Reference Ranges for the Size of the Fetal Cardiac Outflow Tracts From 13 to 36 Weeks Gestation: A Single-Center Study of Over 7000 Cases

Association of Prenatally Diagnosed Isolated Single Left Superior Vena Cava and Postnatal Development of Coarctation of the Aorta

To report the prevalence of coarctation of the aorta (CoA) in fetuses with single left superior vena cava (SL-SVC) and to evaluate changes in echocardiographic measurements. Additionally, to report the prevalence of associated malformations. Retrospective observational study of fetuses diagnosed with SL-SVC between 2012 and 2021 at a tertiary fetal cardiology unit. In fetuses without intracardiac abnormalities, Z-scores of the ventricles, great arteries, and Doppler flow patterns are reported. We identified 47 fetuses with SL-SVC of which 8/47 (17%) had abnormal intracardiac anatomy. One fetus was lost to follow-up. Of those with normal intracardiac anatomy and postnatal follow-up (38), karyotype abnormalities were confirmed in 2/38 (5%) and ECA in 8/38 (21%). 33/38 were live-born. None developed CoA postnatally. Paired analysis of Z-scores between early and late scans of 24 fetuses showed that diameters of the right heart structures and Doppler flows of tricuspid valve increased significantly during pregnancy, while the left heart structures and flow patterns did not change. The median risk of CoA did not change between the early and the late scan. We did not observe CoA in this cohort. A degree of ventricular asymmetry was present, but this was due to right heart dominance rather than hypoplasia of left heart structures. This likely reflects redistribution of blood and does not appear to confer increased risk of CoA. Predictive models of the postnatal development of CoA which set the dimensions of right and left heart structures in relation might not be applicable in this situation.

Fetal Echocardiographic Z Score Pilot Project: Study Design and Impact of Gestational Age and Variable Type on Reproducibility of Measurements Within and Across Investigators

BACKGROUND

Fetal echocardiography is widely available, but normative data are not robust. In this pilot study, the authors evaluated (1) the feasibility of prespecified measurements in a normal fetal echocardiogram to inform study design and (2) measurement variability to assign thresholds of clinical significance and guide analyses in larger fetal echocardiographic Z score initiatives.

METHODS

Images from predefined gestational age groups (16-20, >20-24, >24-28, and >28-32 weeks) were retrospectively analyzed. Fetal echocardiography expert raters attended online group training and then independently analyzed 73 fetal studies (18 per age group) in a fully crossed design of 53 variables; each observer repeated measures for 12 fetuses. Kruskal-Wallis tests were used to compare measurements across centers and age groups. Coefficients of variation (CoVs) were calculated at the subject level for each measurement as the ratio of SD to mean. Intraclass correlation coefficients were used to show inter- and intrarater reliabilities. Cohen's d > 0.8 was used to define clinically important differences. Measurements were plotted against gestational age, biparietal diameter, and femur length.

RESULTS

Expert raters completed each set of measurements in a mean of 23 ± 9 min/fetus. Missingness ranged from 0% to 29%. CoVs were similar across age groups for all variables (P < .05) except ductus arteriosus mean velocity and left ventricular ejection time, which were both higher at older gestational age. CoVs were >15% for right ventricular systolic and diastolic widths despite fair to good repeatability (intraclass correlation coefficient > 0.5); ductal velocities and two-dimensional measures, left ventricular short-axis dimensions, and isovolumic times all had high CoVs and high interobserver variability despite good to excellent intraobserver agreement (intraclass correlation coefficient > 0.6). CoVs did not improve when ratios (e.g., tricuspid/mitral annulus) were used instead of linear measurements. Overall, 27 variables had acceptable inter- and intraobserver repeatability, while 14 had excessive variability between readers despite good intraobserver agreement.

CONCLUSIONS

There is considerable variability in fetal echocardiographic quantification in clinical practice that may affect the design of multicenter fetal echocardiographic Z score studies, and not all measurements may be feasible for standard normalization. As missingness was substantial, a prospective design will be needed. Data from this pilot study may aid in the calculation of sample sizes and inform thresholds for distinguishing clinically significant from statistically significant effects.

