Heterotaxy Patients Research Articles

Outcomes of heart transplantation in children with heterotaxy syndrome.

End-stage congenital heart disease in children with heterotaxy syndrome might necessitate heart transplantation. Heart transplantation in heterotaxy patients can be associated with several technical (e.g. redo, systemic/pulmonary-venous/situs anomalies, pulmonary artery reconstruction), and extra-cardiac (e.g. ciliary dyskinesia, infections, gastrointestinal) challenges. We aim to examine if heterotaxy syndrome is associated with increased early or late transplantation risks. The United Network for Organ Sharing transplantation database was merged with the Paediatric Health Information System administrative database to identify children with heterotaxy who received heart transplantation. Characteristics and outcomes were compared between children with heterotaxy and contemporaneous non-heterotaxy congenital and non-congenital cardiomyopathy control groups. After merger, our cohort of 1122 patients was divided to three groups: group heterotaxy (n = 143), group non-heterotaxy congenital (n = 428) and group cardiomyopathy (n = 551). There were differences in the characteristics between the 3 groups, with heterotaxy being comparable to non-heterotaxy congenital group. The waitlist duration was longer for heterotaxy than non-heterotaxy congenital and cardiomyopathy groups (91 vs 63 vs 56 days, p < 0.001). Early post-transplant complications were similar for all groups except for operative mortality that was 1% for cardiomyopathy and 4% for heterotaxy and non-heterotaxy congenital, p < 0.001. Post-transplant stay was shorter for cardiomyopathy (57) compared to non-heterotaxy congenital (99) and heterotaxy (89) days, p < 0.001. While rejection prior to discharge was comparable between heterotaxy and CHD groups, it was higher at 1-year for heterotaxy (22%), than non-heterotaxy congenital (19%) and cardiomyopathy (13%), p < 0.001. Survival at 5 years was superior for cardiomyopathy (87%) compared to heterotaxy (69%) and non-heterotaxy congenital (78%), p < 0.001. For the heterotaxy group, no risk factors affecting survival were identified on multivariable analysis. Despite complexity, heart transplantation in selected children with heterotaxy is associated with good mid-term outcomes. Despite early results that are comparable to other patients with congenital heart disease, the increasing rejection rate at one year and the relatively accelerated attrition at mid-term warrant further follow-up. Due to database limitations in defining morphologic and surgical details, further work is warranted to delineate anatomic and surgical variables that could affect survival.

A novel NODAL variant in a young embolic stroke patient with visceral heterotaxy

BackgroundIschemic stroke in young adults can be caused by a variety of etiologies including the monogenic disorders. Visceral heterotaxy is a condition caused by abnormal left–right determinations during embryonic development. We aimed to determine the cause of a young ischemic stroke patient with visceral heterotaxy.Case presentationWe performed neurological, radiological, and genetic evaluations in a 17-year-old male patient presenting ischemic stroke and visceral heterotaxy to determine the underlying cause of this rare disease combination. Brain magnetic resonance imaging (MRI) showed evidence of embolic stroke, abdominal computed tomography (CT) showed visceral heterotaxy, and echocardiogram showed cardiac anomaly with right-to-left-shunt (RLS). Whole genome sequencing (WGS) revealed a heterozygous missense variant (NM_018055.5: c.1016 T > C, p.(Met339Val)) in the NODAL gene, which is essential to the determination of the left–right body axis.ConclusionsOur study highlights the importance of evaluating genetic etiology in young ischemic stroke and the need for stroke risk management in visceral heterotaxy patients with RLS. To the best of our knowledge, we report the first genetically-confirmed case of visceral heterotaxy with young embolic stroke reported to date.

Clinical implications of respiratory ciliary dysfunction in heterotaxy patients with congenital heart disease: elevated risk of postoperative airway complications.

