242 Clinical presentation and long-term outcome of non immune and isolated atrioventricular block when congenital or diagnosed during childhood: a French multicentric study on 141 patients.

Purpose: When isolated and non immune, prevalence of congenital and childhood atrioventricular blocks (AVB) is extremely low and little is known about their natural history. Methods: a multicentric study retrospective from 1980 to 2009 allowed inclusion of 141 children from 13 French referral centers. Included children presented an AVB diagnosed in utero, at birth or during childhood before the age of 15 years, without structural heart abnormalities and without maternal antibodies. Results: 26 congenital and 114 childhood AVB were included. Symptoms lead to diagnosis in 15,6% whereas AVB was asymptomatic in 84,4%. 73% AVB were complete and 26,2% AVB were incomplete at first presentation. 21 of these incomplete blocks (56,7%) progressed to permanent complete AVB. Narrow QRS complexes were found in 69,2% congenital and 91,2% childhood AVB. In the 112 (79,4%) implanted children, mean duration between AVB diagnosis and pacemaker implantation was 35 months. Pacemaker primo-implantation occurred during the first year of life for 18 children and 90 children (63.8%) were paced before 10 years old. Pacing was required for symptomatic bradycardia in 37,5% whereas prophylactic cardiac pacing accounted for 61,6%. The median follow-up was 96 months (from 6 to 384 months). 85,1% experienced no complication and neither dilated cardiomyopathy nor death had occurred at last follow-up. Pacemaker-related complications appeared in 11,6%. Conclusion: We describe the largest reported experience with isolated and non immune congenital and childhood AVB. Such a block is a nodal damage from unknown origin that may postnatally progress in incomplete forms. Outcome is not influenced by age at diagnosis. Prognosis is very good with no late-onset dilated cardiomyopathy, a few pacemaker-related complications in the modern technological era and no death at last follow-up. [ABSTRACT FROM AUTHOR]