BACKGROUND: Functional mitral regurgitation (FMR) is associated with reduced survival in dilated cardiomyopathy (DCM). Cardiac resynchronization therapy (CRT) can improve FMR. We sought to identify the predictors of FMR improvement after CRT in DCM. METHODS: From January 2003 to December 2013, 430 DCM patients consecutively enrolled were retrospectively analyzed. Inclusion criteria were successful CRT implantation in the presence of conventional indications (i.e., left bundle branch block, left ventricular ejection fraction ≤35%, New York Heart Association functional class ≥II) and moderate-to-severe FMR at the time of procedure. Early echocardiographic evaluation after CRT implantation (median 2.5 days) has been performed in each patient. Improvement in FMR (absent/mild) at midterm (7 months; interquartile range 4-10) was considered as the primary study end point. RESULTS: A total of 44 patients (10% of the overall cohort) were included. A significant reduction in FMR severity was observed in 21 patients (48%) at midterm after CRT (median time 7 months). No preimplantation variables predicted FMR evolution, but FMR improvement at midterm was strongly predicted by an acute favorable hemodynamic response (persistence/development of normal right ventricular function and 10-mm Hg decrease or normalization [≤35 mm Hg] of systolic pulmonary artery pressure) at postimplantation echocardiography (odds ratio: 13.7; 95% confidence interval: 1.27-42.8; P = 0.016). FMR improvement at midterm was stable during follow-up and was associated with superior long-term transplant-free survival (P = 0.022). CONCLUSIONS: Stable FMR improvement frequently occurs after CRT implantation in DCM and is associated with improved transplant-free survival. Echocardiographic evaluation of acute hemodynamic response to CRT is helpful to early identification of the favorable FMR evolution