Conventional versus high-porosity polytetrafluoroethylene grafts: clinical evaluation

In baboons, nonreinforced (unwrapped) 60 microns internodal distance polytetrafluoroethylene grafts form a complete endothelial lining within 2 weeks by capillary ingrowth through the wall. Smooth muscle cells then grow under the endothelium and proliferate to form a complete neointima. To determine if spontaneous endothelialization of these grafts can also occur in humans, 10 above-knee femoropopliteal grafts composed of equal lengths of 60 and 30 microns polytetrafluoroethylene were placed in eight patients. These grafts were reinforced (wrapped) for human use. Because biopsy of the grafts was not possible, endothelialization was assessed noninvasively by 111In-labeled platelet imaging 1 week and 3 months after surgery. There was no difference in indium uptake between 60 and 30 microns segments at either time. Histologic sections were available from 60 microns segments of two patients who underwent operation for graft thrombosis. Capillary ingrowth was seen in these grafts, but it rarely extended more than half the distance from the outside of the graft to the lumen. Smooth muscle cells were not seen on the flow surface, indicating that a neointima had not formed. These findings demonstrate that capillary ingrowth can occur in 60 microns grafts in humans but does not produce an endothelial lining. The failure to endothelialize is perhaps a result of inadequacy of angiogenesis in adult humans or retardation of capillary ingrowth by the reinforcing wrap.