL) cholesterol ('bad cholesterol'), which is the main driver of atherosclerotic plaque formation in artery walls. Reducing LDL cholesterol is one of the most evidence-based interventions for preventing heart attack, stroke, and sudden cardiac arrest.Statins are the most important and widely used class of cholesterol-lowering drug. They work by(...)
• ChoreaBrief, involuntary jerky movements involving the limbs and face, seen in a number of brain disorders and following brain injury.
• Chronic Obstructive Pulmonary DiseaseRefers to a number of chronic lung disorders that obstruct airflow. The most common form of COPD is a combination of chronic bronchitis and emphysema.
• COPDRefers to a number of chronic lung disorders that obstruct airflow. The most common form of COPD is a combination of chronic bronchitis and emphysema.
• Chronotropic IncompetenceThe inability of the heart to increase its rate appropriately in response to increased activity or metabolic need, e.g., exercise, illness, etc.
• CineangiographyCineangiography (also written cine-angiography or cineventriculography) is a diagnostic imaging technique in which a radiocontrast dye is injected into the blood vessels or heart chambers while X-ray images are recorded as a continuous moving picture. The resulting moving image allows doctors to observe the flow of contrast through the cardiac chambers and coronary arteries in real time, visualising both anatomy and movement.In cardiac medicine, cineangiography is performed during(...)
• Circulatory SystemThe circulatory system (also called the cardiovascular system) is the organ system that circulates blood throughout the body, delivering oxygen and nutrients to tissues and removing waste products including carbon dioxide. It consists of the heart (the pump), the blood vessels (arteries, veins, and capillaries), and the blood itself.The circulatory system has two interconnected circuits. The systemic circulation carries oxygenated blood from the left heart via the aorta and arteries to(...)
• ClaudicationA tiredness or pain in the arms and legs caused by an inadequate supply of oxygen to the muscles, usually due to narrowed arteries or peripheral arterial disease (PAD).
• Clinical Nurse SpecialistA registered nurse with specialist training and expertise in a particular clinical area — for example, cardiac nursing, heart failure, arrhythmia management, or ICD and device management. For patients with ICDs and other cardiac devices, the CNS (sometimes called an arrhythmia nurse specialist or cardiac device nurse) is often the most accessible and knowledgeable member of the team for day-to-day questions about the device, clinic appointments, and post-implant recovery. CNSs typically(...)
• CNSA registered nurse with specialist training and expertise in a particular clinical area — for example, cardiac nursing, heart failure, arrhythmia management, or ICD and device management. For patients with ICDs and other cardiac devices, the CNS (sometimes called an arrhythmia nurse specialist or cardiac device nurse) is often the most accessible and knowledgeable member of the team for day-to-day questions about the device, clinic appointments, and post-implant recovery. CNSs typically(...)
• Clinical PsychologistA clinical psychologist is a doctoral-level healthcare professional trained to assess and treat a wide range of psychological difficulties. In the UK, clinical psychologists must be registered with the Health and Care Professions Council (HCPC) and typically hold a Doctorate in Clinical Psychology (DClinPsy) following a psychology undergraduate degree and extensive supervised clinical experience.Clinical psychologists work across the lifespan and within a range of settings including NHS(...)
• ClopidogrelMedication used to prevent clots from forming in the blood vessels
• Closed head injuryDamage to the brain where there is no penetration from the scalp or skull through to brain tissue. Often there is no injury to scalp or skull.
• Closed Heart SurgeryClosed heart surgery refers to cardiac surgical procedures that can be performed without opening the heart chambers and without the need for cardiopulmonary bypass (heart-lung bypass). The surgeon operates on the exterior of the heart or great vessels while the heart continues to beat normally, without stopping it or entering its interior.The term 'closed heart' is used to distinguish these procedures from open heart operations, where the heart is stopped and entered using bypass(...)
• Clot-BusterA drug used to dissolve a clot in an emergency,for example during a heart attack or stroke. This is called thrombolytic therapy.
• ClubbingFinger clubbing (digital clubbing) is a clinical sign in which the fingertips and toenails become abnormally curved, with thickening of the tissue beneath the nail, giving a characteristic bulbous shape to the fingertips. The angle between the nail and the nail fold (Lovibond's angle) exceeds 180 degrees. Clubbing develops over months to years and is associated with a range of underlying diseases.In cardiovascular medicine, clubbing is classically associated with cyanotic congenital(...)
• Co-survivorA family member, friend, or partner who was present at, or closely affected by, a cardiac arrest. Co-survivors often experience significant psychological impact — including anxiety, post-traumatic stress, depression, and hypervigilance — that is distinct from but interconnected with the survivor's own recovery. The trauma of witnessing a cardiac arrest, performing CPR on a loved one, or believing they might die can be profound and long-lasting. Co-survivors frequently report that their(...)
• CoarctationCoarctation is a narrowing (stenosis) of an artery, most commonly referring to coarctation of the aorta: a localised narrowing of the aorta, typically just beyond where the subclavian artery branches off to supply the left arm. This narrowing restricts blood flow to the lower body and forces the heart to pump much harder to maintain adequate circulation.Coarctation of the aorta is a congenital heart defect and one of the more common congenital cardiac conditions, accounting for(...)
• Coarctation of the AortaA congenital heart defect that results in narrowing of the aorta.
• CognitionGeneral term used to cover all areas of intellectual functioning. Includes skills such as thinking, remembering, planning, understanding, concentrating and using language.
• Cognitive Behavioural TherapyCognitive behavioural therapy (CBT) is a structured, evidence-based talking therapy that helps people identify and change unhelpful patterns of thinking and behaviour that are maintaining psychological difficulties. It is one of the most widely researched and effective psychological treatments available, and is recommended by NICE for anxiety, depression, PTSD, and many other conditions commonly experienced by cardiac arrest survivors. How CBT works CBT is based on the principle that how(...)
• Cognitive Impairment (post-cardiac arrest)Difficulties with memory, attention, concentration, processing speed, executive function, or other aspects of thinking, resulting from injury or illness affecting the brain. Following cardiac arrest, cognitive impairment is common and is caused primarily by hypoxic-ischaemic brain injury — the period during which the brain was deprived of oxygen. The degree of impairment varies enormously between individuals and depends on factors including the duration of the arrest, how quickly CPR and(...)
• Cognitive RehabilitationCognitive rehabilitation is a structured, goal-oriented therapeutic process designed to help people improve or compensate for difficulties in cognitive functions such as memory, attention, executive function, and processing speed, following brain injury or neurological illness. For cardiac arrest survivors with hypoxic brain injury, cognitive rehabilitation can play an important role in supporting recovery and improving daily functioning. Two main approaches Cognitive rehabilitation uses(...)
• Collateral CirculationBlood flow through small, nearby vessels in response to blockage of a main blood vessel.
• Collateral VesselsNew blood vessels created by the body to try and restore blood flow to an area when the blood vessel(s) that are already there are too small, narrowed, or blocked.
• CollateralsCollateral vessels are alternative blood vessel pathways that carry blood around a blockage or an area of abnormal development. When a normal artery or vein is obstructed, narrowed, or absent, blood is redirected through smaller, pre-existing vessels that gradually enlarge and remodel over time to compensate. This process, known as collateralisation, is the body's natural response to chronic ischaemia (reduced blood flow).In the heart, coronary collateral vessels develop in response to(...)
• ComaA state of deep and often prolonged unconsciousness.
• CommissurotomyA commissurotomy is a procedure used to widen the opening of a heart valve that has become narrowed (stenotic) due to fusion of the valve leaflets along their natural joining points (commissures). The commissures are the points where adjacent valve leaflets meet at the edges of the valve orifice; in conditions such as rheumatic mitral stenosis, these edges fuse together, reducing the effective valve opening.Commissurotomy separates the fused leaflets to widen the valve opening and(...)
• Commotio CordisCommotio cordis (Latin for "agitation of the heart") is a rare cause of sudden cardiac arrest triggered by a blunt, non-penetrating impact to the chest during a critically vulnerable window in the cardiac cycle. The impact itself does not cause structural damage to the heart or chest; it is the precise timing of the blow that triggers ventricular fibrillation. How it happens During each heartbeat, there is an extremely brief period (approximately 10 to 30 milliseconds, just before the peak(...)
• Community First ResponderA volunteer, often with first aid or emergency medical training, who is dispatched by the ambulance service to respond to cardiac arrests and other life-threatening emergencies in their local community — typically arriving before the ambulance. Community first responders are registered with and supported by their local NHS ambulance trust. They carry a defibrillator and are trained in CPR. Their presence in rural and semi-rural areas, where ambulance response times may be longer, can be(...)
• CFRA volunteer, often with first aid or emergency medical training, who is dispatched by the ambulance service to respond to cardiac arrests and other life-threatening emergencies in their local community — typically arriving before the ambulance. Community first responders are registered with and supported by their local NHS ambulance trust. They carry a defibrillator and are trained in CPR. Their presence in rural and semi-rural areas, where ambulance response times may be longer, can be(...)
• Computed TomographyComputed tomography (CT) is a medical imaging technique that uses X-rays and a computer to produce detailed cross-sectional images of the body's internal structures. Unlike a conventional X-ray, which produces a flat two-dimensional image, CT captures multiple X-ray measurements from different angles as the scanner rotates around the patient, and the computer reconstructs these into detailed three-dimensional images that can be viewed in any plane.In cardiac and emergency medicine, CT is(...)
• CTComputed tomography (CT) is a medical imaging technique that uses X-rays and a computer to produce detailed cross-sectional images of the body's internal structures. Unlike a conventional X-ray, which produces a flat two-dimensional image, CT captures multiple X-ray measurements from different angles as the scanner rotates around the patient, and the computer reconstructs these into detailed three-dimensional images that can be viewed in any plane.In cardiac and emergency medicine, CT is(...)
• ConcussionA mild traumatic brain injury caused by a blow or jolt to the head. Contrary to common belief, loss of consciousness is not required for a concussion diagnosis — most concussions do not involve passing out. Symptoms may include headache, confusion, dizziness, memory problems, and sensitivity to light or noise. Concussion can occur following cardiac arrest due to a fall at the time of collapse.
• Conducting TissueThe conducting tissue of the heart is a specialised network of cells that generate and transmit the electrical impulses that coordinate each heartbeat. Unlike ordinary heart muscle cells, conducting cells are not primarily contractile; their function is to conduct electricity rapidly and reliably to ensure that the chambers of the heart contract in the correct sequence.The main components of the cardiac conduction system are: the sinoatrial (SA) node (the heart's natural pacemaker,(...)
• Conduction SystemSpecial muscle fibers that conduct electrical impulses throughout the heart muscle
• ConduitA conduit in cardiac surgery is a tube or vessel used to create a new pathway connecting one part of the cardiovascular system to another, typically to bypass an obstruction, replace a damaged structure, or reconstruct an abnormal anatomy. Conduits can be biological (such as a segment of the patient's own vein or artery, or a preserved donor vessel called a homograft) or synthetic (such as polyester or PTFE fabric tubing).Conduits are widely used in congenital heart surgery, where(...)
• ConfabulationVerbalisations about people, places or events with no basis in reality.
• CongenitalCongenital is a medical adjective meaning 'present at birth' or 'existing at the time of birth'. It applies to conditions, abnormalities, or traits that a person is born with, regardless of whether they were caused by genetic factors, environmental influences during fetal development, or a combination. The term does not imply hereditary transmission, as some congenital conditions arise from new (de novo) mutations or environmental exposures during pregnancy.In cardiology, congenital(...)
• Congenital Heart DefectsCongenital heart defects (CHD) is a general term for structural abnormalities of the heart or its major blood vessels that are present at birth. The terms 'congenital heart defects' and 'congenital heart disease' are used interchangeably in clinical practice.CHD encompasses a wide spectrum of abnormalities, from simple defects that require no treatment (such as small ventricular septal defects that often close spontaneously in childhood) to complex and life-threatening conditions(...)
• CHDCongenital heart defects (CHD) is a general term for structural abnormalities of the heart or its major blood vessels that are present at birth. The terms 'congenital heart defects' and 'congenital heart disease' are used interchangeably in clinical practice.CHD encompasses a wide spectrum of abnormalities, from simple defects that require no treatment (such as small ventricular septal defects that often close spontaneously in childhood) to complex and life-threatening conditions(...)
• Congenital Heart DiseaseCongenital heart disease (CHD) is an umbrella term for structural abnormalities of the heart or major blood vessels that are present from birth. The defects form during fetal development and range from simple conditions that require no treatment to complex abnormalities that need surgery in infancy and lifelong specialist follow-up. CHD is the most common type of birth defect, affecting around 1 in 100 babies born in the UK.Common types of congenital heart defect include holes in the(...)
• Congenitally Corrected Transposition of the Great ArteriesIn this complex malformation, the ventricles are on the opposite side of the heart to usual. The atria are connected to the incorrect ventricles and the great arteries also come from the wrong ventricles (transposition). Despite these problems, blood from the lungs passes to the aorta, so the child is not cyanosed. Other heart defects are commonly present (e.g. VSD, valve abnormalities, coarctation, pulmonary stenosis).
• Congestive Heart FailureCongestive heart failure (CHF) is a term for heart failure in which the body's fluid regulation is overwhelmed, causing fluid (congestion) to build up in the tissues. In the lungs, this congestion causes breathlessness and, in severe cases, pulmonary oedema. In the body's periphery, it causes swelling of the ankles and legs (peripheral oedema) and, in advanced cases, ascites (fluid in the abdomen) and an enlarged liver due to venous congestion.The term congestive heart failure describes(...)
• Conscious Having an awareness of one’s environment and one’s own existence, sensations, and thoughts
• Consciousness The state of being conscious; awareness
• Consultant PsychiatristA Consultant Psychiatrist is a trained mental health doctor with additional specialist training in psychiatry. The consultant is medically responsible for the care of people receiving mental health services and also supervises junior doctors
• Continuous Positive Airways PressureAn air pressure in the range 5-30cm. It can be applied to ghe upper airways using a full face mask or a nasal mask only (nCPAP). It is used in HDU's to optimize oxygen delivery to pateints who are being weaned from ventilators and on patients at home with obstructive sleep apnoea.
• CPAPAn air pressure in the range 5-30cm. It can be applied to ghe upper airways using a full face mask or a nasal mask only (nCPAP). It is used in HDU's to optimize oxygen delivery to pateints who are being weaned from ventilators and on patients at home with obstructive sleep apnoea.
• ContracoupBruising of the brain tissue in the side opposite to where the blow was struck.
• ContractionCardiac contraction is the process by which the heart muscle (myocardium) generates force to squeeze blood out of the chambers and into the circulation. It is triggered by an electrical impulse from the heart's conduction system, which causes a rapid change in the electrical charge across the surface of each muscle cell (the action potential). This triggers the release of calcium ions inside the cell, which bind to proteins in the contractile machinery and cause the muscle fibres to slide(...)
• ContracturesJoints and muscles which are not used regularly quickly becoming stiff, and rendering them resistant to stretching.
• ContraindicationA situation in which medication should not be used. For example because of a physical condition, other medications, pregnancy
• Convulsion A violent involuntary contraction of a muscle or muscles.
• Coronary AngiographyCoronary angiography is the gold standard diagnostic investigation for coronary artery disease, providing direct visualisation of the coronary arteries and the degree and location of any narrowings or blockages. It is performed by injecting a radiocontrast dye into the coronary arteries via a catheter, while X-ray imaging (fluoroscopy) captures the dye outlining the arterial lumen in real time.The procedure is performed in a cardiac catheterisation laboratory. A thin catheter is inserted(...)
• Coronary AngioplastyCoronary angioplasty is a procedure used to open a narrowed or blocked coronary artery by inflating a small balloon at the site of the obstruction, compressing the plaque against the artery wall and widening the channel for blood flow. It is performed during cardiac catheterisation: a thin catheter is inserted into a peripheral artery (usually the radial artery at the wrist) and guided under X-ray imaging to the affected coronary artery.Once in position at the narrowed segment, a(...)
• Coronary ArteriesThe coronary arteries are the blood vessels that supply oxygenated blood to the heart muscle (myocardium) itself. Despite being the body's most powerful pump, the heart cannot use the blood flowing through its chambers directly; it relies on its own dedicated arterial supply. There are two main coronary arteries, both arising from the base of the aorta just above the aortic valve.The left coronary artery (LCA) divides shortly after its origin into the left anterior descending (LAD)(...)
• Coronary Artery AnomalyA coronary artery anomaly (CAA) is a congenital defect in which one or more of the coronary arteries has an abnormal origin, course, or structure. The anomaly is present from birth and arises during fetal cardiac development, when the coronary arteries fail to form in the usual pattern.Coronary artery anomalies vary widely in their clinical significance. Many are benign variants discovered incidentally on imaging and require no treatment. However, certain types carry a risk of sudden(...)
• CAAA coronary artery anomaly (CAA) is a congenital defect in which one or more of the coronary arteries has an abnormal origin, course, or structure. The anomaly is present from birth and arises during fetal cardiac development, when the coronary arteries fail to form in the usual pattern.Coronary artery anomalies vary widely in their clinical significance. Many are benign variants discovered incidentally on imaging and require no treatment. However, certain types carry a risk of sudden(...)
• Coronary Artery Bypass GraftCoronary artery bypass graft (CABG) surgery restores blood flow to the heart muscle by routing blood around a blocked or narrowed coronary artery. During the procedure, a surgeon takes a healthy blood vessel from elsewhere in the body (typically the internal mammary artery from the chest wall, or a vein from the leg) and uses it to create a detour around the diseased section.CABG is most commonly performed to treat severe coronary artery disease (CAD) when arteries are too blocked for(...)
• CABGCoronary artery bypass graft (CABG) surgery restores blood flow to the heart muscle by routing blood around a blocked or narrowed coronary artery. During the procedure, a surgeon takes a healthy blood vessel from elsewhere in the body (typically the internal mammary artery from the chest wall, or a vein from the leg) and uses it to create a detour around the diseased section.CABG is most commonly performed to treat severe coronary artery disease (CAD) when arteries are too blocked for(...)
• Coronary Artery DiseaseCoronary artery disease (CAD) is the narrowing or blockage of the coronary arteries, the blood vessels that supply oxygenated blood to the heart muscle. It is the most common form of heart disease in adults and the leading cause of [sudden cardiac arrest](/glossary/sudden-cardiac-arrest/) in people over 40 in the UK.CAD develops through a process called atherosclerosis, in which fatty deposits (plaques) build up inside the artery walls over years and decades. These plaques contain(...)
• CADCoronary artery disease (CAD) is the narrowing or blockage of the coronary arteries, the blood vessels that supply oxygenated blood to the heart muscle. It is the most common form of heart disease in adults and the leading cause of [sudden cardiac arrest](/glossary/sudden-cardiac-arrest/) in people over 40 in the UK.CAD develops through a process called atherosclerosis, in which fatty deposits (plaques) build up inside the artery walls over years and decades. These plaques contain(...)
• Coronary Care UnitA specially equipped unit in a Hospital providing intensive care to patients of coronary artery disease, i.e. myocardial infarction, unstable angina, etc.
• CCUA specially equipped unit in a Hospital providing intensive care to patients of coronary artery disease, i.e. myocardial infarction, unstable angina, etc.
• Coronary Heart DiseaseCoronary heart disease (CHD) is the term commonly used in the UK for coronary artery disease (CAD): the narrowing and blockage of the coronary arteries due to the build-up of atherosclerotic plaque. The two terms are interchangeable in everyday clinical practice and public health contexts, though CAD is more commonly used in cardiology literature.CHD is the single biggest cause of death in the UK and a leading cause of sudden cardiac arrest, particularly in people over 40. The same(...)
• Coronary ObstructionA partial or complete obstruction (occlusion) of one of the coronary arteries, thereby hindering blood flow to the heart muscle. This can be due to thrombus, embolus, spasm or dissection.
• Coronary OcclusionAn obstruction of one of the coronary arteries that hinders blood flow to the heart muscle
• Coronary RevascularizationCoronary revascularisation refers to any procedure that restores blood flow to heart muscle deprived of oxygen due to narrowing or blockage of the coronary arteries. The aim is to relieve ischaemia, reduce symptoms such as angina, and in certain situations reduce the risk of heart attack and sudden cardiac arrest. Two main techniques are available: percutaneous coronary intervention (PCI) and coronary artery bypass graft (CABG) surgery.PCI is performed via a catheter inserted into an(...)
• Coronary SpasmA transient partial or complete obstruction (occlusion) of one of the coronary arteries, thereby hindering blood flow to the heart muscle. A rare clinical cause of angina.
• Coronary ThrombosisFormation of a clot in one of the arteries carrying blood to the heart muscle. Also called coronary occlusion
• Cortical blindnessLoss of visual function resulting from damage to the main visual areas, which are located in the occipital lobes at the back of the brain.
• CounsellingCounselling is a talking therapy that usually deals with a recent distressing event.The length of time that counselling is needed varies from person to person.
• Cardiopulmonary ResuscitationCardiopulmonary Resuscitation. An emergency procedure used when someone's heart has stopped (cardiac arrest) to maintain blood flow to the brain and vital organs until normal heart rhythm can be restored. CPR combines chest compressions — pressing hard and fast on the centre of the chest to manually pump the heart — with rescue breaths in trained responders, or chest compressions alone (hands-only CPR) in untrained bystanders. Current Resuscitation Council UK guidance recommends hands-only(...)
• CPRCardiopulmonary Resuscitation. An emergency procedure used when someone's heart has stopped (cardiac arrest) to maintain blood flow to the brain and vital organs until normal heart rhythm can be restored. CPR combines chest compressions — pressing hard and fast on the centre of the chest to manually pump the heart — with rescue breaths in trained responders, or chest compressions alone (hands-only CPR) in untrained bystanders. Current Resuscitation Council UK guidance recommends hands-only(...)
• Cranial nervesThe cranial nerves are 12 pairs of nerves that arise directly from the brain and brainstem rather than from the spinal cord. Numbered I to XII, each pair has distinct functions: some are purely sensory, some purely motor, and some carry both types of fibres. They supply the head, face, neck and several internal organs, controlling functions including smell, vision, eye movement, facial sensation and movement, hearing, balance, swallowing, speech, taste, and regulation of the heart and(...)
• CraniotomySurgical removal of the skull in small pieces.
• Creatinine KinaseA Cardiac enzyme used to diagnose a heart attack.
• Critical Care TeamThe critical care team is the multidisciplinary group of health professionals responsible for the assessment and treatment of patients with life-threatening illness or injury. Critical care (also called intensive care) wards provide continuous monitoring and advanced organ support for patients who require more intervention than can be delivered on a general ward.The team is led by a critical care consultant (intensivist), a doctor with specialist training in managing complex, unstable(...)
• Cross MatchThe test to ensure that blood, for transfusion, is compatible with the patient and will not cause an unwanted reaction.
• CryoablationCryoablation is a technique used in cardiac electrophysiology in which extremely cold temperatures are applied to heart tissue to destroy it or create a precisely controlled scar. During catheter ablation procedures, cryoablation eliminates abnormal electrical circuits or triggers that cause arrhythmias by freezing the target tissue to temperatures below -40 to -70°C, disrupting cell structures and triggering cell death.Cryoablation has a particular advantage in cardiac(...)
• CulturesSamples of blood
• CyanosisBlueness of the skin caused by a lack of oxygen in the blood.
• Cyanotic Heart DiseaseCyanotic heart disease is a category of congenital heart defect in which a structural abnormality allows oxygen-poor (deoxygenated) blood to enter the systemic circulation without first passing through the lungs. The resulting low oxygen saturation causes cyanosis: a bluish discolouration of the skin, lips, and fingertips that becomes visible when blood oxygen levels fall significantly.In a normal heart, deoxygenated blood returning from the body passes entirely through the right heart(...)

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• DeathThe irreversible loss of the capacity for consciousness combined with the irreversible loss of the capacity to breathe. May be diagnosed on cardiovascular (heart) or neurological (brain) criteria.
• Death Rate (age-adjusted)An age-adjusted death rate (also called an age-standardised mortality rate) is a statistical measure used to compare mortality between different populations or across different time periods, after removing the distorting effect of differences in age distribution. Since older populations naturally have higher death rates than younger ones, comparing raw (crude) death rates between a young and an old population would not meaningfully reflect whether one group faces genuinely higher(...)
• Deep Vein ThrombosisA blood clot in a deep vein in the calf (DVT)
• DVTA blood clot in a deep vein in the calf (DVT)
• DefectA physical abnormality, e.g. of the position or structure of the heart or main blood vessels.
• DefibrillationDefibrillation is the delivery of a controlled electrical shock to the heart to terminate a life-threatening cardiac arrhythmia and restore the potential for a normal heart rhythm. It is the definitive treatment for ventricular fibrillation (VF) and pulseless ventricular tachycardia (VT), the heart rhythms responsible for the vast majority of sudden cardiac arrests.During VF, the heart's electrical activity is completely disorganised: millions of cells fire chaotically, causing the(...)
• Defibrillation ThresholdDefibrillation threshold (DFT) is the minimum energy level required to successfully terminate ventricular fibrillation (VF) with a defibrillation shock. In the context of implantable cardioverter defibrillators (ICDs), it refers to the amount of energy the device must be able to deliver to reliably convert VF back to a normal rhythm. Why it matters at ICD implantation When an ICD is implanted, the cardiologist needs to confirm that the device can deliver enough energy to terminate VF(...)
• Defibrillation Threshold TestingPerformed during ICD implantation, this is an assessment is to confirm appropriate sensing of ventricular fibrillation and to establish an adequate safety margin for defibrillation
• DFTPerformed during ICD implantation, this is an assessment is to confirm appropriate sensing of ventricular fibrillation and to establish an adequate safety margin for defibrillation
• DefibrillatorA defibrillator is a medical device that delivers a controlled electric shock to the heart to restore a normal cardiac rhythm in someone experiencing a life-threatening arrhythmia such as ventricular fibrillation (VF) or pulseless ventricular tachycardia (VT). These arrhythmias produce no effective pumping action; defibrillation is the only treatment that can terminate them. The shock depolarises all the heart's electrical cells simultaneously, giving the heart's natural pacemaker the(...)
• Defibrillator Shock ExperienceThe experience of receiving a defibrillator shock from an ICD is one that many survivors describe in vivid terms, yet it is rarely discussed openly before device implantation. Understanding what a shock feels like, and how to manage the psychological and practical aftermath, is an important part of living with an ICD. What a shock feels like The sensation varies between individuals but is most commonly described as a sudden, forceful blow or thump to the chest, a sensation of being kicked,(...)
• DeliriumDelirium is a name for acute confusion. It is sometimes described as like being in a nightmare, but it feels very real to patients. A patient with delirium is hallucinating, which means they can be seeing, hearing, or feeling things that don’t exist outside their mind. They can imagine they are in different situations, and these are often very frightening.
• DemyelinationLoss of the fatty insulating sheath (myelin) surrounding nerve axons, which impairs their function by interfering with their ability to conduct electrical nerve impulses normally.
• DendriteAre appendages that are designed to receive communications from other cells. They resemble a tree-like structure, forming projections that become stimulated by other neurons and conduct the electrochemical charge to the cell body (or, more rarely, directly to the axons)
• DepressionDepression is one of the most common forms of mental health problem and can occur to people of all ages. Symptoms include feelings of despair, hopelessness and worthlessness, an inability to cope, sleep problems and sometimes thoughts of suicide. Often people with depression will complain of physical problems (e.g for example headaches, stomach problems) rather than depression when consulting their GP. Various treatments are available for depression including antidepressant medication,(...)
• DepressionDepression is a common mental health condition characterised by persistent low mood, loss of interest or pleasure in activities (anhedonia), and a range of physical and psychological symptoms. These can include fatigue, changes in sleep and appetite, difficulty concentrating, feelings of worthlessness or guilt, and in severe cases, thoughts of self-harm or suicide. Depression is distinct from normal sadness: it is more intense, longer lasting (typically two weeks or more), and affects the(...)
• Device AdvisoryA formal notification issued by a device manufacturer when a potential safety issue is identified with a specific model of ICD, pacemaker, or leads. An advisory (sometimes called a safety alert or field safety corrective action) does not always mean the device needs to be replaced — many advisories result in a change to programming or increased monitoring. Patients affected are contacted by their device clinic, who will advise on any recommended action. If you are concerned about whether(...)
• Device InterrogationAlso called a device check or device follow-up. A routine clinic appointment (or remote session via home monitoring equipment) in which a clinician uses a programmer — a handheld device held over your chest — to wirelessly communicate with your ICD or pacemaker. The interrogation reads stored data including any arrhythmia episodes, shocks delivered, battery status, and lead performance. Most patients with an ICD have a formal in-person interrogation at least once a year, supplemented by(...)
• Device PocketThe small surgically created space beneath the skin — usually just below the collarbone — where the pulse generator of an ICD or pacemaker sits. The pocket is formed during the implant procedure and the device is secured within it. Pocket complications, though uncommon, can include infection, haematoma (blood collection), or the device eroding through the skin, all of which require prompt medical attention.
• DextrocardiaDextrocardia is a rare congenital condition in which the heart is positioned on the right side of the chest rather than the left. In the most common form (situs inversus with dextrocardia), all of the thoracic and abdominal organs are mirrored, with the liver on the left and the spleen on the right. This mirror-image arrangement can be associated with a structurally normal heart and normal life expectancy.However, dextrocardia can also occur in isolation, with the heart rotated to the(...)
• DiabetesA disease in which the body doesn’t produce or properly use insulin. Insulin is needed to convert sugar and starch into the energy used in daily life
• DiagnosisDiagnosis is the process of identifying a disease, condition, or injury based on a person's symptoms, clinical history, physical examination, and the results of investigations such as blood tests, imaging, or monitoring. A diagnosis gives a name and framework to what is happening in the body, which guides treatment decisions and provides a basis for discussing prognosis.In the context of cardiac arrest, the immediate priority after resuscitation is to identify the underlying cause. The(...)
• DiagnosticsIn the context of cardiac devices, diagnostics refers to the data stored and reported by an implantable cardioverter defibrillator (ICD) or pacemaker that records the patient's cardiac rhythm, device activity, and the delivery of any therapies. This stored information is reviewed at each device clinic appointment and via remote monitoring to evaluate how the heart has been behaving and whether the device is functioning as intended.Devices typically store: heart rate histograms (showing(...)
• DialysisCirculating a patient’s blood through a machine outside the body to remove toxins, waste products and excess salts from the blood whilst a patient’s own kidneys are unable to do so. Intensive care units commonly offer a gentler/slower version of standard outpatient-type dialysis that is better tolerated by critically ill patients. Maybe colloquially be referred to as ‘filtration’
• DiastoleThe time during which the ventricular heart muscle relaxes after each contraction, between each heart beat.
• Diastolic Blood PressureDiastolic blood pressure is the lower of the two numbers in a blood pressure reading (for example, the 80 in 120/80 mmHg). It represents the pressure in the arteries when the heart muscle is relaxing between beats (during diastole), before the next contraction. During this phase, the aortic and pulmonary valves are closed and the heart refills with blood.Diastolic blood pressure reflects the minimum pressure maintained in the arterial system by the elastic recoil of the large arteries(...)
• Diastolic DysfunctionDiastolic dysfunction refers to impaired relaxation and filling of the left ventricle during diastole (the phase between heartbeats). Instead of relaxing fully to accommodate incoming blood, the ventricle becomes stiff, raising filling pressures and causing blood to back up into the pulmonary circulation. The result is the symptoms of [heart failure](/glossary/heart-failure/) despite the heart continuing to pump a normal percentage of blood with each beat.Diastolic dysfunction underlies(...)
• DiencephalonThe midbrain. This contains discrete nerve centres including the hypothalamus, which controls appetite regulation, sexual arousal, thirst and temperature control, and some aspects of memory. The diencephalon also contains the thalamus, the body's sensory gateway to the brain.
• DietitianA health professional who can advise you on healthy eating and special diets.
• Diffuse axonal injuryWidespread tearing of nerve fibres across the whole of the brain.
• Diffuse brain injuryInjury to cells in many areas of the brain rather than in one specific location.
• DigitalisDigitalis is a class of medicines derived from the foxglove plant (Digitalis purpurea and Digitalis lanata) that have been used in medicine for over 200 years. The active compounds, primarily digoxin and digitoxin, have positive inotropic effects (strengthening the force of heart muscle contraction) and negative chronotropic effects (slowing the heart rate). The most commonly used preparation today is digoxin.Digitalis medicines act by inhibiting the sodium-potassium ATPase pump in heart(...)
• DigoxinDigoxin is a cardiac glycoside derived from the foxglove plant (see Digitalis). It strengthens the force of heart muscle contractions (positive inotropic effect) and slows the heart rate by reducing conduction through the atrioventricular (AV) node (negative chronotropic effect).In modern cardiology, digoxin is used primarily for rate control in atrial fibrillation, particularly in patients with concurrent heart failure with reduced ejection fraction where beta-blockers or calcium(...)
• Dilated CardiomyopathyDilated cardiomyopathy (DCM) is a disease of the heart muscle in which the left ventricle, and sometimes other chambers, becomes enlarged (dilated) and weakened, significantly reducing its ability to pump blood effectively. It is one of the most common causes of heart failure and a recognised cause of sudden cardiac arrest through ventricular arrhythmias.DCM can result from genetic variants, viral myocarditis, excessive alcohol consumption, certain medications or chemotherapy agents,(...)
• DiplopiaDouble vision
• Discharge PlanningDischarge planning is the structured process of preparing a patient to leave hospital safely, ensuring that their ongoing care, support, and monitoring needs are met after they go home. It begins early in the hospital admission and involves the patient, their family or carers, and the clinical team.For cardiac arrest survivors, discharge planning is particularly important because recovery extends well beyond the hospital stay. Survivors leaving intensive care may be physically(...)
• DiseaseDisease is a general medical term for any condition that impairs the normal functioning of part or all of the body, producing recognisable signs and symptoms. In clinical usage, it encompasses both congenital conditions (present from birth, due to genetic factors or developmental abnormalities) and acquired conditions (developing during a person's lifetime as a result of infection, injury, ageing, or lifestyle factors).In cardiovascular medicine, the term appears in compound forms(...)
• DisinhibitionDifficulty in controlling urges and impulses to speak, act or show emotions.
• Dispatcher-Assisted CPRDispatcher-assisted CPR (DA-CPR), also called telephone CPR or T-CPR, is the process by which an emergency call handler guides a bystander through performing CPR on a person in cardiac arrest while waiting for the ambulance to arrive. It is one of the most impactful interventions in improving out-of-hospital cardiac arrest survival rates. Why it makes a difference The first minutes after cardiac arrest are critical. For every minute without CPR and defibrillation, survival chances fall by(...)
• Dissecting AneurysmA dissecting aneurysm, more accurately called an aortic dissection, is a serious emergency in which a tear forms in the inner layer (intima) of the aortic wall, allowing blood to surge through the tear and split the layers of the aortic wall apart, creating a false channel (false lumen) running parallel to the true lumen. The pressure of blood flowing through this false channel can propagate the tear along the length of the aorta, sometimes extending into branches supplying the coronary(...)
• DissectionA condition in which the layers of an artery separate or are torn, causing blood to flow between the layers. Dissection most commonly occurs in the aorta and can cause sudden death.
• DissociationA disruption in the normal continuity of consciousness, memory, identity, or perception. Dissociation exists on a spectrum — from mild and common experiences such as daydreaming or briefly losing track of a conversation, through to more profound states in which a person feels detached from their body, experiences the world as unreal (derealisation), or feels detached from themselves as if watching from the outside (depersonalisation). Dissociation is a normal protective response to(...)
• DiureticA drug that lowers blood pressure by causing fluid loss. Diuretics promote urine production.
• Dizziness A sensation of whirling and a tendency to fall; giddy; vertiginous
• DizzinessDizziness is a broad term describing an unpleasant sensation that includes lightheadedness, a feeling of faintness or unsteadiness, and a spinning sensation (vertigo). In the context of cardiac arrest and heart conditions, dizziness is often significant because it can indicate a problem with the heart's ability to maintain adequate blood pressure and flow to the brain.For survivors of sudden cardiac arrest, dizziness may arise from several causes. Orthostatic hypotension, a drop in blood(...)
• Do Not Attempt Cardiopulmonary ResuscitationDo Not Attempt Cardiopulmonary Resuscitation. A clinical decision, made in advance, that CPR should not be attempted if a person's heart stops. A DNACPR order is not a withdrawal of all treatment — it applies only to CPR. It is usually made when CPR is considered unlikely to be successful, or when the burdens of attempted resuscitation outweigh the potential benefits, given the person's overall condition. The decision should ideally be made in discussion with the patient and, where(...)
• DNACPRDo Not Attempt Cardiopulmonary Resuscitation. A clinical decision, made in advance, that CPR should not be attempted if a person's heart stops. A DNACPR order is not a withdrawal of all treatment — it applies only to CPR. It is usually made when CPR is considered unlikely to be successful, or when the burdens of attempted resuscitation outweigh the potential benefits, given the person's overall condition. The decision should ideally be made in discussion with the patient and, where(...)
• Donor ValvesA heart valve (usually the aortic or pulmonary valve), taken from the heart of a child or adult soon after death, which can be kept sterile and frozen to preserve its structure. It can be used as a replacement for a defective or missing valve in a child or adult having heart surgery.
• Doppler UltrasoundDoppler ultrasound is a technology that uses the Doppler effect (the change in frequency of sound waves reflected from moving objects) to measure and visualise blood flow within the heart and blood vessels. It is an essential component of echocardiography (cardiac ultrasound) and vascular ultrasound studies.Whereas standard (B-mode) ultrasound produces still or moving images of anatomical structures, Doppler ultrasound detects the velocity and direction of blood flowing through those(...)
• Double Inlet Left VentricleA condition in which both atria are connected to the left ventricle. The right ventricle is usually very small.
• DILVA condition in which both atria are connected to the left ventricle. The right ventricle is usually very small.
• Double Outlet Right VentricleDouble outlet right ventricle (DORV) is a congenital heart defect in which both the aorta and the pulmonary artery arise from the right ventricle, rather than the normal arrangement where the aorta arises from the left ventricle. Because the left ventricle has no great artery to pump into directly, blood from the left ventricle can only exit through a ventricular septal defect (VSD) into the right ventricle and thence into the great arteries.DORV encompasses a spectrum of anatomy, and(...)
• DORVDouble outlet right ventricle (DORV) is a congenital heart defect in which both the aorta and the pulmonary artery arise from the right ventricle, rather than the normal arrangement where the aorta arises from the left ventricle. Because the left ventricle has no great artery to pump into directly, blood from the left ventricle can only exit through a ventricular septal defect (VSD) into the right ventricle and thence into the great arteries.DORV encompasses a spectrum of anatomy, and(...)
• Driving Restrictions (ICD)People with an ICD are subject to specific driving restrictions under DVLA guidelines in the UK. Following ICD implantation for the prevention of sudden cardiac arrest, patients are typically required to stop driving for at least 6 months. If the ICD delivers a shock (appropriate or inappropriate) that causes or could have caused incapacity, a further period of driving cessation applies. Different rules apply to Group 1 (car and motorcycle) and Group 2 (lorry and bus) licences — Group 2(...)
• Dual-Chamber PacemakerA dual-chamber pacemaker is a device with two leads: one placed in the right atrium and one in the right ventricle. This allows the pacemaker to sense and pace both chambers, coordinating their contractions to restore the normal sequence in which the atria beat just before the ventricles. This coordinated timing is called atrioventricular (AV) synchrony.Dual-chamber pacing is preferred over single-chamber (ventricular only) pacing in most people who need a permanent pacemaker, because it(...)
• DuctusThe blood vessel connecting the aorta with the pulmonary artery before birth. The full name is 'Ductus Arteriosus'. It usually closes within the early days or weeks after birth. If it remains open after this time it is called a Patent (or Persistent) Ductus Arteriosus (PDA).
• DuraOutermost of the three membranes protecting the brain and spinal cord.
• DyingThe end stage of every persons life, lasting often for several days before the actual death.
• DysarthriaDysarthria is a speech disorder caused by weakness, slowness, or incoordination of the muscles used for speaking. It results from damage to the brain or nervous system that controls these muscles, rather than from a problem with language understanding or word-finding (which would be aphasia).People with dysarthria may have slurred, slow, or imprecise speech that is difficult for others to understand. The voice may sound nasal, breathy, or monotone. In mild cases the problem is barely(...)
• DysphagiaDysphagia means difficulty swallowing. It is classified as oropharyngeal dysphagia (affecting the mouth and throat) or oesophageal dysphagia (affecting the oesophagus), with different underlying causes and treatments for each type. In the context of cardiac arrest and critical illness, dysphagia is primarily a complication of brain injury and prolonged mechanical ventilation.After a cardiac arrest, hypoxic-ischaemic brain injury can impair the complex coordination of muscles involved in(...)
• DyspnoeaLaboured or difficult breathing. Can be due to an obstruction to the flow of air into and out of the lungs (as in Bronchitis or Asthma)
• DyspraxiaInability to plan and perform purposeful movements, while still having the ability to move and be aware of the movement.

