The aim of the study was to assess the clinical and prognostic impact of early functional mitral regurgitation (FMR) improvement on the outcome of patients with idiopathic dilated cardiomyopathy (IDC). The prevalence and prognostic role of FMR improvement, particularly at early follow-up, in patients with IDC are still unclear. From 1988 to 2009, we enrolled 470 patients with IDC with available FMR data at baseline and after 6 ± 2 months. According to the evolution of FMR, patients were classified into 3 groups: stable absent-mild FMR, early FMR improvement (downgrading from moderate-severe to absent-mild), and persistence/early development of moderate-severe FMR. At baseline, 177 of 470 patients (38%) had moderate-severe FMR. Patients with early FMR improvement had significantly better survival rate-free from heart transplant with respect to those with persistence/early development of moderate-severe FMR (93%, 81%, and 66% vs 91%, 64%, and 52% at 1, 6, and 12 years, respectively; p = 0.044). At 6-month follow-up multivariate analysis, FMR improvement was associated with better prognosis (hazard ratio 0.78, 95% confidence interval [CI] 0.64 to 0.96, p = 0.02); the other independent predictors were male gender, heart failure duration, and early re-evaluation of the New York Heart Association class and left ventricle systolic function. This model provided more accurate risk stratification compared with the baseline model (Net Reclassification Index 80% at 12 months and 41% at 72 months). In conclusion, in a large cohort of patients with IDC receiving optimal medical treatment, early improvement of FMR was frequent (53%) and emerged as a favorable independent prognostic factor with an incremental short- and long-term power compared with the baseline evaluation.
