NODAL variants are associated with a continuum of laterality defects from simple D-transposition of the great arteries to heterotaxy

BACKGROUND

NODAL signaling plays a critical role in embryonic patterning and heart development in vertebrates. Genetic variants resulting in perturbations of the TGF-β/NODAL signaling pathway have reproducibly been shown to cause laterality defects in humans. To further explore this association and improve genetic diagnosis, the study aims to identify and characterize a broader range of NODAL variants in a large number of individuals with laterality defects.

METHODS

We re-analyzed a cohort of 321 proband-only exomes of individuals with clinically diagnosed laterality congenital heart disease (CHD) using family-based, rare variant genomic analyses. To this cohort we added 12 affected subjects with known NODAL variants and CHD from institutional research and clinical cohorts to investigate an allelic series. For those with candidate contributory variants, variant allele confirmation and segregation analysis were studied by Sanger sequencing in available family members. Array comparative genomic hybridization and droplet digital PCR were utilized for copy number variants (CNV) validation and characterization. We performed Human Phenotype Ontology (HPO)-based quantitative phenotypic analyses to dissect allele-specific phenotypic differences.

RESULTS

Missense, nonsense, splice site, indels, and/or structural variants of NODAL were identified as potential causes of heterotaxy and other laterality defects in 33 CHD cases. We describe a recurrent complex indel variant for which the nucleic acid secondary structure predictions implicate secondary structure mutagenesis as a possible mechanism for formation. We identified two CNV deletion alleles spanning NODAL in two unrelated CHD cases. Furthermore, 17 CHD individuals were found (16/17 with known Hispanic ancestry) to have the c.778G > A:p.G260R NODAL missense variant which we propose reclassification from variant of uncertain significance (VUS) to likely pathogenic. Quantitative HPO-based analyses of the observed clinical phenotype for all cases with p.G260R variation, including heterozygous, homozygous, and compound heterozygous cases, reveal clustering of individuals with biallelic variation. This finding provides evidence for a genotypic-phenotypic correlation and an allele-specific gene dosage model.

CONCLUSION

Our data further support a role for rare deleterious variants in NODAL as a cause for sporadic human laterality defects, expand the repertoire of observed anatomical complexity of potential cardiovascular anomalies, and implicate an allele specific gene dosage model.

Pkd1l1-deficiency drives biliary atresia through ciliary dysfunction in biliary epithelial cells

BACKGROUND & AIMS

Syndromic biliary atresia is a cholangiopathy characterized by fibro-obliterative changes in the extrahepatic bile duct (EHBD) and congenital malformations including laterality defects. The etiology remains elusive and faithful animal models are lacking. Genetic syndromes provide important clues regarding the pathogenic mechanisms underlying the disease. We investigated the role of the gene Pkd1l1 in the pathophysiology of syndromic biliary atresia.

METHODS

Constitutive and conditional Pkd1l1 knockout mice were generated to explore genetic pathology as a cause of syndromic biliary atresia. We investigated congenital malformations, EHBD and liver pathology, EHBD gene expression, and biliary epithelial cell turnover. Biliary drainage was functionally assessed with cholangiography. Histology and serum chemistries were assessed after DDC (3,5-diethoxycarbony l-1,4-dihydrocollidine) diet treatment and inhibition of the ciliary signaling effector GLI1.

RESULTS

Pkd1l1-deficient mice exhibited congenital anomalies including malrotation and heterotaxy. Pkd1l1-deficient EHBDs were hypertrophic and fibrotic. Pkd1l1-deficient EHBDs were patent but displayed delayed biliary drainage. Pkd1l1-deficient livers exhibited ductular reaction and periportal fibrosis. After DDC treatment, Pkd1l1-deficient mice exhibited EHBD obstruction and advanced liver fibrosis. Pkd1l1-deficient mice had increased expression of fibrosis and extracellular matrix remodeling genes (Tgfα, Cdkn1a, Hb-egf, Fgfr3, Pdgfc, Mmp12, and Mmp15) and decreased expression of genes mediating ciliary signaling (Gli1, Gli2, Ptch1, and Ptch2). Primary cilia were reduced on biliary epithelial cells and altered expression of ciliogenesis genes occurred in Pkd1l1-deficient mice. Small molecule inhibition of the ciliary signaling effector GLI1 with Gant61 recapitulated Pkd1l1-deficiency.

CONCLUSIONS

Pkd1l1 loss causes both laterality defects and fibro-proliferative EHBD transformation through disrupted ciliary signaling, phenocopying syndromic biliary atresia. Pkd1l1-deficient mice function as an authentic genetic model for study of the pathogenesis of biliary atresia.

IMPACT AND IMPLICATIONS

The syndromic form of biliary atresia is characterized by fibro-obliteration of extrahepatic bile ducts and is often accompanied by laterality defects. The etiology is unknown, but Pkd1l1 was identified as a potential genetic candidate for syndromic biliary atresia. We found that loss of the ciliary gene Pkd1l1 contributes to hepatobiliary pathology in biliary atresia, exhibited by bile duct hypertrophy, reduced biliary drainage, and liver fibrosis in Pkd1l1-deficient mice. Pkd1l1-deficient mice serve as a genetic model of biliary atresia and reveal ciliopathy as an etiology of biliary atresia. This model will help scientists uncover new therapeutic approaches for patients with biliary atresia, while pediatric hepatologists should validate the diagnostic utility of PKD1L1 variants.

CFAP45, a heterotaxy and congenital heart disease gene, affects cilia stability

Congenital heart disease (CHD) is the most common and lethal birth defect, affecting 1.3 million individuals worldwide. During early embryogenesis, errors in Left-Right (LR) patterning called Heterotaxy (Htx) can lead to severe CHD. Many of the genetic underpinnings of Htx/CHD remain unknown. In analyzing a family with Htx/CHD using whole-exome sequencing, we identified a homozygous recessive missense mutation in CFAP45 in two affected siblings. CFAP45 belongs to the coiled-coil domain-containing protein family, and its role in development is emerging. When we depleted Cfap45 in frog embryos, we detected abnormalities in cardiac looping and global markers of LR patterning, recapitulating the patient's heterotaxy phenotype. In vertebrates, laterality is broken at the Left-Right Organizer (LRO) by motile monocilia that generate leftward fluid flow. When we analyzed the LRO in embryos depleted of Cfap45, we discovered "bulges" within the cilia of these monociliated cells. In addition, epidermal multiciliated cells lost cilia with Cfap45 depletion. Via live confocal imaging, we found that Cfap45 localizes in a punctate but static position within the ciliary axoneme, and depletion leads to loss of cilia stability and eventual detachment from the cell's apical surface. This work demonstrates that in Xenopus, Cfap45 is required to sustain cilia stability in multiciliated and monociliated cells, providing a plausible mechanism for its role in heterotaxy and congenital heart disease.

Biallelic DAW1 variants cause a motile ciliopathy characterized by laterality defects and subtle ciliary beating abnormalities

PURPOSE

The clinical spectrum of motile ciliopathies includes laterality defects, hydrocephalus, and infertility as well as primary ciliary dyskinesia when impaired mucociliary clearance results in otosinopulmonary disease. Importantly, approximately 30% of patients with primary ciliary dyskinesia lack a genetic diagnosis.

METHODS

Clinical, genomic, biochemical, and functional studies were performed alongside in vivo modeling of DAW1 variants.

RESULTS

In this study, we identified biallelic DAW1 variants associated with laterality defects and respiratory symptoms compatible with motile cilia dysfunction. In early mouse embryos, we showed that Daw1 expression is limited to distal, motile ciliated cells of the node, consistent with a role in left-right patterning. daw1 mutant zebrafish exhibited reduced cilia motility and left-right patterning defects, including cardiac looping abnormalities. Importantly, these defects were rescued by wild-type, but not mutant daw1, gene expression. In addition, pathogenic DAW1 missense variants displayed reduced protein stability, whereas DAW1 loss-of-function was associated with distal type 2 outer dynein arm assembly defects involving axonemal respiratory cilia proteins, explaining the reduced cilia-induced fluid flow in particle tracking velocimetry experiments.

CONCLUSION

Our data define biallelic DAW1 variants as a cause of human motile ciliopathy and determine that the disease mechanism involves motile cilia dysfunction, explaining the ciliary beating defects observed in affected individuals.

