Fetal cardiovascular physiology

Practical Evaluation of the Fetal Cardiac Function

The fetal heart adapts dynamically to nutrient and oxygen needs from all fetal organs. These continuous changes make it difficult to define normal/abnormal cardiac function based only on the evaluation of a few cycles. Many signs of fetal cardiac dysfunction have been suggested; however, very few can stand as true manifestations of cardiac deterioration, and none has emerged as a single reliable marker of cardiac dysfunction. It is the combination of abnormal findings that provides a more accurate assessment of the status of the fetal heart function.

A Multiscale Mathematical Model for the Fetal Blood Circulation of the Second Half of Pregnancy

Doppler ultrasound is a commonly used method to assess hemodynamics of the fetal cardiovascular system and to monitor the well-being of the fetus. Indices based on the velocity profile are often used for diagnosis. However, precisely linking these indices to specific underlying physiology factors is challenging. Several influences, including wave reflections, fetal growth, vessel stiffness, and resistance distal to the vessel, contribute to these indices. Understanding these data is essential for making informed clinical decisions. Mathematical models can be used to investigate the relation between velocity profiles and physiological properties. This study presents a mathematical model designed to simulate velocity wave propagation throughout the fetal cardiovascular system, facilitating the assessment of factors influencing velocity-based indices. The model combines a one-fiber model of the heart with a 1D wave propagation model describing the larger vessels of the circulatory system and a lumped parameter model for the microcirculation. Fetal growth from 20 to 40 weeks of gestational age is incorporated by adjusting cardiac and circulatory parameter settings according to scaling laws. The model's results, including cardiac function, cardiac output distribution, and volume distribution, show a good agreement with literature studies for a growing healthy fetus from 20 to 40 weeks. In addition, Doppler indices are simulated in various vessels and agree with literature as well. In conclusion, this study introduces a novel closed-loop 0D-1D mathematical model that has been verified against literature studies. This model offers a valuable platform for analyzing factors influencing velocity-based indices in the fetal cardiovascular system.

Prediction of fetal growth restriction and small for gestational age by ultrasound cardiac parameters

OBJECTIVE

Prediction of fetal growth restriction (FGR) and small of gestational age (SGA) infants by using various ultrasound cardiac parameters in a logistic regression model.

METHODS

In this retrospective study we obtained standardized ultrasound images of 357 fetuses between the 20th and 39th week of gestation, 99 of these fetuses were between the 3rd and 10th growth percentile, 61 smaller than 3rd percentile and 197- appropriate for gestational age over the 10th percentile (control group). Several cardiac parameters were studied. The cardiothoracic ratio and sphericity of the ventricles was calculated. A binary logistic regression model was developed for prediction of growth restriction using the cardiac and biometric parameters.

RESULTS

There were noticeable differences between the control and study group in the sphericity of the right ventricle (p = 0.000), left and right longitudinal ventricle length (pright = 0.000, pleft = 0.000), left ventricle transverse length (p = 0.000), heart diameter (p = 0.002), heart circumference (p = 0.000), heart area (p = 0.000), and thoracic diameter limited by the ribs (p = 0.002). There was no difference of the cardiothoracic ratio between groups. The logistic regression model achieved a prediction rate of 79.4 % with a sensitivity of 74.5 % and specificity of 83.2 %.

CONCLUSION

The heart of growth restricted infants is characterized by a more globular right ventricle, shorter ventricle length and smaller thorax diameter. These parameters could improve prediction of FGR and SGA.

The gut microbiome as a modulator of arterial function and age-related arterial dysfunction

The arterial system is integral to the proper function of all other organs and tissues. Arterial function is impaired with aging, and arterial dysfunction contributes to the development of numerous age-related diseases, including cardiovascular diseases. The gut microbiome has emerged as an important regulator of both normal host physiological function and impairments in function with aging. The purpose of this review is to summarize more recently published literature demonstrating the role of the gut microbiome in supporting normal arterial development and function and in modulating arterial dysfunction with aging in the absence of overt disease. The gut microbiome can be altered due to a variety of exposures, including physiological aging processes. We explore mechanisms by which the gut microbiome may contribute to age-related arterial dysfunction, with a focus on changes in various gut microbiome-related compounds in circulation. In addition, we discuss how modulating circulating levels of these compounds may be a viable therapeutic approach for improving artery function with aging. Finally, we identify and discuss various experimental considerations and research gaps/areas of future research.

Prenatal Diagnosis of Fetal Heart Failure

Fetal heart failure (FHF) is a condition of inability of the fetal heart to deliver adequate blood flow for tissue perfusion in various organs, especially the brain, heart, liver and kidneys. FHF is associated with inadequate cardiac output, which is commonly encountered as the final outcome of several disorders and may lead to intrauterine fetal death or severe morbidity. Fetal echocardiography plays an important role in diagnosis of FHF as well as of the underlying causes. The main findings supporting the diagnosis of FHF include various signs of cardiac dysfunction, such as cardiomegaly, poor contractility, low cardiac output, increased central venous pressures, hydropic signs, and the findings of specific underlying disorders. This review will present a summary of the pathophysiology of fetal cardiac failure and practical points in fetal echocardiography for diagnosis of FHF, focusing on essential diagnostic techniques used in daily practice for evaluation of fetal cardiac function, such as myocardial performance index, arterial and systemic venous Doppler waveforms, shortening fraction, and cardiovascular profile score (CVPs), a combination of five echocardiographic markers indicative of fetal cardiovascular health. The common causes of FHF are reviewed and updated in detail, including fetal dysrhythmia, fetal anemia (e.g., alpha-thalassemia, parvovirus B19 infection, and twin anemia-polycythemia sequence), non-anemic volume load (e.g., twin-to-twin transfusion, arteriovenous malformations, and sacrococcygeal teratoma, etc.), increased afterload (intrauterine growth restriction and outflow tract obstruction, such as critical aortic stenosis), intrinsic myocardial disease (cardiomyopathies), congenital heart defects (Ebstein anomaly, hypoplastic heart, pulmonary stenosis with intact interventricular septum, etc.) and external cardiac compression. Understanding the pathophysiology and clinical courses of various etiologies of FHF can help physicians make prenatal diagnoses and serve as a guide for counseling, surveillance and management.