• e

• Ebstein's AnomalyA form of congenital heart disease affecting the right side of the heart: the tricuspid valve is displaced towards the apex to a varying extent, resulting in impaired right ventricular function. It can cause breathlessness, failure to thrive, cyanosis and abnormalitities of heart rhythm, although it may be asymptomatic, if mild, life expectancy is normal, if severe, corrective surgery may be necessary
• EchocardiogramAn echocardiogram (often called an "echo") is an ultrasound scan of the heart. It uses sound waves to create real-time moving images of the heart's structure and function, without using radiation. It is one of the most commonly used cardiac investigations and is almost always performed as part of the assessment following a cardiac arrest.**What it measures**An echocardiogram can assess:- **Cardiac chambers:** the size and shape of the four chambers of the heart - **Ejection(...)
• EchocardiographyA method of studying the heart’s structure and function by analyzing sound waves bounced off the heart and recorded by an electronic sensor placed on the chest. A computer processes the information to produce a one-, two- or three-dimensional moving picture that shows how the heart and heart valves are functioning.
• EcholaliaImitation of sounds or words without comprehension. This is a normal stage of language development in infants but is abnormal for adults.
• ECMOECMO (extracorporeal membrane oxygenation) is an advanced life support technique that takes over the functions of the heart and lungs outside the body when they are too severely impaired to support life. It is used in the most critical cases of cardiac arrest, cardiogenic shock, or severe respiratory failure, providing a bridge to recovery or to a definitive treatment such as a heart transplant. How ECMO works Blood is drawn out of the body through a cannula (a large tube), pumped through(...)
• EctopicsA premature contraction of the atrium or ventricle earlier than the next expected normal sinus or escape rhythm beat. Caused by an abnormal electrical focus.
• EfficacyEfficacy refers to how well a treatment, intervention, or device works under ideal, controlled conditions. In medical research, efficacy is typically measured in clinical trials where patient populations, dosing, and follow-up are carefully standardised. It is distinct from effectiveness, which describes how well a treatment works in real-world clinical practice, where patients are more varied, adherence is imperfect, and conditions are less controlled.In the context of cardiac care and(...)
• EffusionA collection of fluid in an area such as the pericardium or the pleural cavity. Such a collection, if it is large, may lead to buildup of pressure on the heart or lungs, and often results in deterioration in their function, and so it may need to be drained.
• Ejection FractionEjection fraction (EF) is the percentage of blood ejected from the left ventricle with each heartbeat. A normal ejection fraction is 55% or higher. An EF of 40 to 54% indicates mildly reduced function. An EF below 40% meets the definition of heart failure with reduced ejection fraction (HFrEF) and signals significantly impaired pumping.Ejection fraction is most commonly measured by echocardiogram, though cardiac MRI provides the most precise assessment. After cardiac arrest, EF is a(...)
• EFEjection fraction (EF) is the percentage of blood ejected from the left ventricle with each heartbeat. A normal ejection fraction is 55% or higher. An EF of 40 to 54% indicates mildly reduced function. An EF below 40% meets the definition of heart failure with reduced ejection fraction (HFrEF) and signals significantly impaired pumping.Ejection fraction is most commonly measured by echocardiogram, though cardiac MRI provides the most precise assessment. After cardiac arrest, EF is a(...)
• ElectrocardiogramA test to measure the heart's electrical activity with each heart beat. Wires are attached to the skin of the arms, legs and chest, using soft, stickon discs (called 'electrodes'). A tracing is printed on paper and gives information about the heart rate and regularity, as well as providing data about enlargement of the heart chambers and thickening of heart muscle, which may provide useful information about the nature and severity of heart problems.
• ECGA test to measure the heart's electrical activity with each heart beat. Wires are attached to the skin of the arms, legs and chest, using soft, stickon discs (called 'electrodes'). A tracing is printed on paper and gives information about the heart rate and regularity, as well as providing data about enlargement of the heart chambers and thickening of heart muscle, which may provide useful information about the nature and severity of heart problems.
• Electrocardiogram Treadmill Test (ETT)A recording of the Heart’s Rate and Rhythm while walking on a treadmill.
• ElectrodeAn electrode is a conductor that makes electrical contact with a non-metallic part of a circuit, in a medical context typically the body's tissues. Electrodes detect or deliver electrical signals and are fundamental to cardiac monitoring, diagnostic testing and rhythm management devices.Surface electrodes are adhesive patches applied to the skin. In electrocardiography (ECG), 10 surface electrodes placed on the chest, arms and legs detect the tiny electrical signals generated by cardiac(...)
• ElectroencephalogramA test that can detect and record the brain’s electrical activity. The test is done by pasting metal disks, called electrodes, to the scalp
• EEGA test that can detect and record the brain’s electrical activity. The test is done by pasting metal disks, called electrodes, to the scalp
• Electromagnetic InterferenceElectromagnetic interference (EMI) refers to electrical or magnetic signals from external sources that can potentially interfere with the sensing and function of an implanted cardiac device such as an ICD or pacemaker. Devices continuously sense the heart's electrical activity to detect arrhythmias; if an external electrical signal is misinterpreted as cardiac activity, the device may respond inappropriately.Potential consequences of EMI include inappropriate shocks, where an ICD(...)
• EMIElectromagnetic interference (EMI) refers to electrical or magnetic signals from external sources that can potentially interfere with the sensing and function of an implanted cardiac device such as an ICD or pacemaker. Devices continuously sense the heart's electrical activity to detect arrhythmias; if an external electrical signal is misinterpreted as cardiac activity, the device may respond inappropriately.Potential consequences of EMI include inappropriate shocks, where an ICD(...)
• Electrophysiological studyAn electrophysiological study (EP study) is a test used to evaluate your heart's electrical system and to check for abnormal heart rhythms. Natural electrical impulses coordinate contractions of the different parts of the heart. This helps keep blood flowing the way it should.
• EPSAn electrophysiological study (EP study) is a test used to evaluate your heart's electrical system and to check for abnormal heart rhythms. Natural electrical impulses coordinate contractions of the different parts of the heart. This helps keep blood flowing the way it should.
• Electrophysiological TestingA procedure (invasive or non-invasive) used to detect and give information about abnormal heart rhythms.
• ElectrophysiologyThe study of the electrical properties of cells and tissues
• Electrophysiology StudyAn electrophysiology study (EPS) is a specialised cardiac investigation carried out in a catheterisation laboratory to assess the electrical system of the heart in detail. It is used to identify the cause of arrhythmias, evaluate the risk of dangerous heart rhythms, and guide treatment decisions. What happens during the procedure The patient lies on an X-ray table and the procedure is usually performed under local anaesthesia with sedation. Thin, flexible wires (catheters) are inserted(...)
• EmbolismAn embolism is the lodging of an embolus, a blockage-causing piece of material, inside a blood vessel. The embolus may be a blood clot (thrombus), a fat globule, a bubble of air or other gas, or foreign material. An embolism can cause partial or total blockage of blood flow in the affected vessel.
• EmbolusAlso called embolism; a blood clot that forms in a blood vessel in one part of the body and travels to another part.
• Emergency Action Plan in SportAn Emergency Action Plan (EAP) in sport is a written protocol detailing the exact steps that should be taken if a cardiac arrest or other medical emergency occurs during sporting activity. A well-structured EAP increases the speed and effectiveness of the response and improves survival outcomes. All sports clubs, schools, gyms, and leisure facilities in the UK are encouraged to have a current EAP that covers: the location of the nearest AED, names and contact details of trained(...)
• Emergency DepartmentThe emergency department (ED), also known as accident and emergency (A&E) or the emergency room (ER), is the hospital department that assesses and treats patients with acute, urgent medical and surgical conditions. Emergency departments operate 24 hours a day, 7 days a week, and are staffed by emergency medicine consultants, doctors, nurses, and allied health professionals.For cardiac arrest patients, the emergency department plays a role in the resuscitation pathway, though many(...)
• A&EThe emergency department (ED), also known as accident and emergency (A&E) or the emergency room (ER), is the hospital department that assesses and treats patients with acute, urgent medical and surgical conditions. Emergency departments operate 24 hours a day, 7 days a week, and are staffed by emergency medicine consultants, doctors, nurses, and allied health professionals.For cardiac arrest patients, the emergency department plays a role in the resuscitation pathway, though many(...)
• Emotional labilityRapid and drastic changes in emotional state (such as laughing, crying or anger) that are inappropriate.
• Emotional LabilityEmotional lability is a condition in which a person experiences rapid, uncontrolled shifts in emotional expression, often disproportionate to the triggering situation. The person may laugh or cry suddenly and find the emotional response difficult to stop, even when it does not match how they actually feel inside. It is distinct from depression, although the two can coexist. Why it occurs after cardiac arrest Emotional lability can be a direct consequence of hypoxic brain injury. The(...)
• Emotional NumbingA feeling of emotional flatness, detachment, or being cut off from one's own feelings, from other people, or from the world. Emotional numbing is a common response to overwhelming trauma — the mind's way of protecting itself from emotional pain that is too intense to process all at once. It can manifest as an inability to feel joy, love, or warmth; feeling like a bystander in one's own life; loss of interest in things that previously brought pleasure; or a sense that the world feels(...)
• Employment and Support AllowanceEmployment and Support Allowance (ESA) is a UK welfare benefit for people who are unable to work, or whose ability to work is limited, due to illness or disability. It is being gradually replaced by Universal Credit for new claimants, but existing ESA claimants may still be on the benefit, and in some circumstances ESA (particularly contribution-based ESA, now called New Style ESA) remains available alongside Universal Credit. Types of ESANew Style ESA (contribution-based): available to(...)
• EndarterectomySurgical removal of plaque deposits or blood clots in an artery.
• EndocarditisEndocarditis is an infection of the endocardium, the inner lining of the heart, including the heart valves. It most commonly occurs when bacteria (or, less commonly, fungi) enter the bloodstream and colonise the endocardial surface, particularly where there is existing structural abnormality such as a damaged or prosthetic heart valve. The resulting infected deposits (vegetations) can damage valve leaflets, obstruct blood flow, and release emboli that travel to the brain, kidneys, and(...)
• Endocarditis ProphylaxisUse of antibiotics to prevent endocarditis at times when bacteria may be expected to enter the bloodstream (e.g. dental extractions or surgery on nose, throat, mouth or bowel). See Protocol for prevention.
• EndocardiumThe smooth membrane covering the inside of the heart. The innermost lining of the heart.
• EndomyocarditisEndomyocarditis is an inflammatory condition affecting both the myocardium (the heart muscle) and the endocardium (the inner lining membrane of the heart). It represents a combined presentation of two related conditions: myocarditis (inflammation of the heart muscle) and endocarditis (inflammation of the inner lining). In practice, the two conditions frequently co-exist, and the term endomyocarditis acknowledges this overlap.Inflammation of the heart muscle and lining can be acute (rapid(...)
• EndotheliumThe smooth inner lining of many body structures, including the heart (endocardium) and blood vessels.
• Endotracheal TubeAn endotracheal tube (ET tube) is a flexible plastic tube inserted through the mouth (or occasionally the nose) and passed through the larynx (voice box) into the trachea (windpipe). Once in place, an inflatable cuff creates a seal that protects the airway from aspiration of secretions or stomach contents, and the tube connects the patient to a mechanical ventilator or manual resuscitation bag.Endotracheal intubation is performed to secure the airway and provide mechanical ventilation(...)
• Enlarged HeartA state in which the heart is larger than normal because of heredity, long-term heavy exercise, or diseases and disorders such as obesity, high blood pressure, and coronary artery disease
• EnzymeA complex chemical capable of speeding up specific biochemical processes in the body.
• EpicardiumThe epicardium is the innermost layer of the pericardium (the protective sac surrounding the heart) and simultaneously the outermost layer of the heart wall itself. It is a thin, smooth membrane that covers the external surface of the heart muscle (myocardium) and the roots of the great vessels.The epicardium is composed of a single layer of flat epithelial cells (mesothelium) supported by connective tissue. It contains the coronary arteries and veins that supply and drain the heart(...)
• EpilepsyThere are many varied presentations. Seizure or fit activity involving parts of or the complete body.
• OestrogenA female hormone produced by the ovaries that may protect premenopausal women against heart disease. Oestrogen production stops after menopause.
• Oestrogen Replacement TherapyOestrogen replacement therapy is a form of hormone therapy in which oestrogen (the main female sex hormone) is provided to women whose natural oestrogen levels have fallen, most commonly as a result of the menopause. During the menopause, the ovaries stop producing oestrogen and progesterone, leading to symptoms including hot flushes, night sweats, vaginal dryness, mood changes, and reduced bone density. Oestrogen replacement is the most effective treatment for these symptoms.Oestrogen(...)
• ERTOestrogen replacement therapy is a form of hormone therapy in which oestrogen (the main female sex hormone) is provided to women whose natural oestrogen levels have fallen, most commonly as a result of the menopause. During the menopause, the ovaries stop producing oestrogen and progesterone, leading to symptoms including hot flushes, night sweats, vaginal dryness, mood changes, and reduced bone density. Oestrogen replacement is the most effective treatment for these symptoms.Oestrogen(...)
• Evoked potentialsElectrical responses of the brain to stimulation, recorded from the scalp.
• Executive FunctionExecutive function is the term used for a set of mental skills that enable a person to plan, focus attention, remember and follow instructions, and manage multiple tasks. These higher-order thinking abilities are controlled primarily by the prefrontal cortex, a region of the brain that is particularly vulnerable to hypoxic injury after cardiac arrest. What executive function includes Executive function is not a single ability but a collection of related skills:Planning and organisation:(...)
• Executive functionsThe ability to think and reason, to synthesize and integrate complex information and make considered judgements and decisions about what to do in a particular situation.
• Exercise-Induced ArrhythmiaExercise-induced arrhythmia refers to an abnormal heart rhythm that is triggered or worsened by physical exertion. In a normal heart, exercise causes a controlled increase in heart rate. In people with certain underlying conditions, exertion can provoke ventricular tachycardia, ventricular fibrillation, or other dangerous rhythms. Conditions associated with exercise-induced arrhythmia include CPVT (Catecholaminergic Polymorphic Ventricular Tachycardia), Long QT Syndrome, hypertrophic(...)
• Exercise Stress TestA common test to help doctors assess blood flow through coronary arteries in response to exercise, usually walking, at varied speeds and for various lengths of time on a treadmill. A stress test may include use of electrocardiography, echocardiography, and injected radioactive substances. Also called exercise test, stress test, nuclear stress test, or treadmill test
• Exercise Tolerance TestFormal exercise test whilst monitoring the patient, blood pressure and ECG using either a treadmill or bicycle ergometer. Used for detecting coronary ischaemia, arrhythmias and level of cardiovascular fitness.
• Extra-Corporeal Membrane OxygenationCirculating a patient’s blood to a machine outside the body that adds oxygen to – and removes waste carbon dioxide from – the bloodstream. Specialised service in a handful of centres across the UK. Patient’s often have to travel to a different ICU to receive the therapy.
• ECMOCirculating a patient’s blood to a machine outside the body that adds oxygen to – and removes waste carbon dioxide from – the bloodstream. Specialised service in a handful of centres across the UK. Patient’s often have to travel to a different ICU to receive the therapy.
• ExtubationExtubation is the removal of an endotracheal tube (ETT) from a patient's airway once they no longer require mechanical ventilation. It is a planned, structured procedure carried out by the critical care team when the patient has demonstrated sufficient ability to breathe independently and protect their own airway.Before extubation, clinicians assess several factors: whether the underlying reason for intubation has improved or resolved, whether the patient is awake enough to follow(...)
• EMDR (Eye Movement Desensitisation and Reprocessing)Eye Movement Desensitisation and Reprocessing (EMDR) is a structured psychological therapy used to help people process and recover from traumatic experiences. It is one of the two treatments recommended by NICE for [post-traumatic stress disorder (PTSD)](/glossary/post-traumatic-stress-disorder/), alongside trauma-focused [cognitive behavioural therapy](/glossary/cognitive-behavioural-therapy/).EMDR works on the principle that traumatic memories can become stuck in the brain's processing(...)
• EMDREye Movement Desensitisation and Reprocessing (EMDR) is a structured psychological therapy used to help people process and recover from traumatic experiences. It is one of the two treatments recommended by NICE for [post-traumatic stress disorder (PTSD)](/glossary/post-traumatic-stress-disorder/), alongside trauma-focused [cognitive behavioural therapy](/glossary/cognitive-behavioural-therapy/).EMDR works on the principle that traumatic memories can become stuck in the brain's processing(...)

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• FacemasksFacemasks in the medical context are devices worn over the nose and mouth (or held by a healthcare provider over a patient's face) to deliver supplemental oxygen, administer inhaled medications, or assist with breathing. Several types are used in cardiac and critical care settings, each designed for different purposes and oxygen delivery levels.Simple facemasks deliver oxygen concentrations of around 35 to 50% and suit patients with mild to moderate oxygen needs who are awake and(...)
• Fallots TetralogyA common heart defect associated with cyanosis. There are four parts to the defect (Tetra = four). The name 'Fallot' refers to the French doctor who described the features of the defect.
• Familial HypercholesterolaemiaA genetic predisposition to dangerously high cholesterol levels.
• Fatigue ManagementFatigue management refers to a structured set of strategies and techniques designed to help people with persistent tiredness understand, monitor, and reduce the impact of fatigue on their daily life. It is an important part of recovery for many cardiac arrest survivors, for whom fatigue is one of the most commonly reported and most disabling long-term symptoms. Why fatigue after cardiac arrest is different Post-cardiac arrest fatigue is not the same as ordinary tiredness. It is often(...)
• Fatty AcidsFatty acids are the basic structural units of dietary fats. They are chains of carbon atoms with hydrogen atoms attached, and they occur in several forms that have different effects on health and cardiovascular risk.Saturated fatty acids, found in animal products (butter, lard, full-fat dairy, fatty meat) and some plant sources (coconut oil, palm oil), raise LDL (low-density lipoprotein) cholesterol and are associated with increased coronary artery disease risk. UK dietary guidelines(...)
• Fear of RecurrenceThe fear that a cardiac arrest or life-threatening arrhythmia will happen again. Fear of recurrence is one of the most commonly reported psychological difficulties among cardiac arrest survivors and ICD patients, and can significantly affect quality of life, physical activity, return to work, and relationships. It may present as avoidance of exercise, reluctance to be alone, hypervigilance about physical symptoms, or anxiety about ICD shocks. For some people, the presence of an ICD — while(...)
• Fever A rise in body temperature above the normal
• FibrateA drug used to bring down cholesterol and triglyceride levels in your blood.
• FibrillationRapid, uncoordinated contractions of individual heart muscle fibers. The heart chamber involved can’t contract all at once and pumps blood ineffectively, if at all.
• First AidFirst aid is the initial assistance or treatment given to a person who has been injured or has suddenly become unwell, before professional medical help arrives or the person can be transported to a medical facility. The aim of first aid is to preserve life, prevent the condition from worsening, and promote recovery. First aid can be given by anyone with basic training, and in life-threatening emergencies, the actions of a bystander in the first few minutes are often decisive.In the(...)
• First-degree Heart BlockOccurs when an electrical impulse from the heart’s upper chambers (the atria) is slowed as it moves through the atria and atrioventricular (AV) node
• FlashbackA vivid, distressing involuntary re-experiencing of a traumatic event, in which the person feels as though the event is happening again in the present moment rather than being a memory. Flashbacks are a hallmark symptom of PTSD. They can be triggered by sensory cues — sounds, smells, physical sensations, images — associated with the original trauma. For cardiac arrest survivors, triggers may include hospital environments, the sound of an alarm, the feeling of chest pain, or news stories(...)
• Fluid BalancePatients in ICU are often unable to control their own fluid balance. They may be dehydrated from lack of food and drink, vomiting or diarrhoea
• FlutterFlutter refers to a rapid but organised electrical activity in a heart chamber, more regular than fibrillation but faster than normal rhythm. The term most commonly refers to atrial flutter, though ventricular flutter also exists as a distinct and more dangerous condition.Atrial flutter is a supraventricular arrhythmia in which the atria beat at around 250 to 350 times per minute, driven by a circular electrical circuit (re-entry circuit) rather than the normal pacemaker. Because the(...)
• Focal brain injuryInjury restricted to one region (as opposed to diffuse).
• Fontan OperationAn operation to connect the main veins from the systemic circulation (SVC and IVC) to the lung arteries. Blood then flows directly into the lung circulation, after returning from the body, without going through the right ventricle as would happen in a normal heart. This operation is named after a French surgeon Francis Fontan.
• Foramen OvaleThe foramen ovale is a natural oval-shaped opening between the two upper chambers of the heart (the right and left atria) that is present in every fetus during development. During fetal life, the lungs are not yet functioning for breathing, so the fetal circulation directs oxygenated blood from the placenta through the right atrium and across the foramen ovale into the left atrium, bypassing the pulmonary circulation entirely. This is a necessary and normal part of fetal circulation.At(...)
• Frontal lobesThe largest lobes of the brain, occupying the front part of the cerebral hemispheres. As well as containing the areas controlling voluntary movement and speech production, the frontal lobes are involved in the executive functions of thinking and reasoning, the integration of complex information, judgement, decision-making and planning for the future. They also have an important role in social behaviour, personality and emotion.
• Fusiform AneurysmA tube-shaped aneurysm that causes the artery to bulge outward. Involves the entire circumference (outside wall) of the artery

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• Generalised Anxiety Disorder-7The Generalised Anxiety Disorder-7. A validated 7-item self-report questionnaire used to screen for and measure the severity of anxiety symptoms over the past two weeks, scored 0–21. Scores of 5, 10, and 15 represent mild, moderate, and severe anxiety respectively. The GAD-7 is widely used in GP and outpatient settings, often alongside the PHQ-9. It may be used in post-arrest and cardiac rehabilitation follow-up to identify anxiety that would benefit from psychological support or(...)
• GAD-7The Generalised Anxiety Disorder-7. A validated 7-item self-report questionnaire used to screen for and measure the severity of anxiety symptoms over the past two weeks, scored 0–21. Scores of 5, 10, and 15 represent mild, moderate, and severe anxiety respectively. The GAD-7 is widely used in GP and outpatient settings, often alongside the PHQ-9. It may be used in post-arrest and cardiac rehabilitation follow-up to identify anxiety that would benefit from psychological support or(...)
• GastrostomyThe creation of an opening into the stomach for the administration of foods and fluids when swallowing is impossible.
• Gated Blood Pool ScanAn x-ray analysis of how blood pools in the heart during rest and exercise. The test uses a radioactive substance to tag red blood cells to allow doctors to estimate the heart’s overall ability to pump and its ability to compensate for one or more blocked arteries. Also called MUGA (multiple gated acquisition scan) or nuclear ventriculography
• General PractitionerA general practitioner (GP) is a family doctor who provides primary care to patients of all ages. GPs are usually the first point of contact with NHS healthcare services and can assess, treat, and refer patients to specialist services as needed. They hold a comprehensive view of a patient's health, managing ongoing conditions alongside acute problems.After a cardiac arrest and hospital discharge, the GP plays an important coordinating role. They can prescribe and review ongoing cardiac(...)
• Generator ReplacementA planned surgical procedure to replace the pulse generator (battery unit) of an ICD or pacemaker when its battery reaches end of service. The leads are usually left in place and reconnected to the new generator. The procedure is typically performed under local anaesthetic and is much less complex than the original implant. Battery longevity varies by device and how often it delivers therapy, but most ICD generators last 5–10 years.
• Genetic TestingBlood tests that study a person’s genes to find out if he or she is at risk for certain diseases that are passed down through family members
• Genetic Testing in Cardiac ConditionsGenetic testing in cardiac conditions involves analysing a blood or saliva sample to look for inherited variants in genes associated with heart conditions that can cause arrhythmias, cardiomyopathy, or sudden cardiac death. It is an important part of investigating the cause of cardiac arrest, particularly in younger patients or those without obvious structural heart disease. When it is offered Genetic testing is typically offered when a cardiac condition with a known or suspected genetic(...)
• Glasgow Coma ScaleThe Glasgow Coma Scale (GCS) is a standardised clinical scoring system used to describe and monitor a patient's level of consciousness following brain injury or any condition affecting neurological function. It was developed by Teasdale and Jennett at the University of Glasgow in 1974 and is now one of the most widely used neurological assessment tools in emergency medicine and intensive care worldwide.The GCS assesses three components of behaviour: eye opening (scored 1 to 4), verbal(...)
• GCSThe Glasgow Coma Scale (GCS) is a standardised clinical scoring system used to describe and monitor a patient's level of consciousness following brain injury or any condition affecting neurological function. It was developed by Teasdale and Jennett at the University of Glasgow in 1974 and is now one of the most widely used neurological assessment tools in emergency medicine and intensive care worldwide.The GCS assesses three components of behaviour: eye opening (scored 1 to 4), verbal(...)
• GlutamateGlutamate is the principal excitatory neurotransmitter in the brain, responsible for activating neurons and facilitating processes including learning, memory and synaptic plasticity. Under normal conditions, glutamate is carefully regulated within synapses and rapidly cleared after use. However, when brain cells are deprived of oxygen, as occurs during cardiac arrest and hypoxic-ischaemic brain injury (HIBI), this regulation breaks down.During and after cardiac arrest, oxygen-starved(...)
• Glyceryl Trinitrate (Nitroglycerin)A drug that dilates blood vessels and is used mainly to prevent and treat angina. Side effects may include flushing, headache, and fainting. Glyceryl trinitrate is also applied topically in the treatment of anal fissures.
• GTNA drug that dilates blood vessels and is used mainly to prevent and treat angina. Side effects may include flushing, headache, and fainting. Glyceryl trinitrate is also applied topically in the treatment of anal fissures.
• Graded Exposure TherapyGraded exposure therapy (also called graduated exposure or exposure therapy) is a psychological treatment technique used to help people reduce fear and avoidance behaviour by systematically and gradually approaching feared situations, activities, or sensations in a controlled and supported way. It is one of the most effective psychological interventions for anxiety, PTSD, and phobias, and is a central component of cognitive behavioural therapy. Why exposure works Avoidance provides(...)
• Graduated Return to ActivityA graduated return to activity is a structured, stepwise approach to resuming physical activity after a serious health event such as cardiac arrest. Rather than attempting to return to previous activity levels immediately, a graduated plan begins at a low level of exertion and increases incrementally, allowing the body and heart to adapt safely under medical guidance. Why gradual progression matters After cardiac arrest, the heart and body may be significantly deconditioned, and fear of(...)
• GraftIn surgery, a graft is a piece of tissue or material that is transplanted from one location to another to repair, replace, or augment a damaged or absent structure. Grafts may be taken from the patient's own body (autograft), from another person (allograft or homograft), from an animal (xenograft), or be made from synthetic material (prosthetic graft).In cardiac surgery, the most common use of grafts is in coronary artery bypass grafting (CABG), where blood vessels harvested from(...)
• Graham Steell MurmurA soft high-pitched heart murmur best heard over the second left intercostal space in early diastole. It is a sign of Pulmonary Regurgitation
• Grey matterNerve cell bodies in the brain, which have a greyish appearance and make up the cerebral cortex.
• GriefThe natural emotional response to loss. Grief is not only experienced when someone dies — it can follow any significant loss, including the loss of health, identity, independence, or the life a person expected to have. After cardiac arrest, grief is experienced in multiple ways: by co-survivors who may grieve the person their partner was before the arrest, or the life they had together before it was altered by an ICD or cognitive impairment; by survivors grieving their previous sense of(...)
• Group 1 Driving LicenceA Group 1 driving licence is the standard UK car and motorcycle licence held by most drivers. Following cardiac arrest or ICD implantation, Group 1 licence holders face a period of mandatory driving restriction, but the rules are less stringent than those that apply to Group 2 licence holders (lorry and bus drivers). After cardiac arrest Following an out-of-hospital cardiac arrest or a sustained ventricular arrhythmia causing incapacity, the DVLA requires a minimum period off driving.(...)
• Group 2 Driving LicenceA Group 2 driving licence is the licence category required in the UK to drive large goods vehicles (LGV, formerly HGV) and passenger-carrying vehicles (PCV), including buses and coaches. Group 2 licence holders are subject to significantly stricter medical standards than ordinary car drivers (Group 1), particularly following cardiac events such as cardiac arrest. Why Group 2 standards are stricter Group 2 drivers are in control of larger, heavier vehicles with greater potential for harm to(...)
• GuidelineA clinical guideline is a systematically developed statement designed to help clinicians and patients make informed decisions about appropriate care for specific clinical circumstances. Guidelines are produced by authoritative bodies using formal processes of evidence review, expert consensus and public consultation, and are regularly updated as new evidence emerges.In the UK, the National Institute for Health and Care Excellence (NICE) produces guidelines covering clinical management,(...)
• GuidewireA small, bendable wire that is threaded through an artery; it helps doctors position a catheter so they can perform angioplasty or stent procedures.
• GyrusA ridge of the cerebral cortex.

