BIOVALVE - I / II Clincial Investigation

Inclusion Criteria: 1. The subject is ≥65 years 2. The subject has provided written informed consent 3. Subject is willing to participate in the clinical investigation and to comply with all of the study procedures and follow-up visits 4. NHYA class ≥II 5. High surgical risk: Logistic EuroSCORE-I ≥20% (or equivalence of EuroSCORE-II) or STS score ≥10% or co-morbidity judged by the heart team (consisting of at least one interventional cardiologist and one cardiac surgeon) to pose an absolute or relative contraindication for conventional aortic valve replacement according to VARC-2 6. Severe symptomatic calcific aortic valve stenosis characterized by mean aortic gradient \>40 mm Hg or peak jet velocity \>4.0 m/s or effective orifice area (EOA) of \<1.0 cm2 (\<0.6 cm2/m2 body surface area) 7. Annulus diameter as determined by multi-slice computed tomography (MSCT) from 23-26 mm Exclusion Criteria: 1. Trans-esophageal echocardiogram (TEE) is contraindicated 2. Congenital bicuspid or unicuspid valve 3. Left ventricular outflow tract (LVOT) obstruction such as hypertrophic obstructive cardio myopathy (HOCM) or subject presenting with systolic anterior motion (SAM). Evidence of intra cardiac mass, thrombus or vegetation 4. Transfemoral access vessel characteristics that would preclude safe placement of a 18 French sheath 5. Vessel and/or anatomical characteristics that would preclude safe delivery of the BIOVALVE prosthesis to the ascending aorta and/or placement of the prosthesis 6. Anatomical restrictions such as shallow sinuses with heavily calcified leaflets, low height of coronary ostia, extreme tortuosity of the aortic arch, thoracic (TAA) or abdominal (AAA) aortic aneurysm, presence of endovascular stent graft 7. Severe mitral regurgitation grade \>3 8. Severe mitral stenosis 9. Prosthetic mitral valve 10. Severe left ventricular dysfunction with left ventricular ejection fraction (LVEF) \<20% 11. Hemodynamic instability 12. Percutaneous coronary intervention (PCI) within 30 days prior to index procedure and / or planned PCI during index procedure 13. Renal insufficiency (creatinine \>2.5 mg/dl) or subject under dialysis and/or renal replacement therapy 14. Any cerebrovascular event or transient ischemic attack (TIA) within 180 days prior to TAVI procedure 15. Evidence of acute myocardial infarction (defined as ≥2 fold CK level or in absence of CK a ≥3 fold CKMB level above the upper range limit within ≤30 days prior to TAVI procedure) 16. Blood dyscrasia defined as: leucopenia (WBC \<1000 mm³), thrombocytopenia (platelet count \<50'000 cells/mm³), history of bleeding diathesis requiring blood transfusion 17. Ongoing sepsis or suspected active endocarditis 18. Active peptic ulcer or gastrointestinal bleeding within last 3 months that would preclude anticoagulation 19. Subject refuses blood transfusion 20. Known hypersensitivity to, or contraindication to nitinol, anticoagulation/antiplatelet regimes, any other medications required for the procedure or post-procedure as determined by the heart team, or sensitivity to contrast media which cannot be adequately pre-medicated 21. Need for emergency TAVI intervention, or other medical, social, or psychological conditions that in the opinion of the heart team precludes the subjects from appropriate consent or adherence to protocol required follow-up exams 22. Expectation that subject will not improve despite treatment of aortic stenosis 23. Estimated life expectancy of less than 12 months due to associated non-cardiac co-morbidities 24. Severe pulmonary hypertension (\> 60 mm Hg assessed by continuous wave Doppler, TTE) or clinical signs of acute severe right ventricular dysfunction 25. Currently participating in another investigational drug or device study where primary endpoint has not been reached yet