ENVISION IDE Trial: Safety and Effectiveness of NAVITOR in Transcatheter Aortic Valve Implantation

Key Inclusion Criteria: 1. Subject who is deemed to be at intermediate or low risk for open surgical aortic valve replacement: 1. Intermediate risk: estimated risk of overall surgical mortality ≥ 3% and \< 8% at 30 days 2. Low risk: estimated risk of overall surgical mortality \< 3% at 30 days Estimated risk of overall surgical mortality includes consideration of the Society of Thoracic Surgeons (STS) risk score, overall clinical status, and other clinical co-morbidities unmeasured by the risk calculator 2. New York Heart Association (NYHA) Functional Classification of II, III, or IV 3. Degenerative aortic valve stenosis Key Exclusion Criteria: 1. In the opinion of the Investigator, life expectancy is less than 2 years 2. Evidence of an acute myocardial infarction \[defined as ST-segment elevation myocardial infarction (STEMI) or non-ST-segment elevation myocardial infarction (NSTEMI) with acute ischemia symptoms and troponin elevation\] within 30 days prior to index procedure 3. Untreated clinically significant coronary artery disease requiring revascularization 4. Any percutaneous coronary or peripheral interventional procedure performed within 30 days prior (except pacemaker or implantable cardioverter defibrillator (ICD) implant) to index procedure or planned within 30 days following the index procedure 5. Blood dyscrasias as defined: leukopenia (WBC \< 3000 mm3), acute anemia (Hb \< 9 g/dL), thrombocytopenia (platelet count \< 50,000 cells/mm³); history of bleeding diathesis or coagulopathy 6. Active peptic ulcer or upper GI bleeding within 3 months prior to index procedure that would preclude anticoagulation 7. Recent (within 6 months prior to index procedure date) cerebrovascular accident (CVA) or a transient ischemic attack (TIA) 8. Renal insufficiency (creatinine \> 3.0 mg/dL or eGFR \< 30 ml/min/1.73m2) and/or end stage renal disease requiring chronic dialysis 9. Hostile chest or conditions or complications from prior surgery that would make the subject be considered high surgical risk (i.e., mediastinitis, radiation damage, abnormal chest wall, porcelain aorta, adhesion of aorta or internal mammary artery to sternum, etc.) 10. Significant frailty as determined by the heart team (after objective assessment of frailty parameters) that would indicate high or extreme surgical risk 11. Mixed aortic valve disease (aortic stenosis and aortic regurgitation with predominant aortic regurgitation 3-4+) 12. Aortic valve is a unicuspid or bicuspid valve as verified by echocardiography or CT. 13. Severe ventricular dysfunction with LVEF \< 30% as measured by resting echocardiogram 14. Pre-existing prosthetic heart valve or other implant (such as prosthetic ring or transcatheter edge-to-edge repair (TEER) clip) in any valve position 15. Severe circumferential mitral annular calcification (MAC) which is continuous with calcium in the left ventricular outflow tract (LVOT) 16. Severe (greater than or equal to 3+) mitral regurgitation or severe mitral stenosis 17. Minimum access vessel diameter of \< 5.0 mm for small FlexNav Delivery System and \< 5.5 mm for large FlexNav Delivery System 18. Eccentricity ratio of the annulus \< 0.73 Additional Exclusion Criteria for Pivotal Randomized Cohort 1. Hostile Chest or conditions or complications from prior surgery that would make the subject be considered high surgical risk 2. Significant frailty as determined by the heart team (after objective assessment of frailty parameters) that would indicate high or extreme surgical risk 3. Mixed aortic valve disease 4. Aortic valve is a unicuspid or bicuspid valve as verified by echocardiography or CT 5. Inadequate aortic valve calcification 6. Pre-existing prosthetic heart valve or other implant (such as prosthetic ring or transcatheter edge-to-edge repair (TEER) clip) in any valve position Additional Exclusion Criteria for ViV Cohort 1. Failing valve has moderate or greater paravalvular regurgitation. 2. Known severe prosthesis-patient mismatch 3. Failing valve is unstable, rocking, or not structurally intact. 4. Patient has a pre-existing prosthetic heart valve or other implant (such a prosthetic ring with a rigid support structure or transcatheter edge-to-edge repair clip) in any valve position other than aortic. 5. Bioprosthetic valve diameter that would not accommodate implantation of the Navitor Valve. 6. Increased risk of coronary obstruction by prosthetic leaflets of the index valve Additional Exclusion Criteria for bicuspid cohort 1. In the opinion of the Investigator life expectancy is less than 1 year 2. Inadequate or severe aortic valve calcification and/or anatomical features that would preclude safe delivery of the valve