Mid-gestational fetal placental blood flow is diminished in the fetus with congenital heart disease

Interdependence of placenta and fetal cardiac development

The placenta and fetal heart undergo development concurrently during early pregnancy, and, while human studies have reported associations between placental abnormalities and congenital heart disease (CHD), the nature of this relationship remains incompletely understood. Evidence from animal studies suggests a plausible cause and effect connection between placental abnormalities and fetal CHD. Biomechanical models demonstrate the influence of mechanical forces on cardiac development, whereas genetic models highlight the role of confined placental mutations that can cause some forms of CHD. Similar definitive studies in humans are lacking; however, placental pathologies such as maternal and fetal vascular malperfusion and chronic deciduitis are frequently observed in pregnancies complicated by CHD. Moreover, maternal conditions such as diabetes and pre-eclampsia, which affect placental function, are associated with increased risk of CHD in offspring. Bridging the gap between animal models and human studies is crucial to understanding how placental abnormalities may contribute to human fetal CHD. The next steps will require new methodologies and multidisciplinary approaches combining innovative imaging modalities, comprehensive genomic testing, and histopathology. These studies may eventually lead to preventative strategies for some forms of CHD by targeting placental influences on fetal heart development.

Model-Informed Vancomycin Dosing Optimization to Address Delayed Renal Maturation in Infants and Young Children with Critical Congenital Heart Disease

Ensuring safe and effective drug therapy in infants and young children often requires accounting for growth and organ development; however, data on organ function maturation are scarce for special populations, such as infants with congenital diseases. Children with critical congenital heart disease (CCHD) often require multiple staged surgeries depending on their age and disease severity. Vancomycin (VCM) is used to treat postoperative infections; however, the standard pediatric dose (60-80 mg/kg/day) frequently results in overexposure in children with CCHD. In this study, we characterized the maturation of VCM clearance in pediatric patients with CCHD and determined the appropriate dosing regimen using population pharmacokinetic (PK) modeling and simulations. We analyzed 1,254 VCM serum concentrations from 152 postoperative patients (3 days-13 years old) for population PK analysis. The PK model was developed using a two-compartment model with allometrically scaled body weight, estimated glomerular filtration rate (eGFR), and postmenstrual age as covariates. The observed clearance in patients aged ≤ 1 year and 1-2 years was 33% and 40% lower compared with that of non-CCHD patients, respectively, indicating delayed renal maturation in patients with CCHD. Simulation analyses suggested VCM doses of 25 mg/kg/day (age ≤ 3 months, eGFR 40 mL/min/1.73 m2 ) and 35 mg/kg/day (3 months < age ≤ 3 years, eGFR 60 mL/min/1.73 m2 ). In conclusion, this study revealed delayed renal maturation in children with CCHD, could be due to cyanosis and low cardiac output. Model-informed simulations identified the lower VCM doses for children with CCHD compared with standard pediatric guidelines.

Shared developmental pathways of the placenta and fetal heart

Congenital heart defects (CHD) remain the most common class of birth defect worldwide, affecting 1 in every 110 live births. A host of clinical and morphological indicators of placental dysfunction are observed in pregnancies complicated by fetal CHD and, with the recent emergence of single-cell sequencing capabilities, the molecular and physiological associations between the embryonic heart and developing placenta are increasingly evident. In CHD pregnancies, a hostile intrauterine environment may negatively influence and alter fetal development. Placental maldevelopment and dysfunction creates this hostile in-utero environment and may manifest in the development of various subtypes of CHD, with downstream perfusion and flow-related alterations leading to yet further disruption in placental structure and function. The adverse in-utero environment of CHD-complicated pregnancies is well studied, however the specific etiological role that the placenta plays in CHD development remains unclear. Many mouse and rat models have been used to characterize the relationship between CHD and placental dysfunction, but these paradigms present substantial limitations in the assessment of both the heart and placenta. Improvements in non-invasive placental assessment can mitigate these limitations and drive human-specific investigation in relation to fetal and placental development. Here, we review the clinical, structural, and molecular relationships between CHD and placental dysfunction, the CHD subtype-dependence of these changes, and the future of Placenta-Heart axis modeling and investigation.

