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

Aberrant subclavian artery origin in tetralogy of Fallot with pulmonary stenosis is associated with chromosomal or genetic abnormality

We determined the relationship between aortic arch anatomy in tetralogy of Fallot with pulmonary stenosis and chromosomal or genetic abnormality, by performing analysis of 257 consecutive patients undergoing surgical repair from January, 2003 to March, 2011. Chromosomal or genetic abnormality was identified in 49 of the 257 (19%) patients. These included trisomy 21 (n = 14); chromosome 22q11.2 deletion (n = 16); other chromosomal abnormalities (n = 9); CHARGE (n = 2); Pierre Robin (n = 2); and Kabuki, Alagille, Holt-Oram, Kaufman McKusick, Goldenhar, and PHACE (n = 1 each). Aortic anatomy was classified as left arch with normal branching, right arch with mirror image branching, left arch with aberrant right subclavian artery, or right arch with aberrant left subclavian artery. Associated syndromes occurred in 33 of 203 (16%) patients with left arch and normal branching (odds ratio 1); three of 36 (8%) patients with right arch and mirror image branching (odds ratio 0.4, 95% confidence interval 0.1-1.6); seven of eight (88%) patients with left arch and aberrant right subclavian artery (odds ratio 36, 95% confidence interval 4-302); and six of 10 (60%) patients with right arch and aberrant left subclavian artery (odds ratio 8, 95% confidence interval 2-26). Syndromes were present in 13 of 18 (72%) patients with either right or left aberrant subclavian artery (odds ratio 15, 95% confidence interval 4-45). Syndromes in patients with an aberrant subclavian artery included trisomy 21 (n = 4); chromosome 22q11.2 deletion (n = 5); and Holt-Oram, PHACE, CHARGE, and chromosome 18p deletion (n = 1 each). Aberrant right or left subclavian artery in tetralogy of Fallot with pulmonary stenosis is associated with an increased incidence of chromosomal or genetic abnormality, whereas right aortic arch with mirror image branching is not. The assessment of aortic arch anatomy at prenatal diagnosis can assist counselling.

Imaging findings in Down syndrome

Down syndrome, or trisomy 21, is the most common chromosomal anomaly and is characterized by intellectual disability and a typical facies. People with Down syndrome can have abnormalities of multiple organ systems. Cardiac and respiratory system involvement is the most common cause of morbidity and mortality, although every organ system can be affected. Patients may present prenatally with findings on screening sonography. If the diagnosis is not made prenatally, it is apparent at birth because of the characteristic facial features and musculoskeletal findings. Children with Down syndrome present to the radiology department at various ages depending on the severity of the specific finding. The purpose of this paper is to review the most common antenatal and postnatal imaging findings of Down syndrome as they manifest throughout the body.

Simplified first-trimester fetal cardiac screening (four chamber view and ventricular outflow tracts) in a low-risk population

OBJECTIVES

Our aim was to assess the accuracy of a simplified fetal cardiac study, inclusive of four-chamber view (4CV) and ventricular outflow tracts, performed during the 11-14 week screening by well-trained obstetricians to detect congenital heart diseases (CHDs).

METHODS

A transabdominal ultrasound was performed on 4820 singleton pregnant women at 11-14 weeks to visualize the visceral site, the 4CV, and the outflow tracts. Neonatal outcomes were recorded 6 and 12 months after birth.

RESULTS

Among the 4820 patients reviewed, 790 were excluded because of loss at prenatal or postnatal follow-up (649 cases), or inability to obtain adequate first-trimester sonographic cardiac evaluation (141 cases). Among the 4030 included cases, 32 CHD cases were detected (20 major and 12 minor); 18 of the major (90%) and five of the minor (42%) were detected or suspected in the first trimester, one major and six minor in the second trimester, and one major and one minor only after birth.

CONCLUSIONS

A simplified protocol is an effective tool to screen for CHD at 11-14 weeks.

[Aberrant right subclavian artery (arteria lusoria) and the risk for trisomy 21. Retrospective study of 11,479 fetopathological examinations]

OBJECTIVE

The aberrant right subclavian artery is a malformation of the aortic arch present at less than 2 % of the individuals in the general population. This incidence is higher in trisomy 21, making it possible use the aberrant right subclavian artery as a prenatal marker of trisomy 21.

