Gordon A, Jimenez E, Cortez D. Pediatr Cardiol. 2024 Aug;45(6):1165-1171. doi: 10.1007/s00246-022-02942-9. Epub 2022 Jun 9.PMID: 35678827 Free PMC article.
Take Home Points:
- Despite procedural complexity, His Bundle pacing is achievable in smaller sized pediatric population as well as in individuals with structural cardiac abnormalities with variable and challenging conduction system anatomy.
Commentary by Dr. Srikant Das (Texas Children’s Hospital- Austin), Congenital and Pediatric
Cardiac EP section editor:
The authors examine outcomes and short term to medium term follow up data in 24 patients following conduction system pacing (CSP) (23 His-Bundle pacing, 1 Left Bundle Branch area pacing).
The small cohort is heterogenous with a mixture of pediatric and adult patients and includes patients with structurally normal hearts as well as congenital structural cardiac defects. The age ranges from 8 -39 years, including 7 adults and includes 12 patients with a variety of structural congenital heart defects with biventricular physiology.
There are no reported complications during implant or over a median follow up time of just under two years. Their cohort comprised of pediatric and adult patients with 50% (12) having selective His Bundle pacing. They analyzed the patients based on selective versus non-selective His Bundle pacing implants. As intended for CSP, the post implant narrower QRS duration was a median of 100 ms in both groups.
The authors report that all patients with normal baseline left ventricular function retained normal left ventricular function on follow-up. Additionally, four patients with depressed ejection fractions ranging from 32% to 45% had improvement of at least 5–10% in their ejection fraction.
There is no report in the study cohort of any abrupt rise in capture threshold or loss of His Bundle capture. They report on follow up for the non-selective His-bundle implants, the median His-capture threshold was 2 V@0.4 ms (range 1.5–6 V@0.4–0.5 ms). The pertinent details of case with high threshold of 6V@0.4–0.5 ms is not discussed. The authors report five patients programmed in a unipolar ventricular pacing mode but details regarding the reason is not available.
While the procedural complexity and increased duration due to the workflow of His Bundle pacing is well recognized, including the need for electroanatomic mapping, the authors do not provide a procedural time, anesthesia duration or fluoroscopy time/dose for the cases.
Perspective:
Due to the rapid evolution of CSP, guidelines are behind clinical practice and conduction system pacing guidelines are not available in pediatric or adults with congenital heart disease (ACHD). The authors work adds to the growing body of safety and feasibility in this population. But the authors do not provide discussion regarding the process of selection at their center for these patients to undergo conduction system pacing attempts. The recent rapid adoption of conduction system pacing for adults with structurally normal hearts is of interest due to its potential as alternative modality of cardiac resynchronization therapy (CRT) as well as a primary CRT strategy. Recently though there is a shift from His Bundle pacing towards left bundle branch area pacing.
A rise in the His Bundle capture threshold is a significant concern after His Bundle pacing in large adult literature including a late His Bundle capture threshold rise reported in approximately one‐third of the patients during the long‐term follow‐up period. There is even report of abrupt loss of capture that occurred even though the His Bundle capture threshold remained stable for 3 years. In addition, the procedural learning curve, small pediatric sizes, and variation in conduction system anatomy adds to the challenge to avoid complication.
While it is well-known that higher conventional right ventricular pacing percentage is associated with increased risk of pacing induced cardiomyopathy, most paced patients are subjected to decades of pacing-induced dyssynchrony and never develop pacing induced cardiomyopathy. Better understanding is needed in pediatric and ACHD population for optimal patient selection for conduction system pacing and even for optimal type of CSP – His bundle pacing versus Left Bundle Branch area pacing.