The Placenta in Congenital Heart Disease: Form, Function and Outcomes

The maternal-fetal environment, controlled and modulated by the placenta, plays a critical role in the development and well-being of the fetus, with long-term impact through programming of lifelong health. The fetal cardiovascular system and placenta emerge at the same time embryologically, and thus placental form and function are altered in the presence of congenital heart disease (CHD). In this review, we report on what is known about the placenta from a structural and functional perspective when there is CHD. We describe the various unique pathologic findings as well as the diagnostic imaging tools used to characterize placental function in utero. With growing interest in the placenta, a standardized approach to characterizing placental pathology has emerged. Furthermore, application of ultrasonography techniques and magnetic resonance imaging now allow for insights into placental blood flow and functionality in vivo. An improved understanding of the intriguing relationship between the placenta and the fetal cardiovascular system will provide opportunities to develop novel ways to optimize outcomes. Once better understood, therapeutic modulation of placental function offered during the vulnerable period of fetal plasticity may be one of the most impactful ways to alter the course of CHD and its complications.

Neuroplacentology in congenital heart disease: placental connections to neurodevelopmental outcomes

Children with congenital heart disease (CHD) are living longer due to effective medical and surgical management. However, the majority have neurodevelopmental delays or disorders. The role of the placenta in fetal brain development is unclear and is the focus of an emerging field known as neuroplacentology. In this review, we summarize neurodevelopmental outcomes in CHD and their brain imaging correlates both in utero and postnatally. We review differences in the structure and function of the placenta in pregnancies complicated by fetal CHD and introduce the concept of a placental inefficiency phenotype that occurs in severe forms of fetal CHD, characterized by a myriad of pathologies. We propose that in CHD placental dysfunction contributes to decreased fetal cerebral oxygen delivery resulting in poor brain growth, brain abnormalities, and impaired neurodevelopment. We conclude the review with key areas for future research in neuroplacentology in the fetal CHD population, including (1) differences in structure and function of the CHD placenta, (2) modifiable and nonmodifiable factors that impact the hemodynamic balance between placental and cerebral circulations, (3) interventions to improve placental function and protect brain development in utero, and (4) the role of genetic and epigenetic influences on the placenta-heart-brain connection. IMPACT: Neuroplacentology seeks to understand placental connections to fetal brain development. In fetuses with CHD, brain growth abnormalities begin in utero. Placental microstructure as well as perfusion and function are abnormal in fetal CHD.

Double Jeopardy: Prematurity and Congenital Heart Disease-What's Known and Why It's Important

This article is based on a composite of talks presented during the Double Jeopardy: Prematurity and Congenital Heart Disease Plenary Session at NeoHeart 2020, a global virtual conference.Prematurity and low weight remain significant risk factors for mortality after neonatal cardiac surgery despite a steady increase in survival. Newer and lower weight thresholds for operability are constantly generated as surgeons gather proficiency, technical mastery, and experience in performing complex procedures on extremely small infants. The relationship between birth weight and survival after cardiac surgery is nonlinear with 2 kilograms (kg) being an inflection point below which marked decline in survival occurs.The prevalence of congenital heart disease (CHD) in premature infants is more than twice that in term born infants. Increased risk of preterm birth in infants with CHD is most commonly due to spontaneous preterm birth and remains poorly understood.Advances in Neonatal-Perinatal medicine have led to a marked improvement in survival of neonates born prematurely over the last several decades. However, the risk of severe morbidities including retinopathy of prematurity, intraventricular hemorrhage, bronchopulmonary dysplasia and necrotizing enterocolitis remains significant in extremely low birth weight infants. Premature infants with CHD are at a greater risk of prematurity related morbidities than premature infants without CHD. Interventions that have been successful in decreasing the risk of these morbidities are addressed.

