When the flow of blood to the heart is blocked—usually due to a buildup of fat, cholesterol, and other substances which form a plaque—a heart attack can occur. In some instances, the plaque can rupture, forming a clot that blocks blood flow and subsequently damaging or destroying a part of the heart muscle. Heart attacks are also known as myocardial infarctions and can potentially be fatal. Treatment for heart attacks has improved significantly over the years, and when you get treatment as quickly as possible, the outcome of your heart attack greatly improves.