Cardiac surgery in Congenital Heart Disease-Heterotaxy (CHD-HTX) patients often leads to increased postoperative airway complications. Abnormal respiratory ciliary function, resembling primary ciliary dyskinesia, has been observed. We expanded the sample size by retrospectively reviewing Ciliary Dysfunction (CD) in CHD-HTX patients to verify the increased risk of post-surgical respiratory complications. We conducted a retrospective review of 69 CHD-HTX patients undergoing cardiac surgery, assessing abnormal respiratory function using nasal nitric oxide (nNO) levels and nasal ciliary motion observed in video microscopy. Data collected included demographics, surgical details, postoperative complications, length of stay, ICU hours, salvage procedures, intubation duration, and mortality. The CD and no-CD cohorts exhibited notable similarities in risk adjustment in Congenital Heart Surgery-1 (RACHS-1) risk categories, age at the time of surgery, and the duration of follow-up evaluations. We observed a trend toward an increased length of post-operative stay in the CD group (15.0 vs. 14.0; P = 0.0017). CHD-HTX patients with CD showed significantly higher rates of respiratory complications (70% vs. 44.4%; P = 0.008). There were no notable variances observed in postoperative hospitalization duration, mechanical ventilation period, or surgical mortality. Our findings suggest that CHD-HTX patients with CD may face an elevated risk of respiratory complications. These results offer guidance for perioperative management and serve as a reference for further pathological studies.

Functions of cilia in cardiac development and disease.

Errors in embryonic cardiac development are a leading cause of congenital heart defects (CHDs), including morphological abnormalities of the heart that are often detected after birth. In the past few decades, an emerging role for cilia in the pathogenesis of CHD has been identified, but this topic still largely remains an unexplored area. Mouse forward genetic screens and whole exome sequencing analysis of CHD patients have identified enrichment for de novo mutations in ciliary genes or non-ciliary genes, which regulate cilia-related pathways, linking cilia function to aberrant cardiac development. Key events in cardiac morphogenesis, including left-right asymmetric development of the heart, are dependent upon cilia function. Cilia dysfunction during left-right axis formation contributes to CHD as evidenced by the substantial proportion of heterotaxy patients displaying complex CHD. Cilia-transduced signaling also regulates later events during heart development such as cardiac valve formation, outflow tract septation, ventricle development, and atrioventricular septa formation. In this review, we summarize the role of motile and non-motile (primary cilia) in cardiac asymmetry establishment and later events during heart development.

Contemporary Outcomes of Heart Transplantation in Children with Heterotaxy Syndrome: Sub-Optimal Pre-Transplant Optimization Translates into Early Post-Transplant Mortality.

Patients with heterotaxy syndrome and congenital heart disease (CHD) experience inferior cardiac surgical outcomes. Heart transplantation outcomes are understudied, however, particularly compared to non-CHD patients. Data from UNOS and PHIS were used to identify 4803 children (< 18years) undergoing first-time heart transplant between 2003 and 2022 with diagnoses of heterotaxy (n = 278), other-CHD (n = 2236), and non-CHD cardiomyopathy (n = 2289). Heterotaxy patients were older (median 5yr) and heavier (median 17kg) at transplant than other-CHD (median 2yr and 12kg), and younger and lighter than cardiomyopathy (median 7yr and 24kg) (all p < 0.001). UNOS status 1A/1 at listing was not different between groups (65-67%; p = 0.683). At transplant, heterotaxy and other-CHD patients had similar rates of renal dysfunction (12 and 17%), inotropes (10% and 11%), and ventilator-dependence (19 and 18%). Compared to cardiomyopathy, heterotaxy patients had comparable renal dysfunction (9%, p = 0.058) and inotropes (46%, p = 0.097) but more hepatic dysfunction (17%, p < 0.001) and ventilator-dependence (12%, p = 0.003). Rates of ventricular assist device (VAD) were: heterotaxy-10%, other-CHD-11% (p = 0.839 vs. heterotaxy), cardiomyopathy-37% (p < 0.001 vs. heterotaxy). The 1-year incidence of acute rejection post-transplant was comparable between heterotaxy and others (p > 0.05). While overall post-transplant survival was significantly worse for heterotaxy than others (p < 0.05 vs. both), conditional 1-year survival was comparable (p > 0.3 vs. both). Children with heterotaxy syndrome experience inferior post-heart transplant survival, although early mortality appears to influence this trend, with 1-year survivors having equivalent outcomes. Given similar pre-transplant clinical status to others, heterotaxy patients are potentially under risk-stratified. Increased VAD utilization and pre-transplant end-organ function optimization may portend improved outcomes.

