myocardial infarction

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. The main danger is that of ventricular fibrillation, which accounts for most of the fatalities. Other arrhythmias are also frequent; ectopic beats in the ventricle are especially important as they predispose to ventricular fibrillation. Other complications include heart failure, rupture of the heart, phlebothrombosis, pulmonary embolism, pericarditis, shock, mitral regurgitation, and perforation of the septum between the ventricles.

The best results from the management of patients with myocardial infarction follow mobile and hospital-based coronary care 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) and is relieved by the intravenous infusion of a drug to dissolve thrombus (thrombolysis) or by emergency coronary angioplasty. 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.