Changes in left ventricular output from fetal to early neonatal life

Cdk1 Deficiency Extends the Postnatal Window of Cardiomyocyte Proliferation and Restores Cardiac Function after Myocardial Infarction

Cyclin-dependent kinase 1 (Cdk1) is a master regulator of the G2-M transition between DNA replication and cell division. This study investigates the regulation of cardiomyocyte (CM) proliferation during the early neonatal period and following ischemic injury in adult mice. We analyzed cell cycle dynamics with the assessment of DNA synthesis, and cytokinesis in murine hearts during the first 15 days after birth. A distinct proliferative block was observed at 1 day, followed by a second wave of DNA synthesis at 4 days, leading to CM binucleation (CMBN) by day 5. Genome-wide mRNA profiling revealed the differential expression of cell cycle regulatory genes during this period, with a downregulation of factors involved in cell division and mitosis. The loss of Cdk1 impaired CMBN but extended the neonatal CM proliferation window until day 10 post-birth. In adult hearts, the cardiac-specific ablation of Cdk1 triggered CM proliferation post-myocardial-infarction (MI) in specific zones, driven by the activation of EGFR1 signaling and suppression of the anti-proliferative p38 and p53 signaling. This was accompanied by restoration of fractional shortening, mitochondrial function, and decreased reactive oxygen species. Additionally, cardiac hypertrophy was mitigated, and survival rates post-MI were increased in Cdk1-knockout mice. These findings reveal a novel role of Cdk1 in regulating cell cycle exit and re-entry in differentiated CMs and offer insights into potential strategies for cardiac repair.

Diagnostic value of reversed differential cyanosis in (supra)cardiac total anomalous pulmonary venous return

BACKGROUND

To investigate the occurrence of reversed differential cyanosis (RDC) in case of (supra)cardiac total anomalous pulmonary venous return (TAPVR), we explored the hemodynamic changes and oxygen saturation levels during the fetal-to-neonatal transition in (supra)cardiac TAPVR, thereby revealing determinant factors of RDC.

METHODS

A computational model was used to simulate the cardiovascular fetal-to-neonatal transition up to 24 h after birth. Abnormalities associated with TAPVR, like patent ductus arteriosus (PDA) and persistent pulmonary hypertension of the neonate (PPHN), were imposed on the model. Hemodynamic impact on flow distribution and right-sided pressures as well as oxygen saturations were assessed.

RESULTS

Model findings demonstrated that RDC in (supra)cardiac TAPVR was dependent on two key factors: (1) the type of pulmonary venous connection being supracardiac or cardiac, and (2) the presence of a patent ductus arteriosus exhibiting right-to-left shunting. Persistence of RDC was mainly determined by the latter; an increase in pulmonary-to-systemic pressure difference by PPHN or PDA-induced pulmonary over-circulation contributed to persistence of RDC.

CONCLUSION

This study highlights the significance of RDC in (supra)cardiac TAPVR and suggests to incorporate early screening ( < 24 h after birth) and to consider RDC as an immediate fail in screening protocols to ensure prompt detection of (supra)cardiac TAPVR.

IMPACT

Utilizing a validated computational model for the cardiovascular fetal-to-neonatal transition, this study sheds light on the complex hemodynamics in neonates with (supra)cardiac Total Anomalous Pulmonary Venous Return (TAPVR). Model findings suggest that the often-present pulmonary over-circulation in neonates with TAPVR might significantly contribute to the anomaly's frequent omission during pulse-oximetry screening beyond the first 24 h after birth. This study highlights the diagnostic value of reversed differential cyanosis in early screenings within the first 24 h after birth. By including RDC as an immediate fail in early pulse-oximetry screenings, the likelihood of missing (supra)cardiac TAPVR cases could be reduced.

Physiologically Based Pharmacokinetics Modeling in the Neonatal Population-Current Advances, Challenges, and Opportunities

Physiologically based pharmacokinetic (PBPK) modeling is an approach to predicting drug pharmacokinetics, using knowledge of the human physiology involved and drug physiochemical properties. This approach is useful when predicting drug pharmacokinetics in under-studied populations, such as pediatrics. PBPK modeling is a particularly important tool for dose optimization for the neonatal population, given that clinical trials rarely include this patient population. However, important knowledge gaps exist for neonates, resulting in uncertainty with the model predictions. This review aims to outline the sources of variability that should be considered with developing a neonatal PBPK model, the data that are currently available for the neonatal ontogeny, and lastly to highlight the data gaps where further research would be needed.

Adapting to a new environment: postnatal maturation of the human cardiomyocyte

The postnatal mammalian heart undergoes remarkable developmental changes, which are stimulated by the transition from the intrauterine to extrauterine environment. With birth, increased oxygen levels promote metabolic, structural and biophysical maturation of cardiomyocytes, resulting in mature muscle with increased efficiency, contractility and electrical conduction. In this Topical Review article, we highlight key studies that inform our current understanding of human cardiomyocyte maturation. Collectively, these studies suggest that human atrial and ventricular myocytes evolve quickly within the first year but might not reach a fully mature adult phenotype until nearly the first decade of life. However, it is important to note that fetal, neonatal and paediatric cardiac physiology studies are hindered by a number of limitations, including the scarcity of human tissue, small sample size and a heavy reliance on diseased tissue samples, often without age-matched healthy controls. Future developmental studies are warranted to expand our understanding of normal cardiac physiology/pathophysiology and inform age-appropriate treatment strategies for cardiac disease.

[Safe and Appropriate Pharmacotherapy in Paediatric Anaesthesia]

Safe and appropriate pharmacotherapy in children requires knowledge of age-group-specific features regarding pharmacology and drug dosing. In addition, aspects of medication safety must be considered. This review highlights basic principles and discusses key facts; further research in paediatric databases is recommended (www.kinderformularium.de).

Hemodynamic parameters after Delayed Cord Clamping (DCC) in term neonates: a prospective observational study

Background

Delayed cord clamping (DCC) is practiced worldwide, as standard care in both term and preterm babies. Our aim was to determine the hemodynamic effects of DCC on transitional circulation.

Material and methods

This prospective observational study was carried out in a tertiary care hospital, at Pune, India, from May 2018 to October 2019.Term neonates born during the study period were included. The primary outcome variables of the study were right ventricular output (RVO), left ventricular output (LVO), superior vena cava (SVC) flow (ml/kg/min) and heart rate(HR) at 12 ± 6 and 48 ± 6 h of life measured by point of care functional echocardiography. Inter-observer and intra-observer variability was calculated for these parameters.

Results

Out of a total of 2744 deliveries during the study period, 620 babies were included. Mean gestational age of the enrolled babies was 38.96 ± 1.08 weeks and mean birth weight was 2.9 ± 0.39 kg. Mean heart rate of babies recorded at 12 ± 6 h of life was 127 beats per minute (bpm) whereas it was 128 bpm at 48 ± 6 h of life. RVO {mean (SD)} was 209.55(44.89) and 205.85(46.35) ml/kg/min, LVO {mean (SD)} was 133.68(31.15) and 134.78(29.84) ml/kg/min whereas SVC flow {mean (SD)} was 106.85(26.21) and 109.29(25.11) ml/kg/min at 12 ± 6 and 48 ± 6 h of life respectively. There was good intra-observer agreement in all the variables.

SGA babies had a significantly higher heart rate at 12 ± 6 h of life as compared to AGA babies, although this difference in heart rate could not be appreciated at 48 ± 6 h of life. However SGA babies had a higher LVO, RVO and SVC flow than AGA babies at both the time points of observation.

Conclusion

After DCC there is less fluctuation in the hemodynamic parameters (heart rate, cardiac output) at the two time points of observation.. As compared to AGA babies, SGA babies had a significantly higher baseline heart rate, LVO, RVO and SVC flow. LVO of SGA babies after delayed cord clamping is found to be significantly lower than LVO seen in other studies, favoring the cardio-stabilizing effect of DCC.

Brief rationale

This is the first study with a large sample size evaluating the hemodynamic effects of DCC in term neonates by functional echocardiography. The normative data of heart rate and cardiac output of term, stable babies with small for gestational age(SGA) as a special subgroup undergoing DCC requires further evaluation.

