BACKGROUND: Although very late stent thrombosis occurs several years after implantation of sirolimus-eluting stent (SES), the morphologic changes of the stent beyond 2 years have not yet been systematically studied in living patients. The late vascular response to SES was therefore evaluated by serial angioscopic studies at 2 and 5 years after stent implantation. METHODS: A total of 17 patients with 17 SES underwent a repeated angioscopy procedure at 2 and 5 years. Neointimal stent coverage (NSC) was classified as follows: grade 0, presence of uncovered struts; grade 1, visible struts through a thin neointima; or grade 2, complete neointimal coverage without visible struts. For each patient, the minimum and maximum NSC grade and the existence of in-stent thrombus were recorded. RESULTS: The minimum and maximum NSC grade did not increase between the 2 and 5 years (0.59 ± 0.51 vs 0.88 ± 0.70, P = .17, and 1.82 ± 0.39 vs 1.94 ± 0.24, P = .30, respectively). The prevalence of patients with uncovered struts did not significantly decrease from 2 to 5 years (41% vs 29%, P = .49). During the follow-up period, 3 of 6 thrombi disappeared, whereas new thrombus formation was found in 3 patients without any clinical symptoms. In-stent thrombus did not decrease (35% vs 35%, P > .99). CONCLUSIONS: The current serial angioscopic study suggests that incomplete NSC and the prevalence of latent thrombus within the SES segments did not decrease from 2 to 5 years. The risk of stent thrombosis related to incomplete healing of SES may continue for an extended period.
BACKGROUND: Although very late stent thrombosis occurs several years after implantation of sirolimus-eluting stent (SES), the morphologic changes of the stent beyond 2 years have not yet been systematically studied in living patients. The late vascular response to SES was therefore evaluated by serial angioscopic studies at 2 and 5 years after stent implantation. METHODS: A total of 17 patients with 17 SES underwent a repeated angioscopy procedure at 2 and 5 years. Neointimal stent coverage (NSC) was classified as follows: grade 0, presence of uncovered struts; grade 1, visible struts through a thin neointima; or grade 2, complete neointimal coverage without visible struts. For each patient, the minimum and maximum NSC grade and the existence of in-stent thrombus were recorded. RESULTS: The minimum and maximum NSC grade did not increase between the 2 and 5 years (0.59 ± 0.51 vs 0.88 ± 0.70, P = .17, and 1.82 ± 0.39 vs 1.94 ± 0.24, P = .30, respectively). The prevalence of patients with uncovered struts did not significantly decrease from 2 to 5 years (41% vs 29%, P = .49). During the follow-up period, 3 of 6 thrombi disappeared, whereas new thrombus formation was found in 3 patients without any clinical symptoms. In-stent thrombus did not decrease (35% vs 35%, P > .99). CONCLUSIONS: The current serial angioscopic study suggests that incomplete NSC and the prevalence of latent thrombus within the SES segments did not decrease from 2 to 5 years. The risk of stent thrombosis related to incomplete healing of SES may continue for an extended period.