Maternal antibodies against fetal cardiac antigens in congenital complete heart block.

An immunologic basis for congenital heart block has been proposed previously. To investigate the association between congenital heart block and maternal antibodies capable of crossing the placenta, we used immunofluorescence to examine serum samples from 41 mothers and 8 affected children, together with serum from controls, for antibodies to fetal cardiac tissue. Twenty-one mothers (51 percent) had IgG antibody reactive with fetal heart tissue, as compared with only 9 of 94 controls (10 percent; P less than 0.001). Three of 8 affected babies, but none of 50 healthy babies, had similar antibodies. The antibodies reacted with all myocardial tissue and were not directed specifically to the conduction system. They also reacted with other fetal tissues and could be distinguished from nuclear and smooth-muscle autoantibodies. We also observed a higher occurrence of antibodies to cytomegalovirus, but not to Epstein-Barr virus, in these mothers. Autopsy specimens from babies with congenital heart block examined by immunoperoxidase staining showed deposition of immunoglobulin and complement components in all cardiac tissues. These findings strengthen the case implicating immune reactivity related to maternal antibody in the development of some but not all cases of congenital heart block.