Expanded Characterization of Ventricular Electrogram in Selective Left Bundle Branch Pacing: A Cohort Study of Patients With/Without LBB Potential

ABSTRACT Aims The electrophysiological transition from non‐selective to selective capture with electrogram (EGM)‐splitting during threshold testing is the gold standard for verifying left‐bundle‐branch (LBB) capture in LBB‐area pacing. Our preliminary study identified distinct ventricular EGM morphologies in patients with recordable LBB potentials. The present study extends these observations to patients with and without LBB potentials and characterizes the electrophysiological features and potential mechanistic correlates of these EGM phenotypes during selective LBB (S‐LBB) pacing. Methods Patients with confirmed S‐LBB pacing were categorized into three groups based on the comparison between intrinsic and paced ventricular EGM morphologies: concordant (CE), similar (SE), and discordant (DE). Baseline characteristics, pacing indications, pacing parameters, and V6 R‐wave peak times (RWPTs) were analyzed. Results S‐LBB pacing was achieved in 387 patients (86.8%). After excluding patients with LBBB, an LBB potential was recorded in 276/341 patients (80.9%). Among patients with an LBB potential, V‐V6(P) RWPT and V‐V6(S) RWPT were strongly correlated in the CE ( r = 0.889) and SE groups ( r = 0.825), whereas V‐V6(S) RWPT was significantly shorter in the DE group. Among patients without an LBB potential, the DE group also showed a shorter V‐V6(S) RWPT. There was a strong correlation between V‐V6(P) RWPT and V‐V6(S) RWPT in the CE group ( r = 0.815), while the DE group exhibited a poor correlation ( r = 0.351). Conclusions Continuous recording using a 200 Hz high‐pass filter effectively confirms S‐LBB pacing by revealing discrete EGM signals. Concordant or similar intrinsic and paced EGMs may suggest shared conduction pathways, whereas discordant EGMs might reflect distinct conduction routes.