Neo-endothelialisation of PTFE microvascular grafts: a five-year experience.

This paper presents the results of a 5-year experience of the implantation of 1 mm diameter polytetrafluoroethylene (PTFE) prosthesis in rodents. By evaluating the implanted grafts at different intervals, the process of neo-endothelial healing can be divided into six phases: Platelet Aggregation Phase (Stage I); Fibrin Network Phase (Stage II); Bridging Phase (Stage III); Progression Phase (Stage IV-A); Transmural Migration Phase (Stage IV-B) (only in optimal grafts, with thin wall and long fibril length); Intimal Closure Phase (Stage V); and Endothelial Thromboresistance Phase (Stage VI). Grafts with 60 or 90 microns fibril length offer enough "anchoring space" for the ingrowth of neo-endothelium and they act as a framework for the neo-endothelial invasion. Furthermore, this type of material allows intramural migration and penetration of cellular elements. In particular, a network of capillaries traversing the graft wall and opening eventually on the luminal surface can provide multiple sources of neo-endothelium, contributing to the development of the inner neo-endothelial lining. Scanning electron microscopy can favourably assist in the evaluation of different types of PTFE grafts, with regard to their fibril length, diameter, and wall thickness.