Incremental value of myocardial deformation in predicting postnatal coarctation of the aorta: establishment of a novel diagnostic model

BACKGROUND

Prenatal detection of coarctation of the aorta (CoA) still suffers from high false-positive and false-negative rates. The objective of this study was to develop a novel model to improve the diagnostic accuracy of fetal CoA.

METHODS

A retrospective study was conducted in 122 fetuses with suspected CoA who also had postnatal follow-ups. Fetuses with confirmed diagnosis of CoA after birth were defined as CoA group, and Non-CoA group were those false-positives. Conventional fetal echocardiographic measurements, including great arterial dimensions and flow characteristics were obtained. Left ventricular (LV) functional parameters were determined using two-dimensional speckle tracking echocardiography. A novel multi-parametric diagnostic model, including gestational age (GA) at diagnosis, aortic isthmus (AOI) Z-score and LV longitudinal strain (LVLS), was developed by univariate and multivariate logistic regression analyses. The model was validated prospectively by a validation cohort of 48 fetuses.

RESULTS

CoA was confirmed in 62/122 (50.8%) cases after birth. Fetuses with postnatal CoA were diagnosed significantly earlier than false-positives (median (interquartile range), 24.5 (23.3-26.4) vs 27.8 (24.5-30.4) weeks; P < .001). The Z-scores of aortic dimensions (aortic valve annulus, ascending aorta, transverse aortic arch and AOI) were significantly smaller (all P < .001), while the Z-scores of pulmonary dimensions (pulmonary valve annulus and main pulmonary artery) were significantly greater (all P < .05), in cases of confirmed CoA than false-positives. Compared with Non-CoA group, CoA group displayed lower LV ejection fraction (P = .005), LV fractional area change (P < .001) and LVLS (P < .001). A multivariate logistic regression model incorporating GA (odds ratio (OR): 0.74, 95% confidence interval (CI): 0.60-0.88; P = .001), AOI Z-score (OR: 0.20, 95% CI: 0.08-0.41; P < .001) and LVLS (OR: 1.79, 95% CI: 1.41-2.42; P < .001) was established to diagnose CoA more accurately (Akaike information criterion: 81.77, C-statistics: 0.945). The performance of this model was confirmed prospectively in the validation cohort.

CONCLUSIONS

In fetuses with suspected CoA, speckle tracking analysis of LVLS may have an incremental value in predicting postnatal CoA. Our diagnostic model, including GA, AOI Z-score and LVLS, may provide a good tool for the stratification of the risk in fetal CoA and contribute to patient-specific perinatal management.

Intrauterine Valvuloplasty in Severe Aortic Stenosis-A Ten Years Single Center Experience

Objective: To assess the course and outcome of fetal aortic valvuloplasty (FAV) in fetuses with severe aortic stenosis (SAS) in a single center. Methods: All fetuses with a prenatal diagnosis of SAS with subsequent FAV were retrospectively collected in one tertiary center for fetal medicine over a period of 10 years. In the study, period fetuses with SAS were considered suitable for FAV in the presence of markedly elevated left ventricular pressures (maximum velocity of mitral regurgitation (MR Vmax) >250 cm/s and/or maximum velocity of aortic stenosis (AS Vmax) >250 cm/s), retrograde flow in the transverse aortic arch and a left ventricular length Z-score >−1. Results: In the study period 29 fetuses with AS were treated with 38 FAV. If reinterventions are included 82.7% of fetuses received a technically successful FAV. Procedure related death occurred in three (10.3%) cases, spontaneous fetal death in 2 (6.9%), and termination of pregnancy was performed in 3 cases (10.3%). Among the 21 live births (72.4%), four died in infancy. Among the remaining survivors, 8/17 (47.1%) had a biventricular outcome at the age of one year, 8/17 (47.1%) were univentricular and one infant (5.9%) is biventricular at the age of eight months. Fetuses with biventricular outcome had significantly greater left ventricular (LV) length Z-scores (p = 0.031), and lower tricuspid to mitral valve (TV/MV) ratios (p = 0.003). Conclusions: FAV has a high technical success rate and a low rate of procedure related mortality if performed in experienced hands. The success rate of biventricular circulation at the age of one year is moderate and seems to depend rather on the center’s experience and postnatal surgical strategies than solely on prenatal selection criteria. In the absence of randomized controlled trials, FAV remains an experimental intervention.

