ABC | Volume 112, Nº5, May 2019

Guideline Brazilian Fetal Cardiology Guidelines – 2019 Arq Bras Cardiol. 2019; 112(5):600-648 death. 218 The presence of an intact atrial septum or severely restricted foramen ovale represents one of the worst risk factors of neonatal mortality. It causes deep hypoxemia after birth and pulmonary hypertension (venocapillary) triggered by pulmonary vein arterialization. 218 In this condition, resuscitation maneuvers are usually ineffective. Some hospitals recommend emergency Norwood operation, with mortality affecting 83% of patients by the sixth month of life. Even in those who underwent immediate neonatal atrial septostomy, mortality exceeds 48%. 218,219 These deaths are usually not directly related to the procedure and end up occurring after the first week of life. 196 It is believed that, in addition to deep neonatal hypoxemia, anatomical abnormalities secondary to in utero venocapillary hypertension are related to mortality. In these cases, anatomopathological studies have demonstrated arterialization of the pulmonary veins associated with lymphatic vessel dilatation. 219-221 It is estimated that the incidence of severely restrictive foramen ovale or intact interatrial septum associated with HLHS occur in 6% of cases, with some degree of restriction affecting, at least, 22% of patients. 219 Left atrial decompression during fetal life seems to be essential to the prevent poor immediate neonatal clinical presentation and the remodeling of the pulmonary vascular bed. 196 The main echocardiographic marker of significantly restricted foramen ovale during fetal life is the presence of high-velocity reverse flow in the pulmonary vein Doppler tracing, which shows an abnormal bidirectional pattern. 45 This finding indicates that blood is returning to the lungs during atrial contraction, because the LA cannot decompress to the left ventricle or the right atrium. 189 It is very important to examine at least one pulmonary vein with pulsed-wave Doppler during the echocardiogram of a fetus with HLHS. 222 The echocardiographer must have in mind that this piece of information may significantly change these patients’ outcome and the pre- and postnatal management. Other important features in this condition are pulmonary vein and LA dilation, atrial septum bulging into the right atrium, absent or minimal high-velocity flow across the interatrial septum. 189 The ideal moment to perform atrial septostomy is discussed. 196,223 Intending to prevent definitive damage to the pulmonary circulation, the intervention should ideally be performed immediately after the diagnosis. On the other hand, from the technical point of view, it is rather difficult to create an orifice in the interatrial septum that lasts for multiple weeks and prevent severe neonatal hypoxemia. It appears to be consensual that the ideal moment is between the 28 th to the 33 rd weeks of gestation when the fetus is of good size. During this period, it is feasible to use larger balloons with greater capacity to open wider orifices in the interatrial septum. 190,197 The use of stents in the interatrial septum has also been considered by some authors. 224,225 This procedure appears to be more challenging than atrial septostomy, mainly due to the difficulty of optimally positioning the stent in the septum. One of the main problems is to visualize the stent inside the metallic needle via ultrasound. Stent implantation is particularly interesting when the interatrial septum is very thick and, thus, does not allow for the opening of an orifice that is wide enough to alleviate pressure in the LA. Due to the profile of needles available for fetal interventions, the largest stent used is 3 mm, which may, in some cases, reach an internal diameter of 3.5 mm. 39,40 The rate of poor positioning and embolization is high, according to recent publications. In cases of embolization, the stent is buried in the atrium, without further complications, and the procedure may be completed with the septostomy. 224,225 8.7. Final Considerations of Fetal Cardiac Interventions With the development of fetal cardiac interventions, several important principles have been recognized. Technical success of the procedure does not always translate to clinical success after birth. Understanding the natural history of the malformation and continuously refining the criteria for patient selection are absolutely critical when one consider the creation of an invasive fetal cardiology programwhich includes potentially risky procedures. It is important to recognize that the majority of CHD are not fatal, and classic palliative treatment during the neonatal period is an option in many situations. However, for some anomalies whose natural history may be changed for the better, or for those with extremely severe prognoses, fetal intervention may be a therapeutic option. Table 8.3 indicates the class of recommendation and level of evidence for the different fetal cardiac interventions adapted form the Fetal Cardiology guidelines published by the AHA in 2014. 17 9. Acknowledgments These guidelines are the result of the work of many people whose intellectual, creative, “informatic,” and executive efforts, combined with those of the authors, constitute the basis of this document. Unfortunately, because of editorial reasons, it is not possible for all of them to appear among the authors who represent each group. The authors thank them here formally for their 640