To evaluate safety and feasibility of Mitral Loop Cerclage(MLC) Annuloplasty with CSTV for repair of functional mitral regurgitation.

The objective of this prospective, single-center, open label, feasibility test is to assess the safety and efficacy of Mitral Loop Cerclage Annuloplasty with CSTV protective device in treating functional mitral regurgitation (FMR) associated with heart failure.

Inclusion Criteria:

• NYHA(New York Heart Association) Class III - IV, and symptomatic severe functional MR by 2014 ACC/AHA guideline in spite of optimal medical treatment.

(For optimal medical treatments, ①ACE inhibitor or angiotensin receptor blocker ②β-blocker ③ aldosterone antagonists should be given for at least 3 months unless the subject has contraindication for each drug)

Exclusion Criteria:

• Primary Mitral Regurgitation
• LV ejection fraction lower than 25%
• Creatinine ≥2.0 mg/dL
• Anomaly of Coronary Sinus
• Pre-existing devices in coronary sinus such as Implantable Cardioverter Defibrillator and Pacemaker
• 2:1 Atriventricular AV block or higher AV block and ventricular tachycardia
• Subjects with functional MR who need CABG or AVR performed
• Subjects who have functional MR caused by aortic valve disease
• Subjects who have uncontrollable hyperthyroidism
• Subjects who have severe TR due to primary valve leaflet disease
• Subjects who cannot be screened by cardiac CT
• Subjects who have possibility of coronary artery pinching even with Mitral Loop Cerclage system judged by cardiac CT
• Subjects who are unable to take anti-platelet agents
• Subjects who are participated in other clinical trials within 1 month of enrollment
• Subjects who have coagulation disorders
• Subjects who have thrombosis and embolism
• Subjects who are pregnant, or lactating, or plan pregnancy during the clinical trials
• Subjects who are deemed not to be eligible in this study by physician's discretion