Morphologic studies in saphenous vein grafts for aorto-coronary bypass surgery. Part I: Morphology of the Graft using ordinary surgical preparation techniques.

Vein bypass grafts in 8 patients were examined by light microscopy (LM) only or, in addition, by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) before stretching, after stretching and immediately before implantation. Before stretching, the endothelium showed only discrete changes and detachment of the endothelium was rare. After stretching severe endothelial damage was evident, including loss of large areas of endothelium and extensive endothelial tears. Before implantation there had been an extension of the tears and the endothelial detachment in individual preparations. The most important factor causing damage is stretching of the vein. The incubation medium may also play a significant role. Damage incurred before operation or during removal, and hypoxia are of lesser importance. By avoiding endothelial damage it should be possible to limit the occurrence of early postoperative thrombosis and possibly severe late changes as well.