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

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

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

Role of artificial-intelligence-assisted automated cardiac biometrics in prenatal screening for coarctation of aorta

OBJECTIVE

Although remarkable strides have been made in fetal medicine and the prenatal diagnosis of congenital heart disease, around 60% of newborns with isolated coarctation of the aorta (CoA) are not identified prior to birth. The prenatal detection of CoA has been shown to have a notable impact on survival rates of affected infants. To this end, implementation of artificial intelligence (AI) in fetal ultrasound may represent a groundbreaking advance. We aimed to investigate whether the use of automated cardiac biometric measurements with AI during the 18-22-week anomaly scan would enhance the identification of fetuses that are at risk of developing CoA.

METHODS

We developed an AI model capable of identifying standard cardiac planes and conducting automated cardiac biometric measurements. Our data consisted of pregnancy ultrasound image and outcome data spanning from 2008 to 2018 and collected from four distinct regions in Denmark. Cases with a postnatal diagnosis of CoA were paired with healthy controls in a ratio of 1:100 and matched for gestational age within 2 days. Cardiac biometrics obtained from the four-chamber and three-vessel views were included in a logistic regression-based prediction model. To assess its predictive capabilities, we assessed sensitivity and specificity on receiver-operating-characteristics (ROC) curves.

RESULTS

At the 18-22-week scan, the right ventricle (RV) area and length, left ventricle (LV) diameter and the ratios of RV/LV areas and main pulmonary artery/ascending aorta diameters showed significant differences, with Z-scores above 0.7, when comparing subjects with a postnatal diagnosis of CoA (n = 73) and healthy controls (n = 7300). Using logistic regression and backward feature selection, our prediction model had an area under the ROC curve of 0.96 and a specificity of 88.9% at a sensitivity of 90.4%.

CONCLUSIONS

The integration of AI technology with automated cardiac biometric measurements obtained during the 18-22-week anomaly scan has the potential to enhance substantially the performance of screening for fetal CoA and subsequently the detection rate of CoA. Future research should clarify how AI technology can be used to aid in the screening and detection of congenital heart anomalies to improve neonatal outcomes. © 2024 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Pre-intervention myocardial stress is a good predictor of aortic valvoluplasty outcome for fetal critical aortic stenosis and evolving HLHS

Fetal critical aortic stenosis with evolving hypoplastic left heart syndrome (CAS-eHLHS) causes biomechanical and functional aberrations, leading to a high risk of progression to hypoplastic left heart syndrome (HLHS) at birth. Fetal aortic valvuloplasty (FAV) can resolve outflow obstruction and may reduce progression risk. However, it is currently difficult to accurately predict which patients will respond to the intervention and become functionally biventricular (BV) at birth, as opposed to becoming functionally univentricular (UV). This prediction is important for patient selection, parental counselling, and surgical planning. Therefore, we investigated whether biomechanics parameters from pre-FAV image-based computations could robustly distinguish between CAS-eHLHS cases with BV or UV outcomes in a retrospective cohort. To do so we performed image-based finite element biomechanics modelling of nine CAS-eHLHS cases undergoing intervention and six healthy fetal control hearts, and found that a biomechanical parameter, peak systolic myofibre stress, showed a uniquely large difference between BV and UV cases, which had a larger magnitude effect than echocardiography parameters. A simplified equation was derived for quick and easy estimation of myofibre stress from echo measurements via principal component analysis. When tested on a retrospective cohort of 37 CAS-eHLHS cases, the parameter outperformed other parameters in predicting UV versus BV outcomes, and thus has a high potential of improving outcome predictions, if incorporated into patient selection procedures. Physiologically, high myocardial stresses likely indicate a healthier myocardium that can withstand high stresses and resist pathological remodelling, which can explain why it is a good predictor of BV outcomes. KEY POINTS: Predicting the morphological birth outcomes (univentricular versus biventricular) of fetal aortic valvuloplasty for fetal aortic stenosis with evolving HLHS is important for accurate patient selection, parental counselling and management decisions. Computational simulations show that a biomechanics parameter, pre-intervention peak systolic myofibre stress, is uniquely robust in distinguishing between such outcomes, outperforming all echo parameters. An empirical equation was developed to quickly compute peak systolic myofibre stress from routine echo measurements and was the best predictor of outcomes among a wide range of parameters tested.

Association of Gestational Age at Birth With Left Cardiac Dimensions at Near-Term Corrected Age Among Extremely Preterm Infants

BACKGROUND

Remodeling and altered ventricular geometry have been described in adults born preterm. Although they seem to have an adverse cardiac phenotype, the impact of various degrees of prematurity on cardiac development has been scarcely reported. In this study, we evaluated the impact of gestational age (GA) at birth on cardiac dimensions and function at near-term age among extremely preterm infants.

METHODS

This is a retrospective single-center cohort study of infants born at <29 weeks of GA between 2015 and 2019. Infants with available clinically acquired echocardiography between 34 and 43 weeks were included. Two groups were investigated: those born <26 weeks and those born ≥26 weeks. All measurements were done by an expert masked to clinical data using the raw images. The primary outcome was measurements of cardiac dimensions and function based on GA group. Secondary outcomes were the association between cardiac dimensions and postnatal steroid exposure and with increments of GA at birth.

RESULTS

A total of 205 infants were included (<26 weeks, n = 102; ≥26 weeks, n = 103). At time of echocardiography, weight (2.4 ± 0.5 vs 2.5 ± 0.5 kg, P = .86) and age (37.2 ± 1.6 vs 37.1 ± 1.9 weeks, P = .74) were similar between groups. There was no difference in metrics of right-sided dimensions and function. However, left-sided dimensions were decreased in infants born <26 weeks, including systolic left ventricle (LV) diameter (1.06 ± 0.20 cm vs 1.12 ± 0.18 cm, P = .02), diastolic LV length (2.85 ± 0.37 vs 3.02 ± 0.57 cm, P = .02), and estimated LV end-diastolic volume (5.36 ± 1.69 vs 6.01 ± 1.79 mL, P = .02).

CONCLUSIONS

In our cohort of very immature infants, birth at the extreme of prematurity was associated with smaller left cardiac dimensions around 36 weeks of corrected age. Future longitudinal prospective studies should evaluate further the impact of prematurity on LV development and performance and their long-term clinical impact.

Normative change with gestation in fetal intraventricular pressure difference with color M-mode Doppler echocardiography

AIM

The intraventricular pressure difference (IVPD) is the pressure difference in early diastole from the base to the apex of the ventricle. It is a useful marker for evaluating diastolic function because of its role as a suction force. This study investigated the changes in total and segmental IVPDs in normal fetuses throughout gestation to obtain normative data equations.

METHODS

One hundred thirty-seven healthy pregnant women at 12-40 weeks of gestation were prospectively enrolled to evaluate IVPD. The color M mode was performed, and the image was evaluated using our own code to calculate the IVPD. Segmental IVPD was divided into mid to apex and base. Pearson's correlation coefficient was used to evaluate this relationship.

RESULTS

There was a significant, positive relationship between IVPD and gestational age in both ventricles (right ventricle [RV]: r = 0.800, left ventricle [LV]: r = 0.818). As for segmental IVPD, basal and mid-apical IVPD also increased with gestation in both ventricles (RV: basal, r = 0.627; mid-apical, r = 0.705; LV: basal r = 0.758; mid-apical, r = 0.756). IVPG, which was calculated as IVPD/ventricular length, also showed a weak, positive relationship with gestation in both ventricles (RV r = 0.351, p < 0.001; LV r = 0.373, p < 0.001).

CONCLUSION

The total and segmental IVPDs significantly increased linearly through time.

Fetal Hemodynamic Response to Anemia in Early Gestation: Using Hemoglobin Bart's Disease as a Study Model

OBJECTIVE

 To assess fetal hemodynamic changes in response to anemia in early gestation, using fetal Hb Bart's disease as a study model.

METHODS

 A prospective study was conducted on pregnancies at risk for fetal Hb Bart's disease at 12-14 weeks of gestation. Fetal hemodynamics were comprehensively assessed by 2D ultrasound, Doppler velocity, and cardio-STIC just prior to the invasive procedure for diagnosis. The various hemodynamic parameters of the affected and unaffected fetuses were compared.

