Different Determinants of Improvement of Early and Late Systolic Mitral Regurgitation Contributed after Cardiac Resynchronization Therapy

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.

Keywords: Mitral regurgitation, Early systolic, Late systolic, Cardiac resynchronization therapy

Abbreviations: APM, Anterolateral papillary muscle, CRT, Cardiac resynchronization therapy, LV, Left ventricular, LVESV, Left ventricular end-systolic volume, MR, Mitral regurgitation, PPM, Posteromedial papillary muscle, Ts, Time to peak systolic velocity during the ejection phase, Ts-Dif, Maximal difference of time to peak systolic velocity during the ejection phase among 12 left ventricular segments