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.Recently, occurrence of late stent thrombosis (LST) after drug‐eluting stent implantation has became a major clinical concern.^1,2,3 A long‐term follow‐up study demonstrated that LST occurs at a constant rate of 0.6% a year for up to 3 years after drug‐eluting stent implantation.³ Pathological investigation shows that delayed arterial healing, characterised by an incomplete endothelialisation and persistence of fibrin, has a key role in the occurrence of LST.^4,5 Moreover, a powerful predictor of LST is the existence of uncovered struts without endothelialisation.⁵ We therefore proposed the hypothesis that the uncovered struts of a sirolimus‐eluting stent (SES) remain for an extended period of time.Coronary angioscopy provides a direct visualisation of the lumen and detailed information on the condition of neointimal stent coverage (NSC) and thrombus.^6,7,8 This imaging modality has the advantage of allowing the identification of an intracoronary thrombus.⁸ Presently, no long‐term angioscopic follow‐up data after SES implantation are available. We herein present our findings as derived from angioscopic examination, focusing on the long‐term serial changes in the NSC, especially the uncovered stent struts, and the presence of thrombus inside the SES.