MATERIAL AND METHODS

This work, which relates to a series of 11,479 consecutive fetal autopsies aims to measure the force of association between the aberrant right subclavian artery and trisomy 21, to confront our results with the sonographic series previously published and to contribute to assess the place that can have this sign in the echographic screening and the fetopathologic diagnosis of trisomy 21.

RESULTS

The isolated presence of an aberrant right subclavian artery does not represent an argument sufficient for the indication of a karyotype. But the detection of this anomaly must make pay a special attention in search of other associated signs.

CONCLUSION

On the results of this study, the aberrant right subclavian artery has to be considered as a part of the spectrum not only of trisomy 21, but also of many other congenital syndromes.

The fetal three-vessel and tracheal view revisited

The routine use of four-chamber screening of the fetal heart was pioneered in the early 1980s and has been shown to detect reliably mainly univentricular hearts in the fetus. Many conotruncal anomalies and ductal-dependent lesions may, however, not be detected with the four-chamber view alone and additional planes are needed. The three-vessel and tracheal (3VT) view is a transverse plane in the upper mediastinum demonstrating simultaneously the course and the connection of both the aortic and ductal arches, their relationship to the trachea and the visualization of the superior vena cava. The purpose of the article is to review the two-dimensional anatomy of this plane and the contribution of colour Doppler and to present a checklist to be achieved on screening ultrasound. Typical suspicions include the detection of abnormal vessel number, abnormal vessel size, abnormal course and alignment and abnormal colour Doppler pattern. Anomalies such as pulmonary and aortic stenosis and atresia, aortic coarctation, interrupted arch, tetralogy of Fallot, common arterial trunk, transposition of the great arteries, right aortic arch, double aortic arch, aberrant right subclavian artery, left superior vena cava are some of the anomalies showing an abnormal 3VT image. Recent studies on the comprehensive evaluation of the 3VT view and adjacent planes have shown the potential of visualizing the thymus and the left brachiocephalic vein during fetal echocardiography and in detecting additional rare conditions. National and international societies are increasingly recommending the use of this plane during routine ultrasound in order to improve prenatal detection rates of critical cardiac defects.

Fetal left brachiocephalic vein in normal and abnormal conditions

OBJECTIVES

To establish values of fetal left brachiocephalic vein (LBCV) dimensions during normal pregnancy and determine whether routine assessment of the LBCV may help in identifying fetuses with congenital abnormalities of this vessel.

METHODS

Fetal LBCV was assessed prospectively during ultrasound examinations in 431 normal singleton pregnancies. The visualization rate of the transverse view of the upper fetal chest at the level of drainage of the LBCV into the superior vena cava (SVC) by two-dimensional (2D) and 2D plus color Doppler ultrasound was evaluated. Reference ranges of LBCV diameter during non-complicated pregnancies were established. Interobserver and intraobserver measurement variability was analyzed. In addition, a retrospective review of the hospital medical records of 91 pregnancies with fetuses diagnosed with LBCV abnormalities was performed.

RESULTS

Sonographic assessment of the fetal LBCV was consistently achieved in the second and third trimesters and in some fetuses in the first trimester of pregnancy. In normal fetuses LBCV diameter increased significantly throughout pregnancy, with a mean value of 0.7 mm at 11 weeks and 4.9 mm at term. Dilation of the fetal LBCV was noted in five cases of intracranial arteriovenous malformation and six cases of supracardiac type total anomalous pulmonary venous connection. Abnormal course of the LBCV was noted in 12 fetuses. In 63 fetuses with a persistent left SVC and a right SVC the LBCV was absent.

CONCLUSION

This is the first study describing an effective sonographic approach for the assessment of fetal LBCV dimensions during pregnancy. The normative data may provide an additional means of detecting rare anomalies of systemic and pulmonary veins during pregnancy.

Anomalous origins of bilateral vertebral arteries in a child with Down syndrome and Moyamoya disease. A case report

Variations in vertebral artery origin and course are well-described in the literature. The origin of right vertebral artery from the right common carotid artery is an extremely rare variant. We describe a unique case of a child with Down syndrome with variant origins of bilateral vertebral artery, an aberrant right subclavian artery and concomitant Moyamoya disease of intracranial circulation. The presence of variations of the origin and course of craniocervical arteries might have profound implications in angiographic and surgical procedures and hence it is of great importance to be aware of such a possibility.

