A genetic etiology for interruption of the aortic arch type B

Aberrant Subclavian Artery in Interrupted Aortic Arch with Severe Aortic Outlet Obstruction: Cerebral Blood Flow as a Possible Determinant of Embryonic Cardiovascular Development?

Aberrant subclavian artery (ASCA) is frequently observed in interrupted aortic arch (IAA) with aortic/subaortic obstruction. Developmental significance of ASCA in IAA in utero remains elusive. Newborns with prenatally diagnosed isolated IAA under continuous prostaglandin E1 infusion were studied. Cross-sectional areas of aortic valve opening (AVOCSA) and patent ductus arteriosus (PDACSA) were represented by echocardiographic measurement of (diameter)2 indexed by body surface area (m2). Types of IAA and presence of ASCA were examined in relation to sizes of AVOCSA and PDACSA. Twenty-four newborns with IAA (six type A and 18 type B) were reviewed. Male dominance was seen in type B (male 72%). Twenty-three patients had left aortic arch. No type A patients had ASCA, but 50% of type B had ASCA; AVOCSA was significantly smaller in type B than in type A (p = 0.003). In type B, PDACSA was significantly larger in those with ASCA than without (p = 0.003), but AVOCSA exhibited no significant size difference between these two subgroups. Chromosome 22q11 deletion was only seen in type B (56%) and showed no significant correlation with the presence of ASCA. In type B IAA, the presence of ASCA was associated with larger PDACSA, suggesting an adaptive enlargement of the ductus arteriosus and ASCA in response to reduced antegrade flow across small AVOCSA, which may be augmenting cerebral blood flow. Preservation of cerebral blood flow may be another important determinant affecting embryonic cardiovascular development.

Molecular Pathways and Animal Models of Semilunar Valve and Aortic Arch Anomalies

The great arteries of the vertebrate carry blood from the heart to the systemic circulation and are derived from the pharyngeal arch arteries. In higher vertebrates, the pharyngeal arch arteries are a symmetrical series of blood vessels that rapidly remodel during development to become the asymmetric aortic arch arteries carrying oxygenated blood from the left ventricle via the outflow tract. At the base of the aorta, as well as the pulmonary trunk, are the semilunar valves. These valves each have three leaflets and prevent the backflow of blood into the heart. During development, the process of aortic arch and valve formation may go wrong, resulting in cardiovascular defects, and these may, at least in part, be caused by genetic mutations. In this chapter, we will review models harboring genetic mutations that result in cardiovascular defects affecting the great arteries and the semilunar valves.

Human Genetics of Congenital Heart Defects

Congenital heart diseases (or congenital heart defects/disorders; CHDs) are structural abnormalities of the heart and/or great vessels that are present at birth. CHDs include an extensive range of defects that may be minor and require no intervention or may be life-limiting and require complex surgery shortly after birth. This chapter reviews the current knowledge on the genetic causes of CHD.

Perinatal Diagnosis and Management of a Case with Interrupted Aortic Arch, Pulmonary Valve Dysplasia and 22q11.2 Deletion: A Case Report

The 22q11.2 deletion syndrome (22q11.2DS) is the most common chromosomal microdeletion disorder caused by hemizygous microdeletion of the long arm of chromosome 22. It is now known to have a heterogenous presentation that includes multiple additional congenital anomalies and later-onset conditions, such as gastrointestinal and renal abnormalities, autoimmune disease, variable cognitive delays, behavioral phenotypes and psychiatric illness. The purpose of our paper is to present the case of a fetus diagnosed with a complex association of cardiac anomalies: interrupted aortic arch type B, large malalignment-type ventricular septal defect, pulmonary valve dysplasia, and aberrant right subclavian artery for whom the result of genetic testing revealed 22q11.2 deletion. The pregnancy was regularly followed until delivery which took place in Germany so that neonatal cardiac surgery could be performed in an experienced center for cardiac malformations. The distinctivness of our report resides in the fact that it offers a complete image of a case of 22q11.2 deletion syndrome starting from the prenatal diagnosis (and emphasizing on the most relevant sonographic features) and, with parents not opting for termination of pregnancy, ending with the newborn surviving major cardiac surgery, offering thus the possibility to bring into focus postnatal outcome and future expectations in similar cases.

Morphogenetic processes in the development and evolution of the arteries of the pharyngeal arches: their relations to congenital cardiovascular malformations

The heart and aortic arch arteries in amniotes form a double circulation, taking oxygenated blood from the heart to the body and deoxygenated blood to the lungs. These major vessels are formed in embryonic development from a series of paired and symmetrical arteries that undergo a complex remodelling process to form the asymmetric arch arteries in the adult. These embryonic arteries form in the pharyngeal arches, which are symmetrical bulges on the lateral surface of the head. The pharyngeal arches, and their associated arteries, are found in all classes of vertebrates, but the number varies, typically with the number of arches reducing through evolution. For example, jawed vertebrates have six pairs of pharyngeal arch arteries but amniotes, a clade of tetrapod vertebrates, have five pairs. This had led to the unusual numbering system attributed to each of the pharyngeal arch arteries in amniotes (1, 2, 3, 4, and 6). We, therefore, propose that these instead be given names to reflect the vessel: mandibular (1st), hyoid (2nd), carotid (3rd), aortic (4th) and pulmonary (most caudal). Aberrant arch artery formation or remodelling leads to life-threatening congenital cardiovascular malformations, such as interruption of the aortic arch, cervical origin of arteries, and vascular rings. We discuss why an alleged fifth arch artery has erroneously been used to interpret congenital cardiac lesions, which are better explained as abnormal collateral channels, or remodelling of the aortic sac.

Morphogenesis of the Mammalian Aortic Arch Arteries

The major vessels in mammals that take blood away from the heart and deliver it to the arms and the head take their origin from the aortic arch and are derived from the arteries formed within the embryonic pharyngeal arches. These pharyngeal arch arteries, initially symmetrical, form in a cranial to caudal sequence within the pharyngeal mesenchyme. They then undergo a complex process of remodeling to produce the asymmetrical brachiocephalic arteries as seen in the adult. A complex interaction between the tissues of the pharyngeal arches and the genes they express is required to ensure that arterial formation and remodeling is able to proceed normally. If this process is disrupted, life-threatening congenital cardiovascular malformations can occur, such as interruption of the aortic arch, isolation of individual arteries, or so-called vascular rings. Here, using state-of-the-art imaging techniques, we describe the morphogenesis of the arteries in humans and mice and the cardiovascular defects in the Tbx1 mutant mouse model. We provide details of the process of remodeling, clarifying also the morphogenesis of the external carotid artery and the so-called "migration" of the left subclavian artery.

Msx1 haploinsufficiency modifies the Pax9-deficient cardiovascular phenotype

BACKGROUND

Successful embryogenesis relies on the coordinated interaction between genes and tissues. The transcription factors Pax9 and Msx1 genetically interact during mouse craniofacial morphogenesis, and mice deficient for either gene display abnormal tooth and palate development. Pax9 is expressed specifically in the pharyngeal endoderm at mid-embryogenesis, and mice deficient for Pax9 on a C57Bl/6 genetic background also have cardiovascular defects affecting the outflow tract and aortic arch arteries giving double-outlet right ventricle, absent common carotid arteries and interruption of the aortic arch.

