Reduced fetal cerebral oxygen consumption is associated with smaller brain size in fetuses with congenital heart disease.

Circulation: Clinical Summaries.

In the article “Reduced Fetal Cerebral Oxygen Consumption Is Associated With Smaller Brain Size in Fetuses With Congenital Heart Disease” by Sun et al,1 the authors state: “This study supports a direct link between reduced cerebral oxygenation and impaired brain growth in fetuses with CHD and raises the possibility that in utero brain development could be improved with maternal oxygen therapy.” I have a serious concern that this could lead to widespread introduction of chronic administration of oxygen to …

Neurodevelopmental impairments are common in congenital heart disease (CHD) and fetal brain volume is an important predictor of outcomes. Social determinants of health (SDOH) and environmental factors influence brain growth in other populations and likely play a neurodevelopmental role in CHD. This study evaluated the influence of SDOH and environmental factors on fetal and neonatal brain volume, growth, and risk of brain injury in CHD. This prospective single-center longitudinal cohort study enrolled fetuses with severe CHD to undergo third-trimester fetal and preoperative brain MRIs. Controls underwent third-trimester brain MRIs. Participants completed SDOH and environmental exposure surveys. Fetal and neonatal brain volumes, brain growth, and presence of white matter injury (WMI) were assessed. 57 CHD patients and 24 controls were enrolled, resulting in 33 fetal and 44 neonatal MRIs in the CHD group and 21 fetal control MRIs. Several SDOH and environmental factors, including maternal smoking, were associated with smaller brain volume and slower brain growth in CHD but not in controls. With CHD, repeated-measures analysis showed smaller fetal brain volume (coeff: - 13.3, 95% CI - 25.5, - 1.1, p = 0.03) and slower growth (coeff: - 2.5, 95% CI - 5.0, - 0.07, p = 0.04) with exposure to any risk factor. Patients with moderate to severe WMI had significantly lower mean COI scores compared to those with no or minimal WMI (58.28 vs. 37.28, p = 0.04), but lost significance when adjusted for GA. SDOH and environmental exposures influence fetal brain growth and preoperative brain injury risk in CHD. These results highlight additive environmental prenatal risks which may be amenable to early intervention.

BackgroundNeurodevelopmental impairments are common in congenital heart disease (CHD) and fetal brain volume is an important predictor of outcomes. Social determinants of health (SDOH) and environmental factors influence brain growth in other populations and likely play a neurodevelopmental role in CHD. This study evaluated the influence of SDOH and environmental factors on fetal and neonatal brain volume, growth, and risk of brain injury in CHD.MethodsThis prospective single-center longitudinal cohort study enrolled fetuses with severe CHD to undergo third-trimester fetal and preoperative brain MRIs. Controls underwent third-trimester brain MRIs. Participants completed SDOH and environmental exposure surveys. Fetal and neonatal brain volumes, brain growth, and presence of white matter injury (WMI) were assessed.Results57 CHD patients and 24 controls were enrolled, resulting in 33 fetal and 44 neonatal MRIs in the CHD group and 21 fetal control MRIs. Several SDOH and environmental factors, including maternal smoking, were associated with smaller brain volume and slower brain growth in CHD but not in controls. With CHD, repeated-measures analysis showed smaller fetal brain volume (coeff: −13.3, 95%CI: −25.5,−1.1 p = 0.03) and slower growth (coeff: −2.5, 95%CI: −5.0, −0.07, p = 0.04) with exposure to any risk factor. CHD subjects from high Childhood Opportunity Index neighborhoods had lower odds of moderate to severe preoperative WMI (OR = 0.16, 95%CI: 0.03, 0.9, p = 0.04).ConclusionsSDOH and environmental exposures influence fetal brain growth and preoperative brain injury risk in CHD. These results highlight additive environmental prenatal risks which may be amenable to early intervention.

