Automatic segmentation of 15 critical anatomical labels and measurements of cardiac axis and cardiothoracic ratio in fetal four chambers using nnU-NetV2

BACKGROUND

Accurate segmentation of critical anatomical structures in fetal four-chamber view images is essential for the early detection of congenital heart defects. Current prenatal screening methods rely on manual measurements, which are time-consuming and prone to inter-observer variability. This study develops an AI-based model using the state-of-the-art nnU-NetV2 architecture for automatic segmentation and measurement of key anatomical structures in fetal four-chamber view images.

METHODS

A dataset, consisting of 1,083 high-quality fetal four-chamber view images, was annotated with 15 critical anatomical labels and divided into training/validation (867 images) and test (216 images) sets. An AI-based model using the nnU-NetV2 architecture was trained on the annotated images and evaluated using the mean Dice coefficient (mDice) and mean intersection over union (mIoU) metrics. The model's performance in automatically computing the cardiac axis (CAx) and cardiothoracic ratio (CTR) was compared with measurements from sonographers with varying levels of experience.

RESULTS

The AI-based model achieved a mDice coefficient of 87.11% and an mIoU of 77.68% for the segmentation of critical anatomical structures. The model's automated CAx and CTR measurements showed strong agreement with those of experienced sonographers, with respective intraclass correlation coefficients (ICCs) of 0.83 and 0.81. Bland-Altman analysis further confirmed the high agreement between the model and experienced sonographers.

CONCLUSION

We developed an AI-based model using the nnU-NetV2 architecture for accurate segmentation and automated measurement of critical anatomical structures in fetal four-chamber view images. Our model demonstrated high segmentation accuracy and strong agreement with experienced sonographers in computing clinically relevant parameters. This approach has the potential to improve the efficiency and reliability of prenatal cardiac screening, ultimately contributing to the early detection of congenital heart defects.

The three fetal shunts: A story of wrong eponyms

The fetal circulatory system bypasses the lungs and liver with three shunts. The foramen ovale allows the transfer of the blood from the right to the left atrium, and the ductus arteriosus permits the transfer of the blood from the pulmonary artery to the aorta. The ductus venosus is the continuation of the umbilical vein, allowing a large part of the oxygenated blood from the placenta to join the supradiaphragmatic inferior vena cava, bypassing the fetal liver and directly connecting the right atrium. These structures are named after the physicians who are thought to have discovered them. The foramen ovale and the ductus arteriosus are called the "foramen Botalli" and the "ductus Botalli," after Leonardo Botallo (1530-c. 1587). The ductus venosus is styled "ductus Arantii" after Giulio Cesare Arantius (1530-1589). However, these eponyms have been incorrectly applied as these structures were, in fact, discovered by others earlier. Indeed, the foramen ovale and the ductus arteriosus were described by Galen of Pergamon centuries earlier (c. 129-210 AD). He understood that these structures were peculiar to the fetal heart and that they undergo closure after birth. The ductus venosus was first described by Andreas Vesalius (1514-1564) 3 years before Arantius. Therefore, the current anatomical nomenclature of the fetal cardiac shunts is historically inappropriate.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

DW-Net: A cascaded convolutional neural network for apical four-chamber view segmentation in fetal echocardiography

Fetal echocardiography (FE) is a widely used medical examination for early diagnosis of congenital heart disease (CHD). The apical four-chamber view (A4C) is an important view among early FE images. Accurate segmentation of crucial anatomical structures in the A4C view is a useful and important step for early diagnosis and timely treatment of CHDs. However, it is a challenging task due to several unfavorable factors: (a) artifacts and speckle noise produced by ultrasound imaging. (b) category confusion caused by the similarity of anatomical structures and variations of scanning angles. (c) missing boundaries. In this paper, we propose an end-to-end DW-Net for accurate segmentation of seven important anatomical structures in the A4C view. The network comprises two components: 1) a Dilated Convolutional Chain (DCC) for "gridding issue" reduction, multi-scale contextual information aggregation and accurate localization of cardiac chambers. 2) a W-Net for gaining more precise boundaries and yielding refined segmentation results. Extensive experiments of the proposed method on a dataset of 895 A4C views have demonstrated that DW-Net can achieve good segmentation results, including the Dice Similarity Coefficient (DSC) of 0.827, the Pixel Accuracy (PA) of 0.933, the AUC of 0.990 and it substantially outperformed some well-known segmentation methods. Our work was highly valued by experienced clinicians. The accurate and automatic segmentation of the A4C view using the proposed DW-Net can benefit further extractions of useful clinical indicators in early FE and improve the prenatal diagnostic accuracy and efficiency of CHDs.

Utility of Fetal Cardiac Axis and Cardiac Position Assessment in Predicting Neonatal Respiratory Morbidity in Fetal Congenital Lung Lesions

OBJECTIVES

To assess the diagnostic performance of the fetal cardiac axis (CA) and/or cardiac position (CP) versus the congenital pulmonary malformation volume ratio (CVR) in predicting any and severe neonatal respiratory morbidity in fetal congenital lung lesions.

METHODS

This work was an 11-year retrospective cohort study. The sensitivity, specificity, positive predictive value, and negative predictive value of CA and/or CP assessment in prediction of respiratory morbidity were calculated before 24 weeks' gestation and between 24 and 32 weeks and compared to CVR cutoffs obtained from the literature.

RESULTS

Fifty-three patients were included. CA and/or CP abnormalities were present in 45% and 38% of patients before 24 weeks and between 24 and 32 weeks and were significantly more common in left- versus right-sided lesions (60% versus 17%; P = .003). The sensitivity, specificity, positive predictive value, and negative predictive value of an abnormal CA and/or CP for any and severe respiratory morbidity were 0.67, 0.61, 0.33, and 0.86 and 0.8, 0.58, 0.17, and 0.97 before 24 weeks and 0.75, 0.73, 0.45, and 0.91 and 0.8, 0.67, 0.20, and 0.97 between 24 and 32 weeks, respectively. An abnormal CA and/or CP had higher sensitivity for any respiratory morbidity compared to the CVR at 0.5 and 0.8 cutoffs both before 24 weeks and between 24 and 32 weeks (P < .05).

CONCLUSIONS

An abnormal CA and/or CP before 24 weeks and between 24 and 32 weeks has higher sensitivity for the detection of any respiratory morbidity at birth compared to the CVR at both 0.5 and 0.8 cutoffs. A normal CA and CP have a high negative predictive value for excluding any respiratory morbidity at birth both before 24 weeks and between 24 and 32 weeks.

Z Score Reference Ranges of Fetal Cardiothoracic Diameter Ratio

OBJECTIVE

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

METHOD

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

RESULTS

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

CONCLUSION

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

Correlation Between the Thymic-Thoracic Ratio and Cardiac Axis in Healthy Fetuses

OBJECTIVES

The aim of this study was to assess the correlation between the thymic-thoracic ratio and cardiac axis in healthy fetuses.

METHODS

The fetal thymic-thoracic ratio and cardiac axis were measured in 220 healthy fetuses. The normal ranges of the fetal thymic-thoracic ratio and cardiac axis for each gestational week were established. The Pearson correlation coefficient was calculated to analyze the relationship between the thymic-thoracic ratio and cardiac axis.

RESULTS

The mean fetal thymic-thoracic ratio increased slightly throughout the pregnancy, from 0.33 at 17 weeks' gestation to 0.37 at 37 weeks. No statistically significant correlation was found between the thymic-thoracic ratio and cardiac axis in healthy fetuses.

