Serial assessment of bioresorbable-polymer sirolimus-eluting stent by coronary angioscopy and optical coherence tomography

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Case studyA 68-year-old man was diagnosed with silent myocardial ischemia with multiple coronary lesions and underwent a percutaneous coronary intervention (PCI). Two bioresorbable-polymer sirolimus-eluting stents (BP-SES, 2.5×38 mm and 2.5×28 mm Ultimaster, Terumo Corporation, Tokyo, Japan) were implanted stepwise in the left circumflex artery (LCX) and the left anterior descending artery (LAD). Serial assessment by coronary angioscopy (CAS) and optical coherence tomography (OCT) was carried out at the time of PCI for another lesion and follow-up coronary angiographies. We obtained the images of BP-SES in LCX and LAD at 1 and 3 months and 2 and 8 months after PCI, respectively. CAS showed insufficient strut coverage (grade 0–1) and red mural thrombi at 1 and 2 months after PCI (Fig. 1a and b). OCT showed many uncovered struts and interstrut hollows (Fig. 1a′ and b′). Three-month follow-up indicated an improvement in strut coverage (grade 1–2), but there were residual mural thrombi and interstrut hollows (Fig. 1c and c′). Assessment by CAS at 8 months after PCI showed well-covered struts (grade 2–3) and disappearance of mural thrombi (Fig. 1d). OCT also showed improved strut coverage (Fig. 1d′). BP-SES is a new-generation, thin-strut, abluminal-coating sirolimus-eluting stent with a biodegradable polymer. The polymer is metabolized to fully eliminate over 3–4 months, and the drug is released simultaneously with polymer biodegradation. Thereafter, the stent is expected to be a bare-metal stent, which enhances strut endothelialization to prevent stent thrombosis. The CENTURY II trial proved the noninferiority of BP-SES to a cobalt–chromium everolimus-eluting stent at the 9-month follow-up 1. Further, early coverage of stent struts after the implantation of BP-SES is expected to contribute toward shortening the duration of DAPT. In the present case, however, CAS showed mural red thrombi inside stents, which is not clearly detected by OCT, in the early follow-up within 3 months after stent implantation. However, late follow-up observation by CAS at 8 months after PCI did not clearly detect thrombi. Even though the clinical significance of such in-stent mural thrombus is still unclear, it makes us consider the continuation of DAPT in the early period after BP-SES implantation. In addition, OCT showed the existence of interstrut hollows in the early follow-up period, especially at 1 month after PCI for LCX (Fig. 1a′). CAS also showed heterogeneity of strut coverage during the same follow-up period. A previous study indicated that multiple interstrut hollows may be closely related to peri-stent contrast staining in lesions after first-generation sirolimus-eluting stent implantation 2, and it could predict late stent thrombosis of the lesion 3. In contrast to these reports on first-generation SES, interstrut hollows of BP-SES in this case decreased gradually over time. We speculate that this process may be a benefit from the biodegradable property of the polymer of BP-SES. To the best of our knowledge, the present case is the first reported serial observation of BP-SES by CAS and OCT from an early to a late follow-up period, and it showed the vascular healing process after stent implantation.AcknowledgementsConflicts of interestThere are no conflicts of interest.

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