Neurodevelopmental impairment is common in children with congenital heart disease (CHD), but postnatal variables explain only 30% of the variance in outcomes. To explore whether the antecedents for neurodevelopmental disabilities might begin in utero, we analyzed whether fetal brain volume predicted subsequent neurodevelopmental outcome in children with CHD. Fetuses with isolated CHD and sociodemographically comparable healthy control fetuses underwent fetal brain magnetic resonance imaging and 2-year neurodevelopmental evaluation with the Bayley Scales of Infant and Toddler Development, Third Edition (Bayley-III) and the Adaptive Behavior Assessment System, Third Edition (ABAS-3). Hierarchical regression evaluated potential predictors of Bayley-III and ABAS-3 outcomes in the CHD group, including fetal total brain volume adjusted for gestational age and sex, sociodemographic characteristics, birth measures, and medical history. The CHD group (n=52) had lower Bayley-III cognitive, language, and motor scores than the control group (n=26), but fetal brain volumes were similar. Within the CHD group, larger fetal total brain volume correlated with higher Bayley-III cognitive, language, and motor scores and ABAS-3 adaptive functioning scores (r=0.32-0.47; all P<0.05), but this was not noted in the control group. Fetal brain volume predicted 10% to 21% of the variance in neurodevelopmental outcome measures in univariate analyses. Multivariable models that also included social class and postnatal factors explained 18% to 45% of the variance in outcome, depending on developmental domain. Moreover, in final multivariable models, fetal brain volume was the most consistent predictor of neurodevelopmental outcome across domains. Small fetal brain volume is a strong independent predictor of 2-year neurodevelopmental outcomes and may be an important imaging biomarker of future neurodevelopmental risk in CHD. Future studies are needed to support this hypothesis. Our findings support inclusion of fetal brain volume in risk stratification models and as a possible outcome in fetal neuroprotective intervention studies.

Introduction: Fetuses with complex congenital heart disease (CHD) are at high risk for impaired brain development. However, the relationship between altered fetal brain development and infant neurobehavioral outcomes in CHD remains largely unknown. Hypothesis: We hypothesized that impaired fetal brain volumetric growth and cortical folding in CHD would predict impaired infant neurodevelopment. Methods: We prospectively recruited women with pregnancies complicated by a fetal CHD diagnosis. Women underwent a fetal MRI on a GE 1.5T scanner. Volumes of fetal total brain, cortical gray matter, white matter, deep gray matter, cerebellum, and brainstem were quantified. Cortical folding included local gyrification index, sulcal depth, and surface area. We completed Bayley Scales of Infant and Toddler Development III and Infant-Toddler Social and Emotional Assessment at 18 months. Generalized estimating equations were used to measure associations between fetal brain measures and infant neurodevelopment outcomes. Results: We enrolled 186 mother/baby dyads who underwent 250 MRIs between 20-39 gestational weeks. Seventy-seven had single-ventricle (SV) CHD and 109 had two-ventricle (2V) CHD. Forty-nine subjects died and 133 infants underwent neurodevelopment testing at a mean age of 19.6 months. Decreased fetal brain volumes and delayed cortical folding (all p&lt;0.05) were associated with poorer infant cognitive outcomes. Impairments in fetal cerebellum (p=0.004), cortical (p=0.05) and deep gray matter (p=0.03) volumes, and cortical folding measures (all p&lt;0.01) were associated with language delays. Reduced prenatal cortical gray matter volume (p=0.008), gyrification (p=0.02), and surface area (p=0.05) were associated with motor delays. Infants with SV CHD had lower competence scores compared to 2V CHD. Conclusions: We report that impairments in fetal brain growth and cortical folding predict adverse cognitive, language and motor outcomes in CHD. Infants with SV CHD showed greater susceptibility to social-emotional problems compared to those with 2V CHD. These data suggest that impaired prenatal regional brain growth disturbances and delayed cerebral cortical development are important biomarkers for later neurobehavioral dysfunction.