RESULTS

 Of 56 fetuses at risk, 17 had Hb Bart's disease and 39 were unaffected. The right and combined ventricular cardiac outputs (CO) were significantly higher in the affected fetuses (0.993 vs. 1.358; p < 0.001 and 1.010 vs. 1.236; p < 0.001, respectively), whereas the left CO tended to be higher but not significantly (1.027 vs. 1.113; p = 0.058). Cardiac dimensions, middle-cerebral artery peak systolic velocity, Tei index, and isovolemic contraction time were significantly increased, while the global sphericity index was significantly decreased. Interestingly, cardiac preload, ventricular wall thickness, shortening fraction, isovolemic relaxation time, and fetal heart rate were unchanged. Four fetuses had hydropic changes, but all cardiac functions were normal.

CONCLUSION

 Fetal anemia induces hypervolemia and increases cardiac output to meet the tissue oxygen requirement, resulting in an increase in size without hypertrophy, volume load without pressure load, and a decrease in the globular sphericity index. The heart works very well but works harder, especially systolic ventricular load. Hydrops fetalis due to anemia appears not to be caused by heart failure as previously believed but rather by volume load with high vascular permeability at least in early pregnancy.

Comparison of the left and right ventricular size and systolic function of low-risk fetuses in the third trimester: Which is more dominant?

Objective

To quantify fetal cardiovascular parameters utilizing fetal-specific 2D speckle tracking technique and to explore the differences in size and systolic function of the left and right ventricles in low-risk pregnancy.

Methods

A prospective cohort study was performed in 453 low-risk single fetuses (28+0–39+6 weeks) to evaluate ventricular size [i.e., end-diastolic length (EDL), end-systolic length (ESL), end-diastolic diameter (ED), end-systolic diameter (ES), end-diastolic area, end-systolic area, end-diastolic volume (EDV), and end-systolic volume (ESV)] and systolic function [i.e., ejection fraction (EF), stroke volume (SV), cardiac output (CO), cardiac output per kilogram (CO/KG), and stroke volume per kilogram (SV/KG)].

Results

This study showed that (1) the reproducibility of the interobserver and intraobserver measurements was good to excellent (ICC 0.626–0.936); (2) with advancing gestation, fetal ventricular size and systolic function increased, whereas right ventricular (RV) EF decreased and left ventricular (LV) EF was not significantly changed; (3) LV length was longer than RV length in diastole (2.24 vs. 1.96 cm, P &lt; 0.001) and systole (1.72 vs. 1.52 cm, P &lt; 0.001); (4) LV ED-S1 and ES-S1 were shorter than the RV ED-S1 and ES-S1 (12.87 vs. 13.43 mm, P &lt; 0.001; 5.09 vs. 5.61 mm, P &lt; 0.001); (5) there were no differences between the LV and RV in EDA or EDV; (6) the mean EDV ratio of right-to-left ventricle was 1.076 (95% CI, 1.038–1.114), and the mean ESV ratio was 1.628 (95% CI, 1.555–1.701); (7) the EF, CO and SV of the LV were greater than the RV (EF: 62.69% vs. 46.09%, P &lt; 0.001; CO: 167.85 vs. 128.69 ml, P &lt; 0.001; SV: 1.18 vs. 0.88 ml, P &lt; 0.001); (8) SV and CO increased with ED-S1 and EDL, but EF was not significantly changed.

Conclusion

Low-risk fetal cardiovascular physiology is characterized by a larger RV volume (especially after 32 weeks) and greater LV outputs (EF, CO, SV, SV/KG and CO/KG).

Incidence of Fetal Myocardial Hypertrophy in Mother with Diabetes Mellitus by Using Cardio-Spatiotemporal Image Correlation (STIC) M-Mode

Objective

The aim was to demonstrate the prevalence of fetal myocardial hypertrophy (FMH) in diabetes mellitus (DM) pregnant women using spatio-temporal image correlation (STIC) M-mode.

Material and Methods

This prospective descriptive study was conducted at Bhumibol Adulyadej Hospital (BAH) Royal Thai Air Force between April and December 2022. Participants were singleton DM pregnant women with gestational age (GA) between 18 and 40 weeks who had antenatal care and delivery at BAH. DM screening was randomized blood sugar obtained from all participants. All participants underwent fetal heart exams by four-dimension ultrasound with STIC M-mode.

Results

One hundred and forty-five participants were recruited and classified as pregestational (PDM) and gestational DM (GDM) at 31 and 114 cases, respectively. The mean age of participants was 31.7 years old. Fasting blood sugar (FBS) of PDM was significantly higher than GDM (105.1 vs 87.0 mg%). GDMA2 had more elevated FBS than GDMA1 (p < 0.001). PDM had significantly greater FBS and two-hour postprandial blood sugar (2hr-PP) than GDM (105.1/87.0 and 151.5/117.9 mg%, respectively). FBS and 2hr-PP of GDMA2 were more than GDMA1 with statistical significance. Good glycemic control of GDM was significantly better than PDM. GDMA1 had better glycemic control than GDMA2 with statistical significance. Four-fifth (115/145) of participants had FMH. FMH and estimated fetal weight among PDM and GDM were comparable. Both good and poor glycemic control had similar FMH. Neonatal outcomes of FMH or non-FMH infants were similar.

Conclusion

The prevalence of FMH in diabetic pregnant women was 79.3%. Glycemic control had no correlation to FMH.

Fetal intelligent navigation echocardiography (FINE) has superior performance compared to manual navigation of the fetal heart by non-expert sonologists

OBJECTIVES

Manual and intelligent navigation (i.e. fetal intelligent navigation echocardiography or FINE) by the operator are two methods to obtain standard fetal cardiac views from spatiotemporal image correlation (STIC) volumes. The objective was to compare the performance between manual and intelligent navigation (FINE) of the fetal heart by non-expert sonologists.

METHODS

In this prospective observational study, ten sonologists underwent formal training on both navigational methods. Subsequently, they were tested on their ability to obtain nine cardiac views from five STIC volumes of normal fetal hearts (19-28 gestational weeks) using such methods. The following parameters were determined for both methods: (1) success rate of obtaining nine cardiac views; (2) mean time to obtain nine cardiac views per sonologist; and (3) maximum number of cardiac views successfully obtained for each STIC volume.

RESULTS

All fetal cardiac images obtained from 100 STIC volumes (50 for each navigational method) were reviewed by an expert in fetal echocardiography. Compared to manual navigation, FINE was associated with a significantly: (1) higher success rate of obtaining eight (excluding the abdomen view) appropriate cardiac views (92-100% vs. 56-88%; all p<0.05); (2) shorter mean time (minute:seconds) to obtain nine cardiac views (2:11 ± 0:37 vs. 15:49 ± 7:44; p<0.0001); and (3) higher success rate of obtaining all nine cardiac views for a given STIC volume (86 vs. 14%; p<0.001).

CONCLUSIONS

When performed by non-expert sonologists, intelligent navigation (FINE) had a superior performance compared to manual navigation of the normal fetal heart. Specifically, FINE obtained appropriate fetal cardiac views in 92-100% of cases.

Maternal obesity in pregnancy and children's cardiac function and structure: A systematic review and meta-analysis of evidence from human studies

The prevalence of obesity is increasing worldwide. Experimental animal studies demonstrate that maternal obesity during pregnancy directly affects cardiac structure and function in their offspring, which could contribute to their increased cardiovascular disease (CVD) risk. Currently, a systematic overview of the available evidence regarding maternal obesity and alterations in cardiac structure and function in human offspring is lacking. We systematically searched the electronic databases Embase, MEDLINE and NARCIS from inception to June 29, 2022 including human studies comparing cardiac structure and function from fetal life onwards in offspring of women with and without obesity. The review protocol was registered with PROSPERO International Prospective Register of Systematic Reviews (identifier: CRD42019125071). Risk of bias was assessed using a modified Newcastle-Ottawa scale. Results were expressed using standardized mean differences (SMD). The search yielded 1589 unique publications, of which thirteen articles were included. Compared to offspring of women without obesity, fetuses of women with obesity had lower left ventricular strain, indicative of reduced systolic function, that persisted in infancy (SMD -2.4, 95% confidence interval (CI) -4.4 standard deviation (SD) to -0.4 SD during fetal life and SMD -1.0, 95% CI -1.6 SD to -0.3 SD in infancy). Furthermore, infants born to women with obesity had a thicker interventricular septum (SMD 0.6 SD, 95% CI 0.0 to 1.2 SD) than children born to women without obesity. In conclusion, cardiac structure and function differs between fetuses and children of women with and without obesity. Some of these differences were present in fetal life, persisted in childhood and are consistent with increased CVD risk. Long-term follow-up research is warranted, as studies in offspring of older age are lacking.

