Management of Congenital Heart Disease: State of the Art-Part II-Cyanotic Heart Defects

Deamidation enables pathogenic SMAD6 variants to activate the BMP signaling pathway

The BMP signaling pathway plays a crucial role in regulating early embryonic development and tissue homeostasis. SMAD6 encodes a negative regulator of BMP, and rare variants of SMAD6 are recurrently found in individuals with birth defects. However, we observed that a subset of rare pathogenic variants of SMAD6 consistently exhibited positive regulatory effects instead of the initial negative effects on the BMP signaling pathway. We sought to determine whether these SMAD6 variants have common pathogenic mechanisms. Here, we showed that pathogenic SMAD6 variants accompanying this functional reversal exhibit similar increases in deamidation. Mechanistically, increased deamidation of SMAD6 variants promotes the accumulation of the BMP receptor BMPR1A and the formation of new complexes, both of which lead to BMP signaling pathway activation. Specifically, two residues, N262 and N404, in SMAD6 were identified as the crucial sites of deamidation, which was catalyzed primarily by glutamine-fructose-6-phosphate transaminase 2 (GFPT2). Additionally, treatment of cells harboring SMAD6 variants with a deamidase inhibitor restored the inhibitory effect of SMAD6 on the BMP signaling pathway. Conversely, when wild-type SMAD6 was manually simulated to mimic the deamidated state, the reversed function of activating BMP signaling was reproduced. Taken together, these findings show that deamidation of SMAD6 plays a crucial role in the functional reversal of BMP signaling activity, which can be induced by a subset of various SMAD6 variants. Our study reveals a common pathogenic mechanism shared by these variants and provides a potential strategy for preventing birth defects through deamidation regulation, which might prevent the off-target effects of gene editing.

Recent Advances in Hydrogel-Based 3D Bioprinting and Its Potential Application in the Treatment of Congenital Heart Disease

Congenital heart disease (CHD) is the most common birth defect, requiring invasive surgery often before a child's first birthday. Current materials used during CHD surgery lack the ability to grow, remodel, and regenerate. To solve those limitations, 3D bioprinting is an emerging tool with the capability to create tailored constructs based on patients' own imaging data with the ability to grow and remodel once implanted in children with CHD. It has the potential to integrate multiple bioinks with several cell types and biomolecules within 3D-bioprinted constructs that exhibit good structural fidelity, stability, and mechanical integrity. This review gives an overview of CHD and recent advancements in 3D bioprinting technologies with potential use in the treatment of CHD. Moreover, the selection of appropriate biomaterials based on their chemical, physical, and biological properties that are further manipulated to suit their application are also discussed. An introduction to bioink formulations composed of various biomaterials with emphasis on multiple cell types and biomolecules is briefly overviewed. Vasculogenesis and angiogenesis of prefabricated 3D-bioprinted structures and novel 4D printing technology are also summarized. Finally, we discuss several restrictions and our perspective on future directions in 3D bioprinting technologies in the treatment of CHD.

Homozygous SMAD6 variants in two unrelated patients with craniosynostosis and radioulnar synostosis

BACKGROUND

SMAD6 encodes an intracellular inhibitor of the bone morphogenetic protein (BMP) signalling pathway. Until now, rare heterozygous loss-of-function variants in SMAD6 were demonstrated to increase the risk of disparate clinical disorders including cardiovascular disease, craniosynostosis and radioulnar synostosis. Only two unrelated patients harbouring biallelic SMAD6 variants presenting a complex cardiovascular phenotype and facial dysmorphism have been described.

CASES

Here, we present the first two patients with craniosynostosis harbouring homozygous SMAD6 variants. The male probands, both born to healthy consanguineous parents, were diagnosed with metopic synostosis and bilateral or unilateral radioulnar synostosis. Additionally, one proband had global developmental delay. Echocardiographic evaluation did not reveal cardiac or outflow tract abnormalities.