CONCLUSIONS

In healthy fetuses, the thymus occupies an increasingly larger portion of the upper mediastinum when the pregnancy advances. The cardiac axis is not affected by the thymic-thoracic ratio in healthy fetuses.

24-segment sphericity index: a new technique to evaluate fetal cardiac diastolic shape

OBJECTIVE

Because of parallel circulation in the fetus and the differential effect that various disease states may have on the shape of the right and left ventricles, this study was conducted to evaluate the sphericity index (SI) of 24 transverse segments distributed from the base to the apex of each of the ventricular chambers.

METHODS

Two hundred control fetuses were examined between 20 and 40 weeks of gestation. The displacement of the ventricular endocardium during the cardiac cycle was computed using offline speckle-tracking software. From the ASCII output of the analysis, we analyzed 24 end-diastolic transverse segments, distributed from the base to the apex of each ventricle, as well as the end-diastolic mid-basal-apical length. The SI was computed for each of the 24 segments by dividing the mid-basal-apical length by the transverse length for each segment. Regression analysis was performed against biometric measurements and gestational age according to last menstrual period and ultrasound. Eight fetuses, in which the four-chamber view appeared subjectively to demonstrate chamber disproportion, were evaluated as examples to demonstrate the utility of this technology.

RESULTS

The SI for each segment was independent of gestational age and fetal biometric measurements. The SI of the right ventricle was significantly (P < 0.001) lower than that of the left ventricle for segments 1-18, suggesting that the right ventricle was more globular in shape than was the left ventricle at the base, mid and a portion of the apical segments of the chamber. Fetuses with various cardiac structural abnormalities and abnormal fetal growth had abnormal SI values that reflected either a more globular or a more flattened ventricular chamber.

CONCLUSION

Determination of SI for each of 24 segments of the fetal right and left ventricles provides a comprehensive method to examine the shape of the ventricular chambers. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Common Findings in Late-Gestation Fetal Echocardiography

OBJECTIVES

Fetal echocardiography provides detailed information about cardiac structure and function in utero. Limited information is available regarding normal findings late in pregnancy. We therefore sought to identify and describe common cardiac findings in late gestation.

METHODS

Fetuses with structurally normal hearts were identified in mid gestation within a subset of pregnant women in a prospective study. The atrioventricular valves, right and left atria, aortic isthmus and ductus arteriosus dimensions and flow abnormalities, aneurysm of the septum primum, and presence and grade of tricuspid regurgitation were assessed throughout pregnancy. Linear and logistic regression analyses were used to characterize changes in quantitative and qualitative fetal echocardiographic parameters by gestational age (GA).

RESULTS

Forty fetuses between 24 and 38 weeks' GA were studied. Each had a fetal echocardiographic study completed before and after 34 weeks' gestation, which were compared. Tricuspid-to-mitral valve and right-to-left atrium ratios increased with GA (P < .001). More frequently noted after 34 weeks were tapering of the ductus arteriosus (2.5% versus 32%), prominent aortic isthmus diastolic flow (5% versus 67%), prominent ductus arteriosus diastolic flow (2.5% versus 25%), trivial or mild tricuspid regurgitation (35% versus 80%), and aneurysms of the septum primum (37.5% versus 80%). These findings all increased linearly with GA (P < .001).

CONCLUSIONS

Atrioventricular valve and right/left atrium disproportion, mild ductus arteriosus tapering, prominent aortic isthmus and ductus arteriosus diastolic flow, trivial or mild tricuspid regurgitation, and aneurysms of the septum primum are frequently identified after 34 weeks' GA. Their identification suggests that these fetal echocardiographic findings in isolation are likely normal and are results of the physiologic alterations that occur late in the third trimester.

Diffusion tensor imaging and histology of developing hearts

Diffusion tensor imaging (DTI) has emerged as a promising method for noninvasive quantification of myocardial microstructure. However, the origin and behavior of DTI measurements during myocardial normal development and remodeling remain poorly understood. In this work, conventional and bicompartmental DTI in addition to three-dimensional histological correlation were performed in a sheep model of myocardial development from third trimester to postnatal 5 months of age. Comparing the earliest time points in the third trimester with the postnatal 5 month group, the scalar transverse diffusivities preferentially increased in both left ventricle (LV) and right ventricle (RV): secondary eigenvalues D2 increased by 54% (LV) and 36% (RV), whereas tertiary eigenvalues D3 increased by 85% (LV) and 67% (RV). The longitudinal diffusivity D1 changes were small, which led to a decrease in fractional anisotropy by 41% (LV) and 33% (RV) in 5 month versus fetal hearts. Histological analysis suggested that myocardial development is associated with hyperplasia in the early stages of the third trimester followed by myocyte growth in the later stages up to 5 months of age (increased average myocyte width by 198%, myocyte length by 128%, and decreased nucleus density by 70% between preterm and postnatal 5 month hearts.) In a few histological samples (N = 6), correlations were observed between DTI longitudinal diffusivity and myocyte length (r = 0.86, P < 0.05), and transverse diffusivity and myocyte width (r = 0.96, P < 0.01). Linear regression analysis showed that transverse diffusivities are more affected by changes in myocyte size and nucleus density changes than longitudinal diffusivities, which is consistent with predictions of classical models of diffusion in porous media. Furthermore, primary and secondary DTI eigenvectors during development changed significantly. Collectively, the findings demonstrate a role for DTI to monitor and quantify myocardial development, and potentially cardiac disease. Copyright © 2016 John Wiley & Sons, Ltd.

Severe left diaphragmatic hernia limits size of fetal left heart more than does right diaphragmatic hernia

OBJECTIVES

To assess whether severity of congenital diaphragmatic hernia (CDH) correlates with the degree of left heart hypoplasia and left ventricle (LV) output, and to determine if factors leading to abnormal fetal hemodynamics, such as compression and reduced LV preload, contribute to left heart hypoplasia.

METHODS

This was a retrospective cross-sectional study of fetuses at 16-37 weeks' gestation that were diagnosed with CDH between 2000 and 2010. Lung-to-head ratio (LHR), liver position and side of the hernia were determined from stored ultrasound images. CDH severity was dichotomized based on LHR and liver position. The dimensions of mitral (MV) and aortic (AV) valves and LV were measured, and right and left ventricular outputs were recorded.

RESULTS

In total, 188 fetuses with CDH were included in the study, 171 with left CDH and 17 with right CDH. Fetuses with severe left CDH had a smaller MV (Z = -2.24 ± 1.3 vs -1.33 ± 1.08), AV (Z = -1.39 ± 1.21 vs -0.51 ± 1.05) and LV volume (Z = -4.23 ± -2.71 vs -2.08 ± 3.15) and had lower LV output (26 ± 10% vs 32 ± 10%) than those with mild CDH. MV and AV in fetuses with right CDH (MV, Z = -0.83 ± 1.19 and AV, Z = -0.71 ± 1.07) were larger than those in fetuses with left CDH, but LV outputs were similarly diminished, regardless of hernia side. Severe dextroposition and abnormal liver position were associated independently with smaller left heart, while LHR was not.

CONCLUSION

The severity of left heart hypoplasia correlates with the severity of CDH. Altered fetal hemodynamics, leading to decreased LV output, occurs in both right- and left-sided CDH, but the additional compressive effect on the left heart is seen only when the hernia is left-sided. Improved knowledge of the physiology of this disease may lead to advances in therapy and better risk assessment for use in counseling affected families.

