VASOREACTIVITY AND RESTENOSIS AFTER CORONARY ANGIOPLASTY IN THE ATHEROSCLEROTIC PIG MODEL

Background: The effect of coronary angioplasty on coronary spasm remai ns unknown. We examined the effects of balloon angioplasty, using an o versized balloon, on coronary hypercontraction and eventual restenosis in a pig model of coronary spasm. Methods: We performed balloon angio plasty, using an oversized balloon at the site of coronary spasm super imposed on atherosclerosis with 6 (group A, n=14) or 1 (group B, n=14) atmospheres of inflation pressure in miniature pigs. Using coronary a ngiography we assessed the coronary basal diameter and diameter change in response to histamine and serotonin before, immediately after, and 4 weeks after angioplasty. Histological examinations were performed i mmediately after and 4 weeks after the angioplasty. Results: Before an gioplasty, histamine- and serotonin-induced hypercontraction was repro ducibly noted at the atherosclerotic site. Immediately after angioplas ty, the coronary diameter became larger (P<0.01) than before angioplas ty in group A, but there was no significant difference in group B. The hypercontraction in group A was abolished immediately after and 4 wee ks after angioplasty, whereas the hypercontraction in group B was unch anged. Histological examination revealed medial necrosis immediately a fter and medial fibrosis 4 weeks after angioplasty, which were more pr ominent in group A. Four weeks after angioplasty, the magnitude of res tenosis was greater in group A than in group B. Conclusions: Angioplas ty using an oversized balloon with the higher atmosphere of inflation pressure abolished coronary hypercontraction immediately after and 4 w eeks after angioplasty, which probably resulted from the irreversible damage to medial smooth muscles; however, this did not prevent resteno sis.