This study is a prospective, single-arm, multi-center feasibility clinical study of the Tendyne Mitral Valve System for the treatment of eligible subjects with symptomatic, severe mitral regurgitation and severe mitral annular calcification (MAC). Subjects satisfying the study inclusion/exclusion criteria will undergo a procedure to implant the Tendyne mitral valve replacement device.

Inclusion criteria:

1. Heart Team determines subject is not a suitable candidate for conventional surgical treatment due to degree of MAC present and the subject will likely benefit from transcatheter valve implantation
2. Symptomatic, severe mitral regurgitation, as defined in the 2017 ACC expert Consensus Decision Pathway on the Management of MR
3. NYHA Functional Classification ≥ II (if Class IV, patient must be ambulatory)
4. Age 18 years or older at time of consent
5. Not a member of a vulnerable population per the investigator's judgment
6. The subject or the subject's legal representative has been informed of the nature of the study and agrees to its provisions, including complying with study required testing and follow-up visits, and has provided written informed consent

Exclusion criteria:

1. Presence of Left Ventricle or Left Atrium thrombus
2. Chest condition that prevents transapical access
3. Left Ventricular Ejection Fraction (LVEF) less than 25% assessed by echocardiogram
4. Left Ventricular End Diastolic Dimension (LVEDD) > 7.0 cm
5. Severe mitral stenosis not amenable to balloon valvuloplasty or transcatheter therapy
6. Prior intervention with permanently implanted mitral device (e.g. MitraClip)
7. Mitral pathoanatomy and Left Ventricular Outflow tract (LVOT) anatomy deemed not suitable for Tendyne mitral valve implantation
8. Any planned cardiac surgery or intervention that is 30 days prior and 30 days post that is not concomitant with the Tendyne procedure
9. Cardiac resynchronization therapy (CRT) device or implantable pulse generator (IPG) implanted within three months of planned implant procedure
10. Myocardial Infarction (MI) within 30 days of the planned implant procedure
11. Symptomatic, or ischemia-associated coronary artery disease (e.g., active ischemia) amenable to revascularization and thus requiring stenting or CABG
12. Cerebrovascular accident (CVA) within six months of planned implant procedure
13. Unresolved severe symptomatic carotid stenosis (> 70% by ultrasound)
14. Cardiogenic shock or hemodynamic instability requiring inotropes or mechanical support devices within 1 month prior to planned implant procedure
15. Severe tricuspid regurgitation or severe right ventricular dysfunction
16. Hypertrophic or restrictive cardiomyopathy, constrictive pericarditis or any other structural heart disease causing heart failure other than dilated cardiomyopathy of either ischemic or non-ischemic etiology
17. Any of the following: leukopenia, acute anemia, thrombocytopenia, history of bleeding diathesis, or coagulopathy if cannot be adequately treated
18. History of endocarditis within 6 months of planned implant procedure
19. Active systemic infection requiring antibiotic therapy
20. Known hypersensitivity or contraindication to procedural or post-procedural medications (e.g., contrast solution, anti-coagulation therapy) which cannot be adequately managed medically
21. Subject unable or unwilling to take anticoagulation with warfarin for a minimum of 6 months following Tendyne valve implantation
22. Known hypersensitivity to nickel or titanium
23. Subject is undergoing hemodialysis due to chronic renal failure ( ≥ Stage 4 CKD)
24. Subject has pulmonary arterial hypertension (fixed PAS >70mmHg)
25. FEV1 < 50% of predicted or < 1L
26. Subject refuses blood transfusions
27. Subject has COPD requiring continuous home oxygen therapy or chronic outpatient oral steroid use
28. Pregnant, lactating, or planning pregnancy within next 12 months.
29. Currently participating in an investigational drug or another device trial that has not reached its primary endpoint
30. Subjects with non-cardiac co-morbidities that are likely to result in a life expectancy of less than 12 months