BACKGROUND: Transcatheter aortic valve implantation (TAVI) is a guideline-directed treatment for severe aortic stenosis and degenerated aortic bioprostheses. When new transcatheter heart valve (THV) platforms for TAVI are launched, they should be compared with best-in-practice contemporary THVs for their short-term and long-term performance. The COMPARE-TAVI 1 trial was designed to provide a head-to-head comparison of the SAPIEN 3 or SAPIEN 3 Ultra THVs and the Myval or Myval Octacor THVs. METHODS: This multicentre, all-comers, randomised, non-inferiority trial was done at three university hospitals in Denmark. Eligible patients were aged 18 years or older, scheduled for transfemoral TAVI, and eligible for treatment with SAPIEN 3 THVs or Myval THVs. Patients were randomly assigned (1:1) to treatment with SAPIEN 3 (29 mm diameter) or SAPIEN 3 Ultra (20 mm, 23 mm, or 26 mm diameter) THVs or Myval or Myval Octacor THVs (20-32 mm diameter). The TAVI procedure was performed according to local practice and under local anaesthesia unless leaflet laceration was performed. The primary endpoint was a composite of death, stroke, moderate or severe aortic regurgitation, or moderate or severe haemodynamic THV deterioration at 1 year according to Third Valve Academic Research Consortium criteria. All patients assigned to THV treatment were included in the intention-to-treat analysis, and all patients who were treated as randomly assigned were included in the per-protocol analysis. With an expected event rate of 13%, the prespecified non-inferiority margin was 5·3%. This trial is registered with ClinicalTrials.gov, NCT04443023, and is closed to accrual. FINDINGS: Between June 15, 2020, and Nov 3, 2023, 1031 patients were enrolled. Enrolment was paused twice because of patent-related legal proceedings. Of 1031 patients, 517 patients were randomly assigned to SAPIEN 3 THVs and 514 to Myval THVs. The median patient age was 81·6 years (IQR 77·6-85·0), and 415 (40%) of 1031 patients were female and 616 (60%) were male. The primary endpoint occurred in 67 (13%) of 517 patients randomly assigned to SAPIEN 3 THVs versus 71 (14%) of 514 patients randomly assigned to Myval THVs (risk difference -0·9% [one-sided upper 95% CI 4·4%]
p INTERPRETATION: Myval THVs were non-inferior to SAPIEN 3 THVs in terms of a 1-year composite endpoint of death, stroke, moderate or severe aortic regurgitation, or moderate or severe haemodynamic THV deterioration. FUNDING: Meril Life Sciences, Vingmed Denmark, the Danish Heart Foundation, and the Central Denmark Region.