Mi-thos® Transcatheter Mitral Valve Replacement Study

Inclusion Criteria: * Severe mitral valve regurgitation ≥ 3+; * High surgical risk fot open mitral valve surgery; * Age ≥ 65 years old; * Life expectancy \> 12 months; * As assessed by multidisciplinary cardiac team, patients who are not eligible for surgery; * 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; * Patients with severe thoracic deformities.