Atherosclerosis is a common feature of autogenous vein bypass grafts resulting in their long-term failure. Arterial pressure-induced distension is thought to play a major role in the wall thickening of vein grafts, which may in turn favor atherosclerotic complications. In this study, we evaluated the influence of vein distension on the development of atherosclerotic lesions in jugular vein grafts interposed into the common carotid arteries of rabbits. The proximal half of each vein graft was wrapped with a 4-mm-diameter polytetrafluoroethylene graft that reduced the vein graft diameter by 46 +/- 5%. Fourteen animals were fed a 1% cholesterol-rich diet for 8 weeks, and five animals were fed a normal diet. In normocholesterolemic and hypercholesterolemic animals, the wall thickness and the total cross-sectional area were significantly reduced in wrapped compared with unwrapped segments. Foam cells were never observed in normocholesterolemic animals. In hypercholesterolemic rabbits, the sudanophilic lesions covered 62 +/- 4% of the luminal surface in unwrapped segments and 31 +/- 7% in wrapped segments (p < 0.0001). In transverse sections, the surface areas of foam cells were also markedly reduced in wrapped compared with unwrapped segments. Reduction of the wall distension using a rigid external support protected the vein grafts from atherosclerosis, possibly as a result of the decrease in wall thickening that occurred in response to arterialization.