Cardiac axis shift within the cardiac cycle of normal fetuses and fetuses with congenital heart defect

OBJECTIVES

To investigate changes in the cardiac axis (CAx) within the cardiac cycle of normal fetuses and fetuses with congenital heart defects (CHD).

METHODS

This was a retrospective case-control study in which stored videoclips of four-chamber views from 527 prenatal ultrasound examinations performed at 18 + 0 to 36 + 6 weeks of gestation were reviewed. Among the ultrasound scans included, 287 were of normal fetuses (controls) and 240 were of fetuses with CHD. In each case, the CAx was measured at end systole (just before the atrioventricular (AV) valve opened) and at end diastole (just before the AV valve closed). CAx measurements of fetuses with CHD were compared to those of controls.

RESULTS

The mean CAx in the control group was 45.9 ± 8.5° at end systole and 38.3 ± 8.4° at end diastole (P < 0.001), resulting in an average difference of 7.6 ± 3.2°. The mean CAx in fetuses with CHD was 53.4 ± 17.8° at end systole and 47.5 ± 17.3° at end diastole (P < 0.001), resulting in an average difference of 5.9 ± 6.3°. However, in some forms of CHD, such as hypoplastic left heart syndrome and L-transposition of the great arteries, the CAx was greater at end diastole than at end systole, with a difference of more than 5°. In 21.3% of control fetuses, there was a CAx shift within the cardiac cycle of ≥ 10°. Abnormal CAx measured at end systole was strongly associated with CHD.

CONCLUSIONS

Measurement of the CAx at end systole provides values that differ from those when measured at end diastole, in both normal fetuses and those with CHD. We recommend that the CAx be measured at end systole as a greater proportion of fetuses with CHD and fewer normal fetuses have an abnormal CAx at this stage compared to at end diastole. The occurrence of an abnormal CAx and the CAx shift within the fetal cardiac cycle depend on the type of CHD.

[Reconstruction of a digital three-dimensional model of fetal heart]

OBJECTIVE

To explore the methods for constructing the digital three-dimensional model of fetal heart.

METHODS

Original two-dimensional CT image data sets were collected from 4 abortion fetuses with fetal malformations but not heart malformation or chromosomal abnormalities. The three-dimensional fetal heart model was reconstructed using Mimics14.0 software.

RESULTS

In the reconstructed three-dimensional fetal heart, the left atrium, left ventricle, right atrium, right ventricle, the ascending aorta, the main pulmonary and their branches, the superior cava and inferior vena cava were marked with different colors, and these structures could be displayed individually or with other structures. This model also allowed three-dimensional arbitrary scaling, shifting or rotation at any angle, and the diameter of the each vessel could be measured with the software.

CONCLUSION

The fetal heart model can be successfully reconstructed from the CT datasets using three-dimensional reconstruction software to facilitate clinical and anatomical teaching.

Differential and linear insertion of atrioventricular valves: a useful tool?

OBJECTIVE

The differential insertion of the atrioventricular valves is the ultrasonographic representation of the more apical attachment of the tricuspid valve to the septum with respect to the mitral valve. A linear insertion is present when both valves form a linear continuum and has been suggested as a marker for atrioventricular septal defects (AVSDs). The objective of this study was to evaluate the anatomical substratum of differential and linear insertions of the atrioventricular valves in normal fetal hearts and fetal hearts with an AVSD.

METHODS

The extent and position of the fibrous skeleton and attachment of the atrioventricular valves to the septum were studied in histological sections of 17 normal hearts and four hearts with an AVSD from 10 + 0 weeks' gestation to 3 days postpartum with various immunohistochemical tissue markers. In addition, spatiotemporal image correlation (STIC) volumes of 10 normal hearts and STIC volumes of eight hearts with an AVSD at 13 + 6 to 35 + 5 weeks' gestation were examined.

RESULTS

The differential insertion of the atrioventricular valves was visible in normal hearts in the four-chamber plane immediately beneath the aorta, but nearer the diaphragm a linear insertion was found. In hearts with an AVSD, a linear appearance was observed in the four-chamber plane immediately beneath the aorta. Towards the diaphragm, however, first a differential insertion and, more caudally, a linear insertion was found.

CONCLUSIONS

Both differential and linear insertions can be found in normal fetal hearts and fetal hearts with AVSD, depending on the plane in which the four-chamber view is visualized. Therefore, measurement of the differential insertion is likely to be useful only in experienced hands.

Magnetic resonance imaging of fetal heart: anatomical and pathological findings

Congenital heart disease is one of the most frequent prenatal malformation representing an incidence of 5/1000 live births; moreover, it represents the first cause of death in the first year of life. There is a wide range of severity in congenital heart malformations from lesions which require no treatment such as small ventricular septal defects, to lesions which can only be treated with palliative surgery such as hypoplastic left heart syndrome. A good prenatal examination acquires great importance in order to formulate an early diagnosis and improve pregnancy management. Nowadays, echocardiography still represents the gold standard examination for fetal heart disease. However, especially when preliminary ultrasound is inconclusive, fetal MRI is considered as a third-level imaging modality. Preliminary experiences have demonstrated the validity of this reporting a diagnostic accuracy of 79%. Our article aims to outline feasibility of fetal MRI in the anatomic evaluation, the common indication to fetal MRI, its role in the characterization of congenital heart defects, and at last its main limitations.

Fetal heart assessment in the first trimester of pregnancy: influence of crown-rump length and maternal body mass index

OBJECTIVE

To evaluate the influence of the crown-rump length and body mass index on sonographic evaluation of the fetal heart using abdominal and vaginal routes in the first trimester of pregnancy.

METHODS

We conducted a cross-sectional study with 57 pregnant women between 12-14 weeks (CRL< 84 mm). We evaluated the following fetal cardiac plans using the abdominal and vaginal routes: four-chamber view, right ventricle outflow tract, left ventricle outflow tract and aortic arch. We used the B-mode, color Doppler and four-dimensional ultrasonography (spatio-temporal image correlation). To evaluate the influence of crown-rump length and body mass index in the assessment of fetal cardiac planes, we used the t test unpaired.

RESULTS

There were no statistically significant differences in the rates of success and failure between abdominal and vaginal routes in relation to body mass index, however, there was a higher failure rate in vaginal assessment using B mode associated with color Doppler (P<0.01).

CONCLUSION

The crown-rump length and body mass index had no interference in fetal cardiac assessment in the first trimester of pregnancy.

[Embryology of the heart walls]

Although anatomically simple structures, the atrial septum and the ventricular septum have complex embryological origins. Recent findings in molecular biology allowed better comprehension of their formation. As soon as the heart tube is formed, cells migrate from several cardiogenic fields to take part in the septation. Elongation, ballooning, and later inflexion of the heart tube create chamber separating grooves, facing the future septa. The systemic venous tributaries conflate at the venous pole of the heart; it will partially involute while contributing to the atrial septum. The primary atrial septum grows from the atrial roof towards the atrioventricular canal. It fuses there with the atrioventricular cushions, while its upper margin breaks down to form the ostium secundum. Then a deep fold develops from the atrial roof and partly covers the ostium secundum, leaving a flap-like interatrial communication through the oval foramen. It will close at birth. The interventricular septum has three embryological origins. The ventricular septum primum, created during the ballooning process, origins from the primary heart tube. It will form the trabecular septum and the inlet septum. The interventricular ring, surrounding the interventricular foramen, will participate in the inlet septum and also form the atrioventricular conduction axis. The outflow cushions will separate the outflow tract in the aorta and pulmonary artery, and grow to create the outlet septum. After merging with the atrioventricular cushions, they will also be part of the membranous septum.