Genetic and Clinical Features of Heterotaxy in a Prenatal Cohort.

Objectives: Some genetic causes of heterotaxy have been identified in a small number of heterotaxy familial cases or animal models. However, knowledge on the genetic causes of heterotaxy in the fetal population remains scarce. Here, we aimed to investigate the clinical characteristics and genetic spectrum of a fetal cohort with heterotaxy. Methods: We retrospectively investigated all fetuses with a prenatal diagnosis of heterotaxy at a single center between October 2015 and November 2020. These cases were studied using the genetic testing data acquired from a combination of copy number variation sequencing (CNV-seq) and whole-exome sequencing (WES), and their clinical phenotypes were also reviewed. Result: A total of 72 fetuses diagnosed with heterotaxy and complete clinical and genetic results were enrolled in our research. Of the 72 fetuses, 18 (25%) and 54 (75%) had left and right isomerism, respectively. Consistent with the results of a previous study, intracardiac anomalies were more severe in patients with right atrial isomerism than in those with left atrial isomerism (LAI) and mainly manifested as atrial situs inversus, bilateral right atrial appendages, abnormal pulmonary venous connection, single ventricles or single atria, and pulmonary stenosis or atresia. In 18 fetuses diagnosed with LAI, the main intracardiac anomalies were bilateral left atrial appendages. Of the 72 fetuses that underwent CNV-seq and WES, 11 (15.3%) had positive genetic results, eight had definitive pathogenic variants, and three had likely pathogenic variants. The diagnostic genetic variant rate identified using WES was 11.1% (8/72), in which primary ciliary dyskinesia (PCD)-associated gene mutations (CCDC40, CCDC114, DNAH5, DNAH11, and ARMC4) accounted for the vast majority (n = 5). Other diagnostic genetic variants, such as KMT2D and FOXC1, have been rarely reported in heterotaxy cases, although they have been verified to play roles in congenital heart disease. Conclusion: Thus, diagnostic genetic variants contributed to a substantial fraction in the etiology of fetal heterotaxy. PCD mutations accounted for approximately 6.9% of heterotaxy cases in our fetal cohort. WES was identified as an effective tool to detect genetic causes prenatally in heterotaxy patients.

Comparable long-term results of the extracardiac conduit total cavopulmonary connection in heterotaxy to non-heterotaxy patients.

Fontan operation in heterotaxy patients has been associated with high mortality. We studied whether adoption of the extracardiac conduit (EC) total cavopulmonary connection (TCPC)in heterotaxy demonstrated comparable results to non-heterotaxy population. A retrospective medical record review of 35 consecutive patients with heterotaxy and 70 consecutive patients without heterotaxy syndrome who underwent EC TCPC between 2000 and 2018 was performed. In the 35 heterotaxy patients, 30 were right and 5 were left atrial isomerism. Anomalies of venous return included bilateral superior vena cava in 20 (57.1%), separated hepatic vein in 8 (22.9%), interrupted inferior vena cava in 3 (8.6%), total anomalous pulmonary venous return in 7 (20%), and partial in 2 patients (5.7%). All patients underwent EC TCPC under beating-heart cardiopulmonary bypass except in four patients (11.4%) cardioplegic arrest was needed for cardiac repair. The surgical mortality rate was lower in heterotaxy patients (0% vs. 5.7%; p = 0.299) but statistically not significant. The follow-up ranged from 2 months to 17.8 years (mean 9.4 ± 5.6 years). At 15 years, there was no significant difference between the heterotaxy and non-heterotaxy patients regarding the long-term survival (70% vs. 78.6%; p = 0.443), freedom from reoperation (81.9% vs. 96.5%; p = 0.057), and postoperative arrhythmia (17.1% vs. 7.1%; p = 0.174). EC TCPC can be performed in heterotaxy patients with comparable early and late results to the non-heterotaxy population. However, the late morbidities regarding the Fontan circulation needs careful follow-up.

