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A heart attack (myocardial infarction) occurs when the blood supply to the heart muscle is severely reduced or stopped. This is usually due to blockage of a coronary artery following rupture of an atherosclerotic plaque and/or the development of a blood clot. Such an event might also be called a coronary thrombosis or coronary occlusion. The subsequent lack of oxygen can result in disability or death of the affected part of the heart muscle.
Sometimes a heart attack is caused by severe spasm of a coronary artery, rather than a blockage. The exact causes of spasm in coronary arteries are unclear; spasm can occur apparently normal arteries, as well as those partly blocked by atherosclerosis.
The symptoms of a heart attack include chest pain or discomfort (which may extend to the back, jaw, neck or arms) and shortness of breath, possibly accompanied by other signs (e.g. cold sweat, nausea, light-headedness, sense of doom).
