When a section of the heart muscle doesn’t get enough blood, it causes a heart attack, also known as a myocardial infarction. The longer the heart muscle goes without treatment to restore blood flow, the more damage it sustains. The most common cause of heart attack is coronary artery disease (CAD). A strong spasm, or sudden contraction, of a coronary artery, which can block blood flow to the heart muscle, is a less common reason. Pain or discomfort in the chest. Most heart attacks are characterized by pain in the center or left side of the chest that lasts longer than a few minutes or that disappears and reappears. Uncomfortable pressure, squeezing, fullness, or pain are all possible sensations. If you or someone you know is experiencing symptoms of a heart attack, call 911 right once. The sooner you go to an emergency room, the sooner you can begin therapy to minimize heart muscle damage. At the hospital, doctors can do tests to see if a heart attack is occurring and choose the best course of action. A heart attack may either cardiopulmonary resuscitation (CPR) or an electrical shock to the heart (defibrillation) to get the heart working again. Bystanders who have been trained to perform CPR or use a defibrillator may be able to assist until emergency medical help arrives. Remember that the sooner emergency treatment begins, the greater your chances of surviving a heart attack.