To evaluate the effectiveness and safety of the Mi-thos® Transcatheter Mitral Valve Replacement System in the treatment of patients with moderate or greater mitral regurgitation who are at high risk for conventional surgery, or who are not candidates for conventional surgery.

The Mi-thos® study is a single-arm, prospective, safety and performance clinical study.

Inclusion Criteria:

• Severe mitral regurgitation ≥ 3+;
• Patients with an STS score >8 or who have been evaluated by a cardiothoracic surgeon as high risk for conventional surgery or who cannot tolerate conventional open-heart surgery;
• Age ≥ 65 years old;
• Life expectancy > 12 months;
• Patients sign an informed consent form.

Exclusion Criteria:

• Previous cardiac mitral valve surgery;
• Active infections requiring antibiotic therapy;
• Clinically significant untreated Coronary Artery Disease (CAD);
• Pulmonary hypertension （Pulmonary systolic pressure > 70 mmHg）;
• Patients with severe right heart failure;
• Left ventricular ejection fraction <25%;
• Diagnosis of hypertrophic cardiomyopathy, restrictive cardiomyopathy, constrictive pericarditis;
• Dialysis patient;
• Patients with severe coagulopathy;
• Patients with contraindications to anticoagulant drugs;
• Patients with stroke or transient ischemic within 30 days;
• Echocardiography found any intracardiac mass, left ventricle or atrial thrombus;
• Patients who require surgery or interventional therapy for other valvular lesions;
• Patients with severe macrovascular disease requiring surgical treatment;
• Patients with more than 70% of carotid stenosis;
• To be allergic to contrast agents, nickel-titanium memory alloys or bovine-derived products;
• Patients with severe neurological disorders affecting cognitive ability;
• Life expectancy < 12 months;
• Patients with severe thoracic deformities.