Definition of heart attack
:an acute episode of coronary heart disease marked by the death or damage of heart muscle due to insufficient blood supply to the heart usually as a result of a coronary artery becoming blocked by a blood clot formed in response to a ruptured or torn fatty arterial deposit
Note:
Symptoms of heart attack include discomfort or pain in the chest, shoulder, arm, back, neck, or jaw, shortness of breath, dizziness or light-headedness, heartburn, nausea, excessive sweating, and extreme fatigue.
— called also
myocardial infarction 
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