Cardiac output and central distribution of blood flow in the human fetus

Reference ranges for the left ventricle modified myocardial performance index, respective time periods, and atrioventricular peak velocities between 20 and 36 + 6 weeks of gestation

Objective: To establish reference ranges for the fetal left ventricle (LV) modified myocardial performance index (Mod-MPI), respective time periods, and right and left atrioventricular peak velocities between 20 and 36 + 6 weeks of gestation.Methods: This cross-sectional study evaluated 360 low-risk singleton pregnancies between 20 and 36 + 6 weeks of gestation. The LV Mod-MPI was calculated as (isovolumetric contraction time + isovolumetric relaxation time)/ejection time. Polynomial regression was used to obtain the best-fit using Mod-MPI and atrioventricular peak velocity measurements and gestational age (GA) with adjustments using the coefficient of determination (R²). The intra- and interobserver reliability was evaluated using the concordance correlation coefficient (CCC).Results: LV Mod-MPI (R² = 0.026, p = .002) and isovolumetric relaxation time (IRT) (R² = 0.036, p < .001) significantly increased with advancing GA. Isovolumetric contraction time (ICT) and ejection time (ET) did not significantly change with GA. RV and LV E wave, A wave, and E/A ratio significantly increased with GA (p < .001). The mean of each parameter ranged as follows: LV Mod-MPI (0.44-0.47 s), IRT (0.041-0.045 s), ICT (0.032-0.034 s), ET (0.167-0.167 s), RV E (30.2-46.91 cm/s), RV A (47.1-60.7 cm/s), RV E/A (0.65-0.78 cm/s), LV E (27.0-41.4 cm/s), LV A (43.2-53.8 cm/s), and LV E/A (0.63-0.78 cm/s). Only LV A wave measurements demonstrated an intraobserver CCC >0.80. The remaining intra- and interobserver reproducibility parameters demonstrated lower CCC.Conclusions: Reference values were replicated for the fetal LV Mod-MPI and LV and RV transvalvular peak velocities between 20 and 36 + 6 weeks of gestation.

Evaluation of Fetal Left Ventricular Size and Function Using Speckle-Tracking and the Simpson Rule

OBJECTIVES

This study was conducted to evaluate left ventricular (LV) size and function in healthy fetuses and to test a cohort of fetuses at risk for abnormal function using speckle-tracking software.

METHODS

Two hundred control fetuses were examined between 20 and 40 weeks' gestation. With the use of offline speckle-tracking software, the end-diastolic and end-systolic volumes were measured and the following computed: stroke volume (SV), SV per kilogram, cardiac output (CO), CO per kilogram, and ejection fraction. These were regressed against 7 independent variables related to the size, weight, and age of the fetuses. Five fetuses with risk factors for LV dysfunction were examined to sample the validity of the data from the control group.

RESULTS

The R² values for measurements of the end-diastolic volume, SV, and CO correlated with the 7 independent variables of fetal size and age (0.7-0.78), whereas the SV/kg, CO/kg, and ejection fraction had lower R² values (0.02-0.1). The measurements were normally distributed (Shapiro-Wilke > 0.5). The 5 fetuses at risk for abnormal LV function had measurements of LV size and function that were consistent with the expected pathologic condition.

CONCLUSIONS

Speckle tracking can provide a comprehensive evaluation of the size and function of the fetal LV.

Transitional fetal hemodynamics and gas exchange in premature postpartum adaptation: immediate vs. delayed cord clamping

Background

Recent studies suggest that delayed cord clamping (DCC) is advantageous for achieving hemodynamic stability and improving oxygenation compared to the immediate cord clamping (ICC) during fetal-to-neonatal transition yet there is no quantitative information on hemodynamics and respiration, particularly for pre-term babies and fetal disease states. Therefore, the objective of this study is to investigate the effects of ICC and DCC on hemodynamics and respiration of the newborn preterm infants in the presence of common vascular pathologies.

Methods

A computational lumped parameter model (LPM) of the placental and respiratory system of a fetus is developed to predict blood pressure, flow rates and oxygen saturation. Cardiovascular system at different gestational ages (GA) are modeled using scaling relations governing fetal growth with the LPM. Intrauterine growth restriction (GR), patent ductus arteriosus (PDA) and respiratory distress syndrome (RDS) were modeled for a newborn at 30 weeks GA. We also formulated a "severity index (SI)" which is a weighted measure of ICC vs. DCC based on the functional parameters derived from our model and existing neonatal disease scoring systems.

Results

Our results show that transitional hemodynamics is smoother in DCC compared to ICC for all GAs. Blood volume of the neonate increases by 10% for moderately preterm and term infants (32-40 wks) and by 15% for very and extremely preterm infants (22-30 wks) with DCC compared to ICC. DCC also improves the cardiac output and the arterial blood pressure by 17% in term (36-40 wks), by 18% in moderately preterm (32-36 wks), by 21% in very preterm (28-32 wks) and by 24% in extremely preterm (20-28 wks) births compared to the ICC. A decline in oxygen saturation is observed in ICC received infants by 20% compared to the DCC received ones. At 30 weeks GA, SI were calculated for healthy newborns (1.18), and newborns with GR (1.38), PDA (1.22) and RDS (1.2) templates.

Conclusion

Our results suggest that DCC provides superior hemodynamics and respiration at birth compared to ICC. This information will help preventing the complications associated with poor oxygenation arising in premature births and pre-screening the more critical babies in terms of their cardiovascular severity.

Clinical Monitoring of Sacrococcygeal Teratoma

BACKGROUND

Sacrococcygeal teratomas (SCT) are often highly vascularized and may result in high-output cardiac failure, polyhydramnios, fetal hydrops, and demise. Delivery is guided by the SCT to fetus volume ratio (SCTratio), SCT growth rate, and cardiac output indexed for weight (CCOi).

METHODS

We compared measurements and outcome in 12 consecutive fetuses referred with SCT. Adverse outcomes were: fetal surgery, delivery < 32 gestational weeks or neonatal demise. Only SCTratio and CCOi were used to manage the cases. SCT vascularization index (VI%) was derived from the 3D virtual organ computer-aided analysis (VOCAL) software. The SCTModel (modified from acardiac twins) calculated a hypothetical SCT draining vein size and derived a risk line, using diameters of the superior and inferior vena cava, the azygous and umbilical veins. VI% and a model of systemic and umbilical venous volumes (SCTModel) were tested as indicators for outcome in SCT.

RESULTS

Fetuses were monitored from 20.1 to 36.4 gestational weeks and 5/12 had adverse outcomes: 1 had successful open fetal surgery at 23.8 weeks and delivered at term, 4 delivered at < 32 weeks with 3/4 having neonatal demise between 25 and 29 weeks. VI% was significantly higher in cases with adverse outcomes (mean 10.3 [8.9-11.6] vs. 4.4 [3.4-5.3], p < 0.0001). The additional fraction of the fetal cardiac output required to perfuse the SCT-draining vein (XSCO%) (p = 0.46), SCTratio (p = 0.08), and CCOi (p = 0.64) were not significant. All cases with adverse outcome had VI% > 8%. The SCTModel risk line predicted nonadverse outcomes well but lacked data in 2/5 cases with adverse outcomes.