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• Hospital Anxiety and Depression ScaleThe Hospital Anxiety and Depression Scale. A widely used, validated 14-item self-report questionnaire that screens for anxiety and depression. It is divided into two 7-item subscales — one for anxiety (HADS-A) and one for depression (HADS-D) — each scored 0–21. A score of 8 or above on either subscale is generally considered a clinically significant level of symptoms, with higher scores indicating greater severity. The HADS was originally developed for use with hospital outpatients but is(...)
• HADSThe Hospital Anxiety and Depression Scale. A widely used, validated 14-item self-report questionnaire that screens for anxiety and depression. It is divided into two 7-item subscales — one for anxiety (HADS-A) and one for depression (HADS-D) — each scored 0–21. A score of 8 or above on either subscale is generally considered a clinically significant level of symptoms, with higher scores indicating greater severity. The HADS was originally developed for use with hospital outpatients but is(...)
• HaematomaA collection of blood forming a definite swelling which compresses and damages the brain around it.
• HaemofilterA haemofilter is a machine used to perform continuous renal replacement therapy (CRRT), a form of kidney support for critically ill patients whose kidneys are unable to adequately filter the blood and remove waste products and excess fluid. Unlike conventional haemodialysis (which runs intermittently over 3 to 4 hours), CRRT using a haemofilter runs continuously over 24 hours, making it suitable for intensive care patients who are too unstable to tolerate the fluid shifts of intermittent(...)
• HaemoglobinThe red coloured pigment in red blood cells that binds avidly to oxygen. Composed of protein and iron. Allows red blood cells to carry oxygen to a patient’s organs & tissues.
• Haemorrhage Profuse bleeding from ruptured blood vessels
• Head injury - mild/minorMay causes brief loss of consciousness for 15 minutes or less with a period of post-traumatic amnesia of less than 1 hour.
• Head injury - moderateDefined as being a condition where the patient has been in a coma for 6 hours, and a period of post-traumatic amnesia of up to 24 hours.
• Head injury - severeDefined as being a condition where the patient has been in a coma for 6 hours or more, or a post-traumatic amnesia of 24 hours or more.
• Health AnxietyExcessive worry about having or developing a serious illness, disproportionate to any symptoms or medical findings. Also called illness anxiety disorder. Health anxiety is particularly common following life-threatening events such as [cardiac arrest](/glossary/cardiac-arrest/), and in people living with chronic conditions such as heart disease.For ICD patients, health anxiety can manifest as excessive monitoring of physical sensations, repeatedly checking the device, fear of every(...)
• HeartThe heart is a muscular organ which pumps blood through the blood vessels of the circulatory system. to provide the body with oxygen and nutrients, as well as assists in the removal of metabolic wastes. The heart is located in the middle compartment of the chest. The heart has 2 pumps, each composed of one atrium and one ventricle with the contraction sequence controlled by it’s own electrical system. There are heart valves ensuring that flow is only in one direction.
• Heart AgeA scoring system that uses biometric data to calculate the risk of a heart attack for an individual and expresses this risk in terms of notional heart age
• Heart Assist DeviceA heart assist device (also called a ventricular assist device or VAD) is a mechanical pump surgically implanted to supplement or replace the pumping function of a failing heart. These devices are used when the heart can no longer maintain adequate circulation despite optimal medical therapy.The most commonly used type is the left ventricular assist device (LVAD), which draws blood from the left ventricle and pumps it into the aorta, bypassing the weakened heart muscle. LVADs are used in(...)
• HADA heart assist device (also called a ventricular assist device or VAD) is a mechanical pump surgically implanted to supplement or replace the pumping function of a failing heart. These devices are used when the heart can no longer maintain adequate circulation despite optimal medical therapy.The most commonly used type is the left ventricular assist device (LVAD), which draws blood from the left ventricle and pumps it into the aorta, bypassing the weakened heart muscle. LVADs are used in(...)
• Heart AttackDeath of, or damage to, part of the heart muscle caused by a lack of oxygen-rich blood flowing to the heart
• Heart BlockHeart block is a condition affecting the conduction system of the heart, in which electrical signals that coordinate heartbeats are delayed or completely blocked as they pass from the atria to the ventricles. In a healthy heart, electrical impulses travel from the sinoatrial (SA) node through the atria and then through the atrioventricular (AV) node and His-Purkinje system to activate the ventricles in a coordinated sequence. In heart block, this conduction pathway is disrupted at the(...)
• Heart FailureSee 'Congestive Heart Failure'. A condition in which the pumping action of the heart is inadequate due to damaged heart valves, ventricular muscle or both. This results in back pressure of blood, with congestion or organs
• HFSee 'Congestive Heart Failure'. A condition in which the pumping action of the heart is inadequate due to damaged heart valves, ventricular muscle or both. This results in back pressure of blood, with congestion or organs
• Heart Failure with Preserved Ejection FractionHeart failure with preserved ejection fraction (HFpEF) occurs when the heart muscle contracts normally (ejection fraction is 50% or above) but the left ventricle has become stiff and relaxes poorly, impairing its ability to fill properly between beats. This diastolic dysfunction reduces the amount of blood available to pump with each cycle, causing symptoms identical to other forms of heart failure despite a normal pumping percentage.HFpEF accounts for approximately half of all heart(...)
• Heart-Lung BypassHeart-lung bypass is the technique by which the functions of the heart and lungs are temporarily taken over by an external machine during open heart surgery, allowing the surgeon to operate on a still, empty heart. The heart is stopped using a cardioplegic solution, and blood is diverted from the right side of the heart, passed through an oxygenator (which adds oxygen and removes carbon dioxide), and returned to the arterial circulation via a pump. The entire circuit is known as a(...)
• Heart-Lung MachineA heart-lung machine (also called a cardiopulmonary bypass machine or bypass pump) is the device used during open heart surgery to temporarily take over the functions of the heart and lungs. It draws blood from the right side of the heart, pumps it through an oxygenator (which adds oxygen and removes carbon dioxide), and returns the oxygenated blood to the arterial circulation, maintaining blood flow to the body's organs while the heart is stopped and the surgeon operates inside it.The(...)
• Heart ManualA Manual given to patients which details their cardiac rehabilitation programme after heart illness. Sometimes used as an alternative to exercise class based rehabilitation.
• Heart MurmurA heart murmur is an abnormal heart sound produced by turbulent blood flow within the heart or through the heart valves, detected by listening with a stethoscope. Normal heart sounds (the familiar 'lub-dub') are produced by the closing of the heart valves; murmurs represent additional sounds created when blood flow becomes turbulent rather than smooth.Murmurs are graded on a scale of 1 to 6 based on their loudness, and are characterised by their timing (systolic, during ventricular(...)
• Heart RateHeart rate is the number of times the heart beats per minute (bpm). In healthy adults at rest, a normal heart rate falls between 60 and 100 bpm. Heart rate varies with age, fitness level, body position, emotion, temperature, and physiological state; it is typically higher in children and lower in very fit athletes, who may have resting rates well below 60 bpm.The heart rate is set primarily by the sinoatrial (SA) node, the heart's natural pacemaker, which fires spontaneously at a basal(...)
• Heart Rate VariabilityHeart Rate Variability (HRV) is the variation in time between consecutive heartbeats, measured in milliseconds. A higher HRV generally reflects a healthy and adaptable autonomic nervous system, indicating the heart can respond flexibly to physical and emotional demands. Reduced HRV is associated with cardiovascular risk and may indicate autonomic dysfunction following cardiac arrest or in the context of heart failure. HRV is measured using ECG analysis or consumer wearable devices.(...)
• Heart RhythmThe pattern of the heartbeats. The heart should beat regularly with an even space between each heartbeat.
• Heart SoundsHeart sounds are the audible sounds produced by the mechanical activity of the heart, traditionally heard through a stethoscope placed on the chest wall. In a healthy heart, two main sounds are heard with each cardiac cycle: the first heart sound (S1) and the second heart sound (S2).S1 is produced by the closure of the two atrioventricular valves (the mitral and tricuspid valves) at the beginning of ventricular systole, as the ventricles start to contract. It is described as a(...)
• Heart Support GroupA group of people who have gone through similar heart disease experiences who meet, talk and give each other support.
• Heart TransplantOperation which involves replacing the diseased heart with the healthy heart of a donor.
• Heart Valve DiseaseHeart valve disease refers to any condition in which one or more of the four heart valves (aortic, mitral, pulmonary, and tricuspid) is damaged, diseased, or abnormally formed, impairing the flow of blood through the heart. The valves are one-way gates ensuring blood flows in the correct direction; when they malfunction, the heart must work harder and symptoms develop.Valve disease takes two main forms. Stenosis occurs when the valve leaflets thicken, fuse, or calcify, narrowing the(...)
• Helicopter-Based Emergency ServiceA helicopter-based emergency service (HEMS), commonly known as an air ambulance, deploys helicopters crewed by highly trained paramedics and doctors to provide advanced pre-hospital care and rapid transport of seriously ill or injured patients to hospital.HEMS serves two main functions. In primary responses, the helicopter is dispatched to the scene of an emergency, such as a serious trauma, major illness, or out-of-hospital cardiac arrest, to deliver advanced medical interventions(...)
• HEMSA helicopter-based emergency service (HEMS), commonly known as an air ambulance, deploys helicopters crewed by highly trained paramedics and doctors to provide advanced pre-hospital care and rapid transport of seriously ill or injured patients to hospital.HEMS serves two main functions. In primary responses, the helicopter is dispatched to the scene of an emergency, such as a serious trauma, major illness, or out-of-hospital cardiac arrest, to deliver advanced medical interventions(...)
• HaematocritHaematocrit (also written as hematocrit) is a blood test measurement that expresses the proportion of whole blood made up of red blood cells, stated as a percentage. For example, a haematocrit of 42% means that 42% of the total blood volume consists of red blood cells, with the remainder being plasma and other components.Normal haematocrit ranges are approximately 36 to 48% in women and 40 to 52% in men, though laboratory reference ranges vary slightly. A low haematocrit indicates(...)
• HaemochromatosisA disease in which too much iron builds up in the body (iron overload). Too much iron in the heart can cause irregular heartbeats (arrhythmias) and heart failure. Too much iron in the pancreas can lead to diabetes.
• HaemodynamicsThe forces involved in circulating blood through the cardiovascular system. The heart adapts its haemodynamic performance to the needs of the body, increasing its output of blood when muscles are working and decreasing output when the body is at rest.
• HeparinA medicine used to slow the clotting of the blood.
• HeredityHeredity is the biological mechanism by which genetic information is transmitted from parent to child, determining inherited characteristics including physical traits, susceptibility to disease, and in some cases, specific medical conditions. Each person inherits roughly half of their genetic material from each biological parent, with variations in specific genes that can alter the function of proteins and cells.In cardiology, hereditary factors are important in a range of conditions(...)
• Hibernating MyocardiumHibernating myocardium is a condition in which an area of heart muscle has chronically reduced blood flow due to significant narrowing of the supplying coronary artery, but has adapted by downregulating its metabolic and contractile activity rather than dying. The muscle cells are alive (viable) but functioning poorly or not at all, appearing weakened or non-contracting on imaging. Crucially, if blood flow is restored by coronary revascularisation (PCI or CABG), the hibernating muscle can(...)
• High Blood PressureHigh blood pressure is the common term for hypertension: a condition in which the force of blood against the artery walls is persistently elevated. Blood pressure is measured in millimetres of mercury (mmHg) and expressed as systolic (peak pressure when the heart beats) over diastolic (pressure between beats). A reading consistently above 140/90 mmHg is defined as hypertension in most adults.High blood pressure is one of the most common and important modifiable cardiovascular risk(...)
• High Density Lipoprotein (HDL)High density lipoprotein (HDL) is a type of lipoprotein particle that transports cholesterol through the bloodstream from peripheral tissues back to the liver, where it can be processed and excreted. This reverse cholesterol transport mechanism is thought to be one of the key ways in which HDL protects against coronary artery disease, which is why it is often referred to as 'good cholesterol.'Higher levels of HDL cholesterol are associated with a lower risk of heart attack and cardiac(...)
• HDLHigh density lipoprotein (HDL) is a type of lipoprotein particle that transports cholesterol through the bloodstream from peripheral tissues back to the liver, where it can be processed and excreted. This reverse cholesterol transport mechanism is thought to be one of the key ways in which HDL protects against coronary artery disease, which is why it is often referred to as 'good cholesterol.'Higher levels of HDL cholesterol are associated with a lower risk of heart attack and cardiac(...)
• High Dependency UnitA high dependency unit (HDU), also known as a step-down unit or level 2 care area, is a hospital ward that provides intensive monitoring and specialist nursing care for patients who are more seriously ill than can be managed on a general ward, but who do not require the full level of organ support of an intensive care unit (ICU). The nurse-to-patient ratio in an HDU is typically 1:2 to 1:3, intermediate between a general ward and an ICU.HDU care is appropriate for patients requiring one(...)
• HDUA high dependency unit (HDU), also known as a step-down unit or level 2 care area, is a hospital ward that provides intensive monitoring and specialist nursing care for patients who are more seriously ill than can be managed on a general ward, but who do not require the full level of organ support of an intensive care unit (ICU). The nurse-to-patient ratio in an HDU is typically 1:2 to 1:3, intermediate between a general ward and an ICU.HDU care is appropriate for patients requiring one(...)
• HippocampusA structure on the inner surface of the temporal lobes, which is made up mainly of grey matter and has an important role in memory processes. Damage to the hippocampus may lead to memory problems.
• Holter MonitorA Holter monitor is a small, wearable device that continuously records the heart's electrical activity (ECG) over a period of 24 hours, 48 hours, 7 days, or occasionally longer. It is used to detect arrhythmias that may be intermittent and therefore not captured by a standard resting ECG, which records only a few seconds of heart rhythm.The patient wears several sticky electrode patches on the chest, connected by wires to a small recording device clipped to a belt or carried in a pocket.(...)
• HomeostasisThe ability or tendency of an organism or cell to maintain internal equilibrium by adjusting its physiological processes. For example, sweating when hot in order to keep the core body temperature at 98.6 degrees maintains homeostasis.
• HomocysteineHomocysteine is a sulphur-containing amino acid produced in the body as an intermediate product of methionine metabolism. It is normally present in the blood in small amounts and is rapidly converted to other compounds, a process requiring B vitamins (folate, B6, and B12) as co-factors. When these vitamins are deficient, or in people with certain genetic variants, homocysteine accumulates in the blood.Elevated homocysteine levels (hyperhomocysteinaemia) have been associated with an(...)
• HomograftA homograft (also called an allograft) is a tissue or organ transplant taken from another human being. In cardiac surgery, the term most commonly refers to a homograft heart valve: a valve (typically the aortic or pulmonary valve along with its root and attached tissue) removed from a human donor heart after death, preserved, and used as a replacement in a recipient patient.Homograft valves have several clinical advantages. Because the tissue is human in origin, it does not require the(...)
• Hormone Replacement TherapyHormone replacement therapy (HRT) is a treatment that replaces hormones (primarily oestrogen, often combined with progestogen) that decline during menopause. It is used to relieve menopausal symptoms including hot flushes, night sweats, sleep disturbance, mood changes, and vaginal dryness, and has benefits for bone density and long-term health.For women who have had a cardiac arrest or have significant cardiovascular risk, the question of whether HRT is safe is an important one. Current(...)
• HRTHormone replacement therapy (HRT) is a treatment that replaces hormones (primarily oestrogen, often combined with progestogen) that decline during menopause. It is used to relieve menopausal symptoms including hot flushes, night sweats, sleep disturbance, mood changes, and vaginal dryness, and has benefits for bone density and long-term health.For women who have had a cardiac arrest or have significant cardiovascular risk, the question of whether HRT is safe is an important one. Current(...)
• HormonesChemicals released into the bloodstream that control different functions in the body, including metabolism, growth, sexual development, and responses to stress or illness.
• HyperHyper is a Greek prefix meaning 'above', 'over', or 'excessive'. In medical terminology, it indicates that a measurement or condition exceeds the normal range. The opposite prefix is hypo (meaning 'below' or 'insufficient').In cardiovascular and critical care medicine, hyper- appears in many important clinical terms. Hypertension means abnormally high blood pressure. Hyperkalaemia means abnormally high blood potassium levels, which can cause dangerous cardiac arrhythmias and is one of(...)
• HyperarousalA state of heightened physical and psychological alertness that persists after a traumatic experience, even when there is no immediate danger. Hyperarousal is one of the three core symptom clusters of PTSD (alongside re-experiencing and avoidance). It can manifest as an exaggerated startle response — jumping at sounds that others barely notice — difficulty relaxing, irritability, angry outbursts, difficulty falling or staying asleep, and an inability to switch off. For co-survivors,(...)
• Hyperbaric oxygen therapyA specialized treatment sometimes used in severe anoxic states - particularly after carbon monoxide poisoning - which involves giving pure oxygen at increased pressure in a hyperbaric chamber.
• HypertensionHypertension, or high blood pressure, is a common condition in which the force of blood against the artery walls is persistently elevated. Blood pressure is expressed as two numbers: systolic pressure (the pressure when the heart beats) over diastolic pressure (the pressure when the heart rests between beats), measured in millimetres of mercury (mmHg). A reading consistently above 140/90 mmHg is considered hypertensive in most adults, though targets may differ for individuals with diabetes(...)
• Hypertrophic CardiomyopathyHypertrophic cardiomyopathy (HCM) is an inherited heart muscle disease in which the cardiac muscle becomes abnormally thick (hypertrophied), most commonly affecting the interventricular septum (the wall between the ventricles). The thickened muscle stiffens the heart, may obstruct blood flow leaving the left ventricle, and creates a substrate for life-threatening arrhythmias.HCM is the most common cause of sudden cardiac arrest in young people and athletes, and is present in around 1 in(...)
• HCMHypertrophic cardiomyopathy (HCM) is an inherited heart muscle disease in which the cardiac muscle becomes abnormally thick (hypertrophied), most commonly affecting the interventricular septum (the wall between the ventricles). The thickened muscle stiffens the heart, may obstruct blood flow leaving the left ventricle, and creates a substrate for life-threatening arrhythmias.HCM is the most common cause of sudden cardiac arrest in young people and athletes, and is present in around 1 in(...)
• Hypertrophic Obstructive CardiomyopathyHypertrophic obstructive cardiomyopathy (HOCM) is the obstructive form of hypertrophic cardiomyopathy (HCM), in which abnormal thickening of the upper interventricular septum narrows the pathway through which blood is ejected from the left ventricle into the aorta. This narrowing produces a dynamic obstruction in the left ventricular outflow tract (LVOT), meaning the obstruction varies in severity depending on heart rate, filling, and contractile state.In HOCM, as the left ventricle(...)
• HOCMHypertrophic obstructive cardiomyopathy (HOCM) is the obstructive form of hypertrophic cardiomyopathy (HCM), in which abnormal thickening of the upper interventricular septum narrows the pathway through which blood is ejected from the left ventricle into the aorta. This narrowing produces a dynamic obstruction in the left ventricular outflow tract (LVOT), meaning the obstruction varies in severity depending on heart rate, filling, and contractile state.In HOCM, as the left ventricle(...)
• HypertrophyHypertrophy is the enlargement of a tissue or organ due to an increase in the size of its individual cells, driven by increased workload or other stimuli. Unlike hyperplasia (which involves an increase in the number of cells), hypertrophy involves existing cells becoming larger and producing more structural proteins.In the heart, myocardial hypertrophy is both an adaptive and a pathological process. The heart muscle responds to chronically increased workload by enlarging individual(...)
• Hyperventilate To breathe in an abnormally deep, long, and rapid manner, sometimes resulting in cramp and dizziness.
• HyperventilationHyperventilation is abnormally rapid or deep breathing that eliminates carbon dioxide from the blood faster than it is produced by the body. As blood carbon dioxide levels fall, the blood becomes more alkaline (respiratory alkalosis), which causes a cascade of physiological effects including narrowing of blood vessels in the brain, altered nerve excitability, and shifts in calcium and potassium binding.Symptoms of hyperventilation include tingling or numbness around the mouth and in the(...)
• HypervigilanceHypervigilance is a state of heightened alertness in which a person is constantly and often exhaustingly on the lookout for signs of danger or threat. In the context of cardiac arrest survival, hypervigilance is one of the most commonly reported psychological symptoms and can significantly affect daily life, relationships, and wellbeing.**What it feels like**A survivor experiencing hypervigilance may be constantly monitoring their own heartbeat, acutely aware of any chest sensation,(...)
• HypoHypo is a Greek prefix meaning 'below', 'under', or 'insufficient'. In medical terminology, it indicates that a measurement or condition falls below the normal range. The opposite prefix is hyper (meaning 'above' or 'excessive').In cardiovascular and critical care medicine, hypo- appears in many important clinical terms. Hypotension means abnormally low blood pressure. Hypokalaemia means abnormally low blood potassium levels, which can cause dangerous cardiac arrhythmias and is one of(...)
• HypoglycaemiaHypoglycaemia is a condition in which the blood glucose (blood sugar) level falls below the normal range, typically defined as below 4.0 mmol/L in adults. Glucose is the primary fuel source for the brain; when blood glucose falls too low, the brain is deprived of energy and neurological symptoms develop rapidly. The severity of symptoms increases with the degree and duration of hypoglycaemia.Symptoms progress in stages. Early symptoms are driven by adrenaline release (the body's attempt(...)
• HypokinesiaDecreased muscle movement. In relation to the heart, hypokinesia refers to decreased heart wall motion during each heartbeat. It is associated with cardiomyopathy, heart failure, or heart attack. Also called hypokinesis.
• HypopituitarismHypopituitarism is a condition in which the pituitary gland fails to produce sufficient levels of one or more of its hormones. The pituitary gland, a small structure at the base of the brain, controls a wide network of other endocrine glands by releasing hormones that regulate growth, reproduction, thyroid function, adrenal function and fluid balance. When pituitary output is impaired, the downstream effects depend on which hormones are deficient.In the context of acquired brain injury,(...)
• HypoplasticSmaller than normal or underdeveloped.
• Hypoplastic Left Heart SyndromeHypoplastic left heart syndrome (HLHS) is a severe congenital heart defect in which the entire left side of the heart (including the left ventricle, mitral valve, aortic valve, and ascending aorta) is severely underdeveloped and unable to support the systemic circulation. It is one of the most complex and life-threatening congenital heart conditions.In a baby with HLHS, the single right ventricle must supply both the pulmonary and systemic circulations, which it can only do through(...)
• Hypoplastic Right Heart SyndromeHypoplastic right heart syndrome is a spectrum of congenital heart conditions in which the right side of the heart (the right ventricle and its associated valves) is abnormally small and underdeveloped, severely limiting its ability to pump blood into the pulmonary circulation to be oxygenated. The spectrum includes hypoplastic right ventricle associated with pulmonary atresia or pulmonary stenosis, Ebstein's anomaly (where the tricuspid valve is displaced downward and part of the right(...)
• HypotensionHypotension means abnormally low blood pressure. It is generally defined as a systolic blood pressure below 90 mmHg, though what is considered clinically significant depends on the individual's baseline and the clinical context. Some people have naturally low blood pressure and are asymptomatic; in others, the same reading causes significant symptoms or indicates a dangerous state.In the acute setting following cardiac arrest, hypotension is a common and serious complication of(...)
• HypothalamusA small structure just above the brain stem. The hypothalamus detects levels of hormones in the blood and controls the pituitary gland's release of hormones in order to keep the levels stable (also see pituitary gland).
• HypoxaemiaHypoxaemia is the medical term for abnormally low oxygen levels in the blood, specifically a reduced partial pressure of oxygen in arterial blood (PaO2) or a reduced oxygen saturation of haemoglobin (SpO2 or SaO2). Hypoxaemia and hypoxia are related but distinct: hypoxaemia refers to low oxygen in the blood, while hypoxia refers to insufficient oxygen delivery to the tissues. Severe hypoxaemia will cause hypoxia if prolonged, but the two terms are not interchangeable.Hypoxaemia can(...)
• HypoxiaHypoxia means an abnormally low level of oxygen in the body's tissues. It is distinct from hypoxaemia, which specifically refers to low oxygen in the blood, though the two terms are often used interchangeably in clinical practice. When cells receive insufficient oxygen, they cannot maintain normal aerobic metabolism and begin to fail, potentially leading to cell death if the deprivation is severe or prolonged.In the context of cardiac arrest, hypoxia is both a cause and a consequence.(...)
• Hypoxic-Ischaemic EncephalopathyHypoxic-ischaemic encephalopathy (HIE) is brain injury caused by a combination of insufficient oxygen (hypoxia) and reduced blood flow (ischaemia). It is the most serious complication of cardiac arrest and the leading cause of death and disability in survivors who are initially resuscitated. What happens to the brain During cardiac arrest, blood flow to the brain stops completely. Brain cells have very limited energy reserves and begin to fail within minutes. The longer the brain is(...)
• Hypoxic-ischaemic injuryDamage caused by an interruption of oxygen supply (hypoxia) linked with a reduction in the blood flow to the brain (ischaemia), such as occurs when the heart stops beating in a cardiac arrest.

