BACKGROUND: Transcatheter aortic valve implantation is an established, guideline-endorsed treatment for severe aortic stenosis. Precise sizing of the balloon-expandable Myval transcatheter heart valve (THV) series with the aortic annulus is facilitated by increasing its diameter in 1·5 mm increments, compared with the usual 3 mm increments in valve size. The LANDMARK trial aimed to show non-inferiority of the Myval THV series compared with the contemporary THVs Sapien Series (Edwards Lifesciences, Irvine, CA, USA) or Evolut Series (Medtronic, Minneapolis, MN, USA).

METHODS: In this prospective, multinational, randomised, open-label, non-inferiority trial across 31 hospitals in 16 countries (Germany, France, Sweden, the Netherlands, Italy, Spain, New Zealand, Portugal, Greece, Hungary, Poland, Slovakia, Slovenia, Croatia, Estonia, and Brazil), 768 participants with severe symptomatic native aortic stenosis were randomly assigned (1:1) to the Myval THV or a contemporary THV. Eligibility was primarily decided by the heart team in accordance with 2021 European Society of Cardiology guidelines. As per the criteria of the third Valve Academic Research Consortium, the primary endpoint at 30 days was a composite of all-cause mortality, all stroke, bleeding (types 3 and 4), acute kidney injury (stages 2-4), major vascular complications, moderate or severe prosthetic valve regurgitation, and conduction system disturbances resulting in a permanent pacemaker implantation. Non-inferiority of the study device was tested in the intention-to-treat population using a non-inferiority margin of 10·44% and assuming an event rate of 26·10%. This trial is registered with ClinicalTrials.gov, NCT04275726, and EudraCT, 2020-000137-40, and is closed to new participants.

FINDINGS: Between Jan 6, 2021, and Dec 5, 2023, 768 participants with severe symptomatic native aortic stenosis were randomly assigned, 384 to the Myval THV and 384 to a contemporary THV. 369 (48%) participants had their sex recorded as female, and 399 (52%) as male. The mean age of participants was 80·0 years (SD 5·7) for those treated with the Myval THV and 80·4 years (5·4) for those treated with a contemporary THV. Median Society of Thoracic Surgeons scores were the same in both groups (Myval 2·6% [IQR 1·7-4·0] vs contemporary 2·6% [1·7-4·0]). The primary endpoint showed non-inferiority of the Myval (25%) compared with contemporary THV (27%), with a risk difference of -2·3% (one-sided upper 95% CI 3·8, pnon-inferiority<0·0001). No significant difference was seen in individual components of the primary composite endpoint.

INTERPRETATION: In individuals with severe symptomatic native aortic stenosis, the Myval THV met its primary endpoint at 30 days.

FUNDING: Meril Life Sciences.