CONCLUSIONS

VI% is a significant indicator of SCT cases with adverse outcomes and combined with SCTratio may guide timing of delivery better than current measures.

Correlation between fetoplacental Doppler indices and measurements of cardiac function in term fetuses

OBJECTIVE

Redistribution of cardiac output (CO) is responsible for the brain-sparing effect seen during periods of fetal stress. Our aim was to investigate prospectively the correlation between fetoplacental Doppler indices and measurements of cardiac function in uncomplicated term singleton pregnancy.

METHODS

This was a prospective observational study of normotensive women with appropriately grown, non-anomalous singleton pregnancy. Participants underwent fortnightly ultrasound examinations from 36 weeks' gestation until delivery, and intrapartum and neonatal outcomes were recorded. The correlation between fetoplacental Doppler indices and various measurements of cardiac function was evaluated.

RESULTS

The study cohort comprised 273 singleton pregnancies. The cerebroplacental ratio (CPR) was correlated positively with left ventricular CO (LVCO) (P < 0.001, rho = 0.29), left-to-right ventricular CO ratio (LVCO/RVCO; P < 0.001, rho = 0.41), global left ventricular strain (P < 0.01, rho = 0.17) and global right ventricular strain (P < 0.001, rho = 0.22). The CPR was correlated inversely with the left ventricular myocardial performance index (P < 0.01, rho = -0.18) and the RVCO (P < 0.001, rho = -0.28). The LVCO and global left ventricular strain were correlated positively with umbilical venous flow (P = 0.04, rho = 0.18 and P < 0.001, rho = 0.25, respectively). There was minimal or no correlation between either the mean uterine artery pulsatility index (PI) or umbilical artery PI with any cardiac indices.

CONCLUSION

The fetal CPR, middle cerebral artery PI and umbilical venous flow are correlated positively with LVCO, LVCO/RVCO and global left ventricular strain in low-risk term pregnancies. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

Comprehensive Evaluation of Right Heart Performance and Pulmonary Hemodynamics in Neonatal Pulmonary Hypertension : Evaluation of cardiopulmonary performance in neonatal pulmonary hypertension

PURPOSE OF REVIEW

Pulmonary hypertension is characterized by an elevation of pulmonary artery pressures and prolonged exposure of the right ventricle to high afterload that collectively contribute to morbidity and mortality in both the term and preterm infants. This review summarizes the pathogenesis, etiologies, and hemodynamic profiles of the conditions that result in pulmonary hypertension in neonates. We explore the application of echocardiographic techniques for the assessment of right ventricular performance and pulmonary hemodynamics that enhance and guide the diagnosis and management strategies in neonates.

RECENT FINDINGS

Clinical assessments based on the determinants of mean pulmonary artery pressures (pulmonary vascular resistance, pulmonary blood flow, and pulmonary capillary wedge pressure) provide a physiologic approach in determining the acute and chronic etiologies of pulmonary hypertension in neonates. In addition, advances in neonatal echocardiography now afford the capability to obtain quantitative information that often precedes the qualitative information acquired by conventional methods and also provide sensitive markers of right ventricle performance for prognostic information based on the determinants of mean pulmonary artery pressures. Neonatal pulmonary hypertension represents a physiologic spectrum that accounts for the variance in clinical presentation and response to therapies. Physiology-based approaches to etiological identification, coupled with the emerging echocardiographic methods for the assessment of pulmonary hypertension in neonates will likely help to identify cardiovascular compromise earlier, guide therapeutic intervention, monitor therapeutic effectiveness, and improve overall outcome.

How to perform a functional assessment of the fetal heart: a pictorial review

The purpose of this pictorial review was to describe various echocardiographic techniques that can be used for the functional assessment of the fetal heart. The systolic and diastolic assessments of the fetal heart are presented separately, with an emphasis on 2-dimensional Doppler methods and an overview of new technologies. The aim of this summary was to review the tools that can be used by the echocardiographer, and on that basis, to systematize the process of performing a functional assessment.

Z-score reference ranges for pulsed-wave Doppler indices of the cardiac outflow tracts in normal fetuses

To determine Z-score equations and reference ranges for Doppler flow velocity indices of cardiac outflow tracts in normal fetuses. A prospective cross-sectional echocardiographic study was performed in 506 normal singleton fetuses from 18 to 40 weeks. Twelve pulsed-wave Doppler (PWD) measurements were derived from fetal echocardiography. The regression analysis of the mean and the standard deviation (SD) for each parameter were performed against estimated fetal weight (EFW) and gestational age (GA), in order to construct Z-score models. The correlation between these variables and fetal heart rate were also investigated. Strong positive correlations were found between the twelve PWD indices and the independent variables. A linear-quadratic regression model was the best description of the mean and SD of most parameters, with the exception of the velocity time interval (VTI) of ascending aorta against EFW, which was best fitted by a fractional polynomial. Z-score equations and reference values for PWD indices of fetal cardiac outflow tracts were proposed against GA and EFW, which may be useful for quantitative assessment of potential hemodynamic alternations, particularly in cases of intrauterine growth retardation and structural cardiac defects.

Functional cardiac measurements performed by two-dimensional Doppler echocardiography in normal fetuses: Determination of Z-scores and future prospects

Two-dimensional (2D) echocardiogram with the aid of color Doppler and pulsed Doppler allows one to record blood flow waveforms in several structures of the heart. The determination of normal values of these flows in the fetus can help understand cardiac hemodynamics. Given this importance, numerous surveys have been conducted with various existing echocardiographic techniques in order to improve the functional evaluation and consequently, planning of delivery. The aim of this review was to discuss the findings of the reference values of blood flows obtained by 2D echocardiography with Doppler, the current trend of the determination of Z-scores in the functional measurements, and their future prospects.

Variations in ductus arteriosus Doppler parameters in different sonographic views during the second half of gestation

The aim of the present study was to compare the Doppler parameters of the fetal ductus arteriosus (DA) measured in the traditional longitudinal ductal arch (LDA) view and the newly introduced three vessels and trachea (3VT) plane of the fetal upper mediastinum. The peak systolic velocity (PSV), end-diastolic velocity (EDV), time-averaged maximum velocity (TAMXV) and velocity-time integral (VTI) measurements were taken for 52 fetuses with normal growth (including 29 females). The pulsatility index (PI) and resistance index (RI) were calculated. All parameters for each fetus were measured three times by the same sonographer in the LDA and the 3VT view, and the averages were taken to obtain the final value. Differences in the above values obtained from the LDA and 3VT views were analyzed and the correlation between the differences of all indices and the gestational age (GA) was evaluated using Pearson's linear coefficient of correlation. All of the values were characterized as normally distributed continuous variables by homogeneity of variance analysis. Slight increases in the PSV, EDV, TAMXV and VTI determined in the LDA view were identified compared with those in the 3VT view (P<0.05). Furthermore, these increases were identified to be independent of the GA (P>0.05). However, no significant differences in the impedance indices PI and RI were observed between the two sonographic planes (P>0.05). In conclusion, the LDA view provides a better chance than the 3VT view to obtain higher values of velocity parameters (PSV, EDV, TMAXV and VTI) within the fetal DA, and the differences are independent of the GA. However, no significant variations in the impedance indices PI and RI were observed between these two sonographic planes.