Aberrant right subclavian artery: incidence and correlation with other markers of Down syndrome in second-trimester fetuses

OBJECTIVE

To assess the incidence of aberrant right subclavian artery (ARSA) and other strong markers of Down syndrome and their correlation in a large population of second-trimester Down syndrome fetuses assessed in a tertiary referral center.

METHODS

Presence or absence of ARSA and other major ultrasound markers of Down syndrome was assessed in a population of 106 second-trimester Down syndrome fetuses referred to our unit for expert assessment and/or termination of pregnancy after karyotyping performed for positive first- or second-trimester screening or advanced maternal age or on maternal request. All cases in which the diagnosis of Down syndrome followed the ultrasound detection of major anomalies or soft markers were excluded from the study, as were all cases with a gestational age less than 14 + 0 weeks. We searched for the ARSA on the three vessels and trachea view using color or power Doppler. All fetuses underwent a thorough anatomic assessment and fetal echocardiography. The other Down syndrome markers assessed were: absent or hypoplastic nasal bone (NB-), defined as length < 5(th) centile; nuchal fold ≥ 5 mm; and mild pyelectasis (> 5 mm). In addition, the presence of major cardiac and extracardiac defects was recorded. A correlation analysis was then performed in order to investigate possible associations between markers and/or major anomalies. Postmortem or postnatal diagnostic confirmation was available in all cases.

RESULTS

The mean (SD) gestational age at ultrasound assessment was 20.4 (4.1) weeks. The incidence of the various variables in the population of Down syndrome fetuses was: ARSA, 25%; NB-, 43%; nuchal fold ≥ 5 mm, 16%; pyelectasis, 17%; major heart defects, 41%; atrioventricular septal defect, 25%; and extracardiac anomaly, 24%. The presence of ARSA did not correlate with any of the other variables. The only positive correlations (P < 0.05) were between NB- and pyelectasis, and between cardiac and extracardiac defects.

CONCLUSIONS

This represents the largest Down syndrome population assessed for ARSA. In this series, the incidence of ARSA was 25%, lower than previously reported in much smaller series. Its presence did not correlate with the presence of any other marker or major anomaly, including heart defects.

Genetic analysis of Down syndrome-associated heart defects in mice

Human trisomy 21, the chromosomal basis of Down syndrome (DS), is the most common genetic cause of heart defects. Regions on human chromosome 21 (Hsa21) are syntenically conserved with three regions located on mouse chromosome 10 (Mmu10), Mmu16 and Mmu17. In this study, we have analyzed the impact of duplications of each syntenic region on cardiovascular development in mice and have found that only the duplication on Mmu16, i.e., Dp(16)1Yey, is associated with heart defects. Furthermore, we generated two novel mouse models carrying a 5.43-Mb duplication and a reciprocal deletion between Tiam1 and Kcnj6 using chromosome engineering, Dp(16Tiam1-Kcnj6)Yey/+ and Df(16Tiam1-Kcnj6)Yey/+, respectively, within the 22.9-Mb syntenic region on Mmu16. We found that Dp(16Tiam1-Kcnj6)Yey/+, but not Dp(16)1Yey/Df(16Tiam1-Kcnj6)Yey, resulted in heart defects, indicating that triplication of the Tiam1-Knj6 region is necessary and sufficient to cause DS-associated heart defects. Our transcriptional analysis of Dp(16Tiam1-Kcnj6)Yey/+ embryos confirmed elevated expression levels for the genes located in the Tiam-Kcnj6 region. Therefore, we established the smallest critical genomic region for DS-associated heart defects to lay the foundation for identifying the causative gene(s) for this phenotype.

Prenatally detectable congenital heart defects in fetuses with Down syndrome

OBJECTIVE

To document the incidence of congenital heart defects (CHD) that are detectable echocardiographically in the fetus with trisomy 21 and the relationship with nuchal translucency, fetal sex and ethnicity.

METHODS

Data on fetuses with a karyotypic diagnosis of trisomy 21 were collected between January 2002 and March 2010. The data were analyzed for the gestational age at examination, maternal age, reason for referral for fetal echocardiography, cardiac diagnosis, fetal sex, ethnicity and outcome.