Evaluation of Fetal Cardiac Function in Maternal Gestational Diabetes Mellitus by Speckle-Tracking Echocardiography

OBJECTIVES

Gestational diabetes mellitus (GDM) is the most common metabolic disease that occurs during pregnancy and may result in fetal cardiac dysfunction. Our study aimed to assess the cardiac function in fetuses of mothers with GDM by a quantitative analysis software based on speckle-tracking echocardiography.

METHODS

Forty-nine fetuses exposed to GDM and 50 normal fetuses were enrolled, and fetal echocardiography were performed and analyzed in this prospective cross-sectional study. We compared cardiac systolic function between the two groups using fetal cardiac quantitative analysis software.

RESULTS

In the GDM group, left ventricular (24 ± 4 versus 28 ± 4, P < .001) and right ventricular global longitudinal strain (23 ± 4 versus 26 ± 4, P = .002) and right ventricular free wall strain (26 ± 6 versus 29 ± 5, P = .006) were significantly lower compared with the control group, whereas there was no significant difference in global spherical index (1.2 ± 0.1 versus 1.2 ± 0.1, P = .425). Additionally, 24-segment transverse fraction shortening of the right ventricle was more impaired than the left, and the segments with reduced fraction shortening were mainly located in the mid and apical sections of the right ventricle, and midsection of the left ventricle.

CONCLUSION

Fetuses exposed to GDM may have cardiac dysfunction before the onset of cardiac morphologic abnormalities, and the right ventricle is more vulnerable than the left during fetal development.

Fetal and Neonatal Anesthesia

Anesthesia for fetal and neonatal surgery requires subspecialized knowledge and expertise. Attention to important anatomic, physiologic, and metabolic differences seen in pregnancy and at birth are essential for the optimal care of these patients. Thorough preoperative evaluations tailored intraoperative strategies and careful postoperative management are critical when devising the anesthetic approach for each of these cases.

Assessment of left ventricular function by spatio-temporal image correlation in fetuses with fetal growth restriction

AIM

To compare the evaluation of left ventricular function by spatio-temporal image correlation (STIC) between fetal growth restriction (FGR) fetuses and normal fetuses.

METHODS

Forty-two FGR fetuses and 50 normal fetuses with gestational age ranging from 28 to 35 weeks, were chosen for the study group and control group, respectively. The fetal heart was acquired using the STIC modality, beginning with a four-chamber view. A 7.5-12.5 s acquisition time and 20-35°angle of the acquisition were used for the acquisition. The resulting STIC dataset was saved for offline analysis. Ventricular volumes were measured using the Virtual Organ Computer-aided Analysis (VOCAL) mode, where the observer defines the contours of the ventricle and traces the endocardia. Stroke volume (SV) = end diastolic volume (EDV)-end systolic volume (ESV) and ejection fraction (EF) = SV/EDV × 100%. The data of the two groups were analyzed.

RESULTS

(1) SV increased with fetal growth in both groups and was positively correlated with gestational age (p < .01), whereas EF remained constant throughout gestation and had no correlation with gestational age (p > .05). (2) There was no difference found in EF between the two groups, (p > .05), SV was significantly lower in FGR group than those in the normal group (p < .01).

CONCLUSION

The STIC is a precise method for calculating fetal ventricular volume changes and functions. Reduced SV occurred at the initial stage of fetal deterioration before the discovery of abnormal EF in FGR fetuses, indicating cardiac dysfunction. SV could be a sensitive indicator of cardiac dysfunction. The use of EF to assess fetal cardiac function is not perfect.

Impact of the Addition of a Centrifugal Pump in a Preterm Miniature Pig Model of the Artificial Placenta

The recent demonstration of normal development of preterm sheep in an artificial extrauterine environment has renewed interest in artificial placenta (AP) systems as a potential treatment strategy for extremely preterm human infants. However, the feasibility of translating this technology to the human preterm infant remains unknown. Here we report the support of 13 preterm fetal pigs delivered at 102 ± 4 days (d) gestation, weighing 616 ± 139 g with a circuit consisting of an oxygenator and a centrifugal pump, comparing these results with our previously reported pumpless circuit (n = 12; 98 ± 4 days; 743 ± 350 g). The umbilical vessels were cannulated, and fetuses were supported for 46.4 ± 46.8 h using the pumped AP versus 11 ± 13 h on the pumpless AP circuit. Upon initiation of AP support on the pumped system, we observed supraphysiologic circuit flows, tachycardia, and hypertension, while animals maintained on a pumpless AP circuit exhibited subphysiologic flows. On the pumped AP circuit, there was a progressive decline in umbilical vein (UV) flow and oxygen delivery. We conclude that the addition of a centrifugal pump to the AP circuit improves survival of preterm pigs by augmenting UV flow through the reduction of right ventricular afterload. However, we continued to observe the development of heart failure within a matter of days.

Retrograde flow in aortic isthmus in normal and fetal heart disease by principal component analysis and computational fluid dynamics

OBJECTIVES

Reverse flow Retrograde flow (RF) of blood in the aortic isthmus can be observed in different types of fetal heart disease (FHD), including abnormalities in heart structure and function. This study sought to investigate the relationship between RF and blood flow parameters, and develop a computational fluid dynamics (CFD) model to understand the mechanisms underlying this observation.

MATERIAL AND METHODS

A total of 281 fetuses (gestational age [GA] 26.6±.3 weeks) with FHD and 2803 normal fetuses (GA: 26.1±.1 weeks) by fetal echocardiography collected from May 2016 to December 2018. Principal component analysis (PCA) was performed to find the relationship and the CFD model reconstructed from 3D/4D spatio-temporal image correlation (STIC) images to simulate hemodynamics.

RESULTS

There was a significant difference in the percentages of RF between the study (80/201 (39%)) and control (29/2803 (1%)) groups (p < 0.05). The RF occur when the aorta flow rate (left heart) is reduced to 60% by CFD stimulation. Pearson correlation analysis showed significant correlations between flow rate and wall shear stress(WSS) (r = .883, p = 0.047) variables at the AI.

CONCLUSION

Volumetric flow rate of AO or left heart was the main component of the cause of RF. The hemodynamics of the cardiovascular system have highly complex behavior hinge on the turbulent nature of circulating blood flow.