Evolution and Development of the Atrial Septum

The complete division of the atrial cavity by a septum, resulting in a left and right atrium, is found in many amphibians and all amniotes (reptiles, birds, and mammals). Surprisingly, it is only in eutherian, or placental, mammals that full atrial septation necessitates addition from a second septum. The high incidence of incomplete closure of the atrial septum in human, so-called probe patency, suggests this manner of closure is inefficient. We review the evolution and development of the atrial septum to understand the peculiar means of forming the atrial septum in eutherian mammals. The most primitive atrial septum is found in lungfishes and comprises a myocardial component with a mesenchymal cap on its leading edge, reminiscent to the primary atrial septum of embryonic mammals before closure of the primary foramen. In reptiles, birds, and mammals, the primary foramen is closed by the mesenchymal tissues of the atrioventricular cushions, the dorsal mesenchymal protrusion, and the mesenchymal cap. These tissues are also found in lungfishes. The closure of the primary foramen is preceded by the development of secondary perforations in the septal myocardium. In all amniotes, with the exception of eutherian mammals, the secondary perforations do not coalesce to a secondary foramen. Instead, the secondary perforations persist and are sealed by myocardial and endocardial growth after birth or hatching. We suggest that the error-prone secondary foramen allows large volumes of oxygen-rich blood to reach the cardiac left side, needed to sustain the growth of the extraordinary large offspring that characterizes eutherian mammals. Anat Rec, 302:32-48, 2019. © 2018 The Authors. The Anatomical Record published by Wiley Periodicals, Inc. on behalf of American Association of Anatomists.

Effect of fetal hemodynamics on growth in fetuses with single ventricle or transposition of the great arteries

OBJECTIVES

As birth weight is a critical predictor of outcome in neonates with congenital heart defect (CHD), the common problem of poor fetal growth in this population is clinically important. However, it is not well understood and the impact of fetal hemodynamics on fetal growth and birth weight in those with CHD has not been assessed. In this study, we sought to evaluate the association between combined cardiac output (CCO) and fetal middle cerebral artery (MCA) and umbilical artery (UA) pulsatility indices (PIs) and fetal growth in different subgroups of CHD, and to study the effects of fetal hemodynamics on late gestational weight gain. We hypothesized that fetuses with CHD will have lower CCO and be smaller at birth.

METHODS

This was a retrospective review of fetal echocardiograms from 67 fetuses diagnosed with hypoplastic left heart syndrome (HLHS, n = 30), non-HLHS single ventricle (SV) (n = 20) or dextrotransposition of the great arteries (d-TGA, n = 17), compared with normal controls (n = 42). CCO was calculated using valvar area, velocity-time integral and heart rate and indexed to estimated fetal weight. MCA- and UA-PI were calculated using systolic, diastolic and mean velocities. Fetal biometry was recorded. Regression models were used to study trends in CCO, MCA- and UA-PI and fetal biometry over gestational age. To evaluate fetal weight gain in late gestation, Z-scores of estimated fetal weight at 30 weeks and birth weight were compared. Regression analysis was used to determine the associations of CCO, indexed CCO and MCA- and UA-PI at 30 weeks with birth weight, length and head circumference Z-scores, in addition to weight gain late in gestation. The gestational age of 30 weeks was chosen based on previous studies that found evidence of poor weight gain in fetuses with CHD in late gestation, starting at around that time.

RESULTS

CCO increased with gestation in all four groups but the rate was slower in fetuses with HLHS and in those with SV. MCA-PI was lower in fetuses with HLHS compared with in those with non-HLHS-SV throughout gestation, suggesting different cerebral blood distribution. At the end of gestation, rate of fetal weight gain slowed in those with HLHS and in those with SV (similar to CCO curves), and head circumference growth rate slowed in all groups but controls. CCO, indexed CCO and MCA- and UA-PI did not correlate with any of the birth measurements or with weight gain late in gestation in fetuses with CHD.

CONCLUSIONS

We found no associations of CCO or MCA- and UA-PI with late gestational weight gain or biometry at birth in fetuses with CHD. This does not support fetal hemodynamics as the primary driver of suboptimal fetal growth in fetuses with SV. Future research could further explain genetic and placental abnormalities that may affect fetal growth in those with CHD. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Cardiopulmonary Adaptation During First Day of Life in Human Neonates

OBJECTIVE

To characterize the natural history of cardiopulmonary physiology in the first 24 hours after birth.

STUDY DESIGN

A prospective observational study of healthy newborns was conducted at a large tertiary perinatal center. Echocardiography was performed at <0.5, 2-3, 7-10, and 22-24 hours of age. Specifically, assessment of pulmonary vascular resistance (PVR) (pulmonary artery acceleration time [PAAT], right ventricular ejection time, right ventricular ejection time:PAAT [PVR index], and PAAT indexed to heart rate [PAATi]), ventricular outputs (right and left), and ventricular function (tricuspid annular planar excursion, right ventricular [RV] fractional area change [FAC], RV/left ventricular [LV] global peak longitudinal strain, and LV ejection fraction) were performed. One-way repeated-measures ANOVA analysis was performed for time-dependent variables.

RESULTS

In total, 15 neonates (9 males), born at 40 ± 0.8 weeks and 3.5 ± 0.5 kg, respectively, were studied. We observed increased PAATi (P < .05) by 2-3 hours, followed by a subsequent decline in all indices of PVR (PVR index, PAATi, midsystolic notching, and right-to-left ductal flow [P < .0001]). Although right and left ventricular stroke volume increased over the study interval (P < .001), LV output remained stable. All indices of RV function (tricuspid annular planar excursion, RV fractional area change 4-chamber, and RV global peak longitudinal strain-3 chamber [P < .001]) increased during the study interval.

CONCLUSION

The immediate transition after birth is characterized by lower PVR, reversal of the transductal shunt, and increased biventricular stroke volume. The differential adaptive response of the RV and LV is novel and may relate to loading conditions and patent ductus arteriosus closure.

Circulatory changes during gestational development of the sheep and human fetus

BACKGROUND

Circulatory changes during gestational development of the human fetus have been considered to be similar to those noted in studies of the lamb fetus.

METHODS

Blood flow measurements derived by Doppler ultrasound and magnetic resonance imaging techniques in human fetuses at various stages of gestation have been compared with those in the lamb.

RESULTS

Combined ventricular output relative to fetal body weight does not change significantly with growth in the lamb or human. However, the proportion of cardiac output to the brain increases markedly in the human, but only slightly in the lamb fetus in the latter half of gestation. Cardiac output distribution to other organs also changes little in the lamb, but in the human, there is a marked decrease in the proportion distributed to the placenta and an increase in pulmonary flow.

CONCLUSION

The developmental changes in the distribution of combined ventricular output in the human fetus may modify the responses to circulatory disturbances, such as congenital cardiovascular malformations, dependent on gestation.

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.

