Fetal Cerebral Vascular Response to Maternal Hyperoxia in Congenital Heart Disease: Effects of Cardiac Physiology.

OBJECTIVES: Fetal cerebral vascular resistance is influenced by several factors in the setting of intact autoregulation to allow for normal cerebral blood flow and oxygenation. Maternal hyperoxia (MH) testing allows for acute alterations in fetal physiology and can be a tool to test cerebral vascular reactivity in late gestation fetuses. We utilized MH testing to evaluate cerebral vascular reactivity in fetuses with specific congenital heart disease (CHD). METHODS: This cross-sectional study compares fetuses with complex CHD to controls without CHD. CHD cases were grouped by physiology: left-sided obstructive lesion (LSOL), right-sided obstructive lesion (RSOL), and d-transposition of the great arteries (d-TGA). Subjects underwent MH testing during the 3(rd) trimester fetal echocardiogram. The pulsatility index (PI) was calculated for the middle cerebral artery (MCA), umbilical artery (UA) and branch pulmonary artery (PA). Comparisons were made between each CHD group and the control group at baseline and following MH. RESULTS: 60 pregnant women enrolled (CHD, n= 43; Control, n= 17). There were 27 fetuses with LSOL, 7 with RSOL and 9 with d-TGA. Mean gestational age was 33.9 weeks (95% CI: 33.6-34.2). At baseline, the MCA PI Z-score was lowest in the LSOL group (-1.8, 95% CI: -2.4, -1.2) compared with the control group (-0.8, 95% CI: -1.3, 0.3). In response to MH, the MCA PI Z-score increased significantly in the control and d-TGA groups but remained unchanged in the LSOL group and declined in the RSOL group. The change in MCA PI Z-score was significantly higher in the control group than the LSOL group (control= 0.9, 95% CI: 0.42, 1.4; LSOL= 0.12, 95% CI: -0.21, 0.45; p= 0.03). This difference was more pronounced in the LSOL subgroup with retrograde aortic arch flow. In all groups, the PA PI decreased at the same rate with MH and the UA PI was unchanged. CONCLUSIONS: The fetal cerebral vascular response to MH varies based on underlying CHD diagnosis, suggesting that cardiovascular physiology may influence autoregulatory capacities of the fetal brain. Further studies are needed to determine clinical implications of these findings on long-term neurodevelopment in these at-risk children. This article is protected by copyright. All rights reserved.