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Table 1 Arrhythmic drugs recommend in fetal atrial flutter based on statement AHA [3]

From: Successful treatment of neonatal atrial flutter by synchronized cardioversion: case report and literature review


Therapeutic maternal dose range

Therapeutic level and effect



LD: 1200–1500 µg/24 h IV, divided every 8 h MD: 375–750 µg/d divided every 8 to 12 h PO (Fetal intramuscular dose: 88 µg/kg q12 h, repeat 2 times)

0.7–2.0 ng/mL Maternal Nausea, fatigue, loss of appetite, sinus bradycardia, first-degree AV block, rare nocturnal Wenckebach AV block

Nausea/vomiting +++, sinus bradyarrhythmia or AV block +++, proarrhythmia Fetal intramuscular: sciatic nerve injury or skin laceration from injection


160–480 mg/d divided every 8 to 12 h PO

Levels not monitored Bradycardia, first-degree AV block, P and QRS widening, QTc ≤ 0.48 s

Nausea/vomiting, dizziness, QTc ≥ 0.48 s, fatigue, BBB, maternal/fetal proarrhythmia


LD: 1800–2400 mg/d divided every 6 h for 48 h PO; lower (800–1200 mg PO) if prior drug therapy MD: 200–600 mg/d PO Consider discontinuation of drug and transition to another agent once rhythm is converted or hydrops has resolved.

0.7–2.8 µg/mL Maternal/fetal sinus bradycardia, decreased appetite, first-degree AV block, P and QRS widening, QTc ≤ 0.48 s

Nausea/vomiting ++, thyroid dysfunction ++, photosensitivity rash, thrombocytopenia, BBB, QTc ≥ 0.48 s, maternal/fetal proarrhythmia, fetal torsades with LQTS, fetal goiter, neurodevelopmental concerns

  1. Proarrhythmia means worsening of an arrhythmia as the result of treatment. AV indicates atrioventricular block; BBB bundle-branch block; CNS central nervous system; ECG electrocardiogram; IV intravenously; LD loading dose; LQTS long QT syndrome; MD maintenance dose; PO orally; VT ventricular tachyarrhythmia; and +++, very common; ++, common; and +, occasional.