Abnormal Extracardiac Development in Fetuses With Congenital Heart Disease

BACKGROUND

Knowledge about extracardiac anomalies (ECA) in fetal congenital heart disease (CHD) can improve our understanding of the developmental origins of various outcomes in these infants. The prevalence and spectrum of ECA, including structural brain anomalies (SBA), on magnetic resonance imaging (MRI) in fetuses with different types of CHD and at different gestational ages, is unknown.

OBJECTIVES

The purpose of this study was to evaluate ECA rates and types on MRI in fetuses with different types of CHD and across gestation.

METHODS

A total of 429 consecutive fetuses with CHD and MRI between 17 and 38 gestational weeks were evaluated. ECA and SBA rates were assessed for each type of CHD and classified by gestational age (<25 or ≥25 weeks) at MRI.

RESULTS

Of all 429 fetuses with CHD, 243 (56.6%) had ECA on MRI, and 109 (25.4%) had SBA. Among the 191 fetuses with normal genetic testing results, the ECA rate was 54.5% and the SBA rate 19.4%. Besides SBA, extrafetal (21.2%) and urogenital anomalies (10.7%) were the most prevalent ECA on MRI in all types of CHD. Predominant SBA were anomalies of hindbrain-midbrain (11.0% of all CHD), dorsal prosencephalon (10.0%) development, and abnormal cerebrospinal fluid spaces (10.5%). There was no difference in the prevalence or pattern of ECA between early (<25 weeks; 45.7%) and late (≥25 weeks; 54.3%) fetal MRI.

CONCLUSIONS

ECA and SBA rates on fetal MRI are high across all types of CHD studied, and ECA as well as SBA are already present from midgestation onward.

Evaluation of umbilical venous flow volume measured using ultrasound compared to circuit flow volume in the EXTra-uterine Environment for Neonatal Development (EXTEND) system in fetal sheep

OBJECTIVE

To compare and validate umbilical venous flow volume (UVFV) measured at the intra-abdominal portion using ultrasound with actual flow volume of umbilical vein (UV) in fetal sheep sustained on the EXTrauterine Environment for Neonatal Development (EXTEND) system.

METHODS

Circuit flow volume through the oxygenator was obtained using sensors. Ultrasound derived UVFV (ml/min) was calculated as (UV diameter [cm]/2)² × 3.14 × maximum velocity (cm/s) × 0.5 × 60, measured at approximately the mid portion between its abdominal insertion and the origin of the ductus venosus. UVFV was measured by ultrasound once daily and was compared to the average of daily circuit flow volume directly measured.

RESULTS

UVFV was measured 168 times in 15 fetal sheep. The ratio of circuit flow volume to combined cardiac output remained stable within the anticipated physiological range throughout. UVFV measured by ultrasound showed good correlation to directly measured circuit flow (r = 0.72). Interclass correlation coefficients for intra-observer variability was 0.991 (95% confidence interval [CI], 0.979-0.996).

CONCLUSION

UVFV measured at the intra-abdominal portion using ultrasound shows a good correlation with directly measured circuit flow volume in UV of fetal sheep on the EXTEND system. Regular incorporation of such validated UVFV measures into clinical use may offer opportunities to better understand conditions of placental dysfunction.