The influence of region of interest width in fetal 2D-speckle tracking echocardiography late in pregnancy

Speckle tracking echocardiography is a promising method for assessment of myocardial function in fetal and neonatal hearts, but further studies are necessary to validate and optimize the settings for use in fetal cardiology. Previous studies have shown that the definition of the region of interest (ROI) affects strain values in adults. The aim of this study was to investigate how different widths of ROI influences measurements of four-chamber longitudinal systolic strain in fetuses late in pregnancy. Thirty-one singleton, healthy fetuses born to healthy mothers underwent an echocardiographic examination during gestational week 37. Speckle tracking was performed with two different settings for ROI width; the narrowest and second most narrow, provided both widths were assessed as suitable for the myocardial wall thickness of the fetus. We found an inverse correlation between the ROI width and the strain values. Four-chamber longitudinal strain changed from - 20.7 ± 3.6% to - 18.0 ± 4.4% (p < 0.001) with increasing ROI width. Further, strain decreased from the endocardium to the epicardium with multilayer measurements. Different widths of ROI influenced the strain measurements significantly in the fetal heart, comparable to what has been reported in adults. A standardization of the ROI setting could improve the interpretation, and reduce variability in fetal strain measurements.

Reference Intervals of Fetal Cardiac Volume Between 14 and 40 Weeks of Gestation

OBJECTIVES

To construct the reference intervals for the cardiac volume (CV) of normal fetuses between 14 and 40 weeks of pregnancy.

METHODS

Low risk singleton pregnancies with normal fetuses were prospectively recruited to acquire 4D-cardio-spatiotemporal image correlation volume datasets (VDS). Subsequent off-line analyses of VDS were anonymously performed to calculate CV using the Virtual Organ Computer-aided AnaLysis technique. The reference intervals were established as a function of gestational age (GA), biparietal diameter (BPD), head circumference (HC), and estimated fetal weight (EFW) based on the best-fitted models for both mean and standard deviation (SD).

RESULTS

A total of 668 VDS were successfully calculated for CV. The best-fitted models for the means and SDs are as follow: 1) GA in week = 6.422 + e^{(-100.653 × GA)} (SD = 0.641 - (0.170 × GA) + (0.009 × GA² )). 2) BPD = 0.016 × (BPD)^3.589 (SD = 2.663 - (1.410 × BPD) + (0.224 × BPD² )). 3) HC = 0.00017 × (HC)^3.537 (SD = 2.341 - (0.341 × HC) + (0.015 × HC² )). The CV progressively increased with advancing fetal age (GA) and size (BPD, HC).

CONCLUSIONS

The reference intervals of CV, theoretically best representing cardiac size, in relation to GA, BPD, HC, and EFW were first established and Z-score was readily calculated. These will be helpful in detection of cardiac abnormalities, especially those associated with cardiomegaly.

4D imaging of fetal right ventricle-feasibility study and a review of the literature

Functional analysis of the fetal cardiovascular system is crucial for the assessment of fetal condition. Evaluation of the right ventricle with standard 2D echocardiography is challenging due to its complex geometry and irregular muscle fibers arrangement. Software package TOMTEC 4D RV-Function is an analysis tool which allows assessment of right ventricular function based on volumetric measurements and myocardial deformation. The aim of this study was to determine the feasibility of this method in fetal echocardiography. The retrospective study was conducted in the high-flow Referral Center for Fetal Cardiology. We recorded 4D echocardiographic sequences of 46 fetuses with normal hearts. Following parameters were calculated: end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV) and ejection fraction (EF), right ventricle longitudinal free-wall (RVLS free-wall) and septal strain (RVLS septum). Tei index was calculated as a standard measure or RV function for comparison. 4D assessment was feasible in 38 out of 46 fetuses (83%). RV volumetric parameters-EDV, ESV and SV-increased exponentially with gestational age. Functional parameters-RV Tei index, EF and strains-were independent of gestational age. Mean EF was 45.2% (± 6%), RV free-wall strain was - 21.2% and RV septal strain was - 21.5%. There was a statistically significant correlation between septal and free-wall strains (r = 0.51, p = 0.001) as well as between EF and RV free-wall strain (r = - 0.41, p = 0.011). 4D RV assessment is feasible in most fetuses. Its clinical application should be further investigated in larger prospective studies.

Fetal Interventricular Septum Volume Evaluated by Three-Dimensional Ultrasound Using Spatiotemporal Image Correlation and Virtual Organ Computer-Aided Analysis in Fetuses From Pre-Gestational Diabetes Mellitus Pregnant Women

BACKGROUND

To assess the interventricular septum (IVS) volume of fetuses from pre-gestational diabetes mellitus (DM) pregnant women by 3-dimensional ultrasound using spatiotemporal image correlation (STIC) and virtual organ computer-aided analysis (VOCAL) methods.

METHODS

This was a prospective cross-sectional study of 45 fetuses from pre-gestational DM and 45 fetuses from healthy pregnant women (controls). Only singleton pregnancies between 20 and 34 + 6 weeks of gestation were included. The fetal IVS volumes were obtained off-line using STIC and VOCAL methods. To analyze differences among variables, the Student’s t-test and Mann-Whitney U test were used. The correlation among continuous variables was determine using Spearman’s correlation test (r).

RESULTS

The median of fetal IVS volume was significantly higher in pre-gestational DM than in healthy pregnant women (0.3 cm³ vs. 0.2 cm³, p = 0.032). A strong positive correlation was observed between fetal IVS volume and gestational age at the time of ultrasound examination (r = 0.75, R² = 0.48, p < 0.0001) and between fetal IVS volume and estimated fetal weight (r = 0.63, R² = 0.37, p < 0.0001). No significant correlation was noted between fetal IVS volume and glycated hemoglobin levels (r = −0.16, R² = 0.01, p = 0.540) in the pre-gestational DM pregnant women.

CONCLUSIONS

Significant differences were observed in fetal IVS volumes between pre-gestational and healthy mothers, with higher values in the fetuses of pre-gestational DM pregnant women.

Assessment of the Size and Shape of the 4-Chamber View and the Right and Left Ventricles using Fetal Speckle Tracking in Normal Fetuses at 17-24 Gestational Weeks

INTRODUCTION

The aim of the study was to establish normal reference values obtained by fetal speckle tracking analysis of the fetal heart between 17-24 weeks of gestation among Thai fetuses and compare the nomograms with previous studies.

METHODS

The 4-chamber view of the fetal heart in 79 normal fetuses was analyzed by speckle tracking analysis to determine the best-fit regression model. The 95% reference intervals and Z-score equations of fetal cardiac parameters were computed.

RESULTS

The end-diastolic length, width, area, and circumference of the 4-chamber view (4CV) as well as the ventricular end-diastolic length, 24-segment widths, and area were all increased as a function of gestational age (GA) and 5 fetal biometric parameters. In contrast, the global sphericity index (SI), 24-segment SI, and right ventricle/left ventricle width and area ratios did not change with GA or fetal biometric measurements. There were few differences in Z-score reference ranges of fetal cardiac measurements between the current study and previous studies conducted in different patient populations.

CONCLUSION

Our study provided z-score and corresponding centile calculators, 5th and 95th centile reference tables, and corresponding graphs for evaluating the size and shape of the 4CV and the right and left ventricles using 6 independent variables between 17 and 24 weeks of gestation. These results provide normal reference ranges for future studies of fetuses with pathologies that may alter the size and shape of the 4-chamber view and ventricles.

Cardiac Measurements of Size and Shape in Fetuses With Absent or Reversed End-Diastolic Velocity of the Umbilical Artery and Perinatal Survival and Severe Growth Restriction Before 34 Weeks' Gestation

OBJECTIVES

The purpose of this study was to evaluate the end-diastolic size and shape of the 4-chamber view as well as the right ventricle (RV) and left ventricle (LV) in growth-restricted fetuses before 34 weeks' gestation with absent or reversed end-diastolic velocity of the umbilical artery and compare the results between those with perinatal deaths and those who survived the neonatal period.

