Extensive deendothelialization and thrombogenicity in routinely prepared vein grafts for coronary bypass operations: facts and remedy

The objective of this study was to gain deeper insight into the early reasons for saphenous vein graft disease and to find a practical approach to obviate it. Intraoperative storage of freshly explanted venous grafts (45 min, 20 degrees C; n=25 in each case) in saline, saline + 5% albumin, or HTK-solution and also in heparinized autologous blood was poorly tolerated by the endothelium. Large endothelial areas (mostly >75% of total surface) were detached already during brief non-pulsatile flushing just before the transplantation. Contact of deendothelialized areas in graft remnants with defined mixtures of coagulation factors or blood (n=11-17) caused rapid coagulatory processes via expression of tissue factor and assembly of prothrombinase in the subendothelium. Attached platelets and leukocytes accelerated the procoagulatory processes further, and endothelium-dependent anticoagulatory activities were significantly abolished. During pulsatile arterial flow, the resulting blood clots exacerbated the damage of the intima markedly, because they were flushed away tearing off further endothelium. In contrast, storage of venous grafts in a plasma preparation freed from isoagglutinins and coagulation factors preserved the endothelium, which resisted arterial flow and revealed anticoagulatory activity in the presence of antithrombin III and/or protein C. We conclude that gentle preparation and preservation of the vascular endothelium with a suitable storage solution during bypass surgery is a decisive first step to obviate saphenous vein graft disease.