Biallelic mutations of TTC12 and TTC21B were identified in Chinese patients with multisystem ciliopathy syndromes

Background

Abnormalities in cilia ultrastructure and function lead to a range of human phenotypes termed ciliopathies. Many tetratricopeptide repeat domain (TTC) family members have been reported to play critical roles in cilium organization and function.

Results

Here, we describe five unrelated family trios with multisystem ciliopathy syndromes, including situs abnormality, complex congenital heart disease, nephronophthisis or neonatal cholestasis. Through whole-exome sequencing and Sanger sequencing confirmation, we identified compound heterozygous mutations of TTC12 and TTC21B in six affected individuals of Chinese origin. These nonsynonymous mutations affected highly conserved residues and were consistently predicted to be pathogenic. Furthermore, ex vivo cDNA amplification demonstrated that homozygous c.1464 + 2 T > C of TTC12 would cause a whole exon 16 skipping. Both mRNA and protein levels of TTC12 were significantly downregulated in the cells derived from the patient carrying TTC12 mutation c.1464 + 2 T > C by real-time qPCR and immunofluorescence assays when compared with two healthy controls. Transmission electron microscopy analysis further identified ultrastructural defects of the inner dynein arms in this patient. Finally, the effect of TTC12 deficiency on cardiac LR patterning was recapitulated by employing a morpholino-mediated knockdown of ttc12 in zebrafish.

Conclusions

To the best of our knowledge, this is the first study reporting the association between TTC12 variants and ciliopathies in a Chinese population. In addition to nephronophthisis and laterality defects, our findings demonstrated that TTC21B should also be considered a candidate gene for biliary ciliopathy, such as TTC26, which further expands the phenotypic spectrum of TTC21B deficiency in humans.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40246-022-00421-z.

Intestinal microbiome changes in an infant with right atrial isomerism and recurrent necrotizing enterocolitis: A case report and review of literature

BACKGROUND

Necrotizing enterocolitis (NEC) is a multifactorial disease that predominantly affects premature neonates. Intestinal dysbiosis plays a critical role in NEC pathogenesis in premature neonates. The main risk factor for NEC in term infants is mesenteric hypoperfusion associated with ductal-dependent congenital heart disease (CHD) that eventually leads to intestinal ischemia. The incidence of NEC in neonates with critical CHD is 6.8%-13%. However, the role of the intestinal microbiome in NEC pathogenesis in infants with ductal-dependent CHD remains unclear.

CASE SUMMARY

A male term neonate with right atrial isomerism underwent modified Blalock-Taussig shunt placement on the 14^th day of life and had persistent mesenteric hypoperfusion after surgery. The patient had episodes of NEC stage IIA on the 1^st and 28^th days after cardiac surgery. Fecal microbial composition was analyzed before and after cardiac surgery by sequencing region V4 of the 16S rRNA gene. Before surgery, species belonging to genera Veillonella and Clostridia and class Gammaproteobacteria were detected, Bifidobacteriaceae showed a low abundance. The first NEC episode was associated with postoperative hemodynamic instability, intestinal ischemia-reperfusion injury during cardiopulmonary bypass, and a high abundance of Clostridium paraputrificum (Clostridium sensu stricto I) (56.1%). Antibacterial therapy after the first NEC episode resulted in increased abundance of Gammaproteobacteria, decreased abundance of Firmicutes, and low alpha diversity. These changes in the microbial composition promoted the growth of Clostridium sensu stricto I (72.0%) before the second NEC episode.

CONCLUSION

A high abundance of Clostridium sensu stricto I and mesenteric hypoperfusion may have contributed to NEC in the present case.

A multi-disciplinary, comprehensive approach to management of children with heterotaxy

Heterotaxy (HTX) is a rare condition of abnormal thoraco-abdominal organ arrangement across the left-right axis of the body. The pathogenesis of HTX includes a derangement of the complex signaling at the left-right organizer early in embryogenesis involving motile and non-motile cilia. It can be inherited as a single-gene disorder, a phenotypic feature of a known genetic syndrome or without any clear genetic etiology. Most patients with HTX have complex cardiovascular malformations requiring surgical intervention. Surgical risks are relatively high due to several serious comorbidities often seen in patients with HTX. Asplenia or functional hyposplenism significantly increase the risk for sepsis and therefore require antimicrobial prophylaxis and immediate medical attention with fever. Intestinal rotation abnormalities are common among patients with HTX, although volvulus is rare and surgical correction carries substantial risk. While routine screening for intestinal malrotation is not recommended, providers and families should promptly address symptoms concerning for volvulus and biliary atresia, another serious morbidity more common among patients with HTX. Many patients with HTX have chronic lung disease and should be screened for primary ciliary dyskinesia, a condition of respiratory cilia impairment leading to bronchiectasis. Mental health and neurodevelopmental conditions need to be carefully considered among this population of patients living with a substantial medical burden. Optimal care of children with HTX requires a cohesive team of primary care providers and experienced subspecialists collaborating to provide compassionate, standardized and evidence-based care. In this statement, subspecialty experts experienced in HTX care and research collaborated to provide expert- and evidence-based suggestions addressing the numerous medical issues affecting children living with HTX.

Post-operative Morbidity and Mortality After Fontan Procedure in Patients with Heterotaxy and Other Situs Anomalies

Heterotaxy is a complex, multisystem disorder associated with single ventricle heart disease and decreased survival. Ciliary dysfunction is common in heterotaxy and other situs abnormalities (H/SA) and may increase post-operative complications. We hypothesized that patients with H/SA have increased respiratory and renal morbidities and increased in-hospital mortality after Fontan procedure. We queried the Pediatric Health Information System database for hospitalizations with ICD-9/10 codes for Fontan procedure in patients aged 1 through 11 years from 2004 to 2019. H/SA was identified by codes for dextrocardia, situs inversus, asplenia/polysplenia, or atrial isomerism and compared to non-H/SA controls. Outcomes were in-hospital mortality or heart transplantation, ECMO, hemodialysis, length of stay (LOS), and mechanical ventilation or vasoactive medication use ≥ 4 days. We adjusted estimates with multivariable logistic regression. Of 7897 patients at 50 centers, 1366 (17%) met criteria for H/SA. H/SA had worse outcomes for all study measures: death/transplantation (1.9 vs 1.1%, OR 1.74 (95% CI 1.01-3.03); p = 0.047), ECMO (3.7 vs 2.3%, OR 1.74 (1.28-2.35); p < 0.001), hemodialysis (2.1 vs 1.2%, OR 1.66 (1.06-2.59); p = 0.026), prolonged mechanical ventilation (13.2% vs 7.6%, OR 1.85 (1.53-2.25); p < 0.001) and vasoactive medication use (29.4 vs 19.7%, OR 1.65 (1.43-1.90), and longer LOS (11 (8-17) vs 9 (7-14) days; p < 0.001). H/SA is associated with increased cardiovascular, renal, and respiratory morbidity, as well as in-hospital mortality after Fontan procedure. Attention to renal and respiratory needs may improve outcomes in this difficult population. The relationship between ciliary dysfunction and lung and renal morbidity should be explored further.

Stepwise Treatment for Heterotaxy Syndrome and Functional Single Ventricle Complicated by Infra-Cardiac Total Anomalous Pulmonary Venous Connection with Ductus Venosus Stent Placement and Subsequent Occlusion

Even today, when the surgical outcome of congenital heart disease in the neonatal period has improved, the prognosis for heterotaxy syndrome and functional single ventricle complicated with total anomalous pulmonary venous connection (TAPVC), especially the infra-cardiac type, is catastrophic. We describe a strategy that combines percutaneous ductus venosus (DV) stent placement and occlusion after TAPVC repair to ensure survival from initial surgery to bidirectional cavopulmonary shunt (BCPS) procedure and facilitate subsequent treatment. Three consecutive patients with heterotaxy syndrome and functional single ventricle complicated by infra-cardiac TAPVC treated with our own strategy were retrospectively studied. In two infants, DV stent placement was performed on the day of birth. In one case at 11 days of age. The risk of pulmonary vein obstruction was reduced, and on-pump surgery, including TAPVC repair, was performed on a standby basis. Since the rapid increase in hepatic enzymes occurred on postoperative day 0 to 1 in all cases, percutaneous stent occlusion was performed until postoperative day 3. The procedure improved liver function. One patient died due to severe atrioventricular valve regurgitation, one case underwent BCPS, and one patient was waiting to undergo. DV stent placement can avoid TAPVC repair in the early neonatal period. After TAPVC repair, the portosystemic shunt remained, resulting in hepatic dysfunction, but this could be improved by stent and vertical vein occlusion. A series of stepwise treatments can be useful to help such critically ill infants survive the high-risk neonatal period and achieve good BCPS circulation.

