A heart attack is a life-threatening event in which the supply of blood and oxygen to part of the heart is blocked. Many heart attack victims wait two hours or more after their symptoms begin before they seek medical help. This delay can result in death or lasting heart damage. Quickly seeking treatment for a heart attack may help prevent much or all of the permanent damage a heart attack can cause.
Each year, more than a million people in the United States have a heart attack. About half (515,000) of these people die as a result. About half of those who die do so within one hour of the start of symptoms and before reaching the hospital.
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 heart muscle. 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 of a heart attack is a spasm in a coronary artery that completely closes the artery.