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

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.

Cardiac remodeling during the neonatal intensive care period; a window of opportunity for early prevention of heart failure?

BACKGROUND

There is growing evidence that preterm birth is a risk factor for early heart failure as a result of cardiac remodeling during a critical period of growth and development. The aim of this study was to explore if cardiac remodeling can be detected very early after preterm birth, and if present, if those remodeling changes persist until discharge.

METHODS

Echocardiography parameters of left ventricular geometry and function were prospectively obtained with echocardiography in preterm infants <30 weeks gestation at postnatal day 3 and at 36 weeks postmenstrual age (PMA). Findings were compared to available data of healthy fetuses and cardiac remodeling was classified based on changes in left ventricular volume and/or mass.

RESULTS

65 (37 male) preterm infants were analysed. Three days after birth, 27.7% of infants had abnormal LV geometry, with immaturity and fetal growth restriction as risk factors for these early cardiac remodeling changes. At 36 weeks PMA, after a median period of 9 weeks of neonatal intensive care, 69.2% had abnormal cardiac geometry which could be classified as dilated hypertrophic remodeling (50.0%), dilated remodeling (11.5%) and hypertrophic remodeling (7.7%).

CONCLUSION

Cardiac remodeling changes can be detected very early after preterm birth. However, most changes take place during the neonatal intensive care period. The findings of this study could assist in identifying a group where an early and short-term intervention has the potential to prevent a pathway of abnormal cardiac development.

Evaluation of right ventricular volume and systolic function in normal fetuses using intelligent spatiotemporal image correlation

BACKGROUND

Heart defects are the most common congenital malformations in fetuses. Fetal cardiac structure and function abnormalities lead to changes in ventricular volume. As ventricular volume is an important index for evaluating fetal cardiovascular development, an effective and reliable method for measuring fetal ventricular volume and cardiac function is necessary for accurate ultrasonic diagnosis and effective clinical treatment. The new intelligent spatiotemporal image correlation (iSTIC) technology acquires high-resolution volumetric images. In this study, the iSTIC technique was used to measure right ventricular volume and to evaluate right ventricular systolic function to provide a more accurate and convenient evaluation of fetal heart function.

AIM

To investigate the value of iSTIC in evaluating right ventricular volume and systolic function in normal fetuses.

METHODS

Between October 2014 and September 2015, a total of 123 pregnant women received prenatal ultrasound examinations in our hospital. iSTIC technology was used to acquire the entire fetal cardiac volume with off-line analysis using QLAB software. Cardiac systolic and diastolic phases were defined by opening of the atrioventricular valve and the subsequent closure of the atrioventricular valve. The volumetric data of the two phases were measured by manual tracking and summation of multiple slices and recording of the right ventricular end-systolic volume and the right ventricular end-diastolic volume. The data were used to calculate the right stroke volume, the right cardiac output, and the right ejection fraction. The correlations of changes between the above-mentioned indices and gestational age were analyzed. The right ventricular volumes of 30 randomly selected cases were measured twice by the same sonographer, and the intra-observer agreement measurements were calculated.

RESULTS

Among the 123 normal fetuses, the mean right ventricular end-diastolic volume increased from 0.99 ± 0.34 mL at 22 wk gestation to 3.69 ± 0.36 mL at 35⁺⁶ wk gestation. The mean right ventricular end-systolic volume increased from 0.43 ± 0.18 mL at 22 wk gestation to 1.36 ± 0.22 mL at 35⁺⁶ wk gestation. The mean right stroke volume increased from 0.62 ± 0.29 mL at 22 wk gestation to 2.33 ± 0.18 mL at 35⁺⁶ wk gestation. The mean right cardiac output increased from 92.23 ± 40.67 mL/min at 22 wk gestation to 335.83 ± 32.75 mL/min at 35⁺⁶ wk gestation. Right ventricular end-diastolic volume, right ventricular end-systolic volume, right stroke volume, and right cardiac output all increased with gestational age and the correlations were linear (P < 0.01). Right ejection fraction had no apparent correlation with gestational age (P > 0.05).

