Fetal cardiac ventricle volumetry in the second half of gestation assessed by 4D ultrasound using STIC combined with inversion mode

Comparison of Different Ultrasonic Screening Methods and Analysis of High Risk Factors for Fetal Cardiac Malformation in Second Trimester of Pregnancy

Current study aims to compare the application of two-dimensional (2D) color doppler ultrasound (CDU) and four-dimensional (4D) ultrasound spatiotemporal image correlation (STIC) in fetal congenital heart disease in the second trimester of pregnancy and to analyze the high risk factors of the disease. From August 2019 to July 2021, 135 second-trimester patients with highly suspected congenital heart malformations were selected who underwent prenatal screening at South Taihu Hospital Affiliated to Huzhou University. 2D-CDU, 4D STIC, and postnatal examination were completed in all patients. 2D-CDU, 4D STIC and 2D-CDU combined with 4D STIC were used to detect fetal cardiac malformations and classify cardiac malformations. The sensitivity, specificity, positive predictive value, negative predictive value and coincidence rate of 2D-CDU, 4D STIC and 2D-CDU combined with 4D STIC were compared. The results of 2D-CDU, 4D STIC and 2D-CDU combined with 4D STIC screening were analyzed for consistency using the results of postpartum diagnosis as the gold standard. Moreover, effects of maternal gestational factors on fetal cardiac malformations by univariate and multivariate analysis. 2D-CDU combined with 4D STIC showed significantly higher section display number than 2D-CDU or 4D STIC in the view of ductal arch, aortic arch, and aortic short-axis. A total of 45 cases of fetal congenital heart malformation were detected in 135 patients in the second trimester, 40, 38 or 42 cases were detected by 2D-CDU, 4D STIC or 2D-CDU combined with 4D STIC, respectively. The sensitivity, specificity, positive predictive value, negative predictive value and coincidence rate of 2D-CDU combined with 4D ultrasound in congenital heart malformation screening were higher than those of 2D-CDU or 4D STIC. Kappa agreement analysis showed that the diagnostic results of 4D STIC and 2D-CDU combined with 4D ultrasound in fetuses with suspected congenital heart malformation were in excellent agreement (κ > 0.75), while 2D-CDU was in good agreement with postpartum diagnosis (κ < 0.75). Univariate and multivariate regression analysis revealed that maternal age ≥ 35, drinking during pregnancy, and history of adverse pregnancy and childbirth were all independent risk factors for fetal cardiac malformations, while folic acid supplementation was an independent protective factor for fetal cardiac malformations. 2D-CDU combined with 4D echocardiography may be superior to single 2D-CDU or 4D STIC in the screening of fetal congenital heart malformation in the second trimester. In order to reduce the incidence of fetal heart anomalies, we should strengthen the screening of pregnancy anomalies in high-risk pregnant women and control the risk factors.

Three-Dimensional Ultrasound for Physical and Virtual Fetal Heart Models: Current Status and Future Perspectives

Congenital heart defects (CHDs) are the most common congenital defect, occurring in approximately 1 in 100 live births and being a leading cause of perinatal morbidity and mortality. Of note, approximately 25% of these defects are classified as critical, requiring immediate postnatal care by pediatric cardiology and neonatal cardiac surgery teams. Consequently, early and accurate diagnosis of CHD is key to proper prenatal and postnatal monitoring in a tertiary care setting. In this scenario, fetal echocardiography is considered the gold standard imaging ultrasound method for the diagnosis of CHD. However, the availability of this examination in clinical practice remains limited due to the need for a qualified specialist in pediatric cardiology. Moreover, in light of the relatively low prevalence of CHD among at-risk populations (approximately 10%), ultrasound cardiac screening for potential cardiac anomalies during routine second-trimester obstetric ultrasound scans represents a pivotal aspect of diagnosing CHD. In order to maximize the accuracy of CHD diagnoses, the views of the ventricular outflow tract and the superior mediastinum were added to the four-chamber view of the fetal heart for routine ultrasound screening according to international guidelines. In this context, four-dimensional spatio-temporal image correlation software (STIC) was developed in the early 2000s. Some of the advantages of STIC in fetal cardiac evaluation include the enrichment of anatomical details of fetal cardiac images in the absence of the pregnant woman and the ability to send volumes for analysis by an expert in fetal cardiology by an internet link. Sequentially, new technologies have been developed, such as fetal intelligent navigation echocardiography (FINE), also known as "5D heart", in which the nine fetal cardiac views recommended during a fetal echocardiogram are automatically generated from the acquisition of a cardiac volume. Furthermore, artificial intelligence (AI) has recently emerged as a promising technological innovation, offering the potential to warn of possible cardiac anomalies and thus increase the ability of non-cardiology specialists to diagnose CHD. In the early 2010s, the advent of 3D reconstruction software combined with high-definition printers enabled the virtual and 3D physical reconstruction of the fetal heart. The 3D physical models may improve parental counseling of fetal CHD, maternal-fetal interaction in cases of blind pregnant women, and interactive discussions among multidisciplinary health teams. In addition, the 3D physical and virtual models can be an useful tool for teaching cardiovascular anatomy and to optimize surgical planning, enabling simulation rooms for surgical procedures. Therefore, in this review, the authors discuss advanced image technologies that may optimize prenatal diagnoses of CHDs.

Relative Mediastinal Displacement Index (RMDI): A Prenatal MRI Indicator of Adverse Events in Fetuses With Isolated Left Congenital Diaphragmatic Hernia

BACKGROUND

Extracorporeal membrane oxygenation (ECMO), has partly improved congenital diaphragmatic hernia (CDH) outcomes, yet the overall morbidity and mortality remain high. Existing prenatal indicators for CDH fetuses are operator-dependent, time-consuming, or less accurate, a new simple and accurate indicator to indicate adverse events in CDH patients is needed.

PURPOSE

To propose and assess the association of a new MRI parameter, the relative mediastinal displacement index (RMDI), with adverse events including in-hospital deaths or the need for ECMO in fetuses with isolated left CDH (iLCDH).

STUDY TYPE

Retrospective analysis.

SUBJECTS

One hundred thirty-nine fetuses were included in the iLCDH group (24 with adverse events and 115 without) and 257 fetuses were included in the control group from two centers in Guangzhou.

FIELD STRENGTH/SEQUENCE

3.0 T, T2WI-TRUFI; 1.5 T, T2WI-FIESTA.

ASSESSMENT

Three operators independently measured the→ DL ,→ DR , and DH on the axial images. The calculation formula of the RMDI was (→ DL  + → DR )/DH.

STATISTICAL TESTS

The independent sample t test, Mann-Whitney U test, Chi-square test, Chi-square test continuity correction, Fisher's test, linear regression analysis, logistic regression analysis, intraclass correlation coefficient, receiver operating characteristic curve analysis, and Delong test. A P value <0.05 was considered statistically significant.

RESULTS

The RMDI did not change with gestational age in the iLCDH group (with [P = 0.189] and without [P = 0.567] adverse events) and the control group (P = 0.876). There were significant differences in RMDI between the iLCDH group (0.89 [0.65, 1.00]) and the control group (-0.23 [-0.34, -0.16]). In the iLCDH group, RMDI was the only indicator left for indicating adverse events, and the best cutoff value was 1.105. Moreover, there was a significant difference in diagnostic accuracy between the RMDI (AUC = 0.900) and MSA (AUC = 0.820), LHR (AUC = 0.753), o/e LHR (AUC = 0.709), and o/e TFLV (AUC = 0.728), respectively.

DATA CONCLUSION

The RMDI is expected to be a simple and accurate tool for indicating adverse events in fetuses with iLCDH.