RESULTS

Of 917 fetuses with trisomy 21, 487 had a diagnostic echocardiogram. Cardiac examination was performed before 14 weeks' gestation in 75% of cases. The main reasons for referral were increased nuchal translucency (NT) in 76% of cases, suspected cardiac abnormality in 15% and an extracardiac anomaly in 6%. Structural CHD was found in 164/487 (34%), or 98/412 (24%) if those referred for suspected CHD are removed from the analysis. The most common diagnosis was atrioventricular septal defect (AVSD) (115/487, 24%). The ratio of female to male fetuses with AVSD was 29%:18% (P = 0.003). There was no difference in the incidence of AVSD with ethnicity. The pregnancy continued in 36 cases, but three were lost to follow-up; of the known outcomes there were 10 intrauterine deaths, six of which had structural heart disease, and 23 live births, 15 of which had CHD.

CONCLUSION

Most fetuses (66-76%) with trisomy 21 have a structurally normal heart on echocardiography. The presence of structural CHD was not associated with increased NT. The increased incidence of AVSD in females was confirmed in our study, although an ethnic difference could not be confirmed. CHD does not appear to increase the chance of spontaneous intrauterine loss in ongoing pregnancies.

Cardiovascular development and survival during gestation in the Ts65Dn mouse model for Down syndrome

The Ts65Dn mouse model for Down syndrome (DS) exhibits many phenotypes seen in human DS. Previous research has revealed a reduced rate of transmission of the T65Dn marker chromosome in neonates. To analyze potential fetal loss, litters from trisomic females at 10.5dpc through 14.5dpc were genotyped. No significant differences from the expected Mendelian ratio were found in transmission of T65Dn at any stage. Cardiovascular defects found in trisomic neonates are associated with formation of pharyngeal arch arteries. Vessel tracing was used to identify anomalies in 10.5dpc, 11.5dpc, and 13.5dpc embryos. Comparison of trisomic versus euploid embryos injected with India ink revealed delay and abnormality in cardiovascular development in trisomic embryos at each stage. Through the analysis of transmission rate and cardiovascular development in embryonic mice, we learn more about prenatal mortality and the origins of cardiac abnormality in the Ts65Dn mice to assist in understanding cardiovascular malformation associated with DS.

Aberrant right subclavian artery at 16 to 23 + 6 weeks of gestation: a marker for chromosomal abnormality

OBJECTIVES

This study was carried out to determine the feasibility of defining the position of the right subclavian artery (RSA) by fetal echocardiography between 16 and 23 weeks of gestation, and the association between an aberrant right subclavian artery (ARSA) and chromosomal and cardiac defects.

METHODS

We examined the position of the RSA in all patients who attended our unit for a fetal cardiac scan. The assessment was carried out using a transverse view of the fetal chest sweeping up from the level of the aortic arch, using color flow mapping. An ARSA was diagnosed when this vessel was not seen in the normal position and an arterial vessel was seen crossing behind the trachea towards the right arm, arising as a fourth branch of the aortic arch, at a lower level than normal.

RESULTS

The course of the RSA could be identified in more than 95% of the 2799 fetuses examined between 16 and 23 + 6 weeks of gestation. An ARSA was found in 43 fetuses. The incidence was 1.5% in normal fetuses, 28.6% in fetuses with trisomy 21, 18.2% in fetuses with trisomy 18 and 8% in fetuses with other chromosomal defects. There was an association between an ARSA and cardiac defects in seven of the 43 fetuses (16%), and three of these seven fetuses had a normal karyotype.

CONCLUSIONS

Assessment of the RSA by a fetal cardiologist is possible in almost all cases. The finding of an ARSA is much more common in fetuses with chromosomal defects, in particular trisomy 21 (where the prevalence of an ARSA was 29%), compared with euploid fetuses. Moreover, the presence of an ARSA may be associated with an increased incidence of intracardiac malformations. Examination of the position of the RSA is likely to become a routine ultrasound marker for chromosomal abnormalities in the second trimester of pregnancy.

Three-dimensional sonography in the prenatal diagnosis of aortic arch abnormalities

PURPOSE

To assess the added value of 3-dimensional (3D) echocardiography with spatiotemporal image correlation (STIC) in the diagnosis of aortic arch abnormalities in fetuses with isolated abnormal upper thoracic 3-vessel view (3VV).