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• ICU DiaryA written record, often kept at the bedside in an ICU, in which family members, friends, and staff note down day-to-day events, observations, and messages during a patient's critical illness. ICU diaries were developed to help survivors make sense of a period they have no memory of — filling the gaps that sedation and illness create. Reading the diary during recovery can help reduce the incidence of PTSD, anxiety, and depression in survivors. Keeping the diary is also therapeutic for(...)
• Identity and Sense of Self After Cardiac ArrestMany cardiac arrest survivors describe a profound disruption to their sense of who they are following the event. This is not simply a metaphor: the experience of near-death, combined with cognitive changes, physical limitations, role changes, and altered relationships, can fundamentally challenge a person's understanding of themselves and their place in the world. How identity can be affected Identity disruption after cardiac arrest can take many forms:Loss of the "pre-arrest self":(...)
• IdiopathicIdiopathic is a medical adjective describing a condition or disease that has no identifiable or known cause. In modern usage, a diagnosis of 'idiopathic' indicates that thorough investigation has not revealed a specific underlying cause. The term comes from the Greek idios (one's own) and pathos (suffering).In cardiology, the term appears in several important clinical contexts. Idiopathic ventricular fibrillation (IVF) is the diagnosis given when a patient survives cardiac arrest due to(...)
• Idiopathic Ventricular FibrillationIdiopathic ventricular fibrillation (IVF) is a diagnosis given when a person has survived ventricular fibrillation and subsequent thorough investigation (including ECG, echocardiogram, cardiac MRI, coronary angiography, electrophysiology study, provocation testing, and genetic testing) has failed to identify any structural, electrical, or inherited cause. It is a diagnosis of exclusion, meaning it is only made after all other explanations have been ruled out. How common is it Idiopathic VF(...)
• IdioventricularIdioventricular describes a heart rhythm that arises from within the ventricles themselves, independent of the heart's normal supraventricular pacemakers (the sinoatrial node and atrioventricular node). When these higher pacemakers fail or are suppressed, the ventricles beat under the control of their own inherent subsidiary pacemaker cells.The most common clinical context is idioventricular rhythm (IVR), which occurs in complete heart block, after cardiac arrest, or when SA and AV node(...)
• ImmunosuppressantsImmunosuppressants are medicines that reduce the activity of the body's immune system. They are used primarily in transplantation medicine to prevent the immune system from attacking and rejecting a donor organ such as a transplanted heart, and they are also used to treat certain autoimmune and inflammatory conditions in which the immune system mistakenly damages the body's own tissues.After heart transplantation, recipients must take immunosuppressant medicines for life. Without them,(...)
• Impedance PlethysmographyImpedance plethysmography is a non-invasive diagnostic technique that measures changes in electrical impedance (resistance to electrical current) in a limb, most commonly the leg, to assess blood volume changes within the veins. Because blood has a different electrical conductivity from surrounding tissue, changes in blood volume alter the measured impedance; these changes are recorded to detect abnormalities in blood flow or venous filling.The technique was historically used to detect(...)
• Implantable Cardioverter DefibrillatorAn implantable cardioverter defibrillator (ICD) is a small electronic device surgically implanted inside the body, most commonly below the left collarbone, that continuously monitors heart rhythm and delivers targeted electrical therapy to correct life-threatening arrhythmias. It is the most effective treatment for preventing sudden cardiac death in people who are at high risk of, or who have survived, ventricular fibrillation or sustained ventricular tachycardia.The ICD consists of a(...)
• ICDAn implantable cardioverter defibrillator (ICD) is a small electronic device surgically implanted inside the body, most commonly below the left collarbone, that continuously monitors heart rhythm and delivers targeted electrical therapy to correct life-threatening arrhythmias. It is the most effective treatment for preventing sudden cardiac death in people who are at high risk of, or who have survived, ventricular fibrillation or sustained ventricular tachycardia.The ICD consists of a(...)
• Implantable Loop RecorderAn electronic device that is surgically implanted over the chest wall to detect arrhythmias. The ILR can be interogated by remote monitoring.
• ILRAn electronic device that is surgically implanted over the chest wall to detect arrhythmias. The ILR can be interogated by remote monitoring.
• Implantable Loop RecorderAn implantable loop recorder (ILR), also called an insertable cardiac monitor (ICM), is a small device implanted just under the skin of the chest that continuously records heart rhythm for up to four or five years. It is used to investigate unexplained blackouts, palpitations, or suspected arrhythmias that have not been captured by shorter monitoring methods. How it works The ILR is about the size of a small USB stick. It is inserted under local anaesthesia in a minor procedure that(...)
• ImpulsivityA tendency to rush into something without reflecting or thinking first.
• ICPA tendency to rush into something without reflecting or thinking first.
• In-Hospital Cardiac ArrestAn in-hospital cardiac arrest (IHCA) is a cardiac arrest that occurs within a hospital, as distinct from an out-of-hospital cardiac arrest (OHCA), which occurs in the community. The distinction is clinically and epidemiologically important because the two settings differ in the speed of response, resources available, and outcomes achieved.In-hospital cardiac arrests benefit from the immediate availability of trained clinical staff, resuscitation equipment, and cardiac arrest teams.(...)
• IHCAAn in-hospital cardiac arrest (IHCA) is a cardiac arrest that occurs within a hospital, as distinct from an out-of-hospital cardiac arrest (OHCA), which occurs in the community. The distinction is clinically and epidemiologically important because the two settings differ in the speed of response, resources available, and outcomes achieved.In-hospital cardiac arrests benefit from the immediate availability of trained clinical staff, resuscitation equipment, and cardiac arrest teams.(...)
• Inappropriate ShockA shock delivered by an ICD (Implantable Cardioverter Defibrillator) when no life-threatening arrhythmia is actually present. Causes include the device misreading a fast but non-dangerous heart rhythm (such as sinus tachycardia), electrical noise from a damaged lead, or T-wave oversensing. Inappropriate shocks are physically and psychologically distressing and can lead to anxiety and reduced quality of life. If you receive a shock that you believe may have been inappropriate, contact your(...)
• Inappropriate Sinus TachycardiaInappropriate sinus tachycardia (IST) is a condition in which the sinus node (the heart's natural pacemaker) fires at an abnormally elevated rate without a physiological reason to explain it. It is defined as a persistent resting heart rate greater than 90 to 100 beats per minute, with an exaggerated and disproportionate increase in heart rate with minimal physical activity. Unlike sinus tachycardia caused by fever, anaemia, dehydration or exercise, IST has no identifiable(...)
• ISTInappropriate sinus tachycardia (IST) is a condition in which the sinus node (the heart's natural pacemaker) fires at an abnormally elevated rate without a physiological reason to explain it. It is defined as a persistent resting heart rate greater than 90 to 100 beats per minute, with an exaggerated and disproportionate increase in heart rate with minimal physical activity. Unlike sinus tachycardia caused by fever, anaemia, dehydration or exercise, IST has no identifiable(...)
• Incompetent ValveAlso called insufficiency; a valve that is not working properly, causing it to leak blood back in the wrong direction
• Induced ComaAn induced coma (also called therapeutic sedation or, in the post-cardiac arrest context, targeted temperature management with sedation) is a medically controlled state of unconsciousness. Sedative and anaesthetic medications are given intravenously to keep the patient deeply asleep, allowing the body to recover from the effects of cardiac arrest and enabling the critical care team to manage breathing via a mechanical ventilator and monitor organ function closely.After cardiac arrest,(...)
• Induced HypothermiaInduced hypothermia is called ‘cooling’. The person is cooled, using special blankets, to reduce the demands that their body is making on their brain. This is done where there is a risk that the person who had the cardiac arrest might suffer from damage to their brain, to give their body time to recover.
• InfarctAn infarct is an area of tissue that has died as a result of a permanent loss of its blood supply. When cells are deprived of oxygen for long enough that they cannot recover, they undergo irreversible death (necrosis), and the resulting dead tissue forms an infarct. In the heart, this is called a myocardial infarct (or myocardial infarction, commonly known as a heart attack); in the brain, it is called a cerebral infarct (stroke).Myocardial infarction occurs when a coronary artery is(...)
• InfarctionDeath of brain cells resulting from an interruption of their blood supply, as occurs in a stroke.
• InfectionInfection occurs when a pathogenic microorganism (a bacterium, virus, fungus, or parasite capable of causing disease) enters the body, multiplies within living tissue, and triggers an immune response. The body defends itself through inflammation (increased blood flow, immune cell recruitment, and chemical mediators) and other immune mechanisms designed to contain and eliminate the invading organism.In cardiac care and critical illness, infections are common and serious complications.(...)
• Infective EndocarditisInfective endocarditis (IE) is an infection of the endocardium (the inner lining of the heart, including the heart valves) caused by microorganisms, most commonly bacteria. It is the term used in modern clinical practice to describe this condition, distinguishing it from rare non-infective inflammatory forms. Bacterial endocarditis is the most common form, though fungal endocarditis occurs in immunocompromised patients.The infection typically occurs when microorganisms enter the(...)
• Inferior Vena CavaThe inferior vena cava (IVC) is the largest vein in the human body. It collects deoxygenated blood returning from the lower half of the body (below the diaphragm), including the legs, abdomen, and pelvic organs, and carries it to the right atrium of the heart.The IVC is formed by the joining of the two common iliac veins in the abdomen and ascends along the right side of the spine before passing through the diaphragm and entering the heart. It works in conjunction with the superior vena(...)
• IVCThe inferior vena cava (IVC) is the largest vein in the human body. It collects deoxygenated blood returning from the lower half of the body (below the diaphragm), including the legs, abdomen, and pelvic organs, and carries it to the right atrium of the heart.The IVC is formed by the joining of the two common iliac veins in the abdomen and ascends along the right side of the spine before passing through the diaphragm and entering the heart. It works in conjunction with the superior vena(...)
• InflammationInflammation is a complex biological response of living tissues to harmful stimuli such as infection, injury, or irritation. It is a protective mechanism designed to eliminate the cause of tissue injury, remove damaged cells and debris, and initiate repair. The cardinal signs of acute inflammation are redness, heat, swelling, pain, and loss of function.At the cellular level, inflammation involves the release of chemical mediators (cytokines, histamine, prostaglandins) that increase blood(...)
• Inherited Cardiac Condition ClinicAn inherited cardiac condition (ICC) clinic is a specialist NHS service that assesses, diagnoses, and manages patients with heart conditions that can run in families and increase the risk of serious arrhythmias, cardiomyopathy, or sudden cardiac death. ICC clinics also coordinate cascade screening of family members who may be at risk. What conditions are seen in ICC clinics ICC clinics specialise in conditions including:Hypertrophic cardiomyopathy (HCM) Dilated cardiomyopathy (DCM) with(...)
• Innocent MurmurAn innocent murmur (also called a functional or physiological murmur) is a heart murmur that is not caused by any structural heart disease or defect. Murmurs are sounds produced by turbulent blood flow through the heart or blood vessels; in an innocent murmur, this turbulence arises simply from the normal flow of blood and carries no clinical significance. Innocent murmurs are common in children and young adults, but can also be heard in adults, particularly in states of increased cardiac(...)
• InotropesInotropes are drugs that alter the strength (force) of the heart's contractions. Positive inotropes increase contractility, boosting cardiac output when the heart is failing to pump effectively. Negative inotropes reduce contractility and are used therapeutically in conditions where a less forceful contraction is beneficial, most notably beta-blockers and some calcium channel blockers used in heart failure and arrhythmia management.Positive inotropes are most commonly used in the(...)
• Integrated Care PathwayAn integrated care pathway (ICP, also called a clinical pathway or care pathway) is a structured, multidisciplinary plan that maps out the expected sequence of clinical care for a patient with a particular condition, from admission through to discharge and beyond. The pathway sets out what should happen at each stage, who is responsible, what the expected outcomes are, and how progress is documented. The aim is to bring together all the information from different members of the clinical(...)
• Intensive Care UnitAn intensive care unit (ICU), also called a critical care unit (CCU) or intensive therapy unit (ITU), is a specialist hospital ward providing continuous monitoring and advanced organ support for patients with life-threatening illness or injury. ICUs have higher staffing ratios than general wards (typically one nurse per one or two patients) and are equipped with monitoring equipment, mechanical ventilators, and the full range of critical care interventions.After cardiac arrest, most(...)
• ICUAn intensive care unit (ICU), also called a critical care unit (CCU) or intensive therapy unit (ITU), is a specialist hospital ward providing continuous monitoring and advanced organ support for patients with life-threatening illness or injury. ICUs have higher staffing ratios than general wards (typically one nurse per one or two patients) and are equipped with monitoring equipment, mechanical ventilators, and the full range of critical care interventions.After cardiac arrest, most(...)
• IntensivistAn intensivist is a physician who specialises in the care of critically ill patients in the intensive care unit (ICU). In the UK, intensivists are usually consultants who have trained in intensive care medicine, either as their primary specialty or dual-accredited alongside another specialty such as anaesthesia, respiratory medicine, renal medicine or cardiology. They lead the multidisciplinary ICU team and take overall responsibility for the management of each patient in the(...)
• Internal Mammary ArteryThe internal mammary artery (IMA), also called the internal thoracic artery, is a blood vessel that runs down the inside of the chest wall on each side of the sternum (breastbone). There are two: the left internal mammary artery (LIMA) and the right internal mammary artery (RIMA). These arteries are highly valued as bypass grafts in coronary artery bypass graft (CABG) surgery because of their exceptional long-term durability.In CABG surgery, the surgeon harvests one or both internal(...)
• Interrupted Aortic ArchInterrupted aortic arch (IAA) is a rare and severe congenital heart condition in which the aorta is completely discontinuous: there is a segment missing, so that the ascending and descending aorta are not connected. Blood flow to the lower body therefore depends entirely on the ductus arteriosus, a fetal blood vessel that normally closes within the first few days after birth. IAA is considered a more severe form of coarctation of the aorta. A large ventricular septal defect (VSD) is(...)
• Interventional CardiologyInterventional cardiology is a subspecialty of cardiology that treats heart conditions using catheter-based techniques performed in a cardiac catheterisation laboratory (cath lab). Instead of open surgery, interventional cardiologists use thin flexible tubes (catheters) inserted through blood vessels under local anaesthetic and X-ray guidance (fluoroscopy) to visualise, diagnose, and treat cardiac problems.Core procedures in interventional cardiology include coronary angiography(...)
• Interventional ProceduresInterventional cardiac procedures are minimally invasive techniques carried out in a cardiac catheterisation laboratory (cath lab) to diagnose or treat heart and vascular problems without the need for open surgery. They use catheters (thin flexible tubes) guided through blood vessels under X-ray imaging (fluoroscopy).The range of interventional procedures in adult cardiac care includes: coronary angiography (passing a catheter to the coronary arteries to inject contrast dye and visualise(...)
• Intracranial pressure monitorA monitoring device to determine the pressure within the brain. It consists of a small tube (catheter) in contact with the pulsing brain or the fluid cavity within it. ICP is measured by means of a metal screw or a plastic catheter connected to an electronic measuring device.
• IntramuscularInto the muscle.
• Intravascular EchocardiographyIntravascular echocardiography (ICE) is an imaging technique that incorporates a miniature ultrasound transducer on the tip of a catheter, which is inserted through a blood vessel and positioned inside the heart or major vessels. This provides high-resolution real-time images of cardiac structures from within. Unlike transthoracic or transoesophageal echocardiography, ICE provides a view from inside the heart itself without requiring an external operator or a probe in the oesophagus.ICE(...)
• Intravascular UltrasoundA combination of echocardiography and cardiac catheterisation. A miniature utrasound device on the tip of a catheter is used to generate images inside the heart and blood vessels.
• IntravenousIntravenous (IV) means 'into or within a vein'. The term is used to describe any substance, fluid or medication delivered directly into the bloodstream via a needle or catheter inserted into a vein, bypassing the digestive system and ensuring immediate availability to the circulation. IV administration provides the fastest route for drug delivery and is essential for emergency treatment where rapid effect is required.In the context of cardiac arrest and critical illness, IV access is one(...)
• Intravenous DripAn intravenous drip is an informal term for a continuous infusion of fluid, medication or nutrition delivered directly into a vein via a cannula (a short plastic tube inserted into a vein, usually in the arm or hand). The fluid flows from a bag or bottle, through a giving set (a thin plastic tube with a drip chamber), and into the vein at a controlled rate. The rate may be regulated by gravity with a manual clamp or, for more precise delivery, by an electronic infusion pump or syringe(...)
• IVAn intravenous drip is an informal term for a continuous infusion of fluid, medication or nutrition delivered directly into a vein via a cannula (a short plastic tube inserted into a vein, usually in the arm or hand). The fluid flows from a bag or bottle, through a giving set (a thin plastic tube with a drip chamber), and into the vein at a controlled rate. The rate may be regulated by gravity with a manual clamp or, for more precise delivery, by an electronic infusion pump or syringe(...)
• Introducer SheathAn introducer sheath (also called a vascular sheath or arterial sheath) is a short, hollow plastic tube inserted into a blood vessel at the start of a cardiac catheterisation or other interventional procedure. It acts as a conduit, maintaining reliable vascular access throughout the procedure and protecting the vessel wall as catheters and other instruments are exchanged. A haemostatic valve prevents blood from leaking back around the instruments.Sheaths are most commonly placed in the(...)
• Intrusive MemoriesIntrusive memories are unwanted, involuntary recollections of a traumatic event that enter a person's consciousness unexpectedly, often with vivid sensory detail and a sense that the event is happening again. They are one of the hallmark symptoms of post-traumatic stress disorder (PTSD) and are commonly reported by cardiac arrest survivors and their family members. What intrusive memories feel like Unlike ordinary memories that a person chooses to recall, intrusive memories feel as if they(...)
• Intrusive ThoughtsUnwanted, recurring, distressing thoughts, images, or impulses related to a traumatic event that enter consciousness involuntarily. Unlike flashbacks — which involve re-experiencing the event as if it is happening again — intrusive thoughts are recognised by the person as memories or mental events from the past, but they are unwanted and difficult to control or dismiss. Common examples for cardiac arrest co-survivors include repeatedly replaying the moment of collapse, thoughts about what(...)
• IntubationIntubation (more precisely, endotracheal intubation) is the procedure of placing a tube through the mouth or nose, past the vocal cords and into the trachea (windpipe) to secure and protect the airway and allow mechanical ventilation. The tube is called an endotracheal tube (ETT) and has an inflatable cuff near its tip that seals against the tracheal wall, preventing secretions from entering the lungs and ensuring that all ventilated air reaches the lungs rather than leaking around the(...)
• IschaemiaIschaemia is a reduction in blood flow to an organ or tissue that is sufficient to impair its function or cause damage. It results from obstruction or narrowing of the artery supplying that tissue, whether from atherosclerotic plaque, a clot, a spasm, or external compression. The reduced blood flow deprives cells of the oxygen and glucose they need for normal metabolism. If ischaemia is severe or prolonged, it progresses to infarction (cell death).Myocardial ischaemia, affecting the(...)
• Ischaemic Heart DiseaseIschaemic heart disease (IHD) is the umbrella term for heart conditions caused by a reduced blood supply to the heart muscle, resulting from narrowing or blockage of the coronary arteries. It is the most common form of heart disease and a leading cause of death worldwide. The terms coronary artery disease (CAD) and coronary heart disease (CHD) are used interchangeably with ischaemic heart disease, reflecting the same underlying process viewed from slightly different angles: CAD describes(...)
• Ischaemic StrokeAn ischaemic stroke occurs when a blood vessel supplying part of the brain is blocked by a clot or other obstruction, cutting off the blood and oxygen supply to an area of brain tissue. Within minutes, the affected brain cells begin to die, causing neurological deficits that reflect the function of the area damaged. Ischaemic strokes account for approximately 85 percent of all strokes; the remainder are haemorrhagic (caused by a burst blood vessel).Ischaemic stroke and cardiac arrest are(...)
• Isosorbide MononitrateA drug used to help prevent angina attacks and sometimes used in the treatment of heart failure.

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• JaundiceJaundice is the yellow or greenish discolouration of the skin, whites of the eyes (scleral icterus), and other tissues caused by elevated bilirubin in the blood. Bilirubin is a yellow pigment produced when the body breaks down the haemoglobin from old red blood cells, which are renewed approximately every 120 days. The liver normally processes bilirubin and excretes it via bile into the faeces; when this process is overwhelmed or disrupted, bilirubin accumulates in the tissues.Jaundice(...)
• Jaw ThrustThe jaw thrust is an airway opening manoeuvre used by first aiders and healthcare professionals when managing an unconscious patient, particularly where there is concern about a possible neck or spinal injury. Unlike the head-tilt chin-lift manoeuvre, the jaw thrust avoids extending the neck and is therefore preferred in situations where cervical spine injury cannot be ruled out.To perform a jaw thrust, the rescuer places their hands on either side of the patient's head, with fingers(...)
• JouleThe SI unit of work or energy, equal to the work done when the point of application of a force of 1 newton is displaced through a distance of 1 metre in the direction of the force.
• Jugular VeinsThe jugular veins are the major veins of the neck that return deoxygenated blood from the head and brain to the heart. There are two pairs: the internal jugular veins, which run deep in the neck alongside the carotid arteries and drain blood from the brain, face, and neck; and the external jugular veins, which are more superficial and can be visible on the surface of the neck.The internal jugular vein is clinically significant as a common site for central venous catheter insertion,(...)

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• KetoacidosisKetoacidosis is a serious metabolic condition in which the blood becomes abnormally acidic due to the accumulation of ketone bodies: acidic breakdown products produced when the body burns fat for energy instead of glucose. Ketoacidosis most commonly occurs in the context of diabetes (diabetic ketoacidosis, DKA), though it can also arise during prolonged starvation or in severe alcoholic liver disease.In diabetic ketoacidosis, insufficient insulin prevents cells from taking up glucose, so(...)

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• Laryngeal MaskAn airway tube with an elliptical inflatable cuff at one end for the insertion into the mouth of a patient requiring artificial ventilation.
• Lasting Power of AttorneyA lasting power of attorney (LPA) is a legal document in England and Wales that allows a person (the donor) to appoint one or more trusted individuals (attorneys) to make decisions on their behalf if they lose mental capacity in the future. An LPA must be set up and registered while the donor still has capacity; it cannot be arranged after capacity has been lost. Two types of LPA There are two separate LPAs, each covering a different area of life:Property and financial affairs LPA:(...)
• Lasting Power of Attorney — Health and WelfareA legal document that gives a named person (the attorney) the authority to make health and welfare decisions on behalf of someone else if they lose the mental capacity to make those decisions themselves. A Health and Welfare LPA can cover decisions including medical treatment, place of care, and — if specifically authorised — life-sustaining treatment. An LPA must be registered with the Office of the Public Guardian before it can be used. It can only be set up while the person still has(...)
• LPAA legal document that gives a named person (the attorney) the authority to make health and welfare decisions on behalf of someone else if they lose the mental capacity to make those decisions themselves. A Health and Welfare LPA can cover decisions including medical treatment, place of care, and — if specifically authorised — life-sustaining treatment. An LPA must be registered with the Office of the Public Guardian before it can be used. It can only be set up while the person still has(...)
• Lay ResponderA member of the public — with no formal medical role — who attempts to help someone in cardiac arrest before the arrival of emergency services. Also called a lay rescuer or bystander responder. Lay responders are a critical link in the chain of survival: early bystander CPR can double or triple survival rates from out-of-hospital cardiac arrest. Calling 999 and following dispatcher instructions allows anyone to perform effective CPR regardless of prior training. Many communities also have(...)
• Lead (Cardiac Device)In cardiology, a lead is a thin, insulated wire that transmits electrical signals between the heart and a cardiac implantable electronic device (CIED) such as a pacemaker, implantable cardioverter-defibrillator (ICD) or cardiac resynchronisation therapy device (CRT). Leads are distinct from electrodes: the electrode is the metal tip at the end of the lead that makes direct contact with the heart tissue, while the lead is the insulated cable connecting that electrode to the device body(...)
• Lead ExtractionLead extraction is a surgical procedure to remove one or more of the leads (wires) from an implanted cardiac device such as a pacemaker or ICD. Over time, leads can become embedded in the heart wall through fibrous tissue growth, making removal complex and requiring specialist expertise. Why leads may need to be extracted Common indications include:Infection: infection of a device or its leads is a serious complication typically requiring complete system removal, antibiotic treatment,(...)
• Leaky ValveSee 'Incompetent'.
• Left AtriumThe upper left-hand chamber of the heart. It receives oxygen-rich (red) blood from the lungs via the pulmonary veins, and then sends this blood to the left ventricle via the mitral valve.
• Left Bundle Branch BlockLeft bundle branch block (LBBB) is an abnormality of the heart's electrical conduction system in which the left bundle branch (the pathway carrying electrical impulses to the left ventricle) is blocked or non-functional. The left ventricle is forced to depolarise via a slower, indirect route, producing a distinctively wide QRS complex on the ECG.Unlike right bundle branch block, LBBB is rarely seen in a structurally normal heart and usually indicates significant underlying cardiac(...)
• LBBBLeft bundle branch block (LBBB) is an abnormality of the heart's electrical conduction system in which the left bundle branch (the pathway carrying electrical impulses to the left ventricle) is blocked or non-functional. The left ventricle is forced to depolarise via a slower, indirect route, producing a distinctively wide QRS complex on the ECG.Unlike right bundle branch block, LBBB is rarely seen in a structurally normal heart and usually indicates significant underlying cardiac(...)
• Left Cardiac Sympathetic DenervationLeft cardiac sympathetic denervation (LCSD) is a surgical procedure that reduces the sympathetic (adrenaline-driven) nerve supply to the heart by removing the lower portion of the left stellate ganglion and the first four thoracic ganglia on the left side. By reducing the heart's response to adrenaline and catecholamines, LCSD has a powerful antiarrhythmic effect, particularly in conditions where arrhythmias are triggered by adrenergic stimulation.LCSD is most commonly used in the(...)
• LCSDLeft cardiac sympathetic denervation (LCSD) is a surgical procedure that reduces the sympathetic (adrenaline-driven) nerve supply to the heart by removing the lower portion of the left stellate ganglion and the first four thoracic ganglia on the left side. By reducing the heart's response to adrenaline and catecholamines, LCSD has a powerful antiarrhythmic effect, particularly in conditions where arrhythmias are triggered by adrenergic stimulation.LCSD is most commonly used in the(...)
• Left VentricleThe left ventricle (LV) is the lower left chamber of the heart and the body's main pumping chamber. It receives oxygenated blood from the left atrium (via the mitral valve) and pumps it out through the aortic valve into the aorta, from where it is distributed to all organs and tissues of the body.The left ventricle has thick, muscular walls (typically 9 to 12mm in adults) to generate the high pressures needed to drive blood around the systemic circulation. In contrast, the right(...)
• Left Ventricular Assist DeviceA mechanical device that can be placed outside the body or implanted inside the body. An LVAD does not replace the heart—it “assists” or “helps” it pump oxygen-rich blood from the left ventricle to the rest of the body
• LVADA mechanical device that can be placed outside the body or implanted inside the body. An LVAD does not replace the heart—it “assists” or “helps” it pump oxygen-rich blood from the left ventricle to the rest of the body
• Left Ventricular DysfunctionDescribes the status of the left ventricle when it is not pumping or filling correctly.
• Left Ventricular FailureLeft ventricular failure (LVF) occurs when the left ventricle (the heart's main pumping chamber) can no longer maintain adequate output, causing blood to back up into the pulmonary circulation. Fluid leaks from the pulmonary capillaries into the lung tissue, producing pulmonary oedema.Symptoms include sudden or progressive breathlessness (particularly on lying flat, known as orthopnoea), a persistent cough (sometimes producing frothy or pink-tinged sputum), severe breathlessness at night(...)
• Left ventricular hypertrophy (LVH)When the left ventricle is too thick walled. Most commonly due to hypertension but also cab be due to aortic valve disease or cardiomyopathy.
• LVHWhen the left ventricle is too thick walled. Most commonly due to hypertension but also cab be due to aortic valve disease or cardiomyopathy.
• Left Ventricular Non-CompactionLeft Ventricular Non-Compaction (LVNC) is a cardiomyopathy in which the left ventricular muscle fails to develop properly, leaving deep trabeculations (spongy, irregular tissue) within the ventricular wall instead of the compact muscle seen in a normal heart. It can be inherited or develop later in life. LVNC can cause heart failure, blood clot formation within the heart, and life-threatening arrhythmias including ventricular tachycardia and ventricular fibrillation, making it a recognised(...)
• Left Ventricular NoncompactionLeft ventricular noncompaction (LVNC) is a cardiomyopathy caused by an arrest of normal myocardial development during fetal life. During normal heart development, the embryonic myocardium is a loose spongy network of muscle fibres that gradually compacts to form the smooth, dense ventricular wall. In LVNC, this compaction process is incomplete, leaving prominent trabeculae (muscular ridges) and deep recesses on the inner surface of the left ventricle. This gives the left ventricle a(...)
• LVNCLeft ventricular noncompaction (LVNC) is a cardiomyopathy caused by an arrest of normal myocardial development during fetal life. During normal heart development, the embryonic myocardium is a loose spongy network of muscle fibres that gradually compacts to form the smooth, dense ventricular wall. In LVNC, this compaction process is incomplete, leaving prominent trabeculae (muscular ridges) and deep recesses on the inner surface of the left ventricle. This gives the left ventricle a(...)
• LesionA lesion is a general medical term for any area of abnormal tissue or damage in the body, whether caused by injury, disease, or a pathological process. The word encompasses wounds, ulcers, tumours, areas of inflammation, scars, and structural abnormalities. In clinical use, the type of lesion is usually specified by the preceding description.In cardiovascular medicine, the term lesion is most commonly used to describe atherosclerotic lesions: areas of the arterial wall that have(...)
• Levels of careLevels of care is a framework used in NHS critical care to classify the level of monitoring and organ support a hospitalised patient requires, guiding decisions about where they should be cared for and how many nursing staff they need. The system standardises communication about patient dependency between clinical teams and between hospitals.The levels are: Level 0 (standard ward-based care with routine observations); Level 1 (ward-based care with additional monitoring such as continuous(...)
• Limbic systemA group of deep cortical structures connected to the hypothalamus, governing memory, emotions and basic drives, including sex drive.
• LipidA fatty substance that is insoluble (cannot be dissolved) in the blood.
• LipoproteinA lipoprotein is a particle that combines lipids (fats) with proteins, allowing fats to be transported in the water-based environment of the bloodstream. Fats are not water-soluble and cannot circulate freely in the blood, so the body packages them inside spherical particles where the water-repelling lipids are enclosed by a coat of proteins (called apolipoproteins) and phospholipids that are water-compatible. Different types of lipoprotein carry different proportions of fats, have(...)
• Locked-in SyndromeA condition in which the patient is awake and retains the ability to sense and perceive, but is unable to communicate except by limited eye movements. This is due to the motor nervous system being paralysed. It can sometimes be confused with persistent vegetative state.
• LocumA temporary health or social care professional.This person does not have a permanent contract with the Trust.
• Long QT SyndromeLong QT syndrome (LQTS) is an inherited or acquired heart rhythm disorder in which the electrical recovery phase of the heartbeat (measured as the QT interval on an ECG) is prolonged. This abnormal prolongation creates a window of vulnerability during which a dangerous arrhythmia called torsades de pointes can occur, potentially deteriorating into ventricular fibrillation and sudden cardiac arrest.Congenital LQTS is caused by mutations in genes encoding ion channels in heart muscle(...)
• LQTSLong QT syndrome (LQTS) is an inherited or acquired heart rhythm disorder in which the electrical recovery phase of the heartbeat (measured as the QT interval on an ECG) is prolonged. This abnormal prolongation creates a window of vulnerability during which a dangerous arrhythmia called torsades de pointes can occur, potentially deteriorating into ventricular fibrillation and sudden cardiac arrest.Congenital LQTS is caused by mutations in genes encoding ion channels in heart muscle(...)
• Low Density Lipoprotein (LDL)Low density lipoprotein (LDL) is the body's primary cholesterol-carrying molecule, transporting cholesterol from the liver through the bloodstream to cells throughout the body. High blood levels of LDL cholesterol promote the development of coronary artery disease by contributing to the build-up of fatty plaques inside artery walls (atherosclerosis), which is why LDL is often called 'bad cholesterol'.When LDL particles accumulate in the artery wall, they trigger an inflammatory response.(...)
• LDLLow density lipoprotein (LDL) is the body's primary cholesterol-carrying molecule, transporting cholesterol from the liver through the bloodstream to cells throughout the body. High blood levels of LDL cholesterol promote the development of coronary artery disease by contributing to the build-up of fatty plaques inside artery walls (atherosclerosis), which is why LDL is often called 'bad cholesterol'.When LDL particles accumulate in the artery wall, they trigger an inflammatory response.(...)
• LumenThe hollow area within a tube, such as a blood vessel.
• LungThe lungs are a pair of spongy, air-filled organs of respiration situated in the chest cavity on either side of the heart, enclosed by a thin membrane called the pleura. The right lung has three lobes and the left lung has two (the left being slightly smaller to accommodate the heart). Their primary function is gas exchange: oxygen from inhaled air passes into the bloodstream and carbon dioxide from the blood passes into the airways to be exhaled.Gas exchange occurs in approximately 300(...)

