Acute myocardial infarction, more commonly known as heart attack, is a condition in which the blood vessels that supply blood to the heart muscle become blocked. If blood flow is blocked for long enough, a part of the heart muscle dies and is replaced by scar tissue. When large areas of the heart or special areas that control heart rhythms are involved, heart attacks can be deadly. Women younger than 60 years of age are more likely than men younger than 60 years of age to die while in the hospital after suffering a heart attack. This sex difference in death in the hospital following heart attacks does not exist in older patients. It is not known, however, whether women who have had heart attacks do better or worse than men during the years after they leave the hospital.