[Topography of the heart and major mediastinal vessels in the early fetal period of human ontogenesis]

In 176 human fetuses at prenatal weeks 16-23, the quantitative study was performed to evaluate the changes of topography of the hearts chambers, septum and valves, aorta, pulmonary trunk and superior vena cava. Te method of N. I. Pirogov, macro-microscopical dissection and preparation of the histotopographical sections in three mutually perpendicular planes were used. As a result of this study, the data on holotopy, skeletotopy and sintopy of the heart and major mediastinal vessels in the early fetal period of human ontogenesis, were obtained. Tese data may be used as reference parameters during the diagnostic ultrasonographic and magnetic resonance tomographic studies of fetuses and during surgical operations performed on fetuses.

Automated region mask for four-chamber fetal heart biometry

This letter proposes an automated region mask for the detection of cardiac chambers from ultrasonic fetal heart biometry. The fetal biometry consists of two dimensional ultrasonic cine-loop sequences of apical four chamber view of fetal heart, which are comparatively The clinical motion information of individual frame is extracted by keeping a constant frame rate of 25 frames per second (fps). The region mask is designed based on the superimposition of motion information from a set of consecutive frames that belong to one cardiac cycle followed by connected component labelling. The borders and edges of all four chambers are thus recognized leading to formation of binary region mask. Experimental study based on second trimester cine-loop sequences confirms the suitability of the proposed technique for detection of heart chambers.

Magnetic resonance imaging in the normal fetal heart and in congenital heart disease

OBJECTIVE

To evaluate prospectively the feasibility of magnetic resonance imaging (MRI) for assessment of the fetal heart for congenital heart disease (CHD).

METHODS

This was a cross-sectional study, including 66 fetuses with a normal heart and 40 with CHD. The fetal heart was examined on MRI using axial steady-state free precession (SSFP) sequences. Regression analysis was used to investigate the effect on the ability to visualize cardiac anatomy of gestational age at examination, maternal body mass index, presence of fetal cardiac abnormality, fetal movements, fetal lie and twinning. The sensitivity and specificity of detecting cardiac defects were calculated.

RESULTS

The four-chamber view was visualized in 98.1% of fetuses. The sensitivity of detecting a cardiac defect on the four-chamber view was 88% and the specificity 96%. The ability to visualize the left and right outflow tracts was only influenced by the presence of fetal movements: for the left outflow tract 94.4 vs. 50.0% visualization and for the right outflow tract 92.6 vs. 53.8% visualization without and with fetal movements, respectively. The sensitivity of detecting a cardiac defect of the left outflow tract was 63% and the specificity 100%, while sensitivity and specificity were 59 and 97%, respectively, for the right outflow tract.

CONCLUSIONS

Despite the use of SSFP sequences, MRI in the fetal heart remains of limited value. It can only be used as a second-line approach for abnormalities of the four-chamber view suspected at prenatal ultrasound.

Comparison of ex-vivo high-resolution episcopic microscopy with in-vivo four-dimensional high-resolution transvaginal sonography of the first-trimester fetal heart

OBJECTIVE

To compare the capability of three-dimensional (3D) reconstructed images produced by high-resolution episcopic microscopy (HREM) with that of in-vivo four-dimensional high-resolution transvaginal sonography (4D-HRTVS) to discern morphological features of the first-trimester human fetal heart.

METHODS

This was a prospective study of fetal hearts between 9 and 14 weeks' gestation. For ex-vivo 3D analysis, 30 human fetal hearts (at 9 + 0 to 14 + 6 weeks) were retrieved from surgical terminations of pregnancy. The specimens were embedded in resin and episcopic ('block-face') imaging was used to obtain a digital volume dataset (HREM) using 3-micron slicing. 4D-HRTVS was performed in 28 separate pregnancies at 10 + 2 to 14 + 0 weeks using a Voluson E8 ultrasound machine with volumetric transvaginal RIC 6-12-MHz transducers. Heart volumes obtained by both methods were compared to assess their ability to demonstrate first-trimester cardiac morphology. Comparisons were made in the transverse and sagittal planes, and using volume rendering.

RESULTS

All hearts were structurally normal, although abdominal situs was not examined in the isolated hearts that underwent HREM. 4D-HRTVS demonstrated each of the complete five transverse cardiac views in 32-86% of cases. HREM showed four features unique to the first-trimester human heart: prominent atrial appendages, spiral ventricular arrangement, prominent coronary arteries and thickened arterial walls. 4D-HRTVS could demonstrate the first two, but ultrasound resolution was too poor to quantify wall thickness and demonstrate coronary arteries in the 3-5-mm diameter heart.

CONCLUSIONS

4D-HRTVS showed limited morphological features of the first-trimester fetal heart compared with HREM. HREM provides a gold standard of ex-vivo imaging against which developments in ultrasound resolution could be compared.

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.

Use of a high-frequency linear transducer and MTI filtered color flow mapping in the assessment of fetal heart anatomy at the routine 11 to 13 + 6-week scan: a randomized trial

OBJECTIVE

To prospectively assess the contribution of a high-frequency linear transducer and of moving target indicator (MTI) filtered color flow mapping in the visualization of cardiac fetal anatomy at the routine 11 to 13 + 6-week scan.

METHODS

This was a cross-sectional prospective study, including 300 singleton fetuses at 11 to 13 + 6 weeks' gestation. Patients were randomized into four groups and a detailed fetal cardiac examination was conducted transabdominally using either a conventional curvilinear transducer, a conventional curvilinear transducer and MTI filtered color flow mapping, a high-frequency linear transducer or a high-frequency linear transducer and MTI filtered color flow mapping. Regression analysis was used to investigate the effect on the ability to visualize different cardiac structures of the following parameters: gestational age at ultrasound examination; fetal crown-rump length (CRL); maternal body mass index (BMI); transducer-heart distance; the technique used at ultrasound; and the position of the placenta.

RESULTS

The four-chamber view was visualized in 89.0% of fetuses and regression analysis showed this rate was correlated with CRL and the use of MTI filtered color flow mapping during ultrasonography, and inversely correlated with BMI and transducer-heart distance. Use of a conventional curvilinear transducer and MTI filtered color flow mapping allowed visualization of the four-chamber view in 97.3% of fetuses, while this was only possible in 84.0% of fetuses using a high-frequency linear transducer. The left and right outflow tracts were visualized in 62.3 and 57.7% of fetuses, respectively. Regression analysis showed that the ability to visualize the left or the right outflow tract was correlated with the use of MTI filtered color flow mapping during scanning and was inversely correlated with transducer-heart distance. The use of a conventional curvilinear transducer and MTI filtered color flow mapping allowed visualization of the left and right outflow tracts in 96.0 and 97.3% of fetuses, respectively, while this was only possible in 37.3 and 26.7% of fetuses using a high-frequency linear transducer.

CONCLUSIONS

During the routine 11 to 13 + 6-week scan, the use of MTI filtered color flow mapping but not of a high-frequency linear transducer, improves visualization of cardiac anatomy.