CONCLUSION

Fetal right ventricular volume can be quantitatively measured using iSTIC technology with relative ease and high repeatability. iSTIC technology is expected to provide a new method for clinical evaluation of fetal cardiac function.

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.

Three-Dimensional Echocardiography-derived strain values acquired by a novel analysis program

OBJECTIVE

This in vitro study calculated longitudinal strain (LS) from different ultrasound systems (GE Vivid E9 and Philips IE 33) before and after myocardial infarct (MI) using a vendor-independent analysis software package (TomTec's 4D LV Analysis) to validate the variation of two ultrasound systems.

METHODS

Ten freshly harvested porcine hearts were passively driven by a pulsatile pump apparatus at stroke volumes (SV) 30-70 mL. Full-volume three-dimensional echocardiography (3DE) data were acquired before and after MI using two different ultrasound systems. LS was derived from TomTec and validated against sonomicrometry data.

RESULTS

Linear regression analyses showed excellent correlations between TomTec-calculated LS values and sonomicrometry data for both normal and simulated MI groups (GE: R²  = 0.72/0.68, Philip: R²  = 0.71/0.66). Bland-Altman analyses demonstrated overestimation of echo-derived strain values for all groups. Both ultrasound system-derived strain values demonstrated decreased LS after MI, and the average change in strain after infarct was roughly 30% in GE images and 25% in Philips images.

CONCLUSIONS

Both GE and Philips echocardiographic systems can be analyzed with TomTec's program, and these images correlated well with sonomicrometry with acceptable variations.

Model of Human Fetal Growth in Hypoplastic Left Heart Syndrome: Reduced Ventricular Growth Due to Decreased Ventricular Filling and Altered Shape

INTRODUCTION

Hypoplastic left heart syndrome (HLHS) is a congenital condition with an underdeveloped left ventricle (LV) that provides inadequate systemic blood flow postnatally. The development of HLHS is postulated to be due to altered biomechanical stimuli during gestation. Predicting LV size at birth using mid-gestation fetal echocardiography is a clinical challenge critical to prognostic counseling.

HYPOTHESIS

We hypothesized that decreased ventricular filling in utero due to mitral stenosis may reduce LV growth in the fetal heart via mechanical growth signaling.

METHODS

We developed a novel finite element model of the human fetal heart in which cardiac myocyte growth rates are a function of fiber and cross-fiber strains, which is affected by altered ventricular filling, to simulate alterations in LV growth and remodeling. Model results were tested with echocardiogram measurements from normal and HLHS fetal hearts.

RESULTS

A strain-based fetal growth model with a normal 22-week ventricular filling (1.04 mL) was able to replicate published measurements of changes between mid-gestation to birth of mean LV end-diastolic volume (EDV) (1.1-8.3 mL) and dimensions (long-axis, 18-35 mm; short-axis, 9-18 mm) within 15% root mean squared deviation error. By decreasing volumetric load (-25%) at mid-gestation in the model, which emulates mitral stenosis in utero, a 65% reduction in LV EDV and a 46% reduction in LV wall volume were predicted at birth, similar to observations in HLHS patients. In retrospective blinded case studies for HLHS, using mid-gestation echocardiographic data, the model predicted a borderline and severe hypoplastic LV, consistent with the patients' late-gestation data in both cases. Notably, the model prediction was validated by testing for changes in LV shape in the model against clinical data for each HLHS case study.

CONCLUSION

Reduced ventricular filling and altered shape may lead to reduced LV growth and a hypoplastic phenotype by reducing myocardial strains that serve as a myocyte growth stimulus. The human fetal growth model presented here may lead to a clinical tool that can help predict LV size and shape at birth based on mid-gestation LV echocardiographic measurements.

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.

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.

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.