Improved heart transplant survival for children with congenital heart disease and heterotaxy syndrome in the current era: An analysis from the pediatric heart transplant society

Challenges exist with heterotaxy due to the complexity of heart disease, abnormal venous connections, and infection risks. This study aims to understand heart transplant outcomes for children with heterotaxy. All children with congenital heart disease listed for transplant from 1993 to 2018 were included. Those with and without heterotaxy were compared. Waitlist outcomes and survival post-listing and transplant were analyzed. Post-transplant risk factors were identified using multiphase parametric hazard modeling. There were 4814 children listed, of whom 196 (4%) had heterotaxy. Heterotaxy candidates were older (5.8 ± 5.7 vs 4.2 ± 5.5 years, p < 0.01), listed at a lower urgency status (29.8% vs 18.4%, p < 0.01), more commonly single ventricle physiology (71.3% vs 59.2%, p < 0.01), and less often supported by mechanical ventilation (22% vs 29.1%, p < 0.05) or extracorporeal membrane oxygenation (3.6% vs 7.5%, p < 0.05). There were no differences in waitlist outcomes of transplant, death, or removal. Overall, post-transplant survival was worse for children with heterotaxy: one-year survival 77.2% vs 85.1%, with and without heterotaxy, respectively. Heterotaxy was an independent predictor for early mortality in the earliest era (1993-2004), HR 2.09, CI 1.16-3.75, p=0.014. When stratified by era, survival improved with time. Heterotaxy patients had a lower freedom from infection and from severe rejection, but no difference in vasculopathy or malignancy. Mortality risk associated with heterotaxy is mitigated in the recent transplant era. Early referral may improve waitlist outcomes for heterotaxy patients who otherwise have a lower status at listing. Lower freedom from both infection and severe rejection after transplant in heterotaxy highlights the challenges of balancing immune suppression.

Off-pump direct hepatic veins-to-hemiazygos vein anastomosis after primary Kawashima operation: long-term result.

Direct hepatic veins-to-hemiazygos connection offers the balanced distribution of hepatic venous blood to both lungs, not requiring anticoagulation. We report a 13-year follow-up after this type of off-pump Fontan completion. Patient's hepatic veins-to-hemiazygos confluence increased with growth to allow for unobstructed flow. This unique technique can be recommended in heterotaxy patients, if atrial hepatic venous drainage and hemiazygos vein are in close proximity.

Early outcomes of usage of cryoFORM® probe for cryomaze procedure in congenital heart surgery.

This study aimed to evaluate the early outcomes of patients who underwent a concomitant therapeutic maze procedure for congenital heart surgery. Between 2019 and 2020, eight patients underwent surgical cryoablation by using the same type of cryoablation probe. Three patients had atrial flutter, two had Wolf-Parkinson-White syndrome, two intra-atrial reentrant tachycardia, and one had atrial fibrillation. Four patients underwent electrophysiological study. Preoperatively, one patient was on 3, two were on 2, five were on 1 antiarrhythmic drug. Six patients underwent right atrial maze and two underwent bilateral atrial maze. Five out of six right atrial maze patients underwent right atrial reduction. Nine different lesion sets were used. Some of the lesions were combined and applied as one lesion. In Ebstein's anomaly patients, the lesion from coronary sinus to displaced tricuspid annulus was delicately performed. The single ventricle patient with heterotaxy had junctional rhythm at the time of discharge and was the only patient who experienced atrial extrasystoles 2 months after discharge. Seven of the eight patients were on sinus rhythm. No patient needed permanent pacemaker placement. Cryomaze procedure can be applied in congenital heart diseases with acceptable arrhythmia-free rates by selecting the appropriate materials and suitable lesion sets. The application of cryomaze in heterotaxy patients can be challenging due to differences in the conduction system and complex anatomy. Consensus with the electrophysiology team about the choice of the right-left or biatrial maze procedure is mandatory for operational success.