[Left-ventricular surface trabeculae of the interventricular septum in the human fetal heart]

Left-ventricular surface of the interventricular septum (IVS) was studied in the heart of 85 human fetuses (at weeks 17-28 of development) formed without congenital defects and minor abnormalities. Two anatomical types of trabeculae (bridge-like and parietal) and their two topographical groups are described: trabeculae of the anterior corner of the left ventricle (LV) and the septal trabeculae. The prevalence of trabeculae in both groups was found to be equal (81-81.2%). No correlation between the numbers of septal trabeculae and the trabeculae of the anterior LV corner was found. While the parietal trabeculae were detected in both groups, the bridge-like type was found only in the anterior LV corner. The number of the bridge-like trabeculae of the anterior LV corner and the septal trabeculae increased from the base to the apex of the heart; this was accompanied by the decrease in the IVS myocardium compactness. Among the first topographical group, there were trabeculae in the shape of skewed cylinders or truncated cones, flattened perpendicularly to their long axis. As a rule, in cone-shaped trabeculae, their broad base was directed towards the IVS. In the second group, the ribbon-shaped trabeculae were prevalent. The data on trabecular width are presented. The formation of the cardiac LV and IVS trabecular pattern in prenatal period is discussed.

Online evaluation of fetal second-trimester four-chamber view images: a comparison of six evaluation methods

OBJECTIVE

To compare six online evaluation methods for auditing routine second-trimester four-chamber view still images.

METHODS

We evaluated three different scoring grids (subjective, five-item score and seven-item score), which were applied with or without access to online help, resulting in a total of six evaluation methods. For the subjective scoring grid, images were rated as excellent, good, fair, poor or very poor. For the five-item score, 1 point was allocated for visualization (vs non-visualization or non-evaluable) of each of: heart crux, atria, ventricles, apex and aorta, yielding a score of 0-5. For the seven-item score, 1 point was allocated for clear (vs unclear) visualization of each of: moderator band at the apex, interventricular septum, atrioventricular valves, non-linear insertion of atrioventricular valves (normal offset), septum primum, aorta and pulmonary vein. Each evaluation method was used via the Internet by three randomly selected reviewers, who evaluated the same set of 80 images. Reviewers were experienced in fetal ultrasound, but were not involved in the design of the study. Interrater agreement was the main outcome.

RESULTS

The five-item scoring grid with online help achieved the best interrater agreement (interrater intraclass correlation coefficient = 0.7).

CONCLUSIONS

Evaluation of the second-trimester sonographic four-chamber view is apparently best achieved with a simple five-item scoring grid.

Measurement of strain and strain rate in embryonic chick heart in vivo using spectral domain optical coherence tomography

The ability to measure in vivo strain and strain rate in embryonic chick heart is one of the key requirements for understanding the mechanisms of cardiac development. Due to its high temporal and spatial resolution as well as its fast imaging capability, optical coherence tomography (OCT) has the potential to reveal the complex myocardial activity in the living chick heart. We describe a method to evaluate the in vivo strain and strain rate of the myocardium through analyzing the periodic variation of the myocardial wall thickness calculated from real time serial OCT images. The results demonstrate that OCT can be a useful tool to describe the biomechanical characteristics of the embryonic heart.

Fetal echocardiography at 11-13 weeks by transabdominal high-frequency ultrasound

OBJECTIVES

To assess the accuracy of fetal echocardiography at 11-13 weeks performed by well-trained obstetricians using a high-frequency linear ultrasound transducer.

METHODS

Fetal echocardiography was performed by obstetricians immediately before chorionic villus sampling for fetal karyotyping at 11-13 weeks. Digital videoclips of the examination stored by the obstetrician were reviewed offline by a specialist fetal cardiologist.

RESULTS

The obstetrician suspected 95 (95%) of the 100 cardiac defects identified by the fetal cardiologist and made the correct diagnosis in 84 (84%) of these cases. In 54 fetuses, the defect was classified as major and in 46 it was minor. In 767 (86.6%) cases, the heart was normal and in 19 (2.1%) the views were inadequate for assessment of normality or abnormality. A subsequent second-trimester scan in the normal group identified major cardiac defects in four cases. Therefore, the first-trimester scan by the obstetricians and cardiologists identified 54 (93.1%) of the 58 major cardiac defects.

CONCLUSIONS

A well-trained obstetrician using high-resolution ultrasound equipment can assess the fetal heart at 11-13 weeks with a high degree of accuracy.

Reliability of the first-trimester cardiac scan by ultrasound-trained obstetricians with high-frequency transabdominal probes in fetuses with increased nuchal translucency

OBJECTIVE

To examine prospectively the reliability of ultrasound-trained obstetricians performing a first-trimester fetal cardiac scan with high-frequency transabdominal probes, by confirming normal or abnormal heart anatomy, in pregnancies referred for increased nuchal translucency thickness (NT).

METHODS

Trained obstetric operators assessed the fetal heart in 133 fetuses with increased NT (> 95th centile) at 11-14 weeks of gestation. A high-frequency transabdominal probe was used to confirm or refute normal cardiac anatomy rather than to establish a specific diagnosis. Following this preliminary screening by the ultrasound-trained obstetrician, specialized fetal echocardiographers rescanned the fetal heart in order to confirm the accuracy of the obstetric operators' findings and to establish a diagnosis in abnormal cases. Fetal cardiologists repeated the examinations at 20 and 32 weeks of pregnancy. Postnatal follow-up lasted 2 years. Twelve fetuses with normal karyotype and normal anatomy were lost to follow-up.

RESULTS

A total of 121 fetuses with increased NT between 11 and 14 weeks' gestation were studied. Congenital heart disease (CHD) was detected in 20/121 (16.5%) fetuses. In addition, there were three with mild ventricular disproportion, the right ventricle being larger than the left, considered as a minor non-specific cardiac abnormality. CHD was associated with chromosomal anomalies in 12/20 (60%) cases. Among the 121 fetuses, there was agreement between ultrasound-trained obstetricians and fetal cardiologists in 116 (95.9%) of the cases, and the ultrasound-trained obstetricians correctly identified 18 cases with major cardiac defects. However, there was disagreement in five cases: two with small ventricular septal defects and three with ventricular disproportion.

CONCLUSIONS

Our results provide evidence that obstetricians, trained to study the heart in the second trimester, can also differentiate reliably between normal and abnormal heart findings in the first trimester, when using a high-frequency transabdominal ultrasound probe.

Significance and outcome of left heart hypoplasia in fetal congenital diaphragmatic hernia

OBJECTIVE

In patients with a left-sided congenital diaphragmatic hernia (CDH), the left ventricle (LV) is often compressed and smaller than normal. The objective of this study was to investigate whether small left heart dimensions prenatally normalize after birth in patients with CDH, or whether prenatal indices of left heart size and flow predict postnatal outcome.

METHODS

Clinical and echocardiographic data were reviewed for patients diagnosed with left-sided CDH prenatally. Cardiac dimensions and flows were compared with normative data. Among liveborn patients, pre- and postnatal Z-scores of left heart structures were compared, and associations between prenatal indices and outcome were assessed.

RESULTS

Of 125 patients diagnosed prenatally with CDH, 111 had a left-sided defect. Of these, 85 were liveborn, including 20 with congenital heart disease. Gestational age-adjusted dimensions of fetal left heart structures, including aortic valve diameter, mitral valve (MV) diameter, LV long-axis, LV short-axis and LV volume, were all smaller than normal (P < 0.001). On average, the LV contributed 33 +/- 8% of combined ventricular output, lower than the normal 40-50%. Z-scores of left heart structures increased from the prenatal echocardiogram to the postnatal study, with average changes ranging from 0.56 +/- 1.68 (aortic valve) to 1.39 +/- 1.85 (LV volume). Among liveborn patients, there was no association between prenatal left heart Z-scores and postnatal survival.

