Impact of strut thickness on vessel responses after polymer-free biolimus A9-coated stents: both optical coherence tomographic and coronary angioscopic evaluations

Background/Introduction The stainless-steel polymer-free biolimus A9-coated stent (SS-BCS) has no polymer, and it demonstrated superior safety and efficacy compared to bare-meta stent with 1-month dual-antiplatelet therapy. However, SS-BCS had a thicker stent strut with 112-120μm compared to the other newer generation stents, which impacted on the worse clinical outcomes of SS-BCS compared to those of ultra-thin strut drug-eluting stent. Recently, the next generation cobalt-chromium thin-strut polymer-free biolimus A9-coated stent (CoCr-BCS) with 84-88μm was developed and better clinical outcomes are expected. However, the vessel responses after CoCr-BCS implantation have not been elucidated. Purpose This study aimed to compare the vessel responses of CoCr-BCS to those of SS-BCS at 12 months after stent implantation using optical coherence tomography (OCT) and coronary angioscopy (CAS). Methods The Collaboration-Ultra study included 52 lesions from 44 patients who underwent percutaneous coronary intervention (PCI) with CoCr-BCS implantation and 71 lesions from 51 patients with SS-BCS implantation. OCT and CAS examinations were performed at 12 months after PCI, and the vessel responses were compared between CoCr-BCS and SS-BCS. The primary outcome was the mean neointimal thickness evaluated by OCT. The secondary outcomes were adequate strut coverage (neointimal thickness ≥40 μm) on OCT and dominant neointimal coverage (NIC) grade on CAS. NIC grade on CAS was graded as follows: grade 0, stent struts exposed; grade 1, struts bulging into the lumen, although covered; grade 2, struts were embedded by the neointima but were seen translucently; grade 3, struts fully embedded and invisible. Linear regression model and ordinal logistic model analyses were performed to determine the impact of CoCr-BCS on OCT and CAS findings at 12 months, respectively. Results OCT showed that the mean neointimal thickness was significantly thicker in CoCr-BCS than in SS-BCS (172±56μm vs. 140±55μm, P=0.006). The adequate strut coverage rate was significantly higher in CoCr-BCS than in SS-BCS (94±7% vs. 84±14%, P<0.001). CAS demonstrated that the dominant NIC was greater in CoCr-BCS than in SS-BCS (P=0.029, Figure). After multivariate analyses, CoCr-BCS had positive impact on mean neointimal thickness (P=0.020), adequate strut coverage (P<0.001) and dominant NIC grade (P=0.027, Table). Conclusion CoCr-BCS demonstrated thicker neointimal thickness, higher adequate coverage rates and better NIC grade compared to SS-BCS, which would be driven by the difference of strut thickness. These results suggest strut thickness is key for better arterial healing even after polymer-free biolimus A9-coated stents.Figure Table