Effectiveness of sotalol as first-line therapy for fetal supraventricular tachyarrhythmias

Fetal supraventricular tachycardia (SVT) and atrial flutter (AF) can be associated with significant morbidity and mortality. Digoxin is often used as first-line therapy but can be ineffective and is poorly transferred to the fetus in the presence of fetal hydrops. As an alternative to digoxin monotherapy, we have been using sotalol at presentation in fetuses with SVT or AF with, or at risk of, developing hydrops to attempt to achieve more rapid control of the arrhythmia. The present study was a retrospective review of the clinical, echocardiographic, and electrocardiographic data from all pregnancies with fetal tachycardia diagnosed and managed at a single center from 2004 to 2008. Of 29 affected pregnancies, 21 (16 SVT and 5 AF) were treated with sotalol at presentation, with or without concurrent administration of digoxin. Of the 21, 11 (6 SVT and 5 AF) had resolution of the tachycardia within 5 days (median 1). Six others showed some response (less frequent tachycardia, rate slowing, resolution of hydrops) without complete conversion. In 1 fetus with a slow response, the mother chose pregnancy termination. The 5 survivors with a slow response were all difficult to treat postnatally, including 1 requiring radiofrequency ablation as a neonate. One fetus developed blocked atrial extrasystoles after 1 dose of sotalol and was prematurely delivered for fetal bradycardia. Three grossly hydropic fetuses with SVT showed no response and died within 1 to 3 days of treatment. In conclusion, transplacental sotalol, alone or combined with digoxin, is effective for the treatment of fetal SVT and AF, with an 85% complete or partial response rate in our series.