CONCLUSIONS

Hypoplasia of and reduced flow through the left heart are common among fetuses with CDH. After birth and CDH repair, left heart dimensions generally normalize, with adequate size to support a biventricular circulation, even when there is very low flow through the left heart in mid- and late-gestation.

Prenatal screening for major congenital heart disease: superiority of outflow tracts over the 4-chamber view

OBJECTIVE

The purpose of this study was to determine the relative importance of the 4-chamber view (4CV) compared with the outflow tract views (OFTVs) in prenatal screening for major congenital heart disease (CHD).

METHODS

We prospectively evaluated 200 consecutive infants undergoing cardiac surgery at our institution for major CHD. By reviewing the infants' medical records and conducting bedside interviews with their parents or guardians, we evaluated detection rates both prenatally and postnatally (before and after discharge to home), and we noted any prenatally identifiable risk factors for CHD. For each infant, we determined whether the 4CV or OFTVs would be expected to have been normal or abnormal on routine midgestation screening fetal sonography.

RESULTS

A prenatal diagnosis of CHD was made in 65 infants (33%): 30 of 124 low-risk pregnancies (24%) and 35 of 76 high-risk pregnancies (46%). An abnormal screening midgestation 4CV would have been expected in up to 63% of the infants, whereas abnormal midgestation OFTVs would have been expected in up to 91% of the infants. Thus, the potential sensitivity for detecting major CHD was higher with the OFTVs than with the 4CV (91% versus 63%; P < .001). Moreover, the OFTVs were more sensitive than the 4CV for detecting ductal-dependent forms of CHD. Diagnosis after discharge to home occurred in 39 of 135 postnatal diagnoses (29%), including many cases of isolated outflow tract abnormalities requiring early invasive intervention.

CONCLUSIONS

Cases of major neonatal CHD with OFTV abnormalities predominate over cases with 4CV abnormalities, particularly among those forms of CHD requiring early invasive intervention.

Feasibility of automated 3-dimensional fetal cardiac screening in routine ultrasound practice

OBJECTIVE

The purpose of this study was to prospectively assess the clinical feasibility of an automated 3-dimensional (3D) software tool for extended basic cardiac screening in routine ultrasound practice.

METHODS

During the 2-month study period, all gravidas fitting our inclusion criteria were consecutively included. Cardiac 3D volumes were acquired within the time slot allocated for the usual 2-dimensional fetal examination. All volumes were assessed on their quality, based on display of the 4-chamber view, and on the ability to sufficiently display diagnostic cardiac planes (left ventricular outflow tract [LVOT], right ventricle outflow tract [RVOT], and stomach location) with Sonography-Based Volume Computer-Aided Diagnosis software (SonoVCAD; GE Healthcare, Milwaukee, WI).

RESULTS

Volume acquisition was successful in 107 of 126 cases (85%). For each sonographer, more than 70% of the acquired cardiac volumes were of high or sufficient quality. Separately analyzed, diagnostic planes of the LVOT, RVOT, and stomach location were visible in 62.1%, 81.6%, and 92.2%, respectively. An extended basic fetal cardiac examination based on retrieval of all diagnostic cardiac planes from a single volume using SonoVCAD could be performed in 46.6% of the cases.

CONCLUSIONS

This study shows that cardiac volume acquisition can be incorporated in a routine ultrasound screening program without much difficulty. However, currently, SonoVCAD software still lacks the consistency to be clinically feasible for cardiac screening purposes. Further advances in ultrasound technology and familiarization with 3D ultrasound might improve its performance.

Fetal anatomic evaluation in the overweight and obese gravida

OBJECTIVES

To evaluate the rate of completion of anatomic surveys of fetuses in overweight and obese gravid patients as compared with normal controls.

METHODS

This was a retrospective review of anatomic ultrasound scans performed between 2004 and 2007. Women were stratified by prepregnancy body mass index (BMI) into normal weight (BMI, 18.5-24.9 kg/m(2)), overweight (BMI, 25.0-29.9 kg/m(2)) and obese Class I (BMI, 30.0-34.9 kg/m(2)), Class II (BMI, 35.0-39.9 kg/m(2)) and Class III (BMI >or= 40.0 kg/m(2)) groups. Rates of completion of basic and comprehensive scans, gestational age at completion and number of scans required were compared.

RESULTS

For the 7140 patients included, completion rates for both the basic (normal weight, n = 2253 (79%); overweight, n = 1771 (76%); obese Class I, n = 767 (72%), Class II, n = 323 (61%) and Class III, n = 171 (49%)) and comprehensive (normal weight, n = 1234 (43%); overweight, n = 930 (40%); obese Class I, n = 404 (38%), Class II, n = 215 (41%) and Class III, n = 108 (31%)) surveys decreased significantly with increasing BMI (P < 0.00001). For surveys completed, the mean number of scans required was significantly higher for obese patients (basic: normal weight 1.3 vs. obese Class III 1.9; comprehensive: normal weight 1.7 vs. obese Class III, 2.2)(P < 0.00001). The overall completion rate improved at each gestational week, but was best between 20 and 23 weeks for obese patients.

CONCLUSIONS

As maternal BMI increases, the rate of completion of anatomic surveys decreases and the number of scans required increases. Delaying the initial survey until 20 weeks' gestation may improve the capacity to complete the examination in a single visit. It should be noted that these results represent completion rates at a tertiary referral center, and therefore may not reflect community experience.

[Importance of "Guidelines for performing fetal cardiac scan" in prenatal screening for fetal congenital heart disease]

OBJECTIVE

To investigate the application of "Guidelines for performing fetal cardiac scan", issued by the International Society of Ultrasound in Obstetrics and Gynecology in 2006, in prenatal screening of fetal congenital heart disease (CHD).

METHOD

Totally, 5000 singleton pregnancies presented at the Maternal-Fetal Medical Center of the Affiliated Drum Tower Hospital of Nanjing University Medical School from September 2006 to July 2007, for prenatal screening were included in this study, with the median maternal age of 28 (range, 18 approximately 48) and the median gestation of 27 (range, 18 approximately 40) weeks. Ultrasound screenings were performed on each fetal heart according to "Guidelines for performing fetal cardiac scan" via the four-chamber and outflow tracts & three-vessel views and fetal echocardiographies were further conducted for suspected cases. Once congenital heart disease was confirmed, amniocentesis or cordocentesis was suggested for fetal karyotyping for ongoing pregnancies and autopsy was performed when the pregnancy was terminated after formal consent. Born babies were followed up at 2 approximately 6 months of age using echocardiography.