EVIDENCE LEVEL

4 TECHNICAL EFFICACY: Stage 1.

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).

Longitudinal Surveillance of Fetal Heart Failure Using Speckle Tracking Analysis

Long-term monitoring of a fetus with heart failure is an undeniable challenge for prenatal cardiology. Echocardiography is constrained by many fetal and maternal factors, and it is difficult to maintain the reproducibility of the measured and analyzed parameters. In our study, we presented the possibilities of using modern speckle tracking technology in combination with standard echocardiography parameters that may be insufficient or less sensitive in the context of monitoring life-threatening fetal conditions. Our analysis shows the superiority of the parameters used to assess fetal cardiac architecture, such as the GSI Global sphericity Index, and fetal cardiac function, such as the FAC fractional area change and the EF ejection fraction, which temporal change may indicate a worsening condition of the fetus with heart failure. The significant increase in the parameters of fetal heart size in speckle tracking allows for an improved echocardiographic diagnosis and monitoring of the fetus with heart failure and the prognostic conclusions about the clinical condition after birth. Significant decreases in FAC for the left and right ventricles and EF for the left ventricle may indicate an unfavourable prognosis for the monitored fetus due to heart failure.

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

AIM

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

METHODS

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

RESULTS

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

CONCLUSION

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

New and advanced features of fetal intelligent navigation echocardiography (FINE) or 5D heart

Congenital heart disease (CHD) is the leading organ-specific birth defect, as well as the leading cause of infant morbidity and mortality from congenital malformations. Therefore, a comprehensive screening examination of the fetal heart should be performed in all women to maximize the detection of CHD. Four-dimensional sonography with spatiotemporal image correlation (STIC) technology displays a cine loop of a complete single cardiac cycle in motion. A novel method known as Fetal Intelligent Navigation Echocardiography (or FINE) was previously developed to interrogate STIC volume datasets using "intelligent navigation" technology. Such method allows the automatic display of nine standard fetal echocardiography views required to diagnose most cardiac defects. FINE considerably simplifies fetal cardiac examinations and reduces operator dependency. It has both high sensitivity and specificity for the detection of CHD. Indeed, FINE has been integrated into several commercially available ultrasound platforms.Recently, eight novel and advanced features have been developed for the FINE method and they will be described herein. Such features can be categorized based upon their broad goals. The first goal is to simplify FINE further, and consists of the following features: (1) Auto fetal positioning (or FINE align); (2) Skip points; (3) Predictive cursor; (4) Static mode volume; and (5) Breech sweep. The second goal is to allow quantitative measurements to be performed on the cardiac views generated by FINE: (6) Automatic cardiac axis; and (7) Cardiac biometry. Finally, the last goal is to improve the success of obtaining fetal echocardiography view(s); and consists of (8) Maestro planar navigation.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

IMPACT

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

Fetal Cardiac Function and Ventricular Volumes Determined by Three-Dimensional Ultrasound Using STIC and VOCAL Methods in Fetuses from Pre-gestational Diabetic Women

To assess the fetal cardiac function and ventricular volumes by three-dimensional (3D) ultrasound using spatio-temporal image correlation (STIC) and virtual organ computer-aided analysis (VOCAL) methods in fetuses from pre-gestational diabetic women. This was a prospective and cross-sectional study that evaluated 53 fetuses from pre-gestational diabetic women and 53 fetuses from healthy mothers between 20 and 34 weeks of gestation. Only fetuses with no structural or genetic abnormalities and singleton pregnant women were included in this study. The fetal cardiac volumes were assessed by STIC and VOCAL methods. The ejection fraction, stroke volume, and cardiac output were calculated from these measurements to evaluate fetal cardiac function. The Mann-Whitney U test was performed to compare the two groups. For calculation of intra- and interobserver reproducibility's, we used concordance correlation coefficients. The mean differences in the right atrial volumes between the diabetic and normal groups ranged from 0.05 mL to 0.1 mL (p = 0.917 and 0.355, respectively). The median of left atrium (LA) volume measurement in pre-gestational diabetic group was significantly lower than healthy mothers (LA: 0.62 vs. 0.68 mL; p < 0.001). The fetal right and left ventricular volumes were similar in both groups. No significant differences in ejection fraction, stroke volume and cardiac output were observed (p value range 0.086-0.815). The majority of fetal atrial/ventricular volumes showed good intra- and interobserver reliabilities. Conversely, the majority cardiac function parameters showed poor intra- and interobserver agreements. STIC and VOCAL methods gave reproducible quantitative results for fetal atrial and ventricular volumes. Significant differences in fetal left atrial volumes were observed between the two groups, which be related to LA atrial dysfunction and /or left ventricle (LV) compliance, reflecting earlier stages of cardiac dysfunction.

Z Score Reference Ranges of Fetal Cardiac Output From 12 to 40 Weeks of Pregnancy

OBJECTIVES

To develop the Z score reference ranges of fetal cardiac output (CO) in healthy fetuses from 12 to 40 weeks of pregnancy.

METHODS

A cross-sectional descriptive study was undertaken among low-risk singleton pregnancies with healthy fetuses between 12 and 40 weeks. The right ventricular cardiac output (RCO), left ventricular cardiac output (LCO), and combined cardiac output (CCO) were measured by 2-dimensional ultrasound with the Doppler velocity of the aorta and pulmonary arteries. The pregnancies were followed until delivery RESULTS: The RCO, LCO, and CCO were determined in 700 fetuses. The predictive models of the CO as a function of gestational age (GA) and biparietal diameter were identified, and the Z score reference ranges were constructed. The means and standard deviations of CO on both sides were increased with GA and biparietal diameter as power models. Nomograms for the LCO, RCO, and CCO were established (ie, RCO = 0.000148 × GA^4.283034 ; SD = 0.000131 × GA^4.026209 ; LCO = 0.000514 × GA^3.790944 ; SD = 0.000169 × GA^3.815546 ). The RCO was much more increased than the LCO with advancing GA.

CONCLUSIONS

The Z score reference ranges and percentile charts of fetal CO were constructed throughout gestation with a large sample size. This may be helpful in detection of cardiac disorders, especially cardiomyopathy, cardiac anomalies, fetal anemia, and fetal growth restriction.

Fetal cardiac function by three-dimensional ultrasound using 4D-STIC and VOCAL - an update

Three- and four-dimensional (3D/4D) ultrasonography with spatio-temporal image correlation (4D-STIC) allows obtaining fetal cardiac volumes and their static and real-time analysis in multiplanar and rendering modes. Cardiac biometrics and Doppler-echocardiographic parameters for evaluation of fetal heart function, including cardiac output and stroke volume, can be analyzed using M-mode, two-dimensional (2D), and 3D/4D cardiac ultrasound. In recent years, functional echocardiography has been used to study fetuses without a structurally cardiac defect but who are at risk of heart failure due to the presence of extra-cardiac conditions, such as, fetal growth restriction, tumors/masses, twin-to-twin transfusion syndrome, fetal anemia (Rh alloimmunization), congenital infections, or maternal diabetes mellitus. The assessment of cardiac function provides important information on hemodynamic status and can help optimize the best time for delivery and reduce perinatal morbidity and mortality. Since 2003, with the advent of the 4D-STIC software, it is possible to evaluate the fetal heart in multiplanar, and rendering modes. This technology associated with virtual organ computer-aided analysis (VOCAL) enables determining the ventricular volume (end-diastole, end-systole), the stroke-volume, the ejection fraction, and the cardiac output of each ventricle. Since 2004, several studies demonstrated that the 4D-STIC and VOCAL had good reproducibility to measure cardiac volumes This study reviews published studies that evaluated the fetal cardiac function by 3D ultrasound using 4D-STIC and VOCAL software.

