P2.B026: Ascending aorta dilation in pediatric patients with antibody mediated complete congenital heart block

Background: Complete heart block in children is rare and may be associated with maternal autoimmune disease, congenital heart disease, cardiothoracic surgery, or remain idiopathic after extensive investigation. The natural history and pathophysiology of congenital complete heart block is not well understood. Previously, an association between ascending aorta dilation and congenital heart block associated with maternal autoimmune disease has been demonstrated. However, the relationship between ascending aorta dilation and idiopathic complete heart block has not yet been described.

Methods: A retrospective chart review of pediatric patients < 19 years with complete congenital heart block evaluated at the Mayo Clinic from 2010-2023 was performed. Patients diagnosed with complete heart block associated with congenital heart disease, cardiothoracic surgery, or with proven/suspected lyme disease were excluded.

Results: Twenty-five patients with congenital complete heart block met the inclusion criteria. The mean age of all patients was 12 ± 6 years and 14 (56%) were male. Of these, 9 (36%) patients had history of positive maternal autoimmune antibodies and the other 16 (64%) were considered to have idiopathic complete heart block. Ascending aorta dilation was present in 9 (100%) patients with immune mediated congenital heart block and 1 (6%) patient with idiopathic complete heart block. The mean ascending aorta z-score was 2.9 ± 1.8 in patients with immune medicated complete heart block and 1 ± 0.9 in patients with idiopathic complete heart block (p =0.0017).

Conclusion: Dilation of the ascending aorta was present in all patients with complete heart block associated with maternal autoimmune disease. In contrast, dilation of the ascending aorta was uncommon in patients with idiopathic complete heart block suggesting a distinct aortopathy associated with fetal exposure to maternal autoantibodies.