The surgical anatomy of hearts with isomeric atrial appendages-implications for surgical management

OBJECTIVES

The most severe combinations of cardiac malformations exist in individuals having jumbled-up thoracic and abdominal organs. These patients make up 2 distinct syndromes. As yet, the consensus is lacking on how best to describe the subsets. The subsets are frequently grouped together in terms of 'heterotaxy'. The surgical approaches to the subsets, however, are markedly different. We reviewed our experiences with regard to the anatomy as observed in the autopsy room, by the analysis of computed tomographic studies, and in the operating room, to assess whether the lesions might be segregated on the basis of isomerism of the atrial appendages.

METHODS AND RESULTS

A review of our findings from the examination of specimens from several archives, along with investigation of a large cohort of patients being prepared for surgical treatment, showed that individuals can uniformly be segregated into subgroups on the basis of isomeric arrangement of the atrial appendages. In all instances, this was made possible by using the criterion of the extent of the pectinate muscles within the appendages as judged relative to the atrial vestibules. Segregation on this basis, which correlated excellently with the bronchial arrangement, sets the scene for an appropriate description of the remainder of the heart, providing the cardiac surgeon with all the inferences required for appropriate surgical intervention.

CONCLUSIONS

When assessing individuals having the features of so-called 'heterotaxy', it is possible to segregate the groups into subsets of individuals having either isomeric right or left atrial appendages. This approach provides the framework for the assessment of appropriate surgical management.

Polysplenia syndrome and sickle cell trait: extensive deep venous thrombosis from venous stasis and hypercoagulability

Deep venous thrombosis is a hitherto under-recognized complication occurring in patients with polysplenia syndrome, despite the high prevalence of venous anomalies such as interrupted inferior vena cava (IVC) with azygos/hemiazygos continuation. Here we report the first case of concurrent polysplenia (as evidenced by interrupted IVC with azygos/hemiazygos continuation, multiple left-sided spleens, bowel malrotation with inverted mesenteric veins, preduodenal portal vein, and pancreatic hypoplasia/partial agenesis of the dorsal pancreas) and sickle cell trait, complicated by extensive deep venous thrombosis refractory to medical and interventional radiologic management.

Human Laterality Disorders: Pathogenesis, Clinical Manifestations, Diagnosis, and Management

Human laterality disorders comprise a group of diseases characterized by abnormal location (situs) and orientation of thoraco-abdominal organs and vessels across the left-right axis. Situs inversus totalis is mirror image reversal of thoraco-abdominal organs/great vessels. Situs ambiguus, better known as heterotaxy, is abnormal arrangement of thoraco-abdominal organs across the left-right axis excluding situs inversus totalis. Heterotaxy, also referred to as atrial or atrial appendage isomerism, is characterized by abnormal location of left-sided or right-sided organs with loss of asymmetry of normally paired asymmetric organs. It is associated with a variety of anomalies involving the heart, great vessels, lungs and intra-abdominal organs. Right and left atrial isomerism are associated with multiple complex congenital cardiac and vascular anomalies, many of which are lethal when untreated. Isomerism may also affect the lungs, spleen, liver, gall bladder, and intestines. Innovative surgical therapy of heterotaxy/isomerism has reduced early mortality and markedly improved long-term prognosis.

Whole-exome sequencing reveals a combination of extremely rare single-nucleotide polymorphism of DNAH9 and RSPH1 genes in a Japanese fetus with situs viscerum inversus

Randomization of left-right body asymmetry, situs viscerum inversus (heterotaxy), is commonly associated with primary ciliary dyskinesia (PCD) resulting from an abnormal ciliary structure, with approximately 50% of PCD patients exhibiting organ laterality defects. I herein report an intrauterine fetal death case, in which an autopsy revealed two lobes of the bilateral lungs as well as heterotaxy of abdominal organs (right-sided spleen and inversion of the alimentary and biliary organs). Whole-exome sequencing (WES) identified a heterozygous single-nucleotide change (c.12775T>C) in exon 68 of the DNAH9 gene, which is a rare single-nucleotide polymorphism (SNP) of rs746081639 and results in the amino acid change of p.C4259R. WES also identified a rare SNP of rs763089682 (c.121G>A) in the RSPH1 gene that causes a heterozygous amino acid alteration of p.G41R. The frequencies of both SNPs, C in rs746081639 and A in rs763089682, are 0.00000824, and a polyphen-2 analysis predicted these amino acid changes to be probably damaging, with a score of 1.000. The combination of extremely rare SNPs in DNAH9 and RSPH1 genes might have been the possible mechanism underlying the development of the laterality defect in the present case.

Outcomes of single ventricle palliation in infants with heterotaxy syndrome

 

OBJECTIVES

Heterotaxy is a known risk factor for morbidity and mortality in single ventricle palliation. In this study, we examined our experience with this challenging group of patients.

METHODS

Records of patients born between 2001 and 2019 with heterotaxy, who needed staged single ventricle palliation were retrospectively analysed.

RESULTS

A total of 53 patients were included in this study. Thirty-five (66%) patients had a right ventricular dominance, common atrioventricular septal defect was present in 37 (70%) patients. Anomalous pulmonary venous drainage was present in 29 (55%) patients. Forty-six (86%) patients underwent first-stage palliation. Forty-one (77.3%) patients received a bidirectional cavopulmonary connection. Thirty-one (58%) patients received total cavopulmonary connection (TCPC). Overall survival rate was 92% at 1 month, 74% at 1 year and 68% at 10 years. Twelve (22.6%) patients died before second palliation stage. Four (10%) patients died before TCPC. No patient died after TCPC. Independent risk factors for mortality in the multivariate COX regression were a presence of restrictive pulmonary blood flow (HR 3.23; 95% CI 1.02-10.2; P = 0.05) and greater than mild atrioventricular valve regurgitation (HR 3.57; 95% CI 1.27-10.0; P = 0.02).

CONCLUSIONS

Mortality and morbidity in patients with single ventricle and heterotaxy are high. Restrictive pulmonary blood flow needing early modulation and greater than mild atrioventricular valve regurgitation at presentation are independent risk factors for mortality. Total anomalous pulmonary venous connection was not identified as a risk factor in the current era.

Hydrops fetalis in PKD1L1-related heterotaxy: Report of two foetuses and expanding the phenotypic and molecular spectrum

Abnormalities in the normal left-right axis asymmetry range from situs inversus totalis to situs ambiguous or heterotaxy. More than 80 genes have been described to have a role in the establishment of the normal situs of the internal organs. Pathogenic variants in the PKD1L1 gene have recently been described in heterotaxy and congenital heart disease. Till date, 11 families have been described with PKD1L1-related heterotaxy. We describe the first Indian family with two affected foetuses with PKD1L1-related nonimmune hydrops, congenital heart disease, situs inversus, and heterotaxy, with biallelic variants in the compound heterozygous state.

Twin atrioventricular nodes, arrhythmias, and survival in pediatric and adult patients with heterotaxy syndrome

BACKGROUND

Heterotaxy syndrome is likely to involve arrhythmias from associated conduction system abnormalities, which are distinct in different subtypes of isomerism and may change further after interventions and remodeling.

OBJECTIVE

The purpose of this study was to understand the risk of arrhythmias and its relation to isomerism subtypes.

METHODS

Patients diagnosed between 1980 and 2019 as having heterotaxy syndrome were enrolled and grouped as right atrial isomerism (RAI), left atrial isomerism (LAI), or indeterminate isomerism.

RESULTS

Of the 366 patients enrolled, 326 (89.1%) had RAI, 35 (9.6%) LAI, and 5 (1.4%) indeterminate isomerism; 71 (19.4%) patients were adults. Arrhythmias occurred in 37.2% of patients (109 supraventricular tachycardia [SVT], 8 atrial fibrillation/flutter, 12 ventricular tachycardia, and 14 paced bradycardia). Freedom from arrhythmias by the age of 1, 5, 10, 20, and 40 years was 0.849, 0.680, 0.550, 0.413, and 0.053, respectively. Twin atrioventricular nodes were identified in 51.5% of patients with RAI, 8.7% of patients with LAI, and 40.0% of patients with indeterminate isomerism and were the key predictors of SVT. Indeterminate isomerism was also a risk factor for SVT. Other forms of tachycardia appeared relatively late. Sinus bradycardia with junctional rhythm was common in LAI (48.7%) and less in indeterminate isomerism (20.0%), with none occurring in RAI. Only in patients with RAI who showed the poorest survival, ventricular tachycardia worsened the long-term survival.

