External beam irradiation for inhibition of intimal hyperplasia bypass: Preliminary following prosthetic results

To determine whether external beam irradiation delivered immediately after graft implantation can inhibit anastomotic intimal hyperplasia (IH) 1 month following polytetrafluoroethylene (PTFE) bypass in a sheep carotid artery model, 23 sheep underwent bilateral bypass of the ligated common carotid ar tery with 8-mm PTFE immediately followed by a single dose of irradiation (1 5, 21, or 30 Gy) to one side. The 15 animals with bilaterally patent grafts were euthanized at 1 month and graft-arterial anastomoses harvested. Using computer-aided image analysis, IH areas and thicknesses were measured. Gra ft patency in this model was 83% at 1 month and did not differ according to treatment administered. In the control animals, IH was greatest at mid-ana stomosis, but minimal within the native vessel. All three radiation doses m arkedly inhibited mid-anastomotic IH area and thickness. At the proximal an astomosis, 30 Gy reduced the IH area 20-fold, from 2.06 to 0.14 mm(2) (p < 0.0001 by ANOVA), and IH thickness 70-fold, from 29.0 to 0.4 <mu>m (p < 0.0 002); similar effects were seen at the distal anastomosis. No adverse effec ts of radiation treatment were observed. External beam irradiation in doses of 15 to 30 Gy delivered in a single fraction immediately after operation markedly inhibits development of intimal hyperplasia 1 month following end- to-side anastomosis with PTFE in sheep.