New graft materials and current approaches to an acceptable small diameter vascular graft.

Prosthetic graft material has not been successful for small artery bypass. Mechanical, cellular, and humoral factors have all been implicated as a cause of failure. In vitro, ex vivo, and in vivo methods have been developed to assess platelet and fibrinogen deposition, measure compliance, and study other factors theorized to relate to graft failure. Cell culture techniques have been used to determine the role of cellular mitogens. The goal of an arterial substitute that can maintain patency in a 3-4 mm diameter low-flow configuration and that is not associated with the development of anastomotic hyperplasia has yet to be reached. A variety of solutions are being researched. New nonthrombogenic polymers are being tested as are new coatings for standard materials. Endothelial cell seeding has been accomplished in animals and is being tried in human clinical studies. Problems and results of endothelial seeding trials are reviewed. Other biologic approaches include the in vitro construction of a blood vessel model using cell coculture techniques and the implantation of bioabsorbable prosthetics into animals. The role of pharmacologic agents in maintaining graft patency is addressed.