INFLUENCE OF EXTERNAL STENT SIZE ON EARLY MEDIAL AND NEOINTIMAL THICKENING IN A PIG MODEL OF SAPHENOUS-VEIN BYPASS-GRAFTING

Background Late saphenous vein graft failure results from intimal and medial thickening due to migration and proliferation of vascular smoot h muscle cells and superimposed atheroma. These changes may represent an adaptation by the vein to its insertion into the arterial system. U sing a porcine model of arteriovenous bypass grafting, we recently dem onstrated that supporting the graft with a nonrestrictive external Dac ron velour stent significantly reduced intimal hyperplasia and total w all thickness. In the present study, we investigated the influence of different external stent sizes on graft wall dimensions and cell proli feration. Methods and Results Three stent sizes were tested: mildly re strictive, nonrestrictive, and oversized (5, 6, and 8 mm in diameter, respectively). Four weeks after grafting, total wall thickness was dec reased 40% by 5-mm stents (P=.02), 66% by 6-mm stents (P=.0004), and 8 1% by 8-mm stents (P=.02 versus unstented grafts). Neointimal thicknes s was reduced almost 62% by 6-mm and 72% by 8-mm stents (both P=.01) b ut not by 5-mm stents. As a result, the encroachment of the intima int o the lumen was reduced approximate to 70% by 6- or 8-mm stents (P=.02 and P=.01 versus unstented grafts, respectively). Both neointimal and medial cell proliferation were significantly reduced by all three ste nts compared with unstented grafts. Conclusions External stenting of s aphenous vein bypass grafts reduces early intimal and medial hyperplas ia. Oversized stents give equally profound suppression of intimal thic kening, obviating the need for precise size matching with the graft an d greatly simplifying the surgical procedure.