METHODS

Forty-nine fetuses with growth restriction and absent or reversed end-diastolic velocity of the umbilical artery were studied. The size, shape, and sphericity index of the 4-chamber view, RV, and LV were assessed. The number and percentage of fetuses with z score values of less than -1.65 and greater than 1.65 were computed.

RESULTS

Of the 49 fetuses, there were 13 perinatal deaths (27%) and 36 (63%) neonatal survivors. Measurements that were unique for neonatal survivors were an increased RV apical transverse width and decreased measurements of the following: LV and RV widths, LV and RV areas, as well as RV sphericity indices.

CONCLUSIONS

Fetuses with a smaller RV and LV size and area and those with a globular-shaped RV were at significantly lower risk for perinatal death.

A 24-segment fractional shortening of the fetal heart using FetalHQ

OBJECTIVES

To evaluate 24-segment fractional shortening (FS) of the fetal heart using FetalHQ by speckle-tracking regarding reproducibility and the change with advancing gestation.

METHODS

Eighty-one pregnant women at 18-21+6 and 28-31+6 weeks of gestation were studied using FetalHQ with the speckle-tracking technique to calculate 24-segment FS of left and right ventricles. Intra- and inter-class correlation coefficients and intra- and inter-observer agreements of measurements for FS were assessed in each segment.

RESULTS

With respect to intra-observer reproducibility, all FS values showed correlations between 0.575 and 0.862 for the left ventricle, with good intra-observer agreements except for left ventricular segments 14-24. Right ventricular FS values showed correlations between 0.334 and 0.685, with good intra-observer agreements. With respect to inter-observer reproducibility, all FS values showed correlations between 0.491 and 0.801 for the left ventricle, with good intra-observer agreements except for left ventricular segments 16-22. Right ventricular FS values showed correlations between 0.375 and 0.575, with good inter-observer agreements. There were significant differences in the mean FS values in the basal segment (segments 1-5) of the left ventricle between 18 and 21+6 and 28-31+6 weeks of gestation (p<0.05), whereas there were significant differences in all mean FS values in the right ventricle between both gestational ages (p<0.05).

CONCLUSIONS

These results suggest that the reproducibility of the 24-segment FS of the fetal heart using FetalHQ is fair. However, there may be significant differences in FS values with advancing gestational age, especially for the right ventricle.

A transition point for the blood flow wall shear stress environment in the human fetal left ventricle during early gestation

Development of the fetal heart is a fascinating process that involves a tremendous amount of growth. Here, we performed image-based flow simulations of 3 human fetal left ventricles (LV), and investigated the hypothetical scenario where the sizes of the hearts are scaled down, leading to reduced Reynolds number, to emulate earlier fetal stages. The shape and motion of the LV were retained over the scaling to isolate and understand the effects of length scaling on its fluid dynamics. We observed an interesting cut-off point in Reynolds number (Re), across which the dependency of LV wall shear stress (WSS) on Re changed. This was in line with classical fluid mechanic theory where skin friction coefficient exhibited first a decreasing trend and then a plateauing trend with increasing Re. Below this cut-off point, viscous effects dominated, stifling the formation of LV diastolic vorticity structures, and WSS was roughly independent of Reynolds number. However, above this cut-off, inertial effects dominated to cause diastolic vortex ring formation and detachment, and to cause WSS to scale linearly with Reynolds number. Results suggested that this transition point is found at approximately 11 weeks of gestation. Since WSS is thought to be a biomechanical stimuli for growth, this may have implications on normal fetal heart growth and malformation diseases like Hypoplastic Left Heart Syndrome.

A non-invasive multimodal foetal ECG-Doppler dataset for antenatal cardiology research

Non-invasive foetal electrocardiography (fECG) continues to be an open topic for research. The development of standard algorithms for the extraction of the fECG from the maternal electrophysiological interference is limited by the lack of publicly available reference datasets that could be used to benchmark different algorithms while providing a ground truth for foetal heart activity when an invasive scalp lead is unavailable. In this work, we present the Non-Invasive Multimodal Foetal ECG-Doppler Dataset for Antenatal Cardiology Research (NInFEA), the first open-access multimodal early-pregnancy dataset in the field that features simultaneous non-invasive electrophysiological recordings and foetal pulsed-wave Doppler (PWD). The dataset is mainly conceived for researchers working on fECG signal processing algorithms. The dataset includes 60 entries from 39 pregnant women, between the 21st and 27th week of gestation. Each dataset entry comprises 27 electrophysiological channels (2048 Hz, 22 bits), a maternal respiration signal, synchronised foetal trans-abdominal PWD and clinical annotations provided by expert clinicians during signal acquisition. MATLAB snippets for data processing are also provided.

Measurement of fetal automated fractional shortening using two-dimensional tracking in multiple centers

PURPOSE

To establish a normal reference range for automated fractional shortening (Auto FS) in normal singleton fetuses measured at multiple centers.

METHODS

This study was conducted from May 2017 to March 2019. It was undertaken on normal singleton fetuses. First, a four-chamber view of the fetal heart was recorded in the B-mode. Then, the region of interest was set on the edge of the ventricular septum and on the edge of the ventricular muscle at a point one-third away from the atrioventricular valve and toward the cardiac apex. Tracking was automatically performed. Values measured in the right ventricle were defined as R-Auto FS, and in the left ventricle as L-Auto FS. Furthermore, combined-Auto FS was defined as the measurement across both ventricles.

RESULTS

A total of 442 normal fetuses were assessed. R-Auto FS decreased significantly with gestational age, and L-Auto FS showed a similar tendency (Spearman's correlation analysis: r_s =  - 0.415 and r_s =  - 0.252, respectively). Combined-Auto FS showed a similar decline as the gestational age increased (r_s =  - 0.451).

CONCLUSION

In this study, we succeeded in defining a reference Auto FS value not only at one institution but also multiple centers. This study suggests that Auto FS can be used clinically and effectively.

Feasibility of Semiautomatic Fetal Intelligent Navigation Echocardiography for Different Fetal Spine Positions: A Matter of "Time"?

OBJECTIVES

We investigated the feasibility of a semiautomatic approach for assessments of the fetal heart (fetal intelligent navigation echocardiography [FINE]) in cases of optimal and unfavorable fetal spine positions.

METHODS

In this study, a total of 1693 spatiotemporal image correlation volumes of first-, second-, and third-trimester fetuses were evaluated by experts using the FINE approach. The data were analyzed regarding proper reconstruction of the diagnostic cardiac planes depending on the fetal spine position.

RESULTS

A total of 1531 volumes were included. The volumes were divided into 4 groups depending on the fetal spine position: 5-7 o'clock, 4 + 8 o'clock, 3 + 9 o'clock, and 2 + 10 o'clock. In total, 93.2% of the diagnostic planes were displayed properly. Between 5 and 7 o'clock, 94.9% of the diagnostic planes were displayed properly. The correct depiction rates in the other groups were 92.4% (4 + 8 o'clock; n = 538; P = 0.0027), 88.3% (3 + 9 o'clock; n = 156; P < .0001), and 87.3% (2 + 10 o'clock; n = 41; P = .0139). In total, the highest dropout rates were found in the sagittal planes: ductal arch, 13.9%; aortic arch, 10.5%; and venae cavae, 12.0%.

CONCLUSIONS

Based on our results, the FINE technique is an effective method, but its feasibility depends on the fetal position. The use of this semiautomatic work flow-based approach supports evaluation of the fetal heart in a standardized manner. Semiautomatic evaluation of the fetal heart might be useful in facilitating the detection of fetal cardiac anomalies.