Diagnostic value of echocardiography in fetal cardiac malformation and clinical classification

Diagnostic value of echocardiography in fetal cardiac malformation and clinical classification was investigated. In total, 206 high-risk parturients, who received a screening of prenatal fetal cardiac malformation in Jinan Maternity and Child Care Hospital from January 2015 to June 2017, were retrospectively analyzed, among those parturients, the results of labor induction or newborns of 141 parturients were diagnosed as cardiac malformation, the fetuses of 65 parturients were diagnosed as non-cardiac malformation, the detection of fetal cardiac malformation of all the parturients was carried out by two-dimensional ultrasound and four-dimensional ultrasound during gestation period, presence or absence of congenital cardiac malformation of the fetuses and clinical classification were estimated. The sensitivity of two-dimensional ultrasound diagnosis combined with four-dimensional ultrasound diagnosis was significantly higher than that of two-dimensional ultrasound diagnosis and four-dimensional ultrasound diagnosis (P<0.05). In addition, the sensitivity of four-dimensional ultrasound diagnosis was significantly higher than that of two-dimensional ultrasound diagnosis (P<0.05). The specificity and positive predictive value of four-dimensional ultrasound diagnosis were significantly higher than those of two-dimensional ultrasound diagnosis and two-dimensional ultrasound diagnosis combined with four-dimensional ultrasound diagnosis (P<0.05). The diagnostic coincidence rates of four-dimensional ultrasound diagnosis and two-dimensional ultrasound diagnosis combined with four-dimensional ultrasound diagnosis were significantly higher than that of two-dimensional ultrasound diagnosis (P<0.05). The negative predictive values of the combined ultrasound diagnosis and four-dimensional ultrasound diagnosis were significantly higher than that of two-dimensional ultrasound diagnosis (P<0.05). The diagnostic efficiency of two-dimensional ultrasound combined with four-dimensional ultrasound was good in the diagnosis of fetal cardiac malformation in prenatal period of pregnant women, it could improve detection rate of fetal cardiac malformation and is worthy of being generalized in clinic.

Four-Dimensional Ultrasound for Evaluating Newborn Cardiac Output: A Pilot Study of Healthy Infants

BACKGROUND

There is currently no reliable non-invasive method of measuring cardiac output in neonatal intensive care. Spatiotemporal image correlation (STIC) is a novel four-dimensional (4D) ultrasound technique that was developed to assess the foetal heart, and it may be a useful way to assess neonatal haemodynamics.

OBJECTIVE

This study aimed to evaluate the feasibility and reproducibility of determining neonatal cardiac output using STIC ultrasound in newborn infants.

DESIGN

Infants were recruited opportunistically from a neonatal intensive care unit and then examined by 2 independent observers. STIC was used to obtain images of the heart. End-diastolic and end-systolic ventricular volumes were measured using virtual organ computer-aided analysis (VOCAL) and used to calculate cardiac output. Reproducibility was assessed with intraclass correlation coefficients (ICC) and agreement with Bland-Altman analysis.

RESULTS

Twenty-four clinically stable infants of 34-43 weeks corrected gestational age were assessed. Both observers successfully acquired 4D STIC volumes in all infants. Left ventricular output showed good reproducibility, with an intra-observer ICC of 0.86 (0.69-0.94) and inter-observer ICC of 0.87 (0.70-0.95). Right ventricular output also showed good reproducibility, with an intra-observer ICC of 0.88 (0.70-95) and inter-observer ICC of 0.84 (0.63-0.93).

CONCLUSIONS

Determining cardiac output using 4D STIC ultrasound is feasible and reproducible in well newborn infants. With further evaluation, this technique may provide valuable information about haemodynamic status in newborn infants requiring intensive care.

Assessment of Fetal Congenital Heart Diseases by 4-Dimensional Ultrasound Using Spatiotemporal Image Correlation: Pictorial Review

The aim of this pictorial review is to describe the technical advances achieved through the application of 4-dimensional (4D) ultrasound using spatiotemporal image correlation (STIC) over conventional 2-dimensional ultrasound in the prenatal detection of congenital heart disease (CHD). Spatiotemporal image correlation is a volume imaging technique that simplifies fetal heart studies while providing more diagnostic information than is typically available from traditional 2-dimensional studies. Four-dimensional software allows the study of cardiac anatomy and function during a single cardiac cycle and has greatly contributed to diagnostic enhancement of CHD. Color flow and power Doppler can be added to STIC in the study of vessel anatomy and to increase the detection of ventricular septal defects. Anatomical details of the fetus can be displayed in multiple images such as using computed tomography or magnetic resonance imaging. In addition, cardiac anatomy can be sectioned freely and reconstructed using different reformatting applications. Realistic views of the fetal heart, with particular emphasis on myocardium and endocardium cushion, can be reached using novel lightening techniques. Moreover, using 4D ultrasound, echolucent structures can be converted into solid voxels generating "digital casts" of the fetal heart that enhances the understanding of the great vessel relationships in the ventricular inflow and outflow tracts. Recently, sillhouette mode has shown to improve depth perception and resolution compared with conventional 3D power Doppler in the study of inflow and outflow tracts. Here, a gallery of prenatally detected CHD using 4D ultrasound with STIC and different applications is described.

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.

Time Interval Measurements of the Ductus Venosus During the Early Second Trimester of Pregnancy: Reference Ranges and Clinical Application

OBJECTIVES

The aims of this study were to construct reference ranges for the time interval parameters of the ductus venosus during the early second trimester of pregnancy and to demonstrate the clinical utility in various fetal disorders.

METHODS

The ductus venosus Doppler measurements of 331 healthy fetuses between 15 and 22 weeks' gestation were analyzed. The systolic time and diastolic time were subdivided into the systolic acceleration time, systolic deceleration time, diastolic acceleration time, and diastolic deceleration time. The median, 5th, and 95th regression lines for each variable were determined according to gestational age. The ductus venosus time interval parameters in cases of fetoplacental abnormalities were calculated and plotted against the reference ranges.

RESULTS

With advancing gestation, the systolic acceleration time and total systolic time increased significantly (P < .001). In contrast to the systolic phase, the diastolic deceleration time decreased significantly during the early second trimester of pregnancy (P = .023). The systolic deceleration time, diastolic acceleration time, and diastolic time were relatively constant. Fetuses with tricuspid insufficiency, twin-twin transfusion syndrome, intrauterine fetal growth restriction, and anemia had abnormal ductus venosus times with different patterns.

CONCLUSIONS

Predicted normal reference ranges for time interval variables in relation to gestational age were established. These could be helpful for assessing fetal cardiovascular function during the early second trimester of pregnancy.

Three- and four-dimensional ultrasound in fetal echocardiography: an up-to-date overview

Congenital heart diseases (CHD) are the most commonly overlooked lesions in prenatal screening programs. Real-time two-dimensional ultrasound (2DUS) is the conventionally used tool for fetal echocardiography. Although continuous improvements in the hardware and post-processing software have resulted in a good image quality even in late first trimester, 2DUS still has its limitations. Four-dimensional ultrasound with spatiotemporal image correlation (STIC) is an automated volume acquisition, recording a single three-dimensional (3D) volume throughout a complete cardiac cycle, which results in a four-dimensional (4D) volume. STIC has the potential to increase the detection rate of CHD. The aim of this study is to provide a practical overview of the possibilities and (dis)advantages of STIC. A review of literature and evaluation of the current status and clinical value of 3D/4D ultrasound in prenatal screening and diagnosis of congenital heart disease are presented.

Image-Derived Assessment of Left Ventricular Mass in Fetal Myocardial Hypertrophy by 4-Dimensional Echocardiography: An In Vitro Study

OBJECTIVES

This study tested the accuracy of new 4-dimensional fetal echocardiography to evaluate left ventricular (LV) mass in an experimental model of fetal myocardial hypertrophy.

