Ventricular asynchronisms measured by radionuclide ventriculography in left bundle branch area pacing: an observational prospective study

The extent of left and right intra- and inter-ventricular asynchronism across various ECG patterns in patients with left bundle branch area pacing (LBBAP) remains unclear.

To assess intra- and inter-ventricular asynchronisms in different LBBAP ECG patterns using radionuclide ventriculography (RVG).

We prospectively performed 58 RVG assessments on non-consecutive patients with LBBAP at a single center from 2021 to 2024, with a median follow-up period of approximately 11 months post-implantation [4.8-16.2]. The primary indication for implantation was high-degree atrioventricular block (58%). LBBAP ECG patterns were categorized according to EHRA consensus (1) into deep septal pacing (DSP), left bundle branch pacing (LBBP), and left ventricular septal pacing (LVSP). We measured both left and right intra-ventricular asynchronisms as well as interventricular asynchronism, calculated by determining the time difference in milliseconds (ms) between the onset of contraction in the left and right ventricles (LV and RV), based on manually delineated regions of interest on LV and RV images. These asynchronism measures were then correlated with the different LBBAP ECG patterns.

The mean left ventricular ejection fraction (LVEF) was 53 % ± 13, with no significant differences among LBBAP subgroups. The DSP pattern was observed in 29 patients (50%), LBBP in 20 patients (35%), and LVSP in 9 patients (15%). Compared to the DSP group, the LBBP group exhibited significantly lower left intraventricular asynchronism (34.0±13 vs. 47.8±21, P=.03), and significantly lower interventricular asynchronism (-1.5±25 vs 33.8± 41, P =.006). No significant differences were observed in left intraventricular or interventricular asynchronism between LBBP and LVSP, as well as in right intraventricular asynchronism across all groups. In a multivariate regression model, the V6-V1 interpeak interval significantly correlated with interventricular asynchronism (B=-0.7, P=.009), while V6 R wave peak time (RWPT), QRS duration and the presence of bundle branch block were not significant predictors.

Overall, LBBP and LVSP patterns exhibited similar asynchronism characteristics. Compared to DSP, LBBP demonstrated a significant reduction in left intraventricular and interventricular asynchronisms, which was inversely correlated with the V6-V1 interpeak interval. The extent to which these differences may influence long-term outcomes and heart failure progression remains unknown.

Left intraventricular asynchronism