Seeding of ePTFE carotid interposition grafts in sheep and dogs: species-dependent results.

Abstract

Autologous endothelial seeding of thin-walled ePTFE vascular prostheses (I.D.4 mm), interposed in the carotid artery, was performed in 10 dogs and 14 sheeps. Aspirin (250 mg/day) and dipyridamole (75 mg/twice daily) were given throughout the study as antiplatelet therapy. Animals were killed 2 and 5 weeks after surgery. Patency rates for seeded grafts in dogs were 75% (6:8) and 83% (10:12) at 2 and 5 weeks, respectively. In control grafts the patency rates were identical. Patency rates for seeded grafts in sheep were 0% (0:5) and 11% (1:9) at 2 and 5 weeks, respectively. Control grafts in sheep had a patency rate of 40% (2:5) and 0% (0:9) at corresponding times. Scanning electron microscopy showed an almost complete endothelialization of seeded grafts in dogs after 5 weeks. Platelet deposition was studied in the dogs by means of chromium-51-labeled autologous platelets. Significantly fewer platelets accumulated on seeded grafts, and the ratio of 6-keto-PCF1 alpha to thromboxane B2 was significantly higher, compared with unseeded grafts, which indicated the presence of a functionally active endothelial lining in seeded grafts. Differences in the hemostatic system could account for the high clotting incidence in sheep, compared with that in dogs. Such species differences make extrapolations to the clinical situation from autologous endothelial seeding in experimental animals hazardous.