Determinants and Clinical Outcomes of Functional Mitral Regurgitation Improvement Following Cardiac Resynchronization Therapy

Functional Mitral Regurgitation (FMR) is associated with poor prognosis in patients with Heart Failure (HF) and reduced Left Ventricular Ejection Fraction (LVEF). Cardiac Resynchronization Therapy (CRT) has been shown to lead to long-term and accurate improvement in FMR.

This study aims to identify the determinants of FMR improvement after CRT and determine their impacts on clinical outcomes.

In this retrospective single-centered study of consecutive CRT implantations, echocardiographic evaluation was performed before CRT implantation and at 6-12-month follow-up. FMR improvement was defined as ≥ 1 grade reduction in MR class. Independent predictors of FMR improvement were determined by multivariate analysis. The composite outcome of HF hospitalization and mortality was used to determine the prognosis.

This study was conducted on 192 patients with a median follow-up of 50 ± 35 months. At baseline, FMR was present in 85% of the participants (48% mild, 30% moderate, and 7% severe). Improvement after CRT was observed in 74% of the patients with significant FMR. The variables associated with CRT improvement were atrial fibrillation, diabetes, and wider QRS, septal right ventricular lead, and posterolateral left ventricular lead. After multivariate analysis, only QRS duration was an independent predictor of FMR improvement (OR: 1.08, 95% CI: 1.00 - 1.17, P = 0.041). ‘Improvers’ had a higher survival-rate free of composite outcome at follow-up (74% vs. 33%, P = 0.015). Yet, the clinical benefit of FMR improvement was independent from CRT responsiveness (p-interaction = 0.338).

FMR was prevalent in patients undergoing CRT implantation, and three-fourths of the patients experienced a reduction in regurgitation severity. The only independent predictor of FMR improvement was QRS duration. Moreover, improvement was associated with better prognosis, independently from CRT responsiveness.