Effect of porosity on small-diameter vascular graft healing

Experimental studies have reported that complete healing of small-diameter expanded polytetrafluoroethylene (ePTFE) grafts occurs only if the porosity of the graft is increased, thereby allowing ingrowth of perigraft capillaries yielding endothelial cells. This study investigates the effects of varied graft porosity on the healing characteristics of 2-mm internal diameter (ID) ePTFE grafts interposed in the rabbit common carotid artery. Four groups were evaluated: Group A (n = 8) standard (30-microm pores) ePTFE grafts; Group B (n = 8) increased porosity (60-microm pores) ePTFE grafts; Group C (n = 8) standard ePTFE; and Group D (n = 8) 60-microm ePTFE external graft surface was externally coated with an impermeable layer of polyurethane. Patency was 100% for all groups at 8 weeks. At explantation, the neointima was composed of primarily modified smooth muscle cells. Endothelial cells were only identified at the perianastomotic region using the endothelial cell-specific antibody CD31. The impermeable external polyurethane coating of ePTFE grafts had no effect on neointima formation, regardless of porosity.