Reference values for variables of fetal cardiocirculatory dynamics at 11-14 weeks of gestation

Assessment of fetal cardiac function in early fetal life: feasibility, reproducibility, and early fetal nomograms

BACKGROUND

Fetal cardiology has shown a rapid development in the past decades. Fetal echocardiography is not only used for the detection of structural anomalies but also to assess fetal cardiac function. Assessment of the fetal cardiac function is performed mostly in the second and third trimesters. The study of fetal cardiac function at the end of first trimester has not been investigated properly, and there is a lack of reference values at early gestational weeks.

OBJECTIVE

This study aimed to assess if the measurement of time-related parameters of cardiac function in the left ventricle of the fetal heart is feasible and reproducible at the end of the first trimester. If possible, we provide nomograms of these parameters from 11 to 13+6 gestational weeks.

STUDY DESIGN

We conducted a prospective observational study from March to September 2022. The study was carried out in 2 hospitals (Hospital Universitari Dexeus, Barcelona, and Hospital VITAHS 9 Octubre, Valencia, Spain). The scans were performed by 3 specialists in fetal medicine. The exclusion criteria were fetal cardiac rhythm abnormalities, abnormal nuchal translucency, abnormal ductus venosus, fetal malformations, stillbirth, estimated fetal weight <10 percentile, diabetes, and gestational hypertensive disorders. The cardiac function parameters studied in the left ventricle were isovolumetric contraction time, isovolumetric relaxation time, ejection time, filling time, cycle time, myocardial performance index, ejection time fraction, and filling time fraction. We study the feasibility and intra- and interobserver reproducibility of these parameters using the interclass correlation coefficient. Nomograms were created and the percentiles of the values of the different parameters were calculated.

RESULTS

A total of 409 cases were recruited but only 296 could be included in the statistical analysis once the exclusion criteria were applied. The intraobserver reproducibility study was excellent (interclass correlation coefficient >0.900), and the interobserver reproducibility study was good (interclass correlation coefficient >0.700). The data regression analysis showed that cycle time, filling time, isovolumetric contraction time, and filling time fraction increased with gestational age, whereas ejection time fraction decreased with gestational age and myocardial performance index (mean, 0.43±0.08), isovolumetric relaxation time (mean, 0.04±0.01), and ejection time (mean, 0.16±0.01) remained constant from 11 to 13 weeks.

CONCLUSION

The study of fetal cardiac function is feasible and reproducible at 11 to 13+6 gestational weeks. Nomograms of the studied parameters are provided.

A Reduction in Antenatal Steroid Dose Was Associated with Reduced Cardiac Dysfunction in a Sheep Model of Pregnancy

Despite widespread use, dosing regimens for antenatal corticosteroid (ACS) therapy are poorly unoptimized. ACS therapy exerts a programming effect on fetal development, which may be associated with an increased risk of cardiovascular disease. Having demonstrated that low-dose steroid therapy is an efficacious means of maturing the preterm lung, we hypothesized that a low-dose steroid exposure would exert fewer adverse functional and transcriptional changes on the fetal heart. We tested this hypothesis using low-dose steroid therapy (10 mg delivered to the ewe over 36 h via constant infusion) and compared cardiac effects with those of a higher dose treatment (30 mg delivered to the ewe over 24 h by intramuscular injection; simulating currently employed clinical ACS regimens). Fetal cardiac function was assessed by ultrasound on the day of ACS treatment initiation. Transcriptomic analyses were performed on fetal myocardial tissue. Relative to saline control, fetuses in the higher-dose clinical treatment group had significantly lower ratios between early diastolic ventricular filling and ventricular filling during atrial systole, and showed the differential expression of myocardial hypertrophy-associated transcripts including βMHC, GADD45γ, and PPARγ. The long-term implications of these changes remain unstudied. Irrespective, optimizing ACS dosing regimens to maximize respiratory benefit while minimizing adverse effects on key organ systems, such as the heart, offers a means of improving the acute and long-term outcomes associated with this important obstetric therapy.

