Structural Protection of the Myocardial Capillary Endothelium By Different Forms of Cardiac Arrest and Subsequent Global Ischemia at 5°C

Abstract

Background: In transplantation surgery sufficient myocardial protection achieved 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-reflow phenomenon" during reperfusion, resulting in insufficient cardiac resuscibility. Methods: We evaluated the endothelial ultrastructure after various common forms of cardiac arrest and subsequent ischemia in deep hypothermia. Canine hearts were arrested by aortic cross clamping and surface cooling with Tutofusin® (ACC) or by coronary perfusion with Custodiol® (histidine tryptophane ketoglutarate, HTK solution), with University of Wisconsin solution (UW), or with St. Thomas' Hospital solution. After extirpation the hearts were incubated at 5ºC in the solution used for cardiac arrest. Myocardial samples were taken immediately after cardiac arrest and after 2 h, 4 h, 6 h, and 10 h of global ischemia. The degree of structural damage was evaluated by a scoring system. Endothelial swelling was determined as the mean barrier thickness of the capillary endothelium. Results: At all selected time points our results show that 1) after cardioplegia with St. Thomas' solution, the degree of endothelial cell swelling was higher than after aortic cross clamping; 2) using HTK or UW solution, the endothelial ultrastructure was better preserved than after aortic cross clamping or using St. Thomas' solution, whereby HTK was slightly better than UW; 3) using UW solution, endothelial cell swelling was a little (up to 10%) but significantly less than after HTK perfusion. Conclusions: With respect to the intraischemic structural preservation of endothelial cells, UW or HTK Solution combined with deep hypothermia promises adequate protection, compared with other clinically used methods tested.

Key words

Heart - Capillaries - Endothelium - Ultrastructure - Stereology - Cardioplegic solutions