Impact of Maternal Hyperoxygenation on Myocardial Deformation and Loading Conditions in Fetuses with and without Left Heart Hypoplasia.

BACKGROUND: Maternal hyperoxygenation (MHO) is used in a variety of clinical applications, but its impact on fetal cardiovascular physiology is poorly understood. Our aims were to describe the effects of MHO on myocardial deformation parameters and on ultrasound-based metrics of preload and afterload and to assess the differential effect of MHO on fetuses with left heart hypoplasia (LHH). We hypothesized that the effects of MHO would be modulated by loading conditions and that fetuses with LHH would be more sensitive to changes in preload and afterload induced by MHO. METHODS: We performed a post hoc analysis of 36 fetal echocardiograms performed as part of a pilot study of MHO in LHH (n = 9) and control (n = 9) fetuses. Oxygen was administered via 8 L face mask for 10 minutes. Right ventricular (RV) and left ventricular (LV) longitudinal strain and strain rate, estimated aortic and pulmonary cardiac output, pulmonary vein velocity-time integral (VTI) and pulsatility indices (PI) of the middle cerebral artery (MCA), pulmonary arteries (PA), and umbilical artery (UA) were measured at three time points: baseline, during MHO, and 10 minutes after removal of MHO. RESULTS: Maternal hyperoxygenation induced decreases in LV strain and strain rate and increases in RV strain and strain rate. Pulmonary artery PI decreased and pulmonary vein VTI increased, suggesting decreased pulmonary vascular resistance and increased pulmonary venous return. Most findings did not return to baseline after removal of MHO. We found no significant effect of MHO on MCA or UA PI. Left heart hypoplasia cases demonstrated similar effects of MHO in control cases, with larger changes in pulmonary vein VTI and LV strain rate. CONCLUSION: The effects of MHO on LV and RV mechanics suggest that changes in deformation indices may be explained by increases in LV preload and decreases in RV afterload. The time period for recovery of fetal hemodynamics from MHO is ill-defined.

Right Ventricular Global Longitudinal Strain in Fetuses with Hypoplastic Left Heart Syndrome Does Not Differ Between Those With and Without Genetic Conditions.

The presence of a genetic condition is a risk factor for increased mortality in hypoplastic left heart syndrome (HLHS). Speckle tracking strain analysis in interstage echocardiograms have shown promise in identifying patients with HLHS at increased risk of mortality. We hypothesized that fetuses with a genetic condition and HLHS have impaired right ventricular global longitudinal strain compared with fetuses with HLHS and no evident genetic condition. We performed a retrospective analysis of 60 patients diagnosed in fetal life with HLHS from 11/2015 to 11/2019. We evaluated presenting echocardiograms and calculated right ventricular global longitudinal strain (RV GLS) and fractional area of change (FAC) using post-processing software. We first compared RV GLS and FAC between those with genetic conditions to those without. We examined the secondary outcome of mortality among those with and without genetic conditions and among HLHS subgroups. Of the 60 patients with available genetic testing, 11 (18%) had an identified genetic condition. Neither RV GLS nor FAC was significantly different between patients with and without genetic conditions. There was no difference in RV GLS or FAC among HLHS phenotype or those who died or survived as infants. However, patients with a genetic syndrome had increased neonatal and overall mortality. In this cohort, RV GLS did not differ between those with and without a genetic diagnosis, among HLHS phenotypes, or between those surviving and dying as infants. Further analysis of strain throughout gestation and after birth could provide insight into the developing heart in fetuses with HLHS.

Chronic Maternal Hyperoxygenation and Effect on Cerebral and Placental Vasoregulation and Neurodevelopment in Fetuses with Left Heart Hypoplasia.

INTRODUCTION: In a pilot study of chronic maternal hyperoxygenation (CMH) in left heart hypoplasia (LHH), we sought to determine effect estimates of CMH on head size, vascular resistance indices, and neurodevelopment compared to controls. MATERIAL AND METHODS: Nine gravidae meeting the inclusion criteria (fetal LHH, ≥25.9 weeks' gestation, and ≥10% increase in percent aortic flow after acute hyperoxygenation) were prospectively enrolled. Controls were 9 contemporary gravidae with fetal LHH without CMH. Brain growth and Doppler-derived estimates of fetal cerebrovascular and placental resistance were blindly evaluated and compared using longitudinal regression. Postnatal anthropomorphic and neurodevelopmental assessments were compared. RESULTS: There was no difference in baseline fetal measures between groups. There was significantly slower biparietal diameter (BPD) growth in the CMH group (z-score change -0.03 ± 0.02 vs. +0.09 ± 0.05 units/week, p = 0.02). At 6 months postnatal age, the mean head circumference z-score in the CMH group was smaller than that of controls (-0.20 ± 0.58 vs. +0.85 ± 1.11, p = 0.048). There were no differences in neurodevelopmental testing at 6 and 12 months. DISCUSSION: In this pilot study, relatively diminished fetal BPD growth and smaller infant head circumference z-scores at 6 months were noted with in utero CMH exposure.