Prenatal ultrasonographic characteristics and prognosis of isolated redundant foramen ovale flap

Objective:To analyze the prenatal ultrasonographic characteristics and prognosis of the isolated redundant foramen ovale flap(RFOF).Methods:From January 2014 to December 2021,we collected data on fetal echocardiography analyses and perinatal outcomes for fetuses with isolated RFOF in Peking University People's Hospital.Results:We found that 0.31%(87/28308)of participants have RFOF.The four-chamber results of the foramen ovale flap(FOF)showed that it was stiff and extended>50%or reached the lateral wall of the left atrium(LA)in diastole.As seen from the foramen ovale(FO)channel and four-chamber views,the hypermobile and redundant flap were observed shrinking and stretching with the fetal cardiac cycle,which is similar to jellyfish.The lateral displacement of flow from LA to the left ventricle(LV)around the FOF on color doppler demonstrated thin linear blood flow from the right to left and a reversal of flow across FO.A uniphasic,but not biphasic,pattern of FOF displacement was observed on M-mode.Stages I(23/87)and II(51/87)had a higher ratio of ventricular disproportion than Stage 0(11/87)and III(2/87).We observed the RA/LA(right/left atrium)>1.2 in 53 cases(60.9%),RV/LV(right/left ventricle)>1.2 in 53 cases(60.9%),PA/AO(pulmonary/aortic artery)>1.2 in 53 cases(60.9%),and moderate or severe tricuspid regurgitation in 10 cases and moderate pericardial effusion in 2 cases(2.2%).Seventy-four RFOF cases had follow-up data.Neonatal death occurred in 2 cases;72 fetuses survived with normal or minor heart defects.Conclusion:RFOF should be considered if the left side of the heart of a fetus is smaller and related to hypermobile FOF.For isolated RFOF cases,a monthly follow-up is recommended to monitor arrhythmia or fetal hydrop status.Prompt treatment is recommended for those with adequate gestational age and lung maturity.