RESULTS

In this study we have investigated both the effect of a different genetic background and Msx1 haploinsufficiency on the presentation of the Pax9-deficient cardiovascular phenotype. Compared to mice on a C57Bl/6 background, congenic CD1-Pax9^-/- mice displayed a significantly reduced incidence of outflow tract defects but aortic arch defects were unchanged. Pax9^-/- mice with Msx1 haploinsufficiency, however, have a reduced incidence of interrupted aortic arch, but more cases with cervical origins of the right subclavian artery and aortic arch, than seen in Pax9^-/- mice. This alteration in arch artery defects was accompanied by a rescue in third pharyngeal arch neural crest cell migration and smooth muscle cell coverage of the third pharyngeal arch arteries. Although this change in phenotype could theoretically be compatible with post-natal survival, using tissue-specific inactivation of Pax9 to maintain correct palate development whilst inducing the cardiovascular defects was unable to prevent postnatal death in the mutant mice. Hyoid bone and thyroid cartilage formation were abnormal in Pax9^-/- mice.

CONCLUSIONS

Msx1 haploinsufficiency mitigates the arch artery defects in Pax9^-/- mice, potentially by maintaining the survival of the 3rd arch artery through unimpaired migration of neural crest cells to the third pharyngeal arches. With the neural crest cell derived hyoid bone and thyroid cartilage also being defective in Pax9^-/- mice, we speculate that the pharyngeal endoderm is a key signalling centre that impacts on neural crest cell behaviour highlighting the ability of cells in different tissues to act synergistically or antagonistically during embryo development.

Genetic Etiology of Left-Sided Obstructive Heart Lesions: A Story in Development

Congenital heart disease is the most common congenital defect observed in newborns. Within the spectrum of congenital heart disease are left‐sided obstructive lesions (LSOLs), which include hypoplastic left heart syndrome, aortic stenosis, bicuspid aortic valve, coarctation of the aorta, and interrupted aortic arch. These defects can arise in isolation or as a component of a defined syndrome; however, nonsyndromic defects are often observed in multiple family members and associated with high sibling recurrence risk. This clear evidence for a heritable basis has driven a lengthy search for disease‐causing variants that has uncovered both rare and common variants in genes that, when perturbed in cardiac development, can result in LSOLs. Despite advancements in genetic sequencing platforms and broadening use of exome sequencing, the currently accepted LSOL‐associated genes explain only 10% to 20% of patients. Further, the combinatorial effects of common and rare variants as a cause of LSOLs are emerging. In this review, we highlight the genes and variants associated with the different LSOLs and discuss the strengths and weaknesses of the present genetic associations. Furthermore, we discuss the research avenues needed to bridge the gaps in our current understanding of the genetic basis of nonsyndromic congenital heart disease.

Failed Progenitor Specification Underlies the Cardiopharyngeal Phenotypes in a Zebrafish Model of 22q11.2 Deletion Syndrome

Microdeletions involving TBX1 result in variable congenital malformations known collectively as 22q11.2 deletion syndrome (22q11.2DS). Tbx1-deficient mice and zebrafish recapitulate several disease phenotypes, including pharyngeal arch artery (PAA), head muscle (HM), and cardiac outflow tract (OFT) deficiencies. In zebrafish, these structures arise from nkx2.5⁺ progenitors in pharyngeal arches 2-6. Because pharyngeal arch morphogenesis is compromised in Tbx1-deficient animals, the malformations were considered secondary. Here, we report that the PAA, HM, and OFT phenotypes in tbx1 mutant zebrafish are primary and arise prior to pharyngeal arch morphogenesis from failed specification of the nkx2.5⁺ pharyngeal lineage. Through in situ analysis and lineage tracing, we reveal that nkx2.5 and tbx1 are co-expressed in this progenitor population. Furthermore, we present evidence suggesting that gdf3-ALK4 signaling is a downstream mediator of nkx2.5⁺ pharyngeal lineage specification. Collectively, these studies support a cellular mechanism potentially underlying the cardiovascular and craniofacial defects observed in the 22q11.2DS population.

Pax9 is required for cardiovascular development and interacts with Tbx1 in the pharyngeal endoderm to control 4th pharyngeal arch artery morphogenesis

Developmental defects affecting the heart and aortic arch arteries are a significant phenotype observed in individuals with 22q11 deletion syndrome and are caused by a microdeletion on chromosome 22q11. TBX1, one of the deleted genes, is expressed throughout the pharyngeal arches and is considered a key gene, when mutated, for the arch artery defects. Pax9 is expressed in the pharyngeal endoderm and is downregulated in Tbx1 mutant mice. We show here that Pax9-deficient mice are born with complex cardiovascular malformations that affect the outflow tract and aortic arch arteries with failure of the 3rd and 4th pharyngeal arch arteries to form correctly. Transcriptome analysis indicated that Pax9 and Tbx1 may function together, and mice double heterozygous for Tbx1/Pax9 presented with a significantly increased incidence of interrupted aortic arch when compared with Tbx1 heterozygous mice. Using a novel Pax9Cre allele, we demonstrated that the site of this Tbx1-Pax9 genetic interaction is the pharyngeal endoderm, therefore revealing that a Tbx1-Pax9-controlled signalling mechanism emanating from the pharyngeal endoderm is required for crucial tissue interactions during normal morphogenesis of the pharyngeal arch artery system.

Summary: A strong genetic interaction between Tbx1 and Pax9 that leads to 4th PAA-derived defects in double heterozygous mice is cell-autonomous within the pharyngeal endoderm.

Left pulmonary artery in 22q11.2 deletion syndrome. Echocardiographic evaluation in patients without cardiac defects and role of Tbx1 in mice

Introduction and hypothesis

Patients with 22q11 deletion syndrome (22q11.2DS) present, in about 75% of cases, typical patterns of cardiac defects, with a particular involvement on the ventricular outflow tract and great arteries. However, in this genetic condition the dimensions of the pulmonary arteries (PAs) never were specifically evaluated.

We measured both PAs diameter in patients with 22q11.2DS without cardiac defects, comparing these data to a normal control group. Moreover, we measured the PAs diameter in Tbx1 mutant mice. Finally, a cell fate mapping in Tbx1 mutants was used to study the expression of this gene in the morphogenesis of PAs.

Methods

We evaluated 58 patients with 22q11.2DS without cardiac defects. The control group consisted of 54 healthy subjects, matched for age and sex. All cases underwent a complete transthoracic echocardiography. Moreover, we crossed Tbx1^+/- mice and harvested fetuses. We examined the cardiovascular phenotype of 8 wild type (WT), 37 heterozygous (Tbx1^+/-) and 6 null fetuses (Tbx1^-/-). Finally, we crossed Tbx1^Cre/+mice with R26R^mT-mG Cre reporter mice to study Tbx1 expression in the pulmonary arteries.

