Sudden death of part of the heart muscle due to a blockage in the blood supply to the heart. The disorder is popularly known as a heart attack. It is usually characterized by severe, unremitting chest pain. Myocardial infarction is the most common cause of death in developed countries. Men are more likely to have a heart attack than women, and smokers are at greater risk. Other risk factors include increased age, unhealthy diet, obesity, and disorders such as hypertension and diabetes mellitus. Atherosclerosis of the coronary arteries is usually a factor. Symptoms include sudden pain in the centre of the chest, breathlessness, feeling restless, clammy skin, nausea and/or vomiting, or loss of consciousness. Myocardial infarction may cause immediate heart failure or arrhythmias. Diagnosis is made from the patient’s history and tests including ECG and measurement of enzymes released into the blood from damaged heart muscle. A myocardial infarction is a medical emergency. Initial treatment may include aspirin, thrombolytic drugs, analgesic drugs, and oxygen therapy. Diuretic drugs, intravenous infusion of fluids, antiarrhythmic drugs, and beta-blocker drugs may also be given. Electrical defibrillation may be used to control severe arrhythmias. After recovery, preventive measures such as taking more exercise, losing weight, stopping smoking, and dietary changes are recommended. Statin drugs are usually given to lower blood cholesterol; aspirin or beta-blocker drugs are given to reduce the risk of further attacks.