A small-caliber vascular graft for aortocoronary artery graft with temporarily artificial and permanently natural antithrombogenicity and natural vessel compliance

Summary

A small-caliber vascular graft was developed and evaluated as a carotid artery replacement and aortocoronary artery graft in animal experiments. Canine carotid arteries were obtained, soaked in distilled water, and then sonicated bring about cell destruction. In this way, a natural tissue tube composed of collagen and elastic laminae was obtained. The tube with a protamine sulfate solution inside was cross-linked with polyepoxy compounds, which made the graft white, hydrophilic, soft, and pliable. The graft was dipped into a heparin solution, which allowed heparin to bind ionically. Eighty grafts (3 mm inner diameter, 6 cm in length) were implanted in the carotid arteries of 40 dogs and resected 1–389 days after implantation. Three grafts were occluded by graft infection and 77 were patent (96% patency). Sixteen control grafts, in which the tissue tube was cross-linked with glutaraldehyde but was not heparinized, were implanted in eight dogs. All of them were occluded within 1 week. Aortocoronary bypass grafting was also performed using the heparinized graft in eight dogs for periods up to 4 months. All the grafts were confirmed to be patent by autopsy or graft angiography. Measurement of the heparin content revealed that about 90% of it was released within 1 month. After the release of heparin, the surface of the graft was completely covered with endothelial cells. The graft wall kept its soft and pliable properties even after the long-term implantation. These results indicate that the antithrombogenicity produced by the combination of the slow release of heparin and endothelialization, together with the natural vessel compliance in the graft, were the major reasons for its success as a small-caliber graft.