Results

The echocardiographic study showed that the mean of the LPA/RPA ratio in 22q11.2DS was smaller (0.80 ± 0.12) than in controls (0.97 ± 0.08; p < 0.0001).

Mouse studies resulted in similar data as the size of LPA and RPA was not significantly different in WT embryos, but in Tbx1^+/- and Tbx1^-/- embryos the LPA was significantly smaller than the RPA in both mutants (P = 0.0016 and 0.0043, respectively). We found that Tbx1 is expressed near the origin of the PAs and in their adventitia.

Conclusions

Children with 22q11.2DS without cardiac defects show smaller LPA compared with healthy subjects. Mouse studies suggest that this anomaly is due to haploinsufficiency of Tbx1. These data may be useful in the clinical management of children with 22q11.2DS and should guide further experimental studies as to the mechanisms underlying PAs development.

Dysregulation of TBX1 dosage in the anterior heart field results in congenital heart disease resembling the 22q11.2 duplication syndrome

Non-allelic homologous recombination events on chromosome 22q11.2 during meiosis can result in either the deletion (22q11.2DS) or duplication (22q11.2DupS) syndrome. Although the spectrum and frequency of congenital heart disease (CHD) are known for 22q11.2DS, there is less known for 22q11.2DupS. We now evaluated cardiac phenotypes in 235 subjects with 22q11.2DupS including 102 subjects we collected and 133 subjects that were previously reported as a confirmation and found 25% have CHD, mostly affecting the cardiac outflow tract (OFT). Previous studies have shown that global loss or gain of function (LOF; GOF) of mouse Tbx1, encoding a T-box transcription factor mapping to the region of synteny to 22q11.2, results in similar OFT defects. To further evaluate Tbx1 function in the progenitor cells forming the cardiac OFT, termed the anterior heart field, Tbx1 was overexpressed using the Mef2c-AHF-Cre driver (Tbx1 GOF). Here we found that all resulting conditional GOF embryos had a persistent truncus arteriosus (PTA), similar to what was previously reported for conditional Tbx1 LOF mutant embryos. To understand the basis for the PTA in the conditional GOF embryos, we found that proliferation in the Mef2c-AHF-Cre lineage cells before migrating to the heart, was reduced and critical genes were oppositely changed in this tissue in Tbx1 GOF embryos versus conditional LOF embryos. These results suggest that a major function of TBX1 in the AHF is to maintain the normal balance of expression of key cardiac developmental genes required to form the aorta and pulmonary trunk, which is disrupted in 22q11.2DS and 22q11.2DupS.

Loss of CXCL12/CXCR4 signalling impacts several aspects of cardiovascular development but does not exacerbate Tbx1 haploinsufficiency

The CXCL12-CXCR4 pathway has crucial roles in stem cell homing and maintenance, neuronal guidance, cancer progression, inflammation, remote-conditioning, cell migration and development. Recently, work in chick suggested that signalling via CXCR4 in neural crest cells (NCCs) has a role in the 22q11.2 deletion syndrome (22q11.2DS), a disorder where haploinsufficiency of the transcription factor TBX1 is responsible for the major structural defects. We tested this idea in mouse models. Our analysis of genes with altered expression in Tbx1 mutant mouse models showed down-regulation of Cxcl12 in pharyngeal surface ectoderm and rostral mesoderm, both tissues with the potential to signal to migrating NCCs. Conditional mutagenesis of Tbx1 in the pharyngeal surface ectoderm is associated with hypo/aplasia of the 4th pharyngeal arch artery (PAA) and interruption of the aortic arch type B (IAA-B), the cardiovascular defect most typical of 22q11.2DS. We therefore analysed constitutive mouse mutants of the ligand (CXCL12) and receptor (CXCR4) components of the pathway, in addition to ectodermal conditionals of Cxcl12 and NCC conditionals of Cxcr4. However, none of these typical 22q11.2DS features were detected in constitutively or conditionally mutant embryos. Instead, duplicated carotid arteries were observed, a phenotype recapitulated in Tie-2Cre (endothelial) conditional knock outs of Cxcr4. Previous studies have demonstrated genetic interaction between signalling pathways and Tbx1 haploinsufficiency e.g. FGF, WNT, SMAD-dependent. We therefore tested for possible epistasis between Tbx1 and the CXCL12 signalling axis by examining Tbx1 and Cxcl12 double heterozygotes as well as Tbx1/Cxcl12/Cxcr4 triple heterozygotes, but failed to identify any exacerbation of the Tbx1 haploinsufficient arch artery phenotype. We conclude that CXCL12 signalling via NCC/CXCR4 has no major role in the genesis of the Tbx1 loss of function phenotype. Instead, the pathway has a distinct effect on remodelling of head vessels and interventricular septation mediated via CXCL12 signalling from the pharyngeal surface ectoderm and second heart field to endothelial cells.

22q11.2 deletion syndrome

22q11.2 deletion syndrome (22q11.2DS) is the most common chromosomal microdeletion disorder, estimated to result mainly from de novo non-homologous meiotic recombination events occurring in approximately 1 in every 1,000 fetuses. The first description in the English language of the constellation of findings now known to be due to this chromosomal difference was made in the 1960s in children with DiGeorge syndrome, who presented with the clinical triad of immunodeficiency, hypoparathyroidism and congenital heart disease. The syndrome is now known to have a heterogeneous presentation that includes multiple additional congenital anomalies and later-onset conditions, such as palatal, gastrointestinal and renal abnormalities, autoimmune disease, variable cognitive delays, behavioural phenotypes and psychiatric illness - all far extending the original description of DiGeorge syndrome. Management requires a multidisciplinary approach involving paediatrics, general medicine, surgery, psychiatry, psychology, interventional therapies (physical, occupational, speech, language and behavioural) and genetic counselling. Although common, lack of recognition of the condition and/or lack of familiarity with genetic testing methods, together with the wide variability of clinical presentation, delays diagnosis. Early diagnosis, preferably prenatally or neonatally, could improve outcomes, thus stressing the importance of universal screening. Equally important, 22q11.2DS has become a model for understanding rare and frequent congenital anomalies, medical conditions, psychiatric and developmental disorders, and may provide a platform to better understand these disorders while affording opportunities for translational strategies across the lifespan for both patients with 22q11.2DS and those with these associated features in the general population.

The aberrant right subclavian artery (arteria lusoria): the morphological and clinical aspects of one of the most important variations--a systematic study of 141 reports

The most important abnormality of the aortic arch is arguably the presence of an aberrant right subclavian artery (arteria lusoria). If this vessel compresses the adjacent structures, several symptoms may be produced. The aim of the study is to present the morphological and clinical aspects of the aberrant right subclavian artery. Three different databases searched for a review of pertinent literature using strictly predetermined criteria. Of 141 cases, 15 were cadaveric and 126 were clinically documented. The gender distribution of the subjects was 55.3% female and 44.7% male. The mean age of the patients at symptoms onset was 49.9 ± 19.4 years for all patients but 54.0 ± 19.6 years and 44.9 ± 18.1 years for female and male subjects, respectively (P = 0.0061). The most common symptoms in this group were dysphagia (71.2%), dyspnea (18.7%), retrosternal pain (17.0%), cough (7.6%), and weight loss (5.9%). The vascular anomalies coexisting with an arteria lusoria were truncus bicaroticus (19.2%), Kommerell's diverticulum (14.9%), aneurysm of the artery itself (12.8%), and a right sided aortic arch (9.2%). In conclusion, compression of adjacent structures by an aberrant right subclavian artery needs to be differentiated from other conditions presenting dysphagia, dyspnea, retrosternal pain, cough, and weight loss.

