A heart attack takes place when one or more coronary arteries (blood vessels that transport blood into and out of the heart) become blocked. The buildup of various substances that block the arteries, such as cholesterol, trigger most heart attacks. During a heart attack, one of the substance buildups can rip apart, spilling cholesterol and other matter into the bloodstream. A blood clot is formed at the site of the rupture and if large enough, may block blood flow into the coronary artery. When tissues don’t receive blood, they immediately begin to deteriorate, so the top priority is to clear the vessel as quickly as possible to restore blood flow. It is a life-threatening emergency; call 911 immediately if you think you or anyone else is experiencing a heart attack.