Additionally, a SUBSTUDY (MITRA-REVERSE FIBROSIS) will explore newer CMR techniques, such as T1 mapping and extracellular volume fraction quantification, can now non-invasively quantify the extent of diffuse extracellular matrix expansion as a surrogate for interstitial fibrosis, and are supported by histological validation. The interplay between diffuse interstitial fibrosis, volume overload reduction (via decrease in mitral regurgitation), and subsequent LV reverse remodeling are not well understood. It is possible that increasing burden of diffuse interstitial fibrosis at baseline may prevent, blunt, or delay the reverse remodeling that occurs following volume overload reduction. Alternatively, volume overload reduction and reverse LV remodeling may lead to subsequent reduction in diffuse interstitial fibrosis A sub-study with gadolinium contrast administration will attempt to address these questions. MR patients without contraindications to gadolinium will be enrolled into the sub-study that includes pre- and post-gadolinium contrast imaging in order to quantifying LV myocardial replacement and interstitial fibrosis, as well as papillary muscle fibrosis. Recently, in a cohort of 48 patients with chronic MR undergoing surgical mitral valve repair, it has been demonstrated that the presence of LV myocardial fibrosis assessed with delayed-enhancement CMR was an independent predictor of increased adverse clinical outcomes. Similarly, in this sub-study it is intended to examine the correlation between the presence and extent of myocardial replacement and interstitial fibrosis to clinical response, as assessed by NYHA (New York Heart Association) class and Kansas City Cardiomyopathy Questionnaire, following a MitraClip procedure. Moreover, a new technique to quantify replacement fibrosis in the papillary muscles may be exploited in the gadolinium sub-study that could provide additional information, as the papillary muscles of the left ventricle are key components of the mitral valve apparatus. Papillary muscles connect the LV wall with the mitral leaflets and annulus, and regulate the location of the mitral leaflets. Thus, the geometry and function of papillary muscles contribute to mitral valve function and an accurate evaluation is key in understanding the pathophysiology of mitral valve disease. This evaluation of the papillary muscles will rely on a new procedure that is based on the use of a novel dark blood delayed enhancement imaging technique.