RESULT

The four-chamber views were successfully obtained in 97.64% (4882/5000) of all the pregnancies, among which the left ventricular and right ventricular outflow tracts and three-vessel views were obtained in 87.69% (4281/4882), 82.51% (4028/4882) and 96.29% (4701/4882), respectively. Higher successful rate was found in the second trimester than the third trimester in obtaining the standard views (P < 0.05). Finally, 73 (1.50%) among the 4882 cases were diagnosed as CHD. Fifty of them were diagnosed prenatally (24 cases in the second trimester and 26 cases in the third trimester) and 23 were missed and 1 misdiagnosed by prenatal ultrasound. Eighteen cases were found with extracardiac malformations. Autopsy was performed in 19 CHD which diagnosed prenatally, and all autopsy reports were consistent with ultrasound foundings. Twelve babies received postnatal echocardiography among which 11 were unanimous, and 1 baby diagnosed as tricuspid insufficiency prenatally was confirmed normal after birth. Abnormal karyotype was found in 7 out of the 23 who had karyotyping performed. Altogether, 28 cases were diagnosed by four chamber view only and 50 cases by combining other views, giving the sensitivity, specificity, false negative rate and false positive rate of 69% (50/73), 99.98% (4808/4809), 0.48% (23/4831) and 2% (1/51), respectively.

CONCLUSION

The "Guidelines for performing fetal cardiac scan" is practical and easy to abide by. The optimal time for fetal cardiac examination is at 18 approximately 27 weeks of gestation. Four-chamber view together with the outflow tracts and three-vessel views examination can detect 69% of CHD in utero.

[Trabeculae and intertrabecular spaces of the heart interventricular septum: anatomical structure and development]

The review presents traditional and new concepts on the development of the trabeculae carneae and intertrabecular spaces (ITS) in the heart ventricles. Myocardial trabeculation preceeds the ventricular septation and at the same time underlies the formation of the interventricular septum. Trabeculae carneae seem to generate the contractile force of the embryonic myocardium. The differences between right and left ventricular trabecular patterns are conditioned by the changes of intracardiac blood flow during the prenatal period. Anatomical characteristics of the right inlet and outlet relief are reviewed. Special emphasis is given to the correlations of the terms "septomarginal trabeculation" and "moderator band". It is noticed that ITS anatomy is still insufficiently studied. The necessity to develop the anatomical criteria of normal intracardiac structures is accentuated.

Nomograms of the fetal heart between 16 and 39 weeks of gestation

OBJECTIVE

To establish the normal fetal cardiac measurement from 16 to 39 weeks' gestation in Thai fetuses.

MATERIAL AND METHOD

Four hundred and eighty normal singleton pregnant women were recruited into the present study. The sonographic measurements were obtained from axial scans at the level of the four-chamber view.

RESULTS

The regression model for cardiac circumference (CC), thoracic circumference (TC), thickness of left ventricular wall during diastole (LVW), diameter of left ventricle during diastole (LVD) and systole (LVS) and thickness of interventricular septum during diastole (IVS) were best fit by allowing a polynomial for gestational age. The cardiothoracic ratio (CTR) and shortening fraction of left ventricle (SFLV) were not statistically different with advancing gestation.

CONCLUSION

The normal values of fetal CC, TC, CTR, LVW, LVD, LVS, IVS and SFLV during gestation were established These data could serve as a standard to investigate cardiac change in pregnancies with fetuses at risk.

The relationship between fetal inferior vena cava diameter pulse and flow velocity waveforms in normal and compromised pregnancies

BACKGROUND

The circulation is characteristically assessed by pressure and flow.

OBJECTIVE

To evaluate the hemodynamic significance of fetal inferior vena cava (IVC) flow velocity waveform (FVW) indices in relation to the diameter pulse waveform (DPW).

STUDY DESIGN

Doppler ultrasound and a phase locked loop echo tracking system were used to measure the FVW and the DPW in the fetal IVC, respectively.

SUBJECTS

We studied 98 normal fetuses (20 to 40 weeks) and 65 compromised fetuses with increased umbilical placental resistance.

RESULTS

The DPW consisted of four waves (A, X, V, and Y waves). Three components (systolic flow; S, diastolic flow; D, reverse flow; R during atrial contraction) were identified in the FVW. The FVW indices were examined in relation to the X descent {(A - X) / A%} of the DPW. The compromised group was divided into three subgroups by the X descent. In 15 fetuses the waveform was normal. In 32 there was a high pulsatile pattern with deep descent form the A crest to X trough. In 18 the X descent was shallow and the pulsatility appeared reduced. The high and low pulsatile patterns were associated with an increase in the S/D ratio and the R/S ratio, respectively.

CONCLUSION

In fetal compromise the high pulsatility DPW may result from increased end-diastolic pressure in response to the increase in ventricular afterload caused by the placental vessel obliteration. The S/D ratio of the FVW may reflect the increasing cardiac afterload. The low pulsatility DPW may indicate depressed myocardial function and output. In the FVW, the R/S ratio may be associated with this.

[Topographic anatomy of human thoracic organs in the early fetal period]

The purpose of the present investigation was to evaluate the holotopy, skeletotopy and sintopy of human heart, trachea and esophagus in the early fetal period. The quantitative evaluation of the topography of these organs was given as a result of study of 100 human fetuses aged 16-24 week with the modification of N.I. Pirogov method and using the multiplane histotopographical sections in the multidimensional coordinate system. The horizontal sections were selected, that could be proposed as the standard ones. he results of this investigation may be recommended for the improvement of the ultrasonographic and magnetic resonance tomographic diagnosis and fetal surgery development.

Primary noncompaction of the ventricular myocardium from the morphogenetic standpoint

This review compiles the current knowledge of normal and abnormal myocardial morphogenesis to facilitate an unambiguous diagnosis of primary myocardial noncompaction. During the early stages of development, the formation of trabeculae with the resulting increase in myocardial surface is a adaptation of the rapidly growing heart to improve nourishment by exchange diffusion from the cardiac lumen. Once the coronary vasculature has developed, the switch to cardiac nutrient supply through active circulation from the subepicardial space is paralleled by gradual compaction of the myocardial trabeculae. This results in a decrease of the inner, trabeculated myocardial layer with a parallel increase in thickness of the outer, compact myocardial layer. Similar to the direction of coronary arterial development, this process proceeds from the epicardium toward the endocardium and from the base of the heart to the apex. Based on developmental data, congenital myocardial noncompaction represents a failure of normal embryonic myocardial maturation. The time of arrest of this process will determine the extension of myocardial noncompaction within the ventricle. Whereas disturbances of myocardial microcirculation are frequent in these hearts, direct communications between the myocardial cavity and the coronary arteries (sinusoids) do not belong to this morphogenetic entity.

Changes in fetal cardiac geometry with gestation: implications for 3- and 4-dimensional fetal echocardiography

OBJECTIVE

Three- and 4-dimensional fetal echocardiography can be performed using novel algorithms. However, these algorithms assume that the spatial relationships among cardiac chambers and great vessels are constant throughout gestation. The objective of this study was to determine whether changes in fetal cardiac geometry occur during gestation.

METHODS

A cross-sectional study was conducted by reviewing 3- and 4-dimensional volume data sets from healthy fetuses obtained between 12 and 41 weeks of gestation. Volume data sets were examined using commercially available software. Parameters measured included angles between: (1) the ductal arch and fetal thoracic aorta; (2) the ductal arch and aortic arch; and (3) the left outflow tract and main pulmonary artery, as seen in the short axis of the heart. The mean angle from the left outflow tract to the short axis was calculated. Nonparametric statistics were used for analysis.

RESULTS

Eighty-five fetuses were included in the study. The angle between the ductal arch and the fetal thoracic aorta decreased with gestational age (Spearman rho coefficient: -0.39; P < .001). In contrast, the angle between the ductal arch and aortic arch, and the mean angle between the left outflow tract and the short axis of the heart increased with gestational age (Spearman rho coefficients: 0.45 and 0.40, respectively; P < .001).

