Background-Frequency-domain optical coherence tomography (FD-OCT) is a novel, high resolution intravascular imaging modality. Intravascular ultrasound (IVUS) is a widely used conventional imaging modality for achieving optimal stent deployment. The aim of this study was to evaluate the impact of FD-OCT guidance for coronary stent implantation compared with IVUS guidance. Methods and Results-A total of 70 patients with de novo coronary artery lesions and either unstable or stable angina pectoris were enrolled in this randomized study (optical coherence tomography [OCT] group: nϭ35, IVUS group: nϭ35). In the OCT group, stent implantation was performed under FD-OCT guidance alone and final stent expansion was evaluated by IVUS. In the IVUS group, conventional IVUS guidance was used and final stent apposition was evaluated by FD-OCT. There were no significant differences regarding the procedural, fluoroscopy time, and contrast volume. Although device and clinical success rates also were similar, the visibility of vessel border was significantly lower in the OCT group (PϽ0.05). Minimum and mean stent area and focal and diffuse stent expansion were smaller (6.1Ϯ2.2 mm versus 7.1Ϯ2.1 mm, 7.5Ϯ2.5 versus 8.7Ϯ2.4 mm, 64.7Ϯ13.7% versus 80.3Ϯ13.4%, 84.2Ϯ15.8% versus 98.8Ϯ16.5%, PϽ0.05, respectively), and the frequency of significant residual reference segment stenosis at the proximal edge was higher in the OCT group (PϽ0.05). Incomplete apposed struts in both groups were similar (Pϭ0.34). Conclusions-FD-OCT

Background— 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. Methods and Results— 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 <0.0001), with heterogeneous intima being more frequently observed at the minimum lumen area site in the VL-ISR group (90.7% versus 17.9%, P <0.0001). Disrupted intima with cavity and intraluminal material also were observed more frequently in the VL-ISR group for the entire stent (18.6% versus 0%, 20.9% versus 2.6%, P <0.03) as well as at the minimum lumen area site (13.9% versus 0%,16.2% versus 0%, P <0.03). Conclusions— 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.

The OCT morphological characteristics of DES restenotic tissue varied at different time-points. OCT images in early DES ISR might be associated with delayed arterial healing, and neoatherosclerosis might contribute to late catch-up phenomenon (L-ISR and VL-ISR) after DES implantation.