Over the last years, several randomized studies comparing transcatheter aortic valve implantation (TAVI) to surgical aortic valve replacement (SAVR) have established TAVI as a treatment option in symptomatic patients with aortic stenosis (AS) (1,2,3). Most transcatheter heart valves (THV) available are designed on either a balloon-expandable (BE) or a self-expanding (SE) concept.

Despite major differences, both designs are recommended to be used indifferently in most of the clinical situations and a significant number of centers only implant one of this two THV design. It remains unclear however, whether these 2 very different THV concepts are achieving similar or different clinical outcomes and could be considered a single "Class" of device. While there is an urgent clinical need to clarify this issue in an exponentially growing therapeutic field, to date no large randomized study powered to compare the 2 THV designs on individual endpoints has been conducted or initiated. Recently, two large-scale French registry-based propensity matched analyses, including more than 30,000 patients, have reported a higher 90 days and 1-year mortality with the use of SE as compared to BE-valve (4,5). However, as the propensity-score matching-approach cannot rule out residual confounders, and as some of the most recent THV iterations were not part of the investigation, there is an urgent need to conduct a randomized trial sufficiently powered to compare head-to-head the latest generation of SE and BE-valve on all-cause mortality. In addition, two small randomized studies have recently showed the inferiority of a new SE-valve compared to BE-valve and SE-THV (SCOPE1 trial, J Lanz. Lancet. 2019 Nov 2;394(10209):1619-1628. and SCOPE 2 trial, Circulation in press), thus further questioning wether THV should be considered as a single "Class" regardless the THV design.

The objective of the present randomized clinical investigation will be to evaluate the impact of THV design (SE vs BE) on the risk of all-cause mortality at 90 days and 1 year.

The present clinical investigation will the first randomized clinical investigation to compare head to head the benefit of BE-valve over SE-valve on total mortality and /or disabling stroke at 90 days and 1-year using a superiority design. Previous head-to-head studies included only a small number of patients, non-inferiority designs and combined endpoints. This clinical investigation will be the first to generate sufficient evidences to change clinical practice and international guidelines to clarify whether one THV design is superior (or not) to the other one (BE vs SE-valve). The result of the clinical investigation is key for clinicians indicating the treatment and for the patients receiving the treatment

The study population will be comprised of all patients with severe, calcific, symptomatic aortic stenosis eligible to percutaneous transfemoral TAVI with BE or SE-valve according to the investigating center heart team.

The inclusion/exclusion criteria are limited and primarily intend to select patient eligible to both BE and SE-valve. This allows for a study cohort whose composition is expected to be close to an all-comers cohort and therefore representative for the standard TAVI population seen in daily practice.

Inclusion Criteria:

• Symptomatic severe aortic stenosis defined according to the current echocardiography criteria of the European Society of Cardiology guidelines2.
• Heart team of the investigating center agrees that the patient is eligible to TAVI with BE-valve SAPIEN 3 (Edwards Lifesciences©) (or further iterations of the same family) OR TAVI with the SE-valve Evolut-R/pro (Medtronic©) (or futher iterations of the same family).
• Heart team of the investigating center agrees that TAVI is feasible via percutaneous transfemoral approach.
• Written informed consent to the BEST study
• Written informed consent to the FRANCE-TAVI registy
• All valve anatomy are authorized (bicuspid or tricuspid aortic valve)

Exclusion Criteria:

• Age < 18 years old
• Patient with legal protection
• Non-affiliation to a social security scheme
• Pregnancy
• Subject participating in another research protocol on TAVI procedure
• Patients presenting with an anatomy that is regarded unsuitable for the implantation of one of the two valve types
• TAVI through nontransfemoral approach or surgical cutdown
• Valve-in-valve procedure (TAVI in TAVI or TAVI in surgical aortic bioprosthesis)
• Implantation of Accurate Neo or Accurate Neo2 valve (Boston scientific)
• Severe aortic regurgitation (>3+)
• Refusal to participate to FRANCE-TAVI registry