Fetal arrhythmias: natural history and management.

The aim was to delineate the significance and natural history of fetal arrhythmias and provide information about their management. A cohort of 114 infants with fetal arrhythmias detected during prenatal ultrasound (US) screening were studied. All subjects underwent echocardiography and were treated as clinically indicated. Postnatal outcome was obtained in 100% of infants until 1 year of age. The incidence of fetal arrhythmias was 0.3%. Among the 87 fetuses with atrial extrasystoles, 2.3% developed supraventricular tachycardia (SVT) in utero. Of the 10 SVT cases, only five required antiarrhythmic therapy in utero with digoxin and propafenone, which successfully restored sinus rhythm in 100% of fetuses, both nonhydropic and hydropic. Sinus bradycardia was associated with structural anomalies in 5 of 6 patients and only 2 of 4 fetuses with atrioventricular block survived. It is concluded that prognosis is good for most fetal tachyarrhythmias, whereas it is less favorable for bradyarrhythmias.