Ultrasonographic Features and Clinical Significance of Fetal Isolated Redundant Foramen Ovale Flap

Abstract Background Little is known about the ultrasonographic features of fetal isolated redundant foramen ovale flap (RFOF). Additionally, false positive diagnosis of aortic coarctation (CoA) may be related to the presence of an RFOF. This study aimed to explore the ultrasonographic features of RFOF and its differential diagnosis with CoA. Methods This was a retrospective cohort study that included 54 fetuses: 15 with isolated RFOF, 9 with CoA, and 30 normal fetuses of matched gestational age. The correlations of foramen ovale flap diameter (FOFD)/left atrial diameter (LAD) with right atrial diameter (RAD)/LAD, right ventricular diameter (RVD)/left ventricular diameter (LVD), and pulmonary artery diameter (PAD)/aortic diameter (AoD) were analyzed, and a quadratic regression model was established. Differences in FOFD/LAD, RAD/LAD, RVD/LVD, PAD/AoD, and aortic isthmus diameter were compared among the three groups. Results (1) Noticeable RAD/LAD, RVD/LVD, and PAD/AoD increases, aortic arch dysplasia, and aortic isthmus narrowing were found in the RFOF group (all p < 0.05); ductus arteriosus aneurysm and premature atrial beats were also observed. (2) As the RFOF severity increased, the atrial and ventricular asymmetry and disproportion between the pulmonary artery and aorta became more pronounced (r = 0.825, 0.862, 0.846, all p < 0.001). (3) Other than the FOFD/LAD, no significant differences in the RAD/LAD, RVD/LVD, PAD/AoD, or aortic isthmus diameter were found between fetuses with an RFOF and fetuses with CoA (p > 0.05). Conclusions Isolated RFOF has specific ultrasound features, and the degree of disproportion between the left and right heart is consistent with the severity of RFOF. Measurement and calculation of FOFD/LAD may help distinguish between RFOF and CoA.