An infarction is a blockage of blood circulation to an area or organ of the body which results in tissue death. Infarctions commonly occur in the spleen, kidney, lungs, brain, and heart.
The acute emergency so beloved of TV hospital dramas, myocardial infarction - in layman's terms, a heart attack - is most often caused by a blockage in one of the coronary arteries that supply blood to the heart. The blockage typically occurs when a blood clot (see thrombosis and embolism for arcane distinctions here) lodges in an area already narrowed by arteriosclerosis; there are other causes, such as a viral infection of the heart.
Symptoms of a myocardial infarction include a crushing pain in the chest which may travel to either arm - more commonly the left - the jaw, and the neck. In some cases there are no symptoms at all. The seriousness of the infarction depends on several factors: the amount of heart muscle affected; how long the area has been deprived of blood; and whether the infarction has damaged the natural pacemaker, causing an irregular heartbeat, or arrhythmia. Death of heart muscle tissue and heart failure may result; damage to other vital organs, including the big one, the brain, may occur if the heart cannot pump sufficient oxygen and blood to them.
Treatment of acute myocardial infarction may include first aid in the form of cardiopulmonary resuscitation (CPR) or administration of thrombolytic (clot-dissolving) drugs. Healing occurs through the replacement of the dead tissue by scar tissue. | 
