Effect of External Beam Irradiation on Intimal Hyperplasia in Autografted Femoral Artery of Dog

Lee, Song Ok; Sohn, Chang Yong; Park, Kwan Gyu; Kim, Ok Bae; Cho, Won Hyun

Abstract

BACKGROUNDS: It is well known that intimal hyperplasia is one of the most important cause of vascular graft failure in angioplasty, autogenous venous graft and prosthetic bypass graft. Clinical trials of drugs including antiplatelet agents, anticoagulant, corticosteroid, cyclosporine and prostaglandin were not satisfactory in suppressing intimal hyperplasia. Seeding of endothelial cell also have been done for this purpose with some success. There are several reports that endovascular low dose irradiation and external beam irradiation might reduce the amount of proliferative neointima after arterial injury.
METHODS
In order to evaluate the effect of external beam irradiation on intimal hyperplasia in grafted vessel, femoral artery autografts using external jugular vein were performed in dogs, and studied the morphological finding under microscope and compared intimal hyperplasia between control and radiated groups. Group I (control) was not irradiated after graft. But experimental groups were irradiated with 6 Mev electron: Group II, 800 cGy on day 1; Group III, 400 cGy on day 1 and day 4 each; and Group IV, 800 cGy on day 4. Radiation efficacy on intimal hyperplasia was histologically assessed by measuring neointimal thickness at the proximal and distal site of grafted vessel at 6 weeks after graft.
RESULTS
Mean neointimal thickness in all irradiated groups were significantly lesser than control group (p<0.05) and not related with irradiating time: Group I (Control), 0.41+/-0.11 mm; Group II, 0.16+/-0.10 mm; Group III, 0.19 0.10 mm; Group IV 0.15+/-0.08 mm. There was no difference in intimal hyperplasia between proximal and distal anastomotic site of grafted vessels in both control and irradiated groups: Control, 0.42+/-0.11 mm vs 0.40+/-0.10 mm; Radiated groups, 0.17+/-0.10 mm vs 0.16+/-0.09 mm; (p>0.05).
CONCLUSION
These data suggest that low dose external beam irradiation might suppress intimal hyperplasia in grafted vessel, but further study will be necessary to determine optimal dose and timing of radiation delivery, and its efficacy in long segment bypass graft.