ABC | Volume 112, Nº5, May 2019

Guideline Brazilian Fetal Cardiology Guidelines – 2019 Arq Bras Cardiol. 2019; 112(5):600-648 ventricular outflow tract, the mitral valve is significantly abnormal, with annular dilation, resulting in severe mitral regurgitation and LA dilation. The foramen ovale is usually quite restrictive, or the interatrial septum is intact, and there is left ventricular endocardial fibroelastosis, which also compromises the subvalvular apparatus of the mitral valve. Most fetuses with this anatomical presentation have some degree of fetal hydrops, with a high risk of death in utero or of triggering premature labor with immediate neonatal death. This disease appears to be the worst spectrum of the mitral valve arcade, where the chordae tendineae are fused and shortened. It is believed that this anatomical complex primarily compromises the mitral and aortic valves, associated with endocardial fibroelastosis, leading to dilation of left chambers. Restricted left to right flow at the atrial level contributes to significant LA dilation which compresses the right chambers and increases central venous pressure. This seems to be the physiopathology of fetal hydrops, which is present in 70–80% of cases, with polyhydramnios being observed in 100% of cases described by Vogel et al. 44 Aortic valve opening, in these cases, may reduce the degree of mitral regurgitation and LA pressure, and may treat or improve fetal hydrops and bring the gestation closer to term. 201 Opening of the atrial septum may be considered for the same procedure, potentializing the effects of aortic valvuloplasty. Besides the intervention, this is a very severe clinical condition, which has a significant impact on fetal and neonatal mortality. 8.5. Fetal Pulmonary Valvuloplasty PAIVS is associated with variable hypoplasia of the right ventricle, tricuspid valve, and right ventricular outflow. The disease’s most severe spectrum presents fibromuscular atresia of the infundibulum and pulmonary valve, with significant hypoplasia of the right ventricular cavity and the tricuspid valve, associated with abnormal coronary circulation. Contrastingly, in the more favorable spectrum, the pulmonary valve atresia is membranous; the tricuspid valve annulus diameter and the right ventricular volume are close to normal, and there is an absence of abnormalities in the coronary arteries. Some cases of critical pulmonary stenosis observed during fetal life may evolve to total flow interruption between the right ventricle and the pulmonary artery, with consequent hypoplasia of the right ventricular chamber. These cases behave similarly to PAIVS with mild to moderate hypoplasia of the right ventricle. 214 The goal of fetal intervention in cases of PAIVS and critical pulmonary stenosis is to promote growth and functional development of the right ventricle and to increase the chances of biventricular circulation during the postnatal period. The identification of potential candidates for the procedure should be based on the risks of the fetus’ evolving to univentricular circulation without fetal intervention and the possibility of changing this progression. 198 The selection of candidates for intervention should follow the criteria previously described in the “Indications” section. Another important criterion in this decision is the presence of signs of fetal heart failure characterized by reverse “a” wave in the ductus venosus flow, which denotes increased right atrium pressure and possible fetal hydrops development. This hemodynamic condition is observed in fetuses who have significant tricuspid regurgitation and very reduced right ventricular compliance. 215 From the technical point of view, this intervention is more difficult and challenging than aortic valvuloplasty. Due to the reduced dimensions and hypertrophy of the right ventricle, associated with its anatomical characteristics (outflow located anterior and far away from inflow), the positioning of the needle below the pulmonary valve requires very experienced and skilled fetal specialist. The RV puncture should be performed as far as possible from the outflow. In cases with valve atresia, the guidewire utilized should have a slightly firmer tip, in order to allow the interventionist to perforate the valve. 201 Some authors prefer to introduce a thinner needle through the first one to perforate the valve or proceed the valve perforation with the 17 G needle itself. 200 After reaching the pulmonary artery, the guide is positioned in one of the pulmonary branches or across the ductus arteriosus, to provide balloon support. For this intervention, the same balloon:annulus ratio as fetal aortic valvuloplasty is employed. The result of the intervention is evaluated by observing the anterograde flow through the pulmonary valve, the reduction of reverse flow through the ductus arteriosus, and the presence of pulmonary insufficiency. Pulmonary insufficiency is a marker of success, and it decreases as gestation advances. Restenosis during fetal life is commonly observed. Most cases will require a new valvuloplasty during the neonatal period. 200,216,217 In many cases, total recovery of the right ventricle does not occur at birth, making accessory pulmonary flow necessary, either with ductus arteriosus stenting or surgical confection of a systemic to pulmonary shunt (modified Blalock-Taussig). 201 8.6. Fetal Atrial Septostomy Although HLHS neonatal survival continues to improve worldwide and, slowly in Brazil, some anatomical and functional aspects are risk factors for poor clinical outcome and neonatal or postoperative 639