Ductus arteriosus and fetal echocardiography: Implications for practice

The ductus arteriosus (DA) is a crucial part of the fetal circulation, both in the normal fetus and in critical congenital heart disease (CHD). It allows shunting between the pulmonary and systemic circulations. In physiological prenatal conditions, the DA lets the majority of right ventricular output bypass the fluid-filled, high-resistance lungs. The DA can cause hemodynamic compromise in the fetus and neonate when constricted or absent (in isolation or in patients with CHD) and may lead to pre- or postnatal sequelae within other systems when forming part of a vascular ring. In CHD, the DA can be interrogated by fetal echocardiography to infer information regarding severity of pulmonary outflow tract obstruction, adequacy of the sub-pulmonary ventricle to supply pulmonary blood flow, and to predict the likelihood of atrial septum restriction in transposition of the great arteries. A good understanding of the DA is crucial for fetal cardiologists.

Hemodynamic adaptation to suboptimal fetal growth in patients with single ventricle physiology

BACKGROUND

In fetuses with structurally normal heart and suboptimal fetal growth (SFG), umbilical artery vascular resistance increases as measured by umbilical artery pulsatility index (UA-PI). The objective of this study is to compare hemodynamic responses to SFG in fetuses with single ventricle (SV) and controls with structurally normal heart.

METHODS

Fetal echocardiograms around 30 weeks of gestation were reviewed. UA-PI and middle cerebral artery pulsatility index (MCA-PI) were calculated. SFG was defined as a birth weight below 25th percentile for gestational age.

RESULTS

Studies from 92 fetuses were reviewed-SV (n = 50) and controls (n = 42). The prevalence of SFG was higher in SV compared to controls (46% vs 21%, P = .02). In patients with normal heart and SFG, UAPI was significantly higher than normal controls (P = .003) suggesting increased placental vascular resistance. In SV with SFG there was no difference in UAPI compared to SV without SFG. There was no difference in MCA-PI between the groups.

CONCLUSIONS

The hemodynamic response to SFG in SV varies from fetuses with structurally normal heart. The mechanism of SFG and the placental pathology may be distinct in SV.

Oxygen Therapy in the Delivery Room: What Is the Right Dose?

Oxygen is the most commonly used medicine used during neonatal resuscitation in the delivery room. Oxygen therapy in delivery room should be used judiciously to avoid oxygen toxicity while delivering sufficient oxygen to prevent hypoxia. Measurement of appropriate oxygenation relies on pulse oximetry, but adequate ventilation and perfusion are equally important for oxygen delivery. In this article, we review oxygenation while transitioning from fetal to neonatal life, the importance of appropriate oxygen therapy, its measurement in the delivery room, and current recommendations for oxygen therapy and its limitations.

Prelabour myocardial deformation and cardiac output in fetuses that develop intrapartum compromise at term: a prospective observational study

Objective: Redistribution of cardiac output is responsible for the "brain sparing" effect seen during periods of acute or chronic fetal stress. We investigated the relationship between prelabour cardiac function in fetuses that subsequently developed intrapartum fetal compromise (IFC). Methods: A blinded, prospective, observational, cohort study, at Mater Mother's Hospital, Brisbane, Australia. A cohort of 284 women with uncomplicated singleton pregnancies underwent ultrasound every 2 weeks from 36 weeks until delivery. Fetal cardiac output was assessed by conventional Doppler ultrasound and myocardial deformation was measured using velocity vector imaging. Results: Two hundred and seventy three women were included in the final analysis, of which 19% had an emergency operative delivery for intrapartum fetal compromise (IFC). Global left ventricular strain (-12.1%, interquartile ranges (IQR) - 10.3 to -14% versus 13%, IQR -11.3 to -14.2%, p = .01) and strain rate (-1.00, IQR 0.85-1.16 s^-1 versus -1.11, IQR -1.00 to -1.21 s^-1, p < .001) were lower in fetuses that required any emergency operative delivery for IFC compared to those that did not. Global longitudinal right ventricular strain rate was lower in fetuses that developed IFC (-1.04 ± 0.22 s^-1 versus 1.13 ± 0.22 s^-1, p < .001), whereas global right ventricular strain did not show any significance differences between the two groups. Additionally, left ventricular cardiac output was lower in fetuses that developed IFC or had a composite neonatal morbidity (560 ± 44 mL/min versus 617 ± 72 mL/min, p < .001) or (581 ± 44 mL/min versus 612 ± 72 mL/min, p < .01), respectively. Conclusion: Lower global left ventricular strain and strain rate and cardiac output are associated with IFC and poorer condition of the newborn. Assessment of fetal cardiac function may be useful for risk stratification for intrapartum fetal compromise in apparently "low risk" term pregnancies.

Functional morphometry for the estimation of the alveolar surface area in prematurely-born infants

Conventionally, the alveolar surface area (S_A) has been measured by using post-mortem morphometry. Such studies have highlighted that S_A in prematurely-born infants is markedly smaller when compared to term-born infants as a result of postnatal impairment or arrest of alveolar development. We herein explore how, non-invasive measurements of the ventilation/perfusion ratio (V_A/Q) can be used to estimate S_A in prematurely-born surviving, convalescent infants. We also compare S_A in prematurely-born infants measured at term-corrected age, to term-born infants using previously published datasets of V_A/Q. Fick's first law of diffusion is employed for the conversion of V_A/Q measurements to S_A values after correcting for differences in pulmonary perfusion, thickness of the respiratory membrane and alveolar-arterial gradient. We report that S_A is fivefold smaller in prematurely-born compared to term-born infants. We conclude that non-invasive measurements of V_A/Q can be used for the functional estimation of S_A which could, in turn, be used as a future outcome measure in respiratory studies of prematurely-born infants.

Restoring Fetal Circulation as a Means of Bridging Treatment Prior to Surgical Repair of Anomalous Origin of the Right Pulmonary Artery from the Ascending Aorta with Persistent Pulmonary Hypertension of the Newborn

Anomalous origin of one pulmonary artery from the ascending aorta is a rare congenital anomaly. Even more rarely reported is its presence in conjunction with persistent pulmonary hypertension of the newborn (PPHN). We present a case of a full-term infant, initially thought to have PPHN and later found to have anomalous origin of the right pulmonary artery from the ascending aorta. We discuss our management concept which included use of PgE1 infusion to restore fetal circulation prior to surgical treatment in this unique clinical scenario.

Cardiac pathophysiology in twin-twin transfusion syndrome: new insights into its evolution

OBJECTIVES

In twin-twin transfusion syndrome (TTTS), unbalanced transfer of vasoactive mediators and fluid from the donor to the recipient cotwin alters their cardiovascular function. The aims of this study were to describe the impact of TTTS on fetal cardiac function in a large cohort of monochorionic-diamniotic (MCDA) pregnancies, and determine the early hemodynamic response to selective fetoscopic laser photocoagulation (SFLP).

METHODS

Echocardiography was performed in 145 MCDA pregnancies, including 26 uncomplicated MCDA, 61 TTTS Stages I+II and 58 TTTS Stages III+IV pregnancies, prior to SFLP for TTTS. Echocardiographic data after SFLP were available in a subset of 41/119 (34%) TTTS cases at a mean of 1.7 ± 1.9 days. Mitral (MAPSE) and tricuspid (TAPSE) annular systolic excursion, myocardial performance index (MPI), tissue Doppler velocities (E', A', S') and filling pressures (E/E') were measured and transformed into Z-scores. Ventricular pressure was estimated from peak atrioventricular regurgitation velocity.