METHOD

A total of 3,420 women underwent a targeted anatomic survey at 18-22 weeks' gestation in a 1-year period. An isolated abnormal upper thoracic 3VV detected on 2-dimensional (2D) imaging was followed up by conventional 2D echocardiography and 3D fetal echocardiography with STIC. Offline reconstruction by a second operator blinded to the suspected diagnosis was performed. Neonatal echocardiography and MRI with 3D reconstruction were performed to verify the prenatal diagnosis.

RESULT

Of the 3,420 patients referred, 4 had an isolated abnormal 3VV (0.09%). A right-sided aortic arch (RAA, n = 3) and double aortic arch (DAA, n = 1) were suspected. In all aortic arch abnormalities, 3D fetal echocardiography and STIC correctly identified RAA with aberrant left subclavian artery in 3 cases and DAA in 1 case with a degree of definition that was equal to the confirmatory postnatal echocardiography and 3D MRI.

CONCLUSION

Although the 2D upper 3VV is a powerful screening tool for isolated aortic arch abnormalities, 3D fetal echocardiography with STIC allows an accurate prenatal characterization of the abnormality to a degree that is typically attainable only by post partum imaging.

Double aortic arch with double aneuploidy--rare anomaly in combined Down and Klinefelter syndrome

A 14-month-old boy with double aneuploidy and a double aortic arch suffered from frequently recurrent severe feeding and respiratory problems. Chromosomal analysis showed a 48,XXY + 21 karyotype: a double aneuploidy of Down syndrome (DS) and Klinefelter syndrome (KS). Only four cases of double aneuploidy (DS + KS) associated with congenital heart defects have been published of which none had a double aortic arch. Our case report should draw attention to the possibility of a double aortic arch in patients with severe feeding and respiratory problems and a double aneuploidy.

Abnormal number of fetal ribs on 3-dimensional ultrasonography: associated anomalies and outcomes in 75 fetuses

OBJECTIVE

The purpose of this study was to describe the clinical importance of an abnormal number of fetal ribs.

METHODS

A retrospective study of all fetuses that were found to have an abnormal number of ribs during routine ultrasonographic examinations was performed. Volume data sets of the fetal ribs were acquired by either static 3- or 4-dimensional volume contrast imaging in plane C. In all cases, a meticulous survey of the fetal anatomy was performed, and prenatal and postnatal records were reviewed.

RESULTS

Seventy-five fetuses were found retrospectively to have an abnormal number of ribs. Ultrasonographic examinations were done between 14 and 31 weeks' gestation (mean, 21.8 weeks; median, 23 weeks). More than 24 ribs were found in 28 fetuses (37%), and fewer than 24 ribs were found in 47 (63%). Additional anomalies were found in 22 fetuses (29%). Cardiovascular anomalies were detected in 10 fetuses. Seven fetuses had renal anomalies. Two fetuses had mild ventriculomegaly, and 1 fetus had holoprosencephaly. Lung dysplasia was found in 2 cases. One fetus had enlarged nuchal translucency with wormian bones. Termination of pregnancy was performed in 3 cases because of major malformations. The other 19 fetuses with associated abnormalities and the 53 without associated anomalies were born alive with only minor anomalies.

CONCLUSIONS

An abnormal number of fetal ribs is an isolated finding in most cases. It may also be seen with major anomalies; however, more frequently the anomalies are minor, and the overall prognosis is good.

Characterization of the cardiac phenotype in neonatal Ts65Dn mice

The Ts65Dn mouse is the most-studied of murine models for Down syndrome. Homology between the triplicated murine genes and those on human chromosome 21 correlates with shared anomalies of Ts65Dn mice and Down syndrome patients, including congenital heart defects. Lethality is associated with inheritance of the T65Dn chromosome, and anomalies such as right aortic arch with Kommerell's diverticulum and interrupted aortic arch were found in trisomic neonates. The incidence of gross vascular abnormalities was 17% in the trisomic population. Histological analyses revealed interventricular septal defects and broad foramen ovale, while immunohistochemistry showed abnormal muscle composition in the cardiac valves of trisomic neonates. These findings confirm that the gene imbalance present in Ts65Dn disrupts crucial pathways during cardiac development. The candidate genes for congenital heart defects that are among the 104 triplicated genes in Ts65Dn mice are, therefore, implicated in the dysregulation of normal cardiogenic pathways in this model.