Evaluation of right side foetal myocardial performance index in pregestational and gestational diabetes mellitus

The aim of our study is to investigate the myocardial performance index (MPI) of the right side of the foetal heart in pregestational and gestational diabetes mellitus and to compare it with non-diabetic pregnancies. This prospective cross-sectional study was conducted between August 2018 and March 2019 at Kanuni Sultan Suleyman Research and Training Hospital. Women with pregestational or gestational diabetes mellitus at 24-34 weeks of gestation were included in the study and non-diabetic pregnant women were included as the control group. MPI of the right side of the foetal heart were evaluated and compared between the groups. A total of 65 pregestational or gestational diabetic patients and 65 non-diabetic patients were included in the study. Isovolumetric contraction time and isovolumetric relaxation time values were significantly longer in the diabetic group (p < .001). Ejection time values were significantly shorter in the diabetic group (p < .001). MPI values were significantly higher in the diabetic group than the non-diabetic group (p < .001). In conclusion, MPI of the right side of the foetal heart is significantly higher in pregestational and gestational diabetes than in the non-diabetic group.IMPACT STATEMENTWhat is already known on this subject? Gestational diabetes mellitus causes foetal cardiomyopathy and foetal diastolic dysfunction. Myocardial performance index (MPI) is a non-invasive, Doppler-derived myocardial performance assessment that is independent of both heart rate and ventricular anatomy.What do the results of this study add? MPI of the right side of the foetal heart was significantly higher in pregestational and gestational diabetes than in the non-diabetic group. There was no difference in right ventricular MPI between pregestational and gestational groups in diabetic pregnancies, and between insulin using and not insulin using groups.What are the implications of these findings for clinical practice and/or further research? Our study results are promising. MPI of the right side of the foetal heart is significantly higher in pregestational and gestational diabetes than in the non-diabetic group. Prospective cohort studies evaluating serial MPI and evaluating by postpartum foetal echocardiography are needed to evaluate possible adverse effects of diabetes on foetal cardiac functions.

Anesthesia for Maternal-Fetal Interventions: A Consensus Statement From the American Society of Anesthesiologists Committees on Obstetric and Pediatric Anesthesiology and the North American Fetal Therapy Network

Maternal-fetal surgery is a rapidly evolving specialty, and significant progress has been made over the last 3 decades. A wide range of maternal-fetal interventions are being performed at different stages of pregnancy across multiple fetal therapy centers worldwide, and the anesthetic technique has evolved over the years. The American Society of Anesthesiologists (ASA) recognizes the important role of the anesthesiologist in the multidisciplinary approach to these maternal-fetal interventions and convened a collaborative workgroup with representatives from the ASA Committees of Obstetric and Pediatric Anesthesia and the Board of Directors of the North American Fetal Therapy Network. This consensus statement describes the comprehensive preoperative evaluation, intraoperative anesthetic management, and postoperative care for the different types of maternal-fetal interventions.

Harnessing Machine Intelligence in Automatic Echocardiogram Analysis: Current Status, Limitations, and Future Directions

Echocardiography (echo) is a critical tool in diagnosing various cardiovascular diseases. Despite its diagnostic and prognostic value, interpretation and analysis of echo images are still widely performed manually by echocardiographers. A plethora of algorithms has been proposed to analyze medical ultrasound data using signal processing and machine learning techniques. These algorithms provided opportunities for developing automated echo analysis and interpretation systems. The automated approach can significantly assist in decreasing the variability and burden associated with manual image measurements. In this paper, we review the state-of-the-art automatic methods for analyzing echocardiography data. Particularly, we comprehensively and systematically review existing methods of four major tasks: echo quality assessment, view classification, boundary segmentation, and disease diagnosis. Our review covers three echo imaging modes, which are B-mode, M-mode, and Doppler. We also discuss the challenges and limitations of current methods and outline the most pressing directions for future research. In summary, this review presents the current status of automatic echo analysis and discusses the challenges that need to be addressed to obtain robust systems suitable for efficient use in clinical settings or point-of-care testing.

Evaluation of fetal cardiac function in pregnancies with well-controlled gestational diabetes

OBJECTIVE

To evaluate fetal ventricular diastolic function in pregnancies of women with gestational diabetes (GD), to determine whether minimal anomalies of glucose metabolism may influence fetal cardiac function.

STUDY DESIGN

Fetal ventricular filling time was measured by transabdominal ultrasound in singleton pregnancies between 34 and 37 weeks of gestation. We used a measurement which consists in the ratio between the diastolic time and the whole cardiac cycle time.

RESULTS

The study included 35 women with a GD and 217 non-diabetic. Right ventricular filling time (RVFT) was significantly lower in the GD group (mean of RVFT = 39.2 ± 4.4 vs 43.6 ± 4.6; p  <  0.01). Likewise, left ventricular filling time (LVFT) was shorter in the GD group compared to the non-GD group, though the difference was not significant (mean of LVFT = 43.6 ± 4.6 vs 44.6 ± 5.5; p  = 0.33).

CONCLUSIONS

Fetal right cardiac function is altered also in pregnancies where gestational diabetes is well controlled.

Molecular and Mechanical Mechanisms Regulating Ductus Arteriosus Closure in Preterm Infants

Failure of ductus arteriosus closure after preterm birth is associated with significant morbidities. Ductal closure requires and is regulated by a complex interplay of molecular and mechanical mechanisms with underlying genetic factors. In utero patency of the ductus is maintained by low oxygen tension, high levels of prostaglandins, nitric oxide and carbon monoxide. After birth, ductal closure occurs first by functional closure, followed by anatomical remodeling. High oxygen tension and decreased prostaglandin levels mediated by numerous factors including potassium channels, endothelin-1, isoprostanes lead to the contraction of the ductus. Bradykinin and corticosteroids also induce ductal constriction by attenuating the sensitivity of the ductus to PGE2. Smooth muscle cells of the ductus can sense oxygen through a mitochondrial network by the role of Rho-kinase pathway which ends up with increased intracellular calcium levels and contraction of myosin light chains. Anatomical closure of the ductus is also complex with various mechanisms such as migration and proliferation of smooth muscle cells, extracellular matrix production, endothelial cell proliferation which mediate cushion formation with the interaction of blood cells. Regulation of vessel walls is affected by retinoic acid, TGF-β1, notch signaling, hyaluronan, fibronectin, chondroitin sulfate, elastin, and vascular endothelial cell growth factor (VEGF). Formation of the platelet plug facilitates luminal remodeling by the obstruction of the constricted ductal lumen. Vasa vasorum are more pronounced in the term ductus but are less active in the preterm ductus. More than 100 genes are effective in the prostaglandin pathway or in vascular smooth muscle development and structure may affect the patency of ductus. Hemodynamic changes after birth including fluid load and flow characteristics as well as shear forces within the ductus also stimulate closure. Current pharmacological treatment for the closure of a patent ductus is based on the blockage of the prostaglandin pathway mainly through COX or POX inhibition, albeit with some limitations and side effects. Further research for new agents aiming ductal closure should focus on a clear understanding of vascular biology of the ductus.