RESULTS

Left ventricular hemodynamics of the recipient twin were affected in early TTTS. In all stages of TTTS, left MPI and E/E' of the recipient twin were elevated in comparison to those of the donor (all P < 0.05), with reduced recipient left S' in TTTS Stages III+IV (P < 0.001). Ventricular pressure was elevated for gestational age (median, 42 mmHg (range, 20-65 mmHg)) in 11 of 14 recipients in which this parameter was measured. Between-group difference in right ventricular E/E' was significant only in TTTS Stages III+IV recipients compared with TTTS Stages I+II (P = 0.007) and uncomplicated MCDA (P = 0.041). Recipient left and right MPI decreased while S', MAPSE and TAPSE increased after SFLP; in donors, left E/E' and cardiac output increased.

CONCLUSIONS

Cardiac function of the recipient twin in TTTS is abnormal, even in the early stages of the disease. Left ventricular filling pressures are elevated and systolic function is decreased before abnormalities in the right heart become apparent. SFLP produces rapid hemodynamic improvement. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Physiological adaptation of the growth-restricted fetus

The growth-restricted fetus in utero is exposed to a hostile environment and suffers undernutrition and hypoxia. To cope with the stress, the fetus changes its physiological functions. These adaptive changes aid intrauterine survival; however, they can lead to permanent functional and structural changes that can contribute to the development of serious chronic diseases later in life. Epigenetic mechanisms are an important part of the pathophysiological processes behind this "developmental origin of adult diseases." The dominant cardiovascular adaptive change is the redistribution of blood flow in hypoxic fetuses, with preferential supply of blood to the fetal brain, myocardium, and adrenal glands. The proportion of blood from the umbilical vein to the ductus venosus and foramen ovale increases, which increases the cardiac output of the left heart ventricle. The increased perfusion of fetal brain can be followed with Doppler ultrasound as increased diastolic velocities and decreased pulsatility index in the middle cerebral artery.

Depressed left and right ventricular cardiac output in fetuses of diabetic mothers

INTRODUCTION

We compared right and left ventricular cardiac output (RVCO and LVCO) in fetuses of diabetic mothers (FDM) to a large normal cohort.

METHODS

We prospectively enrolled 264 normal fetuses and 30 FDM. Fetal CO parameters: semilunar valve velocity time integrals (AVVTI, PVVTI), ventricular outflow diameters (LVOTD, RVOTD), stroke volumes (AVSV, PVSV) were measured, and LVCO and RVCO calculated.  These were normalized using nonlinear regression to estimated fetal weight (EFW) to provide means and standard deviations. Among FDMs, mean Z-scores and 95% confidence limits (CL) were calculated, and compared to zero.

RESULTS

LVCO, RVCO, and parameters they were calculated from, increased predictably and non-linearly with increasing EFW.  In FDM, LVCO was depressed (mean Z -1.679, 95% CL -2.404, -0.955, p<0.001), and AVVTI, LVOTD, AVSV significantly lower than normal.  Similarly, RVCO (mean Z = -1.119, CL -1.839, -0.400, p=0.003), RVOTD (mean -2.085, CL -3.077, -1.093, p<0.001), and PVSV (mean -1.184, CL -1.921, -0.446, p=0.003) were lower than normal, however, PVVTI was not different (mean Z 0.078, CL -0.552, +0.707, p=0.803).

CONCLUSION

Normal biventricular stroke volumes and outputs follow a nonlinear regression with EFW. FDM have significantly lower right and left heart stroke volumes and outputs for weight than do normal fetuses.

Fetal cardiac remodeling in twin pregnancy conceived by assisted reproductive technology

OBJECTIVE

Recent data suggest that singleton fetuses conceived by assisted reproductive technology (ART) present cardiovascular remodeling that may persist postnatally. Twin pregnancies are more frequent in the ART population and are associated with increased adverse perinatal outcomes, such as hypertensive disorders, gestational diabetes and preterm birth. However, it is unknown whether cardiac remodeling is also present in twin pregnancies conceived by ART. Our aim was to assess the presence of fetal cardiac remodeling and dysfunction in twin pregnancies conceived by ART as compared with those conceived spontaneously (SC).

METHODS

This was a prospective cohort study including 50 dichorionic twin fetuses conceived by ART and 50 SC twin fetuses. The study protocol included collection of baseline/perinatal data and a fetal ultrasound examination at 28-30 weeks' gestation, including assessment of estimated fetal weight, fetoplacental Doppler and fetal echocardiography. Measurements of atrial area, atrial/heart ratio, ventricular sphericity index, free wall thickness, mitral and tricuspid annular plane systolic excursions, and systolic and early diastolic peak velocities were assessed. Multilevel analyses were used to compare perinatal and ultrasonographic parameters. Comparisons of echocardiographic variables were adjusted for parental age, paternal body mass index and incidence of pre-eclampsia.

RESULTS

Compared with SC twins, ART twin fetuses showed significant cardiac changes, predominantly affecting the right heart, such as dilated atria (right atrial/heart area: 15.7 ± 3.1 vs 18.4 ± 3.2, P < 0.001), more globular ventricles (right ventricular sphericity index: 1.57 ± 0.25 vs 1.41 ± 0.23, P = 0.001) and thicker myocardial walls (septal wall thickness: 2.57 ± 0.45 mm vs 2.84 ± 0.41 mm, P = 0.034) together with reduced longitudinal motion (tricuspid annular plane systolic excursion: 6.36 ± 0.89 mm vs 5.18 ± 0.93 mm, P < 0.001).

CONCLUSIONS

ART twin fetuses present signs of cardiac remodeling and dysfunction. These changes are similar to those observed in ART singletons and reinforce the concept of fetal cardiac programing in ART. These results open opportunities for early detection and intervention in infants conceived by ART. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

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.

Assessment of Fetal Myocardial Performance Index in Women with Placenta Previa

Background

This study investigated whether fetuses of placenta previa pregnancies have cardiac dysfunction by use of a modified myocardial performance index (Mod-MPI).

Material/Methods

A prospective cross-sectional study was conducted including 178 fetuses at 28–40 weeks of gestation. Eighty-nine fetuses of mothers with placenta previa and without pregnancy complications were recruited (placenta previa group) and matched with 89 fetuses of mothers with normal pregnancies (control group). Fetal cardiac function parameters and perinatal outcomes as well as the Mod-MPI were compared between the 2 groups.

Results

The median Mod-MPI was significantly increased in fetuses of mothers with placenta previa compared with controls (0.47±0.05 vs. 0.45±0.05; P<0.01). Among fetuses of mothers with or without placenta previa, the Mod-MPI was significantly higher in the incomplete placenta previa group compared with the complete placenta previa group and control group (P<0.01). An increased Mod-MPI in placenta previa pregnancies was independently associated with fetal cord pH <7.2 (odds ratio, 4.8; 95% confidence interval, 0.98–23.54; P=0.003).

