Heart Attack and Atherosclerosis Prevention (cont.)
What is angina pectoris?
Angina pectoris is
chest pain or pressure that occurs when the oxygen supply to the heart muscle
cannot keep up with oxygen consumption by the heart muscle. (Oxygen consumption
by the heart muscle increases with physical exertion or excitement and decreases
with rest and relaxation.) Most commonly, the inadequate supply of oxygen is due
to narrowing of the coronary arteries by atherosclerosis. When coronary arteries
are narrowed by more than 50% to 70%, the arteries cannot increase the supply of
blood to the heart muscle during exertion or other periods of high oxygen
demand. An insufficient supply of oxygen to the heart muscle causes chest pain
(angina). Chest pain that occurs with exercise or exertion is called exertional
angina.
What is a heart attack?
A heart attack
(myocardial infarction) is the death of heart muscle due to the sudden and
complete blockage of a coronary artery by a blood clot. A coronary artery
blockage usually occurs in arteries that contain cholesterol plaques. A plaque
can rupture and initiate the formation of a blood clot next to it. A blood clot
can completely block blood flow through a coronary artery and deprive the heart
muscle of needed nutrients and oxygen. The heart muscle then dies, which
produces a heart attack.
Ventricular fibrillation
A heart attack can trigger the sudden onset of ventricular fibrillation.
Ventricular fibrillation is a chaotic electrical rhythm of the heart that causes
cardiac arrest (the heart stands still and ceases to pump blood). Ventricular
fibrillation causes permanent brain damage and death unless a normal heartbeat
can be restored within five minutes of its onset. Of the one million Americans who
suffer heart attacks annually, approximately 400,000 of them die suddenly and
unexpectedly from ventricular fibrillation before the victims can reach any
medical assistance. For these people, the first sign of coronary heart disease
is sudden, unexpected death.
Next: Heart failure »
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