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• Magnetic Resonance ImagingMagnetic resonance imaging (MRI) is a medical imaging technique that uses strong magnetic fields and radio waves to produce detailed images of the body's internal structures. Hydrogen atoms in the body's water molecules align with the magnetic field; radio wave pulses briefly disturb this alignment, and the energy released as the atoms return to alignment is detected and converted into images. Unlike X-rays and CT scans, MRI uses no ionising radiation, making it suitable for repeated use(...)
• MRIMagnetic resonance imaging (MRI) is a medical imaging technique that uses strong magnetic fields and radio waves to produce detailed images of the body's internal structures. Hydrogen atoms in the body's water molecules align with the magnetic field; radio wave pulses briefly disturb this alignment, and the energy released as the atoms return to alignment is detected and converted into images. Unlike X-rays and CT scans, MRI uses no ionising radiation, making it suitable for repeated use(...)
• Maladie de RogerMaladie de Roger (Roger's disease) is a historical term for a small ventricular septal defect (VSD) that produces a disproportionately loud heart murmur but causes no haemodynamic disturbance and no symptoms. It was described by the French physician Henri-Louis Roger in 1879. The loud murmur arises because even a small hole between the ventricles generates significant turbulence as blood jets through the narrow defect during systole; the smaller the hole, the more turbulent and audible the(...)
• MannitolA solution which removes water from the brain by accelerating urinary excretion and thus reduces raised intracranial pressure.
• Marfan SyndromeAn inherited condition associated with lax tissues and affecting many parts of the body including the bones, eyes, heart and aorta.
• Maze SurgeryThe Maze procedure is a surgical operation used to treat chronic atrial fibrillation, typically when medications and catheter ablation have not worked or are unsuitable. During the procedure, a surgeon creates a precise pattern of scar tissue within the atrial muscle using incisions, radiofrequency energy, or cryotherapy. Scar tissue does not conduct electricity, so the resulting "maze" of scars forces electrical impulses to travel along a controlled pathway, restoring coordinated(...)
• Mechanical CPR DeviceA mechanical CPR device is an automated machine that delivers chest compressions during cardiac arrest, replacing or augmenting manual CPR. These devices deliver compressions at a consistent rate, depth, and recoil that is difficult to maintain over time with manual CPR, particularly during patient transport or prolonged resuscitation. Why mechanical CPR devices are used Manual chest compressions are physically demanding, and compression quality inevitably deteriorates over time as(...)
• Mechanical ValveAn artificial valve used to replace a diseased or defective valve, most often the aortic valve. Usually constructed of titanium and pyrolytic carbon. Patients with a mechanical valve require anticoagulation medication to prevent clots from forming on the valve.
• Median SternotomyAn incision in the centre of the chest, from the top to the bottom of the breastbone, used to gain access for most major forms of heart surgery.
• Medical Alert IdentificationMedical alert identification refers to wearable items such as bracelets, necklaces, or wallet cards that communicate a person's critical medical information to emergency responders and healthcare staff. In a medical emergency where the individual cannot speak for themselves, medical alert ID enables responders to act quickly and safely. For cardiac arrest survivors, medical alert ID is particularly important for those with an ICD or pacemaker, a channelopathy such as Long QT Syndrome,(...)
• Medical Emergency TeamA team usually consisting of a group of physicians, anaesthetists, and senior nurses, that can be summoned urgently to attend patients with deterioating medical conditions
• Memory Aids and Compensatory StrategiesMemory aids and compensatory strategies are practical tools and techniques used to manage memory difficulties, rather than relying solely on improving the underlying memory deficit. They are particularly relevant for cardiac arrest survivors who have experienced hypoxic brain injury resulting in working memory problems or broader cognitive impairment. Common memory aids include: diaries and structured planners, smartphone reminders and calendar alerts, notebooks kept in a consistent(...)
• Mental CapacityThe ability to make a specific decision at a specific time. Under the Mental Capacity Act 2005 (England and Wales), a person is assumed to have mental capacity unless there is evidence otherwise. Capacity is decision-specific — a person may have capacity to make some decisions but not others. If a clinical team believes a patient lacks capacity for a particular decision, they are required to act in that person's best interests, consulting family members and those close to the patient as(...)
• Mind (Mental Health Charity)Mind is a leading UK mental health charity that provides information, support, and advocacy for people experiencing mental health difficulties. Mind offers a range of resources including a detailed information website (mind.org.uk), a helpline (Mind Infoline: 0300 123 3393), local Mind services across England and Wales, and peer support programmes.For cardiac arrest survivors and their families, Mind's resources on anxiety, depression, PTSD, and adjustment to life-changing events can be(...)
• MindfulnessA practice of intentionally directing attention to the present moment — thoughts, feelings, and physical sensations — with curiosity and without judgement. Mindfulness-based approaches, including Mindfulness-Based Cognitive Therapy (MBCT) and Mindfulness-Based Stress Reduction (MBSR), have a growing evidence base for reducing anxiety, depression, and stress. For cardiac arrest survivors and ICD patients, mindfulness can be a useful tool for managing health anxiety, fear of recurrence, and(...)
• Minimally conscious stateA state of profoundly altered consciousness seen following a severe brain injury, in which there is some evidence of minimal awareness, although this is far removed from anything approaching normal appreciation of the surroundings or of what is happening.
• Mitral AtresiaComplete obstruction to the mitral valve.
• Mitral Regurgitation (reflux)Backward leak of circulating blood from left ventricle to left atrium due to failure of the mitral valve to close, or to prolapse or to perforation. The leak can be trivial, mild, moderate, or severe.
• Mitral StenosisMitral stenosis is a narrowing of the mitral valve, which controls blood flow from the left atrium to the left ventricle. When the valve opening is narrowed, blood flow from the lungs into the left heart is restricted, causing pressure to rise progressively in the left atrium and the pulmonary circulation.The most common cause worldwide is rheumatic heart disease, in which repeated episodes of rheumatic fever cause inflammation and progressive scarring of the valve leaflets, which(...)
• Mitral ValveThe mitral valve is the valve located at the junction between the left atrium and the left ventricle. It is a bicuspid valve (having two leaflets, or cusps) that opens during diastole to allow oxygenated blood to flow from the left atrium into the left ventricle, and closes during systole to prevent blood from flowing backwards into the atrium. It is named after the bishop's mitre, a ceremonial hat whose shape it resembles.The mitral valve apparatus consists of four components: the two(...)
• Mitral Valve ProlapseMitral valve prolapse (MVP) is a condition in which one or both leaflets of the mitral valve (the valve between the left atrium and left ventricle) are enlarged, thickened, or abnormally flexible, causing them to bulge (prolapse) backwards into the left atrium during ventricular contraction instead of closing cleanly. It is also called Barlow's disease, floppy mitral valve, or myxomatous mitral valve disease.MVP is the most common heart valve abnormality, affecting approximately 2 to 3%(...)
• Mitral Valve RegurgitationMitral valve regurgitation (MR) is a condition in which the mitral valve, which sits between the left atrium and the left ventricle, fails to close completely when the ventricle contracts. Blood leaks backwards (regurgitates) into the left atrium instead of being pumped forward into the aorta. This reduces the effective forward output of the heart and causes the left chambers to gradually enlarge and strain.MR can be primary (caused by disease of the valve itself) or secondary (caused by(...)
• Mitral Valve SurgeryThis can take the form of repair, splitting of the valve if narrowed (valvotomy), or valve replacement.
• mm HgmmHg (millimetres of mercury) is the unit used to measure blood pressure and other pressures within the cardiovascular system. It describes the height in millimetres to which the pressure would raise a column of liquid mercury in a manometer: a type of pressure measurement device historically used before modern electronic transducers became standard.At normal atmospheric conditions, a column of mercury 1 mm high corresponds to approximately 133 pascals of pressure. Blood pressure is(...)
• mmol/lUnits used for measuring the level of different lipids, and many substances including electrolytes. Usually refers to levels in the blood but measurements can be from other body fluids.
• Montreal Cognitive AssessmentThe Montreal Cognitive Assessment. A brief, validated cognitive screening tool used to detect mild cognitive impairment. It takes approximately 10 minutes to administer and assesses multiple cognitive domains including memory, attention, language, executive function, and orientation. Scores range from 0 to 30; a score of 26 or above is generally considered normal, though interpretation should account for education level and age. The MoCA is commonly used in post-cardiac arrest follow-up(...)
• MoCAThe Montreal Cognitive Assessment. A brief, validated cognitive screening tool used to detect mild cognitive impairment. It takes approximately 10 minutes to administer and assesses multiple cognitive domains including memory, attention, language, executive function, and orientation. Scores range from 0 to 30; a score of 26 or above is generally considered normal, though interpretation should account for education level and age. The MoCA is commonly used in post-cardiac arrest follow-up(...)
• Morphine, Oxygen, Nitrates, AspirinMONA is a mnemonic standing for Morphine, Oxygen, Nitrates, and Aspirin, historically used to summarise the immediate initial management of acute coronary syndrome (ACS), including unstable angina, NSTEMI, and STEMI.Aspirin (300mg, chewed) is the most evidence-based component and remains standard first-line treatment for all acute coronary syndromes: it inhibits platelet aggregation and reduces thrombus formation at the site of plaque rupture. Nitrates (sublingual or spray glyceryl(...)
• MONAMONA is a mnemonic standing for Morphine, Oxygen, Nitrates, and Aspirin, historically used to summarise the immediate initial management of acute coronary syndrome (ACS), including unstable angina, NSTEMI, and STEMI.Aspirin (300mg, chewed) is the most evidence-based component and remains standard first-line treatment for all acute coronary syndromes: it inhibits platelet aggregation and reduces thrombus formation at the site of plaque rupture. Nitrates (sublingual or spray glyceryl(...)
• MonitorIn the medical context, a monitor is an electronic device that continuously measures and displays one or more physiological parameters, allowing healthcare professionals to observe a patient's clinical status in real time. Monitors range from simple single-function devices (such as a pulse oximeter measuring oxygen saturation) to complex multi-parameter bedside units that simultaneously display ECG rhythm, heart rate, blood pressure, oxygen saturation, respiratory rate, temperature, and(...)
• Monophasic DefibrillatorA monophasic defibrillator is a type of defibrillator that delivers a high-energy electrical shock in a single direction through the heart, from one electrode pad to the other. The term 'monophasic' (meaning 'one phase' or 'one direction') distinguishes this older technology from biphasic defibrillators, which deliver a current that first flows in one direction and then reverses, flowing back in the opposite direction.Monophasic defibrillators were the standard technology for decades and(...)
• Monounsaturated FatsMonounsaturated fats are a type of dietary fat in which the fatty acid chains contain one double bond in their carbon structure. The term 'monounsaturated' refers to this single point of unsaturation. They are liquid at room temperature and tend to solidify when cooled.Monounsaturated fats are found in high concentrations in olive oil, rapeseed (canola) oil, avocados, and many nuts (particularly almonds, cashews, and peanuts). The Mediterranean diet, which is rich in olive oil and(...)
• Morbidity The fact of having a particular disease or illness. Having two diseases or illnesses simultaneously is known as comorbidity. Experiencing three or more at the same time is referred to as multi-morbidity.
• MorphineMorphine is a potent opioid analgesic derived from the opium poppy, used primarily to relieve moderate to severe pain. It acts on opioid receptors in the brain, spinal cord, and peripheral tissues, reducing pain perception and altering the emotional response to it. Morphine is one of the oldest medicines in use and remains a cornerstone of pain management, particularly in palliative care, post-operative care, and acute severe pain.In critical care following cardiac arrest, opioid(...)
• MortalityMortality refers to the occurrence of death within a defined population. In epidemiology and medical research, mortality is typically expressed as a rate (the number of deaths per 1,000 or 100,000 people in a given population over a defined time period, usually one year) or as a proportion (the percentage of people in a group who die from a particular condition). Mortality data are fundamental to understanding the burden of disease, evaluating interventions, and tracking public health(...)
• Motor cortexThe motor cortex is the region of the brain responsible for planning, initiating and controlling voluntary movement. It occupies a strip of the frontal lobe known as the precentral gyrus, running from the top of the brain down towards the ear on each side. Each hemisphere controls the opposite side of the body: the right motor cortex controls movement of the left arm, leg and face, and vice versa. The motor cortex works in close coordination with adjacent areas including the premotor and(...)
• Mouth to Mouth ResuscitationMouth-to-mouth resuscitation is a form of rescue breathing in which a rescuer breathes air directly into the mouth of a person who has stopped breathing, aiming to fill their lungs and maintain oxygenation until normal breathing resumes or medical help arrives. It is one component of cardiopulmonary resuscitation (CPR) alongside chest compressions.The technique involves pinching the patient's nostrils closed to prevent air escaping through the nose; tilting the head back and lifting the(...)
• MR-conditional Under specific conditions of use, safe in the MR environment.
• MR SafeMR Safe is a classification applied to an object, device, or implant that presents no known hazards in any magnetic resonance imaging (MRI) environment. The designation indicates that the item poses no magnetic attraction, heating risk, or other MRI-related hazard regardless of the field strength or scanning conditions.MR Safe is one of three standard MRI safety classifications. MR Safe items include non-metallic objects made of plastic, glass, or non-conductive composites that have no(...)
• MR UnsafeMR Unsafe is one of three internationally recognised safety labels applied to medical devices, implants, and equipment to describe their behaviour in a magnetic resonance imaging (MRI) environment. A device labelled MR Unsafe presents unacceptable risks to the patient or others when brought into or used within the MRI scanner room. These risks can include movement or heating of the device due to the strong magnetic field, which can cause serious injury or death.The three MRI safety(...)
• MUGA ScanA MUGA scan (Multiple Gated Acquisition scan) is a type of nuclear medicine imaging study used to assess the pumping function of the heart. It measures the ejection fraction of both the left and right ventricles and evaluates regional wall motion (how different areas of the heart muscle contract). Unlike echocardiography, which uses ultrasound to produce structural images, a MUGA scan shows functional information about the heart's performance as a pumping system.During the procedure, a(...)
• MurmurNoises superimposed on normal heart sounds. They are caused by congenital defects or damaged heart valves that do not close properly and allow blood to leak back into the chamber from which it has come.
• MyelinA fatty insulating sheath, which surrounds nerve axons and improves the efficiency of transmission of the electrical nerve impulses along them.
• Myocardial InfarctionA heart attack. The damage or death of an area of the heart muscle (myocardium) resulting from a blocked blood supply to the area. The affected tissue dies, injuring the heart. Symptoms include prolonged, intensive chest pain and a decrease in blood pressure that often causes shock
• MIA heart attack. The damage or death of an area of the heart muscle (myocardium) resulting from a blocked blood supply to the area. The affected tissue dies, injuring the heart. Symptoms include prolonged, intensive chest pain and a decrease in blood pressure that often causes shock
• Myocardial IschaemiaMyocardial ischaemia occurs when the blood supply to part of the heart muscle (myocardium) is insufficient to meet its oxygen demands. The most common cause is narrowing or blockage of a coronary artery due to coronary artery disease, where the build-up of atherosclerotic plaque restricts blood flow.Ischaemia can be stable or unstable. Stable ischaemia typically occurs during exertion or emotional stress, when the heart's demand for oxygen increases but cannot be met through narrowed(...)
• Myocardial Perfusion ScanA method to detect and quantify myocardial ischaemia. An intravenously injected radionuclide that is taken up by normal heart muscle can be imaged using a gamma camera.
• Myocardial StunningMyocardial stunning is the temporary loss of contractile function of heart muscle cells following a brief period of severe ischaemia (reduced blood flow), despite the restoration of normal blood supply. The affected heart muscle is still alive (it has not undergone irreversible necrosis), but it takes hours to days to recover its normal function after blood flow is restored. The key feature distinguishing stunning from infarction is reversibility: if blood supply is maintained, the stunned(...)
• MyocarditisMyocarditis is inflammation of the heart muscle (myocardium). It can weaken the heart's pumping function, disrupt its electrical system, and in some cases cause sudden cardiac arrest. It is an important and sometimes underdiagnosed cause of cardiac arrest, particularly in younger people who appear otherwise healthy.**Causes**The most common cause is viral infection, particularly enteroviruses (such as Coxsackievirus B), adenovirus, and parvovirus B19. Other causes include autoimmune(...)
• MyocardiumThe muscular wall of the heart. It contracts to pump blood out of the heart and then relaxes as the heart refills with returning blood.
• MyoclonusSudden, shock-like muscle twitches or jerks, seen in various brain disorders and quite common following severe cerebral anoxia.
• Myxomatous DegenerationMyxomatous degeneration is a connective tissue disorder in which the structural proteins of heart valve tissue (primarily collagen and elastin) weaken and become replaced by a softer, gel-like (myxomatous) material. This causes the valve to lose its normal stiffness and shape, making it floppy and prone to malfunction.The condition most commonly affects the mitral valve, producing mitral valve prolapse (MVP), in which one or both leaflets of the mitral valve bulge back into the left(...)

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• Nasal SpecsThis is a way of giving oxygen through tubes that fit into the nostrils.
• Nasogastric tubeA nasogastric (NG) tube is a thin, flexible plastic tube inserted through one nostril, down the throat and oesophagus, and into the stomach. The tube is passed at the bedside by trained nurses or doctors, usually without anaesthetic. Its position in the stomach is confirmed before use by aspiration of gastric fluid and pH testing, or by chest X-ray.NG tubes serve two main purposes: drainage and feeding. For drainage, the tube removes fluid and gas from the stomach when it is not emptying(...)
• National Early Warning ScoreThe National Early Warning Score (NEWS2) is a standardised clinical tool used in NHS hospitals to detect and respond to deterioration in patients' clinical condition, and to identify those at risk of cardiac arrest, sepsis, or other life-threatening deterioration. The current version, NEWS2, replaced the original NEWS system in 2017 and includes a specific track to detect the risk of type 2 respiratory failure in patients with conditions such as COPD.NEWS2 scores six physiological(...)
• NEWSThe National Early Warning Score (NEWS2) is a standardised clinical tool used in NHS hospitals to detect and respond to deterioration in patients' clinical condition, and to identify those at risk of cardiac arrest, sepsis, or other life-threatening deterioration. The current version, NEWS2, replaced the original NEWS system in 2017 and includes a specific track to detect the risk of type 2 respiratory failure in patients with conditions such as COPD.NEWS2 scores six physiological(...)
• Near-Death ExperienceA near-death experience (NDE) is a range of subjective experiences reported by some people following a close encounter with death, including cardiac arrest. These experiences can include feelings of profound peace or wellbeing, a sense of leaving the body (out-of-body experience), moving through a tunnel towards light, encountering deceased relatives, a life review, and a sense of returning to the body. NDEs are reported across cultures and are not explained by religious belief alone. How(...)
• NebuliserThis makes medicine into an aerosol and helps loosen thick phlegm and open the airways.
• NecrosisNecrosis is the premature death of cells or tissue caused by external injury, disease, or loss of blood supply. Unlike apoptosis (programmed cell death), necrosis is an uncontrolled process triggered by a harmful external event and typically causes inflammation as the immune system responds to the dying tissue.In cardiac medicine, necrosis most commonly refers to myocardial necrosis (the death of heart muscle cells) caused by prolonged interruption of blood supply during a heart attack(...)
• Neuro-transmittersChemicals made in the nervous system that serve as messengers, aiding or interfering with the functions of the nerve cells.
• Neurocardiogenic SyncopeA recurrent loss of consciouness due to a drop in blood pressure mediated by vasodilatation, bradycardia or a combination of both. They ressemble a simple faint but can be very disabling because they are more frequent and severe.
• Neurogenic diabetes insipidusA condition which causes thirst and excessive production of dilute urine due to the pituitary gland not producing enough of the hormone vasopressin (anti-diuretic hormone).
• NeuronA nerve cell.
• NeuroplasticityNeuroplasticity is the brain's ability to reorganise itself by forming new connections between neurons in response to learning, experience, injury, or recovery. It is the biological foundation for cognitive rehabilitation after cardiac arrest and other forms of brain injury. Why it matters for cardiac arrest survivors Many survivors experience some degree of hypoxic brain injury following cardiac arrest. In the past, brain damage was thought to be permanent and fixed. It is now understood(...)
• Neuropsychological AssessmentA comprehensive assessment of cognitive functioning carried out by a neuropsychologist or clinical psychologist. Unlike brief screening tools such as the MoCA, a full neuropsychological assessment uses a battery of standardised tests to measure specific cognitive domains in detail — including memory, attention, processing speed, executive function, language, and visuospatial ability. Results are compared against population norms and can inform diagnosis, rehabilitation planning, and(...)
• NeurosisNeurosis is an older psychiatric term that was used to describe a range of mental health conditions characterised by excessive anxiety, emotional distress, or dysfunctional behaviours, without loss of contact with reality (as distinct from psychosis). The category included what are now separately classified as anxiety disorders, phobias, obsessive-compulsive disorder (OCD), and certain depressive and somatic conditions. The term neurosis was removed from the main classification systems(...)
• Next of KinThe person identified as closest to a patient — typically a spouse, civil partner, parent, or adult child — who is the primary point of contact for the clinical team when the patient is unable to speak for themselves. Next of kin has no formal legal standing in English law: being listed as next of kin does not automatically give someone the legal right to make medical decisions on a patient's behalf. That right comes from a Health and Welfare Lasting Power of Attorney (LPA) or, in some(...)
• NOKThe person identified as closest to a patient — typically a spouse, civil partner, parent, or adult child — who is the primary point of contact for the clinical team when the patient is unable to speak for themselves. Next of kin has no formal legal standing in English law: being listed as next of kin does not automatically give someone the legal right to make medical decisions on a patient's behalf. That right comes from a Health and Welfare Lasting Power of Attorney (LPA) or, in some(...)
• NicardipineCalcium - channel blocker used to prevent angina and treat hypertension.
• NicotineA chemical found in tobacco smoke, probably harmless, alongside many harmful chemicals in the smoke that cause vascular disease and cancers.
• Nicotine Replacement TherapyNicotine replacement therapy (NRT) refers to a range of products that deliver nicotine to the body without the harmful combustion products of tobacco smoke, helping people manage withdrawal symptoms and cravings while stopping smoking. Available forms include patches, gum, lozenges, inhalators, and nasal sprays.Stopping smoking is one of the most powerful actions a person can take to reduce cardiovascular risk. Smoking damages the lining of blood vessels (endothelium), promotes(...)
• NifedipineNifedipine is a calcium channel blocker (CCB) used primarily to treat high blood pressure (hypertension), angina, and Raynaud's phenomenon. It works by relaxing the smooth muscle in blood vessel walls, causing them to widen (vasodilate) and reducing the resistance the heart pumps against.Calcium channel blockers are one of the main classes of antihypertensive medication recommended by NICE for initial blood pressure treatment, particularly in people of African or Caribbean origin and(...)
• NightmaresDistressing dreams related to a traumatic experience, often vivid and realistic, that can disrupt sleep and leave the person feeling frightened or distressed on waking. Nightmares are a recognised symptom of PTSD and acute stress reactions and are common in both survivors and co-survivors following cardiac arrest. For survivors, nightmares may incorporate distorted versions of the ICU experience, of being unable to breathe, or of medical procedures. For co-survivors, they often replay the(...)
• Glyceryl Trinitrate (GTN)Glyceryl trinitrate (GTN), also known as nitroglycerin, is a medication that causes rapid relaxation and widening (dilation) of blood vessels, including the coronary arteries. It is one of the most important drugs for the immediate treatment of angina (cardiac chest pain).GTN is most commonly used as a sublingual (under the tongue) spray or tablet that is absorbed quickly through the mouth lining, producing an effect within 1 to 3 minutes. This rapid action makes it ideal for relieving(...)
• Non-ST-Segment-Elevation Myocardial InfarctionA non-ST-elevation myocardial infarction (NSTEMI) is one of the two main types of heart attack, distinguished from a STEMI by the absence of persistent ST-segment elevation on the electrocardiogram. Both involve death of heart muscle confirmed by a rise in blood troponin levels, but the underlying coronary artery blockage is typically incomplete in NSTEMI, allowing some residual blood flow to continue through the affected artery.In a STEMI, a coronary artery is completely occluded,(...)
• NSTEMIA non-ST-elevation myocardial infarction (NSTEMI) is one of the two main types of heart attack, distinguished from a STEMI by the absence of persistent ST-segment elevation on the electrocardiogram. Both involve death of heart muscle confirmed by a rise in blood troponin levels, but the underlying coronary artery blockage is typically incomplete in NSTEMI, allowing some residual blood flow to continue through the affected artery.In a STEMI, a coronary artery is completely occluded,(...)
• Non Sustained Ventricular TachycardiaAn abnormally fast heartbeat caused by irregular electrical impulses that originate in the lower chambers of the heart (the ventricles). Ventricular tachycardia that stops by itself within 30 seconds is called non-sustained ventricular tachycardia (NSVT). Any ventricular tachycardia is considered a potentially dangerous cardiac arrhythmia. However, because NSVT does not persist, it is substantially less dangerous than a sustained ventricular tachycardia (SVT) and may turn out to be(...)
• NSVTAn abnormally fast heartbeat caused by irregular electrical impulses that originate in the lower chambers of the heart (the ventricles). Ventricular tachycardia that stops by itself within 30 seconds is called non-sustained ventricular tachycardia (NSVT). Any ventricular tachycardia is considered a potentially dangerous cardiac arrhythmia. However, because NSVT does not persist, it is substantially less dangerous than a sustained ventricular tachycardia (SVT) and may turn out to be(...)
• Noninvasive ProceduresAny diagnostic or treatment procedure in which no instrument enters the body
• NT-proBNPN-terminal pro-B-type natriuretic peptide (NT-proBNP) is a blood biomarker released by the heart when it is under increased strain or pressure. Elevated levels indicate the presence of heart failure or worsening cardiac function. NT-proBNP is used to diagnose heart failure, guide treatment decisions, and monitor a patient's response to therapy over time. A normal level makes significant heart failure unlikely, while persistently elevated levels may prompt intensification of(...)
• Nuclear CardiologyThe study and dianosis of heart disease by the intravenous injection of different types of radionuclide. The radionuclide emits gamma rays, enabling a gamma camera and computer to form an image of the heart.
• Nuclear Medicine ScanA nuclear medicine scan is a diagnostic imaging technique in which a small amount of a radioactive substance (radioisotope or radiotracer) is injected into a vein or inhaled, and a specialised camera detects the radiation it emits to produce images of organ function and blood flow. Unlike structural imaging (CT or MRI), nuclear medicine scans show how organs are working at a physiological level.In cardiac care, nuclear medicine scanning is used primarily for myocardial perfusion imaging,(...)

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• ObesityThe condition of being significantly overweight. It usually applies when a person is 30% or more over ideal body weight. Obesity puts a strain on the heart and can increase the risk of developing high blood pressure and diabetes.
• Occipital lobesArea at the back of the cerebral hemispheres, containing the main visual centres.
• OccludedAn opening, orifice, or passage that is completely blocked. For cardiology this usually relates to a blocked vessel, artery more often than a vein.
• Occluded ArteryAn occluded artery is a blood vessel in which blood flow has been partially or completely blocked. The term 'occlusion' means blockage or obstruction. In cardiovascular medicine, arterial occlusion most commonly refers to blockage of the coronary arteries (causing heart attack or myocardial ischaemia) or blockage of arteries supplying the brain (causing stroke), though occlusion can occur in any artery.Arterial occlusions arise through several mechanisms. Atherothrombosis is the most(...)
• Occupational Health ServiceAn Occupational Health Service (OHS) is a specialist medical service that advises on the relationship between work and health. Occupational Health practitioners assess whether an employee is fit to work, recommend workplace adjustments, and support safe return to work after serious illness or injury. For cardiac arrest survivors, Occupational Health can be a key resource during return to work planning. An Occupational Health assessment typically covers: current functional capacity and(...)
• Occupational TherapistOccupational therapists use purposeful activities to treat people with physical and/or mental health problems. They work as part of a team to identify problems caused by people’s conditions and find ways of coping with these to encourage independence and a better quality of life.
• Occupational TherapyOccupational therapy uses goal-directed activities, appropriate to a person’s age and social role, to restore, develop or maintain the ability for independent living
• OedemaOedema is the abnormal accumulation of fluid in body tissues, causing swelling. It occurs when fluid leaks from blood vessels into surrounding tissues at a greater rate than the lymphatic system can drain it away. Oedema can be localised (affecting one area) or generalised (affecting the whole body).In cardiac conditions, oedema is most commonly a sign of heart failure. When the heart pumps ineffectively, fluid backs up in the venous system. In left heart failure, fluid accumulates in(...)
• Off Pump CABGCoronary Artery Bypass Graft performed on a beating heart, ie without using cardiopulmonary bypass (the pump refers to a heart-lung machine)
• Omega 3A type of fatty acid found in fish oils. Eating these can help prevent blood clotting and help reduce triglyceride levels.
• Open head injuryAn open head injury (also called a penetrating head injury) is one in which the scalp and skull are breached and brain tissue is exposed or penetrated, typically by a foreign object such as a fragment of bone, a projectile or a sharp implement. It is classified as a form of traumatic brain injury (TBI). The injury causes focal damage along the path of penetration, and the risk of infection, including meningitis and cerebral abscess, is significant because the protective barrier between the(...)
• Open Heart OperationAn open heart operation is a cardiac surgical procedure in which the chest is opened (via a sternotomy: a vertical cut through the sternum or breastbone) to access the heart directly and perform surgery on its internal structures. The term 'open' refers to the surgical access to the heart, not necessarily to the heart always being entered, though many procedures (such as valve replacement) do require opening the heart chambers. Open heart surgery is performed under general anaesthesia and(...)
• Open Heart SurgeryOpen heart surgery is a cardiac surgical procedure in which the chest is opened and the heart is operated on while the patient is supported on a heart-lung (cardiopulmonary bypass) machine, which takes over the functions of the heart and lungs during the procedure. The heart is typically stopped to allow the surgeon to work inside it.Open heart surgery is used for coronary artery bypass grafting (CABG) to bypass blocked coronary arteries, valve repair or replacement, correction of(...)
• OrganAn organ is a discrete anatomical structure composed of two or more different tissue types that together form a structural and functional unit, performing one or more specific physiological roles. Examples include the heart, lungs, liver, kidneys, brain, stomach, and intestines. Most organs are part of larger systems (such as the cardiovascular system or respiratory system) that work together to maintain the body's functions.The heart is the most directly relevant organ in the context of(...)
• Organ DonationThe process of donating organs and/or tissue after death to benefit others who need a transplant. In the UK, adults are considered to have agreed to donate their organs unless they have opted out or are in an excluded group (the opt-out system introduced in England in 2020). Families are always consulted and their views are taken into account, even under opt-out. Organ donation is typically discussed by a specialist nurse for organ donation (SNOD), who works alongside the ICU team and is(...)
• Out-of-Body ExperienceAn out-of-body experience (OBE) is a perceptual phenomenon in which a person has a vivid sense of leaving their physical body and observing themselves from an external vantage point. People who report OBEs often describe seeing themselves from above, watching events around their body unfold as if from a position outside it.OBEs are reported by a significant proportion of cardiac arrest survivors, often forming part of a broader near-death experience (NDE). NDEs may also include(...)
• Out of Hospital Cardiac ArrestOut-of-hospital cardiac arrest (OHCA) describes a cardiac arrest that occurs outside a hospital setting, such as at home, at work, in a public place, or on the street. It is distinguished from in-hospital cardiac arrest (IHCA), where medical staff and resuscitation equipment are immediately available.OHCA accounts for the vast majority of cardiac arrests in the UK. Around 30,000 OHCA attempts are made by ambulance services in the UK each year. Survival to hospital discharge is around 8(...)
• OHCAOut-of-hospital cardiac arrest (OHCA) describes a cardiac arrest that occurs outside a hospital setting, such as at home, at work, in a public place, or on the street. It is distinguished from in-hospital cardiac arrest (IHCA), where medical staff and resuscitation equipment are immediately available.OHCA accounts for the vast majority of cardiac arrests in the UK. Around 30,000 OHCA attempts are made by ambulance services in the UK each year. Survival to hospital discharge is around 8(...)
• OximetryA method of measuring the oxygen content of blood.
• Oxygen SaturationThe extent to which the haemoglobin is saturated with oxygen. (Haemoglobin is a protein in the red blood cells that binds with oxygen and carries it to the organs and tissues of the body.)

