Predictors of functional mitral regurgitation improvement in a short-term observation after cardiac resynchronization therapy

Abstract

Background: There is little knowledge on predictors of the functional mitral regurgitation (FMR) improvement (FMRI) after CRT implantation in a short-term observation. The role of preserved contractile reserve (CR) in prediction of FMRI is unclear. The study was undertaken to define predictors of FMRI and the impact of FMRI on the reversed remodelling (RR). Methods: This study is subanalysis of the multicenter Myocardial Viability in Cardiac Resynchronization Therapy (VIACRT) trial. Among 90 pts. with ischemic and nonischemic left ventricle dysfunction undergoing CRT therapy, in whom Doppler Echocardiography was performed one day before and 6 weeks after CRT implantation, 66 pts with at least moderate FMR [(grade 2+); mean age 64±10, mean ejection fraction LVEF 25,7%±6, ischemic etiology 48%] were included. The severity of FMR was estimated semiquantitavely from colour-flow Doppler images on a four –point scale. The FMRI was defined as the reduction of the severity for at least one grade. The pts were divided into: gr. A with FMRI (n = 30) and gr. B without FMRI (n=36). Baseline dyssynchrony was defined by TDI. Low-dose dobutamine stress echo (LDSE) was performed before CRT implantation. CR was defined as changes in LVEF > 20% and improvement of segmental contractility. The RR was defined as the reduction of the LV endsystolic volume LVESV >15%. Results: There were no differences concerning the age, gender, etiology (ischemic vs nonischemic), NYHA class and QRS width between both groups. No differences related to ejection fraction, dyssynchrony parameters and site of the latest activation were shown. Multivariate logistic regression analysis revealed the following predictive factors for FMRI: the presence of CR (improved contractility in >3 segments) with an OR = 5.7 (95% CI 1.81-17.97), p=0.005 with sensitivity 65.5% and specificity 72.2%; (AUC = 0.727) and baseline LV diastolic diameter LVDD ≤ 74 mm with an OR = 2.09 , (95% CI 0.75-5.78), p<0.05 , with sensitivity 80.0% and specificity 47.2% (AUC = 0.632). The FMRI was associated with significantly higher reduction of LVESV; gr. A: -38±27 mL vs -12±36 mL in gr. B, p=0.002 and higher increase in LVEF; in gr. A: +10.1±8.5% vs +2.3±5.5% in gr. B p<0.001 respectively. The higher rate of RR in gr. A comparing to gr. B (62.8% vs 37.2%, p<0.001) was noted. Conclusion: Preserved contractile reserve and lesser degree of LV dilation emerged as predictive factors of short-term FMRI after CRT implantation. FMRI is associated with higher rate of response to CRT in term of reverse remodelling.