Operative challenges in management of concurrent interrupted aortic arch and descending thoracic aortic aneurysm

Interrupted aortic arch is a rare finding in the adult patient. This condition in combination with a descending thoracic aortic aneurysm is an even more exceptional occurrence. Surgical management includes open, endovascular, and hybrid options. We present the case of a 57-year-old man with interrupted aortic arch and concomitant descending thoracic aortic aneurysm, review characterization of this entity, and discuss management options with consideration to associated risks.

The 22q11 deletion: DiGeorge and velocardiofacial syndromes and the role of TBX1

Hemizygous deletion of 22q11 affects approximately 1:4000 live births and may give rise to many different malformations but classically results in a constellation of phenotypes that receive a diagnosis of DiGeorge syndrome or velocardiofacial syndrome. Particularly affected are the heart and great vessels, the endocrine glands of the neck, the face, the soft palate, and cognitive development. Although up to 50 genes may be deleted, it is haploinsufficiency of the transcription factor TBX1 that is thought to make the greatest contribution to the disorder. Mouse embryos are exquisitely sensitive to varying levels of Tbx1 mRNA, and Tbx1 is required in all three germ layers of the embryonic pharyngeal region for normal development. TBX1 controls cell proliferation and affects cellular differentiation in a cell autonomous fashion, but it also directs non-cell autonomous effects, most notably in the signaling between pharyngeal surface ectoderm and the rostral neural crest. TBX1 interacts with several signaling pathways, including fibroblast growth factor, retinoic acid, CTNNB1 (formerly known as β-catenin), and bone morphogenetic protein (BMP), and may regulate pathways by both DNA-binding and non-binding activity. In addition to the structural abnormalities seen in 22q11 deletion syndrome (DS) and Tbx1 mutant mouse models, patients reaching adolescence and adulthood have a predisposition to psychiatric illness. Whether this has a developmental basis and, if so, which genes are involved is an ongoing strand of research. Thus, knowledge of the genetic and developmental mechanisms underlying 22q11DS has the potential to inform about common disease as well as developmental defect.

Epigenetic mechanisms in cardiac development and disease

During mammalian development, cardiac specification and ultimately lineage commitment to a specific cardiac cell type is accomplished by the action of specific transcription factors (TFs) and their meticulous control on an epigenetic level. In this review, we detail how cardiac-specific TFs function in concert with nucleosome remodeling and histone-modifying enzymes to regulate a diverse network of genes required for processes such as cell growth and proliferation, or epithelial to mesenchymal transition (EMT), for instance. We provide examples of how several cardiac TFs, such as Nkx2.5, WHSC1, Tbx5, and Tbx1, which are associated with developmental and congenital heart defects, are required for the recruitment of histone modifiers, such as Jarid2, p300, and Ash2l, and components of ATP-dependent remodeling enzymes like Brg1, Baf60c, and Baf180. Binding of these TFs to their respective sites at cardiac genes coincides with a distinct pattern of histone marks, indicating that the precise regulation of cardiac gene networks is orchestrated by interactions between TFs and epigenetic modifiers. Furthermore, we speculate that an epigenetic signature, comprised of TF occupancy, histone modifications, and overall chromatin organization, is an underlying mechanism that governs cardiac morphogenesis and disease.

The three-vessel view in the fetal mediastinum in the diagnosis of interrupted aortic arch

Interruption of the aortic arch (IAA) is difficult to detect and diagnose in utero. However, prenatal diagnosis may be beneficial because IAA is rapidly fatal (median age, 10 d) if left uncorrected. Our objective was to review the direct and indirect echocardiographic markers associated with IAA, focusing on the importance of the three-vessel view (3VV), which is obtained during routine ultrasound examination to rule out malformations. We analyzed the fetal echocardiograms of nine fetuses and compared them with 56 normal controls. In each fetus, there was a large discrepancy between the diameter of the larger, dilated pulmonary artery (PA) and smaller, narrow aortic arch (Ao). The calculated ratio of PA/Ao in fetuses with IAA was 2.6 ± 0.4 compared with 1.1 ± 0.09 in normal controls (p < 0.0001). The calculated ratio of PA/Ao in fetuses with IAA type A was 2.1 ± 0.09 and IAA type B 2.9 ± 0.2 (p = 0.0007). Discrepancy between PA/Ao diameters should raise the suspicion of aortic arch anomalies and a large discrepancy is a nearly pathognomonic sign of IAA type B.

Isolated interrupted aortic arch: unexpected diagnosis in a 63-year-old male

A 63-year-old male with history of hypertension, dyspnea on exertion, and chronic chest pain was admitted for elective cardiac angiography. Arterial blood pressure was 160/90 mmHg in both arms. Femoral and popliteal pulses were extremely weak, and third (S₃) and fourth (S₄) heart sounds were audible. Aortography showed a mildly dilated aortic root with double brachiocephalic trunk and interruption of aortic arch at isthmus. Profuse and well-developed collaterals appeared at neck and thorax. The patient was recommended to take medical treatment for his hypertension and advanced heart failure. The aim of this paper, is to review the diagnostic and therapeutic options for treatment of the interrupted aortic arch.

Síndrome de deleção 22q11.2 e cardiopatias congênitas

OBJETIVO: Revisar as características clínicas, etiológicas e diagnósticas da síndrome de deleção 22q11 e sua associação com as cardiopatias congênitas. FONTES DOS DADOS: Foram pesquisados artigos científicos presentes nos portais Medline, Lilacs e SciELO, utilizando-se descritores específicos como "22q11", "DiGeorge syndrome", "velocardiofacial syndrome", "congenital heart defects" e "cardio-vascular malformations". O período adotado para a revisão foi de 1980 a 2009. SÍNTESE DOS DADOS: As malformações cardíacas são os defeitos congênitos observados mais frequentemente ao nascimento e representam um problema importante de Saúde Pública. Dentre suas principais causas conhecidas destaca-se a síndrome de deleção 22q11, também chamada de síndrome de DiGeorge, síndrome velocardiofacial e CATCH22. Trata-se de uma doença autossômica domi-nante caracterizada por um fenótipo altamente variável, o que dificulta em muito seu reconhecimento clínico. Além disso, a maior parte dos pacientes apresenta uma microdeleção identificada principalmente por técnicas de citogenética molecular, como a hibridização in situ fluorescente, pouco disponíveis em nosso meio. De forma similar a outras síndromes, a síndrome de deleção 22q11 associa-se a certos defeitos cardíacos específicos, no caso os do tipo conotruncal. Apesar disso, não há ainda na literatura um consenso sobre quais os pacientes com car-diopatia congênita que deveriam ser investigados para a síndrome de deleção 22q11. CONCLUSÕES: Cardiologistas e cirurgiões cardíacos, espe-cialmente pediátricos, devem estar cientes das peculiaridades e dos cuidados dispensados à síndrome de deleção 22q11. Os indivíduos com a síndrome apresentam comumente alterações envolvendo vários sistemas, o que pode levar a dificuldades e a complicações durante seu manejo clínico e cirúrgico.

