Healing Characteristics of Hybrid and Conventional Polytetrafluoroethylene Vascular Grafts

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Abstract
The concepts of porosity and healing in vascular grafts are interrelated. The initial phase of healing includes cellular infiltration into the prosthesis followed by tissue ingrowth from perigraft sources. This provides a framework for development of a pseudointima. The microstructure of conventional expanded polytetrafluoroethylene grafts with an average internodal distance of 20 microns or less results in hindered cellular penetration and tissue ingrowth. A new microstructure hybrid polytetrafluoroethylene graft is described that has a high porosity 60 microns average internodal distance on the adventitial surface combined with a fine pore 20 microns average internodal distance on the luminal surface. In addition, tapered through-pore channels provide a direct channel from the adventitia and lumen that allow biologic communication to occur where cells and tissue can penetrate and vaginate. Canine carotid and femoral implant studies were performed to elucidate healing effects of polytetrafluoroethylene graft structure on cellular penetration and tissue ingrowth. Enhanced cellularity and tissue ingrowth were observed in hybrid polytetrafluoroethylene implants compared to implants of conventional expanded polytetrafluoroethylene. Human explants also demonstrate enhanced initial cellular penetration and capillary formation in the hybrid polytetrafluoroethylene graft wall. It is postulated that hybrid polytetrafluoroethylene will result in improved clinical performance as a result of removal of the healing restrictions associated with random microstructure conventional expanded polytetrafluoroethylene vascular grafts.

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