Incidence and natural history of coronary evagination after implanted biodegradable polymer sirolimus-eluting stent.

Aims: The incidence and temporal change in coronary evagination (CE) after first-generation drug-eluting stent implantation is well established, whereas that after biodegradable polymer sirolimus-eluting stent (BP-SES) implantation has not yet been evaluated. The aim of this study is to assess the incidence and natural history of CE after BP-SES implantation. Methods and results: In this multicenter registry, stable coronary lesions treated by Ultimaster BP-SES were evaluated by serial optical frequency domain imaging (OFDI) (at 0-1-12 or 0-3-12 months) and the incidence of CE was assessed. Coronary evagination was defined as the presence of an outward bulge in luminal vessel contour between apposed struts according to the following criteria: (i) evagination depth ≥10% of nominal stent diameter and (ii) evagination length ≥3.0 mm. Optical frequency domain imaging was obtained in 98, 47, 49, and 87 lesions at 0, 1, 3, and 12 months, respectively. Coronary evagination was observed in 20 (42.6%) and 12 (24.5%) lesions at 1 and 3 months, respectively, and all but one CE had resolved at 12 months. At 12 months, the mean CE area was almost zero and the mean malapposed stent area was also decreased. Comparison of the serial OFDI images indicated that CEs originated mostly from acute stent malapposition or coronary dissection behind the implanted stent. Conclusions: In stable lesions, CE was occasionally observed with Ultimaster BP-SES at 1-3 months but mostly resolved within 12 months, without late-acquired stent malapposition. These findings suggest the safety and feasibility of biodegradable polymer coating on DES.