Causes Of Heart Attack

« INSULIN-DEPENDENT (TYPE 1) DIABETES | Home | Diagnosis &Treatment Of Heart Attack »

By peace | May 23, 2006

Most heart attacks are caused by a blood clot that blocks one of the coronary arteries (the blood vessels that bring blood and oxygen to the heart muscle). When blood cannot reach part of your heart, that area starves for oxygen. If the blockage continues long enough, cells in the affected area die. Unlike exertional angina, death of the heart muscle from a heart attack is permanent.

A heart attack is caused by the formation of a blood clot on a cholesterol plaque located on the inner wall of an artery to the heart (coronary artery). Cholesterol is a fatty chemical which is part of the outer lining of cells in the body. Cholesterol plaque is the formation of a hard, thick substance within the artery walls which is caused by deposits of cholesterol in the artery walls; a process that begins in the late teens. Over time, the accumulation of cholesterol plaque causes thickening of the artery walls and narrowing of the arteries; a process called atherosclerosis.

Plaque accumulation can be accelerated by smoking, high blood pressure, elevated cholesterol, and diabetes. Ultimately, atherosclerosis causes significant narrowing of the coronary arteries. During exercise or excitement, the narrowed coronary arteries cannot increase the blood supply to meet the increased oxygen demand of the heart muscle. When the heart muscle is thus deprived of blood oxygen, a condition called ischemia results; ischemia may be associated with chest pain (angina pectoris). Typically, angina occurs with exertion, and subsides with rest. When the narrowing in the artery becomes critical, angina at rest or “unstable” angina may result. Unstable angina can be the harbinger of a heart attack in the near future.

Occasionally the surface of the cholesterol plaque in the artery may rupture, which leads to the formation of blood clot on the surface of the plaque, which then completely occludes blood flow in the vessel and results in a heart attack. The cause of this “plaque rupture” is largely unknown, but contributing factors may include cigarette smoking, elevated LDL cholesterol, elevated levels of blood catecholamines (adrenaline), high blood pressure and other mechanical and biochemical forces.

Coronary Artery Disease (CAD) is the most common underlying cause of a heart attack. CAD is the hardening and narrowing of the coronary arteries by the buildup of plaque in the inside walls (atherosclerosis). Over time, plaque buildup in the coronary arteries can:

Narrow the arteries so that less blood flows to the heart muscle
Completely block the arteries and the flow of blood
Cause blood clots to form and block the arteries.

A less common cause of heart attacks is a severe spasm(tightening) of the coronary artery that cuts off blood flow to the heart. These spasms can occur in persons with or without CAD. Artery spasm can sometimes be caused by: