CLINICAL AND SEROLOGICAL IDENTIFICATION OF 2 FORMS OF COMPLETE HEART-BLOCK IN CHILDREN

Objective. To study the association of maternal antibodies to Ro(SSA) and/or La(SSB) with isolated complete congenital heart block (CCHB) in children according to the child's age at detection. Methods. Sera fro m 17 mothers of 18 children with CCHB of unidentified cause were studi ed, Autoantibodies were measured by double immunodiffusion, enzyme lin ked immunosorbent assay (ELISA), Western blot, and immunoprecipitation from cell extracts. Statistical analysis used the chi(2) test with Ya tes' correction. Results. CCHB was diagnosed in 12 children of 11 moth ers before the age of 3 mo (Group A) and in 6 children of 6 mothers af ter the age of 17 mo (Group B), Seven Group A mothers and no Group B m other had connective tissue disorders; autoantibodies were found in 9/ 11 Group A and in 1/6 Group B mothers (p < 0.01), Eight Group A childr en needed a pacemaker and one other died of cardiac insufficiency, whe reas only one of the 6 Group B children needed a pacemaker. Interestin gly, this latter child was the only one from Group B whose mother's se rum contained autoantibodies. Irrespective of their age at diagnosis, the children with CCHB who needed a pacemaker and the one who died wer e born to mothers with autoantibodies (p < 0.001). Conclusion. CCHB de tected before the age of 3 mo is highly associated with the presence o f anti-Ro(SSA)/La(SSB) in the mothers, while CCHB diagnosed later is g enerally not, For epidemiological studies, the former type should be c onsidered early onset as opposed to late onset CCHB in the latter type , Establishing this clinicoserological distinction is also important f or the children, since it alerts the clinician to a more severe progno sis (necessity of a pacemaker), even in the rare occurrence of late di agnosed CCHB.