Causes & Risk Factors for Heart Attack

The primary risk factor for heart attack is coronary heart disease (CHD), also called atherosclerosis. Atherosclerosis is a condition in which plaques (deposits of cholesterol and fatty materials) form in the arteries and partially or completely block blood flow. When a plaque tears or ruptures, a blood clot (thrombus) can form and completely block the flow of blood to the heart. Most heart attacks are caused by a blood clot in a coronary artery.

Many of the risk factors for CHD and subsequent heart attack are related to being overweight. Risk factors include the following:

  • Age (over 55)
  • Diabetes (According to the American Heart Association in June 2014, at least 10 percent of people who suffer a heart attack have undiagnosed diabetes.)
  • Elevated levels of certain amino acids and proteins (e.g., homocysteine, C-reactive protein, fibrinogen)
  • Gender (male)
  • Heredity (family history of heart disease)
  • High blood pressure (hypertension)
  • High fat diet
  • High levels of "bad" (LDL) cholesterol and low levels of "good" (HDL) cholesterol
  • Lack of exercise
  • Smoking
  • Stress (e.g., "type A" or driven personality)

In some cases, heart attack is caused by a severe spasm (contraction) in a coronary artery. During a spasm, the artery narrows and blood flow to an area of the heart decreases or stops. The cause of spasms is unknown, and one can occur in normal arteries as well as those partially blocked by atherosclerosis.

The following also may cause heart attack:

  • Complications from bypass surgery or cardiac catheterization
  • Congenital heart conditions (i.e., conditions present at birth)
  • Coronary embolization (blood clot from elsewhere in the body that breaks away and travels to the heart)
  • Drug abuse (e.g., cocaine use may impede blood flow in the heart)
  • Inflammatory artery disease (indicated by the presence of markers in the blood such as interleukin-18 [IL-18] or C-reactive protein [CRP])
  • Trauma (cut, severe blow, or stab wound to the heart)

Some studies have shown that air pollution may increase risk for heart attack, stroke and cardiovascular disease.

About one-quarter of all heart attacks occur without producing any identifiable symptoms. These so-called "silent" heart attacks may only be discovered incidentally by examination of an electrocardiogram (EKG) or by other heart test.

Publication Review By: Stanley J. Swierzewski, III, M.D.

Published: 02 Jul 2000

Last Modified: 04 Jun 2014