Factors associated with in utero demise of fetuses that have underlying cardiac pathologies

Factors associated with in utero fetal demise (IUFD) of fetuses that have underlying cardiac pathologies are largely unknown. This case-control study aimed to define the prevalence of IUFD in fetuses with a diagnosis of cardiac pathologies and to identify prenatal predictors of IUFD. Between January 2004 and December 2010, 74 IUFD cases [4.6 %; 95 % confidence interval (CI) 3.7-5.8 %] were identified from 1,584 cases with a diagnosis of structural or functional cardiac lesions in the Hospital for Sick Children database. The cases were divided into right-sided (N = 28), left-sided (N = 23), great artery (N = 8), and miscellaneous (N = 15) groups. The control subjects (1:1 ratio) were fetuses that had cardiac pathology diagnosed within 48 h of the IUFD case. Multivariable regression models were used to determine echocardiographic predictors of IUFD. The prevalence of IUFD was greatest in hypertrophic cardiomyopathy (8/16, 50 %) and Ebstein's anomaly/tricuspid dysplasia (4/15, 27 %) and lowest in transposition of the great arteries (2/85, 1 %). The findings showed IUFD to be associated with hydrops in 17 (23 %) of the 74 cases and arrhythmia in 11 (15 %) of the 74 cases. The factors identified by univariable logistic regression analyses were right ventricular dysfunction [odds ratio (OR) 2.7; p = 0.001], left ventricular dysfunction (OR 1.8; p = 0.007), umbilical vein pulsations (OR 10.9; p = 0.002), and abnormal ductus venosus flow (OR 3.3; p = 0.01). The factors associated with IUFD in multivariable logistic regression models were cardiomegaly (OR 5.6; p = 0.01), hydrops (OR 29.5; p = 0.001), pericardial effusion (OR 4.1; p = 0.06), and extracardiac abnormalities (OR 7.2; p < 0.001). The prevalence of IUFD is greatest in conditions affecting the ventricular myocardium. The onset of IUFD appears to be related initially to right ventricular dysfunction. Closer surveillance is recommended for lesions at risk of IUFD.

Fetal cardiac interventricular septum: volume assessment by 3D/4D ultrasound using spatio-temporal image correlation (STIC) and virtual organ computer-aided analysis (VOCAL)

OBJECTIVE

To determine reference values for fetal interventricular septum (IVS) volume by 3D/4D ultrasound using spatio-temporal image correlation (STIC) and virtual organ computer-aided analysis (VOCAL).

METHODS

A prospective cross-sectional study was conducted on 200 consecutive normal low-risk pregnant women at a gestational age ranging from 18w0d to 33w6d. The volume data sets of the fetal heart were acquired by applying STIC to a four-chamber plane. IVS volume was calculated offline using VOCAL with rotation of 30° (six planes). To assess the correlation of fetal IVS volume as a function of gestational age (GA), Pearson's correlation coefficient (r) and polynomial regression models with adjustments through the coefficient of determination (R(2)) were calculated. The intra-class coefficient (ICC) was used to evaluate intra- and inter-observer reproducibility.

RESULTS

A good correlation between GA and fetal IVS volume (r = 0.827) was observed. The mean fetal IVS volume ranged from 0.13 ± 0.03 cm(3) (0.08-0.18 cm(3)) at 18wd0 of gestation to 1.33 ± 0.37 cm(3) (0.41-1.98 cm(3)) at 33w6d. The best correlation between fetal IVS volume and GA was exponential: fetal IVS volume = 0.11e(0.139×GA) (R(2 )= 0.785). A good intra- and inter-observer reliability were observed, with ICC = 0.999 and 0.991, respectively.

CONCLUSIONS

Reference values for fetal IVS volume using STIC and VOCAL by 3D/4D ultrasound between 18w0d and 33w6d of gestation were determined and showed to be reliable and concordant.

Fetal left ventricular mass determination on 2-dimensional echocardiography using area-length calculation methods

OBJECTIVES

Fetal cardiac examination is an important part of fetal malformation screening. The purposes of this study were to describe the left ventricular (LV) mass in the second and third trimesters by 2-dimensional echocardiography using area-length calculation methods and to examine the clinical usefulness of this procedure in evaluation of gestational age (GA)- and fetal weight-related LV mass changes.

METHODS

Five hundred healthy fetuses were divided into 2 groups (250 participants per group): second- and third-trimester groups. The estimated fetal weight (EFW) was computed according to the Hadlock formula (Radiology 1984; 150:535-540). The LV mass at end diastole (LVd mass) and LV mass at end systole (LVs mass) were measured, and the difference between the LVd mass and LVs mass [LV(d-s) mass], LVd mass/EFW ratio, and LVs mass/EFW ratio were calculated.