CONCLUSION

RAI was the predominant subtype of heterotaxy in this cohort. Collectively, the median RAI/LAI ratio was 0.731 and 5.450 in Western and East Asian studies, respectively. Arrhythmias, tachycardia, or paced bradycardia were common, but the spectrum was distinct among subtypes.

The Spectrum of Cardiac Anomalies Associated with Heterotaxy: A Single-Center Study of a Large Series Based on Computed Tomography

The aim of the study was to identify and correlate the anatomical variants of cardiac structures among patients with heterotaxy. In this retrospective cross-sectional analysis of 13 years duration, 302 patients of congenital heart diseases associated with heterotaxy were studied. All these patients had undergone a meticulous clinical evaluation, echocardiography, and cardiac computed tomography. The mean age of the cohort was 38.4 months, with 180 males and 122 females. The cohort had 184 patients of right isomerism and 118 of left isomerism. More than half of the cohort had abnormal pulmonary veins. Over 75% of the cohort had low pulmonary blood flow. Abnormal relationship of great arteries was seen in nearly 69% of the cohort. Atrio-venticular canal defect was the commonest anatomical variant. Overall, 43% of the cohort had single ventricle physiology, predominantly associated with right isomerism. Heterotaxy forms a difficult anatomical subset to comprehend due to the plethora of possible abnormalities. However, unless the cardiac and visceral anatomy is delineated well, the surgical plan becomes suboptimal and often elusive, leaving tough choices for cardiac surgeon. It is essential to obtain all the possible anatomical information using additional imaging modalities to devise a basis for a comprehensive plan for medical and surgical management. A better understanding of the genetic and molecular factors in the etiology, coupled with the application of state-of-the-art imaging techniques, is likely to add to our knowledge of heterotaxy to bring about improved surgical outcomes and a better quality of life for patients suffering from this complex entity.

Unusual long survival in a case of heterotaxy and polysplenia

Heterotaxy syndrome with polysplenia is an extremely rare congenital disorder caused by a disruption in the embryonic development that results in an abnormal arrangement of the abdominal and thoracic organs. We present the case of a 59-year-old female patient with invasive ductal carcinoma of the right breast (luminal A type) and CT findings of heterotaxy syndrome with polysplenia. The most remarkable anomalies identified were a left inferior vena cava draining into the hemiazygos vein, absent inferior vena cava at the thoracic level, and hepatic veins directly draining into the right atrium. Moreover, an atrial septal defect was identified, explaining the pulmonary hypertension of unknown cause previously detected in the patient. The relevance of this case lies in the unusual anatomical abnormalities found and the large patient survival, having in to account the great rate of heterotaxy syndrome mortality in the first years of life.

Biventricular Conversion in Unseptatable Hearts: "Ventricular Switch"

Patients with complex systemic and pulmonary venous anatomy, common atrioventricular canal defects and conotruncal anomalies have traditionally been routed to univentricular palliation and labeled as "unseptatable." This report describes our initial experience in septation/biventricular conversion ("ventricular switch"), utilizing the left ventricle (LV) as the subpulmonary ventricle, essentially recapitulating the physiology of congenitally corrected transposition of the great arteries. Five consecutive patients with challenging anatomic configuration underwent septation. All patients were severely cyanotic and had important functional limitations. All patients required complex atrial septation. Ventricular septation was precluded by fixed pulmonary vascular resistance in 2 patients. Systemic venous return was diverted to the morphologic LV as part of physiological 2V (n = 4) or 1.5 V repair (n = 1). Median conversion age was 9 years (range 11 months-46 years). Four patients had 12 previous cardiac surgical procedures in preparation for univentricular repair elsewhere. Three dimensional-printed heart models evaluated feasibility of septation. All patients are alive at a median follow-up of 0.6 years (range 0.08-2.7 years). Median hospital stay was 13 (range 10-60) days. LV recruitment improved functional status and significantly increased systemic oxygen saturation in all patients (79 ± 7% vs 95 ± 5%, P = 0.003). We report a novel paradigm for successfully utilizing both ventricles with the morphologic LV as the subpulmonary ventricle, in a complex population thought to be unseptatable. This approach is versatile and can likely be extrapolated to other complex anatomic configurations. Although we utilized this strategy in patients of variable age, earlier ventricular switch may yield the best results.

Double Choker: Double Aortic Arch with Bilateral Aortic Coarctation Associated with Heterotaxy-Asplenia Syndrome and Complex Atrioventricular Canal Defect

• Double aortic arch (DAA) typically occurs in isolation. • DAA with bilateral coarctation (COA) is very rare with three prior documented cases. • In addition to DAA with bilateral COA our case also has complex intracardiac disease. • Echocardiography served as the primary diagnostic tool with advanced imaging as a useful adjunct.

Situs Ambiguous Anomaly during Laparoscopic Cholecystectomy in an Adult Female

Situs anomalies are rare structural defects affecting 0.01% of general population. They present with multisystem structural defects mostly involving cardiovascular, respiratory and GI systems. Situs abnormality with presence of multiple spleen is termed as left atrial isomerism with anatomical and structural differences to its countertype situs ambiguous with asplenia (right atrial isomerism). In this case report, we present an adult case of situs ambiguous anomaly which was diagnosed incidentally during laparoscopic cholecystectomy. The patient had enlarged left lobe of liver, multiple splenules on right side, malrotated small and large gut, interrupted inferior vena cava with azygos continuation, and bilateral bilobed lungs. It is concluded that variations in situs ambiguous cases differ and a single description is not possible. It is crucial to reveal these variations by using imaging modalities and being aware of them prior to surgery and invasive intervention to prevents the possible risks and complications.

Neonatal Assessment of Infants with Heterotaxy

Heterotaxy is a generalized term for patients who have an abnormality of laterality that cannot be described as situs inversus. Infants with heterotaxy can have significant anatomic and medical complexity and require personalized, specialized care, including comprehensive anatomic assessment. Common and rare anatomic findings are reviewed by system to help guide a thorough phenotypic evaluation. General care guidelines and considerations unique to this patient population are included. Future directions for this unique patient population, particularly in light of improved neonatal survival, are discussed.

Isomerism of the atrial appendages: morphology and terminology

BACKGROUND

Our aim is to identify the pathognomonic anatomical markers and the best terminology to describe the cardiac malformations associated with absent or multiple spleens, which are known as asplenia or polysplenia syndromes or isomerism.

MATERIALS AND METHODS

We have reviewed 65 hearts with isomerism of atrial appendages of the Anatomical Collections of Congenital Heart Disease, Institute of Pathological Anatomy of the University of Padua consisting of 1800 specimens. All the hearts were classified according to sequential segmental classification.

RESULTS

The incidence of isomerism was 3.6%. Of the total, 45 hearts with isomerism of right atrial appendages showed bilateral trilobed lungs, short bronchi, and absent spleen. The atrioventricular junction was univentricular in 49% of cases with a common atrioventricular valve in 91%. Pulmonary atresia and double outlet right ventricle were present in 40% and 47% of cases, respectively. Total anomalous pulmonary venous drainage and absent coronary sinus were always present. In 20 hearts with isomerism of left atrial appendages, bilateral bilobed lungs with long bilateral bronchi and multiple spleens were always found. The biventricular atrioventricular connection was present in 65% with a common valve in 30% of the hearts. The ventriculoarterial connection was concordant in 45% of cases, and aortic atresia and pulmonary atresia were both noted in 15% of each. An anomalous symmetric pulmonary venous drainage was observed in 65% of the hearts and interruption of inferior vena cava was found in 75% of cases.

CONCLUSIONS

We believe that the appropriate terminology is based on the symmetrical morphology of the atrial appendages. The absence of the coronary sinus and the total anomalous pulmonary venous drainage are the markers of isomerism of the right atrial appendages. Symmetric pulmonary venous drainage and interruption of inferior vena cava are the markers of isomerism of left atrial appendages. In recent years, thanks to the improvement of clinical diagnosis and of surgical techniques these patients have the possibility to survive to adult age.

