Heart attack is the death of a segment of heart muscle caused by the loss of blood supply. The blood supply is usually lost because a coronary artery, one that supplies blood to the heart muscle, has a blood clot, a blockage (coronary thrombosis). If some of the heart muscle dies, the patient experiences chest pain and electrical instability of the heart muscle tissue.
Another name for a heart attack is myocardial infarction, cardiac infarction and coronary thrombosis (Infarction = the process whereby an area of dead tissue is caused by a loss of blood supply). Blood supply to the heart can also be undermined if the artery suddenly narrows, as in a spasm.