Myocardial infarction, commonly known as a heart attack, occurs when blood supply to the heart is reduced or stopped, causing damage to heart muscle. It is usually caused by a blood clot forming in one of the coronary arteries due to a buildup of fatty plaques called atheroma within the artery walls over many years. Risk factors that can increase the chances of a heart attack include high blood pressure, obesity, diabetes, smoking, high cholesterol, excessive alcohol, and stress. Signs and symptoms of a heart attack include chest pain or discomfort that may spread to the shoulders, neck, arms, back, or jaw.