BACKGROUND: The mechanism and time course of in-stent restenosis (ISR) after implantation of second-generation DES have not yet been fully elucidated. We sought to evaluate the differences in tissue characteristics between the different phases of ISR after second-generation DES implantation using optical coherence tomography (OCT).Methods and Results: From June 2010 to December 2015, 324 consecutive patients with 337 ISR lesions underwent OCT. Of these, we analyzed 53 lesions in 53 patients who had their first ISR after second-generation DES implantation and underwent OCT before any procedures. According to the timing of ISR, the patients were divided into the early group (within 1 year: E-ISR, n=30) and late group (beyond 1 year: L-ISR, n=23). Quantitative parameters and qualitative characteristics of the neointima were evaluated. In the minimum lumen area site analysis, the E-ISR group had more frequently homogeneous intima than the L-ISR group (26.7% vs. 4.4%, P=0.02). The frequencies of neointima with lipid-laden, thin-cap fibroatheroma, neovascularization and macrophage infiltration were significantly higher in the L-ISR group than in the E-ISR group (30.0% vs. 69.6%, P<0.01; 0.0% vs. 26.1%, p <0.01; 6.7% vs. 26.1%, P=0.049; 3.3% vs. 26.1%, P=0.01, respectively). CONCLUSIONS: Neointimal tissue characteristics differed between E-ISR and L-ISR after second-generation DES implantation. E-ISR was mainly caused by neointimal hyperplasia, whereas neoatherosclerosis was the main mechanism of L-ISR.
BACKGROUND: The mechanism and time course of in-stent restenosis (ISR) after implantation of second-generation DES have not yet been fully elucidated. We sought to evaluate the differences in tissue characteristics between the different phases of ISR after second-generation DES implantation using optical coherence tomography (OCT).Methods and Results: From June 2010 to December 2015, 324 consecutive patients with 337 ISR lesions underwent OCT. Of these, we analyzed 53 lesions in 53 patients who had their first ISR after second-generation DES implantation and underwent OCT before any procedures. According to the timing of ISR, the patients were divided into the early group (within 1 year: E-ISR, n=30) and late group (beyond 1 year: L-ISR, n=23). Quantitative parameters and qualitative characteristics of the neointima were evaluated. In the minimum lumen area site analysis, the E-ISR group had more frequently homogeneous intima than the L-ISR group (26.7% vs. 4.4%, P=0.02). The frequencies of neointima with lipid-laden, thin-cap fibroatheroma, neovascularization and macrophage infiltration were significantly higher in the L-ISR group than in the E-ISR group (30.0% vs. 69.6%, P<0.01; 0.0% vs. 26.1%, p <0.01; 6.7% vs. 26.1%, P=0.049; 3.3% vs. 26.1%, P=0.01, respectively). CONCLUSIONS: Neointimal tissue characteristics differed between E-ISR and L-ISR after second-generation DES implantation. E-ISR was mainly caused by neointimal hyperplasia, whereas neoatherosclerosis was the main mechanism of L-ISR.