Electrophysiological characteristics of lead-position-dependent EGM uninterrupted transition during left bundle branch pacing
Authors: Shen Jiabo , Jiang Longfu , Wu Hao , Zhang Lu , Li Hengdong , Pan Lifang 
Published: June 2024

AbstractBackground and AimsLeft bundle branch pacing (LBBP) is a novel pacing strategy that improves ventricular synchrony by utilizing the native conduction system. However, the current standard practices limit continuous monitoring of paced electrocardiogram (ECG) and intracardiac electrogram (EGM) transition, which may result in overlooked or misinterpreted subtle transitions. This study aimed to explore the electrophysiological characteristics of the lead-position-dependent EGM continuous transition and evaluate their clinical significance.MethodsThis observational study included patients referred for LBBP due to symptomatic bradyarrhythmia. A continuous pacing and recording technique was employed, allowing real-time monitoring of progressive alterations in the paced QRS complex as the lead penetrates deeper into the ventricular septum. EGM and ECG parameters were continuously monitored and analyzed.ResultsThe study encompassed 105 patients, with selective LBBP achieved in 88 patients (83.8%). The amplitude of ventricular EGM predictably changed with radial interventricular septum depth and peaked in the mid-septum. As the lead was inserted into the left ventricular subendocardium, the ventricular current of injury (COI) declined to a level approximating that of the right septum. Continuous recording technique enabled real-time monitoring of the entire perforation process and the subtle variations that exist among different perforation modalities. The discernment of discrete was feasible through the examination of unfiltered EGM, suggesting that selective LBB capture can also be confirmed by observing the subtle morphological transitions within the ventricular COI.ConclusionsThe continuous recording technique provides a more detailed understanding of the radial depth of the pacing lead throughout the implantation process. It simplifies the implantation procedures and facilitates the prevention or early detection of perforations. Future studies are needed to validate these findings and explore their clinical implications.What’s new?Utilization of Ventricular Electrogram (EGM) for Lead Positioning: The amplitude of ventricular EGM changes predictably with radial interventricular septum depth, peaking in the mid-septum. This provides a useful way to determine whether the lead is located on the left, right, or middle of the ventricular septum.Real-time Monitoring of Perforation Process: The continuous recording technique enables real-time monitoring of the entire perforation process. This feature helps to distinguish the subtle variations that exist among different perforation modalities, facilitating early detection and prevention of perforations.Confirmation of Selective Left Bundle Branch Pacing (SLBBP): The emergence of a discrete ventricular current of injury (COI) may serve as a novel characteristic of SLBBP. This suggests that SLBBP can be confirmed by observing the subtle morphological transitions within the ventricular COI.