Foetal therapy: what works? Closed interatrial septum

Current Understanding of Indications, Technical Aspects and Outcomes of Fetal Cardiac Interventions

With the improvement in the detection of congenital heart disease in fetal life, fetal cardiac interventions are pushing the envelope in hopes of either altering the natural history of disease or improving survival in certain high-risk lesions. These interventions include fetal aortic valvuloplasty for evolving hypoplastic left heart syndrome, fetal atrial septoplasty with or without atrial septal stenting for hypoplastic left heart syndrome and variants with intact or severely restrictive atrial septum, and fetal pulmonary valvuloplasty for severe pulmonary stenosis or pulmonary atresia with intact ventricular septum. This review discusses their indications, technical aspects, and outcomes based on available literature.

Fetal cardiac intervention in hypoplastic left heart syndrome with intact or restrictive atrial septum, systematic review, and meta-analysis

To investigate outcomes of fetuses with hypoplastic left heart syndrome (HLHS) with an intact or restrictive atrial septum (I/RAS) managed expectantly or with fetal atrial septal intervention (FASI PubMed, Scopus, and Web of Science were searched systematically from inception until April 2023. Outcomes were classified by those who had FASI and those who had expectant management (EM). To estimate the overall proportion of each endpoint, a meta-analysis of proportions was employed using a random-effects model. Heterogeneity was assessed using the I2 value. Thirty-two studies reporting on 746 fetuses with HLHS and I/RAS met our inclusion criteria. Eleven studies (123 fetuses) were in the FASI group and 21 studies (623 fetuses) were in the EM group. Among the 123 FASI cases, 107 (87%) were reported to be technically successful. The mean gestational age (GA) at diagnosis was comparable between the groups (26.2 weeks FASI vs. 24.4 weeks EM group). The mean GA at FASI was 30.4 weeks (95% CI 28.5, 32.5). The mean GA at delivery was also comparable (37.7 weeks FASI vs. 38.1 weeks EM group). Neonatal outcomes, including live birth, neonatal death, and survival to hospital discharge pooled proportions, were also comparable between groups (live birth: 92% (95% CI 64, 99) FASI versus 93% (95% CI 79, 98) in EM, neonatal death: 32% (95% CI 11, 65) FASI versus 30% (95% CI 21, 41) EM, survival to hospital discharge: 37% (95% CI 25, 52) FASI versus 52% (95% CI 42, 61) EM). Age at neonatal death was higher in the FASI group (mean: 17 days FASI vs. 7.2 days EM group). There was a lower rate of postnatal atrial restrictive septum in the FASI group 38% (95% CI 17, 63) compared to the EM group 88% (95% CI 57, 98). Our review shows variations across centers in the selection criteria and techniques used for FASI. Although survival including livebirth, neonatal death, and survival to hospital discharge did not differ between groups, the procedure may translate into a less restrictive septum at birth. Future multicenter studies are needed to better identify the subset of cases that might have improved outcomes, use standardized definitions, unified techniques, utilize core outcome set, and assess long-term benefits.

Novel Insights into the Etiology, Genetics, and Embryology of Hypoplastic Left Heart Syndrome

Hypoplastic left heart syndrome (HLHS) is a relatively rare severe congenital heart defect (CHD) closely linked to other left ventricular outflow tract (LVOT) lesions including bicuspid aortic valve (BAV), one of the most common heart defects. While HLHS, BAV, and other LVOT lesions have a strong genetic underpinning, their genetic etiology remains poorly understood. Findings from a large-scale mouse mutagenesis screen showed HLHS has a multigenic etiology and is genetically heterogenous, explaining difficulties in identifying the genetic causes of HLHS. In Ohia mice, HLHS shows incomplete penetrance. Some mice exhibited small LV with normal aorta, and others a normal LV with hypoplastic aorta, indicating the LV hypoplasia is not hemodynamically driven. In Ohia mutants, HLHS was found to have a digenic modular construction, with mutation in a chromatin modifier causing the small LV phenotype and mutation in Pcdha9 causing the aorta/aortic valve hypoplasia. The Pcdha9 mutation alone can cause BAV, and in the human genome two common deletion copy number variants spanning PCDHA7-10 are associated with BAV. Hence the digenic etiology of HLHS can account for the close association of HLHS, a rare CHD, with BAV, one of the most common CHD. Functional analysis of Ohia HLHS heart tissue showed severe mitochondrial dysfunction in the small LV, while the normal size RV is also affected but milder, suggesting possible role in vulnerability of surgically palliated HLHS patients to heart failure. These findings suggest insights into the genetics of HLHS may yield new therapies for improving outcome for patients with HLHS.

