Characterization of in-stent neointimal tissue components following drug-eluting stent implantation according to the phase of restenosis using a 40-MHz intravascular ultrasound imaging system

Background and purpose: It is known that drug-eluting stents (DESs) are associated with in-stent restenosis (ISR). However, the characteristics of neointimal tissue components according to the mechanism and time course of DES ISR have not been fully examined. The aim of this study was to characterize the in-stent neointimal tissue components according to the phase of restenosis using radiofrequency signals from 40-MHz intravascular ultrasound (IVUS), called iMAP-IVUS (Boston Scientific Corp., Fremont, CA, USA). Methods: IVUS examinations were performed in 37 angina patients (37 lesions) who underwent repeated percutaneous coronary intervention (PCI) for the treatment of DES ISR. The patients were divided into two groups according to the phase of restenosis: the early ISR group (E-IRS; <= 1 year) and the late ISR group (L-ISR; >1 year). Results: There were 18 patients in the E-ISR group and 19 patients in the L-ISR group. The mean follow-up period between stent implantation and repeated PCI was 8.0 +/- 2.2 months in the E-IRS group and 40.4 +/- 23.9 months in the L-ISR group. The percentage of lipid components and relative necrotic volume were greater in the L-ISR group than in the E-ISR group (5.77 +/- 1.81% vs. 4.51 +/- 1.71%, p < 0.05 and 12.20 +/- 2.97% vs. 8.61 +/- 2.33%, p < 0.001, respectively). Furthermore, there was a positive correlation between the follow-up duration after DES implantation in the L-ISR group and the presence of a necrotic plaque component (r = 0.49, p < 0.05). Conclusions: There were differences in the neointimal plaque characteristics after DES implantation according to the phase of restenosis. This information may lead to a better understanding of the mechanisms of DES ISR. (C) 2014 Japanese College of Cardiology. Published by Elsevier Ltd. All rights reserved.