Effect of Functional Mitral Regurgitation on Outcome in Patients Receiving Cardiac Resynchronization Therapy for Heart Failure.

Functional mitral regurgitation (FMR) is common in heart failure (HF), and negatively impacts prognosis. Cardiac resynchronization therapy (CRT) can improve FMR, but the long-term changes in and impact of FMR after CRT are still unclear. The present study investigated the prevalence, evolution and impact on mortality of FMR before and after CRT in patients with HF. A total of 1,313 patients (66 ± 11 years, 77% male, 59% ischemic heart disease) treated with CRT were evaluated. Patients were divided into 4 groups of FMR according to the evolution at 6 months after CRT: no or mild FMR at baseline which remained unchanged at 6 months (grade 0-1 FMR unchanged, n = 609 [51%]), no or mild FMR which worsened to moderate to severe (grade 0-1 FMR worsened, n = 66 [6%)]), moderate to severe FMR which improved to no or mild (grade 2-4 improved, n = 209 [18%]), and moderate to severe FMR which remained unchanged (grade 2-4 unchanged, n = 309 [26%]). Over a mean follow-up of 51 ± 38 months, 297 (25%) patients died. Those with baseline FMR grade 0-1 which remained unchanged at 6-month follow-up, as well as baseline FMR grade 2-4 which improved, had lower mortality rates than patients with 6-month FMR grade 2-4 regardless of baseline FMR grade (p <0.001). Baseline FMR grade 2-4 that remained unchanged at 6-month follow-up was associated with increased mortality, independent of the clinical and left ventricular volumetric responses to CRT (hazard ratio, 1.77; 95% confidence interval, 1.41-2.22, p <0.001). In conclusion, moderate to severe FMR at baseline which remains unchanged at 6 months after CRT implantation is strongly associated with long-term mortality in patients with HF.