Conclusions

There is impairment of fetal cardiac function in pregnancies with placenta previa. An increased MPI was independently associated with adverse perinatal outcomes to some extent in the placenta previa pregnancies.

Cardiac output and blood flow redistribution in fetuses with D-loop transposition of the great arteries and intact ventricular septum: insights into pathophysiology

OBJECTIVES

Although the postnatal physiology of D-loop transposition of the great arteries with intact ventricular septum (D-TGA/IVS) is well established, little is known about fetal D-TGA/IVS. In the normal fetus, the pulmonary valve (PV) is larger than the aortic valve (AoV), there is exclusive right-to-left flow at the foramen ovale (FO) and ductus arteriosus (DA), and the left ventricle (LV) ejects 40% of combined ventricular output (CVO) through the aorta, primarily to the brain. In D-TGA/IVS, the LV ejects oxygen-rich blood to the pulmonary artery, theoretically leading to pulmonary vasodilation, increased branch pulmonary artery flow and reduced DA flow. In this study, we tested the hypothesis that D-TGA/IVS anatomy results in altered cardiac valve sizes, ventricular contribution to CVO, and FO and DA flow direction.

METHODS

Seventy-four fetuses with D-TGA/IVS that underwent fetal echocardiography at our institution between 2004 and 2015 were included in the study. AoV, PV, mitral valve and tricuspid valve sizes were measured and Z-scores indexed to gestational age were generated. Ventricular output was calculated using Doppler-derived velocity-time integral, and direction of flow at the FO and DA shunts was recorded in each fetus using both color Doppler and flap direction. Measurements in the D-TGA/IVS fetuses were compared with data of 222 controls, matched for gestational-age range, from our institutional normal fetal database.

RESULTS

The LV component of CVO was higher in D-TGA/IVS fetuses than in controls (50.7% vs 40.2%; P < 0.0001), with no difference in the total CVO. Flow was bidirectional at the FO in 56 (75.7%) and at the DA in 24 (32.4%) D-TGA/IVS fetuses. Only 21.6% fetuses had normal right-to-left flow at both shunts. Bidirectional shunting was more common in third-trimester fetuses than in second-trimester ones (P < 0.03). AoV and PV diameters were nearly identical in D-TGA/IVS in contrast to control fetuses, hence AoV Z-score was higher than PV Z-score (1.13 vs -0.65, P < 0.0001) in D-TGA/IVS.

CONCLUSIONS

In fetuses with D-TGA/IVS there is loss of the normal right-sided dominance, as each ventricle provides half of the CVO, with a relatively large AoV diameter and a small PV diameter, and high incidence of bidirectional FO and DA flow. This may support the theory that high pulmonary artery oxygen content reduces pulmonary vascular resistance, thereby increasing branch pulmonary artery flow and venous return, which results in increased LV preload and output. Pulmonary sensitivity to oxygen is thought to increase later in gestation, which may explain the higher incidence of bidirectional shunting. Consequences of these flow alterations include increased aortic and, most likely, brain flow, perhaps in an attempt to compensate for the substrate deficiency observed in D-TGA/IVS. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Recipient umbilical artery elongation (redundancy) in twin-twin transfusion syndrome

BACKGROUND

Chronic hypertension in adults causes arterial lengthening in major arteries, but the effects of early fetal hypertension on the twin-twin transfusion syndrome recipient's vascular architecture remains unknown.

OBJECTIVE

We hypothesize that arterial cord redundancy is related to recipient hypertension and subsequent heart failure. Our objectives were to: (1) establish a 3-dimensional color Doppler ultrasound method of measuring umbilical arterial length relative to its corresponding venous segment in the umbilical cord using artery vein angle; (2) compare recipient artery vein angle to gestational age-matched controls; and (3) test the association of artery vein angle with recipient heart failure.

STUDY DESIGN

We compared 3 groups prospectively: twin-twin transfusion syndrome pregnancies undergoing fetoscopic laser surgery (preoperatively) and 2 groups of gestational age-matched controls: uncomplicated monochorionic-diamniotic twin pregnancies and healthy singletons. Using a 3-dimensional color-Doppler volume image of 5 cm of cord near the placental insertion, we traced the umbilical artery and vein producing umbilical artery:vein length, (artery vein index) and measured the artery vein angle between umbilical artery and vein. Correlation of artery vein angle to twin-twin transfusion syndrome stage, maximum vertical pocket, umbilical arterial indices, ductus venosus Doppler, and brain natriuretic peptide were performed. We used pulsed-wave and tissue Doppler to measure tissue Doppler velocities and indexed cardiac output and correlated these with artery vein angle. Comparative statistics, including multivariable linear regression, examined the relationship between umbilical arterial Doppler indices and artery vein angle.

RESULTS

Artery vein angle and artery vein index correlated significantly (R², 0.86; P < .0001), hence, artery vein angle was used for analysis. Mean artery vein angle was 33.1 ± 31.5 degrees in recipients (n = 44), 9.5 ± 6 degrees in monochorionic-diamniotic (n = 11; 22 fetuses), and 8.9 ± 8.3 degrees in singleton controls (n = 16) (P < .001). An artery vein angle ≥26 degrees (>95th percentile for controls) was measured in 52% recipients. Artery vein angle was higher in twin-twin transfusion syndrome stage 3R vs 1 (P = .001). Artery vein angle increased with increasing umbilical arterial pulsatility index (P < .001), and decreased with increasing resistance index (P = .02) after adjusting for gestational age. Interrater agreements to categorize abnormal artery vein angle values was 95% (P < .001). Abnormal ductus venosus Doppler and elevated recipient amniotic fluid N-terminal pro-brain natriuretic peptide/protein levels correlated significantly with artery vein angle. Abnormal artery vein angles were associated with decreased indexed cardiac output, lower tissue Doppler velocities, higher right-sided Tei indices, and severe tricuspid regurgitation.

CONCLUSION

Umbilical arterial lengthening occurs in 52% of recipients and is associated with abnormal Doppler flows, low systolic tissue Doppler velocities, reduced cardiac output, and elevated markers of cardiac failure. This may reflect chronicity and severity of hypertension in the recipient fetus. Further research is needed to explore the mechanisms of elongation and long-term implications.

Aortic isthmus shunt dynamics in normal and complicated monochorionic pregnancies

OBJECTIVE

To study fetal aortic isthmus (AoI) shunt dynamics in monochorionic (MC) twins.

METHODS

Normal and complicated MC pregnancies were prospectively enrolled. The relationship of isthmus flow index (IFI) with Doppler parameters of umbilical artery (UA), descending aorta, middle cerebral artery, and ductus venosus and with left and right ventricular cardiac output and stroke volume was studied.

RESULTS

The IFI was obtained in 180 examinations from 48 pregnancies (24 twin-twin transfusion syndrome, TTTS; 4 selective intrauterine growth restriction, sIUGR; 12 TTTS + sIUGR; and 8 uncomplicated). Median gestational age was 20.9 weeks. AoI diastolic flow was reversed in three cases. UA pulsatility index (PI) and ductus venosus-PI z-scores were negatively correlated with the IFI (r_s -0.40 and -0.26, respectively, p < 0.001). Regression analysis identified only UA-PI as a determinant of the IFI (p < 0.001). The IFI was significantly correlated with left ventricular cardiac output and stroke volume. It did not differ between TTTS donors and recipients. sIUGR fetuses had significantly lower IFI compared with normal-grown counterparts (p < 0.001).

