What is Myocardial Infarction?

Commonly called a heart attack, a myocardial infarction results from coronary heart disease (C.H.D.)—blood vessel disease in the heart. Coronary artery disease (C.A.D.) and ischemic heart disease are other names for coronary heart disease.

What causes a heart attack?
A heart attach occurs when the blood supply to part of the heart muscle itself—the myocardium—is severely reduced or stopped. This occurs when one of the coronary arteries that supply blood to the heart muscle is blocked. The blockage is usually from the buildup of plaque (deposits of fat-like substances) due to atherosclerosis. The plaque can eventually tear or rupture, triggering a blood clot to form that blocks the artery and leads to a heart attack. Such an event is sometimes called a coronary thrombosis or coronary occlusion.

If the blood supply is cut off severely or for a long time, muscle cells suffer irreversible injury and die. Disability or death can result, depending on how much heart muscle is damaged.

Sometimes a coronary artery temporarily contracts or goes into spasm. When this happens, the artery narrows and blood flow to part of the heart muscle decreases or stops. What causes a spasm is unclear. But spasm can occur in normal-appearing blood vessels as well as vessels partly blocked by atherosclerosis. If a spasm is severe, a heart attack may result.