A heart attack, sometimes called a myocardial infarction, is a medical emergency that happens when the heart's blood supply is abruptly cut off, frequently by a blood clot. This has the potential to be fatal and cause significant damage to the heart muscle. It may result in anxiety, weakness, shortness of breath, and chest pain. Chest pain, however, is not always associated with a heart attack, and it can occasionally be misdiagnosed as dyspepsia.