The investigators' hypothesis is that CMR tissue characterization and myocardial function analysis acquired by CMR feature tracking technique predict reverse remodeling in patients with severe secondary mitral regurgitation (MR) undergoing transcatheter mitral edge-to-edge repair.

Diametrically opposed results of the COAPT- and the MITRA-FR trial have demonstrated the need for additional evidence in the field of transcatheter mitral edge-to-edge repair. Reverse left ventricular remodeling after treatment of severe secondary mitral regurgitation can indicate treatment response and is associated with positive outcomes.

However, so far it is reverse remodeling, respectively treatment response is difficult to predict, which complicates patient selection for mitral edge-to-edge repair. Previous studies have shown, that focal (late gadolinium enhancement (LGE)) but not diffuse myocardial fibrosis (T1 mapping and extracellular volume fraction (ECV)) burden quantification using CMR predicts reverse left ventricular remodeling following cardiac resynchronization therapy in patients with heart failure with reduced ejection fraction (HFrEF). On the other hand, myocardial T1 mapping was predictive for beneficial left ventricular remodeling after long-term heart failure therapy. Furthermore, in patients with HFrEF, LGE is associated with clinical outcome and an incremental predictive value to left ventricular dimensions and function. However, as only 1/3 of HFrEF patients show LGE, subtle fibrosis might be missed. Recently the investigators have shown that different novel fibrosis detection techniques (naive T1 mapping, mean ECV and λGd being the delta of pre- and post T1 mapping and ECV calculation) all demonstrated strong association with outcome in patients with heart failure.

The investigators' hypothesis is that these markers (CMR tissue characterization and myocardial function analysis acquired by a CMR feature tracking) might also be helpful in predicting reverse remodeling after transcatheter mitral edge-to-edge repair. This project might help to understand the pathophysiology of the disease in patients with secondary mitral regurgitation, improve risk stratification in this clinical setting, and optimize selection of patients who benefit from transcatheter mitral edge-to-edge repair.

Inclusion Criteria:

• Patients with severe secondary MR characterized, according to the European guidelines and recommendations, by a regurgitant volume ≥30 mL/beat or an effective regurgitant orifice ≥20 mm².
• Symptomatic patients with New York Heart Association Class ≥II.
• Left ventricular ejection fraction between 15% and 50%.
• Optimal standard of care therapy for heart failure according to investigator.
• Not eligible for a mitral surgery intervention according to the Heart Team.
• Patients who have the ability to understand the requirements of the study and provide written consent/assent to participate and agree to abide by the study requirements.

Exclusion Criteria:

• Participants younger than 18 years
• Pregnancy or breastfeeding
• Severe impaired renal function (GFR < 15 ml/min)
• Patients with untreated severe concomitant valve disease (e.g. severe tricuspid valve regurgitation, aortic stenosis)
• The patient has a medical condition, serious concurrent illness, or extenuating circumstance that would significantly decrease study compliance, including all prescribed follow-up
• The patient has contraindications to CMR, including: Implanted non-CMR conditional metallic implants, pacemaker, intracardiac defibrillator, neurostimulator, epicardial pacemaker leads, or any abandoned leads, ferromagnetic aneurysm clip, ferromagnetic halo device, cochlear implants, implanted infusion pumps or severe claustrophobia
• The patient is clinically unstable or has stage D congestive heart failure or inability to lay flat for 60 minutes