Time-dependent activation and repolarization changes following left bundle branch area pacing versus conventional biventricular pacing in patients with dyssynchronous heart failure
Authors: Smits K C , Bressi E , Rijks J H J , Stipdonk A M W , Hermans B J M , Grieco D , Luermans J G L M , Vernooy K , Prinzen F W , Nguyen U C 
Published: May 2024

Abstract

Background
Cardiac Resynchronization Therapy (CRT) is the standard treatment for patients with dyssynchronous heart failure. Despite the effectiveness of conventional biventricular pacing (BiVP), 6-16% of patients develop ventricular tachyarrhythmias (VTAs) within a year of implantation. The relationship between BiVP and the development of VTAs is still under debate. During BiVP, the left-sided epicardium-to-endocardium activation creates a non-physiological activation and hence a non-physiological repolarization, which might trigger VTAs. A novel alternative treatment option to BiVP that on the contrary induces a left ventricular endocardium-to-epicardium activation, is left bundle branch area pacing (LBBAP). We hypothesized that LBBAP leads to a more homogenous repolarization than conventional BiVP.

Purpose
To compare time-dependent activation and repolarization changes in patients with dyssynchronous heart failure receiving LBBAP versus BiVP.

Methods
Patients eligible for CRT who underwent LBBAP (n=21) or BiVP (n=94) were retrospectively included. Standard 12-lead electrocardiograms obtained prior to implantation [baseline], shortly following implantation (0-2 days, [acute phase]), and after prolonged pacing during follow-up (31-180 days, [chronic phase]) were analyzed. QRS duration and QRS area were calculated through reconstruction of the vectorcardiogram and further analyzed together with corrected QT (QTc) and corrected Tpeak-Tend (Tp-e,c) intervals using a semi-automatic approach in MATLAB. Differences between LBBAP and BiVP patients were determined using the Mann-Whitney U-test. Time-dependent changes within groups were determined using the Wilcoxon signed-rank tests. Significance was defined as a p-value ≤0.05.

Results
(see figure): Compared to baseline, QRS duration and QRS area decreased significantly during the acute phase (both p &lt; 0.01) and stabilized during chronic pacing for both BiVP and LBBAP patients. Differences in QRS duration or QRS area between LBBAP and BiVP were not significant at any of the time points. In the acute phase, BiVP resulted in a temporary and significant prolongation of both QTc and Tp-e,c compared to baseline (both p &lt; 0.01). However, there was a subsequent shortening observed between the acute and chronic phases for both QTc and Tp-e,c (both p &lt; 0.01). Compared to baseline, LBBAP acutely shortened Tp-e,c (p = 0.02) and tended to shorten QTc. During chronic pacing, LBBAP shortened QTc and Tp-e,c compared to baseline (p = 0.01 and p &lt; 0.01). The decreases in QTc and Tp-e,c were larger in LBBAP than in BiVP patients in the acute and chronic pacing phase (all p &lt;0.01).

Conclusion
CRT induces activation changes in both BiVP and LBBAP patients to a comparable extent. While BiVP leads to an acute increase in repolarization dispersions, LBBAP reduces markers of repolarization dispersion compared to baseline. The diminished dispersion of repolarization might contribute to an antiarrhythmic effect with LBBAP.