Reference values for ductus venosus Doppler velocity indices between 11 and 13+6 weeks of gestation: A single-center prospective study in Iran

Background

This study aimed to investigate reference Doppler velocimetry indices (DVIs) of the fetal ductus venosus (DV) during 11-13 + 6 gestational weeks.

Materials and Methods

In a prospective observation over referrals to a single tertiary care center in a 2-year interval, normal singleton pregnancies with fetal crown-rump lengths (CRLs) of 43-80 mm were examined by a single experienced sonographer for their DV pulsatility index (DVPI), DV resistance index (DVRI), and S-wave maximum velocity/A-wave minimum velocity (S/A ratio). Multinomial and quantile regression functions were used to analyze the effect of gestational age (estimated by CRL) on reference values (5^th and 95^th percentiles of the distribution in each gestational day/week). P < 0.05 was considered significant.

Results

Over a sample of 415 participants with a mean/median gestational age of 12 + 1 weeks, no significant correlations were found between the CRL and DVIs using multinomial regression functions (linear model best fitted for all [DVPI: B coefficient = 0.001, P = 0.235] [DVRI: B coefficient = 0.001, P = 0.287] [DV S/A: B coefficient = 0.010, P = 283]). Quantile regression analyses of DVIs' reference values were nonsignificant across the CRL range except for the DVRI ([5^th regression line: coefficient = -0.004, P = 0.018] [95^th regression line: coefficient = -0.001, P = 0.030]).

Conclusion

Reference values for DVPI, DVRI, and DV S/A ratios were established as 0.80-1.39, 0.62-0.88, and 2.57-6.70, respectively. Future meta-analyses and multicenter studies are required to incorporate DV DVIs into an updated universal version of the practice.

Fetal Cardiac Function: Myocardial Performance Index

The Myocardial Performance Index (MPI) or Tei index, presented by Tei in 1995, is the ratio of the sum of the duration of the isovolumetric contraction time (ICT) and isovolumetric relaxation time (IRT) to the duration of the ejection time (ET). The Modified Myocardial Performance Index (Mod-MPI), proposed in 2005, is considered a reliable and useful tool in the study of fetal heart function in several conditions, such as growth restriction, twin-twin transfusion syndrome, maternal diabetes, preeclampsia, intrahepatic cholestasis of pregnancy, and adverse perinatal outcomes. Nevertheless, clinical translation is currently limited by poorly standardised methodology as variations in the technique, machine settings, caliper placement, and specific training required can result in significantly different MPI values. This review aims to provide a survey of the relevant literature on MPI, present a strict methodology and technical considerations, and propose future research.

Nomograms of fetal cardiothoracic ratio from 17 to 37 weeks' gestation as assessed by three different measurement techniques and their correlation with gestational age

OBJECTIVE

To create nomograms for fetal cardiothoracic (CT) ratio as assessed by three different 2-dimensional sonographic measurements, including CT diameter, circumference, and area ratios, in Thai fetuses with a gestational age (GA) of 17-37 weeks, and to evaluate both their correlation with GA or biparietal diameter (BPD) and variability among the three measurement methods.

METHODS

Two-dimensional sonographic measurements of fetal CT ratio in 4-chamber view were assessed by three different measurement techniques. The 95% reference intervals and Z-scores of all measurement methods based on GA or BPD were constructed. Intraclass correlation coefficients (ICC) for the reproducibility of each technique were compared.

RESULTS

A total of 511 uncomplicated singleton pregnancies were included. The fetal CT ratio values by all measurement techniques gradually and smoothly increased with increasing GA and BPD. The fetal CT circumference ratio showed the least correlation with both GA and BPD. The intraobserver and interobserver reliability coefficients of all techniques demonstrated almost excellent agreement (all ICCs at least 0.87).

CONCLUSION

Reference intervals and Z-score reference ranges were developed using three different techniques for fetal CT ratio with a GA of 17-37 weeks. These nomograms are a simple and reliable screening tool for identifying abnormal fetal heart size.

Umbilical Artery Doppler Patterns and Right Ventricular Outflow Abnormalities in Twin-Twin Transfusion Syndrome

OBJECTIVES

To evaluate the association of abnormal Doppler velocimetric patterns in the umbilical arteries (UAs) and right ventricular outflow tract abnormalities (RVOTAs) in twin- twin transfusion syndrome (TTTS) cases.

