Left bundle branch block is associated with a similar Dyssynchronous phenotype in heart failure patients with Normal and reduced ejection fractions

BACKGROUND: Few therapies improve outcomes in patients with heart failure with preserved ejection fraction (HFpEF). If left bundle branch block (LBBB) is associated with left ventricular dyssynchrony and impaired cardiac performance in HFpEF, cardiac resynchronization therapy(CRT) could be a promising treatment.

METHODS: We performed a cross sectional analysis of selected patients with HFpEF (ejection fraction ≥50%) with and without LBBB (normal conduction, NC) and patients with HFrEF and LBBB who were suitable CRT candidates to describe and contextualize the mechanical phenotype of LBBB in HFpEF. Systolic and diastolic isovolumic times, ejection time(ET), and diastolic filling time(DFT) were measured on spectral tissue Doppler echocardiographic images and indexed to the heart rate. Dyssynchrony pattern was assessed using speckle tracked longitudinal strain patterns. Comparisons were performed using ANOVA and χ2 test with post-hoc pairwise comparisons as indicated.

RESULTS: Eighty-two HFpEF (50 with NC, 32 with LBBB) and 149 HFrEF (all with LBBB) patients met criteria. Overall, 84.4% with HFpEF/LBBB and 91.3% with HFrEF/LBBB had demonstrable mechanical dyssynchrony, compared to 0% with HFpEF/NC. Compared to HFpEF/NC, HFpEF/LBBB had significantly prolonged isovolumetric contraction time (ICT), isovolumetric relaxation time (IRT), and total isovolumetric time and significantly shorter ET (all indexed). LBBB/HFrEF patients, compared to LBBB/HFpEF patients, had increased ICT and IRT, with decreased DFT but similar ET.

CONCLUSIONS: Patients with HFpEF and LBBB frequently have a LBBB dyssynchrony phenotype, prolonged ICT and IRT, and reduced ET compared to HFpEF patients with NC. The electromechanical dyssynchrony and disordered cardiac timing of HFpEF with LBBB is similar to HFrEF with LBBB.