The value of cardiovascular magnetic resonance in the diagnosis of fetal aortic arch anomalies

Background: Here we report our preliminary experience of using fetal cardiovascular magnetic resonance (CMR) imaging, particularly with transverse views at the level of the aortic arch, in the diagnosis of aortic arch anomalies.

Materials and methods: Between January 2013 and December 2015, routine prenatal obstetric ultrasound (US), echocardiography (Echo), and 1.5 T CMR were performed on approximately 600 pregnant women. CMR included balanced fast field echo and single-shot fast spin echo sequences. The images were analyzed using an anatomic segmental approach by two radiologists. The prenatal imaging findings were compared with postnatal diagnoses, from imaging or autopsy.

Results: A total of 22 cases with suspected aortic arch anomalies were found by prenatal Echo. These included the following: right aortic arch, 18 cases; double aortic arch, 2 cases; atrial isomerism, 3 cases including 2 with right aortic arch; and pulmonary atresia, aortic overriding and ventricular septal defect, 1 case. Fetal CMR diagnoses were: right aortic arch with aberrant left subclavian artery, 9 cases; right aortic arch with mirror-image branching, 8 cases; double aortic arch, 4 cases; left aortic arch with right aberrant subclavian artery, 1 case. 16 cases were born alive and subsequently underwent evaluation by Echo or MRI and 6 cases had autopsies. There were 23 aortic arch anomalies. Prenatal Echo misdiagnosed 5 of these (5/23), and missed the diagnosis in 4 cases (4/23). Consequently, the accuracy of prenatal Echo was 60.8% (14/23). Both prenatal Echo and CMR misdiagnosed the same single case as a double aortic arch. The correct diagnosis was found to be right aortic arch with aberrant subclavian artery. Consequently, the accuracy of fetal CMR was 95.6% (22/23).

Conclusion: Unlike prenatal Echo, fetal CMR is unaffected by fetal position. Fetal CMR with transverse views at the level of the aortic arch is a useful adjunct for the diagnosis of fetal aortic arch anomalies.