Background

His-bundle pacing (HBP) is an alternative modality of permanent pacing possibly preventing harmful effects of conventional right ventricular pacing such as electrical and mechanical dyssynchrony or pacing induced heart failure. HBP has evolved a favorable option of permanent pacing in the adult population. However, only sparse data is available on the efficacy and safety of HBP in children and younger patients with congenital complete heart block (CCHB). We report a high-volume single center experience of HBP in young patients with CCHB.

Methods

Patients with CCHB and without other congenital heart disease who underwent successful HBP between 01/2020 and 06/2021 were analyzed retrospectively in this study. All procedures were conducted with the use of a 3D mapping system and an electrophysiologic recording system. The right atrium and the His-bundle region were mapped with a decapolar diagnostic catheter. The pacemaker lead was then maneuvered along the basal interventricular septum until a His-bundle potential was identified and the lead was advanced into the septum. Threshold testing was performed aiming at values below 1.5/1.0 V/ms. Non-selective and selective HBP was identified according to previously published criteria. Acute procedural success was defined as successful lead implantation with adequate pacing thresholds and reproducible selective and/or non-selective HBP.

Results

The study population consisted of 5 patients (40% females). HBP was performed in all but one patient (80%) as a de novo pacemaker implantation. In one patient (20%) HBP was performed due to development of a pacemaker-induced cardiomyopathy after conventional right ventricular pacing. All patients who underwent HBP as a de novo pacemaker implantation had a left ventricular ejection fraction >55%. Median age at HBP was 16.2 {12.2; 25.4} years. All patients underwent left-sided pacemaker implantation. Back-up right ventricular pacing leads were not implanted in patients with de novo HBP. The patient with a pre-existing right ventricular pacing lead did not undergo lead extraction. Mean procedural duration was 106.8±17.1 minutes with a mean fluoroscopy time of 9.2±2.4 minutes and a mean area dosage product of 59.4±21.7 Gy*cm2. Venous lead access was achieved by puncture of the axillary vein in 4 patients (80%) and via the subclavian vein in one patient (20%). One patient (20%) showed excessive threshold increase of the His-bundle lead two days after implantation. The lead was revised and replaced by a conventional right ventricular lead as the patient had a normal left ventricular ejection fraction. Follow-up of the remaining patients with a mean duration of 356 days showed stable thresholds of the His-bundle lead without significant alterations compared to baseline values in all except one case in which pacing threshold rose above 2.5/1.0 V/ms. No patient suffered from clinical signs of heart failure. Mean QRS duration at the timepoint of last follow-up was 98±18 ms.

Conclusion

HBP for CCHB was safe and effective and resulted in narrow QRS morphologies during pacing in most cases. However, larger trials with longer follow-up periods are required to assess feasibility of HBP in young patients. Additionally, other conduction system pacing modalities like left bundle branch pacing may overcome limitations of HBP.