Differences in tissue characterization of restenotic neointima between sirolimus-eluting stent and bare-metal stent: integrated backscatter intravascular ultrasound analysis for in-stent restenosis

Abstract

The pathogenesis of in-stent restenosis (ISR) after drug-eluting stent (DES) implantation remains unclear. The purpose of this study is to analyse tissue characterizations of neointima in restenosis lesions after sirolimus-eluting stent (SES), comparing with those after bare metal stent (BMS) using integrated backscatter intravascular ultrasound (IB-IVUS). A total of 54 consecutive patients who had ISR lesions after SES (n = 20) or BMS (n = 34) implantation were enrolled. For tissue characterization of neointima, IB-IVUS was performed by cross-sectional (at the minimum lumen area) and volumetric (within the stented segment) analyses. In addition, angiographic patterns of restenosis were evaluated with division into focal and diffuse. The focal angiographic pattern of restenosis was predominantly observed in the SES group (SES vs. BMS; 80.0 vs. 26.5%; P = 0.0001), whereas the diffuse pattern was more common in the BMS group (SES vs. BMS; 20.0 vs. 73.5%; P = 0.0001). On both cross-sectional and volumetric IB-IVUS analyses, the neointimal tissue in restenosis lesions after SES implantation had a significantly larger percentage of lipid tissue (cross-sectional: 23.3 ± 12.7 vs. 15.7 ± 11.9%; P = 0.033; volumetric: 22.8 ± 10.4 vs. 16.3 ± 7.0%; P = 0.008) and a significantly smaller percentage of fibrous tissue compared with that after BMS implantation (cross-sectional: 73.6 ± 11.6 vs. 82.0 ± 11.2%; P = 0.011, volumetric: 73.8 ± 9.5 vs. 80.5 ± 6.7%; P = 0.004). This IB-IVUS study indicates that larger amounts of lipid tissue are present in neointima of SES when compared with BMS, suggesting that neoatherosclerosis may in part be responsible for ISR after SES implantation.