Pseudointimal hyperplasia of ridged outer wall polytetrafluoroethylene vascular prostheses

In addition to the polytetrafluoroethylene (PTFE) vascular graft (G) with its conventionally smooth surface, a unique PTFE graft with a ridged outer wall (T) is now also currently available for clinical use. Although an excellent antikinking property is provided by this unique outer structure, the possible influence of the structure on the formation of pseudointima has not yet been investigated in detail. Four kinds of T grafts (3 mm inner diameter, 3 cm long) with various fibril lengths (FL, T-15, T-30, T-60, T-90) and a G graft with 30 microns FL (G-30) were implanted into the inferior vena cava of rabbits. The patency of the grafts at 4 weeks were as follows: 6/8(T-15), 6/8(T-30), 5/8(T-60), 0/8(T-90) and 4/6 (G-30). Pseudointimal hyperplasia (PH) of the T grafts advanced as the FL increased, judging by the thickness of the pseudointima, cellular density, and maturity of fibroblasts. In addition, the maturity of endothelial-like cells on the luminal surface increased as the FL increased. The degree of pseudointimal hyperplasia in G-30 was comparable to that of T-15, although the maturity of the endothelial-like cells was similar to that of T-60. Microscopically, there was a micro-heterogeneity of cellular density in T grafts probably due to the uneven outer structure. In conclusion, not only FL but also the outer structure of PTFE may thus influence the formation of the pseudointima.