To summarize the pathological significance of retrograde flow in fetal aortic arch by analyzing the associated diseases and hemodynamic characteristics.

A retrospective study on retrograde flow in fetal aortic arch was conducted on fetuses with intra- or extra-cardiac abnormality. All data were collected from the database of Fetal Heart Disease Maternal Fetal Medicine Research Important Laboratories in Beijing from January 2013 to October 2016. Fetuses with normal cardiac structure and without extra-cardiac abnormality in late pregnancy were excluded from this study. Ultrasound images with description of retrograde flow in fetal aortic arch in report or presenting retrograde flow signal during scanning were recruited. All selected cases were reviewed and the diagnosis was reconfirmed. The signal of retrograde flow in the aortic arch was that the direction of blood flow in the aortic arch was inconsistent with that of the ductus arteriosus. Spectral Doppler was used to define systolic or diastolic retrograde flow and all cases were divided into four groups accordingly: middle-late systole, systole, diastole, systole+diastole for analysis. The etiology of retrograde flow in the aortic arch was analyzed based on cardiac structure abnormality and extra-cardiac abnormality. Clinical outcomes were followed up. Descriptive statistics was used to analyze all the data.

(1) Among 21 607 cases reviewed, 62 (0.29%) were recruited with the mean gestational age of (29.5±4.6) weeks and and average age of (26.1±2.9) years, respectively. (2) Fifty-eight (93.5%) of the 62 cases were diagnosed with cardiac structure and/or cardiac function abnormality, including 44 of left ventricular outflow abnormality and 14 of significantly reduced left ventricular volume with normal left ventricular function. The other four cases (6.5%) with extra-cardiac abnormality were all complicated with abnormal peripheral circulation resistance in fetal systemic circulation, which included intrauterine growth restriction resulting from placental insufficiency (three cases) and cerebral arteriovenous fistula (one case). (3) Retrograde flow filling the whole aortic arch was found in 32 cases (51.6%) with severe aortic stenosis or atresia, one (1.6%) with severe aortic regurgitation caused by absence of aortic valve and one (1.6%) with cerebral arteriovenous fistula. Retrograde flow with other causes mainly presented in the middle part and the distal isthmus of the aortic arch. (4) Retrograde flow presented in the middle and late systole was observed in 24 cases (38.7%) of significantly reduced left ventricular volume with normal left ventricular function, while those presented in the diastole were found in cases with severe aortic regurgitation, large coronary fistula, or abnormal peripheral circulation resistance (six cases, 9.7%). Thirty-two fetuses (51.6%), diagnosed with left ventricular outflow tract obstruction, showed retrograde flow in both systole and diastole. (5) Among the 62 pregnancies, 46 (74.2%) were terminated, one (1.6%) ended due to fetal intrauterine death, and the other 15 (24.2%) continued to delivery (13 of term pregnancy, and two of preterm pregnancy). Autopsies were performed on 26 out of the 46 terminated fetuses, and the results were consistent with the fetal echocardiography. Of the 15 newborns, one died due to extra-cardiac abnormality, and the other 14 (four underwent operation) remained well in development and heart function during follow-up until March, 2017.

The retrograde flow signal in the aortic arch is commonly seen in fetal cardiac structural and/or functional abnormality. Hemodynamic characteristics of the retrograde flow may vary depending on the etiology. Therefore, clinicians should pay attention to analyze the hemodynamics in combination with ultrasound findings to identify the etiology and to improve the accuracy of fetal echocardiography.

Fetal diseases; Aortic valve insufficiency; Hemodynamics