What Is a Heart Attack?

Medically Reviewed

If you are like most people over age 50, having a heart attack is probably one of your major health concerns—and understandably so. Heart attacks remain the leading cause of death among Americans.

Each year, about 635,000 people in the United States have a heart attack for the first time, and 300,000 have a repeat attack.

What is a heart attack?

Like every other organ, your heart needs its own supply of oxygenated blood. It receives this supply through the coronary arteries.

In a healthy heart, blood flow through the coronary arteries increases to meet the heart’s demand for oxygen. For example, the heart needs more oxygen during exercise than at rest.

But as we age, the coronary arteries become thickened and narrowed (atherosclerosis) and are less able to respond to increased oxygen demands. When atherosclerosis impairs blood flow to the heart, the result is a condition called coronary heart disease (also known as coronary artery disease).

What happens during a blockage

Heart attacks, which doctors call myocardial infarctions, typically occur in people with coronary heart disease when a coronary artery becomes completely blocked by a blood clot. This blockage cuts off the blood supply to the muscular layer of the heart’s wall (myocardium), which plays a crucial role in the heart’s pumping action.

Such a blockage can produce crushing pain or pressure in the middle of the chest as well as tissue death (infarction) in the portions of the heart muscle normally supplied by that coronary artery.

Many people who suffer a heart attack have angina (episodes of pain, pressure or squeezing in the chest caused by an inadequate blood supply to the heart because of narrowed coronary arteries) and may experience more frequent or severe pain in the days leading up to a heart attack. Other people, particularly women and older men, may experience less obvious warning signs.

In many cases, however, a heart attack strikes suddenly and without warning in individuals who think they are healthy. Many of these people haven’t been to a doctor in years and don’t realize that their arteries have sustained damage from high blood pressure or high cholesterol levels.

Once the heart muscle is deprived of oxygen, irreparable damage can develop within 20 to 30 minutes. In fact, half of the deaths from heart attacks occur within the first hour, making immediate medical attention critical.

Learn How to Prevent a Heart Attack and Symptoms of Coronary Heart Disease.