Objective: To determine the implications of a bidirectional Doppler flow pattern detected in one or both of the fetal great arteries in the first trimester.
Methods: Database records were reviewed for cases of bidirectional flow found on fetal echocardiography performed at less than 15 weeks of gestation between January 1999 and October 2006 inclusive. Bidirectional flow consisted of antegrade flow in systole and retrograde flow in diastole. Data including indication for fetal echocardiography, gestational age at diagnosis, the anatomical features, karyotype, nuchal translucency measurement and outcome were collected.
Results: From almost 2500 scans, bidirectional flow was detected in a total of 15 fetuses. The abnormal flow pattern was confined to the aorta in four, to the pulmonary artery in four, and was present in both great arteries in a further seven fetuses. Eight of the 15 fetuses had regurgitation at one or both atrioventricular valves. Additional cardiac abnormalities were detected by ultrasound in eight cases. Of the 13 cases for which the karyotype was known, 12 were abnormal and five of these had trisomy 18. None of the fetuses survived. There were two intrauterine deaths and 13 terminations of pregnancy.
Conclusion: Bidirectional flow in one or both great arteries is an unusual finding at the first-trimester scan and must be distinguished from the retrograde flow occurring only in systole in duct-dependent heart defects. It carries a poor prognosis, which is a consequence of both the high chance of underlying chromosomal abnormality and the hemodynamic compromise associated with severe arterial valve regurgitation.