A heart attack (myocardial
infarction,or MI happens when one or more areas of the heart muscle don't get
enough oxygen. This happens when blood flow to the heart muscle is blocked.
The blockage is caused by a buildup
of plaque in the arteries (atherosclerosis). Plaque is made up of depositsof
cholesterol and other substances. When a plaque breaks (ruptures), a blood clot quickly
forms. The blood clot is the actual cause of the heart attack.
If the blood and oxygen supply is cut off, muscle cells of the heart begin to suffer damage and start to die. Irreversible damage begins within 30 minutes of blockage. The result is heart muscle affected by the lack of oxygen no longer works as it should.