Placenta morphology and biomarkers in pregnancies with congenital heart disease - A systematic review

Impaired placentation is an important contributing factor to intra-uterine growth restriction and pre-eclampsia in fetuses with congenital heart defects (CHD). These pregnancy complications occur more frequently in pregnancies with fetal CHD. One of the most important factors influencing the life of children with CHD is neurodevelopmental delay, which seems to start already in utero. Delayed neurodevelopment in utero may be correlated or even (partly) explained by impaired placentation in CHD cases. This systematic review provides an overview of published literature on placental development in pregnancies with fetal CHD. A systematic search was performed and the Newcastle-Ottawa scale was used to access data quality. Primary outcomes were placenta size and weight, vascular and villous architecture, immunohistochemistry, angiogenic biomarkers and/or placental gene expression. A total of 1161 articles were reviewed and 21 studies were included. Studies including CHD with a genetic disorder or syndrome and/or multiple pregnancies were excluded. Lower placental weight and elevated rates of abnormal umbilical cord insertions were found in CHD. Cases with CHD more frequently showed microscopic placental abnormalities (i.e. abnormal villous maturation and increased maternal vascular malperfusion lesions), reduced levels of angiogenic biomarkers and increased levels of anti-angiogenic biomarkers in maternal serum and umbilical cord blood. Altered gene expression involved in placental development and fetal growth were found in maternal serum and CHD placentas. In conclusion, abnormal placentation is found in CHD. More extensive studies are needed to elucidate the contribution of impaired placentation to delayed neurodevelopment in CHD cases.

Fetal Physiologically Based Pharmacokinetic Models: Systems Information on Fetal Cardiac Output and Its Distribution to Different Organs during Development

BACKGROUND AND OBJECTIVE

Fetal circulation is unique and the parameters describing hemodynamic status during development are critical for constructing a fetal physiologically based pharmacokinetic model. To date, a comprehensive review of circulatory changes during fetal development, with a specific focus on developing these models, has not been reported. The objective of this work was to collate, analyze, and mathematically describe physiological information on fetal cardiac output and tissue blood flows during development.

METHODS

A comprehensive literature search was carried out to collate and evaluate the changes to fetal cardiac output and fetal tissue blood flows during growth. The collated data were assessed, integrated, and analyzed to establish continuous mathematical functions describing the average parameter changes and variability during development.

RESULTS

Data were available for fetal cardiac output (14 Doppler studies), blood flow through the fetal umbilical vein (15 studies), ductus venosus (6 studies), liver veins (5 studies), brain (4 studies), lungs (5 studies), and kidneys (2 studies). Fetal cardiac output is described as either an age- or weight-dependent function. The latter is preferred as it generates an individualized cardiac output that is correlated to the fetal body weight. Blood flow as a proportion of fetal cardiac output to the liver, placenta, brain, kidneys, and lungs was age varying, whilst for the adipose, bone, heart, muscle, and skin the blood flow proportions were fixed. The pattern of change (with respect to direction and pace) for each of these parameters was different.

CONCLUSIONS

Despite limitations in the availability of some values, the collected data provide a useful resource for fetal physiologically based pharmacokinetic modeling. Potential applications of these data include predicting xenobiotic exposure and risk assessment in the fetus following the administration of maternally dosed drugs or unintended exposure to environmental toxicants.

The placenta as the window to congenital heart disease

PURPOSE OF REVIEW

There is an increasing recognition that structural abnormalities and functional changes in the placenta can have deleterious effects on the development of the fetal heart. This article reviews the role of the placenta and the potential impact of placental insufficiency on fetuses with congenital heart disease.

RECENT FINDINGS

The fetal heart and the placenta are directly linked because they develop concurrently with shared regulatory and signaling pathways. Placental disease is more common in pregnancies carrying a fetus with congenital heart disease and the fetal response to placental insufficiency may lead to the postnatal persistence of cardiac remodeling. The mechanisms underlying this placental-fetal axis of interaction potentially include genetic factors, oxidative stress, chronic hypoxia, and/or angiogenic imbalance.

SUMMARY

The maternal-placental-fetal circulation is critical to advancing our understanding of congenital heart disease. We must first expand our ability to detect, image, and quantify placental insufficiency and dysfunction in utero. Elucidating the modifiable factors involved in these pathways is an exciting opportunity for future research, which may enable us to improve outcomes in patients with congenital heart disease.