METHODS

Ten fresh rabbit hearts were studied. Fetal myocardial hypertrophy was simulated by fixing different amounts of myocardial tissue to the LV epicardium. A small latex balloon was mounted on vinyl tubing and fixed within each LV cavity. The proximal end of the tube was attached to a pulsatile pump apparatus. The pump was calibrated to deliver stroke volumes of 2 and 4 mL at stroke rates of 60 and 120 beats per minute (bpm). Four-dimensional data were acquired and analyzed with quantification software. Reference values for LV mass were determined by the displacement method.

RESULTS

Echo-derived measurements of LV mass showed good correlations with reference values at all stroke rates and stroke volumes: at 2 mL and 60 bpm, r = 0.95; at 2 mL and 120 bpm, r = 0.95; at 4 mL and 60 bpm, r = 0.93; and at 4 mL and 120 bpm, r = 0.95 (P< .01 for all values). There was also excellent interobserver (r = 0.98; mean difference of -0.32 g; -4.4% of the mean) and intraobserver (r = 0.98; mean difference of -0.28 g; -3.8% of the mean) agreement.

CONCLUSIONS

In this controlled in vitro study, high-resolution 4-dimensional echocardiography was shown to accurately assess LV mass and have the potential to evaluate fetal myocardial hypertrophy.

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.

Evaluation of right ventricular function in fetal hypoplastic left heart syndrome using spatio-temporal image correlation (STIC)

Background

Postnatal outcome of fetuses with hypoplastic left heart syndrome (HLHS) is mainly determined by right ventricular function. In the present study we used spatio-temporal image correlation (STIC) to assess right ventricular function of fetuses with HLHS.

Methods

Three-dimensional ultrasound with STIC technique was used to acquire heart images from fetuses that had HLHS and the normal controls, between 24⁺⁰ and 37⁺⁶ weeks of gestation. Right ventricular end-diastolic volume (RVEDV) and right ventricular end-systolic volume (RVESV) were determined using the virtual organ computer-aided analysis software, and the parameters of right ventricular function were calculated.

Results

Both RVEDV and RVESV were found to be significantly higher in fetuses with HLHS as compared to that in normal controls (P < 0.001). There were no significant differences in the parameters between fetuses with and without a visible left ventricular cavity (P > 0.05). Compared to fetuses with HLHS plus mild tricuspid regurgitation (TR), fetuses with HLHS plus severe TR exhibited lower right ventricular stroke volume (RVSV), right ventricular cardiac output (RVCO) and standardized RVCO (P < 0.05). The right ventricular ejection fraction (RVEF) was significantly lower in HLHS fetuses that had severe TR (P < 0.001).

Conclusion

As the right ventricle is solely responsible for maintenance of circulation, the right ventricular systolic function undergoes compensatory enhancement in fetuses with HLHS and mild TR, compared to that in normal controls. Size of the left ventricle does not significantly affect the right ventricular function in HLHS. However, right ventricular systolic function may be impaired prenatally in HLHS fetuses that have severe TR.

Role of 3-D ultrasound in clinical obstetric practice: evolution over 20 years

The use of 3-D ultrasound in obstetrics has undergone dramatic development over the past 20 years. Since the first publications on this application in clinical practice, several 3-D ultrasound techniques and rendering modes have been proposed and applied to the study of fetal brain, face and cardiac anatomy. In addition, 3-D ultrasound has improved calculations of the volume of fetal organs and limbs and estimations of fetal birth weight. And furthermore, angiographic patterns of fetal organs and the placenta have been assessed using 3-D power Doppler ultrasound quantification. In this review, we aim to summarize current evidence on the clinical relevance of these methodologies and their application in obstetric practice.

Real Time Three-Dimensional Echocardiographic Evaluations of Fetal Left Ventricular Stroke Volume, Mass, and Myocardial Strain: In Vitro and In Vivo Experimental Study

BACKGROUND

Left ventricular stroke volume, mass, and myocardial strain are valuable indicators of fetal heart function. This study investigated the feasibility of nongated real time three-dimensional echocardiography (RT3DE) to determine fetal stroke volume (SV), left ventricular mass (LVM), and myocardial strain under different conditions.

METHODS

To evaluate fetal hearts, fetal-sized rabbit hearts were used in this study. The in vitro portion of this study was carried out using a balloon inserted into the LV of eight fresh rabbit hearts and driven by a calibrated pulsatile pump. RT3DE volumes were obtained at various pump-set SVs. The in vivo experiments in this study were performed on open-chest rabbits. RT3DE volumes were acquired at the following conditions: baseline, simulated hypervolemia, inferior vena cava (IVC) ligation, and ascending aorta (AAO) ligation. Displacement values and sonomicrometry data were used as references for RT3DE-derived SV, LVM, longitudinal strain (LS), and circumferential strain (CS).

RESULTS

Excellent correlations between RT3DE-derived values and reference values were demonstrated and accompanied by high coefficients of determination (R(2) ) for both in vitro and in vivo studies for SV, LVM, LS, and CS (in vitro: SV: R(2)  = 0.98; LVM: R(2)  = 0.97; LS: R(2)  = 0.87, CS: R(2)  = 0.80; in vivo: SV: R(2)  = 0.92; LVM: R(2)  = 0.98; LS: in vivo: R(2)  = 0.84; CS: in vivo: R(2)  = 0.76; all P < 0.05).

CONCLUSIONS

RT3DE is capable of quantifying the SV, LVM, and myocardial strain of fetal-sized hearts under different conditions. This nongated RT3DE may aid the evaluation of fetal cardiac function, providing a superior understanding of the progress of fetal heart disorders.

4D Fetal Echocardiography in Clinical Practice

Spatiotemporal image correlation (STIC) is a technique that acquires the fetal cardiac volumes, and then analyzes it offline in both multiplanar and rendered modes, using both static and moving images from a four-dimensional (4D) cine sequence simulating a full cardiac cycle. Spatiotemporal image correlation makes it possible to evaluate cardiac structures and their vascular connections, is less operator dependent, and allows cardiac volumes to be sent to specialists in tertiary centers for examination. Spatiotemporal image correlation can be combined with other software techniques, such as virtual organ computer-aided analysis (VOCAL) and automatic volume calculation (SonoAVC), to calculate cardiac function parameters. It can also be used in association with Omniview® in order to obtain standard echocardiographic planes using simple targets arterial rendering (STAR) and four-chamber view and swing technique (FAST). Recently, fetal intelligent navigation echocardiography (FINE), acquired from 3D STIC volumes, has made it possible to automatically obtain nine standard echocardiographic planes. In this article, we review the chief applications of 4D echocardiography using STIC technique in clinical practice.

How to cite this article

Araujo Júnior E, Tedesco GD, Carrilho MC, Peixoto AB, Carvalho FHC. 4D Fetal Echocardiography in Clinical Practice. Donald School J Ultrasound Obstet Gynecol 2015;9(4): 382-396.

New technique for assessing fetal heart growth using three-dimensional ultrasonography: description of the technique and reference curves

OBJECTIVE

To describe a new technique for assessing fetal growth using three-dimensional ultrasonography (3DUS) using the extended imaging virtual organ computer-aided analysis (XI VOCAL) software and its respective reference curves.

METHODS

We conducted a cross-sectional study on 303 normal singleton pregnancies between their 20th and 34th weeks. To assess fetal heart growth, we used the XI VOCAL software with 10 planes in which the reference lines (beginning and end) were placed at the cardiac apex, the output level of the vessels and the base above the diaphragm, respectively. To assess the correlation between distance and interval, polynomial regressions were performed with adjustments using the coefficient of determination (R(2)). To assess the inter-observer reproducibility, we used the intraclass correlation coefficient (ICC).