CONCLUSION

In MC gestations, AoI shunting is predominantly determined by placental flow resistance, while cerebral impedance and volume status have no impact. In MC twins, the relationship between AoI flow and outcome deserves further study in the setting of sIUGR. © 2017 John Wiley & Sons, Ltd.

Fetal intrapericardial teratoma: natural history and management including successful in utero surgery

BACKGROUND

Intrapericardial teratoma is a rare, lethal tumor often detected in fetal life. Tumor mass and pericardial effusion cause cardiac tamponade that, if relieved, could be life-saving. Optimal timing of intervention and methods for effective fetal treatment are unknown.

OBJECTIVE

We describe our single-center experience with fetal intrapericardial teratoma including the first report of successful in utero surgical resection with survival to term.

STUDY DESIGN

We reviewed our database for suspected fetal intrapericardial teratoma. On fetal ultrasound and echocardiography tumor size was estimated by calculation of an ellipse and analyzed in relation to Doppler-derived fetal cardiac output, venous flow patterns, hydrops, and outcome.

RESULTS

Eight fetuses with suspected intrapericardial teratoma were seen from 2009 through 2015. Gestational age at initial presentation ranged from 21-34 (median 26) weeks. Two cases mimicked the appearance of intrapericardial teratoma, but had no serial change in cardiac output over time and were ultimately determined to be other types of tumor. In 6 cases of true intrapericardial teratoma, tumor growth was extremely rapid and associated with progressive decline in cardiac output (to <400 mL/kg/min) manifesting in hydrops and death if left untreated. One case was treated successfully at 31 weeks through ex utero intrapartum delivery with tumor resection while on placental support. Another case underwent open fetal surgery and resection at 24 weeks, with resumption of gestation until delivery at 37 weeks with excellent outcome.

CONCLUSION

Fetal intrapericardial teratoma can be successfully managed utilizing serial surveillance and by treatment in a timely manner prior to the predictable onset of hydrops, determined through increasing tumor size and a declining cardiac output. Surgical resection in utero is possible, with good results.

Fetal Situs, Isomerism, Heterotaxy Syndrome: Diagnostic Evaluation and Implication for Postnatal Management

OPINION STATEMENT

A hallmark of vertebrate anatomy is asymmetry of structures, especially internal organs, on the left and right side of the body. Heterotaxy syndrome is the combination of correct-sided, and incorrect-sided organs. The establishment of the left-right axis is an early event in vertebrate embryogenesis. Failure to establish this axis has numerous consequences for later development and can result in a wide range of potential defects. Congenital heart disease is among the more frequent and serious problems. Heterotaxy syndrome is diagnosed prenatally with increasing frequency due to improved screening practices. The key to proper management of fetal heterotaxy syndrome is reliable determination of left and right in the fetus, a thorough understanding of associated defects and comprehensive imaging.

Reduced fetal brain fissures depth in fetuses with congenital heart diseases

OBJECTIVE

To screen and detect cortex gyration in fetuses with congenital heart disease (CHD) using Ultrasonography (US) during routine obstetric scans.

METHODS

The depth of the Sylvian fissure (SF), parieto-occipital fissure (POF), and calcarine (CF) fissure were prospectively serially measured and compared in 45 fetuses with CHD and 45 normal fetuses. Cardiac hemodynamic parameters, including aortic valve diameter (AV), pulmonary valve diameter (PV), velocity time integral of the aortic valve (VTIav), and velocity time integral of the pulmonary valve (VTIpv), were recorded. Correlations between the fissure depths and the prenatal cardiac hemodynamic parameters and postnatal neurodevelopmental scores were assessed.

RESULTS

SF, POF, and CF were decreased in CHD fetuses compared with the controls in late of pregnancy (P < 0.01). The diagnostic category was independently associated with smaller fissure depths in fetuses with CHD (adjusted R²  = 0.472 for SF, 0.465 for POF, and 0.425 for CF). Correlations were observed between small fissure depths and decreased left heart hemodynamic parameters (AV and VTIav) in fetuses with CHD. The SF depth was positively correlated with the neurodevelopmental scores (P < 0.01).

CONCLUSIONS

US can be used to screen for abnormal fetal brain cortex development during routine obstetric scans and to evaluate the maturation progress during close follow-up. © 2016 John Wiley & Sons, Ltd.

Guidelines for the Use of Echocardiography in the Evaluation of a Cardiac Source of Embolism

Embolism from the heart or the thoracic aorta often leads to clinically significant morbidity and mortality due to transient ischemic attack, stroke or occlusion of peripheral arteries. Transthoracic and transesophageal echocardiography are the key diagnostic modalities for evaluation, diagnosis, and management of stroke, systemic and pulmonary embolism. This document provides comprehensive American Society of Echocardiography guidelines on the use of echocardiography for evaluation of cardiac sources of embolism. It describes general mechanisms of stroke and systemic embolism; the specific role of cardiac and aortic sources in stroke, and systemic and pulmonary embolism; the role of echocardiography in evaluation, diagnosis, and management of cardiac and aortic sources of emboli including the incremental value of contrast and 3D echocardiography; and a brief description of alternative imaging techniques and their role in the evaluation of cardiac sources of emboli. Specific guidelines are provided for each category of embolic sources including the left atrium and left atrial appendage, left ventricle, heart valves, cardiac tumors, and thoracic aorta. In addition, there are recommendation regarding pulmonary embolism, and embolism related to cardiovascular surgery and percutaneous procedures. The guidelines also include a dedicated section on cardiac sources of embolism in pediatric populations.

Estimated combined cardiac output and laser therapy for twin-twin transfusion syndrome

INTRODUCTION

Twin-twin transfusion syndrome (TTTS) is the major cause for fetal demise in monochorionic diamniotic pregnancies. Estimated combined cardiac output (CCO) has not been studied in this setting. The primary aims of this study were to compare CCO in twin donor and recipient fetuses and assess differences in CCO before and after laser coagulation therapy. A secondary aim was to evaluate the relationship of CCO with perinatal mortality, defined as intrauterine or neonatal mortality (≤30 days of age) in fetuses that underwent laser coagulation therapy.

METHODS

We performed a retrospective review of fetuses with TTTS who received echocardiograms prior to laser therapy. Prelaser echocardiograms were performed in 66 fetuses, of which 45 (21 donor and 24 recipient) survived to the postlaser echocardiogram.

RESULTS

Donor CCO increased from a mean of 487±137 mL/min/kg prelaser to 592±128 mL/min/kg postlaser (P=.025). There was no significant change in mean recipient CCO from prelaser 551±165 mL/min/kg to postlaser 575±112 mL/min/kg (P=.564). In recipient fetuses, higher prelaser CCO correlated with increasing Quintero stage (P=.010) and perinatal mortality (P=.003). Thirty-day postnatal outcome data were available for 38 fetuses, of whom 34 (89%) survived. Amongst survivors, 25 (74%) experienced an increase in CCO, while 9 (26%) experienced a decrease in CCO (P=.010). Donor fetuses had higher CCO after laser therapy.

