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Updated | Sanghee Ro Fetal Tachyarrhythmia Management General Considerations: • Recommend transplacental therapy for sustained fetal tachycardia (occurring at least > 50% of the monitoring time) and when HR > 200 bpm • If the heart rate is > 180 bpm with a 1:1 atrioventricular ratio, SVT is the probable diagnosis • If the heart rate has atrial rates >300 bpm and an atrioventricular ratio of 2:1, 3:1 or even 4:1 atrioventricular conduction, atrial flutter is the probable diagnosis • If the fetus is tachycardic and the atrioventricular ratio is <1, the rhythm is likely either VT or junctional ectopic tachycardia • It is important to remember that transplacental antiarrhythmic treatment requires at least 48-72 hours to achieve therapeutic fetal drug levels o It is premature to say a medication has failed until therapeutic levels are achieved. • Recommend fetal echocardiogram every 48-72 hours until conversion to normal heart rate and rhythm • Goals for antiarrhythmic drug therapy: o Restore a normal fetal heart rate o Prevent or reverse fetal heart failure o Avoid premature delivery (if possible) < 35 weeks gestation: 3rd line 2nd line 1st line SVT No hydrops Flecainide Flecainide +Digoxin OR Sotalol + Digoxin Flecainide + Sotalol OR Amiodarone Hydrops Flecainide +Digoxin Sotalol + Digoxin OR Flecainide + Sotalol Amiodarone + Digoxin
Updated | Sanghee Ro >35 weeks gestation: • Consider early delivery for sustained tachyarrhythmia (>50% of monitoring period) and > 200 bpm o City call cardiologist should be aware and available to co-manage tachyarrhythmia • For non-sustained tachyarrhythmia < 200 bpm, recommend observation, fetal heart monitoring and biophysical profile monitoring Drug Dosages and Maternal Monitoring:* 1. Flecainide: a. Uniform dosing at 100 mg PO q8h (i.e. 300 mg/day) i. Maximum dosing: 450 mg/day if no response ii. Half-life of 20 hours b. Maternal contraindications: i. Congestive heart failure, Brugada syndrome, coronary heart disease c. Maternal monitoring: i. Baseline and daily ECG to watch for QRS prolongation ii. Baseline maternal echocardiogram given drug’s negative inotropic effects iii. Telemetry d. Target trough level: 200-1000 mcg/L considered therapeutic range 2. Digoxin: a. If starting in conjunction with flecainide or sotalol: 250 mcg PO q8h (without loading dose) i. Half-life of 35-48 hours 3rd line 2nd line 1st line Atrial Flutter No hydrops Sotalol Sotalol + Digoxin Sotalol + Flecainide OR Amiodarone Hydrops Sotalol + Digoxin Sotalol + Flecainide OR Amiodarone Amiodarone + Digoxin
Updated | Sanghee Ro b. Loading dose (only if starting as monotherapy): i. 500 mcg PO (as first dose), followed by 250 mcg PO q8hours x 2 doses (3 total doses) c. Trough after 3rd loading dose d. Maintenance dose: 125-250 mcg PO TID (375-750 mcg/day) e. Maternal contraindications: i. WPW, high-degree AV block hypertrophic cardiomyopathy f. Maternal monitoring: i. Daily ECGs to evaluate for ST segment changes g. Target trough level 1.5-2.5 ng/mL 3. Sotalol: a. If hydropic: 80 mg PO q8h i. Consider 160 mg PO q12h if maternal weight > 100 kg b. Non-hydropic: 80 mg PO q12h i. Consider 80mg PO q8h if maternal weight > 100 kg c. Half-life of 12 hours d. Maximum dose of 480 mg /day e. Maternal contraindications: i. Bradycardia, hypotension, asthma f. Maternal monitoring: i. Daily ECGs to evaluate for prolonged PR and QTc intervals g. Target therapeutic range: < 2.5 mg/L 4. Amiodarone a. Loading dose: 1.2-2.4 g/day for 2-7 days b. Maintenance dose: 0.2-0.4 g/day i. Half-life of 56 days c. Maternal monitoring: i. Daily ECGs for prolonged QTc d. Target therapeutic range: 1-2.5 μg/mL *Discuss all treatment plans with cardio-obstetric subspecialists (maternal-fetal medicine, adult cardiologist, obstetrician). References: 1. Batra AS, Silka MJ, Borquez A, Cuneo B, Dechert B, et al. Pharmacologic management of cardiac arrhythmias in the fetal and neonatal periods: A scientific statement from the American Heart Association. Circulation March 5, 2024;149:e937-e952. 2. Alsaied T, Baskar S, Fares M, et al. First-line antiarrhythmic transplacental treatment for fetal tachyarrhythmia: A systematic review and meta-analysis. J Am Heart Assoc 2017;6:e007164. 3. Miyoshi T, Maeno Y, Hamasaki T, et al. Antenatal therapy for fetal supraventricular tachyarrhythmias JACC 2019;64(7):874-885.
Updated | Sanghee Ro 4. Malhame I, Gandhi C, Tarabulsi G, et al. Maternal monitoring and safety considerations during antiarrhythmic treatment for fetal supraventricular tachycardia. Obstet Med 2018;12(2):66-75.