Efficacy of corticosteroids in suppression of intimal hyperplasia.

The effect of steroids and immunosuppression on the development of intimal hyperplasia was studied in 24 New Zealand white rabbits. Staged bilateral arteriotomy and stripping of intima of the common carotid artery was performed by means of a 2F balloon catheter under 700 mm Hg of pressure. At 3 months, after the control side artery was harvested (N = 24), the rabbits were assigned to three groups of eight animals each: (1) dexamethasone 0.1 mg/kg, (2) cyclophosphamide (Cytoxan) 1 mg/kg, or (3) azathioprine 1 mg/kg intramuscularly. The animals were treated on the day before the contralateral intimal stripping and then were treated six times a week for 8 weeks; the vessels were harvested at 3 months. Twelve-week patency rates were 62.5% in the control group, 83.3% in the dexamethasone group, 100% in the Cytoxan group, and only 33.3% in the azathioprine group. The ratio of the luminal area to the area enclosed by the internal elastic lamina was used as an index of intimal hyperplasia, with a higher ratio indicating less intimal thickening. This ratio of the patient vessels was 0.74 +/- 0.14 (N = 15) for the controls, 0.79 +/- 0.11 (N = 6) for the Cytoxan group, and 0.91 +/- 0.06 (N = 5, p less than 0.05) for the dexamethasone group, which is statistically significant by means of analysis of variance. Occluded vessels had evidence of organized thrombus without any intimal hyperplasia. The decrease in intimal hyperplasia seen in the steroid group suggests a potential role for steroids in small vessel revascularization, but further studies are required.