Prenatal Identification of Restrictive and Non-restrictive Ventricular Septal Defects Based on End-Systolic Flow Patterns in the Fetal Aortic Isthmus

Fetuses with large ventricular septal defects (VSDs) must be closely monitored during the perinatal period. Intrauterine assessment of size of septal defects with bidimensional echocardiography are unreliable. The objective of the present study is to document the contribution of flow pattern analysis in the fetal aortic isthmus for prenatal identification of large non-restrictive VSDs requiring immediate postnatal attention. We conducted a cross-sectional retrospective study of Doppler recordings from patients referred to our Fetal Cardiology Unit and diagnosed with one or multiple VSDs from January 2006 to November 2015. Three groups were defined: (1) large non-restrictive VSDs (n = 11) with postnatal cardiac failure (2) small restrictive VSDs (n = 28) asymptomatic, and (3) absence of cardiac abnormality (n = 66). The Isthmic end-Systolic Index (ISI) was computed to quantify aortic isthmus flow and compared between the three groups. Fetuses with restrictive VSD and control group showed similar ISI: stable at 0.20 ± 0.01 up to 27 weeks of gestation and dropping later due to the fall of end-systolic velocities in the aortic isthmus. By 35 weeks, a brief end-systolic retrograde flow was present, associated with a further fall of ISI down to -0.26 ± 0.05. In contrast, ISI of fetuses with large non-restrictive VSDs were unchanged throughout gestation (0.18 ± 0.06), becoming significantly higher during the last weeks of gestation compared to the two other groups (p < 0.001). In fetuses with VSDs, the ISI measurement from the aortic isthmus Doppler flow during the second half of gestation is a reliable predictor of a large non-restrictive defect with risk of major postnatal clinical impact.

Prenatal sonographic markers of the outcome in fetuses with bronchopulmonary sequestration

PURPOSE

To evaluate the prenatal sonographic predictive markers of the outcome in fetuses with bronchopulmonary sequestration (BPS).

METHODS

BPS size and diameter of the feeding artery (FA) were measured prenatally and postnatally. Velocity of the FA and the left ventricular-modified myocardial performance index (LV mod-MPI) were also evaluated prenatally.

RESULTS

Forty-seven women were included in the study. Mean gestational age, mass size, diameter and velocity of the FA, and LV mod-MPI at prenatal diagnosis were 23.5 ± 2.2 weeks, 3.6 ± 8.3 cm, 2.3 ± 0.6 mm, 46.6 ± 15.4 cm/s, and 0.46 ± 0.06, respectively. Mean mass diameter and FA diameter measured on postnatal CT examinations were 3.8 ± 1.0 cm and 2.3 ± 0.7 mm, respectively. Five patients had respiratory symptoms after birth. Twenty children (43%) underwent or were scheduled to undergo mass excision, and the remaining 27 (57%) were doing well without any intervention. There was no neonatal death. LV mod-MPI at diagnosis, the FA diameter after birth and the serial change in the FA size were significantly associated with postnatal mass excision.

CONCLUSION

The FA diameter and LV mod-MPI may be additional markers for predicting whether fetuses with BPS should undergo mass excision in early childhood or conservative care.

Assessment of fetal right ventricular myocardial performance index changes following intrauterine transfusion

INTRODUCTION

Severe fetal anemia may cause cardiac ischemia, reduced contractility, and dysfunction. The purpose of our study is to evaluate right ventricular myocardial performance index (MPI) before and after intrauterine transfusion (IUT) in patients who underwent this procedure because of fetal anemia due to Rh-D alloimmunization.

MATERIALS AND METHODS

This prospective cohort study was conducted between January 2018 and June 2019 at Kanuni Sultan Suleyman Research and Training Hospital, Istanbul, Turkey. The pregnant women who were applied IUT because of fetal anemia due to Rh-D alloimmunization in our perinatology clinic were included in the study. Fetal right ventricular MPI before and 24 h after IUT were evaluated.

RESULTS

A total of 28 IUTs were performed in 17 pregnant women during the study period. The isovolumetric contraction time (ICT) and isovolumetric relaxation time (IRT) values measured before IUT, were found to be significantly longer compared to the ICT and IRT values measured after IUT. The MPI values measured after transfusion was found to be higher than before transfusion.

CONCLUSIONS

The fetal right ventricular MPI increases 24 h after IUT. This increase in the right ventricular MPI might be used as a marker for predicting adverse fetal outcomes following IUT.

Utility of the modified myocardial performance index in growth-restricted fetuses

OBJECTIVES

The modified myocardial performance index (Mod-MPI) can be used to assess myocardial function. Fetal growth restriction can affect fetal myocardial function, thereby altering the Mod-MPI. The results of previous studies on the utility of the Mod-MPI in growth-restricted fetuses are conflicting. The aim of this study was to calculate the left modified-MPI in growth-restricted fetuses and to compare the results with those of healthy fetuses.

METHODS

This was a prospective cross-sectional case-control study. In total, 40 women with growth-restricted fetuses and 40 women with fetuses of normal weight (controls) at 29-39 gestational weeks were enrolled in the study. An experienced obstetrician calculated the Mod-MPI for each fetus. Women with systemic diseases or fetuses with chromosomal/structural abnormalities were excluded from the study. The results of Mod-MPI measurements of the two groups were compared.

RESULTS

The mean single deepest vertical pocket (SDVP) of amniotic fluid, estimated fetal weight (EFW), and isovolumetric relaxation time (IRT) was significantly lower in the fetal growth restriction (FGR) group as compared with these parameters in the control group (P < .05). The uterine artery (UtA) pulsatility index (PI) was significantly higher in the FGR group as compared with that in the control group (P < .05). There were six cases of absent end-diastolic flow (AED) in the FGR group. There were no statistically significant between-group differences in the Mod-MPI, isovolumetric contraction time (ICT), and ejection time (ET) (P > .05). There was also no statistically significant correlation between the Mod-MPI in the fetuses with AED and the control group for Mod-MPI (P > .05).

