Temporal analysis of stimulation parameters evolution in the left bundle branch area pacing

Physiological stimulation is an increasingly utilized modality of cardiac stimulation. In our study, we aim to evaluate the temporal evolution of stimulation parameters in the Left Bundle Branch Area Pacing (LBBAP) following implantation.

We analyzed 206 patients who underwent implantation of a pacemaker or cardiac resynchronization therapy (CRT) involving the LBA in our center Between 2022 and 2023. A polygraphic system was employed to measure the duration of the QRS complex pre- and post-implantation, alongside the Left Ventricular Activation Time (LVAT) and the peak interval from V6 to V1 (PV6-PV1), as well as the presence or absence of R' in V1. Identical measurements were conducted on surface ECGs during follow-up assessments one month and one year post-implantation.

70.4% of the cohort were male, with a mean age of 75 years. A total of 77% received conventional pacemakers. The most frequent indication for implantation was symptomatic atrioventricular block, while ventricular dysfunction was the predominant reason for CRT. An overwhelming 87% of patients exhibited cardiovascular risk factors, and 65% had a history of cardiac disease. At the time of the initial implantation, 65% of patients demonstrated R' in V1. A significant narrowing of the baseline QRS (10.6 ms, 95% CI 6.6-14.6, p < 0.01) was observed compared to the stimulated QRS at initial implantation, albeit with a significant increase between the one-month and one-year measurements (7.19 ms, 95% CI 4.8-9.6, p < 0.01 and 1.89 ms, 95% CI -3.0-6.8, p < 0.01), while still maintaining a reduction relative to the baseline QRS. Significant differences in LVAT (7.8 ms, 95% CI 5.1-9.9, p < 0.01) were evident at implantation and at one month, with greater values observed at implantation. Identical results were obtained in the CRT analysis. No significant differences were found in PV6-PV1. Significant differences were noted in the presence of R' in V1, with 24% of patients losing this finding after one month, and 45% among the CRT subgroup.

Our findings indicate an elongation of QRS measurements post-implantation of a pacemaker or CRT with LBBAP involvement in our series, both at one month and one year, while remaining narrower than the baseline QRS. A shortening of the LVAT was observed at one month, followed by elongation at one year. Regarding the presence of R' in V1, by one month, 24% of the cohort had lost this finding, increasing to 45% in the separate analysis of patients with pacemaker-CRT and defibrillator-CRT.