Impact of Left Bundle Branch Block on Left Ventricular Mechanics in Patients with Idiopathic Dilated Cardiomyopathy

Ahmed Emara,Magdi H Yacoub,Naglaa Fahim,Hala Mahfouz Badran,Waleed Abdou,Mohamed Fathi

doi:10.4236/wjcd.2019.92013

Abstract

Objectives: Left bundle branch block (LBBB) is commonly associated with heart failure. We evaluated the prevalence and impact of LBBB on left ventricular mechanics using 2D strain imaging in patients with idiopathic dilated cardiomyopathy (IDCM). Methods: We included 101 patients with IDCM with mean age 38 ± 18 years: 74% were males and 13.9% of them were in NYHA Class III-IV. LBBB was present in 26 (37%) of included patients. Myocardial mechanics including longitudinal, circumferential strain and rotation and LV synchronization were assessed using two-dimensional strain imaging. Results: LBBB group had higher LV volumes, and PAP compared with non LBBB. Peak LV longitudinal systolic strain (esys) of the septum and global LV SRsys were significantly lower in LBBB compared to non LBBB group (P < 0.01, <0.03). TTP-d was greater in LBBB in comparison to non LBBB group (274.5 ± 116 versus 209.4 ± 139, P < 0.02). The electromechanical delay between septal segments was 35 ± 18 ms and between lateral wall segments: 48 ± 24 ms, between anterior wall segments: 21 ± 11 and between inferior wall segments: 41 ± 12. Consequently, LV mechanical dyssynchrony was more evident in IDCM patients with LBBB. QRS width was correlated inversely with LV longitudinal strain and strain rate and electromechanical delay (P < 0.0001) in non LBBB group. In LBBB QRS width was not related to cardiac mechanics. Using univariate analysis and after a multiple covariate adjustment, the baseline LBBB was associated with a significantly increased LV dysfunction. Conclusion:After correcting for potential confounders, LBBB was found to be associated with more deterioration of LV mechanics and exaggerated LV dyssynchrony in patients with IDCM.

Highlights

Idiopathic dilated cardiomyopathy (IDCM) is a diagnosis that continues to puzzle many cardiovascular specialists
We evaluated the prevalence and impact of Left bundle branch block (LBBB) on left ventricular mechanics using 2D strain imaging in patients with idiopathic dilated cardiomyopathy (IDCM)
We included 101 patients with IDCM with mean age 38 ± 18 years: 74% were males and 13.9% of them were in New York Heart Association (NYHA) Class III-IV

Summary

Introduction

Idiopathic dilated cardiomyopathy (IDCM) is a diagnosis that continues to puzzle many cardiovascular specialists. A number of Left bundle branch block (LBBB) occurs frequently in patients with dilated cardiomyopathy (DCM) and is associated with high cardiac morbidity and mortality. The characteristic feature of LBBB is an asynchronous septal wall motion and most frequently a delay of the lateral and/or posterior wall segments [1]; this heterogeneous activation of the ventricle leads to inefficient contraction. It is generally assumed that LBBB occurs secondarily to the underlying disease process of DCM; the possibility exists that in some patients the LBBB-induced abnormal left ventricular (LV) contraction pattern could—over long term—induce DCM [3]. There is extensive research underway in patients with DCM and LBBB to evaluate the short and long-term effects of normalization of ventricular activation sequence with high septal, LV, or biventricular pacing [4]

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