Coronary 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 cholesterol, inflammatory cells, and fibrous tissue. As plaques grow, they narrow the artery (stenosis) and reduce blood flow to the heart muscle. If a plaque ruptures suddenly, a blood clot can form at the rupture site and block the artery completely, causing a [heart attack](/glossary/heart-attack/) (myocardial infarction). A heart attack can trigger [ventricular fibrillation](/glossary/ventricular-fibrillation/) and [cardiac arrest](/glossary/cardiac-arrest/).
Risk factors for CAD include high cholesterol, [hypertension](/glossary/hypertension/), smoking, [diabetes](/glossary/diabetes/), physical inactivity, obesity, a family history of heart disease, and increasing age. Many of these risk factors are modifiable with lifestyle change and medication.
Symptoms of CAD include [angina](/glossary/angina/) (chest pain or discomfort on exertion), breathlessness, and fatigue. Some people have no symptoms until a heart attack occurs. Investigations include [coronary angiography](/glossary/coronary-angiography/), CT coronary angiography, and stress testing.
Treatment depends on severity and may include lifestyle changes, medication ([statins](/glossary/statin-therapy/), [beta-blockers](/glossary/beta-blocker/), [antiplatelet therapy](/glossary/antiplatelet-therapy/)), [percutaneous coronary intervention (PCI)](/glossary/percutaneous-coronary-intervention/), or [coronary artery bypass graft (CABG)](/glossary/coronary-artery-bypass-graft/) surgery. After cardiac arrest caused by CAD, treatment of the underlying disease forms a key part of [secondary prevention](/glossary/secondary-prevention/).
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