What is a heart attack (myocardial infarction or MI)?
A heart attack, or myocardial infarction, occurs when one or more regions of the heart muscle experience a severe or prolonged lack of oxygen caused by blocked blood flow to the heart muscle. The blockage is often a result of atherosclerosis – a buildup of plaque composed of fat deposits, cholesterol, and other substances. Plaque ruptures and eventually a blood clot forms. The actual cause of a heart attack is a blood clot that forms within the plaque-obstructed area. If the blood and oxygen supply is cut off severely or for a long period of time, muscle cells of the heart suffer damage and die. The result is dysfunction of the muscle of the heart in the area affected by the lack of oxygen.