RESULTS

The mean distance between the apex and the base of the fetal heart ranged from 14.41 ± 1.24 mm to 26.24 ± 2.62 mm between the 20th and 34th weeks, respectively. The mean interval between the apex and the base of the fetal heart ranged from 1.56 ± 0.13 mm and 2.94 ± 0.30 mm between the 20th and 34th weeks, respectively. We observed good correlation of distance and interval with the gestational age, with R(2) = 0.73 and 0.74, respectively. We observed a good inter-observer to the interval and distance with ICC = 0.983 and 0.996, respectively.

CONCLUSION

We described a new technique for assessing fetal heart growth using 3DUS and determined reference curves for the distance and interval between the 20th and 34th weeks of pregnancy.

Four-dimensional echocardiography with spatiotemporal image correlation and inversion mode for detection of congenital heart disease

The aim of this study was to evaluate the use of 4-D echocardiography with inversion mode and spatiotemporal image correlation (IM-STIC) in the detection of normal and abnormal fetal hearts. We retrospectively studied 112 normal fetuses and 16 fetuses with a confirmed diagnosis of congenital heart disease. Two volumes were acquired from each of the fetuses using transverse and sagittal sweeps. Volumes were reconstructed with IM-STIC. In normal fetuses, IM-STIC facilitated visualization of the interior structures of the fetal heart and great vessels. The visualization rates of intended planes obtained from IM-STIC 4D data ranged from 55% to 100%. In 16 fetuses with congenital heart disease, IM-STIC was able to display the cardiac malformations using digital casting. Some of the malformations were suspected during pre-natal 2-D echocardiography, and their pre-natal IM-STIC diagnoses were confirmed by post-natal echocardiography, surgery and/or autopsy. Hence, 4-D IM-STIC allows better visualization of complex congenital heart disease and should be considered a very useful addition to 2-D echocardiography.

Diagnosis and treatment of fetal cardiac disease: a scientific statement from the American Heart Association

BACKGROUND

The goal of this statement is to review available literature and to put forth a scientific statement on the current practice of fetal cardiac medicine, including the diagnosis and management of fetal cardiovascular disease.

METHODS AND RESULTS

A writing group appointed by the American Heart Association reviewed the available literature pertaining to topics relevant to fetal cardiac medicine, including the diagnosis of congenital heart disease and arrhythmias, assessment of cardiac function and the cardiovascular system, and available treatment options. The American College of Cardiology/American Heart Association classification of recommendations and level of evidence for practice guidelines were applied to the current practice of fetal cardiac medicine. Recommendations relating to the specifics of fetal diagnosis, including the timing of referral for study, indications for referral, and experience suggested for performance and interpretation of studies, are presented. The components of a fetal echocardiogram are described in detail, including descriptions of the assessment of cardiac anatomy, cardiac function, and rhythm. Complementary modalities for fetal cardiac assessment are reviewed, including the use of advanced ultrasound techniques, fetal magnetic resonance imaging, and fetal magnetocardiography and electrocardiography for rhythm assessment. Models for parental counseling and a discussion of parental stress and depression assessments are reviewed. Available fetal therapies, including medical management for arrhythmias or heart failure and closed or open intervention for diseases affecting the cardiovascular system such as twin-twin transfusion syndrome, lung masses, and vascular tumors, are highlighted. Catheter-based intervention strategies to prevent the progression of disease in utero are also discussed. Recommendations for delivery planning strategies for fetuses with congenital heart disease including models based on classification of disease severity and delivery room treatment will be highlighted. Outcome assessment is reviewed to show the benefit of prenatal diagnosis and management as they affect outcome for babies with congenital heart disease.

CONCLUSIONS

Fetal cardiac medicine has evolved considerably over the past 2 decades, predominantly in response to advances in imaging technology and innovations in therapies. The diagnosis of cardiac disease in the fetus is mostly made with ultrasound; however, new technologies, including 3- and 4-dimensional echocardiography, magnetic resonance imaging, and fetal electrocardiography and magnetocardiography, are available. Medical and interventional treatments for select diseases and strategies for delivery room care enable stabilization of high-risk fetuses and contribute to improved outcomes. This statement highlights what is currently known and recommended on the basis of evidence and experience in the rapidly advancing and highly specialized field of fetal cardiac care.

Antenatal architecture and activity of the human heart

We construct the components for a family of computational models of the electrophysiology of the human foetal heart from 60 days gestational age (DGA) to full term. This requires both cell excitation models that reconstruct the myocyte action potentials, and datasets of cardiac geometry and architecture. Fast low-angle shot and diffusion tensor magnetic resonance imaging (DT-MRI) of foetal hearts provides cardiac geometry with voxel resolution of approximately 100 µm. DT-MRI measures the relative diffusion of protons and provides a measure of the average intravoxel myocyte orientation, and the orientation of any higher order orthotropic organization of the tissue. Such orthotropic organization in the adult mammalian heart has been identified with myocardial sheets and cleavage planes between them. During gestation, the architecture of the human ventricular wall changes from being irregular and isotropic at 100 DGA to an anisotropic and orthotropic architecture by 140 DGA, when it has the smooth, approximately 120° transmural change in myocyte orientation that is characteristic of the adult mammalian ventricle. The DT obtained from DT-MRI provides the conductivity tensor that determines the spread of potential within computational models of cardiac tissue electrophysiology. The foetal electrocardiogram (fECG) can be recorded from approximately 60 DGA, and RR, PR and QT intervals between the P, R, Q and T waves of the fECG can be extracted by averaging from approximately 90 DGA. The RR intervals provide a measure of the pacemaker rate, the QT intervals an index of ventricular action potential duration, and its rate-dependence, and so these intervals constrain and inform models of cell electrophysiology. The parameters of models of adult human sinostrial node and ventricular cells that are based on adult cell electrophysiology and tissue molecular mapping have been modified to construct preliminary models of foetal cell electrophysiology, which reproduce these intervals from fECG recordings. The PR and QR intervals provide an index of conduction times, and hence propagation velocities (approx. 1-10 cm s(-1), increasing during gestation) and so inform models of tissue electrophysiology. Although the developing foetal heart is small and the cells are weakly coupled, it can support potentially lethal re-entrant arrhythmia.

Ultrasound assessment of fetal cardiac function

Introduction: Fetal heart evaluation with US is feasible and reproducible, although challenging due to the smallness of the heart, the high heart rate and limited access to the fetus. However, some cardiac parameters have already shown a strong correlation with outcomes and may soon be incorporated into clinical practice. Materials and Methods: Cardiac function assessment has proven utility in the differential diagnosis of cardiomyopathies or prediction of perinatal mortality in congenital heart disease. In addition, some cardiac parameters with high sensitivity such as MPI or annular peak velocities have shown promising results in monitoring and predicting outcome in intrauterine growth restriction or congenital diaphragmatic hernia. Conclusion: Cardiac function can be adequately evaluated in most fetuses when appropriate expertise, equipment and time are available. Fetal cardiac function assessment is a promising tool that may soon be incorporated into clinical practice to diagnose, monitor or predict outcome in some fetal conditions. Thus, more research is warranted to further define specific protocols for each fetal condition that may affect cardiac function.