Trends in Infant Mortality After TAPVR Repair over 18 Years in Texas and Impact of Hospital Surgical Volume

For some congenital heart lesions, higher institutional surgical volume has been associated with better survival than in lower volume centers. The relationship between institutional surgical volume and mortality in infants after total anomalous pulmonary vein return (TAPVR) repair has not been well explored. The Texas Inpatient Public Use Data File was queried for hospitalizations including TAPVR repair in infants between January 1, 1999 and December 31, 2016. We first evaluated the change in mortality over the study period. We then evaluated associations between institutional TAPVR surgical volume and mortality using univariable analysis and multivariable analysis accounting for center effects. For secondary analyses, we evaluated the association between volume and mortality among non-mutually exclusive TAPVR subsets, including isolated TAPVR, TAPVR with other congenital heart disease (CHD), TAPVR with heterotaxy, and TAPVR with single ventricle anatomy. Of 971 surgical hospitalizations that met inclusion criteria, 62% were male. Mortality after TAPVR repair decreased over the study period from 15.1% (1999-2004) to 7.6% (2012-2016) with an odds ratio per increasing year of 0.96 (95% CI 0.92-0.99, p = 0.030). By univariable analysis, earlier era, preterm birth, lower institutional surgical volume, heterotaxy, and additional CHD were associated with increased mortality. Institutional surgical volume remained significant in multivariate analysis with an odds ratio per increase in surgical volume of every 10 patients of 0.93 (95% CI 0.90-0.96, p < 0.001). When examining by subgroup, isolated TAPVR had the lowest mortality (n = 606, mortality = 6%), compared to TAPVR with other CHD (n = 359, mortality = 20%), TAPVR with heterotaxy (n = 135, mortality = 21%), and TAPVR with single ventricle (n = 128, mortality = 23%). In all groups except those with single ventricle, higher surgical volume was associated with lower mortality in multivariate analyses (isolated TAPVR p = 0.001, TAPVR with other CHD p = 0.009, TAPVR with heterotaxy p < 0.001, TAPVR with single ventricle p = 0.161). This is the first study to demonstrate an association between institutional surgical volume and mortality after TAPVR repair. Higher volume centers are associated with lower hospital mortality after TAPVR repair, including TAPVR with other CHD.

Left-right asymmetric heart jogging increases the robustness of dextral heart looping in zebrafish

Building a left-right (L-R) asymmetric organ requires asymmetric information. This comes from various sources, including asymmetries in embryo-scale genetic cascades (including the left-sided Nodal cascade), organ-intrinsic mechanical forces, and cell-level chirality, but the relative influence of these sources and how they collaborate to drive asymmetric morphogenesis is not understood. During zebrafish heart development, the linear heart tube extends to the left of the midline in a process known as jogging. The jogged heart then undergoes dextral (i.e. rightward) looping to correctly position the heart chambers relative to one another. Left lateralized jogging is governed by the left-sided expression of Nodal in mesoderm tissue, while looping laterality is mainly controlled by heart-intrinsic cell-level asymmetries in the actomyosin cytoskeleton. The purpose of lateralized jogging is not known. Moreover, after jogging, the heart tube returns to an almost midline position and so it is not clear whether or how jogging may impact the dextral loop. Here, we characterize a novel loss-of-function mutant in the zebrafish Nodal homolog southpaw (spaw) that appears to be a true null. We then assess the relationship between jogging and looping laterality in embryos lacking asymmetric Spaw signals. We found that the probability of a dextral loop occurring, does not depend on asymmetric Spaw signals per se, but does depend on the laterality of jogging. Thus, we conclude that the role of leftward jogging is to spatially position the heart tube in a manner that promotes robust dextral looping. When jogging laterality is abnormal, the robustness of dextral looping decreases. This establishes a cooperation between embryo-scale Nodal-dependent L-R asymmetries and organ-intrinsic cellular chirality in the control of asymmetric heart morphogenesis and shows that the transient laterality of the early heart tube has consequences for later heart morphogenetic events.

Intra-Abdominal Abnormalities Associated with Polysplenia Syndrome

What to look for in case of polysplenia and/or unusual disposition of several intra-abdominal organs.

Alkylglycerol monooxygenase, a heterotaxy candidate gene, regulates left-right patterning via Wnt signaling

Congenital heart disease (CHD) is a major cause of morbidity in the pediatric population yet its genetic and molecular causes remain poorly defined. Previously, we identified AGMO as a candidate heterotaxy disease gene, a disorder of left-right (LR) patterning that can have a profound effect on cardiac function. AGMO is the only known alkylglycerol monooxygenase, an orphan tetrahydrobiopterin dependent enzyme that cleaves the ether linkage in alkylglycerols. However, whether AGMO plays a role in LR patterning was unexplored. Here we reveal that Agmo is required for correct development of the embryonic LR axis in Xenopus embryos recapitulating the patient's heterotaxy phenotype. Mechanistically, we demonstrate that Agmo is a regulator of canonical Wnt signaling, required during gastrulation for normal formation of the left - right organizer. Mutational analysis demonstrates that this function is dependent on Agmo's alkylglycerol monooxygenase activity. Together, our findings identify Agmo as a regulator of canonical Wnt signaling, demonstrate a role for Agmo in embryonic axis formation, and provide insight into the poorly understood developmental requirements for ether lipid cleavage.

Characterisation of computed tomography angiography findings in paediatric patients with heterotaxy

BACKGROUND

Heterotaxy refers to the abnormal arrangement of organs across the left-right axis and is typically associated with complex cardiovascular malformations.

OBJECTIVE

To characterise the range of cardiac and extracardiac CT angiography findings in children with heterotaxy using the latest nomenclature consensus and to compare the different types of isomerism.

MATERIALS AND METHODS

We retrospectively analysed the data of 64 consecutive paediatric patients referred to our tertiary paediatric cardiovascular centre who underwent CT angiography for the evaluation of known or suspected heterotaxy within a 52-month period.

RESULTS

Right atrial isomerism was identified in 44 (69%) children, while left atrial isomerism was identified in 18 (28%) children. Atrial appendage anatomy and situs could not be determined in 2 children (3%). Associated heart defects included complete atrioventricular canal (CAVC) in 51 (80%) children, total anomalous pulmonary venous return in 43 (67%) and pulmonary atresia in 23 (36%). The bronchial branching pattern corresponded to atrial appendage morphology in all children except in the two in whom atrial appendage morphology could not be defined. In children with right atrial isomerism, the most common associated abnormalities were CAVC (n=41, 93%) and asplenia (n=34, 77%), while in those with left atrial isomerism, the most common associated abnormalities were polysplenia (n=17, 94%) and an interrupted inferior vena cava with azygos continuation (n=15, 83%).

CONCLUSION

CT angiography provides useful cardiovascular and extracardiac data on heterotaxy, which frequently involves a pattern of side-related findings but has great anatomical variability.

Standardised imaging pipeline for phenotyping mouse laterality defects and associated heart malformations, at multiple scales and multiple stages

Laterality defects are developmental disorders resulting from aberrant left/right patterning. In the most severe cases, such as in heterotaxy, they are associated with complex malformations of the heart. Advances in understanding the underlying physiopathological mechanisms have been hindered by the lack of a standardised and exhaustive procedure in mouse models for phenotyping left/right asymmetries of all visceral organs. Here, we have developed a multimodality imaging pipeline, which combines non-invasive micro-ultrasound imaging, micro-computed tomography (micro-CT) and high-resolution episcopic microscopy (HREM) to acquire 3D images at multiple stages of development and at multiple scales. On the basis of the position in the uterine horns, we track in a single individual, the progression of organ asymmetry, the situs of all visceral organs in the thoracic or abdominal environment, and the fine anatomical left/right asymmetries of cardiac segments. We provide reference anatomical images and organ reconstructions in the mouse, and discuss differences with humans. This standardised pipeline, which we validated in a mouse model of heterotaxy, offers a fast and easy-to-implement framework. The extensive 3D phenotyping of organ asymmetry in the mouse uses the clinical nomenclature for direct comparison with patient phenotypes. It is compatible with automated and quantitative image analyses, which is essential to compare mutant phenotypes with incomplete penetrance and to gain mechanistic insight into laterality defects.

Summary: Laterality defects, which combine anomalies in several visceral organs, are challenging to phenotype. We have developed here a standardised approach for multimodality 3D imaging in mice, generating quantifiable phenotypes.