Fetal echocardiographic markers to differentiate between a right and double aortic arch

OBJECTIVES

To describe the fetal echocardiographic features of a double aortic arch (DAA) and secondly, to assess the performance of these features to differentiate between a right aortic arch with left duct (RAA-LD) in a blinded cohort of vascular rings.

METHODS

Review of records to identify surgically confirmed cases of DAA diagnosed prenatally from 2014 to 2018 (cohort-A). Prenatal echocardiograms were reviewed and the segments of the aortic arches anterior and posterior to the trachea, aortic isthmuses and the presence/absence of the Z-sign were described. The utility of these markers were assessed in a separate cohort (B) of fetuses with surgically confirmed cases of DAA or RAA-LD.

RESULTS

Cohort-A comprised 34 cases with DAA; there was a dominant RAA in 32/34 (94%) and balanced left aortic arch (LAA) and RAA in two cases. The proximal LAA was seen in 29/34 (85%), distal LAA in 15/34 (44%) and the LAA aortic isthmus in 4/34 (12%). The "Z" configuration was present in 29/34 (85%) cases. The most predictive marker for DAA in cohort-B was the Z-sign (sensitivity: 100%, specificity: 81%).

CONCLUSION

The "Z" sign is a useful differentiator between RAA-LD and DAA. The absence of visualization of the left aortic isthmus does not preclude the presence of a DAA.

Deficient Myocardial Organization and Pathological Fibrosis in Fetal Aortic Stenosis-Association of Prenatal Ultrasound with Postmortem Histology

In fetal aortic stenosis (AS), it remains challenging to predict left ventricular development over the course of pregnancy. Myocardial organization, differentiation and fibrosis could be potential biomarkers relevant for biventricular outcome. We present four cases of fetal AS with varying degrees of severity and associate myocardial deformation on fetal ultrasound with postmortem histopathological characteristics. During routine fetal echocardiography, speckle tracking recordings of the cardiac four-chamber view were performed to assess myocardial strain as parameter for myocardial deformation. After pregnancy termination, postmortem cardiac specimens were examined using immunohistochemical labeling (IHC) of key markers for myocardial organization, differentiation and fibrosis and compared to normal fetal hearts. Two cases with critical AS presented extremely decreased left ventricular (LV) strain on fetal ultrasound. IHC showed overt endocardial fibro-elastosis, which correlated with pathological fibrosis patterns in the myocardium and extremely disturbed cardiomyocyte organization. The LV in severe AS showed mildly reduced myocardial strain and less severe disorganization of the cardiomyocytes. In conclusion, the degree of reduction in myocardial deformation corresponded with high extent to the amount of pathological fibrosis patterns and cardiomyocyte disorganization. Myocardial deformation on fetal ultrasound seems to hold promise as a potential biomarker for left ventricular structural damage in AS.

Reference Ranges for Pulsed-Wave Doppler of the Fetal Cardiac Inflow and Outflow Tracts from 13 to 36 Weeks' Gestation

BACKGROUND

Doppler assessment of ventricular filling and outflow tract velocities is an integral part of fetal echocardiography, to assess diastolic function, systolic function, and outflow tract obstruction. There is a paucity of prospective data from a large sample of normal fetuses in the published literature. The authors report reference ranges for pulsed-wave Doppler flow of the mitral valve, tricuspid valve, aortic valve, and pulmonary valve, as well as heart rate, in a large number of fetuses prospectively examined at a single tertiary fetal cardiology center.

METHODS

The study population comprised 7,885 fetuses at 13 to 36 weeks' gestation with no detectable abnormalities from pregnancies resulting in normal live births. Prospective pulsed-wave Doppler blood flow measurements were taken of the mitral, tricuspid, aortic, and pulmonary valves. The fetal heart rate was recorded at the time of each assessment. Regression analysis, with polynomial terms to assess for linear and nonlinear contributors, was used to establish the relationship between each measurement and gestational age.