En Bloc Combined Heart and Liver Transplantation for End-Stage Heart Failure

Combined heart-liver transplant (CHLTx) remains the only option for long-term survival in patients with end-stage heart and hepatic failure. To date, there are a limited number of transplant centers in the United States that have conducted a CHLTx. Between July of 2009 and December 2019, our group has performed the largest series (N = 20) of <i>en bloc</i> CHLTx to date. En block combined heart-liver transplantation offers both grafts the opportunity to minimize dysfunction with shorter ischemic time compared to sequential heart-liver transplant. This technique simplifies the surgery in patients with complex venous anatomy such as heterotaxy patients and can be performed in dextrocardia or levocardia patients, irrespective of the side of inferior vena cava or superior vena cava. We describe our indications and detailed en block technique for combined heart-liver with its midterm outcome.

Imbalanced mitochondrial function provokes heterotaxy via aberrant ciliogenesis.

About 1% of all newborns are affected by congenital heart disease (CHD). Recent findings identify aberrantly functioning cilia as a possible source for CHD. Faulty cilia also prevent the development of proper left-right asymmetry and cause heterotaxy, the incorrect placement of visceral organs. Intriguingly, signaling cascades such as mTor that influence mitochondrial biogenesis also affect ciliogenesis, and can cause heterotaxy-like phenotypes in zebrafish. Here, we identify levels of mitochondrial function as a determinant for ciliogenesis and a cause for heterotaxy. We detected reduced mitochondrial DNA content in biopsies of heterotaxy patients. Manipulation of mitochondrial function revealed a reciprocal influence on ciliogenesis and affected cilia-dependent processes in zebrafish, human fibroblasts and Tetrahymena thermophila. Exome analysis of heterotaxy patients revealed an increased burden of rare damaging variants in mitochondria-associated genes as compared to 1000 Genome controls. Knockdown of such candidate genes caused cilia elongation and ciliopathy-like phenotypes in zebrafish, which could not be rescued by RNA encoding damaging rare variants identified in heterotaxy patients. Our findings suggest that ciliogenesis is coupled to the abundance and function of mitochondria. Our data further reveal disturbed mitochondrial function as an underlying cause for heterotaxy-linked CHD and provide a mechanism for unexplained phenotypes of mitochondrial disease.

Abstract 16914: Structural and Functional Investigation of Myocardial Fiber Architecture in Genetic Mouse Models of Heterodoxy and Situs Inverses Totalis

Introduction: Heterotaxy (HTX) patients with congenital heart disease have higher risk of post-surgical complications and increased morbidity and mortality. Given HTX involves disruption of left-right patterning, this suggests laterality disturbance may drive the poor outcome in CHD patients with HTX. To investigate this, we used mouse models with laterality defects. Although HTX mutant mice invariably die prenatally/neonatlly from complex CHD, many mutations causing HTX also giive rise to mice that are adult viable with situs inversus totalis (SIT), or situs solitus (SS) without CHD. Hence, our goal is to delineate myocardial fiber architecture in the SIT and SS mutant mice to gain insights into possible functional deficits associated with HTX. Hypothesis: Disturbance in specification of laterality results in abnormal myocardial fiber architecture that can cause cardiac dysfunction and make the heart more vulnerable to stress. Methods: Diffusion tensor imaging (DTI) was used to delineate the myocardial fiber organization in SIT and SS mutant mice, and wild-type (WT) control mice. Cardiac MRI and echocardiography were used to evaluate cardiac function with or without dobutamine stress. Results: Echocardiography showed no significant differences in global systolic function in the SIT and SS mutant hearts, but they displayed compromised strain rates under dobutamine stress. SIT and SS hearts also exhibited reduced rotation and torsion, suggesting altered myocardial fiber organization. Myocardial tractography by DTI (Fig.A-D) showed less coherent myocardial fiber organization (Fig. G-I) and more diverse helix angles (Fig. K&amp;M) in SIT mutant hearts. Overall, our data showed the mutant SS and SIT hearts have disrupted myocardial fiber architecture resulting in abnormal torsion, rotation, and strain when stressed. Conclusions: These findings suggest abnormal myocardial architecture may contribute to the poor clinical outcome in HTX patients with CHD.