METHODS

This retrospective study involved women who had laser surgery for TTTS between January 2012 and May 2018 at a single institution. The prevalence of an RVOTA in either twin was compared among TTTS cases in which both twins had positive end-diastolic flow (EDF) in the UA and those in which either twin had intermittent or persistent absent/reversed UA EDF. Nonparametric tests were used for comparisons. Logistic regression was performed to identify variables associated with an RVOTA in either twin, adjusted for moderate or severe tricuspid regurgitation, right ventricular hypertrophy, right ventricular systolic or diastolic dysfunction, the Quintero stage, and other confounders. P < .05 was considered significant.

RESULTS

A total of 126 consecutive TTTS cases were included. Right ventricular outflow tract abnormalities were seen in 8.7% (11of 126) of cases, all in recipient twins. Significant differences in the rate of RVOTAs in the recipient twin were seen between TTTS cases with intermittent absent/reversed UA EDF and those with positive UA EDF (26.9% [7 of 26] versus 3.7% [3 of 82]; P = .002]. However, no significant differences were noted among the other study groups. Intermittent absent/reversed UA EDF was associated with a significantly increased risk for an RVOTA (adjusted odds ratio, 20.6 [95% confidence interval, 3.1-138]; P = .002) after adjusting for confounders.

CONCLUSIONS

Intermittent changes in vascular impedance to UA flow may contribute to the pathogenesis of acquired right-sided cardiac lesions in the recipient twin affected with TTTS.

The role of first trimester fetal heart rate in the prediction of gestational diabetes: A multicenter study

OBJECTIVE

Early pregnancy models for prediction of GDM have been proposed, mostly using anamnestic and biochemical parameters. The aim of our study was to evaluate the strength of association of first trimester fetal heart rate (FHR) in predicting the development of gestational diabetes (GDM).

STUDY DESIGN

We considered in our analysis singleton non-diabetic pregnant women who underwent a first trimester screening at 11-14 weeks. Data on maternal age, BMI, cigarette smoking, NT, FHR, CRL, DV-PVI, β-hCG and PAPP-A were included in the analysis. Multivariate logistic regression analysis was used to estimate the association between maternal characteristics and first-trimester ultrasound measurements and GDM. We evaluated the efficacy of different models for the prediction of GDM.

RESULTS

We considered 603 women, of whom 199 (33%) were subsequently diagnosed with GDM. ROC analysis showed that first trimester FHR was highly predictive of GDM (AUC 0.809, 95% CI 0.769-0.849, p < 0.001). At FPR of 20%, first trimester FHR had a detection rate of 65.2% for GDM (positive likelihood ratio: 3.26; negative likelihood ratio: 0.43), which increased to 89.5% at FPR of 40% (positive likelihood ratio: 2.24; negative likelihood ratio: 0.17). When considering as threshold 162 bpm, FHR showed detection rate of 76.9%, specificity of 67.1% and negative predictive value of 85.5% for GDM.

CONCLUSION

This is the first study to highlight the potential role of first trimester FHR as early predictor of GDM. In our cohort, a threshold of 162 bpm has shown high detection rate and NPV for GDM.

Z-Score Reference Ranges for Fetal Heart Functional Measurements in a Large Brazilian Pregnant Women Sample

The objective of this study was to determine the reference values for fetal heart functional measurements at 24 and 34 weeks of gestation and to develop Z-score equations for all measurements. A single-center, prospective, cross-sectional study with normal fetuses between 24 and 34 weeks of gestation was performed. All pregnant women underwent a comprehensive fetal Doppler echocardiogram with anatomical and functional analysis. Measurements of left and right cardiac output, combined cardiac output, mitral and tricuspid valve flow, inferior vena cava flow, and pulmonary vein flow were performed. The Shapiro-Wilk test and histogram evaluation were performed on all variables. Linear regression was used to assess the relationships between measurements and gestational age. A total of 612 pregnant women with singleton and normal fetuses were included. We assessed the reference values and percentiles of cardiac function as a function of gestational age. The variables that were not normally distributed were subjected to logarithmic or square root transformation. Eleven Z-score equations were developed, with equations for left and right ventricle output and combined cardiac output that were dependent on gestational age and with other equations that were independent of gestational age. The present study produced a large database, allowing the demonstration of reference values and percentiles as well as the development of Z-score equations to facilitate the echocardiographic evaluation of fetal heart function.

