The role of fetal echocardiography in genetic sonography

Trends in the prenatal diagnosis of trisomy 21 show younger maternal age and shift in the distribution of congenital heart disease over a 20-year period

Prenatal testing has changed greatly over the past two decades, which may affect the diagnosis of congenital heart disease (CHD) in Down syndrome. The present study aimed to analyze changes in the prevalence and distribution of CHD diagnosed via ultrasonography and fetopathology in 462 fetuses with trisomy 21 between two consecutive 10-year periods (1999-2018), as well as the associations between CHDs, ultrasound markers, and extracardiac malformations. Overall, the frequency of cardiovascular malformations in trisomy 21 was 27.7 and 26.5%, and ultrasound identified 70 and 62% of CHDs during these periods. A profound increase in first-trimester ultrasound findings and associated anomalies with CHDs (ventricular septal defect, Tetralogy of Fallot) since 2009 were observed. Second-trimester nonstructural heart abnormalities were associated with ultrasound anomalies (74%) and major extracardiac malformations (42.9%). During both study periods, mothers carrying fetuses with CHD were significantly younger than those without CHD (p = 0.038, p = 0.009, respectively). Comparing the two 10-year periods, there were no changes in the prevalence and detection of CHDs. Trend analysis revealed that, although the frequency of CHD remained stable, the diagnostic spectrum had shifted between the study periods. Detection of nonstructural heart abnormalities necessitates detailed follow-up for cardiac/extracardiac malformations and chromosomal disorders.

4D fetal echocardiography-An update

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

Cardio-STIC (spatio-temporal image correlation) as genetic ultrasound of fetal Down syndrome

OBJECTIVE

To evaluate efficacy of cardio-STIC in detection of fetal Down syndrome.

METHODS

Cardio-STIC volume datasets (VDS) were prospectively collected from women during 16-22 weeks, consisting of 40 VDS acquired from fetuses with Down syndrome and 400 VDS from normal fetuses. All VDS were blindly analyzed.

RESULTS

Between both groups, most dimensions were comparable but the right-sided dimensions were significantly greater in fetuses with Down syndrome. Interestingly, shortening fraction was also significantly higher in affected fetuses. Right-to-left disproportion and shortening fraction were used as cardiac markers as well as other eight structural markers to predict fetal Down syndrome. Tricuspid regurgitation had highest sensitivity (30%); followed by VSD (27.5%), right-to-left disproportion (20.0%), and echogenic intra-cardiac foci (EIF; 17.5%). If the test was considered positive in case of the presence of any cardiac marker, cardio-STIC had a detection rate of 72.5% and false-positive rate of 19.5%. Likelihood ratio of each marker for modifying priori risk was also provided.

CONCLUSION

Cardio-STIC as genetic ultrasound for Down syndrome had a detection rate of about 70% and false-positive rate 20%. Cardio-STIC analysis can be helpful in estimation of fetal risk for Down syndrome and counseling when the prenatal diagnosis of the syndrome is made.

Influence of second-trimester ultrasound markers for Down syndrome in pregnant women of advanced maternal age

The objective of the present study was to evaluate the influence of second-trimester ultrasound markers on the incidence of Down syndrome among pregnant women of advanced maternal age. This was a retrospective cohort study on 889 singleton pregnancies between the 14th and 30th weeks, with maternal age ≥ 35 years, which would undergo genetic amniocentesis. The second-trimester ultrasound assessed the following markers: increased nuchal fold thickness, cardiac hyperechogenic focus, mild ventriculomegaly, choroid plexus cysts, uni- or bilateral renal pyelectasis, intestinal hyperechogenicity, single umbilical artery, short femur and humerus length, hand/foot alterations, structural fetal malformation, and congenital heart disease. To investigate differences between the groups with and without markers, nonparametric tests consisting of the chi-square test or Fisher's exact test were used. Moreover, odds ratios with their respective 95% confidence intervals were calculated. Out of the 889 pregnant women, 131 (17.3%) presented markers and 758 (82.7%) did not present markers on the second-trimester ultrasound. Increased nuchal fold (P < 0.001) and structural malformation (P < 0.001) were the markers most associated with Down syndrome. The presence of one marker increased the relative risk 10.5-fold, while the presence of two or more markers increased the risk 13.5-fold. The presence of markers on the second-trimester ultrasound, especially thickened nuchal fold and structural malformation, increased the risk of Down syndrome among pregnant women with advanced maternal age.

