Ultrastructural change in myocardium subsequent to ischemic cardioplegia "no-reflow phenomenon".

Mongrel dogs were subjected to cardiopulmonary bypass with hemodilution and to normothermic anoxic arrest for 30 minutes, to study the subepicardial and the subendocardial myocardial ultructure and the DPTI/TTI ratio. "No-reflow phenomenon" was demonstrated in the myocardium after cardiopulmonary bypass, associated with normothermic anoxic arrest. No-reflow phenomenon was a contributing factor to subendocardial ischemia in the normotrophied ventricle after open-heart surgery. Severe hemodilution with hemoglobin less than 5.0 g% resulted in irreversible damage in both myocardial layers.