ABC | Volume 112, Nº5, May 2019

Guideline Brazilian Fetal Cardiology Guidelines – 2019 Arq Bras Cardiol. 2019; 112(5):600-648 Table 7.4 – Antiarrhythmic drugs Drug Therapeutic dose Therapeutic serum level and effect Toxicity Digoxin LD: 0.5 mg (2 capsules) every 8 h for 48 h – 1.5 mg/d for 2 days 0.7-2.0 ng/mL Maternal nausea/vomiting, sinus bradyarrhythmia or AVB, proarrhythmia MD: 0.25–0.75 mg/day Fetal IM dose: 88 μg/kg every 12 h, repeat twice Nausea, fatigue, loss of appetite, sinus bradycardia, first-degree AV block, nocturnal Wenckebach AV block (rare) Fetal IM: sciatic nerve injury or skin laceration from injection Sotalol 160–480 mg/day every 8–12 h PO Levels not monitored Nausea/vomiting, dizziness, QTc ≥ 0.48 s, fatigue, BBB, maternal/fetal proarrhythmia Bradycardia, first-degree AVB, P and QRS widening, QTc ≤ 0.48 s Amiodarone LD: 1800–2400 mg/d divided every 6 h PO 0.7–2.0 μg/mL Nausea/vomiting, thyroid dysfunction, photosensitivity rash, thrombocytopenia, BBB, QTc ≥ 0.48 s, maternal/fetal proarrhythmia, fetal torsades with LQTS, fetal goiter, neurodevelopmental concerns MD: 200–600 mg/d PO Maternal/fetal sinus bradycardia, decreased appetite, first-degree AVB, P and QRS widening, QTc ≤ 0.48 s Consider discontinuation of drug and transition to another agent once normal rhythm is reestablished or hydrops has resolved. Propranolol 60–320 mg/d divided every 6 h PO 25-140 ng/mL Fatigue, bradycardia, hypotension, AV block, fetal growth restriction, increased uterine tone First-degree AVB, bradycardia, increased uterine tone Lidocaine LD: 1–1.5 mg/kg followed by infusion of 1–4 mg/min continuous IV 1.5-5 μg/mL Nausea/vomiting, neurological symptoms, proarrhythmia Mexiletine 600–900 mg/d divided every 8 h PO 0.5-2 μg/mL Nausea/vomiting, neurological symptoms, proarrhythmia Magnesium sulfate LD: 2–6 g IV over 20 min followed by 1–2 g/h < 6 mEq/L Fatigue, neurological symptoms If there is loss of patellar reflex and/or levels of> 6 mEq/L STOP infusion Treatment for > 48 h is not recommended but redosing may be considered if VT recurs Monitor patellar reflex Levels > 5 mEq/L associated with maternal changes on ECG and proarrhythmia AV: atrioventricular; AVB: atrioventricular block; BBB: bundle-branch block; ECG: electrocardiogram; IM: intramuscular; IV: intravenous; LD: loading dose; LOE: level of evidence; LQTS: long QT syndrome; MD: maintenance dose; PO: orally; VT: ventricular tachycardia. Source: afapted from Donofrio et al. 17 after 5 days, oral sotalol is initiated as second-choice drug. 175-177 This may be used with an initial dose of 80 mg every 12 hours, gradually increasing 40–80 mg every 3–5 day, until the arrhythmia is reversed or the maximum dose of 480 mg/day has been reached. In this case, the mother must remain in hospital for monitorization, with daily ECG control to measure the QTc interval, as well as serum levels of digoxin. In fetuses with significant hydrops and sustained tachycardia with elevated heart rate, sotalol may be initiated concomitantly with digoxin. Combined therapy has greater risks of maternal and fetal complications. If there is no therapeutic response in fetuses who are severely affected, the third-choice drug, amiodarone, may be used at a dose of 800–1,200 mg/ day. 178-179 This drug, however, has a significant toxicity for both mother and fetus. 180 If the fetal tachyarrhythmia continues, with important hemodynamic impairment and severe hydrops, direct fetal therapymay be necessary, via cordocentesis or direct intramuscular injection, given that, in this situation, there is a significant decrease in the transplacental passage of medications. 171,181,182 The risks and benefits of every situation must be weighed individually. Digitalis (dose of 0.03 mg/kg) or amiodarone (dose of 15 mg/kg) may be administered. Adenosine has not shown any effect in maintaining sinus rhythm, and it is not recommended for atrial flutter. 633