Intimal changes in arteriovenous bypass grafts. Effects of varying the angle of implantation at the proximal anastomosis and of producing stenosis in the distal runoff artery.

Autologous arteriovenous bypass grafts were constructed between external iliac arteries in 20 mongrel dogs to determine the development of intimal fibromuscular hyperplasia. Animals received grafts at 55, 90 or 120 degree angles relative to the proximal anastomosis. Five animals with 90 degree angle grafts were also subjected to 80% stenosis in the runoff artery. All grafts showed the development of a fibromuscular tunica intima. Qualitative or quantitative intimal differences were not observed among grafts placed at 90 degree angles, 90 degree angles with runoff artery stenosis, or 120 degree angles. Grafts placed at 55 degree angles relative to the proximal anastomosis developed a consistently thicker fibromuscular layer in the tunica intima when compared to the other groups. These changes which were segmental in nature, occurred in the proximal and distal grafts and over the distal anastomosis.