Appearances of myocardial infarct after weeks and months. Myocardial infarction or a heart attack occurs when blood flow to part of the heart is obstructed. This restricts the oxygen to the heart and causes tissue death. Histologically, collagen deposition occurs and the infarct is replaced by a collagenous scar. (See 2Y0199, 2Y0200 and 2Y0426)