Characteristics and proposed meaning of intrinsic intracardiac electrogram morphology observed during the left bundle branch pacing procedure: A case report

Electrophysiological characteristics of lead position-dependent electrogram uninterrupted transition during left bundle branch pacing

BACKGROUND

The interrupted technique of left bundle branch pacing (LBBP) limits the continuous monitoring of paced electrocardiogram and intracardiac electrogram (EGM) transitions, which may result in overlooked or misinterpreted subtle transitions.

OBJECTIVES

This study aimed to explore the electrophysiological characteristics of lead position-dependent EGM continuous transitions to evaluate lead depth and to investigate the clinical significance of transseptal pacing modalities.

METHODS

A continuous pacing and recording technique enabled by a rotatable connector was used to allow the real-time monitoring of progressive changes in paced EGM and electrocardiographic morphology. Careful observations were conducted to evaluate whether there were significant changes in the amplitude and morphology of the ventricular current of injury (COI), R-wave peak times in leads V1 and V6, QRS duration, and impedance at different interventricular septal depths.

RESULTS

The study included 105 patients. Nonselective LBBP was achieved in 94 patients (89.5%), of whom 88 (83.8%) achieved selective LBBP (SLBBP). Left ventricular septal pacing was confirmed in 11 patients (11.5%). The amplitude of ventricular EGM predictably changed with radial septum depth and peaked in the interventricular septum (26.3±11.3 mV). As the lead was inserted into the left ventricular subendocardium, the ventricular COI declined to a level approximating that of the right septum (11.7 ± 6.3 mV for SLBBP vs 10.4 ± 5.8 mV for right ventricular septal pacing). When selective left bundle branch capture occurred, significant morphological transitions in the ventricular COI were observed in the unfiltered EGM.

CONCLUSION

The continuous recording technique provides a more detailed understanding of pacing lead radial depth throughout implantation. COI amplitude and morphology variations can identify different pacing modalities, particularly in recognizing SLBBP.

Left bundle branch pacing guide by uninterrupted recording of intrinsic filtered and unfiltered intracardiac electrograms

BACKGROUND

Currently, the interrupted recording technique is commonly used to perform left bundle branch (LBB) pacing (LBBP). However, this method requires repeated testing to confirm that the LBB is captured and perforations are avoided. An automated solution may make this repetitive work easier.

CASE SUMMARY

LBBP was performed using an uninterrupted recording technique in an 86-year-old woman. Lead position and LBB capture was confirmed by the characteristics of the intrinsic filtered and unfiltered intracardiac electrograms.

CONCLUSION

Continuous mapping and recording technique may help achieve more accurate positioning of LBBP lead in the ventricular septum.

A Continuous Pacing and Recording Technique for Differentiating Left Bundle Branch Pacing From Left Ventricular Septal Pacing: Electrophysiologic Evidence From an Intrapatient-Controlled Study

BACKGROUND

Left bundle branch pacing (LBBP) is a promising approach for achieving near-physiologic pacing. However, differentiating LBBP from left ventricular septal endocardial pacing (LVS(e)P) remains a challenge. This study aimed to establish a simple and effective method for differentiating LBBP from LVS(e)P and to evaluate their electrophysiologic characteristics.

METHODS

LBBP, using continuous uninterrupted pacing and real-time monitoring of electrocardiograms along with intracardiac electrograms, was performed in 97 consecutive patients. We evaluated the electrophysiologic characteristics observed during LBBP using 6 modalities: right ventricular septal pacing (RVSP), intraventricular septal pacing (IVSP 1 and 2), LVS(e)P, nonselective LBBP (NSLBBP), and selective LBBP (SLBBP).

RESULTS

Of the 97 patients, 87 (89.7%) met the criteria (abrupt change in paced QRS morphology with a transition from Qr to QR/qR in lead V1 and shortening of stimulus to V6 R-wave peak time [Stim-V6RWPT] of ≥ 10 ms with constant output while rather than after lead screwing) for nonselective left bundle branch (LBB) capture. Selective LBB capture was observed in 82 patients (84.5%). The Stim-V6RWPT of NSLBBP and SLBBP were significantly shorter than LVS(e)P (respectively, 67.1 ± 8.7 ms, 67.0 ± 9.3 ms, and 82.1 ± 10.9 ms). Stim-QRSend was the narrowest in IVSP2 (136.6 ± 15.2 ms) instead of NSLBBP (140.0 ± 17.1 ms).

CONCLUSIONS

The uninterrupted pacing technique for differentiating LBBP from LVS(e)P in the same group of patients is feasible. Electrophysiologic evidence from our intrapatient-controlled study shows that LBBP and LVS(e)P differ in ventricular electrical synchronization.