The underlying cause of nearly all heart attacks is atherosclerosis, the buildup of plaques within the walls of the coronary arteries. Some plaques are unstable and can rupture. When this occurs, a cascade of fast-moving events culminates in the formation of a blood clot at the site of the plaque. Together, the plaque and blood clot can completely block the coronary artery, starving the heart tissue of oxygen and nutrients and ultimately leading to death of portions of the heart muscle.
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