Biomechanics of Human Fetal Hearts with Critical Aortic Stenosis

Critical aortic stenosis (AS) of the fetal heart causes a drastic change in the cardiac biomechanical environment. Consequently, a substantial proportion of such cases will lead to a single-ventricular birth outcome. However, the biomechanics of the disease is not well understood. To address this, we performed Finite Element (FE) modelling of the healthy fetal left ventricle (LV) based on patient-specific 4D ultrasound imaging, and simulated various disease features observed in clinical fetal AS to understand their biomechanical impact. These features included aortic stenosis, mitral regurgitation (MR) and LV hypertrophy, reduced contractility, and increased myocardial stiffness. AS was found to elevate LV pressures and myocardial stresses, and depending on severity, can drastically decrease stroke volume and myocardial strains. These effects are moderated by MR. AS alone did not lead to MR velocities above 3 m/s unless LV hypertrophy was included, suggesting that hypertrophy may be involved in clinical cases with high MR velocities. LV hypertrophy substantially elevated LV pressure, valve flow velocities and stroke volume, while reducing LV contractility resulted in diminished LV pressure, stroke volume and wall strains. Typical extent of hypertrophy during fetal AS in the clinic, however, led to excessive LV pressure and valve velocity in the FE model, suggesting that reduced contractility is typically associated with hypertrophy. Increased LV passive stiffness, which might represent fibroelastosis, was found to have minimal impact on LV pressures, stroke volume, and wall strain. This suggested that fibroelastosis could be a by-product of the disease progression and does not significantly impede cardiac function. Our study demonstrates that FE modelling is a valuable tool for elucidating the biomechanics of congenital heart disease and can calculate parameters which are difficult to measure, such as intraventricular pressure and myocardial stresses.

Detailed Echocardiographic Measurements of Individual Chamber in a Chinese Cohort of Hypoplastic Left Heart Syndrome and Comparison with Normal Fetuses via Z-score Modeling

Hypoplastic left heart syndrome (HLHS) is a rare, but exceptionally serious, congenital heart defect. We aimed to explore the best-fitted Z-score models for individual chamber dimension and to draw a comparison between fetuses with HLHS and the normal Chinese cohort. We made measurements of 1674 healthy fetuses and 79 fetuses with HLHS, undertaking echocardiography. Normal fetal cardiovascular Z-score formulae were established by curve-fitting with 5 algorithmic functions and weighted regression of absolute residuals. Classic linear models were fitted for left ventricular diameter against gestational age, and log-transformed linear-power models-were statistically better for left ventricular length, diameter of left atrium and ascending aorta. Fetuses with HLHS manifested significantly lower Z-score means (≤3.5) for these 4 parameters and the vast majority (∼90%) lay beyond -2. Overall, cardiovascular Z-score equations were reliably constructed in a larger Chinese cohort, and their application should benefit evaluation and diagnosis of HLHS.

Doppler Ultrasound Technology for Fetal Heart Rate Monitoring: A Review

Fetal well-being is commonly assessed by monitoring the fetal heart rate (fHR). In clinical practice, the de facto standard technology for fHR monitoring is based on the Doppler ultrasound (US). Continuous monitoring of the fHR before and during labor is performed using a US transducer fixed on the maternal abdomen. The continuous fHR monitoring, together with simultaneous monitoring of the uterine activity, is referred to as cardiotocography (CTG). In contrast, for intermittent measurements of the fHR, a handheld Doppler US transducer is typically used. In this article, the technology of Doppler US for continuous fHR monitoring and intermittent fHR measurements is described, with emphasis on fHR monitoring for CTG. Special attention is dedicated to the measurement environment, which includes the clinical setting in which fHR monitoring is commonly performed. In addition, to understand the signal content of acquired Doppler US signals, the anatomy and physiology of the fetal heart and the surrounding maternal abdomen are described. The challenges encountered in these measurements have led to different technological strategies, which are presented and critically discussed, with a focus on the US transducer geometry, Doppler signal processing, and fHR extraction methods.

Semiautomatic Fetal Intelligent Navigation Echocardiography Has the Potential to Aid Cardiac Evaluations Even in Less Experienced Hands

OBJECTIVES

To investigate the interobserver and intraobserver variability and corresponding learning curve in a semiautomatic approach for a standardized assessment of the fetal heart (fetal intelligent navigation echocardiography [FINE]).

METHODS

A total of 30 stored spatiotemporal image correlation volume data sets of second-trimester fetuses were evaluated by 3 physicians with different levels of expertise in fetal echocardiography by using the FINE approach. Data were analyzed regarding the examination time and proper reconstruction of the diagnostic cardiac planes. The completions and numbers of correct depictions of all diagnostic planes were evaluated by a blinded expert (time t0). To determine interobserver and intraobserver variability, the volumes were reassessed after a 4-week training interval (time t1).

RESULTS

All operators were able to perform the investigation on all 30 volumes. At t0, the interobserver variability between the beginner and both the advanced (P = .0013) and expert (P < .0001) examiners was high. Focusing on intraobserver variability at t1, the beginner showed a marked improvement (P = .0087), whereas in advanced and expert hands, no further improvement regarding proper achievement of all diagnostic planes could be noticed (P > .999; P = .8383). The beginner also showed improvement in the mean investigation time (t0, 82.8 seconds; t1, 73.4 seconds; P = .0895); nevertheless, the advanced and expert examiners were faster in completing the examination (t1, advanced, 20.9 seconds; expert, 28.3 seconds; each P < .0001).

CONCLUSIONS

Based on our results, the FINE technique is a reliable and easily learned method. The use of this semiautomatic work flow-based approach supports evaluation of the fetal heart in a standardized and time-saving manner. A semiautomatic evaluation of the fetal heart might be useful in facilitating the detection of fetal cardiac anomalies.

Neonatal outcome of cases with isolated prenatal ventricular disproportion with a dominant right ventricle

OBJECTIVES

Isolated prenatal ventricular disproportion with a dominant right ventricle represents a challenge in decision-making for both physicians and pregnant women. In the current study, we sought to delineate the postnatal outcomes of these cases.

METHODS

This retrospective analysis included consecutive cases of isolated ventricular disproportion identified using complete fetal echocardiography at the Fetal Heart Center of Xinhua Hospital from January 2014 to October 2017. Postnatal cardiac outcome was examined using transthoracic echocardiography within the first 6 months after birth.

RESULTS

A total of 90 fetuses were included in the final analysis. The median gestational age (GA) at diagnosis was 29 weeks (range 24 to 36). At postnatal examination, cardiac malformations were detected in 39 cases (43.3%), including 25 (27.8%) cases of congenital cardiac septal defects, eight (8.9%) of persistent left superior vena cava, four (4.4%) of left-sided obstructive diseases, and one (1.1%) case of coronary fistula. Nineteen cases (21.1%) with fetal cardiac malformations had significant lower GA at diagnosis (P = .01) and greater right to left ventricle ratio (1.38 vs 1.30, P = .02). Neonatal surgical intervention was not required in any of the cases.

CONCLUSIONS

Isolated prenatal ventricular disproportion with a dominant right ventricle comprises minor postnatal cardiac malformations and doesn't require neonatal intervention.

Feasibility of automated fetal fractional shortening measurement with two-dimensional tracking and construction of a reference range for normal fetuses

PURPOSE

To assess the feasibility of an automated fractional shortening (Auto FS) measurement method using two-dimensional tracking and to construct a reference range for normal fetuses.

METHODS

This study was conducted from May 2017 to March 2018. First, cardiac motion in the four-chamber view was recorded in the B-mode. Subsequently, the region of interest was set on the edge of the ventricular septum or ventricular muscle at a point one-third away from the atrioventricular valve toward the cardiac apex. Tracking was automatically performed. Values measured between the ventricular septum and right ventricle were defined as R-Auto FS, whereas those measured between the ventricular septum and left ventricle were defined as L-Auto FS. Those on each ventricular muscle were defined as Combined-Auto FS.

RESULTS

Data were obtained from 131 singleton fetuses. R-Auto FS significantly decreased with an increase in the number of gestational weeks, and L-Auto FS and Combined-Auto FS showed the same tendency (Spearman's correlation analysis: p = - .528, p = - .351, and p = - .636, respectively).

CONCLUSION

We succeeded in defining a reference Auto FS value for normal singleton pregnancies. Auto FS was negatively correlated with gestational age. This novel technique can assess fetal heart contractility.

Z Score Reference Ranges of Fetal Cardiothoracic Diameter Ratio

OBJECTIVE

This study aims to establish the z score reference ranges of cardiothoracic diameter ratio (CTR) of normal fetuses from 14 to 40 weeks' gestation.

