Prenatal diagnosis of double aortic arch: can we predict airway obstruction (pseudo‐ CHAOS ) and need for airway EXIT ?

Double aortic arch (DAA) is rare and results from failure of regression of one, usually the right, of the dual aortic arches. Its population prevalence remains uncertain, being estimated from those developing tracheal and/or esophageal compression in infancy and requiring surgery1, 2. Its presentation as the cause of in-utero airway compression, mimicking congenital high-airway obstruction syndrome (pseudo-CHAOS), is rarely documented3. Therefore, the sonographic features of DAA predicting perinatal complications, specifically tracheal compression requiring airway intervention (ex-utero intrapartum treatment (EXIT) procedure) at delivery, are unknown, reducing the ability to counsel families effectively. The three vessels and trachea (3VT) view was introduced into prenatal screening at our hospital (25 000 deliveries per year) in 2013. Nine fetuses with DAA diagnosed between 2015 and 2016 were referred for congenital heart disease, of which four had an abnormal 3VT view as the sole referral indication. Median gestational age at diagnosis was 23 (range, 21–36) weeks. Fetal echocardiography was performed to identify arch dominance and the origin of the head and neck vessels. Airway obstruction was recognized by lung brightness, flattened diaphragm and polyhydramnios (amniotic fluid index > 95th centile) (Figure 1). Seven (78%) of the nine fetuses had isolated DAA, six (67%) had right arch dominance, two (22%) had equal arch dominance and one (11%) had left arch dominance (Figure 2). All fetuses had left-sided arterial ducts. Eight (88%) fetuses showed no tracheal and/or esophageal obstruction at presentation or on serial ultrasound examination. The fetus with left arch dominance presented with signs of tracheal compression at 30 + 3 weeks' gestation. EXIT procedure was discussed, but spontaneous delivery at 33 weeks occurred with good perinatal adaptation and initial stability. However, hyperinflation ensued, requiring emergency intubation within 24 h and demise occurred at 1 week postdelivery. Abnormal lung histology was identified at postmortem. One fetus with Ebstein's anomaly was hydropic and demised and one family chose to terminate the pregnancy. Six neonates were delivered at term without prenatal airway obstruction and no perinatal complication. One had right atrial isomerism, atrioventricular septal defect and unobstructed anomalous pulmonary venous connection to the atrial mass and was stable at birth. This patient underwent division of the DAA at 1 month of age as part of initial surgical palliation for congenital heart disease. Another patient with isolated DAA had surgical division at 12 months of age. In our small series, only one fetus had tracheal compression at presentation and none developed pseudo-CHAOS during surveillance. However, we are uncertain whether the mid-trimester absence of obstruction is a reliable predictor of an open airway at delivery. Incorporation of 3VT into screening programs increases prenatal diagnosis of arch abnormalities, including DAA, and continues to raise questions about subsequent counseling and management. As we identify the configuration of DAA and ductal sidedness, we may learn more about risk factors for airway obstructions requiring prenatal planning for EXIT procedure. D. P. Naidu1*, C. Wohlmuth2,3 and H. M. Gardiner2 1Division of Pediatric Cardiology, McGovern Medical School, University of Texas Health Science Center at Houston & Children's Memorial Hermann Hospital, 6410 Fannin St, Suite 425, Houston, TX, 77030, USA; 2The Fetal Center at Children's Memorial Hermann Hospital, Department of Obstetrics, Gynecology and Reproductive Sciences, UT Health - McGovern Medical School, Houston, TX, USA; 3Department of Obstetrics and Gynecology, Paracelsus Medical University, Salzburg, Austria *Correspondence. (e-mail: durga.p.naidu@uth.tmc.edu)