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• PacemakerA pacemaker is a small electronic device implanted under the skin, usually below the collarbone, that monitors the heart's electrical activity and delivers electrical impulses to maintain a safe heart rate when the heart beats too slowly (bradycardia) or pauses. The device consists of a pulse generator (the device body, containing the battery and electronics) and one or more leads (thin wires) that pass through a vein into the heart. If the heart rate falls below a programmed threshold,(...)
• Pacing LeadThe means to conduct the electrical signals to and from an an electronic device (pacemaker, ICD or CRT). Temporary pacing is sometimes required and this uses an external pacing lead and pacemaker generator box.
• Paediatric Advanced Life SupportThis is advanced life support for use in severe medical emergencies in children.
• PALSThis is advanced life support for use in severe medical emergencies in children.
• Paediatric CardiologistA paediatric cardiologist is a consultant physician who specialises in diagnosing and managing heart conditions in children, from newborns through to teenagers and young adults with congenital heart disease. They work in specialist centres and are involved in the assessment and follow-up of inherited and structural heart conditions that can affect cardiac arrest risk in young people.In the context of sudden cardiac arrest, paediatric cardiologists play an important role in several areas.(...)
• PalpitationAn uncomfortable feeling within the chest caused by an irregular heartbeat.
• PalpitationsPalpitations are an awareness of one's own heartbeat that is noticeable and often uncomfortable. People describe palpitations in different ways: a fluttering or flipping sensation in the chest, a racing or pounding heartbeat, a feeling of the heart skipping or pausing, or an unusually forceful beat. Palpitations may be felt in the chest, throat, or neck, and can last seconds or minutes. Palpitations are extremely common in the general population and have many causes, most of which are(...)
• Patient Advice and Liaison ServicePatient Advice and Liaison Service. A free, confidential service available in every NHS Trust in England that helps patients, families, and carers with concerns, questions, or complaints about NHS care. PALS can help you understand what is happening with a loved one's treatment, navigate the hospital system, resolve concerns informally before they become formal complaints, and signpost to further support. For co-survivors trying to understand a complex ICU situation or feeling that(...)
• PALSPatient Advice and Liaison Service. A free, confidential service available in every NHS Trust in England that helps patients, families, and carers with concerns, questions, or complaints about NHS care. PALS can help you understand what is happening with a loved one's treatment, navigate the hospital system, resolve concerns informally before they become formal complaints, and signpost to further support. For co-survivors trying to understand a complex ICU situation or feeling that(...)
• PancreasThe pancreas is a glandular organ located behind the stomach in the upper abdomen. It has two main functions: an exocrine function (producing digestive enzymes released into the small intestine to aid digestion of proteins, fats, and carbohydrates) and an endocrine function (producing hormones that regulate blood sugar levels, secreted directly into the bloodstream).The endocrine portion of the pancreas consists of clusters of cells called the islets of Langerhans. Beta cells produce(...)
• PancreatitisPancreatitis is inflammation of the pancreas, the glandular organ in the upper abdomen responsible for producing digestive enzymes and hormones including insulin. The inflammation causes the pancreas's own digestive enzymes to activate prematurely within the gland, damaging pancreatic tissue and triggering a systemic inflammatory response.Acute pancreatitis presents with severe upper abdominal pain (often radiating to the back), nausea, vomiting, and elevated blood levels of pancreatic(...)
• ParalysisLoss of the ability to move muscles and feel in part of the body or the whole body. Paralysis may be temporary or permanent
• Parietal lobesThe part of each cerebral hemisphere primarily concerned with the perception and interpretation of sensation and movement.
• Parkinson's diseaseA slowly progressive brain disease involving the basal ganglia and causing reduced movement, rigidity and tremor. Damage to the basal ganglia - which can occur in cerebral anoxia - may produce symptoms resembling spontaneously occurring Parkinson's disease.
• Paroxysmal Supraventricular TachycardiaParoxysmal supraventricular tachycardia (PSVT) is a type of rapid heart rhythm that starts and stops suddenly (paroxysmal), originates above the ventricles (supraventricular), and produces a fast regular heart rate, typically between 150 and 250 beats per minute. It is one of the most common arrhythmias seen in clinical practice and can affect people of all ages, including those with structurally normal hearts.PSVT is caused by an abnormal electrical circuit or pathway above the level of(...)
• PSVTParoxysmal supraventricular tachycardia (PSVT) is a type of rapid heart rhythm that starts and stops suddenly (paroxysmal), originates above the ventricles (supraventricular), and produces a fast regular heart rate, typically between 150 and 250 beats per minute. It is one of the most common arrhythmias seen in clinical practice and can affect people of all ages, including those with structurally normal hearts.PSVT is caused by an abnormal electrical circuit or pathway above the level of(...)
• Passive SmokingWhere non smokers inhale other people’s smoke. Causes the same ill health effects as low cigarette smoking.
• PatentPatent is a medical adjective meaning 'open' or 'unobstructed'. When applied to a vessel, duct, or anatomical opening, it means the structure is not blocked or closed and is allowing normal passage of blood or other fluids. The term is the opposite of 'occluded' (blocked) or 'stenosed' (narrowed).In cardiology, the most common use of the term is in patent ductus arteriosus (PDA), where the ductus arteriosus (a fetal vessel connecting the aorta and pulmonary artery) remains open after(...)
• Patent Ductus ArteriosusPatent ductus arteriosus (PDA) is a congenital condition in which the ductus arteriosus, a normal fetal blood vessel connecting the aorta and the pulmonary artery, fails to close after birth. During fetal development, the ductus arteriosus diverts blood away from the non-functioning lungs. Normally, the rise in oxygen levels at birth triggers closure of the ductus within the first days to weeks of life. When it remains open (patent), it creates an abnormal connection between the two great(...)
• PDAPatent ductus arteriosus (PDA) is a congenital condition in which the ductus arteriosus, a normal fetal blood vessel connecting the aorta and the pulmonary artery, fails to close after birth. During fetal development, the ductus arteriosus diverts blood away from the non-functioning lungs. Normally, the rise in oxygen levels at birth triggers closure of the ductus within the first days to weeks of life. When it remains open (patent), it creates an abnormal connection between the two great(...)
• Patent Foramen OvaleA patent foramen ovale (PFO) is a small opening between the right and left atria that persists from fetal circulation into adult life. During fetal development, the foramen ovale allows blood to bypass the non-functioning lungs. Normally, this opening seals when the lungs expand at birth and pressure in the left atrium rises. In approximately 25 to 30% of adults, the foramen ovale fails to seal completely, leaving a small flap-like passage.A PFO is usually of no clinical significance in(...)
• PFOA patent foramen ovale (PFO) is a small opening between the right and left atria that persists from fetal circulation into adult life. During fetal development, the foramen ovale allows blood to bypass the non-functioning lungs. Normally, this opening seals when the lungs expand at birth and pressure in the left atrium rises. In approximately 25 to 30% of adults, the foramen ovale fails to seal completely, leaving a small flap-like passage.A PFO is usually of no clinical significance in(...)
• Peer SupportPeer support is a form of mutual aid in which people draw on their own lived experience to support others facing similar challenges. Unlike professional therapy or counselling, peer support is based on equality: the person offering support has personal experience of the situation and shares it without directing or prescribing what the other person should do. It creates a space where people feel genuinely understood rather than simply advised.For survivors of sudden cardiac arrest and(...)
• Peer SupportPeer support is the process through which people with shared experiences provide emotional, practical, and informational support to one another. In the context of cardiac arrest survivorship, peer support connects survivors and their families with others who have been through similar experiences, offering a unique form of understanding and validation that is difficult to replicate in a clinical setting. Why peer support matters after cardiac arrest Cardiac arrest is a rare and often(...)
• PercutaneousPercutaneous is a medical adjective meaning 'through the skin'. It describes any procedure, drug delivery route, or access method that involves passing through the skin (via a needle, catheter, or wire) rather than requiring an open surgical incision. Percutaneous procedures are generally less invasive than their open surgical equivalents, typically resulting in shorter recovery times and lower complication rates.In cardiology, 'percutaneous' most commonly appears in the terms(...)
• Percutaneous Coronary InterventionPercutaneous coronary intervention (PCI) is a minimally invasive catheter-based procedure used to open narrowed or blocked coronary arteries. A thin flexible tube (catheter) is inserted through a small puncture, usually in the wrist (radial access) or groin (femoral access), and guided to the affected coronary artery under X-ray guidance. The most common form is balloon angioplasty combined with stent insertion, where a mesh tube is deployed to hold the artery open.PCI is performed in a(...)
• PCIPercutaneous coronary intervention (PCI) is a minimally invasive catheter-based procedure used to open narrowed or blocked coronary arteries. A thin flexible tube (catheter) is inserted through a small puncture, usually in the wrist (radial access) or groin (femoral access), and guided to the affected coronary artery under X-ray guidance. The most common form is balloon angioplasty combined with stent insertion, where a mesh tube is deployed to hold the artery open.PCI is performed in a(...)
• Percutaneous Transluminal Coronary AngioplastySee angioplasty
• PTCASee angioplasty
• Peri-Arrest PeriodThe peri-arrest period refers to the critical window of time immediately surrounding a full cardiac arrest: the period just before arrest (when a patient's condition is deteriorating towards it) and the period just after successful resuscitation (when the patient remains highly unstable and at risk of re-arrest). In both cases the patient's physiological state is precarious, and medical teams apply intensive monitoring and intervention to prevent further deterioration.Pre-arrest(...)
• Pericardial EffusionA collection of fluid in the pericardium (sac around the heart). Such a collection, if it is large, may lead to a buildup of pressure on the heart. This often results in deterioration in its function, leading to low blood pressure or heart failure.
• PericardiocentesisA diagnostic procedure that uses a needle to withdraw fluid from the sac or membrane surrounding the heart (pericardium).
• PericardiorrhaphyPericardiorrhaphy is the surgical repair of wounds to the pericardium (the fibrous sac surrounding the heart) following trauma, injury, or iatrogenic laceration. The name combines 'pericardio' (relating to the pericardium) with 'rrhaphy' (the surgical suturing or repair of a structure).The most common indication is penetrating cardiac trauma: wounds caused by stabbing, gunshot injury, or sharp foreign body impalement can lacerate the pericardium and, frequently, the underlying heart(...)
• PericardiostomyPericardiostomy is a surgical procedure in which the pericardium (the membranous sac surrounding the heart) is incised and a drainage tube is inserted to allow continuous or intermittent drainage of fluid from the pericardial space. It is used when a significant accumulation of fluid (pericardial effusion) is causing symptoms or haemodynamic compromise, and when repeated needle drainage (pericardiocentesis) has failed or is expected to be insufficient.The most common indication is a(...)
• PericarditisInflammation of the outer membrane surrounding the heart. When pericarditis occurs, the amount of fluid between the two layers of the pericardium increases. This increased fluid presses on the heart and restricts its pumping action.
• PericardiumThe pericardium is the double-walled fibrous sac that surrounds and encloses the heart and the roots of the great vessels (the aorta, pulmonary artery, vena cavae, and pulmonary veins). It has two main layers: the tough outer fibrous pericardium and the inner serous pericardium, which itself has two layers (the parietal and visceral layers). The space between the two serous layers (the pericardial space) normally contains 15 to 50 ml of lubricating fluid.The pericardium serves several(...)
• Peripheral Vascular disease (PVD)Disease of the blood vessels that supply blood to the limbs.
• PerseverationThe inappropriate persistence of a response in a current task which may have been appropriate for a former task. Perseveration may be verbal or motoric.
• Personal Independence PaymentPersonal Independence Payment (PIP) is a UK government benefit for people aged 16 to state pension age who have a long-term physical or mental health condition or disability that affects their ability to carry out daily activities or move around. It is not means-tested, is not affected by savings or income, and can be claimed whether the person is in work or not. How PIP is assessed PIP is assessed against two components:Daily living component: covers activities such as preparing food,(...)
• PericardiectomyPericardiectomy is a surgical procedure in which all or part of the pericardium (the membranous sac surrounding the heart) is removed. It is most commonly performed to treat constrictive pericarditis, a condition in which the pericardium has become thickened, scarred, and inflexible, restricting the heart's ability to fill normally.In constrictive pericarditis, chronic inflammation of the pericardium (caused by previous infection, surgery, radiotherapy, autoimmune disease, or sometimes(...)
• PharmacistA healthcare professional who ensures that medication that service users receives are safe, effective and appropriate.
• PharmacyA pharmacy (or dispensary in a hospital context) is the department responsible for the procurement, storage, preparation, and dispensing of medicines. Hospital pharmacies supply all medications required for inpatient care, including standard prescribed medicines, complex infusions, and specialised cardiac drugs. Community pharmacies dispense prescriptions for outpatients and provide medicines advice to the public.Clinical pharmacists work as part of multidisciplinary teams in hospital(...)
• PhobiasThis is an extremely common problem in the general population. Phobias are irrational and uncontrollable fears of an object or situation that most people can face without anxiety.The object or situation will trigger feelings of intense panic and the sufferer will go to great lengths to avoid them. Common phobias are fear of flying, spiders and enclosed spaces.
• Patient Health Questionnaire-9The Patient Health Questionnaire-9. A validated 9-item self-report tool used to screen for and measure the severity of depression. Each item asks how often the person has experienced a particular symptom over the past two weeks, scored 0 (not at all) to 3 (nearly every day), giving a total score of 0–27. Scores of 5, 10, 15, and 20 represent mild, moderate, moderately severe, and severe depression respectively. The PHQ-9 is widely used in GP and outpatient settings and is often used(...)
• PHQ-9The Patient Health Questionnaire-9. A validated 9-item self-report tool used to screen for and measure the severity of depression. Each item asks how often the person has experienced a particular symptom over the past two weeks, scored 0 (not at all) to 3 (nearly every day), giving a total score of 0–27. Scores of 5, 10, 15, and 20 represent mild, moderate, moderately severe, and severe depression respectively. The PHQ-9 is widely used in GP and outpatient settings and is often used(...)
• PhysiotherapistA health professional who helps you to improve mobility and general fitness.
• PiaOne of the three membranes surrounding and protecting the brain and spinal cord. The pia lies below the subarachnoid space in direct contact with the surface of the nerve tissue.
• PICCOThis is a special line connected to a computer which works out how well your heart is working and responding to fluids.
• Pituitary glandA small structure at the base of the brain which releases a wide variety of hormones that, in turn, control the activity of the body's other hormone glands.
• Plaque (Atherosclerotic)An atherosclerotic plaque is a deposit of fatty material, cholesterol, inflammatory cells, calcium, and fibrous tissue that builds up within the inner lining (intima) of an artery wall. Plaque formation is the hallmark of atherosclerosis, the underlying process in coronary artery disease and peripheral artery disease.Plaque develops over many years through a process triggered by injury or dysfunction of the arterial lining (endothelium), often caused by hypertension, smoking, high(...)
• PlateletsOne of the three types of cells found in blood; they aid in the clotting of blood.
• PleuraA term which may refer to either (1 ) visceral pleura a membrane which encloses each lung, or (2) parietal pleura a membrane which lines the inside wall of the chest cavity.
• Pleural CavityThe pleural cavity is the potential space between the two layers of the pleura, the thin membranes that line the lungs (visceral pleura) and the inside of the chest wall (parietal pleura). Under normal circumstances this space is not a true cavity but contains only a very thin film of lubricating fluid (around 5 to 15 ml), which allows the two pleural surfaces to slide smoothly against each other as the lungs expand and contract with each breath.The integrity of the pleural cavity is(...)
• Pleural EffusionA pleural effusion is an abnormal collection of fluid in the pleural cavity, the space between the two layers of the pleura (the membranes lining the lungs and chest wall). The normal pleural space contains only a tiny amount of lubricating fluid; when excess fluid accumulates, it can compress the underlying lung, impair its expansion, and cause breathlessness and reduced oxygen levels.Pleural effusions are classified as transudates (resulting from abnormal fluid dynamics, such as(...)
• Pneumonia A disease of the lungs marked by inflammation, congestion, fever, cough, and difficulty in breathing and caused especially by infection
• PneumothoraxA pneumothorax is the presence of air in the pleural cavity, the space between the lung and the chest wall. Normally this space contains only a thin film of fluid; when air enters it, the normal negative pressure that keeps the lung expanded is lost and the lung collapses to some degree.Pneumothorax can be classified by cause. Primary spontaneous pneumothorax occurs without an obvious cause, most commonly in tall young men with small blebs (air sacs) on the lung surface that rupture.(...)
• Polyunsaturated fatPolyunsaturated fats are a type of dietary fat in which the fatty acid chains contain two or more double bonds between carbon atoms (hence 'poly', meaning many). Unlike saturated fats (which are solid at room temperature), polyunsaturated fats are typically liquid at room temperature and are the predominant fat in most plant-based oils, including corn, safflower, sunflower, and soybean oils.There are two main families: omega-6 fatty acids (found in vegetable oils, nuts, and seeds) and(...)
• Positron Emission TomographyPositron emission tomography (PET) is an advanced nuclear medicine imaging technique that produces three-dimensional images of metabolic and physiological processes within the body. Unlike anatomical imaging (such as CT or MRI, which show structure), PET shows how tissues are functioning at a cellular level by detecting the radiation emitted by a radioactive tracer injected into the bloodstream.In cardiac imaging, PET is used to assess myocardial viability and perfusion. The most(...)
• PETPositron emission tomography (PET) is an advanced nuclear medicine imaging technique that produces three-dimensional images of metabolic and physiological processes within the body. Unlike anatomical imaging (such as CT or MRI, which show structure), PET shows how tissues are functioning at a cellular level by detecting the radiation emitted by a radioactive tracer injected into the bloodstream.In cardiac imaging, PET is used to assess myocardial viability and perfusion. The most(...)
• Post-Cardiac Arrest SyndromePost-cardiac arrest syndrome (PCAS) is the term used to describe the complex combination of problems that affect the body in the hours and days following successful resuscitation from cardiac arrest. Even after the heart has been restarted, PCAS can cause serious harm and is a major reason why many people who are resuscitated do not ultimately survive to hospital discharge. The four components PCAS has four overlapping elements:Post-cardiac arrest brain injury - The brain is highly(...)
• Post-Intensive Care SyndromePost-Intensive Care Syndrome (PICS) describes a cluster of new or worsening physical, cognitive, and psychological problems that develop in survivors of critical illness treated in an Intensive Care Unit (ICU). PICS is distinct from post-cardiac arrest syndrome, which refers specifically to the physiological consequences of cardiac arrest itself, though the two commonly co-exist in cardiac arrest survivors. Physical manifestations of PICS include muscle weakness (ICU-acquired weakness),(...)
• PICSPost-Intensive Care Syndrome (PICS) describes a cluster of new or worsening physical, cognitive, and psychological problems that develop in survivors of critical illness treated in an Intensive Care Unit (ICU). PICS is distinct from post-cardiac arrest syndrome, which refers specifically to the physiological consequences of cardiac arrest itself, though the two commonly co-exist in cardiac arrest survivors. Physical manifestations of PICS include muscle weakness (ICU-acquired weakness),(...)
• Post-resuscitation CareThe medical care provided after return of spontaneous circulation (ROSC) following cardiac arrest, typically in an intensive care unit. The goals of post-resuscitation care are to stabilise the patient, identify and treat the underlying cause of the arrest, limit further organ injury (particularly to the brain), and support recovery. Key components include targeted temperature management, continuous monitoring, coronary angiography if a cardiac cause is suspected, and neurological(...)
• Post-traumatic amnesiaThe period after being unconscious when there may be confused behaviour and no continuous memory of day to day events.
• Post-Traumatic GrowthPost-traumatic growth (PTG) is the experience of positive psychological change that some people report following a profoundly difficult or life-threatening event. It does not mean the trauma was a good thing, or that there is no ongoing distress: rather, it describes how struggling with a major challenge can, for some, lead to meaningful changes in perspective, relationships, and sense of purpose. Common areas of growth Research by psychologists Richard Tedeschi and Lawrence Calhoun, who(...)
• Post-traumatic stress disorderPost-traumatic stress disorder (PTSD) is a mental health condition that can develop after exposure to a traumatic event or series of events. It is extremely common after sudden cardiac arrest, affecting a significant proportion of both survivors and those who witnessed the event, including family members and bystanders who performed CPR.**Core symptoms of PTSD**- **Re-experiencing:** flashbacks, nightmares, [intrusive memories](/glossary/intrusive-memories/), and intense distress when(...)
• PTSDPost-traumatic stress disorder (PTSD) is a mental health condition that can develop after exposure to a traumatic event or series of events. It is extremely common after sudden cardiac arrest, affecting a significant proportion of both survivors and those who witnessed the event, including family members and bystanders who performed CPR.**Core symptoms of PTSD**- **Re-experiencing:** flashbacks, nightmares, [intrusive memories](/glossary/intrusive-memories/), and intense distress when(...)
• Postural orthostatic tachycardia syndromeA disorder that causes an increased heart rate when a person stands upright
• PoTSA disorder that causes an increased heart rate when a person stands upright
• PrasugrelMedication that is used to prevent clots forming in blood vessels after a procedure called Percutaneous Coronary Intervention (PCI) (to open a blocked artery in the heart or for a stent insertion)
• Pregnancy After Cardiac ArrestFor survivors of cardiac arrest who are of childbearing age, questions about future pregnancy are important and deserve careful specialist consideration. Pregnancy places significant additional demands on the cardiovascular system, and the safety of pregnancy after cardiac arrest depends heavily on the underlying cause of the arrest, residual cardiac function, and any ongoing medication or device requirements. Why specialist advice is essential Pregnancy should not be considered without(...)
• Premature Atrial ContractionsAre premature heartbeats that are similar to PVCs, but occur in the upper chambers of the heart, an area known as the atria. PACs do not typically cause damage to the heart and can occur in healthy individuals with no known heart disease.
• PACAre premature heartbeats that are similar to PVCs, but occur in the upper chambers of the heart, an area known as the atria. PACs do not typically cause damage to the heart and can occur in healthy individuals with no known heart disease.
• Premature ventricular contractionAn early or extra heartbeat that happens when the heart’s lower chambers (the ventricles) contract too soon, out of sequence with the normal heartbeat
• PVCAn early or extra heartbeat that happens when the heart’s lower chambers (the ventricles) contract too soon, out of sequence with the normal heartbeat
• PrevalencePrevalence is the proportion or total number of cases of a disease or condition that exist in a defined population at a specific point in time (point prevalence) or over a defined period (period prevalence). It reflects how widespread a condition is in a community.Prevalence is distinct from incidence, which measures the rate of new cases arising over time. A condition with a high prevalence may have a relatively low incidence if people live with it for many years (such as hypertension(...)
• Primary PCIPrimary PCI (percutaneous coronary intervention) is the use of emergency coronary angioplasty as the first-line treatment for a STEMI (ST-elevation myocardial infarction), the most serious form of heart attack. Rather than using clot-dissolving drugs (thrombolysis), the blocked coronary artery is opened mechanically by threading a catheter to the site of the blockage and inflating a balloon to compress the clot and plaque, followed by inserting a stent to keep the artery open.Primary PCI(...)
• Processing SpeedProcessing speed is the pace at which the brain takes in information, makes sense of it, and produces a response. It affects how quickly a person can read and understand text, respond in conversation, react to events, perform tasks under time pressure, and manage information arriving simultaneously from different sources. How processing speed is affected after cardiac arrest Slowed processing speed is one of the most commonly reported cognitive changes after cardiac arrest. Survivors may(...)
• PrognosisA clinical assessment of the likely future course and outcome of a patient's condition. In the context of cardiac arrest and intensive care, prognosis refers particularly to the predicted likelihood of survival and the degree of neurological recovery expected. Neuroprognostication — assessing likely brain function — is one of the most difficult and important tasks in post-cardiac arrest care, and is usually not attempted until at least 72 hours after the arrest to allow for the effects of(...)
• Prolapse ValveMitral or Aortic. Refers to one of the valve leaflets (flaps) being weaker than normal and tending to fall backwards when the valve closes,resulting often in valve regurgitation.
• Prone positioningPositioning a patient on their front. Sometimes undertaken to help improve a ventilated patient’s oxygen levels.
• ProphylaxisPrevention.For example measures to prevent coronary disease, diabetes and endocarditis.
• ProprioceptionThe sensory awareness of the position of body parts with or without movement.
• PsychiatristA doctor who specialises in the diagnosis and treatment of people who are mentally ill. Psychiatrists have undergone specialist training and may diagnose illness, prescribe medication and other forms of appropriate treatment.They also decide whether to admit people to and discharge from hospital.
• Psychological FormulationA psychological formulation is a collaborative summary, developed by a psychologist or therapist together with a person, that describes how and why they are experiencing their current difficulties. Unlike a diagnosis, which categorises symptoms into a clinical label, a formulation is a personalised explanation that integrates a person's history, experiences, beliefs, and current context to make sense of their distress. What a formulation includes A formulation typically(...)
• Psychological Wellbeing PractitionerA Psychological Wellbeing Practitioner (PWP) is a trained mental health worker who delivers low-intensity, evidence-based psychological interventions for mild to moderate anxiety and depression. PWPs work within NHS Talking Therapies services (formerly IAPT) and typically deliver guided self-help based on Cognitive Behavioural Therapy (CBT) principles. For cardiac arrest survivors with mild or moderate anxiety, low mood, or health anxiety, a PWP can provide a helpful first level of(...)
• PsychologistPsychologists have skills in the assessment and treatment of mental illness and psychological problems. Unlike psychiatrists they are not medical doctors, their skills include assessing cognitive functions (for example, speech and thought) and providing talking interventions including psychotherapy and counselling.
• PsychotherapistA psychotherapist is a trained mental health professional who uses structured talking therapies to help people understand and resolve emotional, psychological, and relational difficulties. Psychotherapists may work with individuals, couples, families, or groups. Their aim is to help clients develop greater insight, emotional regulation, and control over their responses to difficult experiences.The term psychotherapist covers a range of practitioners working in different therapeutic(...)
• PsychotherapyThe treatment of mental health, emotional and personality problems through talking with a therapist. There are many different types of psychotherapy.
• Public Access DefibrillationPublic access defibrillation (PAD) refers to the placement of automated external defibrillators (AEDs) in publicly accessible locations and the policy framework that enables trained or untrained members of the public to use them in an emergency. PAD programmes are a crucial part of the chain of survival for out-of-hospital cardiac arrest. Why public AEDs save lives Ventricular fibrillation (VF), the most common shockable rhythm in cardiac arrest, is treatable only by defibrillation. For(...)
• PulmonaryPulmonary is an adjective derived from the Latin pulmo (lung), meaning relating to the lungs. In medical terminology, it describes structures, conditions, and processes involving the lungs and the pulmonary circulation: the circuit by which blood travels from the right heart to the lungs to be oxygenated, and back to the left heart.Key pulmonary structures include the pulmonary arteries (which carry deoxygenated blood from the right ventricle to the lungs), the pulmonary veins (which(...)
• Pulmonary ArteryThe main artery carrying blood from the heart to the lungs.
• Pulmonary AtresiaPulmonary atresia is a congenital heart defect in which the pulmonary valve fails to form properly, resulting in complete obstruction of blood flow from the right ventricle to the pulmonary artery. Without a functioning pulmonary valve, blood cannot reach the lungs through the normal route to pick up oxygen.The condition varies in severity depending on how much of the right-sided structures are affected. In pulmonary atresia with intact ventricular septum, the right ventricle is often(...)
• Pulmonary EmbolismA pulmonary embolism (PE) is a blockage in one or more of the arteries supplying the lungs, caused by a blood clot (thrombus) that has travelled from elsewhere in the body, most commonly from a deep vein thrombosis (DVT) in the leg or pelvis. When a large clot or multiple clots obstruct the pulmonary circulation, the right ventricle must work against dramatically increased resistance, and oxygenation of the blood is severely impaired.Pulmonary embolism ranges widely in severity. Small(...)
• PEA pulmonary embolism (PE) is a blockage in one or more of the arteries supplying the lungs, caused by a blood clot (thrombus) that has travelled from elsewhere in the body, most commonly from a deep vein thrombosis (DVT) in the leg or pelvis. When a large clot or multiple clots obstruct the pulmonary circulation, the right ventricle must work against dramatically increased resistance, and oxygenation of the blood is severely impaired.Pulmonary embolism ranges widely in severity. Small(...)
• Pulmonary OedemaPulmonary oedema is the abnormal accumulation of fluid in the lung tissue and air sacs (alveoli), impairing gas exchange and causing severe breathlessness. It is most commonly caused by [left ventricular failure](/glossary/left-ventricular-failure/), in which the failing left ventricle cannot keep pace with blood returning from the lungs, causing pressure to rise in the pulmonary circulation and fluid to leak from the capillaries into the lungs.Symptoms include sudden, severe(...)
• Pulmonary StenosisPulmonary stenosis is a narrowing of the pulmonary valve or the pulmonary artery (or its branches), which restricts blood flow from the right ventricle to the lungs. It is among the more common forms of congenital heart disease and can also occur in adults as a consequence of previous cardiac surgery.The most common form is valvar pulmonary stenosis, where the pulmonary valve leaflets are thickened, fused, or malformed, reducing the size of the valve opening. Subvalvar stenosis (below(...)
• Pulmonary ValveThe valve at the origin of the pulmonary artery, which controls the flow of blood out of the right ventricle and prevents backflow.
• Pulmonary VeinThe blood vessel that carries newly oxygenated blood from the lungs back to the left atrium of the heart
• PulseThe pulse is the rhythmic pressure wave felt in an artery with each heartbeat, caused by the surge of blood expelled from the left ventricle during systole. It can be felt at multiple sites on the body where arteries run close to the surface: the radial artery at the wrist, the carotid artery in the neck, the femoral artery in the groin, the brachial artery in the inner arm, and others.The pulse provides several pieces of clinical information. Rate refers to the number of beats per(...)
• Pulse OximeterA probe that wraps around a hand or foot connected to a machine which measures how much oxygen the blood is carrying.
• Pulseless Electrical ActivityPulseless electrical activity (PEA) is a form of cardiac arrest in which the heart shows organised electrical activity on an ECG monitor, but is not producing a detectable pulse or effective cardiac output. Because the electrical signals appear relatively normal, PEA can be mistaken for a functioning heart rhythm, but the heart muscle is not responding with effective contractions.**Why it occurs**PEA occurs when there is a disconnect between the electrical system and the mechanical(...)
• PEAPulseless electrical activity (PEA) is a form of cardiac arrest in which the heart shows organised electrical activity on an ECG monitor, but is not producing a detectable pulse or effective cardiac output. Because the electrical signals appear relatively normal, PEA can be mistaken for a functioning heart rhythm, but the heart muscle is not responding with effective contractions.**Why it occurs**PEA occurs when there is a disconnect between the electrical system and the mechanical(...)