METHOD

A cross-sectional study was conducted on low-risk singleton pregnancies with healthy fetuses. The CTR was performed using simple 2-dimensional sonography on the typical fetal 4-chamber view. The reference ranges were constructed according to gestational age (GA), biparietal diameter (BPD), and head circumference (HC) as independent variables based on the best-fit models, both mean and standard deviation (SD).

RESULTS

A total of 683 fetuses were measured for CTR. The best-fit equations for the mean and SD as a function of GA, BPD, and HC are as follows: (1) CTR = 0.365 + 0.004 × GA in weeks (SD = 0.031 + 0.001 × GA); (2) CTR = 0.373 + 0.014 × BPD in cm (SD = 0.034 + 0.004 × BPD); and (3) CTR = 0.373 + 0.004 × HC in cm (SD = 0.032 + 0.001 × HC). The CTR was slightly increased with advanced GA, BPD, and HC.

CONCLUSION

Complete nomograms with z score reference ranges of CTR were established throughout pregnancy. These nomograms may be useful to detect cardiac abnormalities.

Absent Pulmonary Valve Syndrome in a Fetus: A Case Report and Literature Review

INTRODUCTION

The main characteristics of absent pulmonary valve syndrome (APVS) include the absence or hypoplasia of the pulmonary valve, stenosis of the pulmonary valve annulus, and aneurysmal dilatation of the pulmonary trunk and its branches. In the more common type 1, the tetralogy of Fallot-like type, there is a ventricular septal defect, overriding aorta, pulmonary arterial dilatation, and absence of ductus arteriosus, The second type has an intact ventricular septum, less pulmonary artery dilatation, and a patent ductus arteriosus, with or without tricuspid atresia.

CASE REPORT

This APVS had an intact ventricular septum with an absent ductus arteriosus.

CONCLUSION

The APVS with intact ventricular septum with an absent ductus arteriosus may represent a third type of APVS.

Nomograms of Fetal Cardiac Dimensions at 18-41 Weeks of Gestation

OBJECTIVE

There is a need for standardized reference values for cardiac dimensions in prenatal life. The objective of the present study was to construct nomograms for fetal cardiac dimensions using a well-defined echocardiographic methodology in a low-risk population.

METHODS

This is a prospective cohort study including 602 low-risk singleton pregnancies undergoing a standardized fetal echocardiography to accurately assess fetal cardiac, ventricular, and atrial dimensions. Parametric regressions were tested to model each measurement against gestational age from 18 to 41 weeks of gestation.

RESULTS

Nomograms were constructed for fetal cardiac dimensions (transverse and longitudinal diameters and areas) of the whole heart, atria, and ventricles, as well as myocardial wall thicknesses. All dimensions showed a progressive increase with gestational age. The best model for most parameters was a second-degree linear polynomial. Fetal cardiac, ventricular, and atrial diameters and areas were successfully obtained in 98.6% of the fetuses, while myocardial wall thicknesses could be obtained in 96.5% of the population. The results showed excellent interobserver and intraobserver reproducibility (intraclass correlation coefficient, ICC > 0.811 and ICC > 0.957, respectively).

CONCLUSIONS

We provide standardized and comprehensively evaluated reference values for fetal cardiac morphometric parameters across gestation in a low-risk population. These no mograms would enable the early identification of different patterns of fetal cardiac remodeling.

Fetal Intelligent Navigation Echocardiography (FINE) Detects 98% of Congenital Heart Disease

OBJECTIVE

Fetal intelligent navigation echocardiography (FINE) is a novel method that automatically generates and displays 9 standard fetal echocardiographic views in normal hearts by applying intelligent navigation technology to spatiotemporal image correlation (STIC) volume data sets. The main objective was to determine the sensitivity and specificity of FINE in the prenatal detection of congenital heart disease (CHD).

METHODS

A case-control study was conducted in 50 fetuses with a broad spectrum of CHD (cases) and 100 fetuses with normal hearts (controls) in the second and third trimesters. Using 4-dimensional ultrasound with STIC technology, volume data sets were acquired. After all identifying information was removed, the data sets were randomly distributed to a different investigator for analysis using FINE. The sensitivity and specificity for the prenatal detection of CHD, as well as positive and negative likelihood ratios were determined.

RESULTS

The diagnostic performance of FINE for the prenatal detection of CHD was: sensitivity of 98% (49 of 50), specificity of 93% (93 of 100), positive likelihood ratio of 14, and negative likelihood ratio of 0.02. Among cases with confirmed CHD, the diagnosis with use of FINE completely matched the final diagnosis in 74% (37 of 50); minor discrepancies were seen in 12% (6 of 50), and major discrepancies were seen in 14% (7 of 50).

CONCLUSIONS

This is the first time the sensitivity and specificity of the FINE method in fetuses with normal hearts and CHD in the second and third trimesters has been reported. Because FINE identifies a broad spectrum of CHD with 98% sensitivity, this method could be used prenatally to screen for and diagnose CHD.

4D fetal echocardiography-An update

With the introduction of the electronic 4-dimensional and spatial-temporal image Correlation (e-STIC), it is now possible to obtain large volume datasets of the fetal heart that are virtually free of artifact. This allows the examiner to use a number of imaging modalities when recording the volumes that include two-dimensional real time, power and color Doppler, and B-flow images. Once the volumes are obtained, manipulation of the volume dataset allows the examiner to recreate views of the fetal heart that enable examination of cardiac anatomy. The value of this technology is that a volume of the fetal heart can be obtained, irrespective of the position of the fetus in utero, and manipulated to render images for interpretation and diagnosis. This article presents a summary of the various imaging techniques and provides clinical examples of its application used for prenatal diagnosis of congenital heart defects and abnormal cardiac function.

Twenty-four Segment Transverse Ventricular Fractional Shortening: A New Technique to Evaluate Fetal Cardiac Function

OBJECTIVES

Because of various fetal and maternal disease states, this study was conducted to evaluate the fractional shortening of 24 transverse segments distributed from the base to the apex of the ventricular chambers.

METHODS

Two hundred control fetuses were examined between 20 and 40 weeks' gestation. The transverse displacement of the ventricular endocardium during the cardiac cycle was computed by using offline software. From the output of the analysis, 24 end-diastolic and end-systolic segments were measured from the base (segment 1) to the apex (segment 24) of the right and left ventricles, and the fractional shortening was computed: [(end-diastolic length - end-systolic length)/end-diastolic length] × 100. Examples of fetal cardiovascular abnormalities were selected to demonstrate the utility of this technique.

RESULTS

The fractional shortening for each segment was independent of gestational age and fetal biometric measurements. There was no significant difference in fractional shortening for segments 1 to 5 between the right and left ventricles. However, the fractional shortening of the left ventricle was significantly greater (P < .0001) than that of the right ventricle for segments 6 to 24, suggesting that the mid and apical segments of the left ventricle have increased displacement toward the center of the chamber compared to the right ventricle. Fetuses with various cardiac structural abnormalities had abnormal fractional shortening values.

CONCLUSIONS

The fractional shortening of 24 segments of the right and left ventricles provides a comprehensive method to examine the contractility of the ventricular chambers.

Improved ultrasound transducer positioning by fetal heart location estimation during Doppler based heart rate measurements

OBJECTIVE

Doppler ultrasound (US) is the most commonly applied method to measure the fetal heart rate (fHR). When the fetal heart is not properly located within the ultrasonic beam, fHR measurements often fail. As a consequence, clinical staff need to reposition the US transducer on the maternal abdomen, which can be a time consuming and tedious task.

APPROACH

In this article, a method is presented to aid clinicians with the positioning of the US transducer to produce robust fHR measurements. A maximum likelihood estimation (MLE) algorithm is developed, which provides information on fetal heart location using the power of the Doppler signals received in the individual elements of a standard US transducer for fHR recordings. The performance of the algorithm is evaluated with simulations and in vitro experiments performed on a beating-heart setup.

MAIN RESULTS

Both the experiments and the simulations show that the heart location can be accurately determined with an error of less than 7 mm within the measurement volume of the employed US transducer.

SIGNIFICANCE

The results show that the developed algorithm can be used to provide accurate feedback on fetal heart location for improved positioning of the US transducer, which may lead to improved measurements of the fHR.

