Development of a thermal cross-linking heparinization method and its application to small caliber vascular prostheses

The authors developed a heparinization method for biomaterials without using chemical reagents and applied it to small caliber vascular prostheses. The vascular prostheses (4 mm diameter expanded polytetrafluoroethylene [e-PTFE], fibril length 90 microns) heparinized by thermal cross-linking, and control grafts (4 mm diameter e-PTFE, fibril length 30 microns), were implanted in the carotid arteries of eight adult dogs. Four pairs of grafts were explanted 1 hr after implantation, and the remaining four pairs were explanted 7 days after implantation. Patency was assessed macroscopically, and the grafts were examined microscopically. The anti thrombogenicity of the vascular prostheses heparinized by thermal cross-linking was good in comparison with that of the control group. However, on the outer surface of the grafts, the author found more infiltration of fibroblasts into the wall of the control grafts than in the heparinized grafts. The author surmised that heparinized gelatin injected into the interfibril space of the graft inhibited cellular infiltration. The infiltration of inflammatory cells was slight in both grafts. Thus, the author was successful in heparinizing the vascular prostheses by thermal cross-linking and obtaining slow release of heparin to maintain early antithrombogenicity. The high concentration of heparin in the graft wall, however, was thought to be an obstacle to integration of the vascular prostheses.