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Background: It recently has been hypothesized that a larger late loss may have a protective role against stent thrombosis. The relationship between angiographic late loss and the presence of thrombus based on angioscopic findings within paclitaxel-eluting stents (PES) and sirolimus-eluting stents (SES) was investigated in this study., Methods and Results: Prospective 6-month follow-up angiographic and angioscopic examinations were performed on 18 patients for PES and on 20 patients for SES. Late loss was measured by quantitative coronary angiography. Angioscopic neointimal stent coverage (NSC) grade was classified as follows: 0=uncovered struts without neointima, 1=visible struts through thin neointima, and 2=no visible struts. In each patient, maximum NSC, minimum NSC, and the existence of thrombus were evaluated. Late loss and maximum NSC were greater in PES than in SES (0.38+/-0.43 versus 0.10+/-0.23 mm; P=0.02 and P=0.0004, respectively). Late loss was correlated with maximum NSC (grade 0, 0.06+/-0.01 mm; grade 1, 0.10+/-0.05 mm; and grade 2, 0.48+/-0.46 mm), whereas there was no correlation between late loss and minimum NSC. The prevalence of patients with uncovered struts did not differ (44% of PES, 40% of SES; P=0.78). In-stent thrombus was found more frequently in PES than in SES (72% versus 40%, P=0.046) despite no occurrence of stent thrombosis. Only within PES were thrombi found in the segments of NSC grade 2 associated with large late loss., Conclusions: The present study suggests that angiographic large late loss was not associated with a low risk of in-stent thrombus.

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.

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., Methods: Serial angioscopic observations were performed in 20 segments of 20 patients at baseline, at 6 months and at 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 (mean (SD) 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 5% of 6-month, and in 20% of 2-year follow-up evaluations. The prevalence of thrombus inside the SES at baseline, 6 months and 2 years was similar (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 uncommon.

Confirming complete neointimal coverage after implantation of a drug-eluting stent is clinically important because incomplete stent coverage is responsible for late thrombosis and sudden cardiac death. Optical coherence tomography is a high-resolution (approximately 10 microm) imaging technique capable of detecting a thin layer of neointimal hyperplasia (NIH) inside a sirolimus-eluting stent (SES) and stent malapposition. This investigation evaluated stent exposure and malapposition 3 months after SES implantation using optical coherence tomography in a different clinical presentations, such as acute coronary syndrome (ACS) and non-ACS. Motorized optical coherence tomographic pullback (1 mm/s) was performed at 3-month follow-up to examine consecutive implanted 31 SESs in 21 lesions in 21 patients (9 with ACS and 12 with non-ACS). NIH thickness inside each strut and percent NIH area in each cross section were measured. In total, 4,516 struts in 567-mm single-stented segments were analyzed. Overall, NIH thickness and percent NIH area were 29 +/- 41 microm and 10 +/- 4%, respectively. Rates of exposed struts and exposed struts with malapposition were 15% and 6%, respectively. These were more frequent in patients with ACS than in those with non-ACS (18% vs 13%, p <0.0001; 8% vs 5%, p <0.005, respectively). In conclusion, neointimal coverage over a SES at 3-month follow-up is incomplete in ACS and non-ACS. Our study suggests that dual antiplatelet therapy might be continued >3 months after SES implantation.

Aims: The neointimal coverage and intracoronary thrombi within stented segments at 6 months after implantation between sirolimus-eluting stents (SESs) and bare metal stents (BMSs) were compared by direct visualization using angioscopy., Methods and Results: Forty-six patients (36 stable angina and 10 acute coronary syndrome) were treated with 33 SESs and 33 BMSs. Immediately after and 6 months after stenting, each of the stented segments, edge body, and overlapping segment were observed by angioscopy and the grade of neointimal coverage over the stents was classified as 0: absent neointima, 1: visible struts through thin neointima, or 2: invisible struts. The existence of thrombi was also evaluated. The average grade of the neointimal coverage at 6 months follow-up was lower in the SES than that in the BMS (edge: 1.4+/-0.7 vs. 1.9+/-0.2, body: 1.0+/-0.5 vs. 1.8+/-0.5, overlapping segment: 0.6+/-0.7 vs. 1.8+/-0.5; P<0.0001, P<0.0001, P=0.0069, respectively). The frequency of persistence of thrombus was significantly higher in the SESs than that in the BMSs (86 vs. 29%, respectively; P=0.031)., Conclusion: The present study suggested a delayed neointimal stent coverage and slower thrombus disappearance process in the SESs in comparison to the BMSs.