Myocardial infarction, also known as heart attack, is a life-threatening condition that occurs when the blood supply to the heart muscle is interrupted. This can damage the heart tissue and cause serious complications. The most common cause of myocardial infarction is a blockage of a coronary artery by a blood clot, which is often the result of a rupture of a fatty plaque. The main symptom of myocardial infarction is chest pain or discomfort, which may radiate to the arm, neck or back. Other symptoms may include shortness of breath, sweating, nausea, dizziness, or fainting.