ABC | Volume 112, Nº5, May 2019

Guideline Brazilian Fetal Cardiology Guidelines – 2019 Arq Bras Cardiol. 2019; 112(5):600-648 flow across the valve assessed by Doppler techniques. Left ventricular to aorta Doppler gradient should not be used to classify the severity of the stenosis since, there is a frequent association of endocardial fibroelastosis and severe myocardial dysfunction in critical aortic stenosis. Reverse flow in the transverse arch, i.e., coming from the descending aorta to the ascending aorta; inverted flow at the atrial level (from left to right); monophasic left ventricular inflow (Doppler tracing across the mitral valve showing single A wave due to high filling pressures), and moderate or severe left ventricular dysfunction are the main functional parameters that suggest impending HLHS. 192-195 Ideally, when fetal intervention is considered to avoid left heart hypoplasia, left ventricular length Z score (long axis) should be > −2, meaning that the left ventricle is not hypoplastic yet. Occasionally, aortic valvuloplasty is performed in cases where the left ventricle has already some degree of hypoplasia (Z-score > −4 and < −2), and the main aim in these cases is to promote some anterograde aortic flow, which may improve coronary and encephalic perfusion and allow ascending aorta growth, knowing that the chances of left ventricular complete recovery are low. 192-195 8.1.2. Hypoplastic Left Heart Syndrome with Intact Interatrial Septum or Significantly Restrictive Foramen Ovale This situation is characterized by absent or minimal high velocity flow across the interatrial septum and bidirectional flow in the pulmonary vein with prominent reverse flow, with disappearance of the classic triphasic pattern. 196,197 8.1.3. Pulmonary Atresia with Intact Interventricular Septum or Critical Pulmonary Valve Stenosis with Signs of Evolving Right Heart Hypoplasia This disease is defined as membranous pulmonary atresia with identifiable pulmonary valve leaflets with intact interventricular septum, associated with minimal or no anterograde pulmonary blood flow; reverse flow in the ductus arteriosus, i.e., coming from the aorta to the pulmonary artery; some degree of right heart hypoplasia, with hypoplastic tricuspid valve annular diameter (Z score < −2), or evidence that the right ventricle has not grown during 2–4 weeks of observation. Cases with significant coronary to right ventricle fistulas are excluded. 198-200 8.1.4. Critical Aortic Stenosis with Massive Mitral Regurgitation and Giant Left Atrium This is a specific group of fetuses that has only recently been characterized as a subgroup of critical aortic stenosis. These cases present with left ventricular dilation, reverse flow in the transverse arch, and some degree of left ventricular dysfunction. Most of them are associated with fetal hydrops and may benefit from aortic valvuloplasty associated or not with atrial septostomy to reduce the risk of fetal or neonatal death. 44,201 8.2. Technical Considerations Pre-anesthesia fasting and tocolytic prophylaxis consist the main preparation for the procedure. Nifidipine, 20 mg orally, started 4–8 hours before the procedure, is the medication of choice for this purpose, since it has few side effects and is highly effective. 189 The intervention is performed under maternal regional block, preferably via spinal anesthesia. General anesthesia may also be used, but this has the disadvantage of hindering proper fetal positioning, given that maternal general anesthesia also anesthetizes the fetus. The fetal positioning is obtained with manual maneuvers allowing the fetal specialist to reach the target cardiac structure percutaneously. The ideal fetal position is pelvic with the spine downwards, leading to proceed the puncture as close as possible to the uterine fundus. 189 Fetal anesthesia may be intramuscular or intravenous via the umbilical cord. It is performed with a mixture of opioid (fentanyl), muscle blocker (pancuronium), and atropine at doses of 15 μg, 0.2 mg, and 0.02 mg per kilogram of fetal weight, respectively. A 20-G Chiba needle is used to administer this medication. 189,190,194 The heart is also accessed with a Chiba needle, 15 cm in length ranging from 17 to 19 Gauge. The entire procedure is monitored by ultrasound, which may be operated by either the fetal specialist or the fetal cardiologist. Once the abdominal wall is crossed, the needle reaches the amniotic cavity and the fetal thorax. 194 The target structure (aortic valve, pulmonary valve, or interatrial septum) is reached by direct heart puncture. Once the distal end of the needle has reached the target cardiac structure, a pre-assembled coronary angioplasty balloon catheter is advanced through the needle until the balloon is positioned across the structure to be dilated. The pressure with which the balloon is inflated varies, considering the diameter and the target structure. For semilunar valve dilation, the ideal balloon:annulus ratio is from 1.1 to 1.2. 193 After the balloon is completely deflated, the entire set (balloon, catheter, and puncture needle) is removed all together, at once. After the system is complete removed from the fetal heart, bradycardia and hemopericardium frequently occur. 190 Voluminous effusions should promptly be emptied via a new puncture with a 637