RESULTS

The measurement for each cardiac Doppler measurement was expressed as a Z score (difference between observed and expected values divided by the fitted SD corrected for gestational age) and percentile. Analysis included calculation of gestation-specific SDs. Regression equations are provided for the cardiac inflow and outflow tracts.

CONCLUSIONS

This study establishes reference ranges for fetal cardiac Doppler measurements and heart rate between 13 to 36 weeks' gestation that may be useful in clinical practice.

Development of the Z-score for the measurement of myocardial thickness by two-dimensional echocardiography in normal fetuses

BACKGROUND

In the current literature, there is a tendency to describe normal values of echocardiographic measurements by means of the Z-score. In fetal cardiology, these Z-score equations are still being established. Measurement of myocardial thickness is an important assessment, especially in fetuses of diabetic mothers, because of the risk of developing myocardial hypertrophy secondary to elevated maternal blood glucose levels.

OBJECTIVE

To determine the percentiles and to develop the Z-score equations of right and left ventricular lateral walls and interventricular septum measurements using two-dimensional echocardiography in normal fetuses between 24 and 34 weeks of gestation.

METHODS

This is a prospective cross-sectional study that was performed in single fetuses with normal heart from nondiabetic pregnant women. Measurements of the lateral walls of the right and left ventricles and the interventricular septum were made.

RESULTS

Eight hundred and seventy three pregnant women were included. We determined the percentiles of the measurements for each gestational age. The Z-score equation was developed for each of the measurements: right ventricular lateral wall measurement [RVLW = x-(-1 + 0.109 * GA)/0.4], left ventricle lateral wall measurement [LVLW = x-(-1.366 + 0.12 * GA)/0.43], and interventricular septum, both at the four-chamber view [IVS_4ch = (x-(-1.113 + 0.107 * GA)/0.4] and at the left ventricular outflow tract plane [IVS_LVOT = (x-(-0.581 + 0.084 * GA)/0.35].

CONCLUSION

The present study allowed the demonstration of the percentiles and the Z-score equations for each of the measurements studied.

Impact of prospective measurement of outflow tracts in prediction of coarctation of the aorta

OBJECTIVES

Prenatal diagnosis of coarctation of the aorta (CoA) is associated with reduced mortality and morbidity, however, accurate prenatal prediction remains challenging. To date, studies have used retrospective measurements of the outflow tracts to evaluate their potential to predict CoA. Our primary objective was to evaluate prospectively acquired measurements of the outflow tracts in fetuses with prenatally suspected CoA. A secondary aim was to report the postnatal prevalence of bicuspid aortic valve in this cohort.

METHODS

Pregnancies with suspicion of isolated CoA and with a minimum of 6 months' postnatal follow-up available were identified from the cardiac database of a tertiary fetal cardiology center in the UK, between January 2002 and December 2017. Measurement of the aortic valve, pulmonary valve, distal transverse aortic arch (DTAA) and arterial duct (AD) diameters were undertaken routinely in fetuses with suspected CoA during the study period. Z-scores were computed using published reference ranges based on > 7000 fetuses from our own unit.

RESULTS

Of 149 pregnancies with prenatally suspected CoA included in the study, CoA was confirmed within 6 months after birth in 77/149 (51.7%) cases. DTAA diameter Z-score and the Z-score of second-trimester DTAA/AD diameter ratio were smaller in fetuses with postnatally confirmed CoA than those in false-positive cases (-2.8 vs -1.9; P = 0.039 and -3.13 vs -2.61; P = 0.005, respectively). Multiple regression analysis demonstrated that the Z-scores of DTAA and AD diameters were the only significant predictors of postnatal CoA (P = 0.001). Bicuspid aortic valve was identified in 30% of the false-positive cases.