Multiplexed quantitative real-time PCR to detect 22q11.2 deletion in patients with congenital heart disease

22q11.2 Deletion syndrome (22q11.2 DS) [DiGeorge syndrome type 1 (DGS1)] occurs in ∼1:3,000 live births; 75% of children with DGS1 have severe congenital heart disease requiring early intervention. The gold standard for detection of DGS1 is fluorescence in situ hybridization (FISH) with a probe at the TUPLE1 gene. However, FISH is costly and is typically ordered in conjunction with a karyotype analysis that takes several days. Therefore, FISH is underutilized and the diagnosis of 22q11.2 DS is frequently delayed, often resulting in profound clinical consequences. Our goal was to determine whether multiplexed, quantitative real-time PCR (MQPCR) could be used to detect the haploinsufficiency characteristic of 22q11.2 DS. A retrospective blinded study was performed on 382 subjects who had undergone congenital heart surgery. MQPCR was performed with a probe localized to the TBX1 gene on human chromosome 22, a gene typically deleted in 22q11.2 DS. Cycle threshold (C(t)) was used to calculate the relative gene copy number (rGCN). Confirmation analysis was performed with the Affymetrix 6.0 Genome-Wide SNP Array. With MQPCR, 361 subjects were identified as nondeleted with an rGCN near 1.0 and 21 subjects were identified as deleted with an rGCN near 0.5, indicative of a hemizygous deletion. The sensitivity (21/21) and specificity (361/361) of MQPCR to detect 22q11.2 deletions was 100% at an rGCN value drawn at 0.7. One of 21 subjects with a prior clinical (not genetically confirmed) DGS1 diagnosis was found not to carry the deletion, while another subject, not previously identified as DGS1, was detected as deleted and subsequently confirmed via microarray. The MQPCR assay is a rapid, inexpensive, sensitive, and specific assay that can be used to screen for 22q11.2 deletion syndrome. The assay is readily adaptable to high throughput.

Cardiovascular anomalies associated with chromosome 22q11.2 deletion syndrome

Cardiovascular anomalies are present in 80% of neonates with 22q11.2 deletion syndrome. Three genes in chromosome 22q11.2 (TBX1, CRKL, and ERK2) have been identified whose haploinsufficiency causes dysfunction of the neural crest cell and anterior heart field and anomalies of 22q11.2 deletion syndrome. The most common diseases are conotruncal anomalies, which include tetralogy of Fallot (TF), TF with pulmonary atresia, truncus arteriosus, and interrupted aortic arch. A high prevalence of the deletion is noted in patients with TF with absent pulmonary valve, TF associated with pulmonary atresia and major aortopulmonary collateral arteries, truncus arteriosus, and type B interruption of aortic arch. Right aortic arch, aberrant subclavian artery, cervical origin of the subclavian artery, crossing pulmonary arteries, and major aortopulmonary collateral arteries are frequently associated with cardiovascular anomalies associated with 22q11.2 deletion syndrome. Virtually every type of congenital heart defect has been described early in the context of a 22q11.2 deletion. In conclusion, conotruncal anomaly associated with aortic arch and ductus arteriosus anomalies should increase the suspicion of 22q11.2 deletion.

Mutations in VEGFA are associated with congenital left ventricular outflow tract obstruction

Left ventricular outflow tract obstruction (LVOTO) comprises a spectrum of stenotic lesions. Previous studies have shown that the vascular endothelial growth factor (VEGF) signaling system plays a critical role in cardiac cushion formation, vasculogenesis, and angiogenesis. We hypothesize that VEGFA may be a potential candidate gene associated with the spectrum of LVOTO lesions. However, it remains unclear whether the VEGFA gene is responsible for the development of LVOTO malformations. In this study, we identified three exon mutations in the VEGFA gene in three of 192 nonsyndromic LVOTO patients, and the overall mutation frequency was 1.6% (3/192). The c.454C>T (p.Arg152X) nonsense mutation and c.19_22dupGACA (p.Thr8ArgfsX78) internal tandem duplication mutation each introduced a premature stop codon and are predicted to produce a truncated VEGFA protein. The c.998G>A missense mutation changes a highly conserved arginine to a glutamine at residue 333 (p.Arg333Gln). These mutations were carried by some family members, and average penetrance was 33.3%. The present study suggests, for the first time to our knowledge, that VEGFA mutations may be associated with congenital LVOTO malformations. We provide evidence that LVOTO is likely oligogenic.

22q11 deletion syndrome: a role for TBX1 in pharyngeal and cardiovascular development

Tbx1 is a member of the Tbox family of binding domain transcription factors. TBX1 maps within the region of 22q11 deleted in humans with DiGeorge or velocardiofacial syndrome. Mice haploinsufficient for Tbx1 have phenotypes that recapitulate major features of the syndrome, notably abnormal growth and remodelling of the pharyngeal arch arteries. The Tbx1 haploinsufficiency phenotype is modified by genetic background and by mutations in putative downstream targets. Homozygous null mutations of Tbx1 have more severe defects including failure of outflow tract septation, and absence of the caudal pharyngeal arches. Tbx1 is a transcriptional activator, and loss of this activity has been linked to alterations in the expression of various genes involved in cardiovascular morphogenesis. In particular, Fgf and retinoic acid signalling are dysregulated in Tbx1 mutants. This article summarises the tissue specific and temporal requirements for Tbx1, and attempts to synthesis what is know about the developmental pathways under its control.

Fetal interrupted aortic arch: 2D-4D echocardiography, associations and outcome

OBJECTIVES

To analyze fetal two-dimensional (2D) echocardiographic characteristics of interrupted aortic arch (IAA) and its different types, to explore whether the use of 4D ultrasound with B-flow imaging and spatiotemporal image correlation (STIC) can improve prenatal diagnostic accuracy, and to describe associations and outcome.

METHODS

The study comprised IAA fetuses examined exclusively by 2D conventional echocardiography during the period from 1994 to 2003, and those identified by conventional echocardiography and examined further by 4D ultrasound with B-flow imaging and STIC during the period January 2004 to July 2008, identified among fetuses examined at two referral centers for congenital heart defects (CHD). Postnatal follow-up was available in all cases. Karyotyping and fluorescent in-situ hybridization (FISH) analysis for the DiGeorge critical region (22q11.2) were performed in all cases.

RESULTS

Twenty-two cases of isolated IAA (15 Type B and seven Type A, seven and three of which, respectively, underwent B-flow imaging and STIC) were detected among 2520 cases of fetal CHD. In seven of the 15 Type B cases, a right subclavian artery arose anomalously (ARSA). 2D echocardiography failed to distinguish the type of IAA in only two cases and the ARSA in five of the seven cases. B-flow imaging and STIC successfully identified IAA types in all 10 cases examined and clearly visualized the origin and course of the ARSA, including cervical ones. FISH detected 22q11.2 microdeletion in 10 of the 15 Type B cases and an unusual association with Type A in one of the seven cases. Fetal/neonatal outcome included: eight terminations of pregnancy, one intrauterine death and four postoperative deaths in the neonatal period, and nine neonates were alive after surgery at a mean follow-up time of 58 months (range, 4 months-13 years).