Nuchal fold thickness, nasal bone absence or hypoplasia, ductus venosus reversed flow and tricuspid valve regurgitation in screening for trisomies 21, 18 and 13 in the early second trimester

OBJECTIVE

To investigate the performance of nuchal fold thickness, nasal bone hypoplasia, reversed flow in the ductus venosus and tricuspid valve regurgitation in the prediction of fetal aneuploidies in the early second trimester.

METHODS

This was a prospective study of 870 fetuses at 14 + 0 to 17 + 6 weeks of gestation, performed from 2005 to 2007. In all cases we assessed classical structural anomalies, second-trimester markers of aneuploidy including nuchal fold thickness and nasal bone length, as well as ductus venosus blood flow pattern and tricuspid valve regurgitation.

RESULTS

The study group included 37 fetuses with trisomy 21, eight with trisomy 18 and four with trisomy 13. Nasal bone hypoplasia was the single most sensitive parameter to identify fetuses with trisomy 21. Independent from maternal age, screening by assessment of nuchal fold and nasal bone identified 64.9% of cases with trisomy 21 and 66.7% of cases with trisomy 18/13 (false-positive rate (FPR), 5.8%). By including ductus venosus and tricuspid flow evaluation, the detection rate increased to 75.7% for trisomy 21 and 83.3% for trisomy 18/13 (FPR, 10.8%). Identification of fetuses with structural abnormalities combined with assessment of all four markers under investigation raised the detection rate of trisomy 21 to 83.9% and that of trisomy 18/13 to 100%. The sensitivity of classical second-trimester markers was 62.2% for trisomy 21 and 70.6% for other autosomal aneuploidies (FPR, 11.3%).

CONCLUSION

The combination of assessment of nuchal fold thickness, nasal bone hypoplasia, ductus venosus reversed flow and tricuspid regurgitation in the early second trimester is associated with a higher detection rate of autosomal trisomies compared with classical second-trimester marker screening.

Indications for fetal echocardiography high referral, low yield?

An excellent imaging tool in the prenatal diagnosis and ongoing evaluation of congenital heart defects, fetal echocardiography is indicated in a selected population at increased risk compared with the general population. For certain "soft markers" of fetal congenital heart defects, ambiguity in the indications for fetal echo may result in a high referral rate, but low yield of congenital heart disease. Here, we critically examine 4 conditions, 2 maternal and 2 fetal: maternal gestational diabetes, advanced maternal age, isolated echogenic focus, and single umbilical artery. This critical review reveals that more prospective population-based studies with higher power and minimal bias need to be performed to establish the absolute risk of congenital heart defects in a selected population compared with that of the general population. Nonetheless, our analysis indicates that the absolute risk of congenital heart defects associated with each of these markers is low.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians

LEARNING OBJECTIVES

After completion of this article, the reader should be able to define which patients should be referred for fetal echocardiography based on known risks, distinguish between relative and absolute risks for fetal congenital heart disease, and summarize fetal anomaly risks for women with altered glucose metabolism.

Utility of fetal echocardiography after normal cardiac imaging findings on detailed fetal anatomic ultrasonography

OBJECTIVE

The purpose of this study was to assess the utility of fetal echocardiography (FE) after normal fetal cardiac imaging findings during detailed fetal anatomic ultrasonography (FAU).

METHODS

We conducted a retrospective cohort review of obstetric ultrasonographic studies from November 2001 through July 2005. We identified women with a singleton gestation with increased risk for congenital heart disease who received FAU performed by a maternal-fetal medicine specialist at 16 to 20 weeks' gestation with subsequent FE. These records were compared with newborn outcomes.

RESULTS

Of 789 pregnancies that had FAU and FE, 481 had satisfactory cardiac imaging. Of those, only 1 fetus had abnormal FE findings. After delivery, 4 of the 480 neonates with normal FAU and FE findings had a diagnosis of a heart defect.

CONCLUSIONS

Fetal echocardiography does not substantially increase the detection rate of major cardiac anomalies after normal findings on detailed FAU performed by a maternal-fetal medicine specialist.