A potentially curative fetal intervention for hypoplastic left heart syndrome

Hypoplastic left heart syndrome (HLHS) encapsulates a spectrum of complex congenital cardiovascular malformations involving varying degrees of underdevelopment of the left-sided heart structures. However, despite improved survival rates since the introduction of staged surgical reconstruction, treatment options for HLHS remain palliative rather than curative. A major limiting factor in the development of definitive curative therapy for HLHS is an incomplete understanding of its pathogenesis. Currently, the aetiology HLHS is best conceptualised by the 'flow theory' of cardiogenesis, which states that normal cardiac development is reliant on the interrelationship of normal flow patterns of blood through the developing heart, and appropriate growth of the cardiac valves and myocardium. Thus, congenital cardiac malformations, such as HLHS, are thought to arise when these two processes are incorrectly coupled in utero. The rationale for the hypothesis proposed herein rests upon the flow theory of cardiogenesis. Morphological studies of HLHS indicate that, although underdeveloped, all left-sided cardiac structures are present and anatomically correct. Further, of the various structural abnormalities that can occur within the spectrum of HLHS, the presence of a ventricular septal defect (VSD) is rare. The rarity of a VSD within the morphological spectrum of HLHS suggests the syndrome may not develop in the presence of a functionally significant VSD. Presumably, the presence of a functional VSD establishes a communication between the two ventricles during cardiac development, and preserves the normal pressure-flow-dependent growth of the left ventricular (LV) myocardium, despite inflow/outflow valve defects. It is proposed that surgical creation of a VSD in utero will 'rescue' the LV of hearts with left-sided valvular deformities that render them susceptible to the development of HLHS later in gestation. In evaluating this hypothesis, potential techniques for surgical creation of a VSD in utero are offered. These techniques are based on already established catheter-based in utero interventions, and conventional postnatal percutaneous procedures for VSD creation. Further discussion is also offered on techniques to avoid, and manage, potential complications (i.e. conduction system damage) of the proposed technique(s). Finally, if VSD creation in utero is indeed practically feasible, and successfully establishes the hypothesised hemodynamic and myocardial growth normalisation within the abnormally developing LV, the clinical implications are profound. This procedure may hold a potential cure for almost every sub-type of HLHS.

Dynamics in prevalence of Down syndrome in children with congenital heart disease

We assessed the dynamics in the prevalence of children with congenital heart disease (CHD) and Down syndrome in Germany with regard to phenotype, severity, and gender. Data from patients with CHD and Down syndrome born between 1980 and 2014 were analyzed, who are registered with the German National Register for Congenital Heart Defects. One thousand six hundred eighteen CHD patients with Down syndrome were identified. The prevalence of children born with both Down syndrome and CHD was constant from 2005 to 2009 but increased from 2010 to 2014. Regarding CHD groups, complex and simple lesions have become more equal since 2005. The number of simple lesions with shunt has a peak prevalence in the period of 2010-2014. Atrioventricular septal defect was the most common CHD phenotype, but temporal changes were found within the group of CHD phenotypes over the observation period.

CONCLUSION

Our findings suggest a growing number of CHD and Down syndrome, which may be the result of improved medical management and progress in educational, social, and financial support. This development is noteworthy as it adds new aspects to present discussions in the media and political settings. What is known: • Congenital heart disease is regarded to be the most important clinical phenomenon in children with Down syndrome, due to its significant impact on morbidity and mortality. • New developments in prenatal diagnostic and therapy management of congenital heart disease continue to influence the number of patients diagnosed with congenital heart disease and Down syndrome. What is New: • This study provides essential data giving the first overview of the dynamics in the prevalence of congenital heart disease and Down syndrome over an extended length of time up to 2015 in a large patient cohort, taking recent developments into account. • Our data suggest a growing prevalence of congenital heart disease and Down syndrome, which may be the result of improved medical management for Down syndrome patients and progress in educational, social, and financial support for their families; this development is noteworthy as it adds new aspects to the present discussion in the media and political settings.

Percutaneous Fetal Cardiac Catheterization Technique for Stenting the Foramen Ovale in a Midgestation Lamb Model

Background—

Intact or highly restricted intra-atrial septum can be reliably diagnosed in the human fetus as early as 22 to 24 weeks of gestation. Fetal interventions targeting the atrial septum have used a direct approach through the atrial wall. Here, we report stenting of the foramen ovale with a large, open-cell stent via percutaneous access through the fetal hepatic vein in a sheep model.

Methods and Results—

In 5 fetal sheep of 109 to 111 days of gestation (term, 147 days), the fetal hepatic vein was punctured percutaneously under ultrasound guidance and a 13.3-cm 14-gauge intravenous catheter was inserted. After catheterization of the inferior vena cava, right atrium, foramen ovale, and left atrium with a guidewire and 1.8F to 2.6F tapered catheter, a self-expandable, 8×12-mm flexible open-cell stent was positioned in an unrestricted foramen ovale. Flow and fetal well-being were documented for 45 minutes after the procedure. Access to the left atrium was achieved in all 5 animals and all survived. In 4 animals, the stent was successfully positioned in the foramen ovale. One fetus was born at term and euthanized on day 3: postmortem examination confirmed the patency of the stent. The other 3 fetuses were well after being monitored by ultrasound for 45 minutes. In 1 animal, the stent dislodged immediately after release obstructing the mitral valve. This fetus developed ascites and was euthanized after 4 days.

Conclusions—

It is feasible to safely advance a large diameter, self-expandable, open-cell design stent into the fetal atrial septum via a percutaneous access route through the fetal hepatic vein.