Continuous Pacing Recordings Reveal Distinct Right Ventricular Activation Patterns in Left Bundle Branch Area Pacing

Left bundle branch area pacing (LBBAP), a physiological pacing method, is widely used, but the pathways of right ventricular (RV) activation under different pacing modalities remain incompletely characterized.

This study aims to investigate RV activation sequence under three left bundle branch pacing modalities: left ventricular septal pacing (LVSP), non-selective left bundle branch pacing (ns-LBBP), and selective left bundle branch pacing (s-LBBP).

We included 250 patients with confirmed s-LBBP via stimulus-to-ventricular (S-V) separation. Continuous pacing recording identified mode transition points by ECG changes. RV activation pathways were analyzed by comparing R-wave peak time (RWPT) in leads V1 and V6 and its changes under different output voltages.

Patients were divided into two groups based on V1 RWPT changes. In the V1 RWPT shortening group (75 cases), V1 RWPT was longest in LVSP (112.61 ± 10.59 ms), with no significant difference between ns-LBBP and s-LBBP. In the V1 RWPT prolongation group (175 cases), V1 RWPT was significantly prolonged in s-LBBP (124.63 ± 17.05 ms). V6 RWPT was longest in LVSP (81.63 ± 10.45 ms), with no significant difference between ns-LBBP and s-LBBP.

In most cases, RV activation time was similar between LVSP and ns-LBBP. S-LBBP exhibited the longest RV activation time. However, in nearly 30% of patients, RV activation time was shortened after left bundle branch capture compared to the LVSP mode with isolated ventricular septal myocardial capture.