Temporal evolution of His bundle pacing thresholds: a sub-study of the PACE-CONDUCT trial

Abstract

Abstract Background His bundle pacing (HBP) has become a valuable alternative for cardiac resynchronization therapy, offering physiological pacing. This substudy of the PACE-CONDUCT trial aimed to explore the influence selective and non-selective HBP on threshold height. We assessed these parameters in patients with both normal conduction and bundle branch block conduction. Methods Our study included 61 consecutive patients with a median age of 73 years, who underwent a successful HBP implantation for indications such as sick sinus syndrome, AV Block 2 type 2, binodal disease, and ablate and pace therapy prior to AV-node ablation. Among these patients, 18 exhibited QRS durations exceeding 150 ms, indicating a complete and broad bundle branch block which made them candidates for cardiac resynchronization therapy (CRT). All patients received HBP implantation with the assistance of a 3D electroanatomical system. This system allowed for low-fluoroscopic, atraumatic evaluation of the His bundle (HB) area, presenting the His voltage as a color-coded map for precise electrode placement. Results The feasibility of bundle branch correction is generally accepted in selective HBP distal to the site of block, albeit associated with higher threshold values and potentially lower battery duration. Our analysis encompassed 61 patients who underwent HBP implantation, with 23 patients (37,7%) exhibiting selective HBP and 38 (62,3%) non-selective HBP. Remarkably, 10 out of the 23 patients with selective HBP demonstrated a complete bundle branch block correction after HBP implantation even with a basal QRS durations exceeding 150 ms. We evaluated HBP thresholds at implantation, one day post-implantation, and one month post-implantation, correlating these data with selective and non-selective HBP. Threshold values were converted to volts per millisecond (volts × milliseconds) for analysis. Statistical analysis conducted with IBM SPSS 29.0 revealed a significant difference at the day of implantation, indicating higher threshold capture in selective HBP compared to non-selective HBP (one-sided p-value: < 0.01, two sided p value 0.01). However, this difference could not be sustained at the one-day and one-month threshold follow-ups, suggesting normalization of the selective HBP threshold. Conclusion In our study, the initially higher threshold in selective HBP normalized within 24 hours compared to non-selective HBP. Additionally, our study demonstrated the feasibility of selective His pacing in patients with complete bundle branch block and broad QRS durations. These findings provide insights into HBP optimization and encourage further investigations with larger patient cohorts to validate our observations and enhance patient care in the realm of cardiac pacing.Threshold trend