Septal Intramyocardial Purkinje Network: A Potential New Mechanism Explaining Left Bundle Branch Area Pacing
Xiaoke Liu1, Siva K Mulpuru2, Atta Behfar3
1Department of Cardiovascular Medicine, Mayo Clinic, Rochester, Minnesota, USA; Division of Cardiovascular Medicine, Mayo Clinic Health Systems, La Crosse, Wisconsin, USA.
JACC. Clinical Electrophysiology
|May 29, 2025
Summary
Left bundle branch area pacing (LBBAP) may activate the heart by directly capturing the intramyocardial Purkinje network. This mechanism explains the narrow QRS intervals observed during LBBAP, offering a new understanding of conduction system pacing.
Area of Science:
- Cardiology
- Electrophysiology
- Cardiac Anatomy
Background:
- Left bundle branch area pacing (LBBAP) is increasingly used for conduction system pacing.
- The physiological mechanism responsible for the narrow QRS interval during LBBAP remains unclear.
Purpose of the Study:
- To investigate the mechanism underlying the narrow QRS interval in LBBAP.
- To evaluate the role of the intramyocardial Purkinje network in LBBAP physiology.
Main Methods:
- Analysis of unique ECG and intracardiac recordings in 13 patients with unexplained LBBAP features.
- Examination of septal Purkinje fiber staining in human cardiac tissue.
- Assessment of findings in relation to the intramyocardial Purkinje network.
Main Results:
- Observed unexpected ECG patterns including alternating bundle branch blocks and variable bundle system recruitment.
- Noted correction of baseline right bundle branch block at low outputs.
- Intracardiac recordings showed rapid septal activation; extensive Purkinje tissue found deep in the septal myocardium.
Conclusions:
- Findings suggest a physiological role for the intramyocardial Purkinje system in LBBAP.
- Direct capture of Purkinje fibers may explain rapid biventricular activation and narrow QRS intervals.
- This provides a unifying explanation for counterintuitive LBBAP observations.
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