Also known as a myocardial infarction, a heart attack occurs when blood flow to part of the heart muscle (myocardium) becomes blocked. If the blood flow is cut off for more than a few minutes, this muscle’s cells begin to die from lack of oxygen.

The most common cause of heart attacks is coronary artery disease (CAD). CAD results from atherosclerosis, a condition in which a fatty substance called plaque builds up on the inside walls of the coronary arteries, the large vessels that supply blood to the heart.

Eventually, plaque can rupture, and after the body repairs the site, a blood clot can form. If the clot becomes large enough, it can either partly or completely block the artery, resulting in a heart attack.

The extent of damage to the heart depends on how long the heart muscle is deprived of oxygen. If blood flow is not restored within 20 to 40 minutes, the heart muscle will begin to suffer irreversible damage, which leads to scarring. Over time, this can lead to complications such as heart failure and life-threatening arrhythmias.