Prenatal course of isolated muscular ventricular septal defects diagnosed only by color Doppler sonography: single-institution experience

OBJECTIVE

Counseling patients with an isolated ventricular septal defect (i-VSD) is clinically important because with high-resolution ultrasound equipment, more small muscular VSDs are now being diagnosed. The prevalence of these lesions is not yet completely described, and the frequency with which muscular VSDs resolve in utero has also not been extensively reported.

METHODS

We investigated the perinatal course of isolated muscular VSDs diagnosed only on color Doppler examinations and followed between January 1, 2005, and December 31, 2006. A complete evaluation of the fetal heart was performed by gray scale, spectral Doppler, and color Doppler examinations.

RESULTS

We performed a total of 2583 fetal echocardiographic examinations on 2410 fetuses during 2318 pregnancies. The study group included 78 twin gestations (3.4%) and 7 triplet gestations (0.3%). There were 16 fetuses with an i-VSD (6.6/1000 fetuses) within the study group. The mean gestational age +/- SD at diagnosis was 23.5 +/- 4.3 weeks. Two of the i-VSDs (12.5%) spontaneously resolved prenatally. One fetus with an i-VSD had trisomy 21 and also had increased nuchal translucency in the first trimester. One i-VSD was diagnosed among 22 fetuses with trisomy 21 examined during the study period.

CONCLUSIONS

An i-VSD is a common congenital heart defect. Prenatal resolution of i-VSDs is less frequent than reported in the literature. A larger cohort is needed to provide a better risk estimate for aneuploidy in the presence of an i-VSD.

Literature Review and suggested protocol for managing ultrasound soft markers for Down syndrome: Thickened nuchal fold, echogenic bowel, shortened femur, shortened humerus, pyelectasis and absent or hypoplastic nasal bone

Mid-trimester soft markers have been linked with Down syndrome and other aneuploidies. There are many other prenatal screening tests available with better detection rates for Down syndrome than the mid-trimester ultrasound. Many patients confronted with the diagnosis of a soft marker become anxious and may request a diagnostic test (amniocentesis) despite the associated risk of miscarriage. This is also despite the fact that most fetuses with an isolated soft marker are chromosomally normal. The management of a pregnancy with a soft marker must therefore be planned in a manner designed to minimize patient anxiety. Likelihood ratios can be used to modify a patient's 'prior risk' (based on age or prior screening tests) and create a new risk. This calculation may help identify a subset of patients suitable for further investigation. It has been proposed that 'negative' likelihood ratios can be used to reduce a patient's risk if no soft marker is found at a mid-trimester ultrasound. There remain concerns about this approach and further research is required before this approach enters common practice. The published work surrounding the management of thickened nuchal fold, echogenic bowel, shortened femur, shortened humerus, pyelectasis (renal pelvis dilatation) and hypoplastic nasal bone is reviewed. Each soft marker has different associations and individual management plans for each of these soft markers are presented. Although isolated single umbilical artery is not usually considered a soft marker of aneuploidy, a management plan for this common finding is also included.

The neonate with congenital heart disease: what the cardiac surgeon needs to know from the neonatologist and the cardiologist

To plan and accomplish a successful operation for a neonate with congenital heart disease, the cardiac surgeon requires a complete anatomic description of the cardiovascular malformation. For optimum outcome, this information must be supplemented by a complete report of the prenatal and postnatal course of the newborn as well as by a thorough summary of any noncardiac congenital or acquired abnormalities. In the most favorable circumstance, the neonate arrives in the operating room completely diagnosed, fully resuscitated, well nourished, and with appropriate monitoring devices in place. Unique perioperative considerations attach to each cardiac anomaly and are briefly reviewed, and the importance of continuity of care for the patient and family is emphasized.

Three-dimensional and four-dimensional fetal echocardiography: a new frontier

PURPOSE OF REVIEW

One of the difficulties of conventional two-dimensional cardiac imaging is the inability to examine fetal cardiac anatomy from multiple angle planes. Three-dimensional and four-dimensional ultrasound allows the fetal examiner to more accurately accomplish this task. Currently, multiple disciplines may be involved in the examination of the fetal heart (pediatric cardiologists, obstetricians, maternal-fetal medicine specialists, and radiologists). The three-dimensional and four-dimensional imaging equipment used by these specialty physicians varies greatly. The purpose of this communication is to review techniques using three-dimensional and four-dimensional imaging that the pediatric cardiologist may not be exposed to in the clinical environment, however, in consulting with colleagues needs to have an understanding of these imaging modalities.