Prenatal Diagnosis of Dextrocardia with Complex Congenital Heart Disease Using Fetal Intelligent Navigation Echocardiography (FINE) and a Literature Review

Fetal dextrocardia is a type of cardiac malposition where the major axis from base to apex points to the right side. This condition is usually associated with a wide spectrum of complex cardiac defects. As a result, dextrocardia is conceptually difficult to understand and diagnose on prenatal ultrasound. The advantage of four-dimensional sonography with spatiotemporal image correlation (STIC) is that this modality can facilitate fetal cardiac examination. A novel method known as fetal intelligent navigation echocardiography (FINE) allows automatic generation of nine standard fetal echocardiography views in normal hearts by applying intelligent navigation technology to STIC volume datasets. In fetuses with congenital heart disease, FINE is also able to demonstrate abnormal cardiac anatomy and relationships when there is normal cardiac axis and position. However, this technology has never been applied to cases of cardiac malposition. We report herein for the first time, a case of fetal dextrocardia and situs solitus with complex congenital heart disease in which the FINE method was invaluable in diagnosing multiple abnormalities and defining complex anatomic relationships. We also review the literature on prenatal sonographic diagnosis of dextrocardia (with an emphasis on situs solitus), as well as tricuspid atresia with its associated cardiac features.

Ultrasound transducer positioning aid for fetal heart rate monitoring

Fetal heart rate (fHR) monitoring is usually performed by Doppler ultrasound (US) techniques. For reliable fHR measurements it is required that the fetal heart is located within the US beam. In clinical practice, clinicians palpate the maternal abdomen to identify the fetal presentation and then the US transducer is fixated on the maternal abdomen where the best fHR signal can be obtained. Finding the optimal transducer position is done by listening to the strength of the Doppler audio output and relying on a signal quality indicator of the cardiotocographic (CTG) measurement system. Due to displacement of the US transducer or displacement of the fetal heart out of the US beam, the fHR signal may be lost. Therefore, it is often necessary that the obstetrician repeats the tedious procedure of US transducer positioning to avoid long periods of fHR signal loss. An intuitive US transducer positioning aid would be highly desirable to increase the work flow for the clinical staff. In this paper, the possibility to determine the fetal heart location with respect to the transducer by exploiting the received signal power in the transducer elements is shown. A commercially available US transducer used for fHR monitoring is connected to an US open platform, which allows individual driving of the elements and raw US data acquisition. Based on the power of the received Doppler signals in the transducer elements, the fetal heart location can be estimated. A beating fetal heart setup was designed and realized for validation. The experimental results show the feasibility of estimating the fetal heart location with the proposed method. This can be used to support clinicians in finding the optimal transducer position for fHR monitoring more easily.

Fetal echocardiography: reference values for the Chinese population

OBJECTIVE

Global racial variability in human development can lead to differences in size of fetal cardiac structures during gestation. Our objective is to establish normal reference ranges of fetal cardiac dimensions between 20 and 34 weeks from fetal echocardiograms recorded at a single center in China.

METHODS

A prospective cross-sectional study was undertaken on single pregnancies with normal fetuses of varying gestational ages (GAs). A total of 4396 normal fetuses were divided into 15 groups from 20 to 34 weeks according to the GA. Measurements included the inner diameter of the fetal cardiac chambers and arteries, the aortic arch isthmus (AI), the descending aorta (DAO), the ductus arteriosus (DA), and the foramen ovale (FO). Measurements were statistically analyzed and regression analysis was applied to assess for correlation with GA.

RESULTS

Normal reference values of fetal cardiovascular dimensions between 20 and 34 weeks were obtained from 4396 subjects at a single center in China. Measurements of fetal cardiac structures increase with advancing GA. It seems there is no difference in r values among linear, cubic, and quadratic model analyses (P > 0.05). However, the r values for the exponential models appear to be smaller than those of the other three models (P < 0.05). Ratios of the diameters of fetal cardiac structures were calculated in order to identify for differential changes in the growth of structures.

CONCLUSIONS

The presented data derived from 4396 normal fetuses provide the reference values of fetal echocardiography in China, which provide guidance to fetal echocardiography examinations.

Reference Ranges of Fetal Cardiac Biometric Parameters Using Three-Dimensional Ultrasound with Spatiotemporal Image Correlation M Mode and Their Applicability in Congenital Heart Diseases

To determine reference values for fetal heart biometric parameters using the spatiotemporal image correlation (STIC) M mode and their applicability in congenital heart diseases (CHDs). A cross-sectional prospective study was conducted with 300 singleton pregnancies between 20 and 33 + 6 weeks of gestation. Right ventricular wall thickness (RVWT), interventricular septum thickness (IVST), and left ventricular wall thickness (LVWT) were measured off-line using the STIC-M mode with the cursor perpendicular to the interventricular septum. Polynomial regressions adjusted with the coefficient of determination (R ²) were performed. The curves were applied to 14 fetuses with structural CHD. For the reproducibility calculations, the concordance correlation coefficient (CCC) was used. The mean RVWT, IVST, and LVWT were 0.34 ± 0.09 cm, 0.28 ± 0.09 cm, and 0.30 ± 0.07 cm, respectively. There was correlation between RVWT, IVST, and LVWT and gestational age (GA): RVWT = -0.002 + 0.013 × GA (R ² = 0.33), IVST = -0.011 + 0.011 × GA (R ² = 0.25), and LVWT = 0.056 + 0.009 × GA (R ² = 0.26). RVWT, IVST, and LVWT were altered (<5th or >95th percentile) in 5/14, 5/14, and 7/14 of the fetuses with CHD, respectively. For RVWT, IVST, and LVWT, intra-observer (CCC = 0.86, 0.85, and 0.87, respectively) and inter-observer (CCC = 0.86, 0.86, and 0.86, respectively) reproducibility were good/moderate. The reference ranges determined for fetal heart biometric parameters using STIC-M had good intra- and inter-observer reproducibility and were applicable to fetuses with CHD.

Fetal Heart Size: A Comparison Between the Point-to-Point Trace and Automated Ellipse Methods Between 20 and 40 Weeks' Gestation

OBJECTIVES

To evaluate whether the global area and circumference of the heart varies between two measurement techniques: the point-to-point trace and the electronic ellipse methods.

METHODS

The epicardial border of the 4-chamber view was measured in 200 fetuses between 20 and 40 weeks' gestation, from which the area and circumference using the point-to-point trace and electronic ellipse were measured. Analysis of variance, correlation, and regression analysis using fractional polynomials and 7 independent variables (head circumference, biparietal diameter, abdominal circumference, femur length, estimated fetal weight, mean ultrasound gestational age, and last menstrual period gestational age) were performed.

RESULTS

The correlation between the mean ultrasound gestational age and last menstrual period gestational age was 0.9880 (5% confidence limit, 0.9716; 95% confidence limit, 0.9880), with an R² of 0.9762. The R² value for the 7 independent variables regressed against the area and circumference using the point-to-point trace and electronic ellipse methods ranged between 0.885 and 0.965. Comparison of Z scores between this study and previous publications demonstrated that there were differences and similarities, depending on whether the area or circumference was measured.

CONCLUSIONS

This study shows high R² values when comparing measurements of the area and circumference against 7 independent variables, irrespective of whether the point-to-point trace or the electronic ellipse method was used to obtain the measurements. A calculator to evaluate the area and circumference is provided, using 7 independent variables from which Z scores and percentiles for individual measurements can be computed.

Quantitative Cardiac Assessment in Fetal Tetralogy of Fallot

OBJECTIVES

The purpose of this study was to quantitatively assess cardiac function and biometric parameters in fetuses with a diagnosis of tetralogy of Fallot and compare them to those in healthy fetuses.

METHODS

Two hundred healthy fetuses and 20 fetuses with a diagnosis of classic tetralogy of Fallot were quantitatively assessed for 16 cardiac parameters, including morphologic characteristics and functions. All recruited fetuses were in the second trimester with correct gestational ages. The measured values that were out of normal reference ranges were considered abnormal. Rates of abnormalities of these parameters were compared between the groups. The significant parameters were further analyzed for their sensitivity, specificity, and likelihood ratio.

