Ovine model of pediatric complete heart block

Objectives: Complete heart block is a significant clinical problem that can limit the quality of life in affected children. A large animal model of permanent, pacemaker-dependent atrioventricular block (AVB) that mimics the size and growth characteristics of pediatric patients was established.

Methods: After implantation of dual-chamber pacemaker devices with fixed leads, AVB was produced by interrupting His-bundle conduction using radio-frequency ablation at the base of the non-coronary cusp of the aortic valve in 14 immature lambs. Subsequent interrogation of pacemakers and electrocardiographic (ECG) measurements determined the persistence of heart block.

Results: AVB was produced in 13 animals by interrupting the His bundle. One animal died due to ventricular fibrillation during ablation proximal to the tricuspid annulus and one post-operative stroke. Surviving sheep required continuous ventricular pacing (mean of 67.7 days).

Conclusions: This is a report on a successful creation of a large animal model of pediatric complete heart block. We anticipate this model to study the effect of long-term chronic pacing and the advancement of cell-based treatments to repair complete heart block in children.