Frequency of aberrant subclavian artery, arch laterality, and associated intracardiac anomalies detected by echocardiography

Tetralogy of Fallot is generally considered to be the most common congenital heart defect associated with an aberrant subclavian artery (ASA), but the prevalence of ASA in patients with other cardiac anomalies is not well described. The pediatric echocardiography database, with 15,871 initial echocardiograms, was searched for all patients with ASA. Arch laterality and associated intracardiac anomalies were documented for each patient. ASA was found in 226 patients, of whom 171 had a left aortic arch (LAA) and 55 had a right aortic arch (RAA). The occurrence of ASA was 1% in patients with LAA (171 of 15,650) and 25% in patients with RAA (55 of 221; p = 0.001). Intracardiac anatomy was normal in 32% of patients with ASA/LAA and 25% with ASA/RAA. Conotruncal anomalies occurred more frequently with ASA/RAA than ASA/LAA (36% vs 18%; p = 0.01). Atrioventricular canal defects accounted for 10% and left-sided cardiac obstructive lesions accounted for 11% of subjects with ASA/LAA. ASA was rarely associated with d-transposition of the great arteries (1 of 226) and double-outlet right ventricle (5 of 226). The prevalence of ASA was highest in patients with interrupted aortic arch (11 of 38; 29%). In patients with tetralogy of Fallot, the overall prevalence of ASA was 8% (34 of 447), but was higher with RAA (16 of 103; 16%). The highest prevalence of ASA occurred in the subgroup of patients with tetralogy of Fallot with pulmonary atresia and RAA (6 of 25; 24%). In conclusion, ASA was more common in patients with RAA, especially with conotruncal anomalies. In patients with LAA, hypoplastic left heart syndrome, aortic coarctation, and atrioventricular canal defects were commonly associated with ASA.

Diagnosis of a terminal deletion of 4p with duplication of Xp22.31 in a patient with findings of Opitz G/BBB syndrome and Wolf-Hirschhorn syndrome

Opitz G/BBB syndrome (OS) is a congenital midline malformation syndrome characterized by hypertelorism, hypospadias, cleft lip/palate, laryngotracheoesophageal abnormalities, imperforate anus, developmental delay and cardiac defects. The X-linked form is caused by mutations in the MID1 gene, while no gene has yet been identified for the autosomal dominant form. Here, we report on a 15-year-old boy who was referred for MID1 mutation analysis with findings typical of OS, including apparent hypertelorism, hypospadias, a history of feeding difficulties, dysphagia secondary to esophageal arteria lusoria, growth retardation and developmental delay. No MID1 mutation was found, but subsequent sub-megabase resolution array CGH unexpectedly documented a 2.34 Mb terminal 4p deletion, suggesting a diagnosis of WHS, and a duplication in Xp22.31. Wolf-Hirschhorn syndrome (WHS) is a contiguous gene deletion syndrome involving terminal chromosome 4p deletions, in particular 4p16.3. WHS is characterized by typical facial appearance ("Greek helmet facies"), mental retardation, congenital hypotonia, and growth retardation. While the severity of developmental delay in this patient supports the diagnosis of WHS rather than OS, this case illustrates the striking similarities of clinical findings in seemingly unrelated syndromes, suggesting common or interacting pathways at the molecular and pathogenetic level. This is the first report of arteria lusoria (esophageal vascular ring) in a patient with WHS.

Fetal aberrant right subclavian artery in normal and Down syndrome fetuses

OBJECTIVES

To evaluate the prevalence of fetal aberrant right subclavian artery (ARSA) in a low-risk population and compare it with that among Down syndrome fetuses, in order to estimate its potential as a marker in Down syndrome screening.

METHODS

Women undergoing routine fetal sonographic examination between 13 and 26 weeks of gestation were evaluated once for the presence of ARSA using either a transvaginal multifrequency 5-9-MHz probe or a transabdominal 4-8-MHz probe as appropriate. Early pregnancy outcome was obtained in all cases.