Three Physiological Components That Influence Regional Cerebral Tissue Oxygen Saturation

Near-infrared spectroscopy (NIRS) measurement of regional cerebral tissue oxygen saturation (rcStO2) has become a topic of high interest in neonatology. Multiple studies have demonstrated that rcStO2 measurements are feasible in the delivery room during immediate transition and resuscitation as well as after admission to the neonatal intensive care unit. Reference ranges for different gestational ages, modes of delivery, and devices have already been published. RcStO2 reflects a mixed tissue saturation, composed of arterial (A), venous (V), and capillary signals, derived from small vessels within the measurement compartment. The A:V signal ratio fluctuates based on changes in oxygen delivery and oxygen consumption, which enables a reliable trend monitoring of the balance between these two parameters. While the increasing research evidence supports its use, the interpretation of the absolute values of and trends in rcStO2 is still challenging, which halts its routine use in the delivery room and at the bedside. To visualize the influencing factors and improve the understanding of rcStO2 values, we have created a flowchart, which focuses on the three major physiological components that affect rcStO2: oxygen content, circulation, and oxygen extraction. Each of these has its defining parameters, which are discussed in detail in each section.

Cardiovascular fetal-to-neonatal transition: an in silico model

BACKGROUND

Previous models describing the fetal-to-neonatal transition often lack oxygen saturation levels, homeostatic control mechanisms, phasic hemodynamic signals, or describe the heart with a time-varying elastance model.

METHODS

We incorporated these elements in the adapted CircAdapt model with the one-fiber model for myocardial contraction, to simulate the hemodynamics of the healthy term human fetal circulation and its transition during the first 24 h after birth. The fetal-to-neonatal model was controlled by a time- and event-based script of changes occurring at birth, such as lung aeration and umbilical cord clamping. Model parameters were based on and validated with human and animal data.

RESULTS

The fetal circulation showed low pulmonary blood flow, right ventricular dominance, and inverted mitral and tricuspid flow velocity patterns, as well as high mean ductus venosus flow velocity. The neonatal circulation showed oxygen saturation levels to gradually increase to 98% in the first 15 min after birth as well as temporary left ventricular volume overload.

CONCLUSIONS

Hemodynamics of the term fetus and 24-h-old neonate, as well as the events occurring directly after birth and the transition during the first 24 h after birth, were realistically represented, allowing the model to be used for educational purposes and future research.

IMPACT

With the addition of oxygen saturation levels, homeostatic pressure-flow control mechanisms, and the one-fiber model for myocardial contraction, a new closed-loop cardiovascular model was constructed to give more insight into the healthy term human fetal circulation and its cardiovascular transition during the first 24 h after birth. Extensive validation confirmed that the hemodynamics of the term fetus and the fetal-to-neonatal transition were realistically represented with the model. This well-validated and versatile model can serve as an education as well as a research platform for in silico investigation of fetal-to-neonatal hemodynamic changes under a wide range of physiological and pathophysiological conditions.

The perinatal transition and early neonatal period in hypoplastic left heart syndrome is associated with reduced systemic and cerebral perfusion

BACKGROUND

The impact of the striking perinatal circulatory changes on blood flow distribution have not to date been well-examined in hypoplastic left heart syndrome (HLHS). This study aims to document perinatal redistribution of cardiac output in HLHS compared to healthy controls, to further understand the impact of perinatal transition on cerebral and systemic blood flow.

METHODS

Prospectively recruited HLHS cases (n=31) and healthy controls (n=19) underwent serial echocardiography from late fetal stages to 96 hours after birth. Combined cardiac output (CCO), systemic, pulmonary, cerebrovascular and splanchnic flow data were compared between HLHS neonates and controls, and the impact of vasoactive support and positive pressure ventilation (PPV) in HLHS patients examined.

RESULTS

In late gestation, CCO was similar between HLHS and controls, whereas middle cerebral artery (MCA) pulsatility index (PI) in HLHS was consistent with low cerebral vascular resistance. In the 96 hours after birth, CCO and pulmonary blood flow progressively increased in HLHS compared to controls (p<0.001), and CCO was further increased in HLHS neonates receiving vasoactive support (p=0.01). HLHS neonates had reduced systemic and 6-24hr superior vena cava (SVC) flow when compared to controls (p<0.001). Low systemic flow was further suggested by increased MCA and celiac artery PI at 6 - 48 hours in HLHS neonates (p<0.001). Systemic and SVC flow did not differ between those with and without vasoactive support.

CONCLUSION

We provide quantitative echocardiographic evidence associating impaired cerebral and systemic blood flow with perinatal hemodynamic changes in the preoperative HLHS neonate.

Feasibility of non-invasive cardiac output monitoring at birth using electrical bioreactance in term infants

BACKGROUND

Non-invasive cardiac output monitoring (NICOM) provides continuous estimation of cardiac output. This has potential for use in the delivery suite in the management of acutely depressed term infants. This study aims to measure cardiac output in term infants at delivery and in the first hours of life.

METHODS

Parents of term infants due to be born by elective caesarean section or vaginal delivery at Cork University Maternity Hospital, Ireland were approached in the antenatal period to participate. Cardiac output was measured using a CHEETAH NICOM device, which uses electrical bioreactance technology, at birth and at 2 hours of life.

RESULTS

Forty-nine newborns were included. The median gestational age was 39 (IQR: 39-40) weeks and the median birth weight was 3.50 (IQR: 3.14-3.91) kg. Cardiac output measurements were obtained at a median of 8 (IQR: 5-12) min of life. The mean (SD) cardiac output was 101 (24) mL/kg/min in the delivery room and 89 (22) mL/kg/min at 2 hours of life. There was a statistically significant decrease in cardiac output from birth to 2 hours of life (difference in mean (95% CI): 13.5 (9.2 to 17.9) mL/kg/min, p<0.001, n=47). There were no adverse effects associated with NICOM.

DISCUSSION

This technique is feasible and safe in the delivery room. Mean cardiac output measures using NICOM are lower than those found in studies which used echocardiography to determine cardiac output at birth.

A Preterm Physiologically Based Pharmacokinetic Model. Part I: Physiological Parameters and Model Building

BACKGROUND

Developmental physiology can alter pharmacotherapy in preterm populations. Because of ethical and clinical constraints in studying this vulnerable age group, physiologically based pharmacokinetic models offer a viable alternative approach to predicting drug pharmacokinetics and pharmacodynamics in this population. However, such models require comprehensive information on the changes of anatomical, physiological and biochemical variables, where such data are not available in a single source.

OBJECTIVE

The objective of this study was to integrate the relevant physiological parameters required to build a physiologically based pharmacokinetic model for the preterm population.

METHODS

Published information on developmental preterm physiology and some drug-metabolising enzymes were collated and analysed. Equations were generated to describe the changes in parameter values during growth.

RESULTS

Data on organ size show different growth patterns that were quantified as functions of bodyweight to retain physiological variability and correlation. Protein binding data were quantified as functions of age as the body weight was not reported in the original articles. Ontogeny functions were derived for cytochrome P450 1A2, 3A4 and 2C9. Tissue composition values and how they change with age are limited.

CONCLUSIONS

Despite the limitations identified in the availability of some tissue composition values, the data presented in this article provide an integrated resource of system parameters needed for building a preterm physiologically based pharmacokinetic model.

Transient Pulmonary Artery Hypertension in Holstein Neonate Calves

Simple Summary

At birth, calves are challenged to maintain their vital functions that were previously supported by the placenta of cows. Failures in the neonatal adaptation process can occur during this and can cause the death of neonates. The present study aimed at the invasive hemodynamic evaluation of calves during the first 30 days of life to elucidate the changes in calves during this stage of life. In conclusion, the results of this research show a transient pulmonary arterial hypertension during the process of adapting to extrauterine life.