CONCLUSION

The utility of the Mod-MPI in FGR remains unclear. Future studies with larger populations are needed to determine the utility of the Mod-MPI as a predictor of cardiac compromise in FGR.

Myocardial function in fetuses with lower urinary tract obstruction: Is there a cardiac remodeling effect due to renal damage?

OBJECTIVES

Cardiac remodeling due to renal dysfunction may have an impact on myocardial function (MF) of fetuses with lower urinary tract obstruction (LUTO). The aim was to identify possible differences in MF in LUTO fetuses compared with healthy controls and to look for interactions between urine biochemistry and MF indices.

METHODS

This is a cohort study consisting of 31 LUTO fetuses and 45 healthy controls. Subgroups were generated according to intrauterine therapy (group 1: LUTO after therapy, group 2: LUTO without therapy at the time of examination, and group 3: controls). MF indices were measured using pulsed wave tissue Doppler imaging and M-mode. Furthermore, results of fetal urine biochemistry were gathered retrospectively.

RESULTS

Among other findings, right ventricular (RV) e'/a' ratio was lower in group 1 compared with group 3 (p = .050). According to gestational age (GA) level-dependent analysis, RV isovolumetric relaxation time was significantly longer in group 2 compared with group 1 and group 3 at GA level 1 (19 wk of gestation). A significant positive correlation between RV e'/a' ratio and β-2-microglobulin as well as α-1-microglobulin and potassium could be observed.

CONCLUSION

We observed differences in MF and an association between ventricular filling pattern and renal protein secretion in LUTO fetuses. This can be interpreted as a sign of intrauterine cardiac remodeling.

Cardiac function and dysfunction in the fetus

Evaluation of fetal cardiac function is one of the most important components of fetal echocardiography. Fetal cardiac dysfunction is closely linked to risk of intrauterine fetal demise, in many, but not all cases is indicative of worse postnatal prognosis and may prompt the use of medications or interventions to optimize outcomes. There may be implications for termination versus continuation of pregnancy, an indication for early delivery, a change in location and even mode of delivery. In extreme cases, fetal cardiac dysfunction may prompt prenatal or early neonatal listing for cardiac transplantation. There are several important differences between the fetal and postnatal circulatory physiology which affect echocardiographic assessment of cardiac dysfunction. In this review, we examine the echocardiographic findings according to their underlying pathophysiology with reference to common causes.

What to do if A + B doesn't work

The majority of newborn resuscitations require very little beyond simple airway management and assisted ventilation. If cardiovascular collapse is serious enough to warrant additional support, resuscitation algorithms recommend moving to chest compressions and then on to medications and possibly volume replacement if vital signs remain marginal or absent. The evidence base upon which this part of the neonatal resuscitation algorithm is structured is sparse. Chest compressions and medications are rare interventions that do not lend themselves easily to clinical trials. Slowly but surely, however, the genesis of an empirical evidence base for this part of the algorithm is beginning to appear.

Patent ductus arteriosus: The physiology of transition

The transition from intrauterine to extrauterine life represents a critical phase of physiological adaptation which impacts many organ systems, most notably the heart and the lungs. The majority of term neonates complete this transition without complications; however, dysregulation of normal postnatal adaptation may lead to acute cardiopulmonary instability, necessitating advanced intensive care support. Although not as well appreciated as changes in vascular resistances, the shunt across the DA plays a crucial physiologic role in the adaptive processes related to normal transitional circulation. Further, we describe key differences in the behavior of the ductal shunt during transition in preterm neonates and we postulate mechanisms through which the DA may modulate major hemodynamic complications during this vulnerable period. Finally, we describe the conditions in which preservation of ductal patency is a desired clinical goal and we discuss clinical factors that may determine adequate balance between pulmonary and systemic circulation.

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.

Echocardiographic Evaluation of Transitional Circulation for the Neonatologists

The hemodynamic changes during the first few breaths after birth are probably the most significant and drastic adaptation in the human life. These changes are critical for a smooth transition of fetal to neonatal circulation. With the cord clamping, lungs take over as the source of oxygenation from placenta. A smooth transition of circulation is a complex mechanism and primarily depends upon the drop in pulmonary vascular resistance (PVR) and increase in systemic vascular resistance (SVR). Understanding the normal transition physiology and the adverse adaptation is of utmost importance to the clinicians looking after neonates. It may have a significant influence on the presentation of congenital heart defects (CHDs) in infants. Bedside echocardiography may help in understanding the transition physiology, especially the hemodynamic changes and shunting across ductus arteriosus and foramen ovale, and it may play an important role in making judicious clinical decisions based upon the altered physiology.

Novel Technique for Measurement of Fetal Right Myocardial Performance Index Using Dual Gate Pulsed-Wave Doppler

OBJECTIVES

To evaluate the reproducibility of the fetal right myocardial performance index determined by simultaneous recording of inflow and outflow using a dual gate pulsed-wave Doppler (DD).

METHODS

This was a prospective study of 39 normal singleton fetuses. Two experienced operators each measured the right myocardial performance index in three ways, twice: (1) separate recording of the inflow and outflow using single-gate pulsed-wave Doppler (PD), (2) simultaneous recordings of the inflow and outflow using tissue Doppler (TD), and (3) simultaneous recordings of the inflow and outflow using DD. Intra- and interoperator reproducibility were assessed with intraclass correlation coefficients. The measurements from all three methods taken by the more experienced operator were compared using Bland-Altman plots and mean differences.

RESULTS

For both operators, intra-operator reproducibility was the highest when using DD, followed by PD, and TD. Interoperator agreement was the highest for PD measurements, followed by DD, and TD. The smallest mean difference was between the PD and DD measurements by the more experienced operator. There was a positive correlation between PD and DD values (r = 0.369, P < .001).

CONCLUSIONS

Dual gate pulsed-wave Doppler may be an effective alternative to the PD or TD methods, and can separately evaluate systolic and diastolic myocardial function.