CONCLUSION

Our results confirm the feasibility of prenatal characterization of IAA and its different types based on 2D echocardiographic examination, albeit with some limitations in the thorough assessment. 4D ultrasound with B-flow imaging and STIC can apparently facilitate visualization and detailed examination of the anatomical features of the IAA types, including visualization of the neck vessels, thus supplying additional information with respect to 2D sonography. As for the known association with microdeletion 22q11.2, our data indicate that Types A and B are distinct, there being a close association only with IAA Type B.

Great vessel development requires biallelic expression of Chd7 and Tbx1 in pharyngeal ectoderm in mice

Aortic arch artery patterning defects account for approximately 20% of congenital cardiovascular malformations and are observed frequently in velocardiofacial syndrome (VCFS). In the current study, we screened for chromosome rearrangements in patients suspected of VCFS, but who lacked a 22q11 deletion or TBX1 mutation. One individual displayed hemizygous CHD7, which encodes a chromodomain protein. CHD7 haploinsufficiency is the major cause of coloboma, heart defect, atresia choanae, retarded growth and development, genital hypoplasia, and ear anomalies/deafness (CHARGE) syndrome, but this patient lacked the major diagnostic features of coloboma and choanal atresia. Because a subset of CHARGE cases also display 22q11 deletions, we explored the embryological relationship between CHARGE and VCSF using mouse models. The hallmark of Tbx1 haploinsufficiency is hypo/aplasia of the fourth pharyngeal arch artery (PAA) at E10.5. Identical malformations were observed in Chd7 heterozygotes, with resulting aortic arch interruption at later stages. Other than Tbx1, Chd7 is the only gene reported to affect fourth PAA development by haploinsufficiency. Moreover, Tbx1+/-;Chd7+/- double heterozygotes demonstrated a synergistic interaction during fourth PAA, thymus, and ear morphogenesis. We could not rescue PAA morphogenesis by restoring neural crest Chd7 expression. Rather, biallelic expression of Chd7 and Tbx1 in the pharyngeal ectoderm was required for normal PAA development.

Chromosomal abnormalities among children born with conotruncal cardiac defects

BACKGROUND

Conotruncal heart defects compose 25% to 30% of nonsyndromic congenital heart defects. This study describes the frequency of chromosome abnormalities and microdeletion of 22q11 associated among infants and fetuses delivered with conotruncal heart malformations.

METHODS

From a population base of 974,579 infants/fetuses delivered, 622 California infants/fetuses were ascertained with a defect of aortopulmonary septation. Infants whose primary cardiac defect was tetralogy of Fallot (n = 296) or d-transposition of the great arteries (n = 189) were screened for microdeletion of 22q11.

RESULTS

Of the infants who had routine karyotypes, 5% had chromosomal abnormalities, including four with extra sex chromosomes. Thirty infants had chromosome 22q11 microdeletions, providing a cause for 10% of infants whose primary defect was tetralogy of Fallot. Right aortic arch, abnormal branching patterns of the major arteries arising from the thoracic aorta, and pulmonary artery abnormalities were observed more frequently among infants with tetralogy of Fallot caused by 22q11 microdeletion.

CONCLUSIONS

We found an unusual number of infants with an extra sex chromosome and a conotruncal defect. Infants with tetralogy of Fallot owing to 22q11 microdeletion showed more associated vascular anomalies than infants with tetralogy without a 22q11 microdeletion. Although these associated vascular anomalies provide clues as to which infants with tetralogy of Fallot are more likely to carry the microdeletion, the overall risk of 10% among infants with tetralogy of Fallot warrants chromosome analysis and fluorescent in situ hybridization (FISH) testing routinely, which may be supplanted by genome-wide copy number testing as it becomes more widely utilized.

Atresia of the aortic arch, with a collateral artery from the right subclavian artery supplying the descending aorta

An infant of 2 months presented with absence of the femoral pulses, albeit with no signs of cardiac failure. The mother was known to have ingested Valproate during pregnancy. Echocardiography showed the aortic arch to be interrupted between the left common carotid and left subclavian arteries, so-called type B interruption, in the setting of an intact ventricular septum. Angiography, and multislice computed tomography, revealed the descending aorta to be supplied by a collateral artery originating from the right subclavian artery. Corrective surgery was successfully performed, but revealed an atretic segment of the arch at the site of interruption of flow.

Multislice CT angiography of interrupted aortic arch

Interrupted aortic arch (IAA) is defined as complete luminal and anatomic discontinuity between the ascending and descending aorta. Because almost all patients with IAA become critically ill during the neonatal period, they should undergo urgent corrective surgery. This clinical urgency necessitates a fast and accurate noninvasive diagnostic method. Although echocardiography remains the primary imaging tool for this purpose, it is not always sufficient for planning surgical correction of IAA, principally due to a limited acoustic window and the inexperience of imagers. In this context, multislice CT angiography is regarded as an appropriate imaging technique complementary to echocardiography because it is fast, accurate, and objective for the diagnosis of IAA. In this article we describe what cardiac radiologists should know about IAA in their clinical practice, including clinicopathological features, CT features with contemporary surgical methods and postoperative complications, and differentiation from coarctation of the aorta and aortic arch atresia.

Genetic basis for congenital heart defects: current knowledge: a scientific statement from the American Heart Association Congenital Cardiac Defects Committee, Council on Cardiovascular Disease in the Young: endorsed by the American Academy of Pediatrics

The intent of this review is to provide the clinician with a summary of what is currently known about the contribution of genetics to the origin of congenital heart disease. Techniques are discussed to evaluate children with heart disease for genetic alterations. Many of these techniques are now available on a clinical basis. Information on the genetic and clinical evaluation of children with cardiac disease is presented, and several tables have been constructed to aid the clinician in the assessment of children with different types of heart disease. Genetic algorithms for cardiac defects have been constructed and are available in an appendix. It is anticipated that this summary will update a wide range of medical personnel, including pediatric cardiologists and pediatricians, adult cardiologists, internists, obstetricians, nurses, and thoracic surgeons, about the genetic aspects of congenital heart disease and will encourage an interdisciplinary approach to the child and adult with congenital heart disease.

