ABC | Volume 112, Nº5, May 2019

Guideline Brazilian Fetal Cardiology Guidelines – 2019 Arq Bras Cardiol. 2019; 112(5):600-648 Table 7.2 – In utero management of bradycardias Diagnosis Primary causes In utero management GOR/LOE Comments Sinus bradycardia Ectopic atrial pacemaker Rule out fetal distress as the cause of bradycardia I/A Can be seen in atrial isomerism Sinus node dysfunction (including immune mediated or infection) Observation until bradycardia resolves I/A Test for anti-Ro/LA antibodies Maternal IgG/IgM for TORCH diseases and parvovirus Secondary causes: maternal medications, maternal hypothyroidism, fetal distress or fetal CNS abnormalities Treat underlying cause of bradycardia I/A Blocked atrial bigeminy Atrial extrasystoles Observe / reduce maternal stimulants I/A 10% risk of fetal SVT Weekly auscultation of fetal HR until arrhythmia resolves AVB Maternal anti-Ro/La antibodies Observation I/A Structurally normal heart Dexamethasone for second-degree block or first-degree block with findings of cardiac inflammation IIb/B Endocardial fibroelastosis, associated valvular or myocardial dysfunctions For CAVB to prevent death or cardiomyopathy IIb/B 4–8 mg∕day IVIG (note: IVIG as prophylaxis is not recommended) IIa/C Sympathomimetics for HR < 55 bpm or higher rates associated with fetal hydrops Ib/C CAVB not related to antibodies Observation I/A Associated with structural defects such as CTGA, left atrial isomerism CAVB related to channelopathies Observation I/A Avoid QT-prolonging drugs AVB: atrioventricular block; CAVB: complete atrioventricular block; CNS: central nervous system; CTGA: corrected transposition of great arteries; GOR: grade of recommendation; HR: heart rate; IVIG: intravenous infusion of gammaglobulin; LOE: level of evidence; mg: milligrams; SVT: supraventricular tachycardia; TORCH: toxoplasma IgG, Rubella IgG, Cytomegalovirus IgG, and Herpes. Source: adapted from Donofrio et al. 17 than the AV, tachycardia due to ectopic atrial focus or junctional reciprocating tachycardia are the most frequent diagnosis. 132,133,136 Atrial flutter presents with atrial rates above 400 bpm, with variable atrioventricular conduction (2:1, 3:1, 4:1) and ventricular rates (200–250 bpm). 17,137,138,141,169 Ventricular tachycardia is identified as atrioventricular dissociation, with atrial rate lower than ventricular, varying from 100 to 400 bpm. When it coexists with bradycardia periods, the possible diagnosis is long QT syndrome, which may manifest as monomorphic ventricular tachycardia, torsade de pointes, ventricular dysfunction, atrioventricular valve regurgitation, and fetal hydrops. 138,172 7.4.2.2. Treatment The first choice for medical treatment of supraventricular tachycardias in most centers continues to be transplacental digoxin, given that it is safe and widely used during gestation. 17,137,138,141,173,174 The doses should be high, since only 50–70% crosses the placental barrier. The recommended loading dose is 3.0 mg during the first 48 hours of treatment, i.e., 0.50 mg every 8 hours. The maintenance dose is 0.25–0.75 mg/day, varying in accordance with isolated experience of each service and maternal serum level. Daily control of digoxin level is mandatory, and it should be kept between 1 and 2 ng/mL. If it is not possible to administer it orally, intravenous lanatoside C may be used as an alternative. If the arrhythmia has not reversed 631