Cardiac 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 reasons, including in people with no known heart disease.
The most common immediate cause of cardiac arrest in adults is ventricular fibrillation (VF): a chaotic, uncoordinated electrical rhythm in the ventricles that produces no effective heartbeat. VF can arise from coronary artery disease and heart attack, inherited cardiac conditions (such as hypertrophic cardiomyopathy, long QT syndrome, Brugada syndrome), cardiomyopathies, and structural heart disease. In some cases no cause can be identified (idiopathic ventricular fibrillation).
The treatment for cardiac arrest is immediate CPR (cardiopulmonary resuscitation) to maintain blood flow to the brain, combined with defibrillation (a controlled electric shock) to restore a normal heart rhythm. Every minute without CPR or defibrillation reduces the chance of survival by approximately 10%. Rapid response from bystanders using CPR and a publicly available AED, combined with emergency services, forms the chain of survival.
Approximately 30,000 out-of-hospital cardiac arrests occur in the UK each year, with an overall survival rate of around 10 to 12%. Survivors face a recovery journey that may include cognitive and physical rehabilitation, psychological support, cardiac investigation and treatment (including ICD implantation in most cases), and adjustment to life after a life-threatening event. SCA UK exists specifically to support survivors, their families, and those bereaved by cardiac arrest.