This is a prospective, randomised, international, multicentre, open-label, investigator-initiated study in patients undergoing valve-in-valve Transcatheter Aortic Valve Implantation (TAVI) for failed surgical aortic bioprosthesis. A total of 111 patients will be randomized in a 2:1 ratio, with 74 patients assigned to self-expanding Hydra THV Series and 37 patients assigned to BEV (Sapien THV Series and MyVal THV Series).

"Inclusion Criteria":

1. Male or Female patient ≥18 years of age
2. Severe hemodynamic valve deterioration of a surgically implanted bioprosthetic aortic valve, including severe valve stenosis and/or severe valve regurgitation, as determined by the Heart Team assessment
3. Patients eligible for transfemoral TAVI with both study THV platforms per heart team consensus.
4. TAVI (with or without fracture of surgical valve) is suitable with commercially available sizes of both Hydra and Sapien/Myvall BEVs.
5. Patient has been informed of the nature of the study and agrees to its provisions and has provided written informed consent as approved by the Ethics Committee and is willing to comply with all protocol-required (follow-up) evaluations.

"Exclusion criteria":

1. Patients unwilling to provide an informed consent, or whose legal representative object to their participation in the study
2. Patient is a woman who is pregnant or nursing (a pregnancy test must be performed within 7 days prior to the index procedure in woman of child-bearing potential according to local practice)
3. Patients with non-transfemoral TAVI access.
4. Surgical or transcatheter valve in mitral position (mitral rings are not an exclusion)
5. Patients who had received the Bentall procedure.
6. Patients with active bacterial endocarditis or ongoing sepsis ≤6 months prior to the index procedure
7. Echocardiographic evidence of intracardiac mass, thrombus or vegetation
8. Acute myocardial infarction ≤30 days before the intended TAVI procedure
9. Known hypersensitivity or contraindication to antithrombotic therapy (or inability to be anticoagulated during the procedure), nitinol, or sensitivity to contrast media which cannot be adequately pre-medicated
10. Patients with severe left ventricular dysfunction and ejection fraction <30% or hemodynamic instability requiring inotropic agent or mechanical support.
11. Patients with significant renal insufficiency (serum creatinine >3.0 mg/dL (265.5μmol/L)) and/or end stage renal disease requiring chronic dialysis
12. Patients who are at very high risk of coronary obstruction (e.g., VIVID classification IIB, IIIB, IIIC) and are judged by the heart team to require upfront leaflet laceration (e.g. Basilica or Unicorn procedure) or chimney or snorkel stenting as part of the TAVI procedure.
13. Any planned surgical or peripheral procedure to be performed in next 30-day after the index procedure
14. Life expectancy <12 months due to non-cardiac co-morbid conditions including carcinomas, chronic liver disease, chronic renal disease or chronic end-stage pulmonary disease