CONCLUSIONS

Higher prelaser CCO in recipient fetuses may indicate more advanced disease. Fetuses who exhibit a decrease in CCO after therapy laser may be at higher risk for perinatal mortality.

Aortic distensibility as a surrogate for intertwin pulse pressure differences in monochorionic pregnancies with and without twin-twin transfusion syndrome

OBJECTIVES

Twin-twin transfusion syndrome (TTTS) complicates 10-15% of monochorionic diamniotic (MCDA) twin pregnancies. The donor response to hypovolemia allows the transfer of vasoactive mediators to the recipient, causing increased recipient afterload and hypertension. Our objective was to apply a novel speckle-tracking technique to measure the aortic fractional area change (AFAC) during the cardiac cycle in MCDA twins with and without TTTS, and identify intertwin differences in AFAC and parameters of cardiac function.

METHODS

High-frame rate four-chamber views of the fetal heart, including the mid-thoracic aorta, were collected prospectively in MCDA twin pairs referred to our center between June 2014 and April 2015. Using speckle-tracking software, the endovascular border of the aorta was traced manually during systole, with guidance on cardiac cycle timing by anatomical M-mode. AFAC, defined as the difference between maximum and minimum area divided by minimum area, expressed as a percentage, was calculated offline and averaged over three cardiac cycles. Tissue Doppler and displacement were used to measure long-axis cardiac function. Intra- and interclass correlation coefficients were used to test observer variability.

RESULTS

Fifty-one MCDA twin pregnancies were included, comprising uncomplicated MCDA (n = 14), TTTS Stages 1/2 (n = 21) and TTTS Stages 3/4 (n = 16). Median gestational age was 20.4 (range, 16.2-27.5) weeks. Mean ± SD heart rate was 142.6 ± 7.2 bpm with no significant intertwin pair differences. AFAC was significantly higher in recipients than in donors of TTTS pairs (Stages 1/2: 72.3 ± 29.9% vs 43.7 ± 19.3%, P < 0.001; Stages 3/4: 75.2 ± 29.2% vs 42.5 ± 18.4%, P = 0.002), consistent with higher recipient pulse pressure. No intertwin differences in AFAC were seen in uncomplicated MCDA pairs. Inter- and intraclass correlation coefficients for AFAC were 0.894 and 0.888. AFAC correlated significantly with combined cardiac output (r = 0.252, P = 0.011) and left and right E/E' ratio (left: r = 0.302, P = 0.004; right: r = 0.247, P = 0.030).

CONCLUSION

AFAC is a quantifiable and reproducible method to assess aortic distensibility and is a promising tool to monitor the response to prelaser therapeutic interventions in pregnancies with TTTS. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.

Can fetal left ventricular modified myocardial performance index predict adverse perinatal outcomes in intrahepatic cholestasis of pregnancy?

OBJECTIVE

To investigate fetal left ventricular function using the left ventricular modified myocardial performance index (mod-MPI) and E wave/A wave peak velocity (E/A) ratio, and to explore the success of mod-MPI in the prediction of adverse perinatal outcomes in intrahepatic cholestasis of pregnancy (ICP).

METHODS

Forty-one ICP cases were compared with 41 gestational age-matched healthy controls. Opening and closing clicks of the mitral and aortic valves were used to define the three time periods [ejection time (ET), isovolumetric contraction time (ICT) and isovolumetric relaxation time (IRT)], which were employed in the calculation of mod-MPI [mod-MPI = (ICT + IRT)/ET]. The E/A ratio was calculated as well.

RESULTS

Fetal left ventricular mod-MPI values were significantly higher in the ICP group compared to controls (0.56 ± 0.09 versus 0.37 ± 0.04, p < 0.001), whereas the E/A ratio was lower (0.62 ± 0.11 versus 0.69 ± 0.10, p = 0.011). The optimal cutoff level for mod-MPI in prediction of adverse perinatal outcomes was >0.48 [sensitivity: 81.8%, specificity: 67.6%, area under the curve (AUC): 0.750, 95% CI: 0.613-0.887, p = 0.008].

CONCLUSIONS

Fetuses of ICP cases have significant left ventricular dysfunction. Mod-MPI can be used in the prediction of adverse perinatal outcomes in ICP.

Integration of Life-Stage Physiologically Based Pharmacokinetic Models with Adverse Outcome Pathways and Environmental Exposure Models to Screen for Environmental Hazards

A computational framework was developed to assist in screening and prioritizing chemicals based on their dosimetry, toxicity, and potential exposures. The overall strategy started with contextualizing chemical activity observed in high-throughput toxicity screening (HTS) by mapping these assays to biological events described in Adverse Outcome Pathways (AOPs). Next, in vitro to in vivo (IVIVE) extrapolation was used to convert an in vitro dose to an external exposure level, which was compared with potential exposure levels to derive an AOP-based margins of exposure (MOE). In this study, the framework was applied to estimate MOEs for chemicals that can potentially cause developmental toxicity following a putative AOP for fetal vasculogenesis/angiogenesis. A physiologically based pharmacokinetic (PBPK) model was developed to describe chemical disposition during pregnancy, fetal, neonatal, and infant to adulthood stages. Using this life-stage PBPK model, maternal exposures were estimated that would yield fetal blood levels equivalent to the chemical concentration that altered in vitro activity of selected HTS assays related to the most sensitive vasculogenesis/angiogenesis putative AOP. The resulting maternal exposure estimates were then compared with potential exposure levels using literature data or exposure models to derive AOP-based MOEs.

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.

Fetal left modified myocardial performance index measured by the Auto Mod-MPI system: development of reference values and application to recipients of twin-to-twin transfusion syndrome

OBJECTIVES

To establish normal reference ranges for the fetal left modified myocardial performance index (Mod-MPI) measured by the Auto Mod-MPI system and evaluate Mod-MPI changes in recipients of twin-to-twin transfusion syndrome (TTTS) before and after fetoscopic laser coagulation.

METHODS

This was a prospective longitudinal study of normal singleton fetuses from 12.0 to 40.0 weeks of gestation. TTTS cases treated by laser coagulation were reviewed for Mod-MPI measurements of recipients. All measurements were performed using the Auto Mod-MPI system by a single experienced operator.

RESULTS

Among a total 447 examinations from 222 fetuses, we were unable to measure the Mod-MPI in two cases, and therefore, 445 examinations were analyzed. The median Mod-MPI consistently increased from 0.44 to 0.56 throughout gestation. The median isovolumetric contraction time (ICT) and isovolumetric relaxation time (IRT) also increased with advancing gestational age. The ejection time (ET) increased until 27 weeks of gestation and decreased thereafter. In the 30 recipients, Mod-MPI, ICT, and IRT increased before laser coagulation and significantly decreased after laser coagulation.

CONCLUSION

Normal reference values for left Mod-MPI were established using the Auto Mod-MPI system, and these might be useful for assessing cardiac function in TTTS. © 2016 John Wiley & Sons, Ltd.