MOLECULAR ANALYSES

The novel missense (c.[584T>G];[584T>G], p.[(Val195Gly)];[(Val195Gly)]) and missense/splice-site variant (c.[817G>A];[817G>A], r.[(817g>a,817delins[a;817+2_817+228])];[(817g>a,817delins[a;817+2_817+228])], p.[(Glu273Lys,Glu273Serfs*72)];[(Glu273Lys,Glu273Serfs*72)]) both locate in the functional MH1 domain of the protein and have not been reported in gnomAD database. Functional analyses of the variants showed reduced inhibition of BMP signalling or abnormal splicing, respectively, consistent with a hypomorphic mechanism of action.

CONCLUSION

Our data expand the spectrum of variants and phenotypic spectrum associated with homozygous variants of SMAD6 to include craniosynostosis.

Adult With Unrepaired Single-Ventricle Defect

This case report discusses the diagnosis of double-inlet left ventricle in a male adult patient in his 50s who presented with New York Heart Association class III heart failure.

Prenatal Diagnosis, Associated Findings, and Postnatal Outcome in Fetuses with Double Inlet Ventricle (DIV)

PURPOSE

To assess the spectrum of associated cardiac anomalies, the intrauterine course, and postnatal outcome of fetuses with double inlet ventricle (DIV).

METHODS

Retrospective analysis of prenatal ultrasound of 35 patients with DIV diagnosed between 2003 and 2021 in two tertiary referral centers in Germany. All fetuses underwent fetal echocardiography and a detailed anomaly scan. Postnatal outcome and follow-up data were retrieved from pediatric reports.

RESULTS

33 cases of DIV were correctly diagnosed prenatally. 24 fetuses (72.7%) had a double inlet ventricle with dominant left (DILV), 7 (21.2%) with dominant right ventricular morphology (DIRV), and 2 cases (6%) with indeterminate morphology (DIIV). 4 (16.6%) were Holmes hearts. 5 of the 7 fetuses (71.4%) with DIRV had a double outlet right ventricle (DORV). Malposition of the great arteries was present in 84.8%. Chromosomal abnormalities were absent. Termination of pregnancy was performed in 8 cases (24.2%). 24 fetuses (72.7%) were live-born. 5 (20.8%) were female and 19 (79.2%) were male. The median gestational age at birth was 38+2.5 weeks. All but one child received univentricular palliation. The median follow-up time was 5.83 years with an adjusted survival rate of 91.6% (22 of 24 live-born children). There was one case of Fontan failure at 15.7 years.

CONCLUSION

DIV remains a major cardiac malformation although both prenatal diagnostics and cardiac surgery have improved over the years. The course of pregnancy is commonly uneventful. All children need univentricular palliation. The children are slightly physically limited, develop a normal intellect, and attend school regularly.

Assisted Reproductive Techniques and Risk of Congenital Heart Diseases in Children: a Systematic Review and Meta-analysis

Infertility is a growing phenomenon and leads to an increased use of assisted reproductive techniques (ARTs). In recent years, concerns about the safety of these procedures emerged and ARTs were hypothesized to be a risk factor for developing congenital heart diseases (CHDs) in offspring. Our aim is to investigate the association between ART and CHD, specifying results according to various subtypes of defects. We performed a systematic review and random-effects meta-analysis following the PRISMA guidelines. MEDLINE and Google Scholar were searched from January 2011 to May 2022. Data about incidence of CHD in ART were tabulated and extracted from all the studies included. Twenty-four studies were included. Pooled incidence of CHDs after IVF pregnancies was 3% (95% CI 0.3-0.4; I2 = 99%), decreasing to 1% (95% CI 0.00-0.01; I2 = 93%) for major CHDs only. An increased risk of CHDs, especially minor (i.e., not requiring surgical correction), seems to occur in ART compared with non-ART pregnancies [RR 1.71 (95% CI 1.25-2.34; I2 = 99%)]. For major CHDs, not enough evidence is available to assess the real risk. Moreover, some confounding factors (i.e., maternal age and male infertility) seem to play a critical role to determine an increased risk of CHDs. Conflicting results emerged among the studies, setting the need for further research to validate the actual evidence and state the real risk of CHD following ART pregnancies.