In a postasphyxia neonatal lamb model, the responses of the cerebral circulation to hypoxic hypoxia and changes in systemic arterial blood pressure were examined. Ventilated newborn lambs (n = 14) were subjected to a gradual asphyxial insult, resuscitated, and returned to control ventilator settings. During the time 2-5 hours after asphyxia, the responses of cerebral blood flow (CBF), cerebral oxygen delivery (OD), cerebral oxygen consumption (CMRO2), and cerebral fractional oxygen extraction (E) to changes in either arterial oxygen content (CaO2) or mean arterial blood pressure (MAP) were assessed. These data were compared with measurements from nonasphyxiated lambs (n = 7). With hypoxia (n = 7), cerebral blood flow increased (CBF = 646/CaO2 + 44) compared with nonasphyxiated lambs (CBF = 1121/CaO2 + 11). In asphyxiated lambs, cerebral oxygen delivery decreased (OD = 0.41 CaO2 + 6.87), but cerebral oxygen consumption remained stable due to a proportional increase in cerebral fractional oxygen extraction (E = -0.014 CaO2 + 0.65). In nonasphyxiated lambs, cerebral oxygen delivery, consumption, and fractional extraction were unchanged with hypoxia. In response to alterations in blood pressure, both cerebral blood flow (CBF = 0.84 MAP + 6.62) and oxygen delivery (OD = 0.13 MAP + 0.77) were pressure-passive. With hypotension, cerebral fractional oxygen extraction increased (E = -0.003 MAP + 0.69) but not enough to prevent a decrease in cerebral oxygen consumption (CMRO2 = 0.042 MAP + 1.79). In nonasphyxiated lambs, cerebral blood flow, oxygen delivery, consumption, and fractional extraction did not vary with blood pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

In this study, we examined the cerebral oxygenation effects of two methods of pharmacologic burst suppression during cardiopulmonary bypass (CPB) in valvular heart surgery patients. Patients were randomly entered into one of three groups: control (n = 13, fentanyl and midazolam), control plus burst suppression doses of thiopental (n = 15), or control plus burst suppression doses of isoflurane (n = 16). Burst suppression (80% suppression) was accomplished in the thiopental and isoflurane groups 15 min before aortic cannulation and was maintained through aortic decannulation. Cerebral physiologic measurements were made during hypothermia (27-28 degrees C) and on rewarming to 36 degrees C. During hypothermia, burst suppression produced significant (P < 0.005) differences with regard to cerebral vascular resistance (P = 0.003), cerebral arterial venous oxygen difference [C(a-v)O2] (P = 0.032), cerebral blood flow (CBF) (P = 0.009), and cerebral oxygen delivery (P = 0.027). There was a similar pattern on rewarming, with groups differing significantly (P < 0.05) with respect to CBF (P = 0.016), cerebral vascular resistance (P = 0.008), oxygen delivery (P = 0.004), C(a-v)O2 (P = 0.043), and cerebral oxygen extraction (P = 0.046). Rewarming rates were similar among groups. There was no difference in neurologic outcome or requirement for inotropic support among groups. The time to awakening was increased (P = 0.0005) in the thiopental group. The thiopental group had lower cerebral oxygen delivery, but not lower cerebral metabolic rate of oxygen consumption, compared with the control group, resulting in widening C(a-v)O2 during CPB. This lack of coupling of oxygen delivery and consumption suggests that pharmacologic neuroprotective mechanisms are complex and involve more than an improvement in the ratio of global cerebral oxygen supply to demand. This study demonstrates that the balance of cerebral oxygen delivery to consumption during cardiopulmonary bypass is altered differently by thiopental and isoflurane. As others have noted, it seems that cerebral protection is more complex than a simple improvement in the balance of oxygen delivery and consumption.