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.

Improving outcomes of patients with heterotaxy and functional single ventricle: a 10-year follow-up of 70 cases in a single institution

Objective: To review current-era palliation outcomes of patients with heterotaxy and functional single ventricle in a single institution. Methods: The clinical data of 70 consecutive patients with heterotaxy undergoing multistage single ventricle palliation in Guangzhou Women and Children's Medical Center from January 2008 to December 2017 were retrospectively reviewed, and the prognosis factors for mortality were analyzed. There were 53 male and 17 female patients.The median age was 13.3 months (range: 6 days to 150 months). Single ventricle multistage palliation included 1(st) stage palliation surgery, 2(nd) bidirectional Glenn shunt, and 3(rd) stage modified Fontan.The Kaplan-Meier method was used to estimate the probability of survival. Multivariate analysis was performed by Cox regression model. Results: Sixty-two patients had right atrial isomerism while eight had left atrial isomerism. Eighteen patients (25.7%) required the first stage palliation. Fifty-five patients received the Glenn shunt, and the Fontan procedure was completed in 27 patients. Overall, mortality occurred in 17 patients (24.3%) including 9 after the first stage palliation, 6 after the Glenn shunt, and 2 following the Fontan procedure. Survival estimates for the entire cohort following surgery were 81% (95%CI: 72% to 90%), 74%(95%CI: 64% to 85%), and 74% (95%CI: 64% to 85%) at 1 year, 5 years and 10 years, respectively. Survival estimates following the first stage palliation were 56% (95%CI: 33% to 79%) and 49% (95%CI: 26% to 73%) at 1 year and 5 years, respectively. Multivariate Cox regression analysis revealed that total anomalous pulmonary venous connection (TAPVC) (HR=6.16, 95%CI: 1.65 to 22.95, P=0.007), atrioventricular valve regurgitation more than moderate (HR=3.81, 95%CI: 1.32 to 10.94, P=0.013) and required the first palliation surgery (HR=4.58, 95%CI: 1.34 to 15.72, P=0.016) were prognosis factors for overall mortality. Conclusions: The management of heterotaxy patients with functional single ventricle remains challenging, and the outcomes are continously improving in china. TAPVC, atrioventricular valve regurgitation more than moderate and required the first palliation surgery still are prognosis factors for overall mortality in heterotaxy syndrome.

Airway ciliary dysfunction and respiratory symptoms in patients with transposition of the great arteries.

