The heart works 24 hours a day, pumping oxygen and nutrient-rich
blood to the body. Blood is supplied to the heart through its
coronary arteries. If a blood clot suddenly blocks a coronary
artery, it cuts off most or all blood supply to the heart, and a
heart attack results. Cells in the heart muscle that do not
receive enough oxygen-rich blood begin to die. The more time
that passes without treatment to restore blood flow, the greater
the damage to the heart. Having a heart attack is a big wakeup
call for most people. There's usually no problem convincing a
heart attack survivor to change his or her lifestyle-to quit
smoking, control their high blood pressure and cholesterol,
control their weight and get regular physical activity. Each
year, more than one million people in the U.S. have a heart
attack and about half - 515,000 - of them die. Half of those who
die do so within one hour of the start of symptoms and before
reaching the hospital. A heart attack is an emergency. Call
emergency services if you thin