Abstract

The neonatal period is a challenging phase for calves, and during this phase constant adaptations are required. The aim of the present study was to evaluate the invasive hemodynamics with the Swan-Ganz catheter in neonate calves to understand adaptive changes during the first 30 days of life. A prospective and observational study was conducted with 10 Holstein calves. Assessments of the right atrial pressure (RAP), right ventricular pressure (RVP), pulmonary artery pressure (PAP), pulmonary capillary pressure (PW), cardiac output (CO), heart rate (HR), pulmonary vascular resistance (PVR), and blood gas levels were performed. The analyses of PAP, PVR, PW, HR, sO₂, and arterial blood gases differed (p < 0.05) between the evaluated periods. Our results indicated transient pulmonary artery hypertension during the process of extrauterine adaptation during the first 30 days of life. This hypertension must be considered as physiological and consequent to the neonatal adaptation process.

Prenatal prediction of neonatal haemodynamic adaptation after maternal hyperoxygenation

Abstract

The reactivity of the pulmonary vascular bed to the administration of oxygen is well established in the post-natal circulation. The vasoreactivity demonstrated by the fetal pulmonary artery Doppler waveform in response to maternal hyperoxia has been investigated. We sought to investigate the relationship between the reactivity of the fetal pulmonary arteries to hyperoxia and subsequent neonatal cardiac function in the early newborn period.

Methods

This explorative study with convenience sampling measured pulsatility index (PI), resistance index (RI), acceleration time (AT), and ejection time (ET) from the fetal distal branch pulmonary artery (PA) at baseline and following maternal hyperoxygenation (MH). Oxygen was administered for 10 min at a rate of 12 L/min via a partial non-rebreather mask. A neonatal functional echocardiogram was performed within the first 24 h of life to assess ejection fraction (EF), left ventricular output (LVO), and neonatal pulmonary artery AT (nPAAT). This study was conducted in the Rotunda Hospital, Dublin, Ireland.

Results

Forty-six women with a singleton pregnancy greater than or equal to 31 weeks’ gestational age were prospectively recruited to the study. The median gestational age was 35 weeks. There was a decrease in fetal PAPI and PARI following MH and an increase in fetal PAAT, leading to an increase in PA AT:ET. Fetuses that responded to hyperoxygenation were more likely to have a higher LVO (135 ± 25 mL/kg/min vs 111 ± 21 mL/kg/min, p < 0.01) and EF (54 ± 9% vs 47 ± 7%,p = 0.03) in the early newborn period than those that did not respond to MH prenatally. These findings were not dependent on left ventricular size or mitral valve (MV) annular diameter but were related to an increased MV inflow. There was no difference in nPAAT.

Conclusion

These findings indicate a reduction in fetal pulmonary vascular resistance (PVR) and an increase in pulmonary blood flow and left atrial return following MH. The fetal response to hyperoxia reflected an optimal adaptation to postnatal life with rapid reduction in PVR increasing measured cardiac output.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12884-020-03403-y.

Cardiac adaptation in asphyxiated infants treated with therapeutic hypothermia

BACKGROUND

Hypoxic ischemic encephalopathy (HIE) affects  one to two newborns per 1,000 live births and oftentimes involves multi-organ insult. The objectives were to assess the evolution of cardiac function in infants with HIE treated with therapeutic hypothermia using echocardiography (ECHO).

METHODS

Archived data during the period 2010-2016 was assessed. Amongst the infants with baseline ECHO assessments, a sub-cohort which had assessments in all the three phases (baseline/pre-active cooling [T1], cooling [T2] and rewarming [T3]) was analyzed separately.

RESULTS

Thirty three infants formed part of the overall cohort, the gestation and birthweight were 39.6 ± 1.6 weeks and 3306 ± 583 g, respectively. Baseline (T1) information noted impaired cardiac performance (right ventricle stroke volume 1.08 ± 0.04 ml/kg, fractional area change [FAC] 24 ± 0.5% and tricuspid annular peak systolic excursion [TAPSE] 7.46 ± 0.11mm). Serial information was available for 24 of 33 infants. Cardiac function improved significantly between the cooling and the re-warming kphases. This included changes in right ventricular output (127 ± 34 vs 164 ± 47 ml/kg/min, p <0.01) and FAC (20 ± 3 vs 28 ± 2%, p<0.01). Pairwise comparisons for fractional shortening did not show significant changes. From the cooling to the rewarming phase, maximum change was noted in FAC (26.3 ± 9.8%) while minimum change was noted in fractional shortening (median, interquartile range) of 4.6% (1.4, 9.1). Significant correlation between TAPSE and time to peak velocity as a proportion of right ventricular ejection time was noted (r2 = 0.68, p <0.001).

CONCLUSIONS

In infants with moderate to severe HIE, cardiac function evolves during various phases of therapeutic hypothermia. Low output state during cooling may be due to a combination of the disease state (HIE) and cooling therapy.

Size and shape of the four-chamber view of the fetal heart in fetuses with an estimated fetal weight less than the tenth centile

BACKGROUND

Fetuses with an estimated fetal weight below the 10^th centile have an increased risk of adverse perinatal and long-term outcomes as well as increased rates of cardiac dysfunction, which often alters cardiac size and shape of the 4-chamber view and the individual ventricles. As a result, a simple method has emerged to screen for potential cardiac dysfunction in fetuses with estimated fetal weights <10^th centile by measuring the size and shape of the 4-chamber view and the size of the ventricles.

OBJECTIVE

To determine the number of fetuses with an abnormal size and shape of the 4-chamber view and size of the ventricles in fetuses with an estimated fetal weight <10^th centile.

MATERIALS AND METHODS

This was a retrospective study of 50 fetuses between 25 and 37 weeks of gestation with an estimated fetal weight <10^th centile. Data from their last examination were analyzed. From an end-diastolic image of the 4-chamber view, the largest basal-apical length and transverse width were measured from their corresponding epicardial borders. This allowed the 4-chamber view area and global sphericity index (4-chamber view length/4-chamber view width) to be computed. In addition, tracing along the endocardial borders with speckle tracking software enabled measurements of the right and left ventricular chamber areas and the right ventricle/left ventricle area ratios to be computed. Doppler waveform pulsatility indices from the umbilical (umbilical artery pulsatility index) and middle cerebral arteries (middle cerebral artery pulsatility index) were analyzed, and the cerebroplacental ratio (middle cerebral artery pulsatility index/umbilical artery pulsatility index) computed. Umbilical artery pulsatility indices >90^th and cerebroplacental ratios <10^th centile were considered abnormal. Using data from the control fetuses, the centile for each of the cardiac measurements was categorized by whether it was <10^th or >90^th centile, depending upon the measurement.

RESULTS

Of the 50 fetuses with estimated fetal weight <10^th centile, 50% (n = 25) had a normal umbilical artery pulsatility index and cerebroplacental ratio. These fetuses had significantly more (P < 0.02 to <0.0001) abnormalities of the size and shape of the 4-chamber view than controls. In all, 44% had a 4-chamber view area >90^th centile, 32% had a 4-chamber view global sphericity index <10^th centile, 56% had a 4-chamber view width >90^th centile, and 80% had 1 or more abnormalities of size and/or shape. The remaining 50% of fetuses (n = 25) had abnormalities of 1 or both for the umbilical artery pulsatility index and/or cerebroplacental ratio. These fetuses had significantly higher rates of abnormalities (P <0.05 to <0.0001) than controls for the following 4-chamber view measurements: 36% had a 4-chamber view area >90^th centile; 28% had a 4-chamber view global sphericity index <10^th centile; and 68% had a 4-chamber view width >90^th centile. Only those fetuses with an abnormal umbilical artery pulsatility index had significant changes in ventricular size; 56% had a left ventricular area <10^th centile; 28% had a right ventricular area <10^th centile; 36% had right ventricular/left ventricular area ratio >90^th centile. One or more of the above abnormal measurements were present in 92% of the fetuses.

CONCLUSION

Higher rates of abnormalities of cardiac size and shape of the 4-chamber view were found in fetuses with an estimated fetal weight <10^th centile, regardless of their umbilical artery pulsatility index and cerebroplacental ratio measurements. Those with a normal umbilical artery pulsatility index and an abnormal cerebroplacental ratio had larger and wider measurements of the 4-chamber view. In addition, the shape of the 4-chamber view was more globular or round than in controls. These fetuses may have an increased risk of perinatal complications and childhood and/or adult cardiovascular disease. Screening tools derived from the 4-chamber view, acting as surrogates for ventricular dysfunction, may identify fetuses who could benefit from further comprehensive testing and future preventive interventions.