Concurrent right atrial isomerism, complete atrioventricular septal defect, and single ventricle in an L-transposition of great arteries patient complicated by brain abscess

We present a case of an 11-year-old Indonesian female who was referred to our facility after surgical excision of brain abscess. The patient has been previously diagnosed with right atrial isomerism, complete atrioventricular septal defect, and L-Transposition of great arteries. Multiple staged surgeries are required for the management of this condition.

Polysplenia syndrome with situs ambiguous, common mesentery, and IVC interruption discovered incidentally in an adult

Polysplenia syndrome associates multiple spleens to other malformations, most frequently cardiac, vascular, visceral, and biliary malformations. Polysplenia has been described mainly in childhood owing to critical anatomic malformations related to cardiac defects or biliary atresia. We present a case of polysplenia syndrome found in a 58-year-old man. Only those with mild anatomical abnormalities reach adulthood without a diagnosis. Radiological examinations are helpful to the diagnosis by ascertaining the location and number of spleens, location of other organs in the chest and abdomen, and identification of other associated anomalies.

Cardiac Rhythm Disturbances in Heterotaxy Syndrome

OBJECTIVE

Heterotaxy syndrome is associated with complex cardiac malformations and cardiac conduction system abnormalities. Those with right atrial isomerism (RAI) have dual sinus nodes and dual atrioventricular nodes predisposing them to supraventricular tachycardia (SVT). Those with left atrial isomerism (LAI) lack a normal sinus node and are at risk of sinus node dysfunction (SND) and atrioventricular block (AV block). We report the occurrence and risk factors associated with arrhythmias in heterotaxy syndrome.

METHODS

A retrospective review of all heterotaxy syndrome patients born and treated at our institution between 2000 and 2014 was performed.

RESULTS

A total of 40 patients were identified; 16/40 (40%) with LAI and 24/40 (60%) with RAI. There were 12 deaths during follow-up [LAI 3/16 (19%), RAI 9/24 (38%); p = 0.30]. Twenty-one patients had arrhythmias during a mean follow-up period of 5.4 years; 14/16 (87%) in LAI and 7/24 (29%) in RAI (p < 0.001). Freedom from arrhythmia at 1,3,5 years of age was 75.0%, 37.9%, 22.7% in LAI, and 83.3%, 77.5%, 69.6% in RAI, respectively(p = 0.00261). LAI had a three-fold increase in developing arrhythmias. Left atrial isomerism was the only factor identified to be associated with arrhythmia occurrence.

CONCLUSIONS

Arrhythmias were commonly seen in heterotaxy syndrome particularly in left isomerism with more than half of the patients having arrhythmias by 3 years of age. Atrial situs was the only risk factor identified to be associated with arrhythmias, and close follow-up is warranted in these patients.

Compound heterozygous Pkd1l1 variants in a family with two fetuses affected by heterotaxy and complex Chd

Heterotaxy and congenital heart defects associated with pathogenic variants in the PKD1L1 gene (autosomal visceral heterotaxy type 8, MIM 617205) has been reported in only four individuals from three unrelated families. We describe a further family with two affected fetuses and novel compound heterozygous pathogenic variants in PKD1L1. PKD1L1 has been shown to function in the ciliary sensation of nodal flow at the embryo primitive node and in the restriction of NODAL signalling to the left lateral. plate mesoderm, mechanisms involved in the development of laterality in vertebrates. Individuals affected with this autosomal recessive condition have variable thoracic and abdominal situs. Features of CHD and other anomalies vary between and within families.

Polysplenia Syndrome as a Risk Factor for Early Progression of Pulmonary Hypertension

BACKGROUND

Recent progress in surgical and intensive care has improved the prognosis of congenital heart disease (CHD) associated with heterotaxy syndrome. Less is known, however, about pulmonary vascular complications in these patients. Methods and Results: We reviewed medical records of 236 patients who were diagnosed with polysplenia syndrome at 2 institutions for pediatric cardiology in Japan from 1978 to 2015. We selected and compared the clinical records of 16 patients with polysplenia who had incomplete atrioventricular septal defect (AVSD) as the polysplenia group, and 22 age-matched patients with incomplete AVSD without any syndromes including polysplenia as the control group. Although the severity of systemic to pulmonary shunt was not significantly different between the groups, mean pulmonary artery pressure (mPAP) and pulmonary vascular resistance index (PVRI) were significantly higher in the polysplenia group than the control (mPAP, 37.3 vs. 19.1 mmHg, P=0.001; PVRI, 5.7 vs. 1.4 WU∙m², P=0.014) before surgical intervention. On regression analysis, polysplenia influenced the development of pulmonary hypertension (PH) regardless of age at evaluation or degree of systemic to pulmonary shunt in the patients with incomplete AVSD.

CONCLUSIONS

Polysplenia syndrome is an independent risk factor for CHD-associated PH. Earlier intervention may be required to adjust the pulmonary blood flow in polysplenia syndrome with CHD to avoid the progression of PH.

Antenatal ultrasound diagnosis of small bowel non-rotation in complex left isomerism: a case report

•

A rare case of mixed isomerism and antenatally diagnosed non-rotation of bowel is reported.

•

Features of bowel non-rotation should be sought antenatally in cases of isomerism.

•

Mixed isomerism and postnatal sequelae should be considered when right and left sided pathology coexist.z

Presentation of case

A multiparous expectant mother was referred to our tertiary unit at 23 weeks with a complex fetal cardiac anomaly in the context of suspected heterotaxy syndrome. The cardiac findings were consistent with isomerism: the fetal cardiac position was levocardia with a single functioning double outlet ventricle and AV valve, pulmonary stenosis, and interrupted inferior vena cava (IVC) with azygous continuation. The fetal abdominal situs was also altered, with the stomach to the right, and the hepatobiliary system midline to left. The spleen was not identified antenatally or postnatally. At 36 weeks, ultrasound revealed an abnormal bowel pattern with small bowel loops on the right side of the abdomen and large bowel on the left, suggesting a diagnosis of non- rotation. The infant was delivered vaginally at 39 weeks. The cardiac diagnosis and non-rotation of the small bowel were confirmed by postnatal echocardiography and contrast fluoroscopy.

Discussion

Heterotaxy syndrome is traditionally classified into right or left isomerism depending on how and where the organs are anatomically arranged. The case presented here demonstrates mixed laterality and prenatal ultrasound features of non-rotation.

Conclusion

It is important to be informed of the embryological variants of isomerism and actively seek antenatal evidence of bowel non-rotation in such cases.

Biliary atresia with an unusual abdominal orientation: A case report

INTRODUCTION

Biliary atresia (BA) is a rare condition where the hepatic or common bile ducts get obliterated by fibrous tissue for unknown causes. It is diagnosed in 5-10 per 100,000 live births worldwide in whom liver injury and death are definite if untreated.

PRESENTATION

We report a case of BA with associated malrotation and situs ambiguous discovered incidentally during Kasai procedure. The small intestine was found to be malrotated with the duodenojejunal junction to the right of the vertebral column. The liver, stomach, and spleen were in the center, right side, and left side of the abdomen respectively. The malrotation was corrected by performing a Ladd's procedure in addition to the Kasai. She had an uneventful postoperative course. At follow-up on the second, sixth and 12th weeks postoperatively, she had normal stool color and liver function.

DISCUSSION

BA patients with associated structural anomalies might have a worse outcome after the Kasai procedure. Several studies demonstrated that the coexistence of malrotation with BA to be in the range of 0.3%-9.4% among BA patients. Also, the presence of situs abnormalities with BA has been reported in some studies to be present in 0.01-0.045% of BA cases. However, the presentation of BA with both situs inversus and intestinal malrotation has seldom been reported.

CONCLUSION

The diagnosis of BA should prompt further investigation for other anatomical abnormalities as the presence of which might affect the management plan.