CONCLUSIONS

Measurement of DTAA and AD diameter Z-scores can be used to ascertain risk for postnatal CoA in a selected cohort. The high incidence of bicuspid aortic valve in false-positive cases merits further study with respect to both etiology and longer-term significance. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Fetal whole heart blood flow imaging using 4D cine MRI

Prenatal detection of congenital heart disease facilitates the opportunity for potentially life-saving care immediately after the baby is born. Echocardiography is routinely used for screening of morphological malformations, but functional measurements of blood flow are scarcely used in fetal echocardiography due to technical assumptions and issues of reliability. Magnetic resonance imaging (MRI) is readily used for quantification of abnormal blood flow in adult hearts, however, existing in utero approaches are compromised by spontaneous fetal motion. Here, we present and validate a novel method of MRI velocity-encoding combined with a motion-robust reconstruction framework for four-dimensional visualization and quantification of blood flow in the human fetal heart and major vessels. We demonstrate simultaneous 4D visualization of the anatomy and circulation, which we use to quantify flow rates through various major vessels. The framework introduced here could enable new clinical opportunities for assessment of the fetal cardiovascular system in both health and disease.

Reference ranges and Z-scores for fetal cardiac measurements from two-dimensional echocardiography in Asian population

Currently available fetal echocardiographic reference values are derived mainly from North American and European population studies, and there is a lack of reference z-score for fetal echocardiographic measurement in Asian populations. The aim of this study was to establish normal ranges of echocardiographic measurements and z-scores in healthy Asian fetuses. A total of 575 healthy pregnant Taiwanese with an estimated gestational age from 14 to 38 weeks were enrolled voluntarily for this observational study. Standard two-dimensional echocardiography was performed to obtain measurements of the cardiac chambers and great arteries of the developing fetuses. In contrast to past studies, our sample was more evenly distributed for estimated gestational age (p<0.001). We present percentile graphs for 13 fetal echocardiographic measurements from the knowledge of estimated gestational age, biparietal distance, head circumference, abdominal circumference, and femur length. Most cardiac structures and developmental markers had linear models as the best-fitting, except for transverse aortic isthmus by estimated gestational age and transverse ductus arteriosus by femur length. Our findings indicate that estimated gestational age was generally the best model for fetal heart development, while head circumferences could be used as an optimal developmental marker to predict left atrium, right atrium, right ventricle, pulmonary annulus, and ductus arteriosus. Lastly, we developed nomograms for each of the 13 fetal heart measurements by each developmental markers. This is the first study providing echocardiographic reference ranges and nomograms for Asian fetuses. Computing z-scores from nomograms helps in standardizing comparisons and adds additional prognostic information to the diagnosis of congenital heart disease.

Transposition of the great arteries: Fetal pulmonary valve growth and postoperative neo-aortic root dilatation

Objectives

Documentation of semilunar valve growth in fetal transposition of the great arteries (TGA) and the relationship between neo‐aortic root (NAoR) dilatation, a cause for postoperative reinterventions after the arterial switch operation (ASO), and pulmonary valve (PV) annulus dimensions prenatally.

Methods

This retrospective multicenter observational study included TGA fetuses suitable for ASO. Semilunar valve annuli pre‐ASO and NAoR diameters (post‐ASO) were measured. Trends in annulus diameters were analyzed using a linear mixed‐effects model and compared with normal values. Prenatal semilunar valve Z‐scores were correlated with NAoR diameters post‐ASO.

Results

We included 137 TGA fetuses (35.8% with significant ventricular septal defects [VSDs]). One hundred twenty‐one underwent ASO. Fetal TGA‐PV diameters were significantly larger than control aortic valve (AoV) and PV annuli from 23 and 27 weeks, respectively, especially when a VSD was present. Fetal TGA‐AoV annuli were significantly larger than control AoV and PV annuli from 26 and 30 weeks, respectively.

Z‐scores of fetal TGA‐PV and NAoR diameter at last follow‐up correlated significantly (P < .001 at 26‐30 wk).

Conclusion

Fetal TGA semilunar valve annuli are larger than control annuli, especially when there is a significant VSD. Factors besides postoperative hemodynamics, including fetal anatomy, PV Z‐score, prenatal flow, connective tissue properties, and genetics, may influence the risk for late reintervention in these fetuses.