Regulation of cardiomyocyte maturation during critical perinatal window

A primary limitation in the use of pluripotent stem cell-derived cardiomyocytes (PSC-CMs) for both patient health and scientific investigation is the failure of these cells to achieve full functional maturity. In vivo, cardiomyocytes undergo numerous adaptive structural, functional and metabolic changes during maturation. By contrast, PSC-CMs fail to fully undergo these developmental processes, instead remaining arrested at an embryonic stage of maturation. There is thus a significant need to understand the biological processes underlying proper CM maturation in vivo. Here, we discuss what is known regarding the initiation and coordination of CM maturation. We postulate that there is a critical perinatal window, ranging from embryonic day 18.5 to postnatal day 14 in mice, in which the maturation process is exquisitely sensitive to perturbation. While the initiation mechanisms of this process are unknown, it is increasingly clear that maturation proceeds through interconnected regulatory circuits that feed into one another to coordinate concomitant structural, functional and metabolic CM maturation. We highlight PGC1α, SRF and the MEF2 family as transcription factors that may potentially mediate this cross-talk. We lastly discuss several emerging technologies that will facilitate future studies into the mechanisms of CM maturation. Further study will not only produce a better understanding of its key processes, but provide practical insights into developing a robust strategy to produce mature PSC-CMs.

The Pathophysiology of Low Systemic Blood Flow in the Preterm Infant

Assessment and treatment of the VLBW infant with cardiovascular impairment requires understanding of the underlying physiology of the infant in transition. The situation is dynamic with changes occurring in systemic blood pressure, pulmonary pressures, myocardial function, and ductal shunt in the first postnatal days. New insights into the role of umbilical cord clamping in the transitional circulation have been provided by large clinical trials of early versus later cord clamping and a series of basic science reports describing the physiology in an animal model. Ultrasound assessment is invaluable in assessment of the physiology of the transition and can provide information about the size and shunt direction of the ductus arteriosus, the function of the myocardium and its filling as well as measurements of the cardiac output and an estimate of the state of peripheral vascular resistance. This information not only allows more specific treatment but it will often reduce the need for treatment.

Neonatal Hemodynamics: From Developmental Physiology to Comprehensive Monitoring

Maintenance of neonatal circulatory homeostasis is a real challenge, due to the complex physiology during postnatal transition and the inherent immaturity of the cardiovascular system and other relevant organs. It is known that abnormal cardiovascular function during the neonatal period is associated with increased risk of severe morbidity and mortality. Understanding the functional and structural characteristics of the neonatal circulation is, therefore, essential, as therapeutic hemodynamic interventions should be based on the assumed underlying (patho)physiology. The clinical assessment of systemic blood flow (SBF) by indirect parameters, such as blood pressure, capillary refill time, heart rate, urine output, and central-peripheral temperature difference is inaccurate. As blood pressure is no surrogate for SBF, information on cardiac output and systemic vascular resistance should be obtained in combination with an evaluation of end organ perfusion. Accurate and reliable hemodynamic monitoring systems are required to detect inadequate tissue perfusion and oxygenation at an early stage before this result in irreversible damage. Also, the hemodynamic response to the initiated treatment should be re-evaluated regularly as changes in cardiovascular function can occur quickly. New insights in the understanding of neonatal cardiovascular physiology are reviewed and several methods for current and future neonatal hemodynamic monitoring are discussed.

Steel reinforced composite silicone membranes and its integration to microfluidic oxygenators for high performance gas exchange

Respiratory distress syndrome (RDS) is one of the main causes of fatality in newborn infants, particularly in neonates with low birth-weight. Commercial extracorporeal oxygenators have been used for low-birth-weight neonates in neonatal intensive care units. However, these oxygenators require high blood volumes to prime. In the last decade, microfluidics oxygenators using enriched oxygen have been developed for this purpose. Some of these oxygenators use thin polydimethylsiloxane (PDMS) membranes to facilitate gas exchange between the blood flowing in the microchannels and the ambient air outside. However, PDMS is elastic and the thin membranes exhibit significant deformation and delamination under pressure which alters the architecture of the devices causing poor oxygenation or device failure. Therefore, an alternate membrane with high stability, low deformation under pressure, and high gas exchange was desired. In this paper, we present a novel composite membrane consisting of an ultra-thin stainless-steel mesh embedded in PDMS, designed specifically for a microfluidic single oxygenator unit (SOU). In comparison to homogeneous PDMS membranes, this composite membrane demonstrated high stability, low deformation under pressure, and high gas exchange. In addition, a new design for oxygenator with sloping profile and tapered inlet configuration has been introduced to achieve the same gas exchange at lower pressure drops. SOUs were tested by bovine blood to evaluate gas exchange properties. Among all tested SOUs, the flat design SOU with composite membrane has the highest oxygen exchange of 40.32 ml/min m². The superior performance of the new device with composite membrane was demonstrated by constructing a lung assist device (LAD) with a low priming volume of 10 ml. The LAD was achieved by the oxygen uptake of 0.48-0.90 ml/min and the CO₂ release of 1.05-2.27 ml/min at blood flow rates ranging between 8 and 48 ml/min. This LAD was shown to increase the oxygen saturation level by 25% at the low pressure drop of 29 mm Hg. Finally, a piglet was used to test the gas exchange capacity of the LAD in vivo. The animal experiment results were in accordance with in-vitro results, which shows that the LAD is capable of providing sufficient gas exchange at a blood flow rate of ∼24 ml/min.

The Successful Immediate Neonatal Transition to Extrauterine Life

Purpose:

To define and describe the processes underlying the successful neonatal transition to extrauterine life and methods to assess the transition.

Method:

Cumulative Index to Nursing and Allied Health Literature (CINAHL), Embase, Web of Science, and Google Scholar were searched using a combination of the key words neonate, neonatal, newborn, transition, respiratory OR pulmonary, cardiac, metabolic, pH, umbilical cord, and assessment. Articles in English and German were reviewed. The final sample of articles consisted of one randomized controlled trial, 30 observational studies using human neonates, one observational study using rabbit pups, one secondary analysis, three systematic reviews, and 23 review articles.

Major Findings:

The pertinent findings in regard to normal events in the respiratory, cardiovascular, and metabolic transitions are reviewed and summarized. We address the underlying factors necessary for the transition to extrauterine life, specify the consequences of a successful transition, and review common assessment approaches.

Conclusion:

Available evidence indicates that the successful immediate transition to extrauterine life should be completed within 1–3 hr after birth, though some adaptive processes can fail as late as 24–48 hr after birth. Further research is necessary to identify a feasible, easily used, noninvasive method to assess the status of a neonate’s transition to extrauterine life.

Fetal Physiology and the Transition to Extrauterine Life

The physiology of the fetus is fundamentally different from the neonate, with both structural and functional distinctions. The fetus is well-adapted to the relatively hypoxemic intrauterine environment. The transition from intrauterine to extrauterine life requires rapid, complex, and well-orchestrated steps to ensure neonatal survival. This article explains the intrauterine physiology that allows the fetus to survive and then reviews the physiologic changes that occur during the transition to extrauterine life. Asphyxia fundamentally alters the physiology of transition and necessitates a thoughtful approach in the management of affected neonates.

Transition from fetal to neonatal circulation: Modeling the effect of umbilical cord clamping

Hemodynamics of the fetal to neonatal transition are orchestrated through complex physiological changes and results in cardiovascular adaptation to the adult biventricular circulation. Clinical practice during this critical period can influence vital organ physiology for normal newborns, premature babies and congenital heart defect patients. Particularly, the timing of the cord clamping procedure, immediate (ICC) vs. delayed cord clamping (DCC), is hypothesized to be an important factor for the transitory fetal hemodynamics. The clinical need for a quantitative understanding of this physiology motivated the development of a lumped parameter model (LPM) of the fetal cardio-respiratory system covering the late-gestation to neonatal period. The LPM was validated with in vivo clinical data and then used to predict the effects of cord clamping procedures on hemodynamics and vital gases. Clinical time-dependent resistance functions to simulate the vascular changes were introduced. For DCC, placental transfusion (31.3 ml) increased neonatal blood volume by 11.7%. This increased blood volume is reflected in an increase in preload pressures by ~20% compared to ICC, which in turn increased the cardiac output (CO) by 20% (COICC=993 ml/min; CODCC=1197 ml/min). Our model accurately predicted dynamic flow patterns in vivo. DCC was shown to maintain oxygenation if the onset of pulmonary respiration was delayed or impaired. On the other hand, a significant 25% decrease in oxygen saturations was observed when applying ICC under the same physiological conditions. We conclude that DCC has a significant impact on newborn hemodynamics, mainly because of the improved blood volume and the sustained placental respiration.