• q

• QT interval correctedCorrects the QT interval for heart rate extremes
• QTcCorrects the QT interval for heart rate extremes

• r

• Radial ArteryThe radial artery in the wrist is often used as the preferred entry point for the catheter in a PCI. Also called trans-radial access.
• Radial Artery AccessUsing the radial artery in the wrist as the entry point for the catheter in an angioplasty or stent procedure. Also called transradial access, the transradial approach, or transradial angioplasty
• Radionuclide ImagingA test in which a harmless radioactive substance is injected into the bloodstream to show information about blood flow through the arteries. Damaged or dead heart muscle can often be identified, as can serious narrowing in an artery
• Radionuclide StudiesRadionuclide studies (also called nuclear cardiology tests or nuclear stress tests) are diagnostic imaging investigations in which a small amount of a radioactive tracer is injected into the bloodstream. As the tracer travels through the heart, a specialised gamma camera detects the radiation it emits and constructs detailed images of blood flow through the heart muscle.The most common radionuclide test in cardiac care is myocardial perfusion imaging (MPI), which assesses how well(...)
• Radionuclide ventriculographyA diagnostic test used to determine the size and shape of the heart’s pumping chambers (the ventricles).
• Ramiprilto treat high blood pressure and heart failure, also used to help prevent heart, kidney or blood vessel problems in people who are at risk of these
• Rapid Access Chest Pain Service (RACPS)System for referral from Primary Care to Secondary Care for the assessment of chest pain.
• Reasonable AdjustmentsReasonable adjustments are changes that employers, service providers, and public bodies are legally required to make under the Equality Act 2010 to remove or reduce disadvantages faced by disabled people. For cardiac arrest survivors who have returned to or are returning to work, reasonable adjustments can make the difference between being able to work and not. Legal basis Under the Equality Act 2010, disability is defined broadly: it covers any physical or mental impairment that has a(...)
• Red Blood CellsThe blood cells which carry oxygen
• RegurgitationBackward flow of blood through a defective heart valve.
• RehabilitationRehabilitation is the process of restoring or improving a person's physical, cognitive, and psychological function following illness, injury, or surgery, with the goal of enabling them to live as independently and fully as possible. In the context of cardiac care and recovery from cardiac arrest, rehabilitation encompasses multiple dimensions of recovery.Cardiac rehabilitation is a structured NHS programme that combines supervised exercise, education about heart health and risk factors,(...)
• Rehabilitation ProgrammeA programme to aid recovery following a heart attack, heart surgery, coronary intervention or heart failure in the short and long term. The program provides education about exercise, lifestyle, relaxation and treatments.
• Remote Device MonitoringRemote device monitoring is a system that allows an implantable cardiac device (ICD, pacemaker, or CRT device) to automatically transmit data from the patient's home to the device clinic, without the need for a face-to-face appointment. It is now standard practice for the majority of patients with implanted cardiac devices in the UK. How it works The patient is provided with a small bedside communicator (sometimes called a transmitter or home monitor). At regular intervals, usually(...)
• Remote MonitoringRemote monitoring (also called remote device monitoring) is a technology that allows implanted cardiac devices such as ICDs, pacemakers, and CRT devices to transmit data from the patient's home to the device clinic without requiring a visit. A bedside communicator receives nightly transmissions from the device and sends them securely to the clinical team via a dedicated network.The data transmitted includes any arrhythmia episodes detected, therapies delivered (shocks or anti-tachycardia(...)
• RMRemote monitoring (also called remote device monitoring) is a technology that allows implanted cardiac devices such as ICDs, pacemakers, and CRT devices to transmit data from the patient's home to the device clinic without requiring a visit. A bedside communicator receives nightly transmissions from the device and sends them securely to the clinical team via a dedicated network.The data transmitted includes any arrhythmia episodes detected, therapies delivered (shocks or anti-tachycardia(...)
• RenalPertains to the kidneys.
• ReperfusionRestoration of blood flow to an organ or tissue. What happens after successful Percutaneous Coronary Intervention (PCI) or Thrombolysis.
• RescuerA person who performs CPR and/or uses a defibrillator on someone in cardiac arrest. A rescuer may be a bystander with no medical training, a trained first aider, a community first responder, or a healthcare professional. For cardiac arrest survivors, the identity of their rescuer — often a stranger, but sometimes a partner, family member, or colleague — can be a profound and complex part of their experience and recovery. Some survivors feel a strong desire to find and thank their rescuer;(...)
• RespirationBreathing
• RespiratorA machine for helping to maintain adequate respiration when the patient is unable to breath adequately on their own.
• RespiratoryAnything to do with 'respiration'.
• Respiratory arrestBreathing stops and there is no effective supply of fresh oxygen to the blood from the lungs. If breathing is not restored, cardiac arrest will quickly follow, as the heart muscle becomes starved of oxygen.
• Respiratory FailureRespiratory failure is a condition in which the respiratory system cannot maintain adequate oxygen levels, cannot adequately remove carbon dioxide, or both. Type 1 (hypoxaemic) respiratory failure involves low blood oxygen with a normal or low carbon dioxide level; it occurs when the lungs' ability to transfer oxygen is impaired, as in pneumonia, pulmonary embolism, or acute respiratory distress syndrome. Type 2 (hypercapnic) respiratory failure involves a high carbon dioxide level in the(...)
• RestenosisThe re-closing or re-narrowing of an artery after an interventional procedure such as angioplasty or stent placement
• ResuscitationResuscitation is the process of restoring life and physiological function to a person who has suffered collapse or cardiac arrest. In clinical practice the term most commonly refers to cardiopulmonary resuscitation (CPR) and advanced cardiac life support for cardiac arrest.CPR consists of chest compressions and rescue breaths performed to maintain circulation to the brain and vital organs until the underlying cause of arrest can be treated. High-quality chest compressions, delivered at a(...)
• Resuscitation Council UKResuscitation Council UK (RCUK) is the national professional body responsible for developing, publishing, and promoting evidence-based guidelines for resuscitation and first aid in the United Kingdom. It provides education and training resources for both healthcare professionals and members of the public, and works to improve survival rates from cardiac arrest across the UK. What RCUK does Key activities of Resuscitation Council UK include:Publishing the UK resuscitation guidelines,(...)
• Retrograde amnesiaThe loss of memory of events for a period prior to the injury.
• Return to Driving After Cardiac ArrestReturning to driving after cardiac arrest is a process governed by DVLA regulations and, where relevant, ICD implantation rules. The rules differ between Group 1 (car and motorcycle) and Group 2 (lorry and bus) licences, with Group 2 restrictions being significantly more stringent. The general process involves: notifying the DVLA of the cardiac event (a legal obligation), observing the mandatory driving ban period (which varies by diagnosis and whether an ICD has been implanted), obtaining(...)
• RevascularisationA procedure to restore blood flow to the tissues. Coronary artery bypass surgery is an example of a revascularisation procedure.
• Rheumatic feverA disease, usually occurring in childhood, that may follow a streptococcal infection. Symptoms may include fever, sore or swollen joints, skin rash, involuntary muscle twitching, and development of nodules under the skin. If the infection involves the heart, scars may form on heart valves, and the heart’s outer lining may be damaged.
• Rheumatic Heart DiseaseRheumatic heart disease is damage to one or more of the heart valves caused by rheumatic fever, an inflammatory condition triggered by an untreated or inadequately treated Group A streptococcal throat infection (strep throat). Rheumatic fever causes the immune system to attack the body's own tissues, including the heart valves, leading to inflammation and scarring.Repeated episodes of rheumatic fever (which can occur if streptococcal infections recur) progressively worsen valve damage.(...)
• RibThe ribs are a series of 24 curved bones arranged in 12 pairs that form the bony cage of the thorax. They articulate with the thoracic vertebrae of the spine at the back and, in most cases, connect to the sternum (breastbone) at the front via cartilaginous extensions. The rib cage protects the heart and lungs and plays an important mechanical role in breathing, rising and falling with each breath.In the context of cardiac care, ribs are most commonly discussed in relation to CPR(...)
• Right AtriumThe upper right chamber of the heart, which receives oxygen-poor (blue) blood from the body and pumps it to the right ventricle via the tricuspid valve.
• Right Bundle Branch BlockThis is a blockage of electrical impulses to the heart's right ventricle, the lower-right part of the heart
• RBBBThis is a blockage of electrical impulses to the heart's right ventricle, the lower-right part of the heart
• Right VentricleThe lower right chamber of the heart, which receives oxygen-poor (blue) blood from the right atrium and sends it to the pulmonary artery via the pulmonary valve.
• Right Ventricular Assist DeviceA right ventricular assist device (RVAD) is a mechanical pump that temporarily takes over or supplements the pumping function of the right ventricle. It draws blood from the right side of the heart (typically the right atrium) and pumps it forward into the pulmonary artery towards the lungs, bypassing a failing right ventricle. Unlike a left ventricular assist device (LVAD), which supports the systemic circulation, the RVAD supports the pulmonary circulation.RVADs may be implanted(...)
• RVADA right ventricular assist device (RVAD) is a mechanical pump that temporarily takes over or supplements the pumping function of the right ventricle. It draws blood from the right side of the heart (typically the right atrium) and pumps it forward into the pulmonary artery towards the lungs, bypassing a failing right ventricle. Unlike a left ventricular assist device (LVAD), which supports the systemic circulation, the RVAD supports the pulmonary circulation.RVADs may be implanted(...)
• Right Ventricular FailureThis is when the veins in the neck become engorged and fluid accumulates in the legs (peripheral oedema) or abdominal cavity heart are affected then a combination of the above features is seen. This is usually referred to as Congestive Cardiac Failure (CCF)
• RigidityRigidity means abnormal stiffness or resistance to passive movement of the limbs or body. It is distinct from normal voluntary muscle tension and from spasticity (which is velocity-dependent resistance associated with upper motor neurone injury). Rigidity has several distinct clinical patterns and causes, some of which are relevant in the context of cardiac arrest and brain injury.In the intensive care unit following cardiac arrest, rigidity of the limbs can be an early and concerning(...)
• Risk factorAn element or condition involving a certain hazard or danger. When referring to heart and blood vessels, a risk factor is associated with an increased chance of developing cardiovascular disease, including stroke.
• Return of Spontaneous CirculationReturn of Spontaneous Circulation. The moment at which a person's heart restarts and begins pumping blood independently following a cardiac arrest, without the need for ongoing CPR or defibrillation. Achieving ROSC is the immediate goal of resuscitation, but it is only the first step — the period following ROSC (post-resuscitation care) is critical to determining the patient's longer-term survival and neurological outcome. Many patients require intensive care following ROSC, including(...)
• ROSCReturn of Spontaneous Circulation. The moment at which a person's heart restarts and begins pumping blood independently following a cardiac arrest, without the need for ongoing CPR or defibrillation. Achieving ROSC is the immediate goal of resuscitation, but it is only the first step — the period following ROSC (post-resuscitation care) is critical to determining the patient's longer-term survival and neurological outcome. Many patients require intensive care following ROSC, including(...)
• Ross OperationThe Ross operation (also called the pulmonary autograft procedure) is a surgical technique for replacing a diseased aortic valve using the patient's own healthy pulmonary valve. The pulmonary valve, which is moved into the aortic position, is then replaced with a donated human valve (homograft) or a biological substitute in the pulmonary position. The procedure was first described by Donald Ross in 1967.The Ross operation is primarily used in younger adults and children with severe(...)

• s

• Saccular aneurysmA round aneurysm that bulges out from an artery; involves only part of the circumference (outside wall) of the artery.
• SarcoidosisAn inflammatory disease that starts as tiny, grain-like lumps called granulomas, which most often appear in your lungs or lymph nodes. The granulomas can clump together and form larger lumps that attack other organs. Sarcoidosis often affects your skin, eyes, or liver, but it can lead to heart problems, such as irregular heartbeats (arrhythmias) or restrictive cardiomyopathy.
• Saturated fatSaturated fat is a type of dietary fat in which the fatty acid chains have no double bonds between carbon atoms, meaning they are fully 'saturated' with hydrogen atoms. This structure makes them solid or semi-solid at room temperature. Saturated fats are found predominantly in animal products including butter, cheese, full-fat dairy, and fatty meat, as well as in certain plant sources such as coconut oil and palm oil.Saturated fat intake is associated with raised LDL cholesterol levels.(...)
• Second-degree Heart BlockImpulses traveling through the heart’s upper chambers (the atria) are delayed in the area between the upper and lower chambers (the AV node) and fail to make the ventricles beat at the right moment
• Secondary PreventionSecondary prevention refers to the measures taken after a serious health event to reduce the risk of that event recurring. In the context of cardiac arrest, secondary prevention encompasses all the treatments, devices, lifestyle changes, and monitoring strategies used to reduce the likelihood of a second cardiac arrest or sudden cardiac death. How secondary prevention differs from primary prevention Primary prevention aims to prevent a first event in people identified as being at risk.(...)
• Sedation-holdA sedation-hold (also called a spontaneous awakening trial or daily sedation interruption) is a planned, temporary reduction or complete suspension of sedative medications in a mechanically ventilated patient, allowing the clinical team to assess neurological function and determine whether the patient is ready to breathe independently and have their breathing tube removed.In the intensive care unit following cardiac arrest, sedation is typically administered continuously to keep patients(...)
• Seizure A sudden attack, spasm, or convulsion, as in epilepsy or another disorder
• Self-Compassion in RecoverySelf-compassion involves treating oneself with the same kindness, understanding, and patience one would offer a close friend who is struggling. In cardiac arrest recovery, self-compassion is an important psychological concept because survivors often experience self-criticism, guilt about the impact on family members, frustration at slow progress, or feelings that they should be "over it" by now. Research links higher self-compassion with better emotional adjustment, lower levels of(...)
• SensingThe ability of a pacemaker or ICD to recognize and respond to the electrical activity of the heart.
• Sensory cortexThe primary sensory cortex is situated on the upper surface of the cerebrum, directly behind the MOTOR CORTEX. Different areas of the sensory cortex specifically deal with the sensations experienced in different parts of the body.
• SepsisSepsis is a life-threatening medical emergency that occurs when the body's response to infection becomes dysregulated and starts to damage its own tissues and organs. Rather than containing the infection locally, the immune system triggers a widespread inflammatory response that disrupts blood flow, impairs oxygen delivery to organs, and can cause multi-organ failure.Sepsis can be caused by bacterial, viral, or fungal infections originating anywhere in the body, including the lungs(...)
• Septal defectA septal defect is a hole (opening) in the wall (septum) that divides two chambers of the heart. Depending on which septum is affected, the defect is classified as an atrial septal defect (ASD) or a ventricular septal defect (VSD).An atrial septal defect is a hole in the wall between the right and left atria (the upper chambers). Small ASDs may cause no symptoms and close spontaneously in childhood; larger ones allow a continuous left-to-right shunt that can, over time, cause right heart(...)
• SeptumThe muscular wall dividing a chamber on the left side of the heart from the chamber on the right.
• Sexual Activity and Intimacy After Cardiac ArrestConcerns about resuming sexual activity and intimacy are extremely common after cardiac arrest, yet they are rarely raised spontaneously in clinical consultations. Many survivors and their partners have significant anxiety about whether sexual activity is safe, when it can be resumed, and how an ICD might affect intimacy. These are legitimate and important questions that deserve a direct answer. Is sexual activity safe after cardiac arrest? For most cardiac arrest survivors, sexual(...)
• Shared Decision MakingA collaborative approach to healthcare in which clinicians and patients work together to make decisions about treatment and management plans. Rather than clinicians simply prescribing a course of action, shared decision making involves discussing the options, evidence, risks, and benefits, and taking into account the patient's values, preferences, and life circumstances. For ICD patients, shared decision making is particularly important around decisions such as ICD implantation, device(...)
• SheathA catheter-like tube that is placed inside a patient’s vessel during an interventional procedure to help the doctor with insertion and proper placement of the actual catheter. Also called an introducer sheath.
• ShockShock is a life-threatening condition in which the circulatory system fails to deliver sufficient oxygen and nutrients to the body's tissues to meet their metabolic needs. Without adequate perfusion, cells switch to anaerobic metabolism, producing lactic acid and ultimately dying. Shock is classified into four main types based on its underlying mechanism, each requiring a different approach to treatment.Cardiogenic shock occurs when the heart fails to pump effectively enough to maintain(...)
• Short QT SyndromeThis is a very rare genetic disease of the electrical system of the heart, associated with risk of abnormal heart rhythms and sudden cardiac death.
• SQTSThis is a very rare genetic disease of the electrical system of the heart, associated with risk of abnormal heart rhythms and sudden cardiac death.
• ShuntA connector that allows blood to flow between two locations.
• Sick Sinus SyndromeSick sinus syndrome (SSS), also called sinus node dysfunction, is a group of heart rhythm disorders caused by abnormal function of the sinoatrial (SA) node, the heart's natural pacemaker. The SA node normally generates regular electrical impulses that set the heart rate; in sick sinus syndrome, this function is impaired, resulting in a heart rate that is too slow, too fast, or alternates between the two.Common manifestations include: sinus bradycardia (an inappropriately slow heart rate(...)
• SSSSick sinus syndrome (SSS), also called sinus node dysfunction, is a group of heart rhythm disorders caused by abnormal function of the sinoatrial (SA) node, the heart's natural pacemaker. The SA node normally generates regular electrical impulses that set the heart rate; in sick sinus syndrome, this function is impaired, resulting in a heart rate that is too slow, too fast, or alternates between the two.Common manifestations include: sinus bradycardia (an inappropriately slow heart rate(...)
• Silent Heart AttackEpisodes of a heart attack that are not accompanied by chest pain
• Silent IschaemiaEpisodes of cardiac ischaemia that are not accompanied by chest pain.
• Sinus BradycardiaSinus bradycardia is a slow heart rate originating from the sinoatrial (SA) node (the heart's natural pacemaker), defined as a heart rate below 60 beats per minute with a normal electrical pathway through the heart. The term 'sinus' indicates that the rhythm originates from the SA node and follows the normal conduction sequence (P wave followed by QRS complex on the ECG); the rate is simply slower than the conventional lower limit of normal.Sinus bradycardia has many causes. It is common(...)
• Sinus NodeThe “natural” pacemaker of the heart. The node is a group of specialized cells in the top of the right atrium which produces the electrical impulses that travel down to eventually reach the ventricular muscle, causing the heart to contract
• SAThe “natural” pacemaker of the heart. The node is a group of specialized cells in the top of the right atrium which produces the electrical impulses that travel down to eventually reach the ventricular muscle, causing the heart to contract
• Sinus Node DysfunctionSinus node dysfunction (SND), also called sick sinus syndrome (SSS), is a group of heart rhythm abnormalities caused by the sinus node (the heart's natural pacemaker) failing to generate or conduct electrical impulses properly. The result can be a heart rate that is inappropriately slow, with or without intermittent fast rhythms alternating with slow ones (tachy-brady syndrome). The role of the sinus node The sinus node is a small cluster of specialised cells in the right atrium. It(...)
• Sinus RhythmA normal heart rhythm in which each electrical impulse originates in the sinus node, and proceeds through the rest of the electrical conduction system to cause a normal contraction sequence.
• Sinus TachycardiaA heart rhythm that originates in the sinus node and proceeds through the rest of the electrical conduction system, but is faster than normal.
• Sleep DisturbanceSleep disturbance is one of the most commonly reported problems in cardiac arrest survivors, yet it is often overlooked in clinical follow-up. Difficulty falling asleep, staying asleep, waking early, experiencing nightmares, or feeling unrefreshed despite adequate sleep hours can all significantly worsen fatigue, cognitive function, mood, and quality of life during recovery.**Types of sleep disturbance reported by survivors**- **Insomnia:** difficulty initiating or maintaining sleep,(...)
• Social PrescribingSocial prescribing is an NHS approach through which healthcare professionals connect people to non-clinical, community-based activities and services that support health and wellbeing. For cardiac arrest survivors, this can include peer support groups, wellbeing walks, creative arts programmes, befriending services, and volunteer activities. Social prescribing is delivered through Link Workers (also called Social Prescribing Link Workers), who are typically based within GP practices under(...)
• SodiumSodium is an essential mineral and electrolyte that is crucial for maintaining fluid balance, nerve transmission, and muscle contraction, including the contraction of the heart muscle. It is the primary positively charged ion in the fluid surrounding cells (extracellular fluid), and its concentration is tightly regulated by the kidneys and hormonal systems.Excess sodium in the body draws water with it, increasing circulating volume and blood pressure. High sodium intake is a significant(...)
• Somatosensory evoked potentialsElectrical responses of the brain recorded from the scalp following stimulation of nerves in the limbs. Failure to obtain SSEPs in someone in coma following an anoxic brain injury is associated with a poor outcome.
• SSEPsElectrical responses of the brain recorded from the scalp following stimulation of nerves in the limbs. Failure to obtain SSEPs in someone in coma following an anoxic brain injury is associated with a poor outcome.
• Source isolationPatients with some infections are routinely cared for ‘in isolation’ to help prevent the spread of infection to other patients. Commonly involves use of physical boundaries by caring for a patient in a side room to the main ward. Staff wear additional personal protective equipment and undertake appropriate hand washing before leaving the area. Side rooms may display alert notices and use directional airflow. Some immunosuppressed patients require ‘reverse isolation’ to protect them from(...)
• SpasticityAn involuntary increase in muscle tone following brain injury, which may produce tightness or stiffness of the limb muscles and interfere with movement and walking.
• Speaking ValveA speaking valve (also called a Passy-Muir valve or PMV) is a one-way device fitted to the outer opening of a tracheostomy tube that allows patients with a tracheostomy to speak. Normally, a tracheostomy tube directs air in and out through the stoma (the opening in the throat), bypassing the larynx (voice box) entirely, so the patient cannot produce voice. The speaking valve opens on inhalation to allow air in through the tracheostomy, but closes on exhalation, redirecting exhaled air(...)
• SphygmomanometerA sphygmomanometer is the medical instrument used to measure blood pressure. The name comes from the Greek sphygmos (pulse) combined with manometer (pressure gauge). The device consists of an inflatable cuff wrapped around the upper arm, a mechanism for inflating the cuff, and a pressure gauge that reads the pressure in millimetres of mercury (mmHg).Traditional sphygmomanometers were auscultatory: the cuff was inflated to temporarily block arterial blood flow, then slowly deflated. Blood(...)
• Spontaneous Coronary Artery DissectionSpontaneous coronary artery dissection (SCAD) is a rare but serious emergency condition in which a tear forms in the wall of a coronary artery, creating a false channel that can partially or completely block blood flow to the heart muscle. The tear separates the layers of the arterial wall without the involvement of atherosclerotic plaque, making SCAD distinct from the more common form of heart attack caused by coronary artery disease.SCAD most commonly affects women in their 40s and(...)
• SCADSpontaneous coronary artery dissection (SCAD) is a rare but serious emergency condition in which a tear forms in the wall of a coronary artery, creating a false channel that can partially or completely block blood flow to the heart muscle. The tear separates the layers of the arterial wall without the involvement of atherosclerotic plaque, making SCAD distinct from the more common form of heart attack caused by coronary artery disease.SCAD most commonly affects women in their 40s and(...)
• ST-segment-elevation myocardial infarctionA STEMI (ST-elevation myocardial infarction) is the most serious form of heart attack, caused by complete and sudden blockage of a coronary artery leading to rapid and progressive death of the heart muscle supplied by that artery. The term refers to the characteristic ECG finding: persistent elevation of the ST segment in leads corresponding to the affected coronary territory, indicating full-thickness ventricular ischaemia.STEMI most commonly results from rupture of an atherosclerotic(...)
• STEMIA STEMI (ST-elevation myocardial infarction) is the most serious form of heart attack, caused by complete and sudden blockage of a coronary artery leading to rapid and progressive death of the heart muscle supplied by that artery. The term refers to the characteristic ECG finding: persistent elevation of the ST segment in leads corresponding to the affected coronary territory, indicating full-thickness ventricular ischaemia.STEMI most commonly results from rupture of an atherosclerotic(...)
• StatinThe generic name for a family of prescribed cholesterol-lowering drugs.
• Statin TherapyStatins are a class of medication that reduce the level of LDL cholesterol (low-density lipoprotein, often called "bad" cholesterol) in the blood by inhibiting an enzyme in the liver (HMG-CoA reductase) involved in cholesterol production. They are one of the most prescribed and most evidence-based medications in cardiovascular medicine, and are frequently prescribed for cardiac arrest survivors, particularly those whose arrest was related to coronary artery disease. Why statins matter(...)
• Stem CellsStem cells are undifferentiated cells that have the ability to develop into more specialised cell types. They are found in various tissues throughout the body and play a key role in growth, repair, and renewal of tissues throughout life.In cardiac medicine, stem cell research has explored whether stem cells could be used to regenerate damaged heart muscle after heart attack or in heart failure, replacing muscle cells (cardiomyocytes) destroyed by ischaemia or disease. Laboratory and(...)
• StenosisThe narrowing or constriction of an opening, such as a blood vessel or heart valve.
• StentA stent is a small, hollow, expandable tube made of metal mesh that is placed inside a blood vessel to hold it open and prevent it from narrowing or collapsing. In cardiovascular medicine, coronary stents are used to treat blocked or narrowed coronary arteries, typically during percutaneous coronary intervention (PCI).During PCI, a balloon catheter is threaded through a blood vessel to the site of the coronary narrowing. The stent (mounted on the balloon in a collapsed state) is(...)
• SternumThe sternum (breastbone) is a flat, elongated bone in the centre of the chest that forms the anterior (front) part of the rib cage. It consists of three parts: the manubrium (the broad upper section at the level of the first and second ribs), the body (the long middle section, to which ribs 2 through 7 are attached via costal cartilages), and the xiphoid process (the small pointed lower tip). The sternum protects the heart and lungs and provides the bony anchor for the anterior rib(...)
• StethoscopeAn instrument for listening to sounds within the body.
• Stokes-Adams SyndromeStokes-Adams syndrome (also called Stokes-Adams disease or Adams-Stokes syndrome) is a term for episodes of sudden loss of consciousness caused by a transient fall in cardiac output, most commonly due to a complete failure of electrical conduction from the atria to the ventricles (complete heart block, also known as third-degree heart block).In complete heart block, the electrical signals that normally travel from the atria through the atrioventricular (AV) node to pace the ventricles(...)
• Streptococcal infectionA streptococcal infection is an infection caused by bacteria of the Streptococcus genus, responsible for a wide range of conditions. The most clinically relevant species in cardiovascular medicine are Streptococcus pyogenes (Group A Streptococcus) and the viridans streptococci group.Streptococcus pyogenes causes pharyngitis ('strep throat'), skin infections, and, in severe cases, sepsis. Critically, repeated or inadequately treated Group A streptococcal throat infections can trigger an(...)
• StreptokinaseA clot-dissolving medicine used to treat heart attack patients.
• StressBodily or mental tension resulting from physical, chemical, or emotional factors. Stress can refer to physical exertion as well as mental anxiety.
• StrokeA sudden disruption of blood flow to the brain, either by a clot or a leak in a blood vessel.
• Sub Aortic StenosisNarrowing below the aortic valve. This usually results from the presence of abnormal tissue or muscle below the valve
• Subarachnoid haemorrhageSubarachnoid haemorrhage (SAH) is bleeding from a blood vessel on the surface of the brain into the subarachnoid space: the area between the inner layers of the meninges (membranes covering the brain) that is normally filled with cerebrospinal fluid. Blood in this space rapidly spreads around the brain, causing intense headache and potentially life-threatening complications.The most common cause of spontaneous (non-traumatic) SAH is rupture of an intracranial aneurysm: a bulge in the(...)
• Subarachnoid spaceThe space between the ARACHNOID membrane and PIA mater. The subarachnoid space is filled with fluid (see: CSF).
• Subclavian arteriesThe subclavian arteries are the two major arteries (right and left) that arise from the aortic arch and supply blood to the arms, neck, and parts of the brain. Each subclavian artery runs beneath the clavicle (collarbone) and continues distally as the axillary and then the brachial artery supplying the arm. The subclavian arteries also give rise to the vertebral arteries (supplying the brainstem and cerebellum) and the internal mammary arteries (also called internal thoracic(...)
• Subcutaneous Internal Cardiac DefibrillatorA subcutaneous implantable cardioverter defibrillator (S-ICD or SICD) is a device that monitors heart rhythm and delivers a shock to correct life-threatening arrhythmias, without placing any leads (wires) inside the heart or blood vessels. All components sit beneath the skin: the generator is implanted under the skin at the left side of the chest, and a sensing lead runs just under the skin along the breastbone.A conventional transvenous ICD has leads that run through a vein into the(...)
• S-ICDA subcutaneous implantable cardioverter defibrillator (S-ICD or SICD) is a device that monitors heart rhythm and delivers a shock to correct life-threatening arrhythmias, without placing any leads (wires) inside the heart or blood vessels. All components sit beneath the skin: the generator is implanted under the skin at the left side of the chest, and a sensing lead runs just under the skin along the breastbone.A conventional transvenous ICD has leads that run through a vein into the(...)
• SublingualUnder the tongue. Some medicines are taken this way.
• SuctionIn a medical context, suction refers to the mechanical removal of secretions, fluid, blood, or foreign material from the airway using a device that applies negative pressure through a plastic catheter or tube. It is a routine procedure in critical care, anaesthesia, and emergency medicine.Suction is used to clear the nose, mouth, throat, or endotracheal tube when a patient cannot clear their own secretions effectively. This may be because they are unconscious, sedated, or have an(...)
• Sudden Cardiac ArrestSudden cardiac arrest is a medical emergency in which the heart suddenly and unexpectedly stops pumping blood effectively. It occurs when a fault in the heart's electrical system causes an abnormal rhythm, most commonly ventricular fibrillation, that prevents the heart from beating in a coordinated way. Without blood reaching the brain, a person loses consciousness within seconds and will die within minutes without treatment.Sudden cardiac arrest is not the same as a heart attack. A(...)
• SCASudden cardiac arrest is a medical emergency in which the heart suddenly and unexpectedly stops pumping blood effectively. It occurs when a fault in the heart's electrical system causes an abnormal rhythm, most commonly ventricular fibrillation, that prevents the heart from beating in a coordinated way. Without blood reaching the brain, a person loses consciousness within seconds and will die within minutes without treatment.Sudden cardiac arrest is not the same as a heart attack. A(...)
• Sudden Cardiac DeathSudden cardiac death (SCD) is the unexpected death that occurs as a result of a sudden cardiac arrest from which resuscitation is unsuccessful or is not performed. It is defined as natural death occurring within one hour of the onset of symptoms, or in an unwitnessed death, within 24 hours of the person last being seen alive and well. SCD accounts for a substantial proportion of all cardiovascular deaths worldwide.The most common cause is coronary artery disease: plaque rupture or acute(...)
• SCDSudden cardiac death (SCD) is the unexpected death that occurs as a result of a sudden cardiac arrest from which resuscitation is unsuccessful or is not performed. It is defined as natural death occurring within one hour of the onset of symptoms, or in an unwitnessed death, within 24 hours of the person last being seen alive and well. SCD accounts for a substantial proportion of all cardiovascular deaths worldwide.The most common cause is coronary artery disease: plaque rupture or acute(...)
• Sudden DeathDeath that occurs unexpectedly and instantaneously or shortly after the onset of symptoms. The most common underlying reason for patients dying suddenly is cardiovascular disease, in particular coronary heart disease.
• SulcusA groove of the cerebral cortex
• Superior Vena CavaThe superior vena cava (SVC) is the large vein that returns deoxygenated blood from the head, neck, arms, and upper chest to the right atrium of the heart. It is formed by the junction of the two brachiocephalic veins and descends into the right atrium. Together with the inferior vena cava (which collects blood from the lower body), it forms the main venous inflow to the right side of the heart.In critical care and interventional cardiology, the SVC has important practical significance.(...)
• SVCThe superior vena cava (SVC) is the large vein that returns deoxygenated blood from the head, neck, arms, and upper chest to the right atrium of the heart. It is formed by the junction of the two brachiocephalic veins and descends into the right atrium. Together with the inferior vena cava (which collects blood from the lower body), it forms the main venous inflow to the right side of the heart.In critical care and interventional cardiology, the SVC has important practical significance.(...)
• SupraSupra is a Latin prefix meaning 'above', 'over', or 'beyond'. In medical terminology, it describes structures, conditions, or processes located above a specified anatomical reference point. The opposite prefix is infra (meaning 'below' or 'beneath').In cardiovascular medicine, 'supra-' appears in several important terms. Supraventricular means 'above the ventricles' and describes arrhythmias originating in the atria, sinoatrial node, or atrioventricular node. Supraventricular tachycardia(...)
• Supravalvar Aortic StenosisSupravalvar aortic stenosis (SVAS) is a rare form of obstruction to blood flow out of the left ventricle, in which the narrowing occurs above the aortic valve rather than at the valve itself (valvar stenosis) or below it (subvalvar stenosis). The obstruction typically involves a localised narrowing or diffuse hypoplasia (underdevelopment) of the ascending aorta just above the sinuses of Valsalva.SVAS can occur as an isolated abnormality or as part of Williams syndrome, a genetic(...)
• Supra CardiacSupra cardiac is a term in congenital heart surgery and anatomy meaning 'above the heart'. It is most commonly encountered in the classification of total anomalous pulmonary venous drainage (TAPVD), a rare but serious congenital heart condition in which the pulmonary veins (which normally carry oxygenated blood from the lungs to the left atrium) instead connect abnormally to a systemic vein.TAPVD is classified by the site of the anomalous connection. In supra cardiac TAPVD (the most(...)
• Supraventricular TachycardiaSupraventricular tachycardia (SVT) is a group of cardiac arrhythmias characterised by a rapid heart rate originating above the ventricles (in the atria, sinoatrial node, or atrioventricular node). The heart rate in SVT is typically 150 to 250 beats per minute, and the rhythm is usually regular. SVT is the most common group of arrhythmias causing symptoms in adults, particularly in young and otherwise healthy people.SVT encompasses several distinct arrhythmias. Atrioventricular nodal(...)
• SVTSupraventricular tachycardia (SVT) is a group of cardiac arrhythmias characterised by a rapid heart rate originating above the ventricles (in the atria, sinoatrial node, or atrioventricular node). The heart rate in SVT is typically 150 to 250 beats per minute, and the rhythm is usually regular. SVT is the most common group of arrhythmias causing symptoms in adults, particularly in young and otherwise healthy people.SVT encompasses several distinct arrhythmias. Atrioventricular nodal(...)
• Survivor GuiltFeelings of guilt associated with surviving an event in which others did not, or with the circumstances of survival. In the cardiac arrest context, survivor guilt can take several forms. Survivors may feel guilty for the distress their cardiac arrest caused to those around them, for the care burden placed on a partner, or simply for having survived when statistically most people do not. Co-survivors who performed CPR may feel guilty about whether they did it correctly, did not start(...)
• Survivor's GuiltSurvivor's guilt is a psychological response in which a person who has survived a life-threatening event feels guilt, shame, or a sense of undeservedness about having survived when others did not, or when they perceive that their survival came at a cost to others. In the context of cardiac arrest, it can take several forms and is more common than is often recognised. How it manifests in cardiac arrest survivors Survivor's guilt after cardiac arrest is not always about other cardiac arrest(...)
• SyncopeSyncope (pronounced 'SIN-ko-pee') is a sudden, brief loss of consciousness caused by a temporary reduction in blood flow and oxygen supply to the brain. The person typically collapses, is unresponsive for seconds to a few minutes, and then recovers spontaneously. Syncope must be distinguished from cardiac arrest (no spontaneous recovery without resuscitation) and from epileptic seizures.Syncope has several distinct mechanisms. Vasovagal syncope (the most common type, also called a simple(...)
• SystemicSystemic is a medical adjective meaning 'involving or relating to the whole body', as opposed to a localised or organ-specific process. It is used to describe conditions, treatments, or physiological processes that affect the entire organism rather than a single organ or region.In cardiovascular medicine, 'systemic' most commonly appears in the term systemic circulation: the part of the circulatory system that carries oxygenated blood from the left side of the heart to all organs and(...)
• SystoleSystole is the phase of the cardiac cycle during which the heart muscle contracts to pump blood out of the ventricles. It is one of two alternating phases of the heartbeat, the other being diastole (the period of relaxation and filling). Blood pressure measurements are expressed as systolic pressure over diastolic pressure (for example, 120/80 mmHg).During systole, electrical activation from the heart's conduction system triggers coordinated contraction of the ventricular muscle.(...)
• Systolic blood pressureSystolic blood pressure is the pressure exerted on the walls of the arteries at the moment of maximum force during a heartbeat, when the left ventricle contracts and ejects blood into the aorta. It is the higher of the two numbers in a blood pressure reading (expressed as systolic over diastolic, for example 120/80 mmHg) and represents the peak arterial pressure during each cardiac cycle.Normal systolic blood pressure for most adults at rest is considered below 130 mmHg. Systolic blood(...)
• SBPSystolic blood pressure is the pressure exerted on the walls of the arteries at the moment of maximum force during a heartbeat, when the left ventricle contracts and ejects blood into the aorta. It is the higher of the two numbers in a blood pressure reading (expressed as systolic over diastolic, for example 120/80 mmHg) and represents the peak arterial pressure during each cardiac cycle.Normal systolic blood pressure for most adults at rest is considered below 130 mmHg. Systolic blood(...)

