Late outcomes of congenital and childhood non-immune, isolated atrioventricular block: a French nationwide retrospective cohort study.

Aims: The natural history of congenital or childhood non-immune, isolated atrioventricular block (AVB) is poorly defined. We aimed at clarifying its long-term outcomes.

Methods and results: We retrospectively studied 385 children with isolated, non-immune AVB diagnosed from in utero or up to 18 years of age, at 29 French medical centres, between 1980 and 2022. Patients with structural heart disease, endomyocardial fibrosis, or maternal antibodies were excluded. Atrioventricular block was asymptomatic in 314 (81.6%) and complete in 263 (68.3%) patients at the time of diagnosis. There was progression to complete AVB in 84/122 (68.8%) patients with incomplete AVB over 12 years (7-17). A total of 286/385 patients (74.3%) received a permanent pacemaker, implanted in the first year of life in 39 (14%) and before 10 years of age in 172 (60%) children. The pacing indication was prophylactic in 203 children (71%). Genetic screening was performed in 133/385 patients (34.5%), leading to the identification of a clinically actionable variant in 11 (8.3%) patients. After a median follow-up of 10 years (5-17), no patient died or developed endomyocardial fibrosis or dilated cardiomyopathy.

Conclusion: In this large nationwide study, the long-term outcome of congenital or childhood non-immune, isolated AVB was excellent. Most children required pacemaker implantation over time, albeit often as a prophylactic measure.