Quantification of acute reduction in mitral regurgitation following cardiac resynchronization therapy

Abstract

Background: Cardiac resynchronization therapy (CRT) is associated with delayed improvements in cardiac function in heart failure patients with left bundle branch block (LBBB) secondary to reverse remodeling. However, the mechanisms of immediate benefits from CRT pacing are not well understood. Our objective was to assess the acute effects of CRT pacing on mitral regurgitation (MR) using quantitative volumetric Doppler echocardiography. Methods: Twenty-four HF patients with LBBB, aged 66±10 yrs, with ejection fraction of 25±7% and QRS duration of 168±35 ms were studied by quantitative 2-D and Doppler echocardiography at baseline and the day after CRT biventricular pacing therapy. MR was quantified with the volumetric method and expressed as regurgitant volume and regurgitant fraction, in addition to and digital color regurgitation jet area. MR regurgitant volume was obtained by subtracting left ventricular outflow tract stroke volume from mitral inflow stroke volume, determined by their respective time velocity integrals multiplied by cross-sectional area. MR regurgitant fraction was obtained by dividing regurgitant volume by mitral inflow stroke volume. Results: Baseline group mean MR regurgitant volume was 35±24 ml, MR regurgitant fraction was 35±17% and MR jet area was 6.9±4.9 cm2. After only 23±10 hours of CRT, significant improvements in MR occurred with regurgitant volume decreasing to 20±19 ml∗ and MR regurgitant fraction decreasing to 21±16%∗, (∗p<0.01 vs. baseline) (figure). MR jet area also decreased to 5.0±5.1 cm2 (p<0.05 vs. baseline). Acute reductions in MR were accompanied by a significant improvement in cardiac index from 2.1±0.5 to 2.4±0.6∗ L/min/m2 (∗p<0.05 vs. baseline). Conclusion: CRT resulted in acute significant reductions in MR and increases in cardiac index. These data support MR reduction as an important acute beneficial effect of CRT in HF patients with LBBB.