• t

• TachyTachy is a Greek prefix meaning 'fast'. In medical terminology, it is used to describe conditions characterised by an abnormally fast rate, most commonly in relation to heart rhythms or breathing.The most common cardiac uses of the prefix include tachycardia (abnormally fast heart rate, above 100 beats per minute in adults), ventricular tachycardia (a fast rhythm originating in the ventricles), and supraventricular tachycardia (fast rhythms originating above the ventricles).(...)
• TachycardiaTachycardia is the medical term for an abnormally fast heart rate, defined as a resting heart rate above 100 beats per minute in adults. The word derives from the Greek tachys (fast) and kardia (heart). While the heart rate naturally increases during exercise, stress, or fever (physiological sinus tachycardia), pathological tachycardia arises from abnormal electrical activity in the heart itself.Tachycardia is classified by the site of origin. Supraventricular tachycardia (SVT) refers to(...)
• TachypnoeaTachypnoea is the medical term for an abnormally fast breathing rate. In adults, a normal resting respiratory rate is 12 to 20 breaths per minute; tachypnoea is generally defined as a rate above 20 breaths per minute at rest. It is one of the earliest and most sensitive indicators of physiological deterioration and is a key parameter in the National Early Warning Score (NEWS2).Tachypnoea occurs as a compensatory response to conditions that disrupt normal gas exchange or increase(...)
• Takotsubo CardiomyopathyTakotsubo cardiomyopathy (also known as stress cardiomyopathy or broken heart syndrome) is a temporary but acute weakening of the left ventricle, most commonly triggered by intense physical or emotional stress. The condition mimics a heart attack in its presentation but, unlike a heart attack, is not caused by blockage of a coronary artery.During an episode, the apex (lower tip) of the left ventricle balloons outwards and stops contracting effectively, while the base of the ventricle(...)
• Talking TreatmentsTalking treatments (also called psychological therapies or psychotherapy) are mental health interventions in which improvement in a person's symptoms and wellbeing is achieved through structured conversation with a trained therapist or counsellor, rather than (or as well as) medication. They are based on the principle that thoughts, feelings, behaviours, and mental health are interconnected, and that therapeutic conversations can help people develop insight, change unhelpful patterns, and(...)
• TamponadeTamponade in the cardiac context (cardiac tamponade) is a life-threatening emergency in which fluid accumulates within the pericardial sac surrounding the heart, building up sufficient pressure to compress the heart chambers and prevent them from filling with blood. This significantly reduces cardiac output and can rapidly cause cardiovascular collapse and cardiac arrest.The pericardial sac normally contains only a very small amount of lubricating fluid. When fluid accumulates (from(...)
• Targeted Temperature ManagementTargeted temperature management (TTM), previously called therapeutic hypothermia, is a treatment used in intensive care after cardiac arrest to reduce brain injury. It involves carefully controlling the patient's body temperature to prevent additional damage during the critical recovery period after the heart restarts. Why temperature matters after cardiac arrest When blood flow stops during cardiac arrest, brain cells are deprived of oxygen. When circulation is restored, a reperfusion(...)
• Telemetry UnitA small box with wires attached to ECG patches on the chest; used to continuously monitor the rhythm via radio transmission to healthcare professionals for evaluation.
• Temporal lobesThe part of the cerebral hemispheres located under the frontal and parietal lobes, lying inwards of the ears. It has a range of important functions and is involved with hearing and some complex aspects of auditory, language and visual perception, as well as memory and emotion.
• TetralogyTetralogy is a term meaning 'a group of four', used in cardiology almost exclusively in the context of Tetralogy of Fallot, the most common cyanotic congenital heart defect, first described comprehensively by the French physician Étienne-Louis Arthur Fallot in 1888.Tetralogy of Fallot (ToF) consists of four anatomical abnormalities occurring together due to a developmental problem in the formation of the fetal heart's outflow tract: a ventricular septal defect (VSD, a hole between the(...)
• Tetralogy of FallotTetralogy of Fallot (ToF) is the most common cyanotic congenital heart defect, consisting of four anatomical abnormalities occurring together: a ventricular septal defect (VSD, a hole between the lower chambers), pulmonary stenosis (narrowing obstructing blood flow from the right ventricle to the lungs), right ventricular hypertrophy (thickening of the right ventricular muscle in response to the obstruction), and an overriding aorta (the aorta sits over the VSD, receiving blood from both(...)
• TOFTetralogy of Fallot (ToF) is the most common cyanotic congenital heart defect, consisting of four anatomical abnormalities occurring together: a ventricular septal defect (VSD, a hole between the lower chambers), pulmonary stenosis (narrowing obstructing blood flow from the right ventricle to the lungs), right ventricular hypertrophy (thickening of the right ventricular muscle in response to the obstruction), and an overriding aorta (the aorta sits over the VSD, receiving blood from both(...)
• Thallium-201 Stress TestA thallium-201 stress test is a type of radionuclide myocardial perfusion imaging used to assess blood flow through the heart muscle at rest and during stress. Thallium-201 is a radioactive isotope that behaves similarly to potassium and is taken up by living, metabolically active heart muscle cells in proportion to their blood supply.During the test, a small dose of thallium-201 is injected into the bloodstream at peak exercise (or at the point of maximum pharmacological stress if the(...)
• Therapeutic hypothermiaAlso known as Targeted Temperature Management (TTM). A controlled lowering of the core body temperature (typically to 32–36°C) following cardiac arrest, used to reduce brain cell metabolism and limit neurological injury during recovery. Current ILCOR and ERC guidelines support active temperature control in post-cardiac arrest care, with the specific target temperature determined by the clinical team based on the patient’s condition.
• Third-degree Heart BlockThird-degree heart block (also called complete heart block) is the most severe form of atrioventricular (AV) block, in which there is complete dissociation between the electrical activity of the atria and the ventricles. No impulses from the atria are conducted to the ventricles at all; the ventricles rely on their own slow escape rhythm from a subsidiary pacemaker, typically producing a rate of 20 to 40 beats per minute.The slow ventricular rate severely reduces cardiac output, causing(...)
• ThrillA thrill is the clinical term for a vibration felt by the examiner's hand placed on the chest wall, corresponding to heart sounds and murmurs of sufficient loudness and turbulence to be transmitted through the chest wall as a palpable vibration. It is essentially the tactile equivalent of a loud murmur: a heart murmur graded 4/6 or louder (on the clinical 1 to 6 scale) is typically associated with a palpable thrill.Thrills are felt at the location where the underlying turbulent blood(...)
• ThrombolysisThrombolysis is the process of dissolving a blood clot (thrombus) using pharmacological agents that activate the body's natural clot-dissolving mechanism. The term is most commonly used for drug treatment (thrombolytic therapy), in which clot-dissolving medicines are administered intravenously to dissolve life-threatening blood clots and restore blood flow.The main thrombolytic drugs (also called fibrinolytics or 'clot-busters') include alteplase (tPA), tenecteplase, and reteplase. They(...)
• Thrombolytic therapyThrombolytic therapy refers to the use of medicines that dissolve blood clots by activating the body's natural fibrinolytic system. These medicines are given intravenously (into a vein) or occasionally intra-arterially (directly into the blocked artery) to restore blood flow through an obstructed vessel.Thrombolytic agents include alteplase, tenecteplase, reteplase, and streptokinase. They work by activating plasminogen, which converts to plasmin and breaks down the fibrin mesh holding(...)
• ThrombosisThrombosis is the formation of a blood clot (thrombus) within a blood vessel or a cavity of the heart, reducing or blocking blood flow. Under normal circumstances, clotting is a protective mechanism that stops bleeding when a vessel is damaged. Thrombosis occurs when this process is triggered inappropriately or excessively within an intact vessel.Three factors (known as Virchow's triad) predispose to thrombosis: abnormal blood flow (such as turbulence or sluggish circulation), changes to(...)
• ThrombusA blood clot.
• ThyroidA gland located in the front of the neck, just below the voice box.
• Tilt Table TestA tilt table test is a diagnostic procedure used to investigate unexplained blackouts (syncope) and near-blackouts (presyncope) by reproducing the conditions that cause a drop in blood pressure or heart rate when a person moves from lying to standing. It is a safe, non-invasive test performed in a supervised cardiac or neurology unit. How the test works The patient lies flat on a motorised table and is secured with straps. After a period of rest, the table tilts to bring the patient to a(...)
• Tissue plasminogen activatorTissue plasminogen activator (tPA) is a naturally occurring protein in the body that activates plasmin, the main enzyme responsible for dissolving blood clots (fibrinolysis). In medical use, tPA refers to recombinant forms of this protein (such as alteplase, tenecteplase, and reteplase) that are administered as medicines to break down dangerous blood clots in emergencies.tPA is used as a thrombolytic (clot-dissolving) treatment in two main emergency settings. In acute ischaemic stroke,(...)
• TPATissue plasminogen activator (tPA) is a naturally occurring protein in the body that activates plasmin, the main enzyme responsible for dissolving blood clots (fibrinolysis). In medical use, tPA refers to recombinant forms of this protein (such as alteplase, tenecteplase, and reteplase) that are administered as medicines to break down dangerous blood clots in emergencies.tPA is used as a thrombolytic (clot-dissolving) treatment in two main emergency settings. In acute ischaemic stroke,(...)
• Tissue ValveAn artificial valve, made from animal tissues (pig or cow) and, mounted on a frame with cloth surround, enabling it to be sewn into the heart. There is no requirement for anticoagulation once a tissue valve is inserted unless there is another indication.
• TitrationThis is a method of determining what substances are in a person’s system by testing bodily fluids. It can detect substances such as prescribed medication and also illegal substances such as drugs or alcohol. Dose titration means to slowly increase the dose of a drug to a level that can be maintained.
• Torsade de PointesTorsade de pointes (TdP) is a distinctive and potentially life-threatening form of ventricular tachycardia in which the QRS complexes appear to twist around the baseline of the ECG, with varying amplitude and axis. The name comes from the French for 'twisting of the points', describing its characteristic ECG appearance.TdP occurs in the context of a prolonged QT interval (the period on the ECG representing ventricular depolarisation and repolarisation). A long QT creates a window of(...)
• TdPTorsade de pointes (TdP) is a distinctive and potentially life-threatening form of ventricular tachycardia in which the QRS complexes appear to twist around the baseline of the ECG, with varying amplitude and axis. The name comes from the French for 'twisting of the points', describing its characteristic ECG appearance.TdP occurs in the context of a prolonged QT interval (the period on the ECG representing ventricular depolarisation and repolarisation). A long QT creates a window of(...)
• Total Anomalous Pulmonary Venous DrainageA defect in which the pulmonary (lung) veins are connected to veins from the body (i.e. the SVC or IVC) or to the right atrium, instead of returning to the left atrium).
• TAPVDA defect in which the pulmonary (lung) veins are connected to veins from the body (i.e. the SVC or IVC) or to the right atrium, instead of returning to the left atrium).
• TracheostomyThis is where a tube is inserted into the windpipe through an incision in the skin of the neck. It needs a small operation and usually replaces the endotracheal tube and is more comfortable when the sedation is turned off.
• Trans FatTrans fat (also called trans fatty acid) is a type of unsaturated fat that has been artificially hydrogenated: a process in which hydrogen is forced through liquid vegetable oil, rearranging some double bonds in the fatty acid chains into a trans configuration. This changes the physical properties of the oil, making it more solid and shelf-stable, which led to partially hydrogenated oils being widely used in processed foods, margarines, and commercial frying.Artificial trans fats have(...)
• Transcatheter aortic valve implantationA minimally invasive procedure to repair a damaged or diseased aortic valve. A catheter is inserted into an artery in the groin and threaded to the heart. A balloon at the end of the catheter, with a replacement valve folded around it, delivers the new valve to take the place of the old. Also called TAVR (Transcatheter aortic valve replacement)
• TAVIA minimally invasive procedure to repair a damaged or diseased aortic valve. A catheter is inserted into an artery in the groin and threaded to the heart. A balloon at the end of the catheter, with a replacement valve folded around it, delivers the new valve to take the place of the old. Also called TAVR (Transcatheter aortic valve replacement)
• Transcatheter InterventionA transcatheter intervention is any procedure carried out through a catheter (a thin, flexible tube) inserted into the body via a small puncture in a blood vessel, rather than through open surgery. The catheter is guided to the target site under imaging guidance, and the therapeutic action (such as balloon inflation, stent deployment, valve repair, or ablation) is performed at the tip of the catheter.The term transcatheter intervention broadly encompasses the same procedures as(...)
• TransferTransfer in a medical context refers to the movement of a patient from one location to another, either within the same hospital (intra-hospital transfer) or between different hospitals (inter-hospital transfer). Both types require careful planning to ensure patient safety, as critically ill patients are particularly vulnerable during transitions when monitoring and emergency equipment may be temporarily reduced.Intra-hospital transfers are common for critically ill patients requiring(...)
• Transient Ischaemic AttackA transient ischaemic attack (TIA), commonly called a 'mini-stroke', is a temporary disruption of blood supply to part of the brain that causes neurological symptoms but resolves completely within 24 hours (typically within minutes to a few hours) without causing permanent brain injury. The underlying process is identical to an ischaemic stroke, but the blockage is either very small or clears spontaneously before permanent damage occurs.Symptoms of a TIA mirror those of stroke: sudden(...)
• TIAA transient ischaemic attack (TIA), commonly called a 'mini-stroke', is a temporary disruption of blood supply to part of the brain that causes neurological symptoms but resolves completely within 24 hours (typically within minutes to a few hours) without causing permanent brain injury. The underlying process is identical to an ischaemic stroke, but the blockage is either very small or clears spontaneously before permanent damage occurs.Symptoms of a TIA mirror those of stroke: sudden(...)
• Transoesophageal EchocardiographyA type of ultrasound which produces images of the Heart viewed from the Oesophagus (gullet) and used to assess the structure and function of the heart unimpeded by the bone and lungs which affects imaging through the chest wall (transthoracic echocardiography).
• TOEA type of ultrasound which produces images of the Heart viewed from the Oesophagus (gullet) and used to assess the structure and function of the heart unimpeded by the bone and lungs which affects imaging through the chest wall (transthoracic echocardiography).
• TransplantationTransplantation is a surgical procedure in which a failing organ or tissue is replaced with a healthy one from a donor, either a living donor or a deceased donor. In cardiovascular medicine, the most important form is heart transplantation.Heart transplantation is the definitive treatment for end-stage heart failure that cannot be managed with medical therapy, cardiac resynchronisation therapy, or mechanical circulatory support. The recipient's failing heart is removed and replaced with(...)
• Transposition of the Great ArteriesTransposition of the great arteries (TGA) is a serious congenital heart defect in which the two main arteries leaving the heart (the aorta and the pulmonary artery) are switched from their normal positions. In a normal heart, the aorta arises from the left ventricle and carries oxygenated blood to the body, while the pulmonary artery arises from the right ventricle and carries deoxygenated blood to the lungs. In TGA, these connections are reversed.This creates two parallel circulations(...)
• Transthoracic EchocardiographyA type of ultrasound which produces images of the heart viewed from the chest wall and used to assess the structure and function of the heart.
• TTEA type of ultrasound which produces images of the heart viewed from the chest wall and used to assess the structure and function of the heart.
• TraumaIn psychological terms, trauma refers to the emotional and psychological response to an event — or series of events — that overwhelms a person's ability to cope. Trauma is not defined by the event itself but by its impact on the individual. The same event can be traumatic for one person and not for another, and neither response is wrong. For cardiac arrest, trauma can affect not only the survivor but equally the co-survivor — the partner, family member, or friend who witnessed the arrest,(...)
• Traumatic Brain InjuryDamage to the brain resulting from a head injury.
• TBIDamage to the brain resulting from a head injury.
• TremorRegular repetitive movements which may be worse either at rest or on attempted movement.
• Tricuspid AtresiaTricuspid atresia is a congenital heart condition in which the tricuspid valve (the valve between the right atrium and right ventricle) is absent or completely obstructed, so no blood can flow directly from the right atrium into the right ventricle to be pumped to the lungs.Survival after birth depends on alternative routes for blood to reach the lungs. Blood from the right atrium passes through an atrial septal defect or patent foramen ovale into the left atrium and mixes with(...)
• Tricuspid StenosisTricuspid stenosis is a narrowing of the tricuspid valve, which controls blood flow from the right atrium to the right ventricle. When the valve opening is narrowed, the right atrium must work harder to push blood through the restricted orifice, leading to a rise in right atrial pressure and reduced filling of the right ventricle.Tricuspid stenosis is the least common of the major adult valve stenoses. The most common cause is rheumatic heart disease, where inflammation following(...)
• Tricuspid ValveThe valve at the junction of the right atrium with the right ventricle, which controls flow of blood into the ventricle before each contraction, and prevents backflow
• Tricuspid ValveThe structure that controls blood flow from the heart’s upper right chamber (the right atrium) into the lower right chamber (the right ventricle).
• Tricuspid Valve DiseaseTricuspid regurgitation is very common and usually due to heart failure. Stenosis of this valve is rare.
• Triggered Refers to an unpleasant and unexpected reminder of past pain or trauma. When we are triggered, we begin to feel emotions related to a trauma that happened to us in the past, even though those events aren’t being talked about directly.
• TriglycerideThe most common fatty substance found in the blood; normally stored as an energy source in fat tissue. High triglyceride levels often accompany other risk factors for heart disease, such as obesity.
• TroponinTroponin is a protein complex found in heart muscle cells (and in skeletal muscle) that plays a central role in regulating muscle contraction. The cardiac-specific forms, troponin I (cTnI) and troponin T (cTnT), are released into the bloodstream when heart muscle cells are damaged or die. Measuring troponin in the blood is the cornerstone of diagnosing heart attack (myocardial infarction).Modern high-sensitivity troponin (hs-Tn) assays can detect extremely small amounts of troponin in(...)
• Truncus ArteriosusTruncus arteriosus is a rare congenital heart defect in which a single large arterial trunk (vessel) arises from the heart instead of the two separate vessels (aorta and pulmonary artery) that are normally present. Blood from both the right and left ventricles, which communicate through a large ventricular septal defect (VSD), flows into this common trunk. The single vessel then gives rise to both the systemic and pulmonary circulations.Because oxygenated and deoxygenated blood mix, and(...)

• u

• UltrasoundHigh-frequency sound vibrations, which cannot be heard by the human ear, used in medical diagnosis.
• Unsaturated FatA type of ‘good’ fat found mainly in foods from plants and fish sources. They include monounsaturated fats and polyunsaturated fats.
• Unstable AnginaAt the lower end of the Acute Coronary Syndrome spectrum. Angina that is of new onset, more readily provoked and/or occurring at rest and without a rise in Troponin.
• Urinary CatheterA urinary catheter is a thin, flexible tube inserted through the urethra into the bladder to continuously drain urine into a sealed collection bag. It allows accurate measurement of urine output without the patient needing to use a toilet, which is especially important in intensive care settings where hourly fluid balance monitoring is critical.In the intensive care unit following cardiac arrest, urinary catheterisation is performed routinely as part of post-resuscitation management.(...)

• v

• ValveA structure in a blood vessel or the heart which ensures blood flows only one way. They are constructed of single or multiple flaps which swing open to allow blood to flow forwards and swing shut to prevent back flow. The valve flaps are referred to as 'leaflets' or 'cusps'.
• Valve RegurgitationAlso called valve insufficiency or incompetence. The one-way valve fails to close completely and leaks.
• Valve replacementAn operation to replace a heart valve that is either blocking normal blood flow or causing blood to leak backward into the heart (regurgitation).
• Valve StenosisValve stenosis is a narrowing of one of the heart's four valves (aortic, mitral, pulmonary or tricuspid) that restricts blood flow through it. The narrowed opening forces the heart to work harder to push blood forward, increasing pressure in the upstream chamber and, over time, causing the muscle to thicken or dilate. Stenosis can be congenital (present from birth due to abnormal valve development) or acquired through age-related calcification, rheumatic fever or inflammatory(...)
• ValvesThe “doors” between the chambers of the heart that allow blood to move forward and prevent it from moving backward. The heart valves are called tricuspid, pulmonary, mitral, and aortic and control the flow of blood into and out of the heart.
• Valvular Heart DiseaseWhen at least one of the four heart valves is diseased or damaged.
• ValvuloplastyValvuloplasty is a procedure to reshape, repair, or widen a diseased heart valve without replacing it. The term encompasses both surgical and catheter-based (transcatheter) techniques, depending on the valve affected and the patient's circumstances.Balloon valvuloplasty is the most common catheter-based form. A thin tube (catheter) is threaded through a blood vessel to the narrowed (stenotic) valve, and a balloon at the tip is inflated to stretch the valve opening wider and improve blood(...)
• Variants of Unknown SignificanceIn a small number of cases, genetic testing finds a “variant of unknown significance,” or VUS. This means there is a portion of the gene that looks different from the way it’s normally expected to look
• VUSIn a small number of cases, genetic testing finds a “variant of unknown significance,” or VUS. This means there is a portion of the gene that looks different from the way it’s normally expected to look
• Varicose veinAny vein that is abnormally dilated (widened).
• VascularPertains to the blood vessels.
• VasodilatorA medication that dilates a blood vessel through relaxation.
• VasodilatorsAny medicine that dilates (widens) the arteries.
• VasopressorsVasopressors are a class of medication that constrict blood vessels and raise blood pressure, used to treat critically low blood pressure (hypotension) that cannot be corrected by fluid replacement alone. They work by stimulating receptors in blood vessel walls, causing them to narrow (vasoconstriction) and thereby increasing the resistance against which the heart pumps, which raises arterial pressure.Vasopressors are an essential component of treatment in the critical care unit for(...)
• Vasovagal SyncopeVasovagal syncope is a temporary loss of consciousness caused by a sudden drop in blood pressure and, often, a slowing of the heart rate. It is the most common cause of blackout and fainting, accounting for the majority of syncopal episodes seen in otherwise healthy people. The mechanism involves an abnormal reflex response of the vagus nerve that causes blood vessels to dilate and the heart rate to slow, reducing blood flow to the brain.Common triggers include prolonged standing, heat,(...)
• Vegetative stateA vegetative state is a disorder of consciousness in which a person has lost all meaningful awareness of their environment but retains some basic brain functions. The brainstem continues to regulate vital functions such as breathing, heart rate and sleep-wake cycles, and the person may open their eyes, make sounds or display reflex movements. However, there is no evidence of purposeful response to commands or communication, no indication of awareness of self or surroundings, and no sign of(...)
• VeinAny one of a series of blood vessels of the vascular system that carries blood from various parts of the body back to the heart, returning oxygen-poor blood to the heart.
• Vena CavaThe vena cava refers to the two largest veins in the body: the superior vena cava (SVC) and the inferior vena cava (IVC). Together they return all deoxygenated blood from the systemic circulation to the right atrium of the heart, completing the circuit before blood is pumped to the lungs for reoxygenation. The SVC drains blood from the head, neck, arms and upper chest, while the IVC collects blood from the abdomen, pelvis and legs.In the critical care setting, the SVC is a key site for(...)
• VentilateTo ventilate a patient means to use a mechanical ventilator to deliver breaths to a patient who cannot breathe adequately for themselves, or to support a patient whose own breathing effort is insufficient to maintain safe oxygen and carbon dioxide levels.Mechanical ventilation is indicated when a patient is unconscious, has respiratory failure, has been anaesthetised for surgery, or cannot maintain adequate airway protection. After cardiac arrest, patients who remain unconscious(...)
• VentilatorA machine that delivers oxygen to a patient's lungs to assist with the breathing process. Also see 'Respirator'
• Ventilator-associated pneumoniaPneumonia in a ventilated patient. Several aspects of ventilation leave patients vulnerable to infection. The breathing tube bypasses many of the body’s natural defences whilst immobility and the absence of coughing lead to retained secretions. A common complication of critical care therapy.
• VAPPneumonia in a ventilated patient. Several aspects of ventilation leave patients vulnerable to infection. The breathing tube bypasses many of the body’s natural defences whilst immobility and the absence of coughing lead to retained secretions. A common complication of critical care therapy.
• VentricleThe ventricles are the two powerful muscular pumping chambers in the lower half of the heart. They receive blood from the upper chambers (the atria) and pump it out under high pressure: the right ventricle to the lungs, and the left ventricle to the rest of the body.The left ventricle is the heart's main pump. It has thick, muscular walls (around 9 to 12mm) to generate the high pressures needed to drive blood around the systemic circulation. The right ventricle is less muscular because(...)
• Ventricular Assist DeviceA mechanical pump that helps the ventricles pump blood, easing the workload of the heart in patients with heart failure
• VADA mechanical pump that helps the ventricles pump blood, easing the workload of the heart in patients with heart failure
• Ventricular Ectopic BeatsVentricular ectopic beats (VEBs), also called premature ventricular contractions (PVCs) or ventricular extrasystoles, are extra heartbeats that originate in the ventricles rather than in the sinus node (the heart's normal pacemaker). They are among the most common cardiac arrhythmias and occur in the majority of people at some point, including those with completely healthy hearts. What causes them VEBs can be triggered by stimulants such as caffeine, alcohol, and nicotine; by stress and(...)
• Ventricular FibrillationVentricular fibrillation (VF) is a life-threatening heart rhythm disturbance and the most common cause of sudden cardiac arrest. Instead of contracting in a coordinated sequence, the ventricles (the heart's lower pumping chambers) produce rapid, chaotic electrical signals that cause the muscle fibres to quiver rather than pump. The result is an immediate and complete loss of cardiac output: no blood reaches the brain or vital organs.In a normal heartbeat, an orderly electrical impulse(...)
• VFVentricular fibrillation (VF) is a life-threatening heart rhythm disturbance and the most common cause of sudden cardiac arrest. Instead of contracting in a coordinated sequence, the ventricles (the heart's lower pumping chambers) produce rapid, chaotic electrical signals that cause the muscle fibres to quiver rather than pump. The result is an immediate and complete loss of cardiac output: no blood reaches the brain or vital organs.In a normal heartbeat, an orderly electrical impulse(...)
• Ventricular Septal DefectA ventricular septal defect (VSD) is a hole in the ventricular septum, the muscular wall separating the left and right ventricles of the heart. VSDs are the most common congenital heart defect, occurring in approximately 2 to 5 per 1,000 live births. They may also develop as a rare but serious complication following a myocardial infarction (post-infarction VSD).The clinical significance of a VSD depends on its size. Because blood pressure in the left ventricle is substantially higher(...)
• VSDA ventricular septal defect (VSD) is a hole in the ventricular septum, the muscular wall separating the left and right ventricles of the heart. VSDs are the most common congenital heart defect, occurring in approximately 2 to 5 per 1,000 live births. They may also develop as a rare but serious complication following a myocardial infarction (post-infarction VSD).The clinical significance of a VSD depends on its size. Because blood pressure in the left ventricle is substantially higher(...)
• Ventricular SeptumThe ventricular septum is the thick muscular wall that divides the left and right ventricles (the two lower pumping chambers of the heart) from each other. Together with the interatrial septum (which separates the two atria), it forms the internal partitioning of the heart. The ventricular septum comprises the muscular portion (the bulk of the wall, which contracts with each heartbeat) and a smaller membranous portion near the aortic root.The ventricular septum maintains the separation(...)
• Ventricular TachycardiaVentricular tachycardia (VT) is a potentially life-threatening heart rhythm disorder in which the ventricles (the heart's lower pumping chambers) beat at an abnormally fast rate, typically 100 beats per minute or above, driven by rapid electrical impulses originating within the ventricular muscle rather than the normal sinus node.VT is classified by duration: non-sustained VT terminates spontaneously within 30 seconds; sustained VT persists beyond 30 seconds and is a cardiac emergency.(...)
• VTVentricular tachycardia (VT) is a potentially life-threatening heart rhythm disorder in which the ventricles (the heart's lower pumping chambers) beat at an abnormally fast rate, typically 100 beats per minute or above, driven by rapid electrical impulses originating within the ventricular muscle rather than the normal sinus node.VT is classified by duration: non-sustained VT terminates spontaneously within 30 seconds; sustained VT persists beyond 30 seconds and is a cardiac emergency.(...)
• VertigoA feeling of dizziness or spinning.
• VestibularSystem in the middle of the ear which senses movement. Injury can lead to dizziness.
• Vicarious TraumaTrauma that develops as a result of witnessing, or being closely involved in, another person's traumatic experience — rather than experiencing the event directly oneself. Vicarious trauma is particularly relevant for co-survivors of cardiac arrest: watching a partner or family member collapse, believing they are dying, witnessing resuscitation attempts, or sitting at an ICU bedside while uncertainty about survival continues can be deeply traumatising in their own right. The symptoms of(...)
• Vocational RehabilitationVocational rehabilitation (VR) is a structured process designed to help people with health conditions, disabilities, or injuries return to work, retain their job, or find suitable new employment. For cardiac arrest survivors, who often face a combination of physical, cognitive, and psychological challenges, vocational rehabilitation can be an essential part of the recovery journey. What vocational rehabilitation involves VR is not a single intervention but a coordinated set of supports(...)

• w

• Ward RoundThe daily visit by a consultant and their team to each patient on a ward or in ICU to review progress, discuss test results, adjust treatment plans, and make decisions about care. Ward rounds typically happen in the morning and can move quickly. For co-survivors and family members, the ward round is often the most important opportunity of the day to hear directly from the clinical team — though in busy units it can be brief. Family members are not always present during ward rounds but can(...)
• WeanedThis is a term used when a patient is being taken off of the breathing machine and is only undertaken when their condition is improving.
• Wearable Cardioverter DefibrillatorA wearable cardioverter defibrillator (WCD), most commonly known by the brand name LifeVest, is an external device worn around the body that continuously monitors heart rhythm and can automatically deliver a defibrillation shock if a life-threatening arrhythmia is detected. Unlike an implantable cardioverter defibrillator (ICD), it does not require surgery and can be fitted and removed at any time. How it works The WCD consists of a garment containing electrodes that sit against the skin(...)
• Wellness Action Plan An easy, free and practical way of helping you to support your own mental health at work and, if you are a manager, helping you to support the mental health of your team members.
• Wernicke's AreaLocated in the temporal lobe, Wernicke's area is the region of the brain responsible for language comprehension — understanding spoken and written words. Damage to this area typically results in Wernicke's aphasia, where speech is fluent but lacks meaningful content. (See also BROCA'S AREA)
• White Matter White coloured nerve tissue in the brain is made up of myelin covered axons, which transmit electrical signals through the nervous system. The white matter lies underneath the grey matter of the cerebral cortex and white matter tracts travel down through the brainstem and into the spinal cord.
• Withdrawal of life-sustaining therapies Withdrawal of life-sustaining therapies refers to stopping or discontinuing medical treatments that keep a person alive but will not cure their underlying medical condition. This decision is often made when it is determined that further treatment is futile and the person is unlikely to recover or when the person is suffering and the continuation of treatment is causing more harm than good.Examples of life-sustaining therapies include mechanical ventilation for people who can no longer(...)
• WSLT Withdrawal of life-sustaining therapies refers to stopping or discontinuing medical treatments that keep a person alive but will not cure their underlying medical condition. This decision is often made when it is determined that further treatment is futile and the person is unlikely to recover or when the person is suffering and the continuation of treatment is causing more harm than good.Examples of life-sustaining therapies include mechanical ventilation for people who can no longer(...)
• Wolff-Parkinson-White syndromeWolff-Parkinson-White syndrome (WPW) is a heart condition caused by the presence of an extra electrical pathway between the atria and ventricles, known as an accessory pathway or bundle of Kent. This additional connection bypasses the AV node (which normally acts as a gatekeeper, slowing electrical signals between the upper and lower chambers) and can cause fast heart rhythms (tachycardias), and in rare cases, sudden cardiac arrest.**The ECG finding: pre-excitation**Because the(...)
• Working MemoryWorking memory is the cognitive system responsible for temporarily holding and manipulating information in the mind while it is being used. It is often described as a mental "scratchpad" that allows a person to keep track of what they are doing, follow a line of reasoning, hold instructions in mind, and link ideas across a conversation or task. How it differs from long-term memory Working memory is not the same as long-term memory. Long-term memory stores information over days, months, and(...)

• x

• X-rayForm of radiation used to create a picture of internal body structures on film.