SMAD6-deficiency in human genetic disorders

SMAD6 encodes an intracellular inhibitor of the bone morphogenetic protein (BMP) signalling pathway. Until now, SMAD6-deficiency has been associated with three distinctive human congenital conditions, i.e., congenital heart diseases, including left ventricular obstruction and conotruncal defects, craniosynostosis and radioulnar synostosis. Intriguingly, a similar spectrum of heterozygous loss-of-function variants has been reported to cause these clinically distinct disorders without a genotype–phenotype correlation. Even identical nucleotide changes have been described in patients with either a cardiovascular phenotype, craniosynostosis or radioulnar synostosis. These findings suggest that the primary pathogenic variant alone cannot explain the resultant patient phenotype. In this review, we summarise clinical and (patho)genetic (dis)similarities between these three SMAD6-related conditions, compare published Madh6 mouse models, in which the importance and impact of the genetic background with respect to the observed phenotype is highlighted, and elaborate on the cellular key mechanisms orchestrated by SMAD6 in the development of these three discrete inherited disorders. In addition, we discuss future research needed to elucidate the pathogenetic mechanisms underlying these diseases in order to improve their molecular diagnosis, advance therapeutic strategies and facilitate counselling of patients and their families.

Institutional transition from invasive to non-invasive imaging in children with univentricular heart defects: safety and cost savings

OBJECTIVES

Patients with univentricular heart defects require lifelong imaging surveillance. Recent advances in non-invasive imaging have enabled replacing these patients' routine catheterisation. Our objective was to describe the safety and cost savings of transition of a tertiary care children's hospital from routine invasive to routine non-invasive imaging of low-risk patients with univentricular heart defects.

METHODS

This single-centre cohort study consists of 1) a retrospective analysis of the transition from cardiac catheterisation (n = 21) to CT angiography (n = 20) before bidirectional Glenn operation and 2) a prospective study (n = 89) describing cardiac magnetic resonance before and after the total cavopulmonary connection in low-risk patients with univentricular heart defects.

RESULTS

Pre-Glenn: The total length of CT angiography was markedly shorter compared to the catheterisation: 30 min (range: 20-60) and 125 min (range: 70-220), respectively (p < 0.001). Catheterisation used more iodine contrast agents than CT angiography, 19 ± 3.9 ml, and 10 ± 2.4 ml, respectively (p < 0.001). Controlled ventilation was used for all catheterised and 3 (15%) CT angiography patients (p < 0.001). No complications occurred during CT angiography, while they emerged in 19% (4/21) catheterisation cases (p < 0.001). CT angiography and catheterisation showed no significant difference in the radiation exposure. Pre-/post-total cavopulmonary connection: All cardiac magnetic resonance studies were successful, and no complications occurred. In 60% of the cardiac magnetic resonance (53/89), no sedation was performed, and peripheral venous pressure was measured in all cases. Cost analysis suggests that moving to non-invasive imaging yielded cost savings of at least €2500-4000 per patient.

CONCLUSION

Transition from routine invasive to routine non-invasive pre-and post-operative imaging is safely achievable with cost savings.

Preoperative Care of Neonates With Congenital Heart Disease

Congenital heart disease (CHD) is one of the most common types of birth defects, with 40,000 newborns diagnosed yearly in the United States. This article describes: (1) four common heart defects seen in neonatal intensive care units, (2) the typical medical/nursing care of these neonates, and (3) common surgical management for the defects. Hypoplastic left heart syndrome, dextro-transposition of the great arteries, tetralogy of Fallot, and pulmonary atresia with intact ventricular septum are four common types of CHD requiring NICU admission. Knowledge of these defects will help nurses to appropriately manage and treat neonates with these types of CHD.

