Heart Attack : FAQs
Myocardial infarction (mi): Heart attack 

How is it caused?
A heart attack is caused by the formation of a blood clot on a cholesterol plaque located on the inner wall of an artery that supplies the heart (coronary artery). Cholesterol plaque is caused by deposits of cholesterol in the artery walls and is a process that begins as early as in the late teens. Over the period of time, the accumulation of cholesterol plaque causes thickening of the artery walls and resultant narrowing of the arteries; a process called asatherosclerosis. Smoking, high blood pressure, elevated cholesterol, and diabetes can accelerate plaque formation. Ultimately, atherosclerosis causes significant narrowing of the coronary arteries to the extent that the blood supply to the heart muscle is compromised. 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. When the narrowing in the artery becomes critical, angina (heart pain) may result leading over time to a heart attack.

Occasionally the surface of the cholesterol plaque in the artery may rupture (tear away), 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 cholesterol, elevated levels of blood catecholamines (adrenaline), high blood pressure, and other mechanical and biochemical forces.

Unlike angina (heart pain), death of the heart muscle from a heart attack is permanent.


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