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.

The effect of increased amnion volume severity on fetal Doppler indices and perinatal outcomes in idiopathic polyhydramnios

Aim: To evaluate the relationship between polyhydramnios severity and alterations in Doppler indices and perinatal outcomes in idiopathic polyhydramnios.Methods: This prospective case control study was conducted in a tertiary hospital with 173 singleton pregnancies between 29 and 41 weeks gestational age between May 2015 and December 2016. Polyhydroamnios is classified as mild (amniotic fluid index 25-30 cm), moderate (30.1-35 cm), and severe (>35 cm) and the number of the patients in mild, moderate, and severe groups were 55, 39, and 26, respectively. The results were compared with 53 healthy controls. Fetal echocardiography and Doppler measurements of the groups were made and the perinatal outcomes from each group were noted. The relationship between the results and the severity of polyhydramnios was analyzed statistically.Results: The myocardial performance index was significantly higher in the fetuses of women with severe polyhydramnios compared to the other groups (p = .006). There were statistically significant differences among the groups in terms of first and fifth minutes according to the Apgar scores (p = .011, p = .016 respectively). In the severe polyhydramnios group compared with other groups, the middle cerebral artery pulstatility index was significantly lower (p = .002), while middle cerebral artery peak systolic velocity and umbilical artery pulstatility index values were significantly higher (p = .0001, p = .045).Conclusions: Our study showed an increase in myocardial performance index and middle cerebral artery peak systolic velocity values and a decrease in middle cerebral artery pulstatility index values, especially in the severe idiopathic polyhydramnios group. Idiopathic polyhydramnios were associated with low first and fifth minute Apgar score. Additionally, the increase in umbilical artery pulstatility index value and the decrease in middle cerebral artery pulstatility index value became more apparent with the increase in amniotic fluid volume. It should be taken into consideration that brain sparing effect may develop especially in cases with severe polyhydramnios.

Evaluation of an automated fetal myocardial performance index

OBJECTIVE

To compare automated measurements of the fetal left myocardial performance index (MPI) with manual measurements for absolute value, repeatability and waveform acceptability.

METHODS

This was a multicenter international online study using images from uncomplicated, morphologically normal singleton pregnancies (16-38 weeks' gestation). Single Doppler ultrasound cardiac cycle images of 25 cases were selected, triplicated and randomized (n = 75). Six senior observers, unaware of the repetition of images, manually calculated MPI for each waveform and the results were compared with automation. Intraobserver repeatability and interobserver reproducibility were assessed using intraclass correlation coefficients (ICCs) and 95% CI. The agreement between each observer's manual MPI measurements and corresponding automated measurements was evaluated using Bland-Altman plots and ICCs with 95% CI. The degree of variation between experts in the classification of fetal MPI waveform quality was assessed using individual cardiac cycle left MPI images previously classified by two authors as 'optimal', 'suboptimal' or 'unacceptable', with 30 images selected for each quality group. Ten images in each category were duplicated and the resulting 120 images were randomized and then classified online by five observers. The kappa statistic (κ) was used to demonstrate interobserver and intraobserver agreement and agreement of classifications by the five observers.

RESULTS

The automated measurement software returned the same value for any given image, resulting in an ICC of 1.00. Manual measurements had intraobserver repeatability ICC values ranging from 0.69 to 0.97, and the interobserver reproducibility ICC was 0.78. Comparison of automated vs manual MPI absolute measurements for each observer gave ICCs ranging from 0.77 to 0.96. Interobserver image quality classification agreement gave k = 0.69 (P < 0.001), and the intraobserver agreement was variable (κ ranging from 0.40 to 0.81).

