Heart Attack!! - A heart attack (also known as a myocardial infarction) is the death of heartmuscle from the sudden blockage of a coronary artery by a blood clot. Coronaryarteries are blood vessels that supply the heart muscle with blood and oxygen.Blockage of a coronary artery deprives the heart muscle of blood and oxygen,causing injury to the heart muscle. Injury to the heart muscle causes chest painand pressure. If blood flow is not restored within 20 to 40 minutes,irreversible death of the heart muscle will begin to occur. Muscle continues todie for 6-8 hours at which time the heart attack usually is 'complete.' Thedead heart muscle is replaced by scar tissue. Approximately one million Americans suffer a heart attack each year. Fourhundred thousand of them die as a result of their heart attack.