The first week of postnatal life is a period of transition for both pulmonary and systemic vascular flow patterns. Owing to associated shunts and altered systemic/pulmonary blood flow, neonates with congenital heart defect (CHD) are at particular risk for disrupted end-organ perfusion and oxygen delivery, including that of the brain. Near-infrared spectroscopy (NIRS) measures venous-weighted cerebral oxygen saturation (CSat) at the frontal cortex, serving as an indirect reflection of cerebral blood flow. CSat is impacted by factors such as tissue perfusion, systemic oxygenation, regional oxygen extraction and haemoglobin levels, all of which are affected by cardiac function and vascular supply [1, 2]. Cerebral fractional tissue oxygen extraction (cFTOE) reflects the balance between cerebral oxygen utilisation and oxygen delivery, and it is operationally defined as (preductal SpO2—CSat)/preductal SpO2. As such, cFTOE can provide insight into cerebral oxygen utilisation. Increased cFTOE can be due to decreased oxygen delivery or increased oxygen consumption not met by associated increase in delivery. Likewise, decreased cFTOE can indicate that the brain is using less oxygen or that oxygen delivery has increased relative to utilisation [3]. Data on CSat and cFTOE as cerebrovascular metrics in neonates with CHD during the period of postnatal adaptation are limited. Elements of anterior cerebral artery (ACA) Doppler such as resistive index (RI) and pulsatility index (PI) assess vascular resistance and flow characteristics in the frontal cortex and have been shown to correspond to cerebral perfusion pressure [4]. Abnormal RI is a recognised indicator of such newborn pathologies as increased intracranial pressure, brain injury and diastolic steal [5-7]. This study has made a notable contribution to the literature by applying these established bedside tools to a vulnerable and complex group of patients (neonates with CHD) during a time of critical transitional physiology (postnatal adaptation). The authors recruited 34 neonates with various types of CHD and analysed 142 concomitant data measurements of NIRS and daily ultrasound Doppler over the first 7 days of life. They used mixed-effects models to evaluate the relationship between CSat/cFTOE and RI/PI-ACA, adjusting for time since birth, pCO2 and haemoglobin levels. The authors found a decline in CSat and rise in cFTOE throughout the first week of life in neonates with CHD, which aligns with findings from prior research [8]. RI and PI both increased over the time period, indicating increased resistance to flow velocities. The authors also reported statistically significant associations between CSat/cFTOE and simultaneous RI/PI values. The findings suggest a progressive increase in oxygen extraction, possibly related to diminished blood flow, impaired oxygen delivery or increased metabolic demand during postnatal transition. The authors theorise that this may be partly owing to altered adaptation due to shunts and abnormal anatomy. Despite the variability of the study population, the findings supported consistent directional trends in NIRS and ultrasound. While these results are meaningful, an even greater impact will be gained in translating the findings to earlier detection/management of cerebral hypoperfusion in order to improve neurodevelopmental outcomes. URL LINK: https://ebneo.org/ebneo-commentary-cerebral-saturation-and-fractional-tissue-oxygen-extraction-and-anterior-cerebral-artery-doppler. Ashley L. Lynch: conceptualization, writing – original draft. Ethan L. Gillett: writing – review and editing. The authors have nothing to report. The authors declare no conflicts of interest. Data sharing not applicable to this article as no datasets were generated or analysed during the current study.

We are grateful to Dr Rudolph for his careful review of our article. Dr Rudolph’s extensive work on the fetal lamb circulation was the principle reference for our research. In our article, we present MRI data showing how the obstructions to flow and abnormal connections that characterize various congenital cardiac malformations result in desaturation of ascending aortic blood because of failure of the normal preferential streaming of umbilical venous blood.1 In addition, we observed reductions in umbilical venous Sao2, and in fetuses with single ventricle physiology, reductions in umbilical blood flow resulting in further desaturation across the fetal circulation. The majority of fetuses with heart disease showed no evidence of increased cerebral blood flow or cerebral oxygen extraction to compensate for the hypoxemia, resulting in a trend toward reduced cerebral oxygen delivery (CDo2) and a significant reduction in cerebral oxygen consumption. In a more recent analysis with …