RECENT FINDINGS

The reconstruction of cardiac structures using this technology allows the examiner to view cardiac anatomy in a manner that was limited by previous two-dimensional imaging. Volume datasets are obtained in the three-dimensional static mode (no cardiac motion) or using four-dimensional - the three-dimensional heart is observed contracting during one or multiple cardiac cycles. Therefore, the fourth dimension is time. Using either three-dimensional or four-dimensional technology datasets are acquired, followed by image reconstruction. The image reconstruction enables the examiner to evaluate a two-dimensional image using multiple views, evaluate intracardiac anatomy at different depth planes, and recreate casts of blood flow of the chambers and great vessels.

SUMMARY

This new technology has enhanced the ability of the examiner to identify normal and complex fetal heart anatomy during the early second to the late third trimesters of pregnancy.

Aberrant right subclavian artery as a new cardiac sign in second- and third-trimester fetuses with Down syndrome

OBJECTIVE

The right subclavian artery arises normally as the first vessel from the brachiocephalic artery of the aortic arch. An aberrant right subclavian artery arises as a separate vessel from the aortic isthmus and crosses to the right, behind the trachea. This variant is present in <1% of the normal population; however, in subjects with Down syndrome, an incidence between 19% and 36% was reported. The purpose of this study was to assess the possibility of the detection of an aberrant right subclavian artery in fetuses with Down syndrome.

STUDY DESIGN

Fourteen consecutive fetuses with prenatally detected Down syndrome were examined between 18 and 33 weeks of gestation. The presence of an aberrant right subclavian artery was determined by visualization of the transverse 3-vessel trachea view of the upper thorax with color Doppler ultrasonography.

RESULTS

The right subclavian artery was visualized in 100% of fetuses (14/14) with Down syndrome. An aberrant right subclavian artery was identified in 35.7% of trisomy 21 fetuses (5/14). In 1 fetus, the aberrant right subclavian artery was the only abnormal ultrasound finding. In 3 fetuses, an aberrant right subclavian artery was associated with an intracardiac echogenic focus plus additional extracardiac markers. In the fourth fetus, an aberrant right subclavian artery was associated with an atrioventricular septal defect. All 9 fetuses with Down syndrome with a normal origin of the right subclavian artery had additional cardiac and/or extracardiac abnormalities. In 12 cases, pregnancy was terminated; 2 fetuses were live born.

CONCLUSION

This preliminary study suggests that the in utero identification of an aberrant right subclavian artery may be a new ultrasound marker to be found in fetuses with Down syndrome. Further studies are required to assess the incidence of aberrant right subclavian artery in normal fetuses.

Latest advances and topics in fetal echocardiography

PURPOSE OF REVIEW

Fetal diagnosis and the supporting specialties of perinatology, neonatology, and surgery have made rapid strides in the last decade. Numerous centers are focusing on this multifaceted niche area as the medical field realizes its vast promise and potential. The authors review some of the major advancements in thought and practice in the field of fetal echocardiography while attempting to give a less detailed overview for the less involved perinatologist.

RECENT FINDINGS

First trimester fetal echocardiography has been an area of recent interest as transducer technology improves. As a result, optimum timing of first and subsequent scans and the population profile they are to be applied to have become an issue that begs consensus. Three-dimensional and four-dimensional fetal echocardiography have also received a boost for the same reasons, and both are being studied for feasibility and accuracy. Fetal tissue Doppler and spectral Doppler imaging are potential areas for exploration; the early steps have been taken. Awareness of associated ultrasound markers, such as exaggerated nuchal translucency, as clues to the presence of congenital heart disease is important, even if controversial.

SUMMARY

The issue of missed prenatal diagnosis is disturbing, especially when it arises against a background of tremendous skill and technologic support. Strategies to minimize mistakes in this critical aspect need to be agreed on by the involved teams and put in place in a multidisciplinary manner if they are to have an important impact.