LEFT BUNDLE BRANCH PACING OF PROXIMAL LEFT BUNDLE BRANCH AND SEPTAL FASCICLE PRODUCES MORE PHYSIOLOGICAL ACTIVATION COMPARED TO PACING OF THE ANTERIOR FASCICLE

Background:
Left bundle branch pacing is defined as the pacing of the trunk or its proximal fascicles. It is unknown, whether a difference between captures with normal or deviated axes and proximal vs. distal locations exists.
Objective:
To study ventricular activation during nonselective LBB pacing (NSLBBp) in different QRS axes and proximal vs. distal pacing positions using ultra-high-frequency ECG (UHF-ECG).
Methods:
NSLBBp captures were classified as superior (-30°;-90°), normal (-29°;60°), or inferior (61°;120°) QRS axis and proximal LBBp (LBBpo to ventricular EGM ≥ 25 ms) vs. fascicular LBBp (LBBpo-V ˂ 25 ms and corresponding axes for anterior, septal and posterior fascicle). UHF-ECG electrical dyssynchrony parameters: e-DYS (difference between the first and last ventricular activation), local depolarization durations in precordial leads (V1-V8d), and their mean value (Vdmean) were calculated.
Results:
No difference in any parameters was found in the axes comparison. NSLBBp of anterior fascicle had longer Vdmean (50±2ms) compared to septal and posterior fascicle (45±2ms and 46±1ms with p˂0.05 and p=NS respectively) and proximal LBBp (44±1ms; p ˂0.015).
Conclusion:
Although NSLBBp of proximal left bundle branch or septal fascicle produces slightly more physiological activation compared to pacing of the posterior and anterior fascicle, the clinical relevance of this finding is yet unclear.
This work was supported by the Charles University Research program 260530/SVV/2020.