Long-term patency of regenerated neoaortic wall following the implant of a fully biodegradable polyurethane prosthesis: experimental lipid diet model in pigs.

The degradation of a polyurethane vascular prosthesis, the time course and characteristics of tissue ingrowth and prosthesis replacement, and the incidence of thrombosis have been investigated in 50 young pigs. A 6-7 cm long cone-shaped prosthesis was implanted in the infrarenal aorta of 50 young growing pigs which were sacrificed at intervals from 60 to 365 days. Ten animals were controls, 25 were given aspirin 10 mg/kg of body weight/day, and 15 were fed with cod liver oil. Aortography, done at 30, 60, and 90 days, showed 100% of implants were thrombosed in the surviving controls, 55% of the aspirin group had patent grafts, and 100% of animals in the lipid diet group had patent grafts. At final graft retrieval, the aspirin group showed only three patencies, while in the lipid diet group seven out of nine animals were patent. The laboratory and morphological studies indicated that all patent prostheses were lined with tissue that resembled the intima of native aorta with a layer of smooth muscle cells which appeared complete at 180 days. From these data we conclude that the biodegradable polyurethane vascular prosthesis is reliable for experimental implants in a pig model. The lipid-rich diet of polyunsaturated fatty acids potentiates long-term patency, perhaps by preventing platelet aggregation and thrombosis, and allowing the growth of a neoendothelium and neomedia within the lumen of the prosthesis, which slowly degrade towards fatty tissue and form neoadventitia.