Novel synthetic selectively degradable vascular prostheses: A preliminary implantation study

Background. Vascular grafts perform less well than autologous arterial or v ein grafts. The purpose of this study was to evaluate the short-term perfor mance of selectively biodegradable filament-wound vascular prostheses, comp rising elastomeric poly(ether urethane) (Lycra) scaffolds and flexible, hyd rophilic biodegradable coatings. Materials and methods. Two types of selectively biodegradable vascular graf ts were manufactured, comprising a filament-wound Lycra scaffold, subsequen tly coated with a biodegradable poly(ethylene glycol)/ poly(lactic acid) (P ELA) block copolymer. The two types of grafts differed in both the overall porosity of the scaffold and the hydrophilicity of the biodegradable consti tuent. A 60-mm-long and 6-mm-diameter filament-wound and polytetrafluoroeth ylene (ePTFE) grafts were implanted as interposition prostheses, randomly, at the right- and left-side carotid arteries. Results. Implantation studies proved the grafts to be patent and pulsatile for periods of up to 3 months. Increasing the scaffold porosity and enhanci ng the hydrophilicity of the biodegradable component improved both the tran smural tissue ingrowth process and the vascularization of the prosthesis wa ll. Also, a well-adhered peripheral tissue and a thin, uniform intima and e ndothelial lining were obtained. All ePTFE graft controls, although patent, were rather stiff and nonpulsati le. A thick pseudointima, poorly attached to the prosthesis inner surface, was observed. The compliance of the wet grafts was significantly higher than in the dry s tate, stemming mainly from the water-plasticizing effect on the biodegradab le component. The grafts explanted after a period of 6 weeks exhibited comp liance only slightly lower than that of the wet grafts. After 12 weeks, how ever, the hoop compliance was 20% lower than that prior to implantation. At 100 mm Hg, for example, the original compliance of the wet graft was 2.5%/ 100 mm Hg decreasing to 2.0%/100 mm Hg after a 3-month implantation. The co mpliance reduction with implantation is attributed to the ingrowth of the p erigraft tissue as revealed by the histological study. A compliance of 2.0% /100 mm Hg is slightly better than that of a standard PTFE graft with an or iginal compliance of 1.6%/ 100 mm Hg. Yet it is still an order of magnitude smaller than that of a canine carotid artery. Conclusions. The improved mechanical properties and enhanced healing of the highly porous filament wound Lycra scaffold graft coated with hydrophilic biodegradable PELA has the potential of being a highly effective small cali ber prosthetic graft. (C) 2000 Academic Press.