CONCLUSIONS

Automated fetal MPI provides superior repeatability and reproducibility to manual methodology. Additionally, experts vary significantly when classifying suitability of fetal MPI waveforms. Automated MPI may facilitate clinical translation by removing human subjectivity. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.

Ductus venosus Doppler in the assessment of fetal cardiovascular health: an updated practical approach

The ductus venosus has a central role in the distribution of highly oxygenated umbilical venous blood to the heart. Its waveform is related to the pressure-volume changes in the cardiac atria and it is therefore important in the monitoring of any fetal condition that may affect forward cardiac function. The cardiovascular parameters that can influence forward cardiac function include afterload, myocardial performance and preload. Decreased forward flow during atrial systole (a-wave) is the most sensitive and ubiquitous finding when any of these parameters is affected. In contrast, decreased forward velocities during end-systolic relaxation (v-wave) are more specifically related to myocardial performance. The ductus venosus pulsatility index alone does not accurately reflect cardiac function, and in cases of suspected fetal cardiac dysfunction, echocardiography is required to identify the underlying mechanism. The role of ductus venosus Doppler in the assessment of fetal growth restriction, supraventricular tachycardia, fetal hydrops, complicated monochorionic twins and congenital heart disease is discussed with these considerations in mind.

Human embryonic cardiovascular function

INTRODUCTION

This review presents an overview of descriptive knowledge on human embryonic cardiovascular physiology mostly based on noninvasive assessment by Doppler ultrasonography. Our objective was to identify and analyze published studies on embryonic cardiovascular function, and summarize available knowledge in this field.

MATERIAL AND METHODS

Citations related to human embryonic cardiovascular function were searched in PubMed, EMBASE, CINAHL and Web of Science using keywords and MeSH terms without any time limitation. The search was restricted to English language articles. Abstracts were screened and full texts of relevant articles were obtained. All articles that reported on physiological aspects of human embryonic cardiovascular function were included. Studies reporting on cardiovascular function after 10 weeks of gestation were excluded. Data were synthesized and presented narratively.

RESULTS

We identified 10 studies that had evaluated cardiovascular function and/or hemodynamics in human embryos at ≤10 weeks of gestation. All of these reported only certain aspects of embryonic cardiovascular function. Embryonic heart rate is associated significantly with gestational age and increases from 6 to 10 weeks of gestation. Cardiac inflow is monophasic during the embryonic period and atria appear to generate higher force during contraction compared with ventricles. Both ventricular inflow and outflow velocities increase with advancing gestation, whereas the Tei index decreases significantly. During the embryonic period, placental blood flow increases with gestation, but absent umbilical artery diastolic flow and umbilical venous pulsations are normal phenomena.

CONCLUSION

There are important differences in normal cardiovascular function between the embryonic and fetal stages of human in utero development.

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.

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.

Reference ranges of myocardial performance index from 12 to 40 weeks of gestation

OBJECTIVE

To establish reference ranges of fetal myocardial performance index (MPI) in normal singleton pregnancies from 12 to 40 weeks gestation.

DESIGN

Prospective descriptive study.

SETTING

A tertiary care teaching center in the Northern part of Thailand.

PARTICIPANTS

A total of 562 normal singleton pregnancies at 12-40 weeks of gestation.

INTERVENTION

Fetal echocardiography was performed for isovolumetric contraction time, isovolumetric relaxation time, ejection time and MPI by one experienced sonographer, using strict criteria for measurement. The measured MPI values were regressed against gestational age (GA) and biparietal diameter (BPD) to determine the best-fitted model.

PRIMARY OUTCOME MEASURES

MPI for each gestational week and each BPD point (cm).

RESULTS

A total of 562 measurements were successfully obtained with good-quality Doppler tracings and complete data for analysis. Predicted mean of MPI for GA and BPD is as follows: predicted mean MPI = 0.404 + 0.004 × GA (weeks) (r (2) = 0.143, p < 0.001) and = 0.419 + 0.015 × BPD (cm) (r (2) = 0.139, p < 0.001) as functions of GA and BPD, respectively. The predicted SD of MPI for GA and BPD is constant throughout pregnancy, 0.071348 and 0.073440, respectively.