CONCLUSIONS

(1) Changes in fetal cardiac geometry were shown with advancing gestational age. (2) Proposed algorithms for the examination of the fetal heart with 3-dimensional ultrasonography may need to be adapted to optimize visualization of the standard planes before 26 weeks of gestation.

Automated sonography: defining the spatial relationship of standard diagnostic fetal cardiac planes in the second trimester of pregnancy

OBJECTIVE

This study defines the spatial relationship of the diagnostic planes of the fetal heart to the 4-chamber view plane in the second trimester of pregnancy as a first step in the automation process.

METHODS

Three-dimensional static volumes of the fetal chest were acquired at the level of the 4-chamber view on 75 fetuses between 18 and 23 weeks' gestation. The spatial relationship of the diagnostic cardiac planes to the 4-chamber view plane were determined for each gestational week by using rotations along the x-, y-, and z-axes and a parallel slide (millimeters) when applicable.

RESULTS

The 5-chamber view (cardiac 1 plane) was best obtained by an initial parallel slide of the reference plane (plane A) toward the fetal head followed by a rotation along the y-axis. The right ventricular outflow tract (cardiac 2) and the abdominal circumference (cardiac 3) planes were best obtained by a parallel slide only: toward the fetal head in cardiac 2 and toward the fetal abdomen in cardiac 3.

CONCLUSIONS

This study shows the spatial relationship of fetal cardiac diagnostic planes to the 4-chamber view plane in the second trimester of pregnancy in 3-dimensional volumes. Testing the clinical applicability of automated software based on these formulas is the next step.

Fetal echocardiography at the time of the nuchal translucency scan

OBJECTIVE

The fetal heart is not studied routinely in the first trimester because of technical and time limitations. Our aim was to assess the feasibility of performing a fetal cardiac study in pregnancies referred for nuchal translucency (NT) screening, using high-frequency linear transabdominal transducers with a specific ultrasound preset.

METHODS

A single trained operator assessed the fetal heart in pregnancies with a fetal crown-rump length (CRL) of 60-84 mm that had been referred for NT screening. A 15- or 6-MHz transabdominal linear transducer with a specific preset suitable mainly for color-flow mapping was used to confirm or refute normal cardiac anatomy rather than to establish a specific diagnosis. Fetuses having an increased risk for congenital heart disease were referred to a tertiary center for a further examination within 1 week. This group consisted of all fetuses with NT > 95(th) centile and those in which a family history or the initial heart scan increased the risk.

RESULTS

A total of 608 fetuses with a median CRL of 65 mm was examined between 2003 and 2005. A cardiac scan was performed successfully in 456 (75%) using a 15-MHz linear transducer alone, and the additional use of a 6-MHz transducer allowed diagnostic images to be obtained in a further 152. Normal cardiac anatomy was assessed confidently within 10 min in 517/608 (85%) pregnancies; in 85 (14%) a longer time was needed and six patients were rescheduled within 2 weeks because of non-diagnostic images at the initial scan. In 571/608 (94%) the risk for congenital heart disease (CHD) was not increased and the heart was considered normal at initial echocardiography; this was confirmed by later scans and at postnatal follow-up. In 37/608 (6%) fetuses the risk for CHD was increased (35 for NT > 95(th) centile and two for family history). In this group normal heart anatomy was described in 34 fetuses and confirmed by subsequent specialist echocardiography. Cardiac defects were suspected in three fetuses (all with increased NT) and confirmed by a fetal cardiologist in each case.

CONCLUSIONS

A trained operator can perform a fetal heart study during the NT screening test using transabdominal high-resolution transducers in an acceptable length of time.

Location and variability of epicardiac ganglia in human fetuses

The aim of the study was to determine the morphology of epicardiac ganglia in human fetuses at different stages of their development as these ganglia are considered to be of a pivotal clinical importance. Twenty-one fetal hearts were investigated applying a technique of histochemistry for acetylcholinesterase to visualize the epicardiac neural ganglionated plexus with its subsequent stereoscopic examination on total organs. In all of the examined fetuses, epicardiac neural plexus with numerous ganglia was well recognizable and could be clearly differentiated into seven ganglionated subplexuses, topography and structural organization of which were typical for hearts of adult human. The largest ganglion number comprising 77% of all counted ganglia was identified on the dorsal atrial surface. Fetal epicardiac plexus in gestation period of 15-40 weeks contained 929 +/- 62 ganglia, but ganglion amount did vary substantially from heart to heart. In conclusion, this study implies that the human fetal epicardiac ganglia occupy their definitive location already at gestation period from 15 weeks and their number as well as distribution on heart surface presumably is not age dependent.

Assessment of the intraobserver variability in the measurement of fetal cardiothoracic ratio using ellipse and diameter methods

OBJECTIVE

To assess the variability of fetal heart and thoracic area and circumference measurements using the ellipse and diameter methods at different gestational ages.

DESIGN

This was a prospective cross-sectional study of 200 singleton pregnancies, with no apparent fetal abnormalities. The gestational age ranged between 19 and 42 weeks. At each examination, two transverse frames of the fetal chest at the level of the four-chamber view during diastole were obtained. For each frame, the area and the circumference of the heart and thorax were obtained by the ellipse and diameter methods. In the diameter method, cardiac and thoracic areas and circumferences were derived from the measured anteroposterior and transverse diameters. All measurements were made by the same observer.

RESULTS

For the same method, intraobserver variability was good. Coefficient of variation for all measurements varied between 3-11%. The ellipse method tended to give larger measurements than did the diameter method, the absolute difference increasing with fetal age. The mean ellipse/diameter ratio was 1.10, 1.04, 1.05 and 1.02 for heart area, thorax area, heart circumference and thorax circumference, respectively. In most cases, intraobserver variability of the thorax measurements was independent of gestational age. In contrast, there was a greater variability of heart measurements with increasing gestational age.

CONCLUSIONS

Both the ellipse and diameter methods of measuring cardiothoracic ratio are clinically useful and fairly reproducible at certain gestations, but are not interchangeable as the ellipse method overestimates measurements compared to the diameter method. The less reproducible measurement of heart size in later gestation should be taken into account when assessing cardiothoracic ratios.

Ontogenetic development of the helical heart: concepts and facts

The structural and functional organization of the ventricular myocardial mass is a controversial matter that cannot be resolved by anatomical studies alone. Therefore, other approaches such as investigations of the ontogenetic development of the ventricular myocardium might help to resolve controversies about its structural and functional organization. It has recently been proposed that the spatial orientation of Torrent-Guasp's ventricular myocardial band model (basal and apical loops) might be the mature morphological correlate of twists and torsions of the embryonic heart loop. In the present contribution, the suggestions made in this concept were analyzed in the light of currently known facts about the development of the embryonic heart. It was found that some of the suggestions made in this concept do not correspond to embryological facts, whereas other suggestions could neither be disproved nor confirmed on the basis of our current knowledge on heart development. The answer to the question as to which of the various models of myocardial fibre organization fits best with the ontogenesis of the myocardial mass awaits future studies. The myocardial units of Torrent-Guasp's myocardial band model are said to have a functional rather than a morphological personality. Future studies on the ontogenetic development of the myocardium, therefore, should comprise not only anatomical analyses of dead specimens but should additionally comprise high resolution in vivo analyses of the development of the spatio-temporal contraction patterns of embryonic and fetal hearts.