RESULTS

The EFW, LVd mass, LVs mass, and LV(d-s) mass were all significantly greater in the third-trimester group than the second-trimester group (P < .05), whereas the LVd mass/EFW and LVs mass/EFW ratios did not differ between the groups (P > .05). The LVd mass, LVs mass, and LV(d-s) mass all significantly correlated with GA and weight (P< .001), but the LVd mass/EFW and LVs mass/EFW ratios did not (P > .05).

CONCLUSIONS

Two-dimensional echocardiography using area-length calculation methods can effectively provide measurements for LV mass and can sensitively indicate fetal weight- and GA -related changes in LV mass. Fetal cardiac mass measurement is a useful parameter for evaluation of fetal heart development.

Fetal Intelligent Navigation Echocardiography (FINE): a novel method for rapid, simple, and automatic examination of the fetal heart

OBJECTIVE

To describe a novel method (Fetal Intelligent Navigation Echocardiography (FINE)) for visualization of standard fetal echocardiography views from volume datasets obtained with spatiotemporal image correlation (STIC) and application of 'intelligent navigation' technology.

METHODS

We developed a method to: 1) demonstrate nine cardiac diagnostic planes; and 2) spontaneously navigate the anatomy surrounding each of the nine cardiac diagnostic planes (Virtual Intelligent Sonographer Assistance (VIS-Assistance®)). The method consists of marking seven anatomical structures of the fetal heart. The following echocardiography views are then automatically generated: 1) four chamber; 2) five chamber; 3) left ventricular outflow tract; 4) short-axis view of great vessels/right ventricular outflow tract; 5) three vessels and trachea; 6) abdomen/stomach; 7) ductal arch; 8) aortic arch; and 9) superior and inferior vena cava. The FINE method was tested in a separate set of 50 STIC volumes of normal hearts (18.6-37.2 weeks of gestation), and visualization rates for fetal echocardiography views using diagnostic planes and/or VIS-Assistance® were calculated. To examine the feasibility of identifying abnormal cardiac anatomy, we tested the method in four cases with proven congenital heart defects (coarctation of aorta, tetralogy of Fallot, transposition of great vessels and pulmonary atresia with intact ventricular septum).

RESULTS

In normal cases, the FINE method was able to generate nine fetal echocardiography views using: 1) diagnostic planes in 78-100% of cases; 2) VIS-Assistance® in 98-100% of cases; and 3) a combination of diagnostic planes and/or VIS-Assistance® in 98-100% of cases. In all four abnormal cases, the FINE method demonstrated evidence of abnormal fetal cardiac anatomy.

CONCLUSIONS

The FINE method can be used to visualize nine standard fetal echocardiography views in normal hearts by applying 'intelligent navigation' technology to STIC volume datasets. This method can simplify examination of the fetal heart and reduce operator dependency. The observation of abnormal echocardiography views in the diagnostic planes and/or VIS-Assistance® should raise the index of suspicion for congenital heart disease.

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.

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.

Fetal cardiac function: technical considerations and potential research and clinical applications

Fetal echocardiography was initially used to detect structural anomalies but has more recently also been proposed to assess fetal cardiac function. This review summarizes technical issues and limitations in fetal cardiac function evaluation, as well as its potential research and clinical applications. Functional echocardiography has been demonstrated to select high-risk populations and to be associated with outcome in several fetal conditions including intrauterine growth restriction, twin-to-twin transfusion syndrome, maternal diabetes, and congenital diaphragmatic hernia. Fetal heart evaluation is challenging due to the smallness and high heart rate of the fetus and restricted access to the fetus far from the transducer. Due to these limitations and differences in cardiac function which are related to fetal maturation, cardiovascular parameters should be validated in the fetus and used with caution. Despite these precautions, in expert hands and with appropriate ultrasound equipment, evaluation of cardiac function is feasible in most fetuses. Functional fetal echocardiography is a promising tool that may soon be incorporated into clinical practice. Research is warranted to further refine the contribution of fetal cardiac assessment to the diagnosis, monitoring, or prediction of outcomes in various fetal conditions.