Cerebral blood flow (CBF) is known to be low in newborn infants, but this has not been shown to be damaging. The purpose of this study was to investigate the relationships between cerebral haemoglobin flow, blood flow, oxygen delivery, oxygen consumption, venous saturation, and fractional oxygen extraction (OEF) in newborn, preterm infants. Measurements were made by near-infrared spectroscopy in 13 very preterm, extremely low birth weight infants (median gestation 25 weeks) during the first 3 days after birth. There was a negative correlation between cerebral oxygen delivery and OEF (n=13, r=-0.5, P=0.03), which implies that when there is a reduction in cerebral oxygen delivery in sick preterm infants, increased cerebral oxygen extraction may be responsible for maintaining oxygen availability to the brain. During the first 3 days after birth CBF (n=13, r=0.7, P=0.01), oxygen delivery (n=13, r=0.5, P=0.03), and oxygen consumption (n=13, r=0.7, P=0.004) all increased. This increase in oxygen consumption indicates increased cerebral metabolic activity after birth, which is likely to be a normal adaptation to extrauterine life. The increases in blood flow and oxygen delivery may also be normal adaptations that facilitate this increase in metabolic activity. There was a decrease (P=0.04) in mean (+/-s.d.) cerebral OEF between day 1 (0.37+/-0.10) and day 2 (0.29+/-0.09), with no change between day 2 and day 3. Taking into account the negative correlation between OEF and oxygen delivery, this decrease in OEF may be because of increased oxygen delivery during this time.

Perinatal inflammation is associated with adverse neurodevelopmental outcomes, which may be partly due to changes in the cerebral oxygen delivery/consumption relationship. We aimed to determine the critical oxygen delivery threshold of the brain of preterm, ventilated lambs and to determine whether the critical threshold is affected by exposure to inflammation in utero. Pregnant ewes received intra-amniotic injection of lipopolysaccharide or saline at 125 or 127 days of gestation. Pulmonary and systemic flow probes and catheters were surgically positioned in the fetus immediately before delivery at 129 days of gestation. After delivery, lambs were ventilated for 90 min using a positive end-expiratory pressure recruitment strategy. Cardio-respiratory variables and blood gases were measured regularly. Systemic and cerebral oxygen delivery, consumption (Fick), and extraction were calculated, and the relationship between cerebral delivery and consumption analyzed. Linear regression was used to define the transition or "critical" oxygen threshold as the point at which the slope of the oxygen delivery/consumption curve changed to be > 10°. Four subgroups were defined according to the calculated critical threshold. A total of 150 measurements were recorded in 18 lambs. Fetal cerebral oxygen consumption was increased by antenatal lipopolysaccharide (P < 0.05). The postnatal critical oxygen threshold was 3.6 ml·kg⁻¹·min⁻¹, corresponding to cerebral oxygen consumption of 0.73 ml·kg⁻¹·min⁻¹. High oxygen delivery and consumption were associated with increased pulmonary and carotid blood flow and systemic extraction compared with low oxygen delivery and consumption. No postnatal effect of antenatal inflammation was observed. Inflammation in utero increases fetal, but not postnatal, cerebral oxygen consumption. Adverse alterations to pulmonary blood flow can result in reduced cerebral blood flow, oxygen delivery, and consumption. Regardless of exposure to inflammation, there is a consistent postnatal relationship between cerebral oxygen delivery and consumption.