RESULTS

Nine hundred and twenty-four fetuses were recruited. An ARSA was detected in 13 fetuses (1.4%) with normal karyotype. During the study period, eight fetuses with Down syndrome referred either with known karyotype or with signs suspicious for Down syndrome were evaluated by the same protocol. Three of eight fetuses (37.5%) were found to have an ARSA. In none of these cases was ARSA an isolated finding. The odds ratio for ARSA in Down syndrome compared with normal fetuses was 42.04 (95% CI, 9.08-194.6).

CONCLUSIONS

An ARSA was found in 1.4% of the normal population. In the small group of Down syndrome fetuses we observed a trend towards a higher rate of ARSA than in normal fetuses. In none of the Down syndrome fetuses was ARSA an isolated finding. Larger prospective studies are needed to examine the significance of ARSA as an isolated finding and the potential of ARSA as a marker in Down syndrome screening.

Down syndrome and aberrant right subclavian artery

Down syndrome (DS) may be associated with various organ system disorders. Feeding problems are frequent in children with DS and may be caused by associated defects, including congenital heart defects, gastrointestinal defects, or endocrine disorders. In the absence of these associated conditions, feeding problems are often attributed to general hypotonia. However, an aberrant right subclavian artery (ARSA), a rare vascular anomaly and an unusual cause of problems with the passage of solid food through the esophagus, has recently been suggested to occur more frequently in patients with DS. This knowledge is of importance when evaluating feeding difficulties in patients with DS. Additional investigation for identifying an ARSA may be indicated in selected patients. Diagnostic techniques, such as transthoracic echocardiography, barium contrast esophagram, angiography, or computed tomography-angiography (CT) can be used in a diagnostic flow chart. The presence of ARSA is not synonymous to the cause of feeding problems in patients with DS and corrective surgery of this vascular anomaly should be restricted to selected cases.

Aberrant right subclavian artery at 11 + 0 to 13 + 6 weeks of gestation in chromosomally normal and abnormal fetuses

OBJECTIVES

To establish the feasibility of examining the subclavian artery at 11 + 0 to 13 + 6 weeks of gestation, and to determine the prevalence of aberrant right subclavian artery (ARSA) in chromosomally normal and chromosomally abnormal fetuses.

METHODS

Fetal echocardiography was performed prospectively in 516 patients before chorionic villus sampling at 11 + 0 to 13 + 6 weeks of gestation. Transabdominal sonography was carried out, and color flow mapping was used to identify the right subclavian artery and determine whether this was normal or aberrant (ARSA). Second-trimester fetal echocardiography was also carried out in a subgroup of 183 fetuses.

RESULTS

The median gestational age was 12 weeks and the median crown-rump length was 68 mm. Successful assessment of the right subclavian artery was achieved in 425/516 (82.4%) cases and the rate of failure to do so was significantly associated with decreasing fetal crown-rump length (r = 0.174, P < 0.001) and increasing maternal body mass index (r = 0.275, P < 0.001). An ARSA was observed in 2/353 (0.6%) fetuses with a normal karyotype, in 4/51 (7.8%) cases with trisomy 21 and in 2/20 (10.0%) with other chromosomal defects. In a subgroup of 183 fetuses examined in both the first and second trimester there were three cases of ARSA observed at both scans and an additional case in which ARSA was detected only at the second scan.

CONCLUSIONS

Assessment of the position of the right subclavian artery is feasible at the 11 + 0 to 13 + 6-week scan and ARSA is more common in chromosomally abnormal than normal fetuses. However, ARSA in the first trimester is unlikely to be a useful marker of trisomy 21.

The power of comparative and developmental studies for mouse models of Down syndrome

Since the genetic basis for Down syndrome (DS) was described, understanding the causative relationship between genes at dosage imbalance and phenotypes associated with DS has been a principal goal of researchers studying trisomy 21 (Ts21). Though inferences to the gene-phenotype relationship in humans have been made, evidence linking a specific gene or region to a particular congenital phenotype has been limited. To further understand the genetic basis for DS phenotypes, mouse models with three copies of human chromosome 21 (Hsa21) orthologs have been developed. Mouse models offer access to every tissue at each stage of development, opportunity to manipulate genetic content, and ability to precisely quantify phenotypes. Numerous approaches to recreate trisomic composition and analyze phenotypes similar to DS have resulted in diverse trisomic mouse models. A murine intraspecies comparative analysis of different genetic models of Ts21 and specific DS phenotypes reveals the complexity of trisomy and important considerations to understand the etiology of and strategies for amelioration or prevention of trisomic phenotypes. By analyzing individual phenotypes in different mouse models throughout development, such as neurologic, craniofacial, and cardiovascular abnormalities, greater insight into the gene-phenotype relationship has been demonstrated. In this review we discuss how phenotype-based comparisons between DS mouse models have been useful in analyzing the relationship of trisomy and DS phenotypes.

