Background: Functional mitral regurgitation (MR) at different phases of the regurgitant period may respond differently to cardiac resynchronization therapy (CRT). The aims of this study were to examine the impact of CRT on the phasic changes of MR (early vs late systole) and to explore the mechanisms of such changes.
Methods: Instantaneous MR flow rate and total MR volume were evaluated in 60 patients who had more than mild functional MR before and 3 months after CRT. In addition, indices of global left ventricular (LV) remodeling, mitral deformation, and LV systolic dyssynchrony were assessed.
Results: CRT diminished MR volume (38 ± 18 vs 32 ± 20 mL) by reducing both the early (72 ± 47 vs 58 ± 48 mL/sec) and late (48 ± 42 vs 40 ± 42 mL/sec) systolic components (all p values < .01). In patients with ≥10% reductions in total MR volume but not in patients without this improvement, there were significant reductions in LV end-systolic volume, increases in LV +dP/dt, decreases in mitral valvular tenting, and improvements of systolic dyssynchrony at 3 months (all P values < .05). By multivariate regression, the reductions in LV end-systolic volume and tenting area were independent determinants of a reduction in total MR volume: the reductions in LV end-systolic volume and global dyssynchrony determined the reduction in early systolic MR, and the reductions in tenting area and global dyssynchrony determined reduction in late systolic MR.
Conclusions: CRT decreases MR volume by reducing both early and late systolic MR. The determinants of the phasic improvement in functional MR are different.
Copyright © 2010 American Society of Echocardiography. Published by Mosby, Inc. All rights reserved.