A heart attack—also called myocardial infarction or MI—occurs
when an area of heart muscle is completely deprived of blood,
and the heart muscle cells die. A heart attack may result when
plaque inside the heart arteries breaks open or ruptures,
forming a clot that significantly blocks blood flow through the
artery. A plaque is made up of cholesterol, white blood cells,
calcium, and other components, and it is surrounded by a fibrous
cap. This fibrous cap may tear or rupture if blood suddenly
flows faster or if the artery suddenly narrows. A tear or
rupture signals the body to repair the injured artery
lining—much as it might heal a cut on the skin—by forming a
blood clot to seal the area. A blood clot that forms in an
artery can completely block blood flow to the heart muscle and
cause a heart attack. Symptoms of a heart attack include: Heart
attack symptoms do not go away with rest or nitroglycerin.
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