Time course study of blood pressure in term and preterm infants immediately after birth

Objective

To describe temporal changes in systolic, diastolic, and mean blood pressure (SBP, DBP, and MBP, respectively) in term and preterm infants immediately after birth.

Methods

Prospective observational two-center study. In term infants SBP, DBP, and MBP were assessed non-invasively every minute for the first 15 minutes, and in preterm infants every minute for the first 15 minutes, as well as at 20, 25, 30, 45, and 60 minutes after birth. Regression analyses were performed by gender and respiratory support in all neonates; and by mode of delivery, cord clamping time, and development of ultrasound-detected brain injury in preterm neonates.

Results

Term infants (n = 54) had a mean (SD) birth weight of 3298 (442) g and gestational age of 38 (1) weeks, and preterm infants (n = 94) weighed 1340 (672) g and were 30 (3) weeks gestation. Term infants’ SBP, DBP and MBP within the first 15 minutes after birth were independent of gender or respiratory support. Linear mixed regression analysis showed that preterm infants, who were female, born vaginally, had delayed cord clamping and did not require positive pressure ventilation nor develop periventricular injury or ventriculomegaly, had significantly higher SBP, DBP, and MBP at some measurement points within the first hour after birth.

Conclusions

We present novel reference ranges of BP immediately after birth in a cohort of term and preterm neonates. They may aid in optimization of cardiovascular support during early transition at all gestations.

Myocardial function in term and preterm infants. Influence of heart size, gestational age and postnatal maturation

BACKGROUND

Sparse knowledge exists on the differences in cardiac function between term and preterm infants. This study examines the impact of heart size, gestational age and postnatal maturation on myocardial function.

AIM

To assess and compare serial echocardiographic indices of myocardial function in term and moderately preterm infants.

METHODS

Longitudinal, prospective, observational echocardiographic cohort study of 45 healthy term infants examined at day three and at 12-20weeks postnatal age and 53 moderately preterm infants (gestational age 31-35weeks) examined at day three and at term equivalent (4-10weeks postnatal age).

OUTCOMES

Primary: Systolic mitral and tricuspid annular plane excursions and annular peak systolic pulsed wave tissue Doppler (pwTDI) velocities. Secondary: Indices normalized for heart size.

RESULTS

On day three, all indices were higher in the term than in the preterm infants whereas normalized systolic pwTDI velocities were lower in the term infants and normalized excursions showed no difference. All indices increased with advanced postnatal age. The indices in term infants on day three were lower than in preterm infants at term equivalent, with and without normalization. After postnatal maturation in both groups, all indices were higher in the term group (except left pwTDI), whereas normalized indices showed no consistent pattern.

CONCLUSIONS

Myocardial function indices increased with gestational age at birth and more profoundly with postnatal maturation. Serial examinations of non-normalized and normalized myocardial function indices showed no sustained differences between the preterm and the term infants. Normalization by heart size may be of value when assessing myocardial function in infants.

Hypoxia signaling controls postnatal changes in cardiac mitochondrial morphology and function

Fetal cardiomyocyte adaptation to low levels of oxygen in utero is incompletely understood, and is of interest as hypoxia tolerance is lost after birth, leading to vulnerability of adult cardiomyocytes. It is known that cardiac mitochondrial morphology, number and function change significantly following birth, although the underlying molecular mechanisms and physiological stimuli are undefined.

Here we show that the decrease in cardiomyocyte HIF-signaling in cardiomyocytes immediately after birth acts as a physiological switch driving mitochondrial fusion and increased postnatal mitochondrial biogenesis. We also investigated mechanisms of ATP generation in embryonic cardiac mitochondria. We found that embryonic cardiac cardiomyocytes rely on both glycolysis and the tricarboxylic acid cycle to generate ATP, and that the balance between these two metabolic pathways in the heart is controlled around birth by the reduction in HIF signaling. We therefore propose that the increase in ambient oxygen encountered by the neonate at birth acts as a key physiological stimulus to cardiac mitochondrial adaptation.

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The reduction in HIF signaling encountered by the heart following birth acts as a physiological switch.

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Reduced postnatal cardiac HIF signaling affects mitochondrial number, structure and function.

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Experimental study of mitochondria is prone to artifacts due to the effect of oxygen.

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Cardiomyocytes employ multiple strategies to function in low oxygen in utero.

Fetal ventricular shortening fraction in hydrops fetalis

OBJECTIVE

To estimate fetal ventricular shortening fraction, representing cardiac contractility, derived from cardiospatiotemporal image correlation with M-mode display "STIC-M" in fetuses with hydrops fetalis secondary to high-output (fetal anemia) and low-output causes (congenital heart defects).

METHODS

A cross-sectional study was conducted in normal fetuses (group 1), fetuses with hemoglobin Bart's disease with (group 2) and without (group 3) hydrops fetalis, and those with hydrops fetalis resulting from cardiac defects (group 4). Volume data sets of cardiospatiotemporal image correlations were acquired for each group for subsequent offline analysis with cardiospatiotemporal image correlation with M-mode display. Group 1 data were used to construct reference ranges of left and right ventricular shortening fraction for assessment of fetuses in the remaining groups.

RESULTS

A total of 606 measurements, 15-35 per week, were performed in normal fetuses to construct reference ranges as well as Z-scores of left and right ventricular shortening fraction. Both parameters were decreased with increasing gestation with weak correlation (r2=0.141, P<.001 and r2=0.055, P<.001, respectively). Shortening fraction did not significantly change among 111 fetuses with hemoglobin Bart's disease with and without hydrops. However, left and right ventricular shortening fraction were significantly decreased (mean Z-scores 5 standard deviations and 8 standard deviations below the mean, respectively) in 21 hydropic fetuses as a result of congenital heart defects (P<.001).

CONCLUSION

Fetuses with hydrops fetalis secondary to cardiac defects and anemia have a different pattern of shortening fraction. Hydrops fetalis resulting from cardiac defect is primarily caused by cardiac decompensation; whereas in fetal anemia, it is probably caused by hypervolemia with cardiac decompensation occurring when the cardiac compensatory mechanism is exhausted.

LEVEL OF EVIDENCE

II.

The myocardial function during and after whole-body therapeutic hypothermia for hypoxic-ischemic encephalopathy, a cohort study

BACKGROUND

Therapeutic hypothermia has become standard treatment for moderate and severe neonatal hypoxic-ischemic encephalopathy (HIE) to reduce cerebral morbidity and mortality. The effect on the heart is incompletely explored.

AIM

To assess the myocardial function during and after whole-body therapeutic hypothermia for HIE.

STUDY DESIGN

Observational cohort study.

SUBJECTS

Forty-four infants with HIE cooled for 72hours were compared with 48 healthy term infants and 20 normothermic infants with HIE.

OUTCOME MEASURES

Tissue Doppler deformation indices of myocardial function (peak systolic strain, peak systolic strain-rate, early diastole strain-rate and strain-rate in atrial systole) during (days 1 and 3) and after (day 4) therapeutic hypothermia.

RESULTS

On days one and three all indices in both HIE groups were lower than the corresponding indices in the healthy infants. The two HIE groups had similar indices, except peak systolic strain-rate on days 1 and 3 and strain-rate in atrial systole on day 1. All strain-rate indices improved from day 3 to 4 (after rewarming) in the cooled group and achieved similar values to those in healthy infants on day 3. All indices were higher in the cooling-group after rewarming than in the normothermic infants with HIE on day 3, except early diastolic strain-rate.

CONCLUSIONS

Infants with HIE had similarly impaired myocardial function during days 1-3 whether normothermic or hypothermic. The myocardial function improved significantly at day 4 (after rewarming), approaching the day 3 levels in the healthy neonates.

