Neointimal Coverage Over Coronary Stent Struts Crossing the Side Branch Ostia

Abstract

Circulation Journal Official Journal of the Japanese Circulation Society http://www. j-circ.or.jp ecently, the incidence of restenosis after percutaneous coronary intervention has been greatly reduced by the widespread use of drug-eluting stents (DES). 1 At the same time, however, safety concerns have been raised regarding the occurrence of late stent thrombosis (LST) after DES implantation. 2,3 Although the mechanism of LST has not yet been fully explained, pathological data from a registry totaling 81 human autopsies of DES recipients revealed that the most powerful histological predictor of stent thrombosis was the degree of endothelial coverage, and that the best morphometric predictor of LST was the ratio of uncovered to total stent struts. 4 Further, although the cases were collected before the DES era, a pathological analysis examining 13 cases with histological evidence of an acute occlusive or nonocclusive mural thrombus within a coronary stent in place ≥30days showed that stenting across ostia of major arterial branches (5 cases) and exposure to radiation therapy (3 cases) were the most frequent pathological mechanisms of LST. 5 Article p 106Previous and recent angioscopic studies have shown that neointimal coverage (NIC) over bare metal stents (BMS) is usually completed within 6 months, 6,7 but that NIC over DES is generally delayed. 8,9 Recent reports using optical coherence tomography (OCT) assessment revealed that the incidence of complete NIC was less than 30% at 9-12 months after DES implantation. 10,11 Accordingly, the lack or delay of NIC could be a possible explanation for the increased incidence of LST after DES implantation. DES at the site of side branches may be an especially high-risk combination for LST. In other words, stent struts placed across the ostia of the sidebranch vessels could be typical candidates for LST, because of delayed NIC. However, few published data regarding NIC in such regions have been available until very recently.Since 2011, several reports have demonstrated that variability among coronary stents in the strut coverage pattern assessed with OCT exists in the bifurcation. 12-14 Kyono et al 12 investigated 12,656 struts in 61 bifurcation segments (paclitaxel-eluting stent (PES): 16; sirolimus-eluting stent (SES): 14; zotarolimus-eluting stent (ZES): 23; BMS: 8) from 46 patients at 6 months after stent deployment. They found that PES had the highest prevalence of uncovered segments in the side-branch ostial region (PES 60.1, SES 17.0, ZES 13.2, BMS 12.3 (%), P<0.0001), whereas SES demonstrated the highest prevalence of uncovered segments opposite the ostial region (PES 3.3, SES 14.0, ZES 1.5, BMS 0.0 (%), P=0.0025). Her et al 13 evaluated the degree of NIC crossing the sidebranch vessel with OCT at 9.3 months after DES implantation. They found significant differences in the proportion of covered stents among the 3 DES types in 51 patients (6 (27%) of 22 with SES, 1 (7%) of 15 with PES, 8 (57%) of 14 with ZES; P=0.011). The percentage of NIC in the overall stent strut...