Healing process of small-diameter polyurethane vascular grafts with spongy structure

Two types of spongy polyurethane-polydimethylsiloxane (Cardiothane 51TM, Konron Instruments, Inc., U.S.A.) vascular grafts (PUG) with an internal diameter of 1.5 mm were fabricated by a spray, phase-inversion-technique: PUG with hydraulic permeability (HP) of 2.7 ml/min/cm2 (PUG-2.7) and PUG with HP of 39 ml/min/cm2 (PUG-39). Twenty-three straight PUG-2.7, 17 straight PUG-39 (1,5 - 2.0 cm in length) and one loop PUG-39 (10 cm in length) were implanted by the same surgeon end-to-end in the infrarenal aorta of 41 male Sprague-Dawley rats. Patency of PUG-2.7 was 73%a (8/11) at 2 weeks, but, at 3 months, decreased to 8% (1/2). At 3 months post-implantation patency of the straight PUG-39 was76% (13/17) and-the loop PUG-39 was also patent. The sole patent PUG-2.7 showed neointimal hyperplasia and incomplete endothelialization. All but one of the patent straight PUG-39 showed a glistening and transparent neointima with complete endothelialization and no anastomotic hyperplasia. The loop PUG-39 displayed endothelialization from each anastomosis and in many islands in the middle portion of the graft. Thus, PUG with a higher HP showed better patency and healing in the rat aortic replacement model.