Impact of mitral regurgitation on reverse remodeling and outcome in patients undergoing cardiac resynchronization therapy.

BACKGROUND Mitral regurgitation (MR) is associated with reduced survival in patients with chronic heart failure, but may be improved with cardiac resynchronization therapy (CRT). We sought to evaluate the relationship between serial measurements of functional MR and reverse remodeling and outcomes in patients undergoing CRT. METHODS AND RESULTS A total of 266 consecutive patients undergoing CRT with available baseline echocardiograms and subsequent clinical and echocardiographic follow-up were included in the analysis. Long-term follow-up included all-cause mortality, heart transplantation, and implantation of a left ventricular (LV) assist device. Temporal changes in MR severity and LV end-systolic volume index (LVESVi) were evaluated by linear mixed-model analysis. CRT led to an immediate sustained decrease in MR (P<0.0001), with no significant subsequent change. The amount of MR decrease correlated with a greater decrease in LVESVi late (P≤0.0001), but not early (P=0.14), after CRT began. Patients with severe MR before CRT experienced a larger LVESVi decrease (P=0.005). Although baseline MR severity was not associated with adverse events (P=0.13), a larger MR decrease (P=0.001) and a smaller residual MR after the initial 6 months of CRT (P=0.03) were predictive of better outcome in a multivariable model. CONCLUSIONS Early reversal of functional MR was associated with reverse cardiac remodeling and improved outcomes. Patients with moderately severe to severe MR before CRT experienced relatively more reverse remodeling than patients with lesser degrees of MR.