Left atrial isomerism with complex cardiovascular malformation on prenatal ultrasound and vascular casting

Left atrial isomerism (LAI) is a rare type of heterotaxy syndrome1. The most common anomalies in fetuses with LAI are absence of the hepatic segment of the inferior vena cava (IVC), interrupted suprarenal IVC segment with enlarged azygos or hemiazygos vein continuation, and azygos vein passing posterior to the aorta and running up to join the superior vena cava (SVC)2. Since LAI was first described by Baillie et al.3, prenatal ultrasound diagnosis of LAI with mild or no cardiac malformations has been reported by different groups; however, LAI with complicated cardiovascular malformations is rare. Cardiologists should be familiar with the cardiovascular malformations associated with LAI because they may affect the surgical treatment after birth. Here, we report a case of LAI with complicated cardiovascular malformations in which the enlarged azygos vein returned to the left SVC, as shown clearly on prenatal ultrasound with glass-body rendering and by postmortem vascular corrosion casting. A 25-year-old Chinese pregnant woman (gravida 2, para 0) was referred to our maternal–fetal medical center at 24 + 2 weeks' gestation with suspected heterotaxy syndrome. Two-dimensional color Doppler imaging revealed the liver located in the middle and the stomach on the right side of the abdomen, double SVC, single atrium, left ventricular dysplasia, mitral atresia, IVC joining the enlarged azygos vein which later inserted into the left SVC, aortic arch coarctation with widened pulmonary artery and left arterial duct, bilateral atria with left atrial appendage morphology, hepatic veins inserting directly into the right side of the single atrium, double-outlet right ventricle and aberrant right subclavian artery arising from the descending aorta, suggesting LAI (Figures 1-4). The fetus died in utero at 26 + 1 weeks of gestation. Following induction, a male fetus weighing 1056 g was delivered. Subsequent anatomical examination and tracheal vascular corrosion casting, performed with informed consent from the parents, confirmed the ultrasound diagnosis and demonstrated additional findings including a right spleen, interrupted aortic arch (rather than aortic arch coarctation), the descending aorta arising from the origin of the right pulmonary artery, a two-lobed right lung, double-outlet right ventricle and complete transposition of the great arteries (Figure 5). Compared with previous cases of LAI, the present case demonstrated complex cardiac malformations. It was difficult to achieve an accurate prenatal ultrasound diagnosis due to the early gestational age of the fetus and the high complexity of the aortic and pulmonary artery malformations; however, vascular casting provided an accurate three-dimensional representation of the vascular system of the fetal heart. The detailed anatomical information provided by vascular corrosion casting technique may improve the accuracy of prenatal imaging diagnosis. In China, Wang's team applied for the first time, and patented, the modified acrylonitrile-butadiene-styrene vascular corrosion casting technique in fetuses with complex congenital heart disease and achieved an optimal display of cardiovascular and visceral malformations4. The authors summarized the following key casting steps: (1) casting should be conducted within 48 h after induction of labor to avoid insufficient or failed perfusion due to blood coagulation; (2) selecting an appropriate cannula is essential for casting; a 1.2-mm scalp needle for children was used in the present study and good results were produced by infusing the casting material through the umbilical vein; (3) the casting material should be kept at an appropriate concentration, which is between 5% and 8%5. In conclusion, use of the glass-body mode on prenatal ultrasound may facilitate the diagnosis of LAI by allowing observation of the interrupted IVC with enlarged azygos vein continuation. Postmortem vascular corrosion casting can display stereoscopically the spatial relationship between the abnormal LAI course and the other blood vessels. This work was supported by the Hubei Provincial Health Committee, China (No: WJ2019F096).