Myocardial Infarction Health Article

Definition

A myocardial infarction, or heart attack, is the death or damage of part of the heart muscle because the supply of blood to the heart muscle is severely reduced or stopped.

Description

Myocardial infarction (MI) is the leading cause of death in the United States. More than 1.5 million Americans suffer a myocardial infarction every year, and nearly half a million die, according to the American Heart Association. Most myocardial infarctions are the end result of years of silent, undetected, progressive coronary artery disease. A myocardial infarction is often the first detected symptom of coronary artery disease. According to the American Heart Association, 63% of women and 48% of men who died suddenly of coronary artery disease had no previous symptoms. Myocardial infarctions are commonly called heart attacks.

A myocardial infarction occurs when one or more of the coronary arteries that supply blood to the heart are completely blocked and blood to the heart muscle is cut off. The blockage is usually caused by atherosclerosis, the build-up of plaque in artery walls, and/or by a blood clot in a coronary artery. Sometimes, a healthy or atherosclerotic coronary artery has a spasm and the blood flow to part of the heart decreases or stops. The result may be a myocardial infarction.

About half of all myocardial infarction patients wait at least two hours before seeking help. This delay dramatically increases the risk of sudden death or disability. The longer the artery remains blocked during a myocardial infarction, the more damage will be done to the heart. If the blood supply is cut off severely, or for longer than 12 hours, muscle cells suffer irreversible injury and die. The patient can die. That is why it is vitally important to teach patients to recognize the signs of a myocardial infarction and seek immediate medical attention at the nearest hospital with 24-hour emergency cardiac care.

About one fifth of all myocardial infarctions are silent, that is, the patient is unaware that the MI has occurred. Although the patient feels no pain, silent myocardial infarctions still damage the heart.

The outcome of a myocardial infarction depends on the location of the blockage, whether the heart rhythm is disturbed, and whether there is collateral circulation to the territory supplied by the acutely occluded coronary artery. Blockages in the left coronary artery are usually more serious than those affecting the right coronary artery. Blockages that produce arrhythmia (irregular heartbeat) can cause sudden death.