When any of the arteries supplying the heart become blocked, a myocardial infarction, or heart attack, will occur if the blockage (or "infarct") is not eliminated quickly. The heart muscle supplied by that artery then becomes starved for oxygen and eventually dies. If the infarct is large enough, the heart's ability to pump blood is compromised, and circulation to all the body's other critical organs is affected. The heart's electrical system may also be adversely affected, resulting in an abnormal rhythm known as ventricular fibrillation. [ad:media]The main cause of myocardial infarction is coronary artery disease (CAD), or a gradual narrowing of the arteries that supply the heart with blood. Eventually, a piece of the fatty plaques affixed to the arteries' inner walls may break free and lodge in a smaller vessel, resulting in total occlusion. CAD affects 3 million Americans and kills more than 700,000 each year; it is the most common life-threatening disease. A blockage that results in a myocardial infarction can also be caused by a bubble of gas or a clot within a blood vessel. But, simply stated, whatever the cause of the occlusion, it means the oxygen required by the heart muscle can no longer be supplied through the blocked vessel. The classic symptoms of myocardial infarction include radiating chest pain (angina) or pain in the jaw or left arm. Other symptoms include heart palpitations; dizziness; indigestion; nausea; sweating; cold, clammy skin; and shortness of breath. If a myocardial infarction is suspected, it is essential that emergency medical care be called and the affected individual evacuated to a hospital. In the meantime, keep the individual calm and administer oxygen. At the hospital, the treatment options include conservative medical management, anticoagulation drugs, heart catheterization or stenting or even coronary artery bypass surgery. Preventing myocardial infarction calls for addressing any risk factors, such as obesity, diabetes, hypertension or smoking. A healthy diet and regular exercise are also important preventatives.