Cardiac Registry screening for DiGeorge Critical Region deletion using loss of heterozygosity analysis

DiGeorge (DGS), velocardiofacial, and conotruncal anomaly face syndromes comprise a phenotypic spectrum that is associated with a submicroscopic 22q11.2 deletion in the majority of cases. These syndromes variably express complex congenital heart disease, cellular immune deficits, hypocalcemia, craniofacial anomalies, and learning disabilities. This retrospective study correlates the presence of a deletion in this region with autopsy and clinical findings in a cohort of patients selected from the Cardiac Registry at Boston Children's Hospital. DNA was extracted from formalin-fixed paraffin-embedded cardiac tissue sampled from 189 patients with conotruncal anomalies. Polymerase chain reaction (PCR) was performed using 4 fluorescently labeled oligonucleotide primer pairs for unique short tandem repeat polymorphisms in the DGS critical region. The PCR products were analyzed for loss of heterozygosity (LOH), and a deletion was assumed when at least 3 consecutive loci demonstrated homozygosity. Of the 189 cases, 16 (8%) met our criteria for LOH and were assumed to have a deletion. These patients included 6 (35%) of 17 patients diagnosed clinically with DGS prior to death. Of the 10 non-DGS patients with LOH, 4 had aortic atresia and 3 had tetralogy of Fallot, both frequently seen in DGS. Polymerase chain reaction is a useful screening alternative to fluorescence in situ hydridization for detecting 22q11.2 deletions in archived tissue samples. This study identified a probable deletion in a subset of cases from a cardiac registry with cardiac defects associated with the DGS phenotype.

Tbx1 expression in pharyngeal epithelia is necessary for pharyngeal arch artery development

During embryonic life, the initially paired pharyngeal arch arteries (PAAs) follow a precisely orchestrated program of persistence and regression that leads to the formation of the mature aortic arch and great vessels. When this program fails, specific cardiovascular defects arise that may be life threatening or mild, according to the identity of the affected artery. Fourth PAA-derived cardiovascular defects occur commonly in DiGeorge syndrome and velocardiofacial syndrome (22q11DS), and in Tbx1(+/-) mice that model the 22q11DS cardiovascular phenotype. Tbx1 is expressed in pharyngeal mesoderm, endoderm and ectoderm, and, in addition, we show that it is expressed in precursors of the endothelial cells that line the PAAs, thus expanding the number of tissues in which Tbx1 is potentially required for fourth PAA development. In this study, we have used cell fate mapping and tissue-specific gene deletion, driven by six different Cre lines, to explore Tbx1 gene-dosage requirements in the embryonic pharynx for fourth PAA development. Through this approach, we have resolved the spatial requirements for Tbx1 in this process, and we show pharyngeal epithelia to be a critical tissue. We also thereby demonstrate conclusively that the role of Tbx1 in fourth PAA development is cell non-autonomous.

Disturbed morphogenesis of cardiac outflow tract and increased rate of aortic arch anomalies in the offspring of diabetic rats

BACKGROUND

Maternal diabetes (MD) is a risk factor for offspring to develop cardiovascular anomalies; this is of growing clinical concern since the number of women in childbearing age with compromised glucose homeostasis is increasing. Hyperglycemia abrogates cardiovascular development in vitro; however, a link to cardiovascular defects in diabetic offspring remains to be investigated.

METHODS

We have studied cardiovascular development in offspring of MD rats by examining serial histological sections of GD 12.0-18.0 offspring. Development of pharyngeal arch artery malformations was analyzed and related to intracardiac anomalies.

RESULTS

Pharyngeal arch artery and intracardiac defects were present in 27 of 37 MD GD 13.0-18.0 offspring. Early sixth arch arteries showed abrogated arteriogenesis, whereas fourth arch artery defects developed as a result of abnormal remodeling. Morphometrical analysis showed increased apoptosis in regressing artery segments and reduced apoptosis in persisting artery segments. Double outlet right ventricle with infundibular stenosis (tetralogy of Fallot) was predominantly found in combination with sixth artery defects and pulmonary atresia. As confirmed by morphometric analysis and three-dimensional (3D)-reconstructions, outflow tract defects coincided with endocardial cushion hypoplasia. Cases with teratology of Fallot additionally showed a shorter outflow tract. No relation with apoptosis or disturbed neural crest cell migration was found.

CONCLUSIONS

Our data uniquely demonstrate mechanistic differences involved in the development of sixth and fourth artery anomalies. Whereas increased apoptosis induces fourth artery anomalies, pulmonary outflow obstruction abrogates sixth artery differentiation independent of apoptosis. The model presented allows analysis of diabetic conditions on cardiovascular development in vivo, essential for elucidating this teratology.

DiGeorge anomaly in a patient with isochromosome 18p born to a diabetic mother

The DiGeorge anomaly (DGA) is an etiologically heterogeneous developmental field defect in which cardiovascular malformations, hypocalcemia, thymic hypoplasia, and characteristic dysmorphisms are major clinical features. The 22q11.2 deletion is the most common single etiology of DGA, although a number of other chromosomal abnormalities and teratogens, including maternal diabetes, have been implicated as well. We present a patient, born to a diabetic mother, with interrupted aortic arch type B (IAA-B), neonatal hypocalcemia, thymic hypoplasia, and dysmorphic features including microcephaly, thick, overfolded helices, and anteriorly-placed anus. Cytogenetic studies showed the presence of a marker chromosome, identified by fluorescence in-situ hybridization (FISH) as an isochromosome 18p [i(18p)]. We did not detect a 22q11.2 deletion by FISH using a cosmid probe corresponding to locus D22S75. The patient is the first example of either DGA or IAA-B in a patient with i(18p). We review the genetic abnormalities associated with DGA, and discuss the potential contributions of maternal diabetes and i(18p) in our patient.

Transforming Growth Factor β–SMAD2 Signaling Regulates Aortic Arch Innervation and Development

Aortic arch interruptions in humans and animal models are mainly caused by aberrant development of the fourth pharyngeal arch artery. Little is known about the maturation of this vessel during normal and abnormal development, which is the subject of this study. Tgfbeta2 knockout mice that present with fourth artery defects have been associated with defective neural crest cell migration. In this study, we concentrated on pharyngeal arch artery development during developmental days 12.5 to 18.5, focusing on neural crest cell migration using a Wnt1-Cre by R26R neural crest cell reporter mouse. Fourth arch artery maturation was studied with antibodies directed against smooth muscle alpha-actin and neural NCAM-1 and RMO-270. For diminished transforming growth factor beta (TGF-beta) signaling, SMAD2 and fibronectin have been analyzed. Neural crest migration and differentiation into smooth muscle cells is unaltered in mutants, regardless of the cardiovascular defect found; however, innervation of the fourth arch artery is affected. Absent staining for nuclear SMAD2, NCAM-1, and RMO-270 in the fourth artery in mutant coincides with severe defects of this segment. Likewise, fibronectin expression is diminished in these cases. From these data we conclude the following: (1) neural crest cell migration is not a common denominator in cardiovascular defects of Tgfbeta2-/- mice; (2) fourth arch artery maturation is a complex process involving innervation; and (3) TGF-beta2 depletion diminishes SMAD2-signaling in the fourth arch artery and coincides with reduced vascular NCAM-1 expression and neural innervation of this artery. We hypothesize that disturbed maturation of the fourth pharyngeal arch artery, and especially abrogated vascular innervation, will result in fourth arch interruptions.

Transbrachial stenting of a critical ostial arteria lusoria stenosis

PURPOSE

To report the endovascular treatment of a critical ostial stenosis in an aberrant right subclavian artery (ARSA), a rare embryologic anomaly of the aortic arch.

