Congenital atrioventricular block: histological aspects

It is known that maternal immunological factors such as systemic disease are involved in the genesis of cardiac conduction problems in the fetus but the histologic changes in the conduction system are less documented. We report the case of a 33-year-old woman with no significant medical history. Her first pregnancy was induced by Clomifene. At 17 weeks of gestation, the fetus presented sonographic abnormalities characteristic of a complete atrioventricular block. Biological investigations found anti-SSA and -SSB antibodies. Clinical history search for systemic disease was positive for photosensitivity, lasting 10 years, suggesting the diagnosis of systemic lupus erythematosus. The patient was treated with prednisone 20 mg per day but fetal death occurred at 29 weeks of gestation. Histological examination of the fetal heart showed an altered atrioventricular node and bundle of His with fibrosis, calcifications, endocardial fibroelastosis and mononucleated inflammatory cells. The search for these specific lesions can be determinant in establishing the disease pathogenesis; also, it is important to eliminate this diagnosis in an unexplained fetal death.