BackgroundOur prior work on congenital heart disease (CHD) with heterotaxy, a birth defect involving randomized left-right patterning, has shown an association of a high prevalence of airway ciliary dysfunction (CD; 18/43 or 42%) with increased respiratory symptoms. Furthermore, heterotaxy patients with ciliary dysfunction were shown to have more postsurgical pulmonary morbidities. These findings are likely a reflection of the common role of motile cilia in both airway clearance and left-right patterning. As CHD comprising transposition of the great arteries (TGA) is commonly thought to involve disturbance of left-right patterning, especially L-TGA with left-right ventricular inversion, we hypothesize CHD patients with transposition of great arteries (TGA) may have high prevalence of airway CD with increased respiratory symptoms.Methods and resultsWe recruited 75 CHD patients with isolated TGA, 28% L and 72% D-TGA. Patients were assessed using two tests typically used for evaluating airway ciliary dysfunction in patients with primary ciliary dyskinesia (PCD), a recessive sinopulmonary disease caused by respiratory ciliary dysfunction. This entailed the measurement of nasal nitric oxide (nNO), which is typically low with PCD. We also obtained nasal scrapes and conducted videomicroscopy to assess respiratory ciliary motion (CM). We observed low nNO in 29% of the patients, and abnormal CM in 57%, with 22% showing both low nNO and abnormal CM. No difference was observed for the prevalence of either low nNO or abnormal ciliary motion between patients with D vs. L-TGA. Respiratory symptoms were increased with abnormal CM, but not low nNO. Sequencing analysis showed no compound heterozygous or homozygous mutations in 39 genes known to cause PCD, nor in CFTR, gene causing cystic fibrosis. As both are recessive disorders, these results indicate TGA patients with ciliary dysfunction do not have PCD or cystic fibrosis (which can cause low nNO or abnormal ciliary motion).ConclusionsTGA patients have high prevalence of abnormal CM and low nNO, but ciliary dysfunction was not correlated with TGA type. Differing from PCD, respiratory symptoms were increased with abnormal CM, but not low nNO. Together with the negative findings from exome sequencing analysis, this would suggest TGA patients with ciliary dysfunction do not have PCD but nevertheless may suffer from milder airway clearance deficiency. Further studies are needed to investigate whether such ciliary dysfunction is associated with increased postsurgical complications as previously observed in CHD patients with heterotaxy.

High burden of genetic conditions diagnosed in a cardiac neurodevelopmental clinic.

There is a known high prevalence of genetic and clinical syndrome diagnoses in the paediatric cardiac population. These disorders often have multisystem effects, which may have an important impact on neurodevelopmental outcomes. Taken together, these facts suggest that patients and families may benefit from consultation by genetic specialists in a cardiac neurodevelopmental clinic. This study assessed the burden of genetic disorders and utility of genetics evaluation in a cardiac neurodevelopmental clinic. A retrospective chart review was conducted of patients evaluated in a cardiac neurodevelopmental clinic from 6 December, 2011 to 16 April, 2013. All patients were seen by a cardiovascular geneticist with genetic counselling support. A total of 214 patients were included in this study; 64 of these patients had a pre-existing genetic or syndromic diagnosis. Following genetics evaluation, an additional 19 were given a new clinical or laboratory-confirmed genetic diagnosis including environmental such as teratogenic exposures, malformation associations, chromosomal disorders, and single-gene disorders. Genetic testing was recommended for 112 patients; radiological imaging to screen for congenital anomalies for 17 patients; subspecialist medical referrals for 73 patients; and non-genetic clinical laboratory testing for 14 patients. Syndrome-specific guidelines were available and followed for 25 patients with known diagnosis. American Academy of Pediatrics Red Book asplenia guideline recommendations were given for five heterotaxy patients, and family-based cardiac screening was recommended for 23 families affected by left ventricular outflow tract obstruction. Genetics involvement in a cardiac neurodevelopmental clinic is helpful in identifying new unifying diagnoses and providing syndrome-specific care, which may impact the patient's overall health status and neurodevelopmental outcome.

The analysis of heterotaxy patients reveals new loss-of-function variants of GRK5.