Fetal tricuspid annular plane systolic excursion (f-TAPSE): evaluation of fetal right heart systolic function with conventional M-mode ultrasound and spatiotemporal image correlation (STIC) M-mode

OBJECTIVES

Fetal tricuspid annular plane systolic excursion (f-TAPSE) is a modified method to measure the vertical movement of the tricuspid valve annulus by M-mode ultrasound, in order to assess the fetal right heart. Evaluation of right heart function is well-recognized in pediatric and adult cardiology, but has not been studied widely in the fetus. We aimed to study f-TAPSE in the second half of gestation in normal fetuses, to establish reference ranges for this measure, to evaluate the usefulness of spatiotemporal image correlation (STIC) M-mode in obtaining it, and to compare conventional M-mode and STIC M-mode-based measures of f-TAPSE.

METHODS

We recruited gravidae presenting to our centers from 20 to 38 weeks for targeted organ scans, fetal echocardiography or third-trimester fetal surveillance, with structurally normal singleton fetuses and verified gestational age (GA). Because of the small number of subjects at the lower limit, fetuses at 20 and those at 21 weeks were combined into a single group ('21 weeks'). During the booked scan, in addition to standard biometry, M-mode was applied to the tricuspid annulus, parallel to the ventricular septum, and the amplitude of the resulting wave was measured. To allow comparison with STIC M-mode, a STIC volume was acquired and saved. In post-processing, the volume was rotated to show an apical four-chamber view, and f-TAPSE was investigated in a similar fashion to that used for conventional M-mode. Two to three measures of TAPSE were taken and the results averaged. In thirty women, measurements were performed by two observers and inter- and intraobserver variation were calculated.

RESULTS

We examined 341 fetuses at GA 20-39 weeks. Conventional M-mode f-TAPSE values ranged from a mean of 3.6 (± 1.1) mm at 21 weeks to a mean of 8.6 (± 1.5) mm at 39 weeks. In 45 cases we were unable to perform conventional M-mode ultrasound because of fetal lie; in eight cases STIC volumes were found in post-processing to be unsuitable for analysis. STIC f-TAPSE values ranged from a mean of 4.2 (± 1.4) mm at 21 weeks to a mean of 8.3 (± 1.5) mm at 39 weeks. Scatterplots of f-TAPSE measures obtained with conventional M-mode and with STIC M-mode were created vs GA and estimated fetal weight (EFW). For both modalities, f-TAPSE increased linearly with GA and with EFW. Good correlation was found between the two methods (Pearson's R(2) = 0.904). No significant difference was found in mean or variance of the distributions or slopes of the regression equations. Inter- and intraobserver variation (intraclass correlation coefficient) in conventional M-mode and STIC M-mode f-TAPSE measures were 0.94 and 0.97, respectively.

CONCLUSION

F-TAPSE in normal fetuses increases over the course of gestation and correlates to EFW. F-TAPSE measurement is easy to perform and available on all ultrasound machines; STIC f-TAPSE is possible on machines with STIC capability and produces similar measures with a greater success rate. We suggest the addition of f-TAPSE measurement to fetal right cardiac function evaluation.

Twenty-five years of fetal echocardiography in conjoined twins: lessons learned

BACKGROUND

The aim of this study was to determine the accuracy of prenatal echocardiography in the diagnosis of intracardiac malformations and the degree of cardiac fusion in conjoined twins presenting to a single center over a 25-year period.

METHODS

The study group included 53 sets of conjoined twins from 1987 to 2012, including 38 thoracopagus, six parapagus, six omphalo-ischiopagus, two omphalopagus, and one cephalopagus. Twins were classified according to the degree of cardiac fusion: separate hearts and pericardium (group A, n = 10), separated hearts and common pericardium (group B, n = 2), fused atria and separated ventricles (group C, n = 2), and fused atria and ventricles (group D, n = 39). Postmortem examination was possible in 68 individual cases (98 deaths [69.3%]).

RESULTS

Cardiac defects were diagnosed in 47 sets of twins (88.6%). In 10 (18.8%), only one fetus was affected, and in 37 (69.8%), both fetuses were affected (n = 84/106 [79.2%]). There was a high predominance of right-sided lesions (63.0% [53 fetuses in 84 affected]) including pulmonary atresia or stenosis (35.7%), tricuspid atresia (11.9%), and hypoplastic or small right ventricle (21.4%). Autopsy findings added information to fetal echocardiographic findings in nine sets of twins (25.7%). Three pairs classified antenatally in groups A, B, and D were confirmed by autopsy in groups B, C, and C, respectively.

CONCLUSIONS

This study demonstrates that specialized fetal echocardiography is not a perfect diagnostic tool but is sensitive enough to establish prognosis in the counseling process. Because of complexity, such evaluations should be performed only at tertiary centers by specialists who are familiar with the peculiarities of this rare malformation. The predominance of right-sided lesions is not only an interesting finding, but this information has essential importance in terms of shortening examination times, allowing a more focused analysis of the fetal heart.

Fetal diagnosis and imaging in cardiology

BACKGROUND

Fetal echocardiography plays a critical role in the diagnosis and management of structural, functional and rhythm-related fetal cardiovascular disease.

OBJECTIVES/METHODS

This article reviews the history of fetal echocardiography and the prenatal diagnosis of fetal cardiovascular disease as well as the evolution of the field of fetal cardiology. The clinical application of fetal echocardiography, including indications for referral, timing of referral and considerations in the diagnosis and serial assessment of fetal cardiovascular disease, is presented.

CONCLUSIONS

Newer directions in the field of fetal cardiology, including first trimester diagnoses and fetal intervention, will continue to expand its role in the evaluation and treatment of affected pregnancies in the future; however, equally as important are efforts to continue to improve prenatal detection rates.

Real-time 3-dimensional echocardiographic assessment of ventricular volume, mass, and function in human fetuses

Objectives

We sought to determine the feasibility and reproducibility of real-time 3-dimensional echocardiography (RT3DE) for evaluation of cardiac volume, mass, and function and to characterize maturational changes of these measurements in human fetuses.

Methods

Eighty pregnant women in the 2^nd and 3^rd trimesters (59 with normal fetuses and 21 with fetuses with congenital heart disease [CHD]) were enrolled. We acquired RT3DE images using a matrix-array transducer. RT3DE measurements of volume, mass, stroke volume (SV), combined cardiac output (CCO), and ejection fraction (EF) were obtained. Images were scored and analyzed by two blinded independent observers. Inter- and intraobserver variabilities and correlations between fetal cardiac indices and gestational age were determined.

Results

Fifty-two of 59 normal data sets (88%) and 9 of 21 CHD data sets (43%) were feasible for analysis. In normal fetuses, the right ventricle (RV) is larger than the left ventricle (LV) (P<0.05), but no difference exists between the LV and RV in mass, SV, CO, and CO/CCO. The EFs for the LV and RV were diminished; the RVSV/LVSV was reduced in CHD fetuses compared with normal fetuses (P<0.05). Fetal ventricular volumes, mass, SV, and CCO fit best into exponential curves with gestational age, but LVEF, RVEF, and RVSV/LVSV remain relatively constant.

Conclusions

RT3DE is feasible and reproducible for assessment of LV and RV volume, mass, and function, especially in normal fetuses. Gestational growth of these measures, except for EF, is exponential in normal and CHD fetuses. CHD fetuses exhibit diminished LV and RV EFs.

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

OBJECTIVE

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

STUDY DESIGN

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

RESULTS

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

CONCLUSION

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

Comparison of Doppler-based and three-dimensional methods for fetal cardiac output measurement

OBJECTIVE

Fetal cardiac output is conventionally measured using two-dimensional (2D) and Doppler ultrasound (Doppler). New methods based on 3D measurements of ventricular size in systole and diastole have been proposed. Our aim was to validate these tools against the conventional Doppler-based methods.