The Aortic Isthmus: A Significant yet Underexplored Watershed of the Fetal Circulation

The aortic isthmus (AoI) is a unique fetal watershed with a waveform reflecting its complex haemodynamic physiology. The systolic component represents left and right ventricular systolic ejection, and the diastolic component represents comparative downstream vascular impedance between the brachiocephalic and subdiaphragmatic fetal circulations. Several indices have been devised to quantify different components of the waveform, including the pulsatility index, resistance index, isthmic flow index, and recently the isthmic systolic index. There have been promising preliminary studies applying these indices to both cardiac (congenital) and extracardiac pathologies, including intrauterine growth restriction and twin-twin transfusion syndrome. However, the waveform's multifactorial origin has proven to be challenging, and the difficulty in separating various components of the waveform could explain that AoI evaluation does not have a clear clinical utility. Further research is underway to realise the full potential of this vessel in fetal cardiac and haemodynamically compromised pathological conditions. In this review article we outline the physiological origin of this Doppler waveform, describe in detail the various published indices, summarise the published literature to date, and finally outline potential future research and hopefully clinical applications.

Cardiac Physiology of Pregnancy

Although the physiology of the heart and vascular system has not changed, there are many things we have learned and are still learning today. Research related to heart adaptations during pregnancy has been performed since the 1930s. Since the mid-1950s, researchers began to look at changes in the maternal cardiovascular system during exercise while pregnant. Research related to exercise during pregnancy and offspring heart development began and has continued since the 1970s. We will review the normal female cardiovascular system adaptations to pregnancy in general. Additionally, topics related to maternal cardiac adaptations to pregnancy during acute exercise, as well as the chronic conditioning response from exercise training will be explored. Since physical activity during pregnancy influences fetal development, the fetal cardiac development will be discussed in regards to acute and chronic maternal exercise. Similarly, the influence of various types of maternal exercise on acute and chronic fetal heart responses will be described. Briefly, the topics related to how and if there is maternal-fetal synchrony will be explained. Lastly, the developmental changes of the fetal cardiovascular system that persist after birth will be explored. Overall, the article will discuss maternal cardiac physiology related to changes with normal pregnancy, and exercise during pregnancy, as well as fetal cardiac physiology related to changes with normal development, and exercise during pregnancy as well as developmental changes in offspring after birth.

Automated cardiac time interval measurement for Modified Myocardial Performance Index calculation of right ventricle

The Modified Myocardial Performance Index (Mod-MPI) has sparked great interest as a parameter for fetal cardiac function assessment. However, measurement of this index requires expertise and its clinical application might be limited, owing to its poor repeatability. Research groups have been investigating left Mod-MPI (that is, Mod-MPI from left ventricle valve events), and an automated algorithm has been developed for left Mod-MPI calculation in our previous study. Right MPI is also important as it becomes abnormal earlier than left MPI in some pathologies; however, for use across the gestational age spectrum, it requires two-image acquisition. This paper presents an automated method to detect valve movements during atrioventricular outflow and ventricular inflow and to further calculate the time intervals required for right MPI calculation. Ninety pulsed-wave Doppler ultrasound images of the right ventricle in fetuses, forty-five showing outflow and forty-five inflow, were analyzed to automatically detect the valve clicks generated by tricuspid valve movement in inflow waves, and pulmonary valve movement in outflow waves. The morphological characteristics of waves were combined with intensity information to locate clicks. This automated method can detect valve movement events with a high positive predictive value (96.20-98.96%) and sensitivity (97.95-100.00%), using manual annotation from an expert ultrasonographer as the gold standard for evaluation.

The Natural History of Atrioventricular Valve Regurgitation Throughout Fetal Life in Patients with Atrioventricular Canal Defects

Atrioventricular valve regurgitation (AVVR) influences morbidity and mortality in the atrioventricular canal defect (AVC). Fetal cardiac structures are subject to hemodynamic changes, as well as growth and maturation during gestation, which may alter the degree of AVVR and affect prognosis. We sought to investigate the frequency of change in degree of AVVR documented by fetal echocardiography (echo) between different periods of gestational age. Subjects with AVC seen in the Fetal Heart Program between January 2008 and September 2010 were identified. Degree of AVVR was assessed by color Doppler imaging and categorized as Grade 0 (no AVVR), Grade 1 (hemodynamically insignificant AVVR = trivial or mild), and Grade 2 (hemodynamically important AVVR = ≥moderate). Levels of AVVR between periods were compared. Forty-three fetuses were analyzed. Overall, 60% had no change, 14% had a decrease, and 26% had an increase in AVVR grade. Two fetuses progressed from Grade 0 or 1 to Grade 2, while one fetus decreased from Grade 2 to Grade 0. Trisomy 21 and heterotaxy syndrome were not risk factors for AVVR progression. Transitional and incomplete canal defects may be more susceptible to AVVR progression. Sixty percent of fetuses with AVC will not exhibit progression of AVVR between the second and third trimesters of gestation. In those who exhibit change, it is most often within a hemodynamically insignificant range between none and mild regurgitation (Grades 0 and 1). These findings have implications for the counseling, follow-up, and delivery plans of the fetus with AVC defect.

Monitoring intrahepatic cholestasis of pregnancy using the fetal myocardial performance index: a cohort study

OBJECTIVE

To investigate use of the fetal myocardial performance index (MPI) in assessing intrahepatic cholestasis of pregnancy (ICP).

METHODS

This was a cohort study including cross-sectional and longitudinal data from 31 women with ICP recruited from June 2012 to March 2014. Fetal left, right and delta MPI (LMPI, RMPI and DMPI), and routine measures of fetal growth and wellbeing, were obtained at each ultrasound examination. Results were evaluated with respect to gestational age (GA)-adjusted reference intervals, level of maternal serum bile acid (SBA) and fetal outcome. Lower SBA (≥ 7.5 and < 40 μmol/L) and high SBA (≥ 40 μmol/L) subgroups of cases were defined for the analysis.

RESULTS

A total of 51 ultrasound examinations were performed in 33 fetuses. The mean LMPI, and means of its isovolumetric relaxation time (IRT) and isovolumetric contraction time (ICT) components were significantly higher in all subgroups of cases of ICP relative to the normal reference mean. Considering only the first examination in each case of ICP, IRT was significantly more prolonged in the high SBA group (n = 10) in comparison to the lower SBA group (n = 23) (52.7 ± 8.0 ms vs 47.3 ± 4.8 ms, P = 0.02), and both IRT (r = 0.538, P = 0.001) and LMPI (r = 0.367, P = 0.036) were significantly correlated with SBA concentration. The proportion of high SBA cases with LMPI, RMPI or DMPI > 2 SD above the GA-adjusted reference mean was not significantly greater than for the lower SBA group. On analysis of all data from those cases with more than one examination, no significant correlation was found between SBA concentration and any of the MPI variables.

