Abstract
BACKGROUND: His-bundle pacing (HBP) facilitates physiological ventricular activation. However, concerns about long-term threshold deterioration persist. The predictors of chronic threshold elevation are not yet well established. METHODS: Between February 2018 and December 2021, HBP was attempted in 95 patients undergoing pacemaker implantation. Strict success criteria (threshold ≤ 2.0 V/0.4 ms) were applied, and 47 patients with successful HBP were monitored for over 3 years. We assessed pacing thresholds for both the His-bundle and right ventricle (RV) at implantation, 1 week, 1 month, and annually thereafter. Lead shape was evaluated using chest radiography. Patients were categorized into two groups based on their His-bundle pacing threshold: stable (≤ 3.5 V/0.4 ms) and deteriorated (> 3.5 V/0.4 ms). RESULTS: Deterioration in His-bundle pacing thresholds was associated with increased RV pacing thresholds. Deterioration in RV pacing occurred earlier, with significant differences observed at 1 week post-implantation (median RV: 1.87 vs. 3.25 V/0.4 ms, p = 0.032; His-bundle: 1.0 vs. 1.25 V/0.4 ms, p = 0.212). Multivariate analysis identified an RV threshold ≥ 3.0 V/0.4 ms at 1 week (OR 10.7, p = 0.036) and lead bending on chest radiography (OR 12.8, p = 0.018) as independent predictors of chronic His-bundle pacing threshold deterioration. CONCLUSION: An elevated RV pacing threshold at 1 week post-implantation and lead flexion at implantation may serve as early indicators of long-term deterioration in His-bundle pacing thresholds. When the RV pacing threshold increase is detected, it is important to closely monitor the patient and frequently adjust the output settings to prevent pacing failure.