Autogenous vein bypass grafts: biological effects of mechanical dilatation and adventitial stripping in dogs.

To evaluate whether mechanical vein dilatation and stripping of adventitia at the time of harvest may adversely alter the long-term fate of autogenous vein grafts, dogs were subjected to reversed femoral vein interposition grafting with either normal veins, mechanically dilated veins, or adventitially stripped veins. Vein segments taken before grafting and veins exposed in situ but not grafted served as controls. Animals were killed at 3 months, and five vein segments in each category were evaluated for gross and microscopic changes. All grafts subjected to arterial interposition displayed marked neointimal proliferation and fibrosis of the media and adventitia. Notably, both dilated and stripped veins appeared to be similar and were indistinguishable from normal veins that had been subjected to arterial interposition for the same duration. Veins exposed in situ but not subjected to arterial flow remained essentially normal. Adverse alterations attributed to vein dilatation or adventitial stripping were not apparent and should not be invoked in the mechanism of graft failure at 3 months' duration.