ABC | Volume 112, Nº5, May 2019

Guideline Brazilian Fetal Cardiology Guidelines – 2019 Arq Bras Cardiol. 2019; 112(5):600-648 vessels: number – that should be three; position – SVC on the right, aorta on the middle and pulmonary artery on the left; size – SVC slightly smaller than aorta that should be slightly smaller than the pulmonary artery and finally, alignment – the SVC is more posterior, aorta is in the center and pulmonary artery is anterior. 19 In this plane, the right and left bronchi are observed. 2.2.6. Step 6 – 6 th Level: Three Vessel and Trachea View Immediately above this plane, i.e., tilting the transducer a bit further in the cephalic direction, a view of two large arches connecting with the descending thoracic aorta is obtained. The one on the left is the ductus arteriosus that originates from the pulmonary artery and the other on the right is the aortic arch, both connecting with the descending aorta. This view makes a figure that suggests the letter V. The trachea appears as an anechoic structure surrounded by a hyperechoic line which corresponds to cartilage, being situated in front of the spine, slightly to the right. In this view, the aortic arch turns toward the left, which is defined exactly by its relation to the trachea. If the trachea is to the right of the aortic arch, the arch is turned toward the left and vice versa. It is worth highlighting that, the use of color flow mapping should be used during all screening steps and levels, and it is of particular importance during this final view. Both arches should present flow in the same direction, always directed from the heart toward the descending thoracic aorta (Figure 2.2). 2.3. Screening for Congenital Heart Disease During the First Trimester Because CHD are the most common severe congenital defects and the least diagnosed by routine obstetric ultrasound, the challenge over recent years has been early screening methods for fetal heart disease, considering the fact that the majority of babies affected by heart disease are born to mothers who do not present the classic indications for fetal echocardiography. Older studies have shown a sensibility of up to 40% in the detection of CHD in fetuses with increased nuchal translucency (NT), between weeks 11 and 14 of gestation (above the 99 th percentile). Focusing on fetuses with increased NT and normal karyotype, they demonstrated an incidence of heart disease 5 to 7 times greater in this group. 20-22 The most recent literature shows a sensibility of about 13.5% for the detection of cardiac abnormalities, being NT ≥ 3.5 mm considered an indication for fetal echocardiography. 23-25 Doppler flow analysis of the fetal cardiovascular system is also applied to screen CHD that may or not be associated with chromosome diseases. Several studies have argued that abnormal flow of the ductus venosus, i.e., the appearance of the reverse wave during atrial contraction (“a” wave) in fetuses with NT ≥ 3.5 mm increases the probability of CHD three-fold, whereas a normal flow pattern decreases the risk of heart disease by half. 21 The presence of tricuspid regurgitation during the first trimester of pregnancy is highly associated Figure 2.2 – Aorta and pulmonary artery appear elongated, going toward the descending aorta. Both converge to the aorta forming an image similar to a V letter. The trachea is to the right of the aortic arch, demonstrating that the latter descends to the left. During color flow mapping, both arches are observed to have flow in the same direction, i.e., from the heart toward the descending thoracic aorta. AoA: aortic arch; DA: ductal arch; SVC: superior vena cava; T: trachea. DA DA SVC SVC AoA AoA 607