Quantitative and qualitative changes in DES-related neointimal tissue based on serial OCT

Objectives: The study evaluated serial quantitative and qualitative changes in vascular responses to drug-eluting stents (DES) using optical coherence tomography (OCT). Background: Serial changes in stent strut coverage and neointima characteristics in DES-treated lesions have not been sufficiently investigated using OCT. Methods: Serial OCT was performed in 72 patients with 76 DES-treated lesions at 9 months and 2 years after DES implantation (sirolimus-eluting stent, n = 23; paclitaxel-eluting stent, n = 20; zotarolimus-eluting stent, n = 25; everolimus-eluting stent, n = 8). Serial changes in quantitative parameters (neointimal thickness, stent strut coverage, and apposition at each strut) and qualitative characteristics of the neointima were evaluated. Results: Mean neointimal thickness significantly increased from 164 μm to 214 μm between 9 months and 2 years (p < 0.001), and the percentage of uncovered stent struts significantly decreased (from 4.4% to 2.3%, p < 0.001). Completely covered lesions were more frequently observed at 2 years (44.7% vs. 59.2%, p = 0.07). However, the percentage of malapposed struts (0.6% vs. 0.9%, p = 0.24) and incidence of intracoronary thrombi (10.5% vs. 9.2%, p > 0.99) were similar. On qualitative evaluation of neointimal morphology, lipid-laden neointima (27.6% vs. 14.5%, p = 0.009) and thin-cap neoatheroma (13.2% vs. 3.9%, p = 0.07) were more frequently detected at 2-year follow-up compared with 9 months. In matched cross-sectional evaluation, the change of neointimal morphology from homogeneous to heterogeneous or lipid-laden pattern was observed in 23 (30.3%) of 76 lesions. There was a significant increase in percent neointimal hyperplasia cross-sectional area in those lesions. Conclusions: This OCT study suggested that neointimal coverage improved from 9 months to 2 years without significant changes in the incidence of malapposed struts and intracoronary thrombus. Additionally, in-stent neoatherosclerosis including transformation to lipid-laden neointima might progress during extended follow-up periods after DES implantation.