Noninvasive measurements of hemodynamic transition directly after birth

BACKGROUND

Cardiac output depends on stroke volume and heart rate (HR). Only HR is used to monitor hemodynamic transition.

METHODS

In 24 term newborns born via cesarean section, HR and preductal blood pressure (BP) were measured. Also, using echocardiography, left ventricular dimensions and (Doppler derived) left ventricular output (LVO) were examined at 2, 5, and 10 min after birth.

RESULTS

Mean (SD) HR and BP did not change with time (mean HR: 157 (21) bpm at 2 min, 154 (17) bpm at 5 min, and 155 (14) bpm at 10 min; mean BP: 51.2 (15.4) mm Hg at 2 min, 50.5 (11.7) mm Hg at 5 min, and 49.6 (9.5) mm Hg at 10 min). Left ventricular end-diastolic diameter increased from 2 to 5 min (14.3 (1.3) vs. 16.3 (1.7) mm; P < 0.001) and stabilized at 10 min (16.7 (1.4) mm). LVO increased between 2 and 5 min (151 (47) vs. 203 (55) ml/kg/min; P < 0.001) and stabilized at 10 min (201 (45) ml/kg/min). LVO increase was associated with rise in left ventricular stroke volume (r = 0.94; P < 0.001), not with rise in HR (r = 0.37; P value not significant).

CONCLUSION

Left ventricular dimensions and LVO significantly increased the first 5 min after birth and stabilized at 10 min, whereas BP remained stable. LVO and left ventricular dimension increase are presumably due to increasing left ventricular preload resulting from pulmonary blood flow and ductal shunting increase.

Transitional cardiovascular physiology and comprehensive hemodynamic monitoring in the neonate: relevance to research and clinical care

A thorough understanding of developmental cardiovascular physiology is essential for early recognition of cardiovascular compromise, selective screening of at-risk groups of neonates, and individualized management using pathophysiology-targeted interventions. Although we have gained a better understanding of the physiology and pathophysiology of postnatal cardiovascular transition over the past decade with the use of sophisticated methods to study neonatal hemodynamics, most aspects of neonatal hemodynamics remain incompletely understood. In addition, targeted therapeutic interventions of neonatal hemodynamic compromise have not been shown to improve mortality and clinically relevant outcomes. However, the recent development of comprehensive hemodynamic monitoring systems capable of non-invasive, continuous and simultaneous bedside assessment of cardiac output, organ blood flow, microcirculation, and tissue oxygen delivery has made sophisticated analysis of the obtained physiologic data possible and has created new research opportunities with the potential of direct implications to patient care.

Tissue Doppler imaging in very preterm infants during the first 24 h of life: an observational study

BACKGROUND

Very preterm newborn infants often need cardiovascular support. More knowledge about myocardial function and factors that influence the immature myocardium may be helpful for optimising cardiovascular support in these infants.

OBJECTIVE

Serial assessment of global myocardial function by means of colour tissue Doppler imaging (cTDI) in very and extremely preterm infants during the first 24 h of life.

STUDY DESIGN

One-centre, prospective, observational longitudinal cohort study in a third level Neonatal Intensive Care Unit. Sixty-five infants with median (range) gestational age (GA) 27 (24-31) weeks and birth weight (BW) 1049 (484-1620) g underwent echocardiographic examinations including cTDI at 5, 12 and 24 h after birth.

MAIN OUTCOME MEASURES

Peak systolic and peak diastolic annular velocity and peak annular displacement of the left and right ventricle.

RESULTS

There was a significant reduction in systolic and diastolic velocities and displacement of both ventricles from 5 to 12 h age. From 12 to 24 h, there was a non-significant increase in myocardial velocities and displacement. At 5 h, babies with haemodynamically significant patent ductus arteriosus (PDA) had significantly higher systolic and diastolic velocities in both ventricles than those with non-significant PDA.

CONCLUSIONS

Myocardial tissue velocities decrease significantly from 5 to 12 h after birth in very preterm infants. Further studies are needed to confirm these results and to determine their clinical implications.

Measuring physiological changes during the transition to life after birth

The transition to life after birth is characterized by major physiological changes in respiratory and hemodynamic function, which are predominantly initiated by breathing at birth and clamping of the umbilical cord. Lung aeration leads to the establishment of functional residual capacity, allowing pulmonary gas exchange to commence. This triggers a significant decrease in pulmonary vascular resistance, consequently increasing pulmonary blood flow and cardiac venous return. Clamping the umbilical cord also contributes to these hemodynamic changes by altering the cardiac preload and increasing peripheral systemic vascular resistance. The resulting changes in systemic and pulmonary circulation influence blood flow through both the oval foramen and ductus arteriosus. This eventually leads to closure of these structures and the separation of the pulmonary and systemic circulations. Most of our knowledge on human neonatal transition is based on human (fetal) data from the 1970s and extrapolation from animal studies. However, there is renewed interest in performing measurements directly at birth. By using less cumbersome techniques (and probably more accurate), our previous understanding of the physiological transition at birth is challenged, as well as the causes and consequences for when this transition fails to progress. This review will provide an overview of physiological measurements of the respiratory and hemodynamic transition at birth. Also, it will give a perspective on some of the upcoming technological advances in physiological measurements of neonatal transition in infants who are unable to make the transition without support.

Cardiac blood flow measurements in stable full term small for gestational age neonates

BACKGROUND

Cardiac blood flow measurements are useful in the haemodynamic management of neonates. Cardiac blood flows can be estimated with functional echocardiography as follows; flow in Superior Vena Cava (SVC), Right Ventricular Outflow (RVO) and Left Ventricular Outflow (LVO). Studies in preterm infants have shown that abnormal superior vena cava flow is associated with poor neurodevelopmental outcomes. To date, normative data on LVO, RVO and SVC flows has been established for term appropriate for gestational age neonates and preterm neonates, but no data is available on RVO, LVO and SVC flows for term small for gestational age neonates.

OBJECTIVE

To determine Right Ventricular Output (RVO), Left Ventricular Output (LVO) and Superior Vena Cava (SVC) flow after the transitional period in stable full term Small for Gestational Age (SGA) neonates.

DESIGN

Observational study.

SETTING

A tertiary care, perinatal centre in western Maharashtra, India.

PARTICIPANTS

Full term (37 to 41 weeks) small for gestational age (weight below 10th percentile for gestational age) infants who were born during the study period.

METHODS

RVO, LVO and SVC flows were measured by functional echocardiography on day 7 of life in stable full term SGA neonates from January 2011 to August 2011. Infants who required respiratory or cardiovascular support and intensive care unit admissions for any indication and those with a clinical suspicion of an infection within 48 hours after data collection were excluded from the study.

STATISTICAL ANALYSES

Unpaired t-test was used to compare SVC flow between symmetric and asymmetric SGA neonates.

MAIN OUTCOME MEASURE

Measurements of RVO, LVO and SVC in term SGA neonates on day 7 of life.

RESULTS

We performed measurements in 52 term SGA neonates with a median (range) birth weight of 2.190 (1.600-2.410) kg. Fifty two measurements were analyzed on day 7. The mean (SD) RVO, LVO and SVC flows were 255.59 (57.42) , 214.61 (52.04) and 126.28 (31.23) mL/kg/min.

CONCLUSION

This study provides RVO, LVO and SVC flow values in a cohort of stable term SGA neonates after the transitional period.

The fetal cardiovascular response to increased placental vascular impedance to flow determined with 4-dimensional ultrasound using spatiotemporal image correlation and virtual organ computer-aided analysis

OBJECTIVE

We sought to determine if increased placental vascular impedance to flow is associated with changes in fetal cardiac function using spatiotemporal image correlation and virtual organ computer-aided analysis.

STUDY DESIGN

A cross-sectional study was performed in fetuses with umbilical artery pulsatility index >95th percentile (abnormal [ABN]). Ventricular volume (end-systole, end-diastole), stroke volume, cardiac output (CO), adjusted CO, and ejection fraction were compared to those of 184 normal fetuses.

