Serial long-term evaluation of neointimal stent coverage and thrombus after sirolimus-eluting stent implantation by use of coronary angioscopy

Objective: Progression of neointimal stent coverage ( NSC) and changes in thrombus were evaluated serially by coronary angioscopy for up to 2 years after sirolimus- eluting stent ( SES) implantation. Design: Serial angioscopic observations were performed in 20 segments of 20 patients at baseline, and at 6 months and 2 years after SES implantation. NSC was classified as follows: 0, uncovered struts; 1, visible struts through thin neointima; or 2, no visible struts. In each patient, maximum and minimum NSC was evaluated. Existence of thrombus was also examined. Results: The maximum NSC increased from 6 months to 2 years ( 1.2 ( 0.4) vs 1.8 ( 0.4), respectively, p = 0.005), while the minimum NSC did not change ( 0.7 ( 0.5) vs 0.8 ( 0.4), respectively, p = 0.25). The prevalence of patients with uncovered struts did not decrease from 6 months to 2 years ( 35% vs 20%, respectively, p = 0.29). Although there were no thrombus- related adverse events, new thrombus formation was found in one patient ( 5%) at the 6- month, and in four patients ( 20%) at the 2- year follow- up evaluations. Frequencies of thrombus inside the SES at baseline, 6 months and 2 years did not differ one from another ( 40%, 40% and 30%, respectively; p = NS). Conclusions: Neointimal growth inside the SES progressed heterogeneously. Uncovered struts persisted in 20% of the patients for up to 2 years and subclinical thrombus formation was not a rare phenomenon.