G protein-coupled receptor kinase 5 (GRK5) is a regulator of cardiac performance and a potential therapeutic target in heart failure in the adult. Additionally, we have previously classified GRK5 as a determinant of left-right asymmetry and proper heart development using zebrafish. We thus aimed to identify GRK5 variants of functional significance by analysing 187 individuals with laterality defects (heterotaxy) that were associated with a congenital heart defect (CHD). Using Sanger sequencing we identified two moderately frequent variants in GRK5 with minor allele frequencies <10%, and seven very rare polymorphisms with minor allele frequencies <1%, two of which are novel variants. Given their evolutionarily conserved position in zebrafish, in-depth functional characterisation of four variants (p.Q41L, p.G298S, p.R304C and p.T425M) was performed. We tested the effects of these variants on normal subcellular localisation and the ability to desensitise receptor signalling as well as their ability to correct the left-right asymmetry defect upon Grk5l knockdown in zebrafish. While p.Q41L, p.R304C and p.T425M responded normally in the first two aspects, neither p.Q41L nor p.R304C were capable of rescuing the lateralisation phenotype. The fourth variant, p.G298S was identified as a complete loss-of-function variant in all assays and provides insight into the functions of GRK5.

Bacteremia in Patients with Heterotaxy: A Review and Implications for Management

Heterotaxy (HTX) is a laterality defect resulting in abnormal arrangement of the thoracic and abdominal organs across the right-left axis, and is associated with multiple anatomic and physiologic disruptions. HTX often occurs in association with complex congenital heart disease. Splenic abnormalities are also common and convey an increased risk of bacteremia (bacteremia) with a high associated mortality. We performed a systematic review of the literature studying the risk of infection in HTX patients and strategies that can be utilized to prevent such infections. Studies were identified for inclusion using PubMed, EMBASE, and OVID, as well as hand search of references from previously identified papers. Published studies specifically investigating bacteremia in HTX were identified and included as long as they were in English. Data were extracted by two separate authors independently with review of any findings that differed between the two authors. There were 42 documented cases of bacteremia in 32 patients. Approximately, 79% of these had absence of a spleen. The average age of bacteremia was 17 months. HTX patients are at high risk for bacteremia leading to mortality, regardless of anatomic splenic type. We propose strategies for the evaluation of splenic function in HTX patients, and review management practices to reduce the impact of infection risk in the HTX population.

DNAH6 and Its Interactions with PCD Genes in Heterotaxy and Primary Ciliary Dyskinesia.

Heterotaxy, a birth defect involving left-right patterning defects, and primary ciliary dyskinesia (PCD), a sinopulmonary disease with dyskinetic/immotile cilia in the airway are seemingly disparate diseases. However, they have an overlapping genetic etiology involving mutations in cilia genes, a reflection of the common requirement for motile cilia in left-right patterning and airway clearance. While PCD is a monogenic recessive disorder, heterotaxy has a more complex, largely non-monogenic etiology. In this study, we show mutations in the novel dynein gene DNAH6 can cause heterotaxy and ciliary dysfunction similar to PCD. We provide the first evidence that trans-heterozygous interactions between DNAH6 and other PCD genes potentially can cause heterotaxy. DNAH6 was initially identified as a candidate heterotaxy/PCD gene by filtering exome-sequencing data from 25 heterotaxy patients stratified by whether they have airway motile cilia defects. dnah6 morpholino knockdown in zebrafish disrupted motile cilia in Kupffer’s vesicle required for left-right patterning and caused heterotaxy with abnormal cardiac/gut looping. Similarly DNAH6 shRNA knockdown disrupted motile cilia in human and mouse respiratory epithelia. Notably a heterotaxy patient harboring heterozygous DNAH6 mutation was identified to also carry a rare heterozygous PCD-causing DNAI1 mutation, suggesting a DNAH6/DNAI1 trans-heterozygous interaction. Furthermore, sequencing of 149 additional heterotaxy patients showed 5 of 6 patients with heterozygous DNAH6 mutations also had heterozygous mutations in DNAH5 or other PCD genes. We functionally assayed for DNAH6/DNAH5 and DNAH6/DNAI1 trans-heterozygous interactions using subthreshold double-morpholino knockdown in zebrafish and showed this caused heterotaxy. Similarly, subthreshold siRNA knockdown of Dnah6 in heterozygous Dnah5 or Dnai1 mutant mouse respiratory epithelia disrupted motile cilia function. Together, these findings support an oligogenic disease model with broad relevance for further interrogating the genetic etiology of human ciliopathies.