Heart attacks result from blood vessel disease in the heart. Coronary heart disease (CHD), sometimes referred to as coronary artery disease (CAD), is a more general name for heart attack (and angina).
A heart attack (or myocardial infarction) occurs when the blood supply to part of the heart muscle itself (the myocardium) is severely reduced or stopped. This occurs when one of the coronary arteries (the arteries that supply blood to the heart muscle) is blocked by an obstruction, often plaque due to atherosclerosis. A heart attack also can be caused by a blood clot lodged in a coronary artery. Such an event is sometimes called a coronary thrombosis or coronary occlusion.
If the blood supply is cut off drastically or for a long time, muscle cells suffer irreversible injury and die. Disability or death can result, depending on how much heart muscle is damaged.
Sometimes a coronary artery temporarily contracts or goes into spasm. When this happens the artery narrows and blood flow to part of the heart muscle decreases or even stops. What causes a spasm is unclear, but it can occur in normal blood vessels as well as vessels partially blocked by atherosclerosis. If a spasm is severe, a heart attack may result.