CONCLUSIONS

LMPI values increase above the population GA-adjusted mean in cases of ICP, particularly amongst women with higher SBA. A significant correlation between IRT and LMPI at initial examination and increasing SBA concentration was found. A future multicenter prospective study may clarify the prognostic utility of MPI in ICP.

Physiology of the fetal and transitional circulation

The fetal circulation is an entirely transient event, not replicated at any point in later life, and functionally distinct from the pediatric and adult circulations. Understanding of the physiology of the fetal circulation is vital for accurate interpretation of hemodynamic assessments in utero, but also for management of circulatory compromise in premature infants, who begin extrauterine life before the fetal circulation has finished its maturation. This review summarizes the key classical components of circulatory physiology, as well as some of the newer concepts of physiology that have been appreciated in recent years. The immature circulation has significantly altered function in all aspects of circulatory physiology. The mechanisms and significance of these differences are also discussed, as is the impact of these alterations on the circulatory transition of infants born prematurely.

The Fetal Modified Myocardial Performance Index: Is Automation the Future?

The fetal modified myocardial performance index (Mod-MPI) is a noninvasive, pulsed-wave Doppler-derived measure of global myocardial function. This review assesses the progress in technical refinements of its measurement and the potential for automation to be the crucial next step. The Mod-MPI is a ratio of isovolumetric to ejection time cardiac time intervals, and the potential for the left ventricular Mod-MPI as a tool to clinically assess fetal cardiac function is well-established. However, there are wide variations in published reference ranges, as (1) a standardised method of selecting cardiac time intervals used in Mod-MPI calculation has not been established; (2) cardiac time interval measurement currently requires manual, inherently subjective placement of callipers on Doppler ultrasound waveforms; and (3) ultrasound machine settings and ultrasound system type have been found to affect Mod-MPI measurement. Collectively these factors create potential for significant inter- and intraobserver measurement variability. Automated measurement of the Mod-MPI may be the next key development which propels the Mod-MPI into routine clinical use. A novel automated system of Mod-MPI measurement is briefly presented and its implications for the future of the Mod-MPI in fetal cardiology are discussed.

Is There a Measurable Difference between the Left and Right Modified Myocardial Performance Indices, and Does This Change to Reflect Unilateral Myocardial Dysfunction in Pathology?

Introduction: Fetal cardiac dysfunction may manifest itself unilaterally as right and left ventricles differing in design, function and load, measurable as differing in myocardial performance indices (MPIs). We wished to define this difference (‘delta-MPI' or DMPI), present its normal range and pilot its use in pathological pregnancy. Material and Methods: Prospective cross-sectional study of 324 normal singleton fetuses (16-38 weeks of gestation). Left and right modified MPI (LMPI and RMPI) were performed during a single examination using the ‘peak' valve click technique. Thirty-seven pathological singleton and monochorionic diamniotic twin pregnancies were compared as pilot data. Results: Modified MPIs (mean ± SD) were 0.45 ± 0.06 (LMPI) and 0.47 ± 0.09 (RMPI), being similar at 18 weeks' gestation with DMPI increasing slightly throughout pregnancy (0.02 ± 0.08). Both singleton intrauterine growth restriction (IUGR) and recipient twin-twin transfusion syndrome (TTTS) showed significantly elevated RMPI, LMPI and DMPI, most pronounced for DMPI (450 and 500% increase, respectively; p < 0.01). DMPI acquisition rates were 83.3% normal and 87.0% pathological. Discussion: We demonstrate for the first time differing intrafetal LMPI and RMPI in a large gestational cohort, with this difference increasing with gestational age. Pilot data confirm the potential for DMPI as a tool to assess unilateral myocardial function in singleton IUGR and recipient twins in TTTS, and further studies are under way to evaluate its clinical utility.

The (Pulsed-Wave) Doppler Fetal Myocardial Performance Index: Technical Challenges, Clinical Applications and Future Research

Functional cardiovascular assessment is becoming an increasingly important tool in the study of fetal pathology. The myocardial performance index (MPI) is a parameter measuring global myocardial function. Since its introduction, several studies have proposed methods to improve its reproducibility and have constructed normative reference ranges. Fetal heart evaluation using the MPI is technically challenging, requiring specific training and expertise, and a consensus has yet to be reached on the method of delineating the time periods used to calculate the index. Despite these limitations, it has been shown to be a useful and highly sensitive parameter of dysfunction in a number of fetal pathologies. Further research is warranted into the effect of pathology on MPI, parameters of unilateral cardiac strain that utilise MPI, and automation of the MPI to encourage incorporation of the MPI as a useful tool in clinical practice.

Minimally invasive therapy for fetal sacrococcygeal teratoma: case series and systematic review of the literature

OBJECTIVE

Large solid sacrococcygeal teratomas (SCT) can cause high-output cardiac failure and fetal or neonatal death. The aim of this study was to describe the outcomes of minimally invasive antenatal procedures for the treatment of fetal SCT.

METHODS

A case review was performed of five fetuses with a large SCT treated antenatally using minimally invasive techniques, and a systematic literature review on fetal therapy for solid SCTs was carried out.

RESULTS

Five women were referred between 17 + 5 and 26 + 4 weeks' gestation for a large fetal SCT with evidence of fetal cardiac failure. Vascular flow to the tumors was interrupted by fetoscopic laser ablation (n = 1), radiofrequency ablation (RFA; n = 2) or interstitial laser ablation  ±  vascular coiling (n = 2). There were two intrauterine fetal deaths. The other three cases resulted in preterm labor within 10 days of surgery. One neonate died. Two survived without procedure-related complications but had long-term morbidity related to prematurity. The systematic literature review revealed 16 SCTs treated minimally invasively for (early) hydrops. Including our cases, six of 20 hydropic fetuses survived after minimally invasive therapy (30%). Survival after RFA or interstitial laser ablation was 45% (5/11). Of 12 fetuses treated for SCT without obvious hydrops and for which perinatal survival data were available, eight (67%) survived. Mean gestational age at delivery after minimally invasive therapy was 29.7 ± 4.0 weeks. Survival after open fetal surgery in hydropic fetuses was 6/11 (55%), with a mean gestational age at delivery of 29.8 ± 2.9 weeks.

