Most heart attacks occur as a result of
coronary artery disease (CAD). CAD is the buildup over time of a material
called plaque on the inner walls of the coronary arteries. Eventually, a
section of plaque can break open, causing a blood clot to form at the site. A
heart attack occurs if the clot becomes large enough to cut off most or all of
the blood flow through the artery.
Coronary Artery With Plaque
Buildup
The illustration shows a normal
artery with normal blood flow (figure A) and an artery containing plaque
buildup (figure B).
The blocked blood flow prevents oxygen-rich blood
from reaching the part of the heart muscle fed by the artery. The lack of
oxygen damages the heart muscle. If the blockage isnt treated quickly,
the damaged heart muscle begins to die.
Heart attack also can occur due to problems with the
very small, microscopic blood vessels of the heart. This condition is called
microvascular disease. Its believed to be more common in women than in
men.
Another less common cause of heart attack is a
severe spasm (tightening) of a coronary artery that cuts off blood flow through
the artery. These spasms can occur in coronary arteries that dont have
CAD. Its not always clear what causes a coronary artery spasm, but
sometimes it can be related to:
Taking certain drugs, such as cocaine
Emotional stress or pain
Exposure to extreme cold
Cigarette smoking
The animation below shows how a heart attack occurs.
Click the start button to play the animation. Written and spoken
explanations are provided with each frame. Use the buttons in the lower right
corner to pause, restart, or replay the animation, or use the scroll bar below
the buttons to move through the frames.
The animation shows how blood flow
is blocked in the heart, leading to a heart attack.