NONPOROUS EXPANDED POLYTETRAFLUOROETHYLENE GRAFTS REDUCES GRAFT NEOINTIMAL HYPERPLASIA IN DOG AND BABOON MODELS

Purpose: Neointimal hyperplasia frequently develops after placement of prosthetic vascular grafts and is a major cause of graft failure. Thi s study was an attempt to prevent vascular lesion formation by coating the graft luminal surface with a thin layer of nonporous silicone pol ymer, and subsequently with an ultrathin layer of vapor phase (plasma gas)-deposited fluoropolymer, thereby providing a smooth and chemicall y uniform surface that was postulated to limit pannus tissue ingrowth across the graft anastomoses. Methods: Bilateral femoral arteriovenous (AV) conduits were constructed in four dogs using expanded polytetraf luoroethylene graft materials (ePTFE; 6-mm inside diameter, 2.5-cm lon g). In each animal, one femoral AV shunt was constructed from a graft whose luminal surface was entirely coated with polymer. On the contral ateral side, an uncoated graft served as a control. Bilateral aortoili ac grafts were placed in three baboons using 5-cm segments of ePTFE (4 -mm inside diameter). One end (1 cm) of each graft had been coated wit h polymer In each animal, the coated end of one graft was placed proxi mally and the coated end of the second graft was placed distally in th e contralateral vessels. Results: All grafts were patent at 30 days. I n the dog model, there was a significant reduction in graft neointimal area at the venous anastomoses for the coated grafts compared with th e uncoated grafts (0.03 +/- 0.02 mm(2) and 1.11 +/- 0.54 mm2, respecti vely; p < 0.05). In the baboon model, the silicone coating significant ly reduced the graft neointimal thickness (0.003 +/- 0.003 mm vs 0.21 +/- 0.05 mm; P < 0.05) and neointimal area (0.05 +/- 0.08 mm2 vs 0.82 +/- 0.58 mm2; p < 0.05). Conclusions: These data demonstrate that heal ing of ePTFE grafts can be effectively modified by altering the physic al properties of the graft surface. Neointimal hyperplasia within ePTF E grafts is significantly reduced by the local application of a fluoro carbon-coated, silicone-based polymer. The resulting graft now surface effectively prevents tissue ingrowth from the adjacent native vessel, thereby preserving the anastomosis luminal area. This approach could represent a new strategy for limiting graft surface anastomotic neoint imal hyperplasia.