368. Current practices in maternal monitoring during antiarrhythmic treatment for fetal SVT: A scoping review

Background In pharmacologic management of fetal supraventricular tachycardia (SVT), antiarrhythmic agents are administered to the pregnant patient serving as a vehicle of transplacental delivery to the fetus. Given that antiarrhythmic therapy can have profound maternal adverse effects, administration of initial loading and dose adjustments should involve deliberate attention to pharmacologic principles with close maternal monitoring for adverse effects. We reviewed current monitoring practices and maternal complications of transplacental antiarrhythmic therapy for fetal SVT. Methods A query of the Embase database for search terms ”Fetal” or ”Foetal” and ”Supraventricular Tachycardia” or ”SVT” yielded 93 titles, of which 19 articles detailing the modalities of therapy for Fetal SVT were reviewed. Results The 19 articles represented 565 cases of fetal SVT, 111 of which had developed hydrops fetalis. Of these cases, 184 received a course of digoxin alone and 33, 56, and 5 cases received a combination therapy of digoxin with flecainide, sotalol, or amiodarone. Flecainide, Sotalol, and amiodarone were given as monotherapy in 89, 77, and 6 cases, respectively. Maternal monitoring information was available in 15 studies. Investigators performed electrocardiograms (EKGs) at baseline and during follow-up in 12 studies, and monitored electrolytes in five. Two studies reported a mandatory cardiologist consultation for all mothers and two studies considered performing echocardiography in select mothers. Digoxin and flecainide levels were measured in eight and four studies, respectively. Toxicity was reported in 5 patients: two on digoxin monotherapy, two on flecainide monotherapy, and one on combination of digoxin and flecainide. Conclusion Pharmacologic management of fetal SVT is generally safe for mothers with normal baseline cardiac assessments and close monitoring of symptoms, EKG, electrolytes, and/or drug levels. Future prospective studies on the treatment of fetal SVT should also include a systematic monitoring strategy for mothers, with consistent reporting of adverse reactions.