Clinical Trial to Evaluate the Safety and Effectiveness of Using the Tendyne Transcatheter Mitral Valve System for the Treatment of Symptomatic Mitral Regurgitation

Inclusion Criteria: 1. Symptomatic, moderate-to-severe or severe mitral regurgitation (MR ≥ Grade III per American Society of Echocardiography criteria), or severe mitral annular calcification (MAC), where a transcatheter therapy is deemed more appropriate than open surgery by the local site heart team. Note: MR and MS severity must be determined by assessment of a qualifying transesophageal echocardiogram (TEE) and transthoracic echocardiogram (TTE), obtained within 120 days prior to subject consent, and must be confirmed by the Echocardiography Core Laboratory. Note: Patients with severe MAC must have symptomatic mitral valve disease associated with MR≥ Grade III, or severe mitral stenosis (MS), or both moderate MR and moderate MS as assessed by the Echocardiography Core Laboratory. 2. NYHA Functional Classification ≥ II (if Class IV, patient must be ambulatory). 3. The local site heart team determines that the subject has been adequately treated per applicable standards for coronary artery disease (e.g., revascularization), left ventricular dysfunction (e.g., cardiac resynchronization therapy) and heart failure (e.g., GDMT). The SEC must concur that the subject has been adequately treated. 4. The local site heart team and the SEC concur on the intended study cohort for the subject. Randomized cohort: Eligibility for this cohort is limited to subjects where the local site heart team deems the mitral valve anatomy is suitable for TEER and are within approved Mitra Clip indications, which must be confirmed by experienced Mitra Clip operators within the SEC. Subjects with primary MR must be at prohibitive surgical risk, while subjects with secondary MR must be symptomatic despite maximally-tolerated guideline-directed medical therapy and meet the Mitra Clip Indications for Use. Non-repairable cohort: Eligibility for this cohort is limited to subjects where the local site heart team deems the mitral valve anatomy is not suitable for TEER with Mitra Clip or does not meet Mitra Clip indications, which must be confirmed by experienced Mitra Clip operators from the SEC. Severe MAC cohort: Eligibility for this cohort is limited to subjects where the local site heart team deems the degree of MAC renders the subject unsuitable for mitral valve surgery. Severe MAC CAP cohort: Eligibility for this cohort is identical to the original Severe MAC cohort. 5. Age 18 years or older at time of consent. 6. Subject has been informed of the nature of the trial and agrees to its provisions, including the possibility of randomization to the Control group, complying with trial required testing, medications, and follow-up visits, and has provided written informed consent. Exclusion Criteria: 1. Mitral valvular vegetation or mass. 2. Left Ventricle or Left Atrium thrombus. 3. Chest condition that prevents transapical access. 4. LVEF less than 25% assessed by the site based on a TTE obtained within 120 days prior to subject consent. Note: LVEF will be principally based on TTE and confirmed by the Echocardiography Core Laboratory. 5. LVEDD \> 7.0 cm assessed by the site based on a TTE obtained within 120 days prior to subject consent. Note: A qualifying LVEDD must be confirmed by the Echocardiography Core Laboratory. 6. Prior surgical or interventional treatment of mitral valve involving implantation of prosthetic material (e.g. valve repair or replacement, or Mitra Clip). 7. Mitral pathoanatomy and LVOT anatomy deemed not suitable for Tendyne transcatheter mitral valve implantation. 8. Aortic valve disease requiring surgery or transcatheter intervention. 9. Tricuspid valve disease requiring surgery or transcatheter intervention. 10. Severe tricuspid regurgitation or severe right ventricular dysfunction. 11. Any surgical or interventional procedure within the period of 60 days prior to or planned procedure 60 days following subject registration. 12. Implant or revision of CRT device within 90 days prior to intended subject registration. 13. Myocardial infarction within 30 days prior to intended subject registration. 14. Symptomatic, unresolved multi-vessel or unprotected left main coronary artery disease (e.g., active ischemia) requiring stenting or CABG. 15. CVA within 6 months prior to intended subject registration. 16. Unresolved severe symptomatic carotid stenosis (\> 70% by ultrasound). 17. Cardiogenic shock or hemodynamic instability requiring inotropes or mechanical support devices at the time of planned implant procedure. 18. Hypertrophic or restrictive cardiomyopathy, or constrictive pericarditis. 19. Any of the following: leukopenia, acute anemia, thrombocytopenia, history of bleeding diathesis, or coagulopathy if cannot be adequately treated. 20. History of endocarditis within 6 months of planned implant procedure. 21. Active systemic infection requiring antibiotic therapy. 22. Known hypersensitivity or contraindication to procedural or post-procedural medications (e.g., contrast solution, anti-coagulation or antiplatelet therapy) that cannot be adequately managed medically. 23. Subjects in whom TEE is contraindicated or high risk. 24. Known hypersensitivity to nickel or titanium. 25. Subject is undergoing hemodialysis due to chronic renal failure. 26. Subject has pulmonary arterial hypertension (fixed PAS \>70mmHg). Note: If PAS \> 70mmHg, site must provide documentation PAS is not fixed in order to be eligible. 27. Subject has COPD requiring continuous home oxygen therapy or chronic outpatient oral steroid use. 28. Subjects with non-cardiac comorbidities that are likely to result in a life expectancy of less than 12 months. 29. Modified Rankin Scale ≥ 4 disability. 30. Status 1 heart transplant or prior orthotopic heart transplantation. 31. Pregnant, lactating, or planning pregnancy during the clinical investigation follow-up period. Note: Female subjects of childbearing age should be instructed to use safe contraception (e.g. intrauterine devices, hormonal contraceptives: contraceptive pills, implants, transdermal patches hormonal vaginal devices, injections with prolonged release). 32. Currently participating in an investigational drug or another device trial that has not reached its primary endpoint. Note: Trials requiring extended follow-up for products that were investigational, but have since become commercially available, are not considered investigational trials. 33. Presence of other anatomic or comorbid conditions, or other medical, social, or psychological conditions that, in the investigator's opinion, could limit the subject's ability to participate in the clinical investigation or to comply with follow-up requirements, or impact the scientific soundness of the clinical investigation results.