A heart attack, also known as an MI for myocardial infarction occurs when the blood supply to a part of the heart muscle is seriously decreased or stops. The blood flow decrease or stoppage happens when there is a blockage in one or more of the coronary arteries that take blood to the heart muscle. This tends to occur due to plaque accumulation, which is called arteriosclerosis (or atherosclerosis). Plaque can break off and cause a blood clot and block the artery. This causes the heart attack. The blockage of a coronary artery can also be referred to as coronary thrombosis or coronary occlusion.  If blood stops for more than a few minutes, the muscle cells are permanently damaged and die. Depending on how much the heart muscle has been damaged, this damage can cause the patient to die or become seriously disabled.  Most hospitals have special protocols to treat heart attack victims as quickly as possible by doing an emergency angiogram with an angioplasty or stent to open up the blocked artery.