A New Polyurethane/Heparin Vascular Graft for Small-Caliber Vein Repair

Small-caliber (1.2 mm inner diameter) vein grafts, made from a mixture of heparin and polyurethane with superior compliance, excellent antithrombogenicity and biocompatibility, have been developed. Eighteen rabbits were used; 12 for the heparin containing grafts and the other six were pure polyurethane grafts as controls. Each graft segment (2 cm in length) was implanted into the femoral veins using a newly developed anastomosis method. Sodium heparin was given before surgery, but no anticoagulant was used thereafter. All the rabbits lived during the whole experimental period of 1 year. Histological analyses of vessels retrieved 2, 4, 8, 12 and 24 weeks after implantation revealed regeneration of endothelial-like cells (in 2 weeks), elastin-like tissues (in 8 weeks), and neoadventitia-like layers (in 12 weeks). The patency rate for the heparin containing grafts was 100%, but was only 83.3% in the no heparin controls. These results indicate that “ideal” small diameter blood vessels can be synthesized and used directly without cellularization before implantation. By the properly selecting scaffold materials, a native vein can repair itself spontaneously to certain degree.