[Clinical course of pre- and post-natal isolated congenital atrioventricular block diagnosed in utero]

We evaluated the pre- and postnatal outcome of isolated atrioventricular (AV) block detected during fetal life in order to identify factors that may affect the natural history of this lesion and to assess prenatal therapy. Over the past eight years, we consecutively evaluated 10 fetuses with complete AV block. The mean gestational age at diagnosis was 25.3 weeks and the mean heart rate was 57 bpm; two fetuses were hydropic. During pregnancy, one fetus suddenly died, while 6 out of 9 fetuses had a mean reduction in heart rate of 17.8 bpm; 4 patients had heart rate < 50 bpm. Five fetuses developed heart failure, which was severe in 2 cases and mild in 3. The mean gestational age at delivery was 31 weeks. Dexamethasone was administered to the mothers during pregnancy in 4 cases without modification of AV block and/or of heart rate, but in 3 out of 4 fetuses the general condition remained stable in spite of the reduction in heart rate in two of them. Sympathomimetic drugs were employed in 3 cases with an increase in fetal heart rate, but maternal discomfort appeared in two cases. Three newborns died during the first week of life, two of hydrops and one of persistent pulmonary hypertension. Cardiac pacing was performed in 6/9 patients within the first 8 months of life and in 3 within the first 2 days. In conclusion, morbidity and mortality are high when AV block is detected during fetal life. Negative prognostic factors are hydrops and a heart rate < 50 bpm. Pre-term delivery to enable cardiac pacing is probably the therapy of choice if gestational age is > 27-28 weeks. Sympathomimetic drugs are effective but are poorly tolerated by the mothers. Dexamethasone has no effect on AV block and/or heart rate, but may improve clinical tolerance of conduction disturbance.