Prenatal Diagnosis of Interrupted Aortic Arch with Intact Ventricular Septum and Persistent Left Superior Vena Cava at 20 Weeks: A Case Report.

Interrupted aortic arch (IAA) is a rare, duct-dependent congenital heart defect that usually occurs with a ventricular septal defect (VSD) and is strongly associated with 22q11.2 microdeletion. Prenatal detection is difficult because the four-chamber view may appear nearly normal. We report a 33-year-old woman referred for fetal echocardiography at 20 weeks 4 days of gestation. Abdominal and cardiac situs were normal, with levocardia, a normal cardiac axis, and a regular rhythm (fetal heart rate 145 bpm) with 1:1 atrioventricular conduction. There was marked ventricular disproportion: the left ventricle was small (diastolic diameter 3.90 mm, Z-score −3.68) compared with the right ventricle (9.14 mm, Z-score +1.69), and the left atrium was small. Flow across the foramen ovale was reversed (left-to-right). The interventricular septum was intact. The aorta arose from the left ventricle and was markedly hypoplastic. The aortic isthmus measured 1.04 mm (Z-score −3.85) on the transverse view of the upper mediastinum, and on sagittal greyscale and colour Doppler imaging the aortic arch could not be traced in continuity with the descending aorta. The pulmonary arteries were confluent and the ductus arteriosus was normal. A persistent left superior vena cava draining into the coronary sinus was also seen. The findings were consistent with IAA. The parents were counselled about the guarded prognosis, and amniocentesis was offered to rule out aneuploidy and 22q11.2 deletion. This case shows that ventricular disproportion, reversed foramen ovale flow, and a small ascending aorta should prompt careful evaluation of the aortic arch, and that early prenatal diagnosis supports genetic testing, informed counselling, and planned delivery at a centre with paediatric cardiac surgery.