Fetuses and neonates with critical congenital heart disease are at risk of delayed brain development and neurodevelopmental impairments. Our aim was to investigate the association between fetal and neonatal brain volumes and neonatal brain injury in a longitudinally scanned cohort with an antenatal diagnosis of critical congenital heart disease and to relate fetal and neonatal brain volumes to postmenstrual age and type of congenital heart disease. This was a prospective, longitudinal study including 61 neonates with critical congenital heart disease undergoing surgery with cardiopulmonary bypass <30 days after birth and MR imaging of the brain; antenatally (33 weeks postmenstrual age), neonatal preoperatively (first week), and postoperatively (7 days postoperatively). Twenty-six had 3 MR imaging scans; 61 had at least 1 fetal and/or neonatal MR imaging scan. Volumes (cubic centimeters) were calculated for total brain volume, unmyelinated white matter, cortical gray matter, cerebellum, extracerebral CSF, and ventricular CSF. MR images were reviewed for ischemic brain injury. Total fetal brain volume, cortical gray matter, and unmyelinated white matter positively correlated with preoperative neonatal total brain volume, cortical gray matter, and unmyelinated white matter (r = 0.5-0.58); fetal ventricular CSF and extracerebral CSF correlated with neonatal ventricular CSF and extracerebral CSF (r = 0.64 and 0.82). Fetal cortical gray matter, unmyelinated white matter, and the cerebellum were negatively correlated with neonatal ischemic injury (r = -0.46 to -0.41); fetal extracerebral CSF and ventricular CSF were positively correlated with neonatal ischemic injury (r = 0.40 and 0.23). Unmyelinated white matter:total brain volume ratio decreased with increasing postmenstrual age, with a parallel increase of cortical gray matter:total brain volume and cerebellum:total brain volume. Fetal ventricular CSF:intracranial volume and extracerebral CSF:intracranial volume ratios decreased with increasing postmenstrual age; however, neonatal ventricular CSF:intracranial volume and extracerebral CSF:intracranial volume ratios increased with postmenstrual age. This study reveals that fetal brain volumes relate to neonatal brain volumes in critical congenital heart disease, with a negative correlation between fetal brain volumes and neonatal ischemic injury. Fetal brain imaging has the potential to provide early neurologic biomarkers.

The path forward is to look backward in time: fetal physiology: the new frontier in managing infants with congenital heart defects.

Introduction: Newer research has highlighted significant neurological impairments in children and adults with congenital heart disease (CHD). The more severe the heart defect, the higher the neurologic impairment. Pregnancies complicated by fetal or maternal CHD carry a higher risk of placental abnormalities. We studied the association between pregnancy hormonal levels and fetal head and body growth. Hypothesis: Placental dysfunction in pregnancies with fetal or maternal CHD alters pregnancy hormonal levels affecting fetal brain and somatic growth. Methods: We performed a retrospective case-control study on pregnant women (year 2010-2019) at the University of Iowa. Only women with first and/or second trimester prenatal screening (ultrasound and blood test) were included. Pregnancies with fetal chromosomal abnormalities, multiple gestation, maternal diabetes, smoking, or hypertension were excluded. Pregnancies were either healthy controls (n=36), women with CHD (MCHD; n=26), or fetus with CHD (FCHD; n=23). Pregnancy hormonal levels, ultrasound findings, and fetal/neonatal growth percentiles and/or z-scores data were analyzed. Results: Women with CHD were younger (p=0.004) with increased fetal nuchal translucency (p=0.003) compared to controls. Women in MCHD (p=0.02) and FCHD (p=0.02) group delivered earlier than controls. FCHD had significantly lower pregnancy associated plasma protein-A (PAPP-A) levels than controls (p=0.04). The groups had no difference in the second trimester fetal head circumference (HC) and femur length. FCHD group had significantly smaller HC percentile (p=0.03) and z-scores (p=0.03) at birth than controls. Both FCHD and MCHD had smaller birth weight and length compared to controls. However, only FCHD group demonstrated significantly lower HC to birth weight ratio (p=0.01). The controls had a positive correlation between human chorionic gonadotropin level and head circumference z-score at birth (r=0.34;p=0.053). Conclusions: Pregnant women with CHD have increased fetal nuchal translucency and deliver at earlier gestational age. Women with fetal CHD have smaller neonatal head and body size at birth with associated low PAPP-A level early in their pregnancy probably related to placental dysfunction.