Patients and methods: The prospective cohort study is designed to enrol 200 patients with severe mitral regurgitation and followed over a 4-year period. Natriuretic peptides including BNP and NT-proBNP will be measured in addition to detailed clinical, electrocardiographic, and echocardiographic assessment prospectively and repetitively in patients with severe mitral regurgitation during routine consultations at 6 months intervals. Our primary analysis (longitudinal study) will focus on the prognosis in asymptomatic patients. In addition, a sub-study will also include symptomatic patients with severe mitral regurgitation whether or not they are scheduled to undergo valvular surgery (cross sectional study) in order to obtain more reliable data regarding BNP/NT-proBNP levels in patients with a formal indication for valvular surgery. The treating physician will remain blinded to the BNP/NT-proBNP values. In this cohort study, we will try to identify a BNP/NT-proBNP cut-off values that predict major adverse cardiac events including cardiac death, congestive heart failure, myocardial infarction, or persistent left ventricular systolic dysfunction at 6 months after valvular surgery.