METHODS

Fetal combined cardiac output was prospectively measured at 16, 20, and 24 weeks of gestation in 15 uncomplicated pregnancies using Doppler and three different 3D algorithms [virtual organ computer-aided analysis (VOCAL), sonographic automatic volume calculation (SonoAVC), and inversion mode]. We determined the inter- and intraobserver variability of the 3D techniques and assessed the correlation between Doppler and 3D.

RESULTS

The 3D techniques showed adequate inter- and intraobserver reproducibility (intraclass correlation coefficient 0.69-0.98), with the best reproducibility for SonoAVC and inversion mode. Bland-Altman analysis revealed low bias and relatively good correlations when comparing the 3D methods among each other, albeit with wide 95% confidence intervals. Doppler measurement of fetal weight-adjusted combined cardiac output (349.0 ml·min⁻¹·kg⁻¹) yielded significantly higher results than 3D CO measurements (177.2, 160.7, and 174.0 ml·min⁻¹·kg⁻¹ for VOCAL, SonoAVC, and inversion mode, respectively; p < 0.0001) and correlated poorly with the 3D methods.

CONCLUSIONS

Although 3D volume-based cardiac output measurements are reproducible, results obtained with different methods are not interchangeable. SonoAVC and inversion have the highest intra- and interobserver reproducibility. Results of cardiac output measurement by 3D and Doppler cannot be interchanged.

Functional assessment of the fetal heart: a review

The purpose of this review is to evaluate the current modalities available for the assessment of fetal cardiac function. The unique anatomy and physiology of the fetal circulation are described, with reference to the difference between in-utero and ex-utero life. M-mode, early/atrial ratio, myocardial performance index, three-dimensional and four-dimensional ultrasound, tissue Doppler including strain and strain rate, speckle tracking, magnetic resonance imaging and venous flow assessment are described. The modalities are analyzed from the perspective of the clinician and certain questions are posed. Does the modality assess systolic function, diastolic function or both? Is it applicable to both ventricles? Does it require extensive post-processing or additional hardware, or does it make use of technology already available to the average practitioner? The reproducibility and reliability of the techniques are evaluated, with reference to their utility in clinical decision-making. Finally, directions for future research are proposed.

Reproducibility of echocardiographic measurements of human fetal left ventricular volumes and ejection fractions using four-dimensional ultrasound with the spatio-temporal image correlation modality

OBJECTIVES

To determine the reproducibility, both reliability and agreement, of measurements of fetal left ventricular parameters from volumes obtained by spatio-temporal image correlation (STIC) acquisition applying virtual organ computer-aided analysis (VOCAL) and Simpson's rule (method of discs). Furthermore the success rate of STIC acquisition was determined.

STUDY DESIGN

In 84 pregnancies between 20 and 34 weeks of gestation the fetal heart was scanned using the STIC modality. An optimal four-chamber view in end-diastole and end-systole was obtained. Left ventricular end-diastolic volume, left ventricular end-systolic volume, stroke volume and ejection fraction were determined. For calculations based on Simpson's rule only one plane was traced, whereas for VOCAL six planes were traced. To quantify the reliability intraclass correlation coefficients were calculated for both intra- and inter-observer measurements. Agreement of measurements was evaluated by Bland-Altman plots.

RESULTS

The STIC volumes of 54 women (64%) were excluded from the study because of poor quality, leaving 30 volumes for further analysis. Intraclass correlation coefficients for intra-observer reliability for VOCAL and Simpson were 0.99 and 0.99 for left ventricular end-diastolic volume, 0.95 and 0.92 for left ventricular end-systolic volume, 0.98 and 0.97 for stroke volume, 0.76 and 0.77 for ejection fraction, respectively. Intraclass correlation coefficients for inter-observer reliability for VOCAL and Simpson were 0.97 and 0.86 for left ventricular end-diastolic volume, 0.97 and 0.86 for left ventricular end-systolic volume, 0.95 and 0.81 for stroke volume, 0.68 and 0.63 for ejection fraction, respectively. According to Bland-Altman plots, the mean percentage difference and 95% limits of intra- and inter-observer agreement for left ventricular stroke volume measurements using VOCAL were -0.2 (-25.1, 24.7)% and 2.8 (-34.2, 39.8)%, respectively. For left ventricular stroke volume measured with Simpson versus VOCAL the mean percentage difference and 95% limits of agreement were -1.8 (-22.1, 18.5)%.

CONCLUSIONS

4D STIC enables reproducible measurements of left ventricular volumes. Reliability of the VOCAL mode is not essentially different from the single-plane method used in Simpson's rule. The large percentage of poor quality STIC volumes and the wide limits of inter-observer agreement would create obstacles for the clinical applicability of this technique.

Fetal heart ventricular mass obtained by STIC acquisition combined with inversion mode and VOCAL

OBJECTIVE

Estimation of fetal heart ventricular mass is important for fetal cardiac evaluation in cases of structural or functional cardiac disorders or extracardiac factors. It may be used with other cardiac parameters to ascertain the severity and prognosis of such disorders, or the nature and timing of intervention. We applied a novel technique combining spatiotemporal image correlation (STIC) with three-dimensional inversion mode and Virtual Organ Computer-aided AnaLysis (VOCAL™) for fetal cardiac mass assessment in healthy fetuses in the second and third trimesters.

METHODS

STIC acquisition was performed during fetal quiescence with the abdomen uppermost, at an angle of 30-50°, without color Doppler mapping. Myocardial volume measurements were performed in postprocessing using VOCAL mode, set to 15°. Beginning with the heart in four-chamber view at end diastole, a trace was drawn manually including the myocardium and interventricular septum. Inversion mode colors the intraventricular (anechoic, fluid-filled) voxels; this intraventricular volume was subtracted automatically from the total. Mass was determined by multiplying the result by the estimated fetal myocardial density (1.050 g/cm(3) ). The process was repeated for right and left ventricles.

RESULTS

Data from 106 fetuses at 21-38 weeks' gestation were obtained and scatterplots of fetal cardiac ventricular mass distribution were created. Several cases of fetuses with disordered cardiac ventricle (supraventricular tachycardia, hypoplastic left heart syndrome, dilated cardiomyopathy, twin-to-twin transfusion syndrome, Ebstein anomaly, non-immune hydrops fetalis, septate right atrium and diaphragmatic hernia) were examined. Ventricular mass parameters were markedly affected as compared with normal cases of similar gestational age.

CONCLUSIONS

STIC acquisition combined with inversion mode and VOCAL is a feasible method of cardiac ventricular mass quantification. This methodology may have added value in fetal cardiac evaluation in cases of anatomic malformation or cardiac dysfunction, or in cases of maternal diabetes.

Fetal cardiac ventricular volume, cardiac output, and ejection fraction determined with 4-dimensional ultrasound using spatiotemporal image correlation and virtual organ computer-aided analysis

OBJECTIVE

The objective of this study was to quantify fetal cardiovascular parameters using spatiotemporal image correlation (STIC) and virtual organ computer-aided analysis (VOCAL).

STUDY DESIGN

A cross-sectional study was performed in normal pregnancies (19-42 weeks) to evaluate ventricular volume, stroke volume (SV), cardiac output (CO), and ejection fraction (EF). The CO was also expressed as a function of estimated fetal weight and biometric parameters.

RESULTS

The following results were found: (1) 184 STIC datasets; (2) with advancing gestation, ventricular volume, SV, CO, and adjusted CO increased, whereas EF decreased; (3) right ventricular (RV) volume was larger than the left ventricular (LV) volume in systole (0.50 vs 0.27 mL; P < .001) and diastole (1.20 vs 1.03 mL; P < .001); (4) there were no differences between the LV and RV in SV, CO, or adjusted CO; and (5) LV EF was greater than the RV EF (72.2 vs 62.4%; P < .001).

