Myocardial infarction Health Dictionary

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.

See HEART, DISEASES OF – Coronary thrombosis.

death of a segment of heart muscle, which follows interruption of its blood supply (see coronary thrombosis). Myocardial infarction is usually confined to the left ventricle. The patient experiences a ‘heart attack’: sudden severe chest pain, which may spread to the arms and throat. Although severe chest pain is the most widely recognized symptom of myocardial infarction, many patients – especially women – do not have chest pain. Other presenting symptoms include abdominal pain, nausea, vomiting, sweating, shortness of breath, and dizziness. The main danger is that of ventricular *fibrillation, which accounts for most of the fatalities. Other *arrhythmias are also frequent. Other complications include heart failure, rupture of the heart, phlebothrombosis, pulmonary embolism, pericarditis, shock, mitral regurgitation, and perforation of the septum between the ventricles.

Patients with myocardial infarction are best cared for in a specialized coronary care unit with facilities for the early detection, prevention, and treatment of arrhythmias and *cardiac arrest. Blockage of a major coronary artery is detected by elevation of the *S–T segment on the *electrocardiogram (STEMI or S–T elevation myocardial infarction). It is relieved by emergency *coronary angioplasty (commonly called primary *percutaneous coronary intervention) or the intravenous infusion of a drug to dissolve thrombus (*thrombolysis). Most survivors of myocardial infarction are able to return to a full and active life, including those who have been successfully resuscitated from cardiac arrest. Lesser degrees of coronary obstruction may not be seen on the electrocardiogram but are revealed by the detection of raised *troponin levels in the blood (NSTEMI or non-S–T elevation myocardial infarction). Treatment is with *antiplatelet drugs and early percutaneous coronary intervention.