(1198) Toxicity associated with maternal antiarrhythmic therapy for treatment of fetal tachyarrhythmias: a case series

Objective:
To evaluate maternal toxicities associated with oral antiarrhythmic therapy for management of fetal tachyarrhythmias.

Study Design:
We conducted a retrospective case series of pregnant people with a fetal tachyarrhythmia diagnosis treated at a large academic medical center between January 2010 and September 2022. We reviewed cases of singleton gestations with an obstetric ultrasound or fetal echocardiography confirming a diagnosis of fetal tachyarrhythmia and who delivered ≥24 weeks’ gestation. Data on maternal oral antiarrhythmic treatment (digoxin, flecainide, sotalol, and/or amiodarone), side effects, monitoring for potential drug toxicity (i.e. electrocardiograms, laboratory surveillance), and neonatal outcomes were abstracted from medical records.

Results:
Of 42 patients found to have fetal tachyarrhythmia, 22 (52.3%) received maternal antiarrhythmic therapy. The majority had fetal supraventricular tachycardia (54.5%), 9 had fetal atrial flutter (40.9%), and 1 (4.5%) had non-sustained fetal atrial tachycardia. Of these, nearly half (N=10) patients developed maternal side effects with concern for drug toxicity requiring therapy modification. The most commonly reported side effects were severe nausea and emesis (N=8). Several patients had maternal electrocardiogram changes (N=5), including AV block and T wave abnormalities, attributed to digoxin; one patient had QRS prolongation secondary to flecainide. Less common therapy-altering side effects included lethargy, presyncope, visual hallucinations, and transaminitis (Figure).

Conclusion:
Although maternal treatment of fetal tachyarrhythmias is often indicated for fetal benefit, in this cohort, 45% of individuals required alteration of therapy due to concern for maternal toxicity. Our findings emphasize the need for standardized maternal monitoring guidelines and prompt therapeutic adjustments to balance fetal treatment efficacy with maternal safety.