RESULTS

Of the 16 parameters, rates of abnormalities in 7 parameters, including right ventricular wall thickness, peak systolic velocities (PSVs) in the pulmonary artery and aorta, time to peak velocity, or acceleration time, in the pulmonary artery, aortic valve diameter, pulmonary valve diameter, and aortic-to-pulmonary valve diameter ratio, were significantly higher in fetuses with tetralogy of Fallot (P < .001). The pulmonary artery PSV, pulmonary artery time to peak velocity, aortic valve diameter, pulmonary valve diameter, and aortic-to-pulmonary valve diameter ratio had high sensitivities (80.0%, 75.0%, 90.0%, 90.0%, and 100.0%, respectively) and specificities (95.5%, 97.0%, 94.5%, 96.0%, and 84.5%).

CONCLUSIONS

In addition to a routine anatomic examination, quantitative assessment of fetal hemodynamics, especially an abnormally high PSV in the pulmonary artery, as well as a shortened acceleration time and abnormal valve size, might be very helpful for confirmation of the diagnosis in cases of suspected tetralogy of Fallot.

A Prospective Study of the Use of Fetal Intelligent Navigation Echocardiography (FINE) to Obtain Standard Fetal Echocardiography Views

OBJECTIVE

To evaluate the performance of Fetal Intelligent Navigation Echocardiography (FINE) applied to spatiotemporal image correlation (STIC) volume datasets of the normal fetal heart in generating standard fetal echocardiography views.

METHODS

In this prospective cohort study of patients with normal fetal hearts (19-30 gestational weeks), one or more STIC volume datasets were obtained of the apical four-chamber view. Each STIC volume successfully obtained was evaluated by STICLoop™ to determine its appropriateness before applying the FINE method. Visualization rates for standard fetal echocardiography views using diagnostic planes and/or Virtual Intelligent Sonographer Assistance (VIS-Assistance®) were calculated.

RESULTS

One or more STIC volumes (total n = 463) were obtained from 246 patients. A single STIC volume per patient was analyzed using the FINE method. In normal cases, FINE was able to generate nine fetal echocardiography views using: (1) diagnostic planes in 76-100% of the cases, (2) VIS-Assistance® in 96-100% of the cases, and (3) a combination of diagnostic planes and/or VIS-Assistance® in 96-100% of the cases.

CONCLUSION

FINE applied to STIC volumes can successfully generate nine standard fetal echocardiography views in 96-100% of cases in the 2nd and 3rd trimesters. This suggests that the technology can be used as a method of screening for congenital heart disease.

How to Acquire Cardiac Volumes for Sonographic Examination of the Fetal Heart: Part 2

The effective performance of fetal cardiac examination using spatiotemporal image correlation (STIC) technology requires 2 essential steps: volume acquisition and postprocessing. An important prerequisite is training sonologists to acquire high-quality volume data sets so that when analyzed, such volumes are informative. This article is part 2 of a series on 4-dimensional sonography with STIC. Part 1 focused on STIC technology and its features, the importance of operator training/experience and acquisition of high-quality STIC volumes, factors that affect STIC volume acquisition rates, and general recommendations on performing 4D sonography with STIC. In part 2, we discuss a detailed and practical stepwise approach for STIC volume acquisition, along with methods to determine whether such volumes are appropriate for analysis.

How to Acquire Cardiac Volumes for Sonographic Examination of the Fetal Heart: Part 1

Four-dimensional sonography with spatiotemporal image correlation (STIC) technology allows acquisition of a fetal cardiac volume data set and displays a cine loop of a complete single cardiac cycle in motion. Part 1 of this 2-part article reviews STIC technology and its features, the importance of operator training/experience, and acquisition of high-quality STIC volumes, as well as factors that affect STIC volume acquisition rates. We also propose a detailed and practical stepwise approach to performing 4-dimensional sonography with STIC and begin herein by providing general recommendations. Part 2 will discuss specifics of the approach, along with how to determine whether such volumes are appropriate for analysis.

Prospective evaluation of the fetal heart using Fetal Intelligent Navigation Echocardiography (FINE)

OBJECTIVE

To evaluate prospectively the performance of Fetal Intelligent Navigation Echocardiography (FINE) applied to spatiotemporal image correlation (STIC) volume datasets of the normal fetal heart.

METHODS

In all women between 19 and 30 weeks' gestation with a normal fetal heart, an attempt was made to acquire STIC volume datasets of the apical four-chamber view if the following criteria were met: (1) fetal spine located between 5- and 7-o'clock positions; (2) minimal or absent shadowing (including a clearly visible transverse aortic arch); (3) absence of fetal breathing, hiccups, or movement; and (4) adequate image quality. Each STIC volume successfully acquired was evaluated by STICLoop™ to determine its appropriateness before applying the FINE method. Visualization rates of fetal echocardiography views using diagnostic planes and/or Virtual Intelligent Sonographer Assistance (VIS-Assistance®) were calculated.

RESULTS

One or more STIC volumes (365 in total) were obtained successfully in 72.5% (150/207) of women undergoing ultrasound examination. Of the 365 volumes evaluated by STICLoop, 351 (96.2%) were considered to be appropriate. From the 351 STIC volumes, only one STIC volume per patient (n = 150) was analyzed using the FINE method, and consequently nine fetal echocardiography views were generated in 76-100% of cases using diagnostic planes only, in 98-100% of cases using VIS-Assistance only, and in 98-100% of cases when using a combination of diagnostic planes and/or VIS-Assistance.

CONCLUSIONS

In women between 19 and 30 weeks' gestation with a normal fetal heart undergoing prospective sonographic examination, STIC volumes can be obtained successfully in 72.5% of cases. The FINE method can be applied to generate nine standard fetal echocardiography views in 98-100% of these cases using a combination of diagnostic planes and/or VIS-Assistance. This suggests that FINE could be implemented in fetal cardiac screening programs. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

Canine fetal echocardiography: correlations for the analysis of cardiac dimensions

The aim of this study was to develop regression models for correlation of canine fetal heart development with body size to characterize normal development or suggest cardiac anomalies. Twenty clinically healthy pregnant bitches, either brachycephalic and non-brachycephalic, were examined ultrasonographically. Transabdominal fetal echocardiography was conducted every 4 days from the beginning of cardiac chambers differentiation until parturition. Ten cardiac parameters were measured: length, width and diameter of the heart; heart area; left and right ventricular dimensions; left and right atrial dimensions; and aortic and pulmonary artery diameter. Femoral length, biparietal diameter and abdominal cross-sectional area were also recorded. Regression equations were developed for each parameter of fetal body size, and linear and logarithmic models were compared. The model with the highest correlation coefficient was chosen to produce equations to calculate relative dimensions based on the correlations. Only the left-ventricular chamber differed between the two racial groups. Biparietal diameter was the independent parameter that produced the highest correlation coefficient for the most fetal cardiac dimensions, although good correlations were also observed using femoral length and abdominal cross-sectional area. Heart width and heart diameter were used as surrogates of cardiac development, as these measurements showed the best statistical correlation. Quantitative evaluation of fetal cardiac structures can be used to monitor normal and abnormal cardiac development.

Hemodynamic studies of isolated absent ductus venosus

OBJECTIVE

The objective of this article is to evaluate hemodynamic changes among fetuses with isolated absent ductus venosus (IADV) diagnosed by prenatal ultrasonography.

PATIENTS AND METHODS

Fetuses with prenatal diagnosis of IADV were recruited and followed. Hemodynamic assessment was performed in all cases, including measurement of cardiac dimensions, shortening fraction, myocardial performance index, preload index in the inferior vena cava and the presence of venous pulsations in the umbilical vein (UV).

RESULTS

Nine fetuses of IADV were assessed, including six cases with extra-hepatic UV drainage and three with intra-hepatic drainage. All fetuses with extra-hepatic UV drainage showed an elevated preload index in the inferior vena cava, venous pulsations in the UV and cardiomegaly. Of them, four had hydrops, two showed poor cardiac function and three resulted in perinatal mortality. Three cases with intra-hepatic drainage had continuous flow in the UV, normal in all hemodynamic parameters and all survived.

CONCLUSION

Hemodynamic assessment of fetuses with IADV was helpful in predicting the development of hydrops and perinatal mortality. The poor prognostic factors included cardiac overload, cardiomegaly, poor myocardial performance, increased preload, the presence of venous pulsations and extra-hepatic UV drainage. © 2015 John Wiley & Sons, Ltd.