A heart attack happens when blood flow to the heart is blocked. Without blood and the oxygen it carries, part of the heart starts to die. The medical name for a heart attack is myocardial infarction, or MI. It may also be called acute coronary syndrome.

A heart attack is often the result of coronary artery disease, in which fatty deposits called plaque (say "plak") build up inside the heart arteries. When plaque breaks open or ruptures, it can form a clot that blocks blood flow to the heart muscle.

Quick treatment that restores blood flow to the heart can help save lives.