Arterial autografts and PTFE vascular microprostheses: similarities in the healing process

A comparative study has been carried out dealing with the vascular healing process in two experimental vascular graft models to determine the differences or similarities between the two. One of the models consisted of the use of arterial autografts and the other of the implantation of vascular microprostheses of polytetrafluoroethylene (PTFE). The common iliac artery of female Sprague-Dawley rats was used. The length of the grafts in both models was 5 mm. A microsurgical technique was employed, and anticoagulant and antibiotic therapies were not used. The results were studied using light microscopy, transmission and scanning electron microscopies, autoradiography, and immunohistochemistry. A patency of 100% was obtained in the arterial autografts, and 87.6% in the PTFE implants. The histopathological findings were as follows: a) the mechanisms of immediate postgrafting response were similar, with marked presence of fibrin and platelet deposition in the form of a nonthrombogenic monolayer; b) a "neoadventitia" formed over the implant in both models; c) the endothelialisation was complete in both types of grafts 2 to 3 weeks after implantation; d) an intimal hyperplastic response appeared in both, although at different times (in the first week in the autografts and at one month with the PTFE); e) white cell accumulation was significantly greater on the PTFE luminal surface than on the autograft. The intimal hyperplasia was formed mainly by secretory myocytes in the autografts, while in the PTFE implants, fibrosis predominated.