What is a heart attack?

A heart attack occurs when the blood supply to the heart is cut off.  The most common cause is disease of the coronary arteries, the large blood vessels that feed blood to the muscle that is the heart.  Without good blood flow, the heart muscle is harmed and can even die.  The diagram below shows the heart and several of the blood vessels on its front side.  The smaller diagrams show cross sections of normal and obstructed blood vessels.

What are symptoms of a heart attack? Chest pain Chest tightness Numbness Shortness of breath Nausea and vomiting

Diagram from the National Heart, Lung, and Blood Institute

What should I do if I think I'm having a heart attack?