Assessing modified chest leads as a substitute for electrophysiological systems in left bundle branch area pacing

Abstract Background Left bundle branch area pacing (LBBAP) typically requires an electrophysiological (EP) system. However, many catheterization laboratories in Asian countries lack access to these expensive EP recording systems. Modified chest leads (MCL1 and MCL6) have been routinely used as substitutes for V1 and V6 for continuous monitoring, but their role in LBBAP implantation when assessed via a pacing system analyzer remains unclear. This study aimed to evaluate the feasibility of MCL as an alternative to a conventional EP system during LBBAP implantation. Methods Between 2023 and 2024, LBBAP was performed in 73 de novo patients with atrioventricular block at Chosun University Hospital, South Korea, using Abbott stylet-driven leads. We compared continuous recordings from a 12-lead ECG-based electrophysiology system with MCL recordings from a PSA. Parameters analyzed included right bundle branch block (RBBB) morphology changes in V1 (or MCL1), QRS transition during differential pacing, left ventricular activation time (LVAT) in V6 (or MCL6), V6-V1 (MCL6-MCL1) interpeak interval, and QRS duration. Results A total of 73 patients (32 men, age 74.3 ± 10.8 years) were included. LBBAP was successfully achieved in all cases, with 24 patients undergoing left bundle branch pacing, 42 undergoing left fascicular branch pacing, and 7 undergoing left ventricular septal pacing. An rSR’ or QR pattern in V1 or MCL1 was observed in all patients. QRS transition Bland-Altman analysis demonstrated that the majority of measurements fell within the 95% limits of agreement between the programmer and the 12-lead ECG system. The intraclass correlation coefficient indicated good agreement for QRS duration (0.849), LVAT in V6 (0.850), and the V6-V1 interpeak interval (0.813). Conclusion Modified chest leads showed a good correlation with the EP system during LBBAP implantation. These findings suggest that MCL may serve as a reliable alternative for cardiac rhythm monitoring in settings where an electrophysiological recording system is unavailable.