Is left bundle branch block pattern on the ECG caused by variable ventricular activation sequence?

Lucie Riedlbauchová; Theodor Adla; Vojtěch Suchánek; Miroslav Ložek; Jan Tomis; Jiří Hozman; Viktor Tomek; Josef Veselka; Jan Janoušek

doi:10.1111/pace.13914

Is left bundle branch block pattern on the ECG caused by variable ventricular activation sequence?

Pacing Clin Electrophysiol. 2020 May;43(5):486-494. doi: 10.1111/pace.13914. Epub 2020 Apr 28.

Authors

Lucie Riedlbauchová¹, Theodor Adla², Vojtěch Suchánek¹, Miroslav Ložek³, Jan Tomis¹, Jiří Hozman⁴, Viktor Tomek³, Josef Veselka¹, Jan Janoušek³

Affiliations

¹ Department of Cardiology, Motol University Hospital and 2nd Faculty of Medicine, Charles University, Prague, Czech Republic.
² Department of Radiology, Motol University Hospital and 2nd Faculty of Medicine, Charles University, Prague, Czech Republic.
³ Children's Heart Centre, Motol University Hospital, 1st and 2nd Faculty of Medicine, Charles University, Prague, Czech Republic.
⁴ Department of Biomedical Technology, Faculty of Biomedical Engineering, Czech Technical University in Prague, Czech Republic.

PMID: 32270513
DOI: 10.1111/pace.13914

Abstract

Background: The presence and extent of ventricular dyssynchrony are currently assessed from the QRS complex morphology and width. However, similar electrocardiography (ECG) pattern may be caused by variable ventricular activation sequence. This may then contribute to interindividually different response to cardiac resynchronization therapy (CRT).

Methods: Electroanatomical mapping and magnetic resonance imaging scan were performed in 11 patients with left bundle branch block (LBBB, QRS 170 ± 14 ms) and heart failure of ischemic (coronary artery disease (CAD), n = 2) and nonischemic (dilated cardiomyopathy (DCM), n = 9) etiology. Ventricular activation sequence was studied during LBBB and final CRT programming. Presence and extent of scarring were analyzed in the 17-segment left-ventricular (LV) model.

Results: Regardless of etiology, presence of typical LBBB was associated with diffuse prolongation of impulse conduction with right-to-left activation sequence. Basal lateral wall was constant site of late activation. This activation pattern was present in "true LBBB," but also in LBBB-like pattern (persistent S wave in V5-6) and left axis deviation. Activation started in right vetricular (RV) apex in patients with left axis deviation at RV free wall in normal axis. Individuals with CAD and DCM patient displayed focal scar. Despite that they exhibited typical LBBB and activation sequence mirrored findings in other LBBB individuals. Reverse remodeling (∆LVESV > 15% after 6 months) was evident in 10 patients.

Conclusions: Both typical LBBB and LBBB-like pattern might be associated with constant activation sequence regardless of etiology and scar localization. Activation initiation in RV apex, not LV activation sequence can be surrogate for left axis deviation. CRT caused inter- and intraventricular LV resynchronization without significantly changed RV activation sequence and duration.

Keywords: ECG; biventricular pacing; electroanatomical mapping; left bundle branch block; resynchronization therapy.

MeSH terms

Aged
Bundle-Branch Block / diagnostic imaging
Bundle-Branch Block / physiopathology*
Bundle-Branch Block / therapy
Cardiac Resynchronization Therapy / methods
Electrocardiography*
Epicardial Mapping
Female
Heart Failure / diagnostic imaging
Heart Failure / physiopathology*
Heart Failure / therapy
Heart Ventricles / diagnostic imaging
Heart Ventricles / physiopathology*
Humans
Magnetic Resonance Imaging
Male
Middle Aged