Heart Attack

Essentially, a heart attack is the death of a portion of the heart muscle due to lack of oxygen. Heart attacks, which claim 570,000 lives in the United States each year, are usually a complication of coronary arthrosclerosis, fatty thickening of the walls of the coronary arteries.

All that is needed to produce a heart attack is for a small blood clot to form in one of the narrowed coronary arteries, blocking the blood supply to a portion of the heart. Thus deprived of nourishment, the heart muscle that is fed by the affected artery dies. This event is called a myocardial infarction (death of a section of the heart muscle). Physicians also use the term coronary thrombosis (referring to a blood clot in a coronary artery). Another way the event can occur is via the formation of a coronary embolism; a piece of clotted material breaks away from the artery and floats down the bloodstream, lodging in and damming up, a narrowed coronary artery (embolus is the Greek word for “wedge shaped stopper”). Myocardial infarction, heart attack follows.

Whether a heat attack victim lives or dies depends in part on where the blockage occurs. If the flow of blood through one of the main arteries is blocked, large portions of the heart muscle may die, irreparably damaging the heart’s pumping mechanism. Usually, however, only a small arterial branch is affected, and other areas of the heart are able to compensate for the loss.

A heart attack not only damages the muscle physically; it may also cause the heart’s delicate electrical system to go out of control. When this happens, the heart beats in an abnormal rhythm (an arrhythmia). In one arrhythmia known as fibrillation, parts of the heart, the atria, the ventricles, or both, may beat irregularly at an extremely fast rate, hundreds of times a minute and in an uncoordinated way. When this happens, the heart is incapable of pumping blood; unless the fibrillation can be stopped and normal circulation restored, the patient will die. CPR (cardiopulmonary resuscitation) should begin immediately.