Death of a section of heart muscle when its blood supply is cut off, usually by a blood clot in a coronary artery narrowed by atherosclerosis. Hypertension, diabetes mellitus, high cholesterol, cigarette smoking, and coronary heart disease increase the risk. Symptoms include severe chest pain, often radiating to the left arm, and shortness of breath. Up to 20percnt of victims die before reaching the hospital. Diagnosis is done by electrocardiography and by analysis for enzymes in the blood. Treatment aims to limit the area of tissue death (infarct) and prevent and treat complications. Thrombolytic (clot-dissolving) drugs may be administered. Beta-blockers alleviate pain and slow the heart rate. Angioplasty or coronary bypass restores blood flow to heart muscle. Follow-up may include drugs, exercise programs, and counseling on diet and lifestyle changes.

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