Microporous Polyurethane Inhibits Critical Mural Thrombosis and Enhances Endothelialization at Blood-Contacting Surface

This study addresses a long-lasting controversv, "Which is a better blood-contacting surface morphology, smooth or rough?" and indicates the importance of micropores penetrating through the graft wall in minimizing thrombosis. Four types of spongy polyurethane-polydimethvlsiloxane (Cardiothane 51: Kontron Instruments, Everett, MA. USA) vascular grafts (PUG). l.5 mm ID and l.5-2 cm in length, fabricated by a sprav, phase-inversion technique, were implanted end-to-end in the infrarenal aorta of 58 adult rats. Some grafts had a continuous inner skin and, consequently, a hydraulic permeability of 0 ml/min per cm2 (PUG-S-0). Some had an inner skin with isolated pores and a mean hydraulic permeability of 11ml/min per cm2 (PUG-S-11). Some had a microporous luminal surface with a mean hydraulic permeability of either 2.7 ml/min per cm2 (PUG-2.7) or 39 ml/min per cm2 (PUG-39). Twelve PUG-S-0, 6 PUG-S-11, 23 PUG-2.7, and 17 PUG-39 were evaluated between 2 hours and 3 months post-implantation. Almost all PUS-S-O occluded with thrombus soon after implantation. PUG-2.7 had poor patency. Both PUG-S-11 and PUG-39 showed acceptable patency. Endothelialization, however, was limited to l-2 mm from proximal and distal anastomoses in any patent PUG-S-11. In contrast, all but one of the patent PU-G-39 were completely endothelialized. The extent of mural thrombosis decreased in the order from PUG-39 to PUG-S-11, PUG-2.7. and PUG-S-0. In conclusion, micropores penetrating through the graft wall, as reflected by hydraulic permeability values, appear to inhibit critical mural thrombosis and to promote a high degree of endothelialization.