Background: The effect of coronary angioplasty on coronary spasm remains unknown. We examined the effects of balloon angioplasty, using an oversized balloon, on coronary hypercontraction and eventual restenosis in a pig model of coronary spasm.
Methods: We performed balloon angioplasty, using an oversized balloon at the site of coronary spasm superimposed on atherosclerosis with 6 (group A, n = 14) or 1 (group B, n = 14) atmospheres of inflation pressure in miniature pigs. Using coronary angiography 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 immediately after and 4 weeks after the angioplasty.
Results: Before angioplasty, histamine- and serotonin-induced hypercontraction was reproducibly noted at the atherosclerotic site. Immediately after angioplasty, the coronary diameter became larger (P < 0.01) than before angioplasty in group A, but there was no significant difference in group B. The hypercontraction in group A was abolished immediately after and 4 weeks after angioplasty, whereas the hypercontraction in group B was unchanged. Histological examination revealed medial necrosis immediately after and medial fibrosis 4 weeks after angioplasty, which were more prominent in group A. Four weeks after angioplasty, the magnitude of restenosis was greater in group A than in group B.
Conclusions: Angioplasty using an oversized balloon with the higher atmosphere of inflation pressure abolished coronary hypercontraction immediately after and 4 weeks after angioplasty, which probably resulted from the irreversible damage to medial smooth muscles; however, this did not prevent restenosis.