Morphometric evaluation on myocardial protection of cold crystalloid versus warm blood cardioplegia.

Twenty patients undergoing open-heart valve replacement were divided randomly into two groups in this study; intermittent perfusion of cold crystalloid (St. Thomas Hospital solution) with hypothermic cardiopulmonary bypass (CPB) (hypothermic group) and continuous administration of warm blood cardioplegia with normothermic CPB (normothermic group) respectively. Tissue samples were taken from the right atrium before weaning from CPB and from the right appendage 30 minutes after removal of the cross-clamp. The results of pathological study in these two groups were as follows: the structural alterations were most severe during the ischemic period in the hypothermic group. Damages of the myocardial