The purpose of this study is the evaluation of cardiac and pulmonary response to cardiopulmonary exercise in severe mitral regurgitation and its variation under treatment (surgical mitral valve repair, percutaneous mitral valve repair, optimal medical treatment). The study is conducted as a prospective, observational, single-center study. Patients suffering from symptomatic severe mitral regurgitation will be eligible, if they are referred to the University Hospital of Regensburg, Germany, for further diagnostic procedures and heart team discussion. Cardiopulmonary exercise testing is performed comprising standardized stress echocardiography as well as ergospirometry. Additional detailed assessment will be conducted including standardized questionary, clinical examination, transesophageal echocardiography and measurement of biomarkers.

Inclusion Criteria:

• symptomatic, severe mitral regurgitation
• referral for diagnostic work-up and heart team discussion
• declaration of informed consent

Exclusion Criteria:

• contra-indication for cardiopulmonary stress examination (unstable angina pectoris, left main disease, abnormal electrolyte concentrations, acute decompensation)
• pregnancy
• exercise test on treadmill not possible (amputation of lower extremity, severe arthritis of lower extremities)
• no acceptable acoustic window at rest

Symptomatic, severe mitral regurgitation. Aetiology and treatment of mitral regurgitation do not affect enrollment.