CONCLUSION

Normal fetal cardiovascular physiology is characterized by a larger RV volume and a greater LV EF, resulting in similar LV and RV SV and CO.

Techniques for assessing cardiac output and fetal cardiac function

Fetal echocardiography was initially used to diagnose structural heart disease, but recent interest has focused on functional assessment. Effects of extracardiac conditions on the cardiac function such as volume overload (in the recipient in twin-twin transfusion syndrome), a hyperdynamic circulation (arterio-venous malformation), cardiac compression (diaphragmatic hernia, lung tumours) and increased placental resistance (intrauterine growth restriction and placental insufficiency) can be studied by ultrasound and may guide decisions for intervention or delivery. A variety of functional tests can be used, but there is no single clinical standard. For some specific conditions, however, certain tests have shown diagnostic value.

Heart stroke volume, cardiac output, and ejection fraction in 265 normal fetus in the second half of gestation assessed by 4D ultrasound using spatio-temporal image correlation

OBJECTIVES

The aim of this study was to establish nomograms for fetal stroke volume (SV), cardiac output (CO), and ejection fraction (EF) using four-dimensional ultrasound with spatio-temporal image correlation (STIC) modality.

METHODS

The fetal heart was scanned using STIC modality, starting with classic four-chamber view plane, during fetal quiescence with abdomen uppermost, at an angle of 20-30°, without color Doppler flow mapping. In post-processing virtual organ, computer-aided analysis technique was used to obtain a sequence of six sections of each ventricular volume in end-systolic volume (ESV) and end-diastolic volume (EDV). The SV (SV = EDV-ESV), CO (CO = SV × fetal heart rate), and EF (EF = SV/EDV) for each ventricle were then calculated. Intra- and interobserver agreement were then calculated.

RESULTS

Two hundred sixty-five fetuses, ranging in gestational age (GA) from 20 to 34(+6) weeks, were included in the study. The left and right SV and CO increased exponentially with gestation and EF remained fairly stable through gestational. Mean left and right SV increased from 0.211 ml and 0.220 ml at 20 weeks to 1.925 ml and 2.043 ml, respectively, at 34 weeks. Mean left and right CO increased from 30.25 ml/min and 31.52 ml/min at 20 weeks to 268.49 ml/min and 287.80 ml/min, respectively, at 34 weeks. Both left and right mean EF remained constant at around 0.63 with advancing GA. Nomograms were created for LSV, RSV, LCO, RCO, LEF, and REF vs. gestational age. Intra- and interobserver agreement reached 95%.

CONCLUSIONS

Four-dimensional ultrasound using STIC represents a simple and reproducible method for estimating fetal cardiac function. STIC seems to overcome many of the pitfalls of conventional ultrasound methods and has the potential to become the method of choice.

Fetal cardiac function assessed by spatio-temporal image correlation

BACKGROUND

Three-dimensional (3D) and four-dimensional (4D) ultrasound have been proposed to be valuable tools for the examination of fetal heart. Spatio-temporal image correlation (STIC) is a technique that adds a time component to 3D ultrasound imaging of the fetal heart, so we can evaluate cardiac structures as a 4D cine sequence containing information of one full cardiac cycle. STIC gives the investigator the opportunity to freeze the displayed cardiac loop in end-diastolic and end-systolic phases. By STIC, 3D measurements of both the left and right ventricle can be used to calculate fetal heart stroke volume, cardiac output and ejection fraction, and expressions of cardiac function. The ultimate goal of STIC technique is to improve fetal cardiac function analysis by decreasing the dependency on operator skills required by two-dimensional ultrasound.

CONTEXT

In this article, we describe literature practical approach for the examination of the fetal heart function using 4D ultrasound by STIC technique.

Four-dimensional volume-rendered imaging of the fetal ventricular outflow tracts and great arteries using inversion mode for detection of congenital heart disease

AIM

Using four-dimensional (4D) sonography with an inversion mode, we evaluated fetal ventricular outflow tracts and great vessels for the detection of congenital heart disease.

METHODS

Volume datasets of the fetal heart were acquired with spatiotemporal image correlation (STIC), which uses automated transverse and longitudinal sweeps of the anterior chest wall. A total of 12 normal fetuses and seven fetuses with congenital heart disease (one case of double-outlet right ventricle, one case of tetralogy of Fallot, one case of transposition of the great arteries, one case of hypoplastic pulmonary artery with a large ventricular septal defect, and three cases of hypoplastic left heart syndrome) at 16-37 weeks of gestation were studied using transabdominal 4D sonography with an inversion mode. 4D inversion mode images of great arteries were evaluated.

RESULTS

4D ultrasound with an inversion mode demonstrated real-time 3D angiographic features of fetal cardiac outflow tracts in both normal and abnormal fetal hearts. This modality facilitated visualization of the relationships, size, and course of the outflow tracts, thus helping the examiner to more effectively understand the spatial relationships between the vessels. In normal fetal hearts, it was clearly shown that the pulmonary artery crosses in front of the aorta. In the three cases of hypoplastic left heart syndrome, an extremely small ascending aorta was evident. In the one case of tetralogy of Fallot, a relatively small pulmonary artery was noted. In the one case of hypoplastic pulmonary artery with a large ventricular septal defect, a markedly small main pulmonary artery was depicted. In the case of transposition of the great arteries, the vessels left the ventricles parallel to each other. In the case of double-outlet right ventricle, great arteries leaving the right ventricle in parallel were shown.

CONCLUSION

4D ultrasound in the inversion mode provides a means of evaluating fetal cardiac outflow tracts in 3D in real time. This technique may assist in the evaluation of spatial relationships between the great vessels and both ventricles, and the difference in the size of great vessels. Moreover, the inversion mode images should be more readily discernible than those obtained by conventional ultrasonography. 4D ultrasound in the inversion mode may be an important modality in future fetal cardiac research and in the evaluation of fetal congenital heart disease.

Reliability of fetal cardiac volumetry using spatiotemporal image correlation: assessment of in-vivo and in-vitro measurements

OBJECTIVE

To assess the reliability of measurement of fetal cardiac ventricular volume, stroke volume, and ejection fraction with four-dimensional ultrasound using spatiotemporal image correlation (STIC).

METHODS

Volume datasets were collected from two sources: 24 from fetuses over a range of gestational ages and 12 from a miniature balloon model. Datasets were analyzed by three observers, repeatedly in 12 fetal datasets and all balloon datasets. Volume calculations were obtained by manually tracing multiple parallel slices (three-dimensional (3D) slice method). Measurement error was assessed by calculating standard errors of measurement (SEM) and coefficients of variation (CV). Reliability was assessed by calculating interobserver and intraobserver intraclass correlation coefficients (ICC).

RESULTS

Measurement errors of balloon volumes were small and reliability was good (SEM <or= 0.07 mL, ICC 0.98-1.00). Fetal ventricle volume measurement error ranged from 0.09 to 0.20 mL and CV from 14.6 to 28.3%. Ventricular volume reliabilities for intra- and interobserver comparisons were greater than or equal to 0.94 and 0.75, respectively. Fetal stroke volume measurement error (SEM 0.17 mL), CV (21.9%) and reliability were measured (intraobserver ICC: left ventricle stroke volume (LVSV), 0.93 vs. right ventricle stroke volume (RVSV), 0.88; interobserver ICC: LVSV, 0.75 vs. RVSV, 0.86). The measurement error decreased with increasing operator experience. The reliability of ejection fraction calculations was poor (ICC < 0.7) for intra- and interobserver comparisons.

CONCLUSIONS

Volume measurements obtained with STIC and 3D slice methods using a balloon model were reliable. In the fetus, measurement errors decreased with increasing operator experience, and reliability was better for stroke volume than for ejection fraction.