Difference of Tissue Characteristics Between Early and Very Late Restenosis Lesions After Bare-Metal Stent Implantation

Abstract

Although in-stent restenosis (ISR) after bare-metal stent (BMS) implantation peaks in the early phase, very late (VL) ISR occasionally is observed beyond a few years after BMS implantation. To date, this mechanism has not been fully clarified. We compared the morphological characteristics of VL-ISR (>5 years, without restenosis within the first year) (n=43) to those of early (E) ISR (within the first year) (n=39) using optical coherence tomography (OCT). Qualitative restenotic tissue analysis included assessment of tissue structure (homogeneous or heterogeneous), presence of microvessels, disrupted intima with cavity, and intraluminal material and was performed at every 1-mm slice of the entire stent. The proportions of cross-sections with heterogeneous intima in the entire stent was significantly higher in the VL-ISR group compared to the E-ISR group (60.5±28.5% versus 5.8±11.5%, P P P P <0.03). The morphological characteristics of restenotic tissue in VL-ISR were different from those in E-ISR and similar to atherosclerotic plaque. In BMS, progression of the atherosclerotic process within neointima after stent implantation may be associated with VL-ISR.