Physiologically based pharmacokinetic modelling of acetaminophen in preterm neonates-The impact of metabolising enzyme ontogeny and reduced cardiac output

In preterm neonates, physiologically based pharmacokinetic (PBPK) models are suited for studying the effects of maturational and non-maturational factors on the pharmacokinetics of drugs with complex age-dependent metabolic pathways like acetaminophen (APAP). The aim of this study was to determine the impact of drug metabolising enzymes ontogeny on the pharmacokinetics of APAP in preterm neonates and to study the effect of reduced cardiac output (CO) on its PK using PBPK modelling. A PBPK model for APAP was first developed and validated in adults and then scaled to paediatric age groups to account for the effect of enzyme ontogeny. In preterm neonates, CO was reduced by 10%, 20%, and 30% to determine how this might affect APAP PK in preterm neonates. In all age groups, the predicted concentration-time profiles of APAP were within 5th and 95th percentile of the clinically observed concentration-time profiles and the predicted Cmax and AUC were within 2-folds of the reported parameters in clinical studies. Sulfation accounted for most of APAP metabolism in children, with the highest contribution of 68% in preterm neonates. A reduction in CO by up to 30% did not significantly alter the clearance of APAP in preterm neonates. The model successfully incorporated the ontogeny of drug metabolising enzymes involved in APAP metabolism and adequately predicted the PK of APAP in preterm neonates. A reduction in hepatic perfusion as a result of up to 30% reduction in CO has no effect on the PK of APAP in preterm neonates.

Ventricular septal defect: diagnosis and treatments in the neonates: a systematic review

BACKGROUND

Medical advancements have encouraged minimally invasive surgical repair of congenital heart defects such as ventricular septal defects (VSDs), and the diagnostic process can now be carried out using non-traditional techniques such as pulse oximetry. This, in turn, has improved clinical outcomes with reduced complication rates post-surgery. However, the variations in type of VSDs, age of patient, comorbidities, and access to closure devices may limit the efficacy of surgical advancements.

METHODS

Articles were identified amongst Scopus, MEDLINE, and PubMed using various relevant search strings using PRISMA guidelines. Of the 115 articles initially extracted, 10 were eventually reviewed after duplicates and irrelevant studies were removed.

RESULTS

Of the 24 eligible articles, 10 papers were selected for analysis. Minimally invasive approaches to VSD repair was associated with satisfactory short-term outcomes when compared to open repair. For diagnosis of congenital VSD, whilst recent advances such as pulse oximetry method and genome analysis are more sensitive, the limited availability and access to such investigatory methods must be recognised.

CONCLUSION

Pulse oximetry and fetal echocardiography are established non-invasive diagnostic tools for VSD. The recent advances in minimally invasive treatment options including periventricular approach and transcatheter techniques have improved patient outcomes, yet at the expense of higher residual rates. Careful patient selection for each technique and follow-up should be planned through multidisciplinary team meetings.

Preoperative Aspirin Management in Redo Tetralogy of Fallot Population: Single Centre Experience

Purpose: Redo operations and preoperative antiplatelet/anticoagulant therapy can significantly increase surgical risk in congenital heart surgery. This is a retrospective study on the impact of preoperative aspirin therapy on the outcome of Tetralogy of Redo Fallot patients undergoing right ventricle outflow tract (RVOT) conduit implantation. Methods: Ten-years retrospective analysis of medical records was carried out. A total of 72 patients were divided into two groups: “Daily-on-ASA” group on daily therapy with aspirin (ASA) until 5 days from surgery and “No-Home-ASA” without it. Propensity match analysis was done in order to standardize the populations. Intraoperative and postoperative lengths were compared as well as the need for inotropic support. In addition, differences in blood transfusions and need for Fresh frozen plasma (FFP)/platelets (PLT) were analysed. Findings: Intraoperative lengths were similar between the groups. Not statistically significative differences about postoperative time to extubation (p = 0.34), ICU Stay (p = 0.31) or in-hospital stay (p = 0.36) were found. Drain loss was higher in the “Daily-on-ASA” group (407.9 ± 96.7 mL vs. 349.5 ± 84.3 mL; p = 0.03) as well as blood transfusions (372.7 ± 255.1 mL vs. 220.1 ± 130.3 mL, p = 0.02) and PLT/FFP need (217.7 ± 132.1 mL vs. 118.7 ± 147.1 mL, p = 0.01). No differences were found in postoperative complications or re-explorations for bleeding. Implications: We found no advantages in surgical times and hospital stay comparing redo patients who stopped aspirin versus those that didn’t take it in the last 6 months. However, our results suggest that redo patients undergoing RVOT conduit implantation who take daily aspirin are at higher risk of bleeding even if it is stopped 5 days before surgery.