Pathological effects of angioplasty on vasospastic carotid arteries in a rabbit model

To define the pathological effects of angioplasty on vasospastic arteries, 36 rabbits underwent angiography and induction of vasospasm by placement of blood-filled (vasospasm groups) or empty (control group) silastic sheaths around the cervical carotid arteries. Two (Day 2) or 7 days (Day 7) later, angiography was repeated and one carotid artery in each animal was dilated by balloon angioplasty. The rabbits were sacrificed 1 day, 7 days, or 3 to 4 weeks after angioplasty. Significant vasospasm developed after placement of silastic sheaths with blood (mean reductions in diameter 39% +/- 6% at Day 2 and 48% +/- 5% at Day 7). Arterial narrowing was less apparent in the control groups at Day 2 (24% +/- 7%). Angioplasty performed on Day 2 significantly increased arterial diameters of vasospastic arteries (50% +/- 7%; p < 0.05) but not those of control arteries (10% +/- 6%, p > 0.05). Angioplasty performed on Day 7 increased the arterial diameters by a similar degree (47% +/- 13%, not significant). Arteries remained dilated after angioplasty, although there was significant vasospasm 7 days after angioplasty when angioplasty was performed on Day 2. Blinded, semiquantitative histopathological study of the arteries showed that 3 to 4 weeks after angioplasty, there was significant endothelial proliferation and a trend for thinning of the tunica media. There were no significant changes in control arteries subjected to angioplasty. Angioplasty was not associated with significant arterial fibrosis as measured by hydroxyproline content (analysis of variance). The increase in endothelial proliferation and decrease in the thickness of the tunica media suggest that, in the rabbit model, angioplasty damages endothelial and smooth-muscle cells. This may be the basis for the observation that vasospastic arteries do not reconstrict after angioplasty.