In vivo evaluation of porous vs. skinned polyurethane (PU) - polydimethylsiloxane (PDMS) small-diameter vascular grafts

Distensible, gel-like tubular membranes suitable for small-diameler vascular grafts were labricated by combining techniques for spraying and phase-inversion of thermodynamically unstable solutions of a biocompatible PU-PDMS blend (CARDIOTHANE 51, Kontron Instrumenls, lnc.,USA) over a sliding and rotating mandrel. Two kinds of 1.5 mm ID tubular membranes were fabricated with and wilhout a dense inner polynrer layer (skin). Both types featured a porous, communicating cell wall structufe and an outer porous surface. Tubular membrane segments, 15-20 mm in length, were implanled in the infrarenal abdominal aorta ol 250-300 gram male Sprague-Dawley rats by the same surgeon. Of 10 porous gralts observed for 2 weeks, 7 were patent and exhibited only minimal remnants of thrombosis in the cenlral part of the graft, and no anaslomotic pathology. All 7 skinned grafts observed for the same duration were occluded. None of the skinned grafts observed for shorter periods remained patent beyond 3 days. A series of 3-monlh implants of porous grafts is currently underway. This experiment suggests that inner surface geometry affects the early palency of small-diameter vascular grafts for a given elastomeric material.