The Full form of MI is Myocardial Infarction. MI is the medical name for a heart attack. A heart attack occurs when blood flow to the heart muscle is abruptly cut off, causing tissue damage and makes a life-threatening condition. Usually, this is the result of a blockage in one or more of the coronary arteries. A blockage can develop due to a buildup of plaque, a substance mostly made of fat, cholesterol, and cellular waste products. While the classic symptoms of MI (a heart attack) are shortness of breath and chest pain, the symptoms can be quite varied. The most common symptoms of a heart attack include pain in the chest, back, jaw, and other areas of the upper body that lasts more than a few minutes or that goes away and comes back, pressure or tightness in the chest, shortness of breath, sweating, nausea, vomiting, anxiety, a cough, dizziness or a fast heart rate. In your cardiovascular system, your heart is the main organ which includes different types of blood vessels. When these arteries become narrowed or blocked due to a buildup of plaque, the blood flow to heart can decrease significantly or stop completely. This causes Myocardial Infarction (MI).