A heart attack
(MI) occurs when there is a lack of
sufficient blood flow to the heart
, and there is heart muscle damage. Heart muscle damage can occur when there is a blockage of blood supply to the heart by a blood clot. If MI by blood clot, anneurysm, etc. there may be the classic symptoms (pain, etc.), and immediate intervention is required.
A heart attack can happen in a non-emergency type circumstance.