CASE REPORT

A 76-year-old woman presented with acute ischemia of her right forearm. Her medical history was notable for hyperlipidemia but otherwise negative for risk factors of atherosclerosis. Color-coded duplex ultrasonography revealed occlusion of the distal brachial and cubital artery, poststenotic flow in the distal subclavian and axillary artery, and reversal of flow in the right vertebral artery. The patient underwent contrast-enhanced multidetector computed tomography of the thorax, which revealed the presence of an ARSA with a calcified, high-grade ostial stenosis. The lesion was successfully stented via a brachial access.

CONCLUSIONS

Endovascular treatment of an ostial stenosis in an aberrant right subclavian artery is feasible by means of transbrachial approach.

Congenital heart disease and aneuploidy

Congenital heart disease (CHD) is one of the commonest prenatal diagnoses made on routine ultrasound screening. Overall, up to 33% of CHD are associated with fetal aneuploidy. However, some specific cardiac lesions have a significantly greater association with particular chromosomal abnormalities. The majority of fetuses with CHD and aneuploidy also have extra-cardiac anomalies and are best managed by a multidisciplinary team where the management and prognosis of the cardiac defect can be discussed in the context of the baby as a whole. It is therefore important for clinicians involved in the management of fetuses with CHD to be aware of the association of aneuploidy as well as the prognosis and management of these cases, so that they can appropriately counsel the parents. In this chapter, we review the frequency and types of aneuploidy associated with the commonly diagnosed CHD and discuss their management.

Vasomotor instability in neonates with chromosome 22q11 deletion syndrome

Approximately 70% of individuals with chromosome 22q11 deletion syndrome (22q11DS) have congenital heart defects. A host of other vascular problems in these patients, such as tortuous carotid arteries, Raynaud's phenomenon, unexplained hypotension, hypertension, and hypothermia, raise the possibility that there may be abnormal autonomic regulation of the vascular system. So far, however, there has been no formal report of autonomic dysfunction in patients with 22q11 deletion. We present two infants with 22q11DS, who had profound hypotension after uncomplicated surgeries for congenital heart disease. The hypotension was not responsive to vasopressor treatment (and extracorporeal membrane oxygenation in one infant) and resulted in death, due to multiorgan system failure. Obvious causes, such as poor cardiac contractility, prolonged circulatory arrest, neurological abnormality, sepsis and blood loss were excluded. On autopsy, no abnormalities were found that could explain the hypotension. We hypothesize that these infants died of severe hypotension due to abnormal vascular tone and that this is a variable feature in individuals with 22q11 deletion. The autonomic nervous system, which is responsible for the regulation of vasomotor tone, may be variably affected in 22q11DS. This could have implications for the surgical management of patients with 22q11DS. Further studies on this topic would establish or refute the association between 22q11DS and dysautonomia.

22q11 deletions in fetuses with malformations of the outflow tracts or interruption of the aortic arch: impact of additional ultrasound signs

OBJECTIVES

One hundred and forty-one consecutive cases of malformations of the outflow tracts or interrupted aortic arch (IAA), detected by fetal echocardiography, underwent detailed anatomy scan, karyotyping and fluorescence in situ hybridization analysis (FISH) to detect the prevalence of 22q11 microdeletion and to evaluate neonatal clinical findings and outcome according to the presence of the genetic defect. Then, we sought to investigate whether some prenatal ultrasound findings could help identify fetuses at higher risk of carrying the 22q11 microdeletion.

METHODS

Echocardiography and FISH for the DiGeorge critical region (22q11) were performed in all cases.

RESULTS

22q11 microdeletion was detected in 28 of 141 fetuses (19.8%). Intrauterine growth restriction (IUGR) appeared to be associated with the worst prognosis, being present in 2/2 intrauterine fetal deaths and 5/6 post-natal deaths. IUGR, additional aortic arch anomalies and thymic hypo/aplasia were significantly more frequent in fetuses with 22q11 microdeletion (p=0.011, 0.011 and <0.0001, respectively). Prenatal ultrasound thymus examination, performed on the last 84 fetuses, showed 75% sensitivity and 94% specificity. The combination of 2 predictors, namely, thymus defects and IUGR associated with additional aortic arch anomalies reached more than 90% sensitivity and 100% specificity.

CONCLUSIONS

Our study demonstrates that 22q11 microdeletion occurs in 20% of malformations of the outflow tracts and IAA type B, as detected in utero, and that this association is significantly predicted by the presence of associated ultrasound findings: thymic hypo/aplasia, IUGR and additional aortic arch anomalies. The feasibility of a correct prenatal diagnosis should enable clinicians to provide the couple with further informative counselling and to plan adequate post-natal medical interventions.

The Jing-Mai connections of the heart

BACKGROUND

The Jing-Mai (variously translated as the Channel, Vessel or Meridians), as described by traditional Chinese medicine, probably exists and has represented the connections between various parts of human body during embryonic development. According to the Chinese theories, there are 14 major Jing-Mai within the human body, of which four are directly connected with the Heart.

METHODS

The described paths of the four Jing-Mai were compared with features of congenital syndromes involving particular types of congenital heart defects.

RESULTS

Specific correlation seem to exist between such four Jing-Mai and known developmental mechanisms underlying various congenital heart defects: the Kidney Jing-Mai-ectomesenchymal tissue migration abnormalities; the Spleen Jing-Mai-situs and looping defects; the Heart Jing-Mai-abnormal cell death; the Small Intestine Jing-Mai (and the Heart Jing-Mai)-extracellular matrix anomalies.

CONCLUSIONS

The Chinese theories seem to provide some intriguing insights into the pathogeneses of congenital heart defects. The Jing-Mai seems to distinguish from, but nevertheless have a close relationship with the blood vessels. Utilization of the Jing-Mai will probably enable a better understanding and development of new treatments for cardiovascular diseases.

Prenatal diagnosis of interruption of the aortic arch and its association with deletion of chromosome 22q11

OBJECTIVES

Differentiation of interruption of the aortic arch (IAA) type A from type B by prenatal echocardiography is possible but difficult. We report nine consecutive cases of the prenatal detection of IAA and evaluate the feasibility of making a correct prenatal diagnosis with fetal echocardiography. The incidence of 22q11 microdeletion in our series, detected using fluorescent in situ hybridization (FISH) analysis, was determined.

METHODS

Echocardiography and FISH for the DiGeorge critical region (22q11) were performed in all cases. The findings were confirmed by autopsy (three cases) or at postnatal surgery (six cases).

RESULTS

On fetal echocardiography we identified six type B cases and three type A. FISH detected microdeletions in 22q11 in five of nine fetuses (four type B cases and an unusual association with type A in one case).

CONCLUSIONS

Our report confirms the feasibility of making a correct prenatal diagnosis of IAA and its different types, based on echocardiographic examination. Furthermore our data are consistent with previous reports indicating that type A and type B are distinct entities. In more than 50% of fetuses with IAA type B, 22q11 microdeletion and DiGeorge or velo-cardio-facial syndromes may be expected. IAA type A is not commonly associated with 22q11 hemizygosity.