RESULTS

A total of 34 fetuses were evaluated at a median gestational age of 28.3 (range, 20.6-36.9) weeks. Mean ventricular volumes were lower for ABN than normal cases (end-systole, end-diastole) with a proportionally greater decrease for left ventricular volume (vs right). Mean left and right stroke volume, CO, and adjusted CO were lower for ABN (vs normal) cases. Right ventricular volume, stroke volume, CO, and adjusted CO exceeded the left in ABN fetuses. Mean ejection fraction was greater for ABN than normal cases. Median left ejection fraction was greater (vs right) in ABN fetuses.

CONCLUSION

Increased placental vascular impedance to flow is associated with changes in fetal cardiac function.

Transitional changes in cardiac and cerebral hemodynamics in term neonates at birth

OBJECTIVE

To describe cardiac function, cerebral regional oxygen saturation (rSO(2)), and cerebral blood flow (CBF) that correspond to changes in arterial oxygen saturation (SaO(2)) in normal term neonates immediately after birth and after the transition.

STUDY DESIGN

In this prospective observational study, cardiac function and cerebral hemodynamics were assessed by echocardiography and Doppler ultrasonography 3 times during the first 20 minutes after vaginal delivery, then again at 24-48 hours after delivery. Cerebral rSO(2) (by near-infrared spectroscopy) and preductal SaO(2) (by pulse oximetry) were assessed continuously.

RESULTS

In 20 neonates, SaO(2) increased progressively from 65% at 1 minute after birth to 97% at 17 minutes after birth. Cerebral rSO(2) increased from 47% at 1 minute to 83% at 8 minutes, then decreased progressively to 73% at 20 minutes. Middle cerebral artery mean velocity decreased from 34 cm/s at 7 minutes to 25 cm/s at 14 minutes. The patent ductus arteriosus (PDA) shunt was balanced at 5 minutes but became increasingly left to right. Left ventricular stroke volume was increased. Middle cerebral artery mean velocity demonstrated an inverse relationship with the PDA shunt. Further hemodynamic changes were noted on the posttransitional assessment.

CONCLUSION

After birth, ductal shunting rapidly changes from balanced to left to right, with a responsive increase in left ventricular stroke volume. Cerebral rSO(2) increases as SaO(2) rises during the first 8 minutes, subsequently, it decreases due to a drop in CBF and despite a further increase in SaO(2). The reduction in CBF is likely due to an increase in arterial O(2) content, PDA shunting, or both.

The methodology of Doppler-derived central blood flow measurements in newborn infants

Central blood flow (CBF) measurements are measurements in and around the heart. It incorporates cardiac output, but also measurements of cardiac input and assessment of intra- and extracardiac shunts. CBF can be measured in the central circulation as right or left ventricular output (RVO or LVO) and/or as cardiac input measured at the superior vena cava (SVC flow). Assessment of shunts incorporates evaluation of the ductus arteriosus and the foramen ovale. This paper describes the methodology of CBF measurements in newborn infants. It provides a brief overview of the evolution of Doppler ultrasound blood flow measurements, basic principles of Doppler ultrasound, and an overview of all used methodology in the literature. A general guide for interpretation and normal values with suggested cutoffs of CBFs are provided for clinical use.

Noninvasive assessment of the early transitional circulation in healthy term infants

BACKGROUND

The early neonatal circulatory transition usually occurs smoothly but occasionally it is incomplete or reverts to the fetal state of high pulmonary vascular resistance, resulting in significant neonatal morbidity.

OBJECTIVE

To define the normal values for echocardiographic parameters during the early transitional circulation in term infants.

METHODS

Two-dimensional, M-mode, pulsed and color flow Doppler echocardiography was used to assess healthy term infants in the first 4 h of life. Left and right ventricular outputs (LVO and RVO) and myocardial performance indices (MPI), left ventricular fractional shortening, end-systolic diameter and end-diastolic diameter, ductal size, shunt and peak velocities, tricuspid regurgitation and left pulmonary artery diastolic velocities were documented.

RESULTS

A total of 21 normal term infants were assessed with median gestation of 39 weeks, birth weight of 3,470 g and postnatal age of 3 h and 22 min. The median echocardiographic values were LVO 193 ml/kg/min, RVO 216 ml/kg/min, left MPI 0.41, right MPI 0.63, and fractional shortening 29%. The ductus was patent in all 21 infants with a median size of 2.3 mm; ductal flow was bidirectional in 86% with median peak left-to-right velocity of 1.07 m/s. The median left pulmonary artery diastolic velocity was 0.31 m/s and physiological tricuspid regurgitation was present in all infants.

CONCLUSION

This study defines normal values for echocardiographic measurements in healthy term infants during the first 4 h after birth. These normative data may be useful in early identification of infants with abnormal circulatory transition, allowing more rapid determination of cardiovascular dysfunction.

Shortening fraction of the right ventricle: a comparison between euploid and trisomy 21 fetuses at week 11 to week 13 and 6 days of gestation

OBJECTIVES

This study was designed to compare the first trimester shortening fraction of the right ventricle (SFRV) values between euploid fetuses and fetuses with trisomy 21.

METHODS

SFRV was measured in 58 first trimester fetuses between September 2008 and February 2010. The stored M-mode images were used to obtain the right ventricular diastolic diameter (RVDD) and right ventricular systolic diameter (RVSD) measurements offline.

RESULTS

The SFRV values were found to be significantly greater in the 9 fetuses with trisomy 21 as compared to the group of 49 euploid fetuses (mean: 48.6 mm; range: 36-56.25 mm vs mean: 34.11 mm; range: 22.73-43.48 mm) (p < 0.0001). The RVDD measurements were also found to be significantly greater in the fetuses with trisomy 21 than in the euploid fetuses (mean: 3.08 mm; range: 2.2-4.7 mm vs mean: 2.54 mm; range: 1.9-3.6 mm) (p = 0.03).There was no difference in the RVSD measurements between the two groups [mean: 1.56 mm; range: 1.2-2.3 mm (trisomy 21 fetuses) vs mean: 1.67 mm; range: 1.3-2.4 mm (euploid fetuses)] (p = 0.17).

CONCLUSIONS

The SFRV values in fetuses with trisomy 21 appear to be significantly greater than in the euploid fetuses. The RVDD also appears to be greater in fetuses with trisomy 21 than in the euploid fetuses.

Fetal cardiac dimensions at 14-40 weeks' gestation obtained using cardio-STIC-M

OBJECTIVES

To establish normative reference ranges of fetal cardiac dimensions derived from volume datasets acquired using spatiotemporal image correlation with M-mode display (cardio-STIC-M).

METHODS

A cross-sectional study was undertaken on singleton pregnancies with normal fetuses and accurate gestational ages. Cardio-STIC volume datasets were acquired by experienced operators using a high-resolution ultrasound machine; these were maneuvered to obtain a four chamber-view with exactly horizontal interventricular septum (IVS). Cardiac dimensions were measured in STIC-M-mode using 4D View software.

RESULTS

A total of 657 measurements, at a rate of between 15 and 37 per week, were obtained. Normal reference ranges for biventricular outer diameter, left and right ventricular inner diameter, left and right ventricular wall thickness, IVS thickness, left to right ventricular diameter ratio and left and right ventricular shortening fractions were constructed based on best-fit equations as a function of gestational age, fetal head circumference and biparietal diameter. Thirty-four volume datasets of abnormal fetal hearts were also separately assessed, many of which showed abnormal cardiac dimensions.

CONCLUSIONS

This is the first report on normal ranges of fetal cardiac dimensions constructed using the new cardio-STIC-M technology. Preliminary evaluation suggests that these reference ranges may be a useful tool in the assessment of fetal cardiac abnormalities.

Regulation of the Pulmonary Circulation in the Fetus and Newborn

During the development of the pulmonary vasculature in the fetus, many structural and functional changes occur to prepare the lung for the transition to air breathing. The development of the pulmonary circulation is genetically controlled by an array of mitogenic factors in a temporo-spatial order. With advancing gestation, pulmonary vessels acquire increased vasoreactivity. The fetal pulmonary vasculature is exposed to a low oxygen tension environment that promotes high intrinsic myogenic tone and high vasocontractility. At birth, a dramatic reduction in pulmonary arterial pressure and resistance occurs with an increase in oxygen tension and blood flow. The striking hemodynamic differences in the pulmonary circulation of the fetus and newborn are regulated by various factors and vasoactive agents. Among them, nitric oxide, endothelin-1, and prostaglandin I2 are mainly derived from endothelial cells and exert their effects via cGMP, cAMP, and Rho kinase signaling pathways. Alterations in these signaling pathways may lead to vascular remodeling, high vasocontractility, and persistent pulmonary hypertension of the newborn.

