Structural protection of the myocardial capillary endothelium by differentforms of cardiac arrest and subsequent global ischemia at 5 degrees C

Background: In transplantation surgery sufficient myocardial protection ach ieved by cardioplegic cardiac arrest and deep hypothermia is a prerequisite for successful resumption of donor heart function. Intraischemic damage of the endothelium combined with capillary compression may lead to the "no-re flow phenomenon" during reperfusion, resulting in insufficient cardiac resu scibility. Methods: We evaluated the endothelial ultrastructure after vario us common forms of cardiac arrest and subsequent ischemia in deep hypotherm ia. Canine hearts were arrested by aortic cross clamping and surface coolin g with Tutofusin(R) (ACC) or by coronary perfusion with Custodiol(R) (histi dine tryptophane ketoglutarate, HTK solution), with University of Wisconsin solution (UW), or with St. Thomas' Hospital solution. After extirpation th e hearts were incubated at 5 degrees C in the solution used for cardiac arr est. Myocardial samples were taken immediately after cardiac arrest and aft er 2h, 4h, 6h, and 10h of global ischemia. The degree of structural damage was evaluated by a scoring system. Endothelial swelling was determined as t he mean barrier thickness of the capillary endothelium. Results: At all sel ected time points our results show that 1) after cardioplegia with St. Thom as' solution, the degree of endothelial cell swelling was higher than after aortic cross clamping; 2) using HTK or UW solution, the endothelial ultras tructure was better preserved than after aortic cross clamping or using St. Thomas' solution, whereby HTK was slightly better than UW; 3) using UW sol ution, endothelial cell swelling was a little (up to 10%) but significantly less than after HTK perfusion. Conclusions: With respect to the intraische mic structural preservation of endothelial cells, UW or HTK solution combin ed with deep hypothermia promises adequate protection, compared with other clinically used methods tested.