Journal of Invasive Cardiology

Abstract: Objective. We sought to evaluate the characteristics of in-stent restenosis (ISR) lesions with microvessels, detected by an optical coherence tomography (OCT). Background. No sufficient in vivo data exist regarding microvessel characteristics in ISR lesions. Methods. Among 78 ISR lesions (drug-eluting stent, n = 72; bare-metal stent, n = 6) in our OCT registry database, visible microvessels were detected in 21 (27%). Microvessels were defined as low backscattering structures <200 μm in diameter on OCT. Clinical, angiographic, and OCT findings were compared between lesions with and without microvessels. Results. Lesions with microvessels had a larger reference vessel diameter (2.90 ± 0.47 mm vs 2.58 ± 0.42 mm; P=.009) and post-stent minimum lumen diameter (2.76 ± 0.29 mm vs 2.54 ± 0.39 mm; P=.033) than those without microvessels. From OCT findings at the segment with minimal lumen cross-sectional area (CSA), neointimal hyperplasia (NIH) CSA (5.4 ± 1.7 mm²  vs 4.2 ± 2.1 mm2; P=.024) and percent NIH CSA (NIH CSA × 100/stent CSA) were significantly greater in lesions with microvessels (79 ± 12% vs 67 ± 16%; P=.001). On multivariate analysis, reference vessel diameter (odds ratio [OR], 4.64; 95% confidence interval [CI], 1.05-20.4; P=.043) and percent NIH CSA at the segment with minimal lumen CSA (OR, 1.06; 95% CI, 1.01-1.12; P=.021) were independent predictors of microvessels. From receiver operating characteristic analysis, the cut-off values of reference vessel diameter and percent NIH CSA predicting the presence of microvessels were 3.1 mm and 74%, respectively. Conclusions. Visible microvessels in ISR lesions might be associated with increased vessel size and extent of NIH.

J INVASIVE CARDIOL 2012;24:116–120

Key words: optical coherence tomography, restenosis, stent

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Many attempts have been made to find the mechanisms or factors related to excessive neointimal hyperplasia (NIH), which causes in-stent restenosis (ISR) after stent implantation.^1-3 From an autopsy study, it was suggested that extensive neovascularization at sites of stent restenosis may play a key role in neointimal proliferation, progression, and further aggravation of neoatherosclerosis.⁴ However, minimal in vivo data exist regarding in-stent neovascularization or characteristics of the neointima. Optical coherence tomography (OCT), a newly developed intracoronary imaging modality, has provided high-resolution cross-sectional images of tissues and enabled identification of microstructures that could not be visualized by previous standard imaging tools such as intravascular ultrasound.^5-7 A previous OCT study reported in vivo identification of visible microvessels that were suggestive of neovascularization within NIH.⁷ Therefore, we hypothesized that ISR lesions with microvessels may have different neointimal characteristics than those without microvessels. Clinical, angiographic, and OCT findings of lesions with microvessels were compared to those of lesions without microvessels.