Fetal Cardiology

Cardiac hemodynamics in fetuses with transposition of the great arteries and intact ventricular septum from diagnosis to end of pregnancy: longitudinal follow-up. Lachaud M, Dionne A, Brassard M, Charron MA, Birca A, Dehaes M, Raboisson MJ. Ultrasound Obstet Gynecol. 2021 Feb;57(2):273-281. doi: 10.1002/uog.21920. PMID: 31710736   Take Home Points: Compared with normal fetuses, those with transposition of the great arteries and intact ventricular septum (TGA-IVS) undergo a complex redistribution of blood flow during the second half of pregnancy, with higher global pulmonary flow, lower ductal flow (with negative diastolic flow at the end of pregnancy) and a smaller foramen Ovale. In addition, fetal cardiac hemodynamic anomalies observed at 28–32 weeks’ gestation was associated with lower postnatal transcutaneous oxygen saturation. TGA-IVS neonates with TcSO2 < 65% had lower fetal left ventricular output, higher diastolic ductal retrograde flow, and smaller foramen Ovale at 28–32 weeks, compared with fetal values in those with postnatal TcSO2 ≥ 65%.   Commentary from Dr. Manoj Gupta (New York, USA), section editor of Pediatric & Fetal Cardiology Journal Watch:   Introduction: This was a retrospective longitudinal cohort study including fetuses that were diagnosed with TGA-IVS between January 2010 and March 2018. Fetuses with TGA-IVS had an echocardiogram at the time of diagnosis and were followed up with appointments at 28–32 and 35–38 weeks’ gestation. Echocardiography examinations were classified into three gestational-age groups: 18–22 weeks (mid gestation), 28–32 weeks (end of second trimester and beginning of third trimester) and 35–38 weeks (end of gestation). Therefore, a total of 133 echocardiograms were used for analysis and included 24 examinations at 18–22 weeks, 58 at 28–32 weeks and 51 at 35–38 weeks.     Methods: Aortic and pulmonary outputs were derived from the formula: Q = TVI × (π × D2/4) × HR, where Q is the output, D is the aortic or pulmonary valve diameter, TVI is the time-velocity integral and HR is the simultaneous heart rate (beats per min). Ductal flow Doppler flow at the ductal level (QDA) was measured on a sagittal view of the fetus. Antegrade and retrograde QDA were calculated. (for details please review the article)   Figure 3 Schematic representation of fetal circulation in transposition of the great arteries and intact ventricular septum physiology, with formulae describing two quantities: global systemic output (QGS), which was equal to right ventricular output (QRV) plus ductal output (QDA), and global pulmonary output (QGP), which was equal to left ventricular output (QLV) minus ductal flow (QDA). LA, left atrium; LV, left ventricle; RA, right atrium; RV, right ventricle.   Foramen Ovale diameter: The diameter of the foramen Ovale was measured in a horizontal, vertical, or oblique four-chamber view, at the end of ventricular systole, on the frames before atrioventricular valve opening. Fetal echocardiographic parameters in fetuses with TGA-IVS were compared between those with postnatal TcSO2 <65% and those with postnatal TcSO2 ≥65%.   Results: GCO (global cardiac output) was significantly greater in fetuses with TGA-IVS than in controls throughout pregnancy, the largest difference occurring at 35–38 weeks. At every timepoint, QLV as a percentage of GCO was significantly higher in fetuses with TGA-IVS than in controls, while QRV as a percentage of GCO was significantly lower. QDA (Ductus arteriosus cardiac output flow) was significantly lower in fetuses with TGA-IVS than in controls at every timepoint, with the difference increasing considerably after 28–32 weeks. Foramen Ovale diameter: The diameter of the foramen Ovale was significantly larger in fetuses with TGA-IVS than in controls at 18–22weeks, it was significantly lower later in pregnancy. Fetuses with TGA-IVS showed no significant increase in the size of the foramen Ovale after 28weeks, while it increased in normal controls.     Throughout pregnancy, the diameter of the foramen Ovale in patients with postnatal TcSO2 <65% was significantly lower than that in patients with postnatal TcSO2 ≥65%. At 28–32 weeks, ductal flow in patients with postnatal TcSO2 <65% was significantly lower than that in patients with postnatal TcSO2 ≥65%. At 28–32 and 35–38weeks, ductal diastolic flow and ductal diastolic ratio were significantly lower in patients with postnatal TcSO2 <65% than in those with postnatal TcSO2 ≥65%   Discussion: In fetuses with TGA-IVS, a smaller foramen Ovale was associated postnatally with preductal TcSO2 < 65%. At 28–32 weeks, these fetuses had lower ductal flow and lower ductal flow ratio. As opposed to the foramen Ovale, which may be challenging to measure, the diastolic ductal flow ratio is easy to obtain and should be evaluated in further studies as a risk factor for postnatal hypoxia.   Conclusions: Most of the observed hemodynamic changes in fetuses with TGA-IVS occurred as early as 18–22 weeks’ gestation. Chronic increased pulmonary flow is associated with decreased antegrade flow through the ductus arteriosus, expressed as the diastolic ductal ratio, and stagnation in the increase in the diameter of the foramen Ovale after 28–32 weeks. A smaller foramen Ovale, negative diastolic flow and a lower diastolic ductal ratio at 28–32 weeks and 35–38 weeks are risks factors for postnatal TcSO2 < 65%.