Project Summary Functional mitral regurgitation (FMR) portends a bleak prognosis and is a common consequence of ischemic and non-ischemic cardiomyopathy (ICM, NICM), where adverse annular and left ventricular (LV) remodeling and/or infarction alters mitral valve (MV) function. Prior studies demonstrate significant increases in mortality risk as severity of FMR increases; mortality rates range from 15-40% at 1 year. Furthermore, as the prevalence of heart failure (HF) is rising, FMR is projected to double from over 2 million patients in 2000 to over 4 million patients in the United States by 2030. Defining FMR severity, optimal timing of intervention, and most appropriate method for intervention remain controversial. Recently, MITRA-FR and COAPT trials demonstrated contrasting survival benefit with percutaneous MV repair, demonstrating the importance and need for more optimal selection criteria. Currently, the patient selection criteria for Mitraclip therapy are solely based on MV anatomy and controversial echocardiographic criteria for FMR severity. Cardiac magnetic resonance (CMR) provides an exciting opportunity to address numerous unmet needs regarding characterizing FMR and the need for more optimal selection criteria for improving outcomes. Superior accuracy and reproducibility for quantification of LV size and function, and gold standard tissue characterization, positions CMR as the ideal imaging modality for comprehensively characterizing FMR and the underlying myopathic processes that significantly impact response to FMR therapies. The goal of the current research is to develop personalized risk prediction for FMR patients through explainable unsupervised phenomapping enriched with advanced CMR imaging biomarkers, and to determine the CMR predictors of reverse remodeling following modern therapies for FMR.