Safety and Performance Study of the MitralStitch Repair System.

Inclusion Criteria: 1. Age ≥18 yrs 2. Moderate to severe (3+) or severe (4+) mitral valve regurgitation confirmed by echocardiography (defined as MR \>2+); 3. NYHA functional class II-V (Appendix 3); 4. Anatomically suitable for mitral valve repair; 5. 40mm ≤LVESD≤55 mm; 25% ≤LVEF ≤60%; tolerable for small incision thoracic surgery; 6. Mitral valve diameter ≤45mm; 7. The independent expert committee of this study determined that surgical operation was contraindicated or high-risk, and the recommended reference standard was: surgical valve replacement with STS score ≥ 8； or surgical valve repair with STS score ≥ 6； or other risk factors (e.g., There are at least two moderate to severe indicators of weakness; potential operational disorders; at least major organ dysfunction that cannot be improved after surgery, etc.) 8. The subject or the subject's legal representative fully understand and agree to join to the clinic trial. Exclusion Criteria: 1. Echocardiographic evidence of intracardiac mass, thrombus or vegetation; 2. Severe mitral valve calcification; 3. Concomitant with greater than moderate aortic stenosis or regurgitation; 4. Mitral regurgitation caused by special pathological mechanisms, such as leaflet perforation and leaflet fissure; 5. Severe untreated coronary artery stenosis requiring revascularization; or with other cardiovascular disease requiring surgical treatment; 6. Hypertrophic cardiomyopathy with or without obstruction, restrictive cardiomyopathy, constrictive pericarditis, or other structural heart diseases that cause heart failure in patients expect dilated cardiomyopathy; 7. Myocardial infarction was performed within 4 weeks before the intervention; 8. Any vascular intervention, cardiac surgery, cardiac resynchronization therapy (CRT, CRT-D), and an implantation of implantable cardioverter defibrillator (ICD) were performed within 30 days before the intervention; 9. Any heart transplantation, mitral valve surgery or percutaneous mitral valve operation were performed before the intervention; 10. Life expectancy is less than 12 months; 11. History of, or active, rheumatic heart disease; 12. Active phase of bacterial endocarditis; 13. The active infections require concurrent antibiotic treatment; 14. History of acute peptic ulcer or upper gastrointestinal bleeding within 3 months; 15. Dysplasia of the blood system, including granulocytopenia (WBC \< 3×109/L), acute anemia (HB \< 90g/L), thrombocytopenia (PLT \< 50×109/L), hemorrhagic constitution, and coagulopathy； 16. Modified Rankin scale ≥4； 17. Pregnant or lactating women; 18. The subject is suffered from a disease which may cause difficulty in evaluating the treatment (e.g., cancer, infection, severe metabolic disease, psychosis, etc.); or special cases were evaluated by the local experimental center heart team as not suitable for the surgical application of this clinical trial instrument; 19. Participants who have participated in clinical trials of any drug and/or medical device within 1 month before this study; 20. In the judgment of the Investigator, patients were not compliant enough to complete the study as required.