Ultrastructure of human myocardium after total cardiopulmonary bypass during open-heart surgery.

During cardiopulmonary bypass surgery without coronary perfusion, most myocardial cells show ischemic lesions of the mitochondria but all other cell organelles remain unchanged. Ischemic damage to the myocardial cells caused by cardiopulmonary bypass surgery for a period of 47 minutes is reversible, since, after 20 minutes of reperfusion of the heart, the first signs of mitochondrial recovery can be observed. Bypass times exceeding 50 minutes cause severe irreversible damage to many myocardial cells.