CONCLUSIONS

Fetal therapy can potentially improve perinatal outcomes for hydropic fetuses with a solid SCT, but is often complicated by intrauterine death and preterm birth.

Multifaceted roles of miR-1s in repressing the fetal gene program in the heart

miRNAs are an important class of regulators that play roles in cellular homeostasis and disease. Muscle-specific miRNAs, miR-1-1 and miR-1-2, have been found to play important roles in regulating cell proliferation and cardiac function. Redundancy between miR-1-1 and miR-1-2 has previously impeded a full understanding of their roles in vivo. To determine how miR-1s regulate cardiac function in vivo, we generated mice lacking miR-1-1 and miR-1-2 without affecting nearby genes. miR-1 double knockout (miR-1 dKO) mice were viable and not significantly different from wild-type controls at postnatal day 2.5. Thereafter, all miR-1 dKO mice developed dilated cardiomyopathy (DCM) and died before P17. Massively parallel sequencing showed that a large portion of upregulated genes after deletion of miR-1s is associated with the cardiac fetal gene program including cell proliferation, glycolysis, glycogenesis, and fetal sarcomere-associated genes. Consistent with gene profiling, glycogen content and glycolytic rates were significantly increased in miR-1 dKO mice. Estrogen-related Receptor β (Errβ) was identified as a direct target of miR-1, which can regulate glycolysis, glycogenesis, and the expression of sarcomeric proteins. Cardiac-specific overexpression of Errβ led to glycogen storage, cardiac dilation, and sudden cardiac death around 3-4 weeks of age. We conclude that miR-1 and its primary target Errβ act together to regulate the transition from prenatal to neonatal stages by repressing the cardiac fetal gene program. Loss of this regulation leads to a neonatal DCM.

Factors modulating effective chest compressions in the neonatal period

The need for chest compressions in the newborn is a rare occurrence. The methods employed for delivery of chest compressions have been poorly researched. Techniques that have been studied include compression:ventilation ratios, thumb versus finger method of delivering compressions, depth of compression, site on chest of compression, synchrony or asynchrony of breaths with compressions, and modalities to improve the compression technique and consistency. Although still in its early days, an evidence-based guideline for chest compressions is beginning to take shape.

Anesthesia for in utero repair of myelomeningocele

Recently published results suggest that prenatal repair of fetal myelomeningocele is a potentially preferable alternative when compared to postnatal repair. In this article, the pathology of myelomeningocele, unique physiologic considerations, perioperative anesthetic management, and ethical considerations of open fetal surgery for prenatal myelomeningocele repair are discussed. Open fetal surgeries have many unique anesthetic issues such as inducing profound uterine relaxation, vigilance for maternal or fetal blood loss, fetal monitoring, and possible fetal resuscitation. Postoperative management, including the requirement for postoperative tocolysis and maternal analgesia, are also reviewed. The success of intrauterine myelomeningocele repair relies on a well-coordinated multidisciplinary approach. Fetal surgery is an important topic for anesthesiologists to understand, as the number of fetal procedures is likely to increase as new fetal treatment centers are opened across the United States.

Tumor metrics and morphology predict poor prognosis in prenatally diagnosed sacrococcygeal teratoma: a 25-year experience at a single institution

PURPOSE

Some fetuses with sacrococcygeal teratoma (SCT) develop hydrops, but there is no consensus on an appropriate prognostic marker for poor prognosis. The purpose of this study is to establish predictors of poor prognosis in fetuses with SCT.

METHODS

A retrospective review of patients with prenatally diagnosed SCT from 1986 to 2011 was performed. Patients with outcome data and ultrasound exams before 32 weeks gestational age (GA) were included (n=37). Tumor volume-to-fetal weight ratio (TFR) and tumor morphology were assessed as sonographic predictors of poor prognosis.

RESULTS

Twelve patients (32%) had good prognosis, and twenty-five patients (68%) had poor prognosis. All patients with poor prognosis had a morphology score ≥ 3, which is a significant predictor of poor prognosis (p <0.0001). TFR was assessed, and a receiver operating characteristic (ROC) analysis identified a cutoff value of 0.12 before 24 weeks GA and 0.11 before 32 weeks GA as predictors for poor prognosis. TFR is a significant predictor of poor prognosis (p<0.0001).

CONCLUSIONS

Patients with cystic SCT all had good prognosis. TFR >0.12 was validated as a sonographic predictor of poor prognosis. TFR and tumor morphology can be used to counsel expectant families with prenatally diagnosed SCT regarding prognosis.

Anesthesia for fetal surgery

Fetal surgery pushes the limits of knowledge and therapy beyond conventional paradigms by treating the developing fetus as a patient. Providing anesthesia for fetal surgery is challenging for many reasons. It requires integration of both obstetric and pediatric anesthesia practice. Two patients must be anesthetized for the benefit of one, and there is little margin for error. Many disciplines are involved, and communication must be effective among all of them. Conducting anesthetic research with vulnerable populations, such as the pregnant woman carrying a fetus with a birth defect is difficult, and many questions remain to be answered. Work is needed to study possible neurotoxicity caused by exposure of the developing brain to anesthetic agents. The effects of stress on the developing fetus also must be further delineated. Anesthetic techniques vary by institution, and prospective studies to determine optimal anesthetic regimens are warranted.

Neonatal resuscitation: foetal physiology and pathophysiological aspects

Although approximately 10% of all newborn infants receive some form of assistance after birth, only 1% of neonates require more advanced measures of life support. Because such situations cannot always be anticipated, paediatricians and neonatologists are frequently unavailable and resuscitation is delegated to the anaesthesiologist. The International Liaison Committee on Resuscitation, the European Resuscitation Council and the American Heart Association have recently updated the guidelines on neonatal resuscitation. The revised guidelines propose a simplified resuscitation algorithm that highlights the central role of respiratory support and promotes an increasing heart rate as the best indicator for effective ventilation. The most striking change in the new guidelines is the recommendation to start resuscitation in term infants with room air rather than 100% oxygen. Continuous pulse oximetry is recommended to monitor both heart rate and an appropriate increase in preductal oxygen saturation. Supplemental oxygen should only be used if, despite effective ventilation, the heart rate does not increase above 100  beats  min(-1), or if oxygenation as indicated by pulse oximetry, remains unacceptably low. This review will focus on foetal physiology and pathophysiological aspects of neonatal adaptation and, thus, attempt to provide a solid basis for understanding the new resuscitation guidelines.