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Prenatal diagnosis of isolated mirror-image right aortic arch with vascular ring by fetal echocardiography

Objective 
To improve the prenatal echocardiographic diagnostic accuracy for fetus with isolated mirror-image right aortic arch which combined with vascular ring by analyzing and accumulating its echocardiographic features. 
 
 
Methods 
Echocardiographic signs were analyzed retrospectively and fetal echocardiographic features were accumulated in 16 cases with prenatal diagnosis of isolated mirror-image right aortic arch with left-side ductus arteriosus which formed vascular ring between January 2014 and February 2016. All cases were confirmed by neonatal echocardiography. 
 
 
Results 
The fetal echocardiography characters: ① In 3-vessel and trachea view, fetal right aortic arch was demonstrated a U-shaped appearance of the great vessels, the right arm of the 'U’ represented the aortic arch and its left branch with ductal continuation. ② In 3-vessel and trachea view or upper axial mediastinal transverse view, left innominate artery passed straightly to the left of the trachea.Left innominate artery and right-side ductus arteriosus were overlapped and the distance of two vessels was very close. ③ In double arch view and longitudinal view for ductus, Left innominate artery did not connect to descending aorta or ductus arteriosus and did not involve in the formation of vascular ring. ④ Color Doppler played an important role in diagnosis of this disease. Power Doppler or high-definition imaging easily showed color overflow and wrongly displayed the crossed relationship of left innominate artery with descending aorta as the anatomical connection, and caused the misdiagnosis of this disease as double aortic arch. 
 
 
Conclusions 
Isolated mirror-image right aortic arch with vascular ring is not rare in the fetal period. Because ductus arteriosus is large and patent during the prenatal period, it is easily mistaken for the crossed relationship of left innominate artery with descending aorta as the anatomical connection and finally misdiagnoses this anomaly as double aortic arch. The keys to accurate diagnosis of the disease are clearly visualization of the innominate artery and its relationship with descending aorta and ductus arteriosus by scanning different views. 
 
 
Key words: 
Echocardiography; Fetal; Mirror-image right aortic arch; Vascular ring; Double aortic arches