Left ventricle shortening fraction: a comparison between euploid and trisomy 21 fetuses in the first trimester

OBJECTIVES

Measurement of the shortening fraction of the left ventricle (SFLV) is an objective way to assess systolic performance. The aim of the study was to compare first trimester SFLV values in euploid fetuses to those in fetuses with trisomy 21.

METHODS

We measured SFLV in 56 fetuses from 11 weeks to 13 weeks 6 days. The left ventricular diastolic diameter (LVDD) and left ventricular systolic diameter (LVSD) were measured offline, and SFLV was calculated. The data were analyzed using Mann-Whitney U test.

RESULTS

We found a significant difference in the SFLV measurements between the group of 49 euploid fetuses and the 7 fetuses with trisomy 21 [38.00 (95% CI: 33.72-42.27) vs 49.93 (95% CI: 43.72-56.13)] (p < 0.05). There was also a significant difference in the nuchal translucency measurements between the two groups: 1.78 mm (95% CI: 1.08-2.48 mm) in the euploid population versus 5.06 mm (95% CI: 3.61-6.71 mm) in the fetuses with trisomy 21 (p < 0.05). There were no significant differences between the group of euploid fetuses and the group of trisomy 21 fetuses in the following parameters: CRL (chorionic villus sampling), LVDD and LVSD.

CONCLUSIONS

SFLV is a well-defined, simple measurement of systolic function of the fetal myocardium. SFLV values in fetuses with trisomy 21 appear to be significantly higher than in euploid fetuses.

A model for educational simulation of hemodynamic transitions at birth

Birth is characterized by swift and complex transitions in hemodynamic and respiratory variables. Unrecognized pathologies or incidents may quickly become fatal or cause permanent damage. This article introduces an essential component of an acute perinatal care simulator, namely a model for educational simulation of normal hemodynamic transitions seen during and shortly after birth. We explicitly formulate educational objectives and adapt a preexisting model for the simulation of neonatal cardiovascular physiology to include essential aspects of fetal hemodynamics. From the scientific literature, we obtain model parameters that characterize these aspects quantitatively. The fetal model is controlled by a time- and event-based script of changes occurring at birth, such as onset of breathing and cord clamping, and the transitory phase up to 24 h after birth. Comparison of simulation results with published target data confirms that realistic simulated hemodynamic vital signs are achieved.

Left and right ventricular myocardial performance index (Tei index) in very-low-birth-weight infants

This study presents a report of serial assessment of ventricular myocardial performance index (Tei index) in very-low-birth-weight (VLBW) infants. One hundred ninety-five VLBW infants, weighing <1,500 g, who were admitted to the neonatal intensive care units at Kakogawa Municipal Hospital between September 2000 and August 2004. Left ventricular (LV) and right ventricular (RV) Tei indexes were assessed consecutively from birth to day 28 in all VLBW infants using pulsed-Doppler echocardiography. The mean values of the LV Tei index rose rapidly from 3 to 12 h after birth and then fell significantly after 24 h. Those of the RV Tei index increased slightly from 3 to 12 h, then decreased drastically after 24 h. The LV Tei index was found to correlate inversely with LV output and LV ejection fraction in the early neonatal period, while the relationship between the LV Tei index and the LV E/A velocity ratio was not significant. The RV Tei index was inversely correlated with RV output. In conclusion, both of the ventricular Tei indexes in VLBW infants showed drastic and significant changes on the first to second day after birth.

The influence of thermal environment on pulmonary hemodynamic acclimation to extrauterine life in normal full-term neonates

OBJECTIVE

To assess chronological changes of pulmonary blood flow in response to ambient temperature load in normal full-term neonates.

METHODS

Group I (n=8) neonates were maintained at 25-26 degrees C for the first 24 h after birth, with Group II (n=7) at 32-33 degrees C. Left pulmonary artery flow volume (Vp) and ductus arteriosus diameter were measured at 2, 4, 6, 12, and 24 h using Doppler ultrasound. Core and peripheral temperatures, as a marker for cold stress, were also evaluated over the same time frame.

RESULTS

For Group I, Vp was steady for the first 6 h after birth before gradually decreasing. In contrast, Vp for Group II significantly decreased from 2-6 h, without later changes. At 6 h after birth in Group II, mean values of both Vp and ductus arteriosus diameter were significantly lower, whereas mean value of peripheral temperature was significantly higher than values in Group I (P<0.05).

CONCLUSION

Pulmonary blood flow in neonates placed at neutral ambient temperature stabilizes earlier than that of neonates placed at room temperatures. Changes of peripheral flow in response to ambient temperature load may be associated with decreased pulmonary blood flow through a left-to-right ductal shunt.

[Awareness: a problem in paediatric anaesthesia?]

Intraoperative awareness has been reported to occur in 0.8-5.0% of paediatric patients undergoing anaesthesia and, therefore, seems to be more common than in adults (incidence 0.1-0.2%). In adult patients, the consequences of intraoperative awareness are well known and can be severe, in children, however, they have not yet been adequately studied. The causes for intraoperative awareness can be divided into three broad categories: First, no or only a light anaesthetic is given on purpose, second, an insufficient dose of an anaesthetic is given inadvertently, third, there is equipment malfunction or the anaesthesiologist makes an error. Unfortunately, especially in young children, painful interventions are still performed without adequate analgesia, e.g. awake intubation or fracture manipulation under midazolam sedation alone. The key issue is, however, that pharmacokinetics and pharmacodynamics change enormously from the 500 g preterm baby to the adolescent patient. Adequate dosing is much more difficult in paediatric patients compared to standard adult surgical patients. Solid knowledge of the pharmacokinetic and pharmacodynamic characteristics of commonly used drugs in different paediatric age groups, as well as aiming for perfection in daily care will help to reduce the incidence of awareness. Methods for monitoring the depth of hypnosis, e.g. the bispectral index, will be used increasingly, at least in children above 1 year of age. In addition to clinical parameters, they will hopefully help to further reduce the incidence of intraoperative awareness.

Randomized trial of volume infusion during resuscitation of asphyxiated neonatal piglets

Despite its use, there is little evidence to support volume infusion (VI) during neonatal cardiopulmonary resuscitation (CPR). This study compares 5% albumin (ALB), normal saline (NS), and no VI (SHAM) on development of pulmonary edema and restoration of mean arterial pressure (MAP) during resuscitation of asphyxiated piglets. Mechanically ventilated swine (n=37, age: 8 +/- 4 d, weight: 2.2 +/- 0.7 kg) were progressively asphyxiated until pH <7.0, Paco2 >100 mm Hg, heart rate (HR) <100 bpm, and MAP <20 mm Hg. After 5 min of ventilatory resuscitation, piglets were randomized blindly to ALB, NS, or SHAM infusion. Animals were recovered for 2 h before euthanasia and lung tissue sampled for wet-to-dry weight ratio (W/D) as a marker of pulmonary edema. SHAM MAP was similar to VI during resuscitation. At 2 h post-resuscitation, MAP of SHAM (48 +/- 13 mm Hg) and ALB (43 +/- 19 mm Hg) was higher than NS (29 +/- 10 mm Hg; p=0.003 and 0.023, respectively). After resuscitation, SHAM piglets had less pulmonary edema (W/D: 5.84 +/- 0.12 versus 5.98 +/- 0.19; p=0.03) and better dynamic compliance (Cd) compared with ALB or NS (Cd: 1.43 +/- 0.69 versus 0.97 +/- 0.37 mL/cm H2O, p=0.018). VI during resuscitation did not improve MAP, and acute recovery of MAP was poorer with NS compared with ALB. VI was associated with increased pulmonary edema. In the absence of hypovolemia, VI during neonatal resuscitation is not beneficial.