Strut thickness differences among drug-eluting stents (DES) have little impact on clinical outcomes of percutaneous coronary intervention (PCI) when implanted with intravascular imaging guidance, new trial data from Japan report. The study, published online Monday and in the July 11 issue of JACC: Cardiovascular Interventions, is the first clinical trial to compare the efficacy of ultrathin-strut biodegradable-polymer sirolimus-eluting stents (BP-SES) and thin-strut durable-polymer everolimus-eluting stents (DP-EES) specifically using intravascular ultrasound (IVUS) or optical coherence tomography (OCT)-guided implantation. Led by Masato Nakamura, MD, PhD, from Toho University Ohashi Medical Center, Meguro-ku, Japan, the researchers behind the trial noted that the clinical outcomes of PCI are influenced by multiple factors, including stent design, lesion morphology and procedural technique but that most randomized controlled trials of DES have been limited by the use of angiography-guided DES implantation. They noted that stent strut thickness has been suggested to be an important determinant of the clinical outcomes of PCI, with meta-analysis data suggesting that ultrathin-strut DES are associated with improvements in clinical outcomes. “Recently, DES implantation guided by IVUS or OCT has demonstrated superiority to angiography-guided DES implantation regarding the occurrence of stent restenosis and thrombosis,” said Nakamura and colleagues. “Hence, the optimization of PCI using guidance with IVUS or OCT may minimize the procedural impact and thereby allow more accurate assessment of the effect of DES strut thickness.” Study setup The CASTLE trial set out to assess whether stent strut differences between an ultrathin-strut BP-SES (60-80 µm) and a thin-strut DP-EES (81 µm) implanted with guidance by IVUS or OCT would have an impact on target lesion failure (TLF) at 1 year after PCI. Nakamura and colleagues noted that between May 2019 and March 2020, a total of 6,774 patients underwent PCI at 65 medical institutions in Japan, of whom 1,515 patients were screened for eligibility. After excluding 75 patients, the remaining 1,440 eligible patients were randomly assigned to the BP-SES group (n = 722) or the DP-EES group (n = 718). There were no significant differences in patient characteristics or angiographic findings. Patients in the BP-SES group and the DP-EES group had mean age of 70.1 years and 70.4 years, respectively; while 39.3% of the BP-SES group and 38.9% of the DP-EES group had diabetes mellitus, and 14.5% of the BP-SES group and 14.1% of the DP-EES group had acute coronary syndrome (ACS). At 1 year after the index PCI, 693 patients (95.9%) in the BP-SES group and 686 patients (95.5%) in the DP-EES group were followed up. The primary endpoint was TLF at 1 year – defined as the composite of cardiac death, target vessel-related myocardial infarction (MI) and clinically driven target lesion revascularization (TLR). Major secondary endpoints were the patient-oriented composite endpoint of all-cause death, all MI and all revascularization, along with each component of TLF and stent thrombosis (ST) at 1 year after the index PCI. Key findings TLF occurred in 6.0% patients in the BP-SES group and 5.7% of patients in the DP-EES group (hazard ratio [HR] 1.04; 95% confidence interval [CI]: 0.68−1.60; p=0.85). Nakamura and colleagues noted that the noninferiority of the BP-SES to the DP-EES for the primary endpoint was established, with an absolute risk difference of 0.25% and an upper limit of the 1-sided 95% CI of 2.67% (P = 0.040 for noninferiority; P = 0.845 for superiority). “Results for the primary endpoint were consistent across various subgroups, including stent diameter, and the sensitivity analysis did not reveal interactions across subgroups,” said the authors, noting that the respective implementation rates of dual antiplatelet therapy for the BP-SES and the DP-EES were as follows: at 6 months after index PCI, 71.8% and 70.9%, and at 1 year, 43.3% and 44.3% The team concluded that the ultrathin-strut BP-SES was not inferior to thin-strut DP-EES with respect to 1-year clinical outcomes when they were implanted under IVUS or OCT guidance. “Therefore, strut thickness differences between DES had no observed impact on clinical outcomes,” they confirmed. Nakamura and colleagues noted that patients taking part in the CASTLE trial will be followed for 3 years after the index PCI to examine the long-term clinical outcomes of both ultrathin-strut and thin-strut DES implanted under guidance with IVUS or OCT. “The accumulation of further clinical evidence for not only the efficacy but also the safety of intravascular imaging guidance-based implantation for these 2 DES of different stent strut thicknesses will be expected,” they said. Stent strut thickness vs. better guidance Writing in an accompanying editorial, Konstantinos C. Koskinas, MD, MSc, from Bern University Hospital, Switzerland, noted that the use of intracoronary imaging in essentially all patients in the CASTLE trial significantly affected the observed findings. “In recent years, a growing body of evidence has shown that intracoronary imaging improves PCI outcomes across a broad spectrum of patients and lesions; the value of IVUS and OCT for procedural guidance is increasingly appreciated among operators, and their use is recommended in current clinical practice guidelines,” said Koskinas. “One can argue that guidance with IVUS or OCT did contribute to optimized stenting outcomes in CASTLE,” he commented. “It is also reasonable to speculate that this might have alleviated potential efficacy differences between the 2 stent types that might have emerged if the interventions had been performed under angiographic guidance alone.” The editorialist noted, however, that this interpretation remains hypothetical, warning that properly designed studies would be required to definitively address this question. “If anything, the fact that several equally good (ie, noninferior) stents are currently available on contemporary catheterization laboratory shelves can only be good news for our patients,” he said. “In the meantime, further research should continue the search for the best possible stent design, implantation technique, and postprocedural management for each individual patient.” Sources: Nakamura M, Kadota K, Nakagawa Y, et al. Ultrathin, Biodegradable-Polymer Sirolimus-Eluting Stent vs Thin, Durable-Polymer Everolimus-Eluting Stent. JACC Cardiovasc Interv 2022;15:1324-1334. Koskinas KC. Impact of Stent Design and Strut Thickness on PCI Outcomes: Is There Still Room for Superiority? JACC Cardiovasc Interv 2022;15:1335-1337. Image Credit: Belezapoy – stock.adobe.com