Heart Disease Home > Causes of Heart Attack

Underlying causes of heart attacks include a blocked coronary artery in people with heart disease and, less commonly, a spasm in a coronary artery that completely closes it. When a narrowed or blocked artery is involved, the blockage is most often the result of a blood clot; however, the buildup of plaque on the artery walls can also narrow or block the artery.

What Causes a Heart Attack?

The cause of a heart attack (also known as a myocardial infarction) is a severely narrowed or completely blocked coronary artery that causes a decrease in oxygen and nutrients to the heart. Without oxygen and nutrients, heart muscle dies.
 
In most cases, the underlying cause of a blocked coronary artery is a blood clot in people with coronary artery disease (known to most people as simply heart disease). Less commonly, the underlying cause is a spasm in a coronary artery that completely closes the artery.
 

Why a Narrowed or Blocked Artery Causes a Heart Attack

Like any muscle, the heart needs a constant supply of oxygen and nutrients, which are carried to it by the blood in the coronary arteries. The coronary arteries can become narrowed or clogged by cholesterol and fat deposits known as plaque. This buildup of plaque is called atherosclerosis. With atherosclerosis, the coronary arteries cannot supply enough blood to the heart, and the result is coronary heart disease (CHD). If not enough oxygen-carrying blood reaches the heart, you may experience chest pain called angina. If the blood supply to a portion of the heart is severely reduced or completely cut off by blockage of a coronary artery, the muscle cells of the heart suffer irreversible injury and die. This condition is known as a heart attack.
 
The most common cause of a blocked coronary artery is a blood clot forming in an artery that is already narrowed from heart disease. Also, a coronary artery can be blocked simply from the buildup of plaque over time.
 
A less common underlying cause of a heart attack is a severe spasm of a coronary artery that cuts off blood flow to the heart. These spasms can occur in people with or without heart disease. Artery spasms can sometimes be caused by:
 
  • Certain drugs, such as cocaine
  • Exposure to cold
  • Emotional stress
  • Cigarette smoking.
     
Written by/reviewed by:
Last reviewed by: Arthur Schoenstadt, MD
Last updated/reviewed:
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