We conducted a posthoc subgroup analysis of the BIOSTEMI ES ( A Comparison of an Ultrathin Strut Biodegradable Polymer Sirolimus-Eluting Stent With a Durable Polymer Everolimus-Eluting Stent for Patients With Acute ST-Segment Elevation Myocardial Infarction Undergoing Primary Percutaneous Coronary Intervention ) Extended Survival (ES) trial which compared ultrathin-strut BP-SES with thin-strut DP-EES in patients undergoing primary PCI for STEMI. The rationale, design, and details regarding study conduct, randomization, blinding, data management, and monitoring have been previously described. Briefly, STEMI patients treated with primary PCI within 24 hours of symptom onset and with at least one culprit lesion suitable for stent implantation were randomized to receive either BP-SES or DP-EES at 10 centers in Switzerland. Patients were followed up to 5 years after the index procedure. The main results of the BIOSTEMI ES trial have been published. For this analysis, patients were stratified by TSL implanted at the culprit site ( ≤ 40 vs >40 mm) based on prior evidence.

Both patients and treating physicians were aware of the assigned treatment, while outcome assessors were blinded to stent allocation. The study protocol adhered to the Declaration of Helsinki and received approval by institutional ethics committees at each participating site. The trial was conducted in collaboration with the Department of Clinical Research, University of Bern, Switzerland, and is reported following the Consolidated Standards of Reporting Trials (CONSORT) guidelines for randomized controlled trials (Supplementary Table I).

The experimental stent ( Orsiro, Biotronik AG, Bülach, Switzerland ) features a thin-strut cobalt-chromium platform measuring 60 µm for stent diameters ≤3.0 mm and 80 µm for diameters >3.0 mm. It is coated with an amorphous hydrogen-rich silicon-carbide layer and an asymmetrical biodegradable poly- l -lactic acid polymer matrix that elutes sirolimus at a dose of 1.4 μg/mm² of stent surface over 12 to 14 weeks, with complete polymer degradation occurring within 24 months.

The control stent ( Xience Prime/Xpedition, Abbott Vascular, Santa Clara, CA ) is a thin-strut (81 µm across all diameters) cobalt-chromium platform that releases everolimus from a durable polymer composed of poly- n -butyl methacrylate and a vinylidene fluoride–hexafluoropropylene copolymer.

The primary endpoint of this analysis was the device-oriented composite endpoint (TLF) defined as the composite of cardiac death, target vessel myocardial reinfarction, or clinically indicated target lesion revascularization, within 5 years of the index procedure. Secondary endpoints included the individual components of TLF; the patient-oriented composite endpoint (POCE), defined as the composite of all-cause death, any myocardial reinfarction, any revascularization, or any stroke; all-cause mortality; definite and definite/probable stent thrombosis according to the Academic Research Consortium criteria; and target vessel failure (TVF), defined as the composite of cardiac death, target vessel myocardial reinfarction, or clinically indicated target vessel revascularization, at 5 years. All endpoint definitions have been described previously. All events were independently adjudicated by a clinical events committee blinded to treatment allocation.

We performed a post hoc subgroup analysis of the BIOSTEMI ES trial to compare clinical outcomes by randomized DES type (BP-SES vs DP-EES) and TSL at the culprit site (≤40 vs >40 mm). This analysis included individual patient data from STEMI patients enrolled in the BIOSCIENCE (Sirolimus-Eluting Stents With Biodegradable Polymer vs Everolimus-Eluting Stents ) randomized trial ( NCT02579031 ) consistent with the primary endpoint analysis of the BIOSTEMI ES trial. Patients were excluded if (1) the culprit lesion was not stented, and (2) no randomized stent was implanted in the culprit lesion.

Categorical variables are presented as counts (%), and continuous variables as mean ± standard deviation. P -values were derived from Student’s t tests, Fisher’s exact tests, generalized linear models, or generalized mixed-effects models for lesion-level data, as appropriate. We used Cox regressions to compare clinical endpoints between DES type (BP-SES vs DP-EES) and TSL subgroup (≤40 vs >40 mm) and their interaction. Time-to-first event was used for all clinical endpoints. We reported hazard ratios (HR), their associated 95% confidence intervals (CI), P -values from Cox regressions, and we derived Kaplan–Meier curves. We performed a sensitivity analysis in which the TSL subgroups were compiled considering all treated (culprit and nonculprit) lesions. We also performed unadjusted and adjusted Cox regression analyses to evaluate the association between TLF at 5 years and TSL modeled as a continuous variable. In both models, the interaction between DES type (BP-SES vs DP-EES) and TSL was included as a fixed effect. The adjusted models included the following variables as covariates; multivessel treatment, age, ejection fraction, previous coronary artery bypass grafting, and bifurcation lesion treatment . Significance threshold was set to 0.05. Statistical analyses were performed using Stata 17 ( StataCorp, College Station, TX ).