ABC | Volume 112, Nº5, May 2019

Guideline Brazilian Fetal Cardiology Guidelines – 2019 Arq Bras Cardiol. 2019; 112(5):600-648 Figure 7.1 – Suggested approach for pregnant women with positive antibodies, without fetal CAVB. CAVB: complete atrioventricular block; ms: miliseconds. Positive anti-RO and/or anti-LA antibodies without CAVB Monitor the mechanical PR interval weekly from weeks 18–26 Mechanical PR stable < 150 ms Progressive increase or mechanical PR > 150 ms After week 26, follow-up every 4 weeks after birth Weekly follow-up until week 26 and every 2 weeks afterwards Consider dexamethasone treatment continues to have technical limitations and is still undergoing experimental studies. Indications for delivery should be analyzed based on the degree of fetal manifestations. In fetuses with significant hydrops, with ventricular rate < 50 bpm and pulmonary maturity (after week 34 of gestation), delivery should be considered, with immediate postnatal pacemaker implant. 163 In fetuses before week 26 of gestation, with heart rate < 45 bpm and hydrops, in utero pacemaker implant, still in experimental phase, may be a therapeutic option. 164-168 In fetuses between weeks 26 and 34 of gestation, the risks of prematurity and the manifestations of CAVB should be weighed together. The in utero suggested manaegment of fetal bradycardia is summarized in figure 7.2. 7.4. Fetal Tachycardia Fetal tachycardia is diagnosed when fetal heart rate is > 180 bpm. In utero treatment depends on gestational age, etiology, degree of hemodynamic compromise (presence of hydrops), mother’s clinical condition, and potential maternal risks of fetal treatment. The therapeutic decision should be based on fetal vs. maternal risks. Medical treatment is indicated for fetuses with sustained or intermittent tachycardias with hydrops and/or ventricular dysfunction, unless gestation is close to term, with fetal pulmonary maturity, thus minimizing the risks of preterm birth. 17,129,131-133,136,140,142,169,170 Tables 7.3 and 7.4, respectively, demonstrate the management of tachyarrhythmias and antiarrhythmic drugs. 17 The suggested management approaches for fetal tachycardias are shown in Figures 7.3, 7.4, and 7.5. 7.4.1. Intermittent Tachycardias Intermittent tachycardia is defined when it is present for less than 50% of the exam period, the minimum observation time being 30 minutes. Sinus tachycardia is determined by atrial and ventricular activation with 1:1 A:V conduction and heart rate over 160 bpm and, usually, below 180 bpm. It is frequently associated with an underlying fetal or maternal abnormal condition, such as fever, stress, or use of medication. Its cause should be treated. As an isolated finding, it does not have clinical significance and does not require treatment. 137,138,141 Intermittent ventricular tachycardia, with ventricular rate over 200 bpm is extremely rare and may evolve to important hemodynamic impairment and hydrops; for this reason, treatment is indicated. 629