CONCLUSION

MPI is significantly increased with GA. The reference ranges of MPI according to GA and BPD, as a marker in evaluating global cardiac function between 12 and 40 weeks of gestation was constructed.

Correlation analysis of ductus venosus velocity indices and fetal cardiac function

OBJECTIVE

To examine the relationships between the ductus venosus (DV) pulsatility index for veins (PIV), individual DV velocity ratios and diastolic and global myocardial cardiac function.

METHODS

Doppler measurements of the DV, atrioventricular (AV) valves and ventricular in- and outflow were analyzed. The DV-PIV and velocity ratios for individual phases (systole (S), end-systolic relaxation (v), early diastole (D), atrial systole (a), and S/v, S/D, S/a, v/D, v/a and D/a ratios) were calculated. The ratio of early and late diastolic peak velocities across AV valves was calculated (E/A ratio). Left modified myocardial performance index (MPI) was calculated from time intervals between valve clicks defining isovolumetric contraction/relaxation and ejection times. All values were transformed to Z-scores. The distributions of DV velocity ratios and DV-PIV were correlated with cardiac Doppler parameters.

RESULTS

A total of 1163 examinations from 213 fetuses, most of which were at risk for cardiac dysfunction, were included in the study. In 742 the PIV was normal and in 421 PIV was elevated > 2 SD above the normal mean. The DV-PIV correlated with velocity ratios (P < 0.0001) but not with E/A ratios and the MPI. S/v and v/D ratios were related to tricuspid and mitral E/A ratios and left ventricular MPI. The S/D ratio was only related to both E/A ratios. There was no relationship between a-wave-related velocity ratios and cardiac function.

CONCLUSIONS

Velocity ratios of the DV show relationships with cardiac function that are not reflected by the PIV alone. In cases of suspected fetal cardiac dysfunction based on elevated DV-PIV, analysis of velocity ratios or direct cardiac evaluation is suggested to determine the underlying pathophysiology.

Echocardiographic assessment of embryonic and fetal mouse heart development: a focus on haemodynamics and morphology

Background. Heart development is a complex process, and abnormal development may result in congenital heart disease (CHD). Currently, studies on animal models mainly focus on cardiac morphology and the availability of hemodynamic data, especially of the right heart half, is limited. Here we aimed to assess the morphological and hemodynamic parameters of normal developing mouse embryos/fetuses by using a high-frequency ultrasound system. Methods. A timed breeding program was initiated with a WT mouse line (Swiss/129Sv background). All recordings were performed transabdominally, in isoflurane sedated pregnant mice, in hearts of sequential developmental stages: 12.5, 14.5, and 17.5 days after conception (n = 105). Results. Along development the heart rate increased significantly from 125 ± 9.5 to 219 ± 8.3 beats per minute. Reliable flow measurements could be performed across the developing mitral and tricuspid valves and outflow tract. M-mode measurements could be obtained of all cardiac compartments. An overall increase of cardiac systolic and diastolic function with embryonic/fetal development was observed. Conclusion. High-frequency echocardiography is a promising and useful imaging modality for structural and hemodynamic analysis of embryonic/fetal mouse hearts.

Environmental origins of congenital heart disease: the heart-placenta connection

Although the mammalian embryo is well protected in the uterus, environmental chemicals, drugs, and maternal nutritional imbalances can interfere with regulatory pathways directing placental and embryonic development early in gestation. Embryonic cells are most susceptible to environmental influences during cellular specification and differentiation stages. Because biochemical differentiation precedes morphological outcome often by days, the period of susceptibility to environmental chemicals expectedly precedes visible morphogenic effects. The cellular mechanisms by which drugs and other environmental factors disrupt embryonic development and induce cardiac abnormalities have remained undefined.

Antegrade late diastolic arterial blood flow in the fetus: insight into fetal atrial function

OBJECTIVE

The purpose of this study was to examine the presence and frequency of antegrade late diastolic arterial blood flow (ALDAF) in the fetus and to determine its contribution to cardiac output.