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.

Right aortic arch detected in fetal life

OBJECTIVE

To evaluate the prenatal distribution, associated conditions and outcome of the different types of right aortic arch (RAA) detected in fetal life.

METHODS

This was a retrospective review of all cases of RAA detected prenatally between 1998 and 2005 in two tertiary referral centers.

RESULTS

In the study period 71 cases of RAA were detected; 26 (37%) had RAA with aberrant left subclavian artery, 23 (32%) had RAA with mirror-image branching, 20 (28%) had RAA of unknown type and two (3%) had double aortic arch. While 20/26 cases with RAA and aberrant left subclavian artery were isolated findings, all 23 cases with RAA and mirror-image branching were associated with cardiac defects, namely tetralogy of Fallot (43%) or pulmonary atresia with ventricular septal defect (22%). Of the 20 cases with RAA, 19 of unknown type were associated with heterotaxy syndromes and had additional cardiac malformations and ambiguities of the situs. The two cases with DAA were isolated findings. Seven cases in our series (10%) had a microdeletion 22q11 and these were significantly associated with extracardiac malformations. The outcome in our series depended solely on the associated cardiac and extracardiac malformations, with the exception of one infant with isolated DAA, in whom a surgical correction was warranted.

CONCLUSIONS

RAA detected in fetal life is associated frequently with other cardiac/non-cardiac malformations, heterotaxy syndromes and microdeletions 22q11. The associated conditions vary depending on the branching type of the brachiocephalic vessels and the presence of extracardiac malformations.

Postnatal lethality and cardiac anomalies in the Ts65Dn Down syndrome mouse model

The Ts65Dn mouse is a well-studied model for Down syndrome (DS). The presence of the translocation chromosome T17 16 (referred to as T65Dn) produces a trisomic dosage imbalance for over 100 genes on the distal region of mouse Chromosome 16. This dosage imbalance, with more than half of the orthologs of human Chromosome 21 (Hsa21), causes several phenotypes in the trisomic mice that are reminiscent of DS. Careful examination of neonates in a newly established Ts65Dn colony indicated high rates of postnatal lethality. Although the transmission rate for the T65Dn chromosome has been previously reported as 20%-40%, genotyping of all progeny indicates transmission at birth is near the 50% expected with Mendelian transmission and survival. Remarkably, in litters with maternal care that allowed survival of some pups, postnatal lethality occurred primarily in pups that inherited the T65Dn marker chromosome. This selective loss within 48 h of birth reduced the transmission of the marker chromosome from 49% at birth to 34% at weaning. Gross morphologic examination revealed cardiovascular anomalies, i.e., right aortic arch accompanied by septal defects, in 8.3% of the trisomic newborn cadavers examined. This is an intriguing finding because the orthologs of the DiGeorge region of HSA22, which are posited to contribute to the aortic arch abnormalities seen in trisomy 16 mice, are not triplicated in Ts65Dn mice. These new observations suggest that the Ts65Dn mouse models DS not only in its previously described phenotypes but also with elevated postnatal lethality and congenital heart malformations that may contribute to mortality.

Ehlers-Danlos type IV syndrome in a patient with Down syndrome: simple co-occurrence or true association?

Down syndrome, a common chromosome aneuploidy, has been associated with an increased incidence of cutaneous disorders. The simultaneous occurrence with Ehlers-Danlos syndrome (EDS) is rare. We report here the clinical case of a 19-year-old female patient with Down syndrome (trisomy 21) who was also affected by EDS type IV. She died from spontaneous bleeding due to rupture of nonaneurysmal abdominal aorta. Since the affected chromosomes in these two syndromes are different (21 and 2, respectively), the concomitant appearance of Down syndrome and EDS type IV in our patient, though clinically intriguing, most likely represents a co-occurrence. However, the possibility that a presently unknown link may exist between these syndromes cannot be ruled out.