Assessment and contributing factors of adequate endothelization after drug-eluting stent implantation

Background Adequate endothelialization after drug-eluting stent (DES) implantation is crucial for reducing thrombotic risk. Optical coherence tomography (OCT) defines adequate strut coverage (ASC) as neointimal thickness ≥40 μm, a threshold validated by histological studies; however, its functional significance in vivo remains unclear. Moreover, it is uncertain whether the overall percentage of adequate strut coverage (%ASC) contributes to thrombus prevention or plaque stabilization when individual struts already meet the ≥40 μm criterion. Coronary angioscopy (CAS) uniquely enables direct visualization of intrastent thrombus and evaluation of plaque stabilization through yellow plaque grading. This study aimed to assess functionally adequate endothelialization after DES implantation and to identify its contributing factors. Methods We performed post-hoc analyses of the COLLABORATION 1 and 2 studies, which included serial OCT and CAS assessments at 1 and 12 months after DES implantation. Four DES types were evaluated: durable polymer everolimus-eluting stents (DP-EES), sirolimus-eluting stents (SES), polymer-free biolimus-coated stents (PF-BCS), and dual-therapy sirolimus-eluting stents (DTS). The relationship between %ASC assessed by OCT and neointimal function, defined as absence of intrastent thrombus and presence of white plaque on CAS, was analyzed at both time points. PF-BCS and DTS were classified as "ingenious" DES, and DP-EES and SES as "fundamental." The primary endpoint was to determine the optimal %ASC cut-off value on OCT for thrombus absence and plaque stabilization assessed by CAS. The secondary endpoint was to identify clinical and procedural predictors, including ingenious DESs and the fundamental DESs, associated with good chronic adequate endothelialization (CAE) at 12 months. Results A total of 150 patients with 177 lesions were analyzed. At 12 months, intrastent thrombus and yellow plaque grade were inversely correlated with %ASC, whereas no such correlation was observed at 1 month. This discrepancy likely reflects the limited ability of OCT in the subacute phase to reliably differentiate thrombus from neointimal tissue, as confirmed by both OCT and CAS findings, leading to potential overestimation of endothelialization by OCT at 1 month. The optimal %ASC cut-off values at the chronic phase were 67% for thrombus prevention and 90% for plaque stabilization (Figure). Multivariable analysis identified the use of ingenious DESs, prasugrel therapy, and hypertension as independent predictors of CAE at 12 months (Table). Conclusions Assessment of adequate endothelialization after DES implantation using OCT is more reliable at 12 months than at 1 month post-procedure. The optimal %ASC thresholds at 12 months are 67% for thrombus prevention and 90% for plaque stabilization. Use of prasugrel and ingenious DES may favorably influence chronic endothelialization after DES implantation.