STUDY DESIGN

We evaluated the presence of ALDAF in 457 fetal and 21 postnatal echocardiograms. The timing of ALDAF to the ventricular systolic Doppler recording (ALDAF-V) was compared with the mechanical atrioventricular interval and, in neonates, the electrical PR interval. Velocity time integrals of ALDAF and the ventricular systolic Doppler signals were measured, and the percent contribution of ALDAF was calculated.

RESULTS

ALDAF was observed in 365 of 457 studies and included all <11 weeks' gestations. Strong correlation between ALDAF-V, atrioventricular interval, and electrical PR interval suggests that ALDAF coincides with atrial contraction. ALDAF contributed substantially to cardiac output in early gestation with later decline.

CONCLUSION

ALDAF results from atrial contraction. Increasing gestational age results in less ALDAF, and reduced ALDAF contribution to cardiac output likely due to improved diastolic function.

The heart-placenta axis in the first month of pregnancy: induction and prevention of cardiovascular birth defects

Extrapolating from animal studies to human pregnancy, our studies showed that folate (FA) deficiency as well as one-time exposure to environmental factors in the first two to three weeks of human gestation can result in severe congenital heart defects (CHDs). Considering that approximately 49% of pregnancies are unplanned, this period of pregnancy can be considered high-risk for cardiac, as well as for neural, birth defects, as the woman usually is not aware of her pregnancy and may not yet be taking precautionary actions to protect the developing embryo. Using avian and mouse vertebrate models, we demonstrated that FA supplementation prevents CHD induced by alcohol, lithium, or elevation of the metabolite homocysteine, a marker for FA deficiency. All three factors affected the important Wnt signaling pathway by suppressing Wnt-mediated gene expression in the heart fields, resulting in a delay of cardiomyocyte migration, cardiomyogenesis, and CHD. Optimal protection of cardiogenesis was observed to occur with FA supplementation provided upon morning after conception and at higher doses than the presently available in prenatal vitamin supplementation. Our studies demonstrate pathways and cell processes that are involved with protection of one-carbon metabolism during heart development.

Reproducibility of constituent time intervals of right and left fetal modified myocardial performance indices on pulsed Doppler echocardiography: a short report

OBJECTIVE

To assess reproducibility of constituent time intervals measured by pulsed Doppler echocardiography for calculation of the right and left fetal myocardial performance indices (MPIs).

METHODS

This was a prospective study of 30 normal singleton pregnancies (19-36 weeks). In each, five different time intervals were measured from the Doppler waveform and four repeated measures were taken for each time interval. Three were from the left heart: isovolumetric contraction time (ICT), isovolumetric relaxation time (IRT) and ejection time (ET); two were from the right heart: 'a-interval' and 'b-interval'. The left and right modified MPIs (Mod-MPIs) generated by these constituent time intervals were also evaluated. Two operators evaluated the reproducibility of all measures.

RESULTS

There was generally good intra- and interobserver reproducibility for all time intervals and resultant Mod-MPIs: ICT, range, 19-43 ms with intraclass correlation coefficient (ICC), 0.91 (95% CI, 0.85-0.95); ET, range, 160-184.8 ms with ICC, 0.90 (95% CI, 0.84-0.95); IRT, range, 35.8-48.5 ms with ICC, 0.67 (95% CI, 0.52-0.81); a-interval, range 208-265 ms with ICC, 0.89 (95% CI, 0.82-0.94); b-interval, range, 163.1-188.3 ms with ICC, 0.82 (95% CI, 0.71-0.90); left Mod-MPI, range, 0.33-0.48 with ICC, 0.84 (95% CI, 0.74-0.91); right Mod-MPI, range, 0.21-0.49 with ICC, 0.82 (95% CI, 0.71-0.90). The 95% limits of agreement showed no statistically significant difference in measurements between the two examiners for all time intervals.

CONCLUSION

This is the first study to evaluate the reproducibility of the component time intervals of both right and left fetal Mod-MPIs in the second and third trimesters and supports the reproducibility of fetal functional cardiac assessment. The IRT is the main source of variation for the left Mod-MPI so should be the focus of further investigation. Even using two separate pulsed-wave Doppler gates and therefore separate cardiac cycles, the right Mod-MPI is reproducible.