Preservation of the endothelium in venous bypass grafts: Relevance for graft patency

Veins continue to be a main choice for arterial bypass grafts, but postoperative graft occlusion rates continue to be a problem, with up to 40% of aortocoronary bypass operations in the U.S.A. now being 'redo' or 'revision' procedures. An understanding of the factors contributing to the problem of endothelial pathology, and possible strategies for preventing it, include surgical, pharmacological and molecular factors. The endothelial cell is central to vascular wall biology, coordinating vascular wall modelling through the synthesis of key elements which influence smooth muscle cell behaviour. Removal of the endothelium leads to an imbalance in the components of the vasculature, with proliferation of vascular smooth muscle cells resulting in intimal hyperplasia. Endeavours to preserve endothelial cell presence and function may minimise implantation injury (and subsequent early vein graft failure), and may also minimise intimal hyperplasia (the cause of short to intermediate term vein graft failure). The pathophysiology of vein graft failure is still poorly understood. With the advent of new technologies, it is expected that a rational approach to the prevention of intimal hyperplasia (through methods such as gene transfer) may soon be feasible. Even before the full potential of such new technologies is realised, meticulous and continuous efforts to preserve endothelium at the stages of vein harvest, storage and graft implantation should be implemented to maximise the patency of venous grafts.