WDR5 regulates left-right patterning via chromatin-dependent and -independent functions

Congenital heart disease (CHD) is a major cause of infant mortality and morbidity, yet the genetic causes and mechanisms remain opaque. In a patient with CHD and heterotaxy, a disorder of left-right (LR) patterning, a de novo mutation was identified in the chromatin modifier gene WDR5 WDR5 acts as a scaffolding protein in the H3K4 methyltransferase complex, but a role in LR patterning is unknown. Here, we show that Wdr5 depletion leads to LR patterning defects in Xenopus via its role in ciliogenesis. Unexpectedly, we find a dual role for WDR5 in LR patterning. First, WDR5 is expressed in the nuclei of monociliated cells of the LR organizer (LRO) and regulates foxj1 expression. LR defects in wdr5 morphants can be partially rescued with the addition of foxj1 Second, WDR5 localizes to the bases of cilia. Using a mutant form of WDR5, we demonstrate that WDR5 also has an H3K4-independent role in LR patterning. Guided by the patient phenotype, we identify multiple roles for WDR5 in LR patterning, providing plausible mechanisms for its role in ciliopathies like heterotaxy and CHD.

Left-right asymmetry in heart development and disease: forming the right loop

Extensive studies have shown how bilateral symmetry of the vertebrate embryo is broken during early development, resulting in a molecular left-right bias in the mesoderm. However, how this early asymmetry drives the asymmetric morphogenesis of visceral organs remains poorly understood. The heart provides a striking model of left-right asymmetric morphogenesis, undergoing rightward looping to shape an initially linear heart tube and align cardiac chambers. Importantly, abnormal left-right patterning is associated with severe congenital heart defects, as exemplified in heterotaxy syndrome. Here, we compare the mechanisms underlying the rightward looping of the heart tube in fish, chick and mouse embryos. We propose that heart looping is not only a question of direction, but also one of fine-tuning shape. This is discussed in the context of evolutionary and clinical perspectives.

Accuracy of echocardiography in diagnosing total anomalous pulmonary venous return

Objective:

Total anomalous pulmonary venous return is an uncommon cyanotic congenital heart defect. Echocardiography is the initial diagnostic tool. Complimentary non-invasive modalities like cardiac computerized tomographic angiography and cardiac magnetic resonance imaging have replaced the need for cardiac catheterization in difficult cases. This study aimed to determine the accuracy of echocardiography in diagnosing total anomalous pulmonary venous return, and to determine the factors that may decrease its sensitivity.

Methods:

This was a cross-sectional study conducted at the Aga Khan University Hospital Karachi, Pakistan from January 2010 to August 2016. All patients who were diagnosed with Total anomalous pulmonary venous return on echocardiography and had subsequent confirmation either on cardiac CT angiography or surgery were included. The diagnostic accuracy of echocardiography was expressed as sensitivity. Previously described taxonomy was used to define diagnostic error. Univariate and multivariate analysis were done by logistic regression OR (95% CI) were reported to identify factors causing the diagnostic error.

Results:

High diagnostic sensitivity (81%) was found in isolated total anomalous pulmonary venous return and low (27%) in heterotaxy and mixed (20%) varieties. Poor acoustic windows and right isomerism were found to be significant factors responsible for the diagnostic error on multivariate analysis.

Conclusion:

Echocardiography can diagnose isolated total anomalous pulmonary venous return with high accuracy. Use of additional modalities may be required for a complete diagnosis in cases with mixed variety, heterotaxy and poor acoustic windows.

Simultaneous Systemic to Pulmonary Shunt and Pulmonary Artery Banding is a Viable Option for Neonatal Palliation of Single Ventricle Physiology

A subset of neonates with single ventricle (SV) physiology has antegrade pulmonary blood flow that is deemed unlikely to be reliable until Glenn. We have used systemic to pulmonary shunt (SPS) with pulmonary artery banding (PAB) to optimize pulmonary blood flow while maintaining reserve antegrade flow. We hypothesize that this is an effective strategy that can be accomplished without the routine need for cardiopulmonary bypass. We retrospectively reviewed the records of 60 neonates who underwent combined SPS + PAB between 2004 and 2015. Data are presented as median with quartiles. Children were 8 (4-19) days old at surgery and included 38 (63%) boys. Atresia or severe stenosis of the subpulmonary atrioventricular (AV) valve associated with pulmonary blood flow across a bulboventricular foramen was present in 37 (62%). In 20 (33%), heterotaxy-associated unbalanced AV canal with pulmonary stenosis with or without anomalous pulmonary venous drainage was present. First-stage palliation was accomplished without cardiopulmonary bypass in 44 patients (73%). There were 7 (12%) hospital deaths, 4 among the 20 (20%) with heterotaxy. Fifty-three children were followed for a median 5.1 (1.8-8.2) years. Three early reinterventions were required after initial palliation (1 PAB adjustment, 2 SPS balloon angioplasties). Five additional heterotaxy patients experienced late mortality during follow-up. There were no early or emergent Glenn. Thirty-nine patients have reached Fontan circulation with a median pre-Fontan PA pressure of 14 (12-18) mm Hg. One patient converted to biventricular physiology and the remaining await completion Fontan. Heterotaxy was the only independent predictor of mortality (hazard ratio 10 (2.3-44, P < 0.001). In SV patients with unreliable antegrade PA flow, SPS + PAB is an effective first-stage palliation. SV patients with heterotaxy are at increased risk for mortality.

Transposition of the great arteries: A laterality defect in the group of heterotaxy syndromes or an outflow tract malformation?

BACKGROUND/AIM

Transposition of the great arteries (TGA) is traditionally classified as a "conotruncal heart defect", implying that TGA evolves from abnormal development of the outflow tract (OFT) of the embryonic heart. However, recently published genetic data suggest that TGA may be linked to laterality gene defects rather than OFT gene defects. The aim of our study was to clarify whether there is any statistically significant link between TGA and clinically diagnosed laterality defects (heterotaxy).

METHODS

Retrospective cross-sectional analysis of 533 patients diagnosed with TGA at our cardiac center over a period of 13 years (2002-2015). Hospital informatics and digital data recording systems were used for collecting patients' data and all patients were reviewed to check the echocardiograms for verification of the diagnosis, type (TGA, congenitally corrected TGA (ccTGA), and levo-position of the great arteries (LGA)), complexity of TGA, and all other variables (e.g., abdominal organ arrangement, cardiac position, presence or absence of other cardiac defects).

RESULTS

Of 533 TGA patients, 495 (92.9%) had the usual arrangement of the internal organs, 21 (3.9%) had mirror-imagery, 7 (1.3%) had left and 10 (1.8%) had right isomerism. 444 (83.3%) patients had TGA. The number of patients who had usual visceral arrangement in each TGA type was: 418 (94.1%) in TGA, 49 (92.4%) in ccTGA, and 28 (77.7%) in LGA. 6 (1.4%) TGA patients, 4 (11.1%) patients with LGA were found to have right isomerism, while no ccTGA patient presented with this asymmetry. 4 (0.9%) TGA patients, 1 (1.9%) ccTGA patient and 2 (5.6%) patients with LGA had left isomerism. Heterotaxy (mirror-imagery, left and right isomerism) was more associated with LGA than TGA or ccTGA with a statistically significant difference (P value of 0.001).

CONCLUSION

In contrast to recently published genetic data, our morphological data do not disclose a significant link between TGA and heterotaxy.

Is isomerism a risk factor for intestinal volvulus?

INTRODUCTION

Isomerism, or heterotaxy syndrome, affects many organ systems anatomically and functionally. Intestinal malrotation is common in patients with isomerism. Despite a low reported risk of volvulus, some physicians perform routine screening and prophylactic Ladd procedures on asymptomatic patients with isomerism who are found to have intestinal malrotation. The primary aim of this study was to determine if isomerism is an independent risk factor for volvulus.

METHODS

Kid's Inpatient Database data from 1997 to 2012 was utilized for this study. Characteristics of admissions with and without isomerism were compared with a particular focus on intestinal malrotation, volvulus, and Ladd procedure. A logistic regression was conducted to determine independent risk factors for volvulus with respect to isomerism.

RESULTS

15,962,403 inpatient admissions were included in the analysis, of which 7970 (0.05%) patients had isomerism, and 6 patients (0.1%) developed volvulus. Isomerism was associated with a 52-fold increase in the odds of intestinal malrotation by univariate analysis. Of 251 with isomerism and intestinal malrotation, only 2.4% experienced volvulus. Logistic regression demonstrated that isomerism was not an independent risk factor for volvulus.

CONCLUSION

Isomerism is associated with an increased risk of intestinal malrotation but is not an independent risk factor for volvulus.

TYPE OF STUDY

Prognosis study.

LEVEL OF EVIDENCE

Level III.

