Heart Attack

Causes

A heart attack occurs when one or more of the arteries (coronary arteries) supplying the heart with oxygen-rich blood become blocked. These arteries encircle the top of the heart like a crown.

Coronary artery blockages are caused by blood clots that form suddenly in a coronary artery that has narrowed over the years from a buildup of cholesterol and other deposits -- collectively known as plaques.

This buildup in the arteries throughout the body is called atherosclerosis (hardening of the arteries.) When coronary arteries narrow due to atherosclerosis, the condition is coronary artery disease.

Coronary artery disease (heart disease) is a major underlying cause of heart attacks. Factors that increase the risk of coronary artery disease -- and the risk for heart attack -- include:

• Family history of heart attacks, heart disease, high blood pressure and high cholesterol
• A high level of "bad" cholesterol, or low-density lipoprotein (LDL) cholesterol, triglycerides, or another blood fat, related to a person's diet.
• Abnormally high levels of homocysteine, C-reactive protein, or fibrinogen in the blood. These have only recently been identified as factors for increased risk of heart disease
• High blood pressure
• Smoking
• Obesity
• Lack of physical activity
• Diabetes
• Unmanageable stress
• Excess alcohol consumption

In rare cases, a heart attack can be caused when a blood clot inside a diseased heart breaks loose and lodges in a healthy or narrowed coronary artery. Another uncommon cause is a spasm of the coronary artery that shuts down blood flow to part of the heart muscle. These life-threatening spasms can be triggered by using drugs such as cocaine.