Rare copy number variants analysis identifies novel candidate genes in heterotaxy syndrome patients with congenital heart defects

BACKGROUND

Heterotaxy (Htx) syndrome comprises a class of congenital disorders resulting from malformations in left-right body patterning. Approximately 90% of patients with heterotaxy have serious congenital heart diseases; as a result, the survival rate and outcomes of Htx patients are not satisfactory. However, the underlying etiology and mechanisms in the majority of Htx cases remain unknown. The aim of this study was to investigate the function of rare copy number variants (CNVs) in the pathogenesis of Htx.

METHODS

We collected 63 sporadic Htx patients with congenital heart defects and identified rare CNVs using an Affymetrix CytoScan HD microarray and real-time polymerase chain reaction. Potential candidate genes associated with the rare CNVs were selected by referring to previous literature related to left-right development. The expression patterns and function of candidate genes were further analyzed by whole mount in situ hybridization, morpholino knockdown, clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9)-mediated mutation, and over-expressing methods with zebrafish models.

RESULTS

Nineteen rare CNVs were identified for the first time in patients with Htx. These CNVs include 5 heterozygous genic deletions, 4 internal genic duplications, and 10 complete duplications of at least one gene. Further analyses of the 19 rare CNVs identified six novel potential candidate genes (NUMB, PACRG, TCTN2, DANH10, RNF115, and TTC40) linked to left-right patterning. These candidate genes exhibited early expression patterns in zebrafish embryos. Functional testing revealed that downregulation and over-expression of five candidate genes (numb, pacrg, tctn2, dnah10, and rnf115) in zebrafish resulted in disruption of cardiac looping and abnormal expression of lefty2 or pitx2, molecular markers of left-right patterning.

CONCLUSIONS

Our findings show that Htx with congenital heart defects in some sporadic patients may be attributed to rare CNVs. Furthermore, DNAH10 and RNF115 are Htx candidate genes involved in left-right patterning which have not previously been reported in either humans or animals. Our results also advance understanding of the genetic components of Htx.

Comparing levocardia and dextrocardia in fetuses with heterotaxy syndrome: prenatal features, clinical significance and outcomes

Background

To investigate the differences in cardiovascular disease, extracardiac anomalies and outcomes between fetuses with levocardia and dextrocardia.

Methods

Clinical demographics, prenatal features, postnatal characteristics and the outcomes of fetuses with levocardia or dextrocardia were recorded and analyzed.

Results

Sixty-five fetuses with dextrocardia and thirty-eight fetuses with levocardia were enrolled. Right ventricle outlet obstruction, atrioventricular septal defect and intestinal malrotation were common in both groups. Univentricular physiology, transposition of the great arteries and esophageal atresia were more frequent in fetuses with levocardia, whereas abnormal pulmonary venous connection, double outlet of right ventricle, left ventricle outlet obstruction and brain abnormalities were more frequent in the dextrocardia group. The accuracy of evaluating cardiac malformations was high, but the sensitivity in assessing extracardiac abnormalities was low.

Conclusions

Although the disorders have certain overlapping features, there are several differences between fetuses with levocardia and dextrocardia. These findings might improve patient counseling and perinatal management.

Segregating bodily isomerism or heterotaxy: potential echocardiographic correlations of morphological findings

BACKGROUND

Bodily isomerism, also referred to as heterotaxy, involves predominantly the thoracic organs, although other organs are usually abnormally positioned. Previously assessed on the basis of splenic anatomy, it is now understood that isomerism is better segregated on the basis of atrial appendage morphology. This allows for anticipation of associated findings. We aimed to assess the accuracy of segregation based on the morphology of the atrial appendages and other structures more easily identified by echocardiography.

METHODS

We reviewed postmortem specimens of hearts from the archives at four institutions categorised as obtained from patients with "heterotaxy". The cardiac structures were analysed using sequential segmental analysis. Non-cardiac structures were also examined if available. Statistical analyses were performed to compare differences in the settings of right as opposed to left isomerism.

RESULTS

Specimens were available from 188 patients. Of these, 57 had left isomerism, and 131 had right isomerism. Atrial appendages were isomeric in all patients. A coronary sinus was found only in left isomerism, whereas a terminal crest, or a Eustachian valve, was found only in right isomerism. Interruption of the inferior caval vein was associated with left isomerism, whereas totally anomalous pulmonary venous connection was associated with right isomerism.

CONCLUSION

Isomerism is uniformly segregated on the basis of the morphology of the atrial appendages, itself defined by the extent of the pectinate muscles. Other features such as the presence of a coronary sinus and systemic venous return can further help with such segregation of isomerism.

Polysplenia syndrome with duodenal and pancreatic dysplasia in a Holstein calf: a case report

Background

Laterality disorders of the abdominal organs include situs inversus totalis that mirrors the arrangements of all internal organs and heterotaxy syndrome (situs ambiguus) in which the thoracic or abdominal organs are abnormally arranged. Heterotaxy is often accompanied by multiple congenital malformations, and it generally comprises asplenia and polysplenia syndromes. To our knowledge, polysplenia syndrome has been reported in only three cattle, and computerized tomographic (CT) images of these animals were not obtained.

Case presentation

A six-month-old Holstein heifer had ruminal tympani and right abdominal distension. CT imaging showed that the rumen occupied the right side of the abdominal cavity, the omasum and abomasum occupied the left ventral side and the liver was positioned on the left. The colon and cecum were located at the left dorsum of the cavity, and the left kidney was located more cranially than the right. Postmortem findings revealed two spleens attached to the rumen. Significantly, the duodenum was too short to be divided into segments, except the cranial and descending parts, or flexures, except the cranial flexure, and the pancreas, which lacked a left lobe, was covered with mesojejunum. The liver comprised a relatively large right lobe and a small left lobe without quadrate and caudate lobes. The caudal vena cava that connected to the left azygous vein passed irregularly through the aortic hiatus of the diaphragm, and the common hepatic vein without the caudal vena cava passed through the caval foramen. Although the lungs and heart were morphologically normal, the right atrium received three major systemic veins. Polysplenia syndrome was diagnosed based on the CT and postmortem findings.

Conclusion

We defined the positions of the abdominal organs and morphological abnormalities in various organs of a calf with polysplenia syndrome based on CT and postmortem findings. These findings will improve understanding of the malpositioning and malformations that can occur in the organs of cattle with polysplenia syndrome.

Electronic supplementary material

The online version of this article (10.1186/s12917-017-1213-2) contains supplementary material, which is available to authorized users.

Cardiopulmonary Exercise Testing in Fontan Patients With and Without Isomerism (Heterotaxy) as Compared to Patients With Primary Ciliary Dyskinesia and Subjects With Structurally Normal Hearts

Isomerism, also known as heterotaxy, is a clinical entity that impacts multiple organ systems both anatomically and functionally. The airways and lungs are involved in a great number of these patients, leading to increased sinopulmonary symptoms, increased need for oxygenation, and increased postoperative ventilatory support. Additionally, these patients often have congenital heart disease requiring Fontan palliation. What has not been previously described, and is the focus of this study, is the results of cardiopulmonary exercise testing in those who have undergone Fontan palliation with and without isomerism. We have now compared these finding with those from patients with primary ciliary dyskinesia, as many patients with isomerism have ciliary dyskinesia. We identified patients having the Fontan circulation with and without isomerism who had undergone cardiopulmonary exercise testing, comparing the findings from healthy individuals undergoing exercise, and a comparable number of individuals with primary ciliary dyskinesia but no congenital heart disease. We were able to include a total of 68 patients in our study, with 17 in each of the four groups. Cardiopulmonary exercise testing yielded the best results in healthy patients. All patients with the Fontan circulation demonstrated mixed pulmonary disease, although those with isomerism had greater FVC and FEV1. Exercise times did not differ, although peak consumption of oxygen was greater in those with isomerism. Those with ciliary dyskinesia had only obstructive pulmonary disease and had the lowest FEF25-75 between all groups. Those with isomerism had a lesser degree of obstructive pulmonary disease when compared to those with primary ciliary dyskinesia. Patients with the Fontan circulation with and without isomerism have relatively subtle differences in their cardiopulmonary exercise testing, with both groups demonstrating restrictive lung disease. In regard to obstructive lung disease, those with isomerism tend to be more similar to the patients with primary ciliary dyskinesia than those with the Fontan circulation but without isomerism. The results are likely limited by selection bias and highlight the need for multicentric efforts to characterize cardiopulmonary exercise testing in those patients with pulmonary isomerism.