Assessment of left ventricular endocardial fibroelastosis in fetuses with aortic stenosis and evolving hypoplastic left heart syndrome

Two-dimensional speckle tracking echocardiography in fetuses with critical aortic stenosis before and after fetal aortic valvuloplasty

BACKGROUND

Critical aortic stenosis (AS) in fetuses may progress to hypoplastic left heart syndrome (HLHS) with need for postnatal single ventricular (SV) palliation. Fetal aortic valvuloplasty (FAV) is performed to achieve postnatal biventricular (BV) circulation. However, the impact of FAV on fetal myocardial function is difficult to measure. Prediction of postnatal circulatory status and, therefore, counseling is challenging.

METHODS

Retrospective study of fetuses with critical AS who underwent FAV. Global Longitudinal Peak Systolic Strain (GLPSS) of the left ventricle (LV) and right ventricle (RV) were retrospectively analyzed before and after intervention. Fisher's Exact Test and Mann-Whitney-U Test were used for univariant statistical analysis.

RESULTS

23 fetuses with critical AS were included. After intervention fetuses demonstrated more negative LV-GLPSS mean values post- vs. pre-intervention (- 5.36% vs. - 1.57%; p < 0.05). RV-GLPSS was decreased in all fetuses, there was no peri-interventional change. 20 fetuses were born alive. Postnatally, 10 had BV and 10 SV circulation. Improved post-interventional LV-GLPSS strain values correlated with BV outcome (p < 0.05). Pre-interventional continuous LV-GLPSS values correlated with postnatal SV vs. BV outcome (p < 0.05).

CONCLUSION

In some fetuses, LV myocardial function assessed by speckle tracking echocardiography (STE) improves after FAV. Improved post-interventional LV-GLPSS correlates with biventricular postnatal outcome. Furthermore, pre-interventional LV- and RV-GLPSS correlate with postnatal outcome. Further studies are needed to asses, if pre-interventional STE parameters might predict which fetuses will benefit from FAV with postnatal BV circulation.

Endocardial Fibroelastosis: A Comprehensive Review

Endocardial fibroelastosis emerged as a challenging clinical phenomenon in the 1940s. It is characterized by an atypical proliferation of fibrous and elastic tissue within the heart and is primarily observed in childhood, occasionally displaying familial inheritance. While the precise cause remains elusive, various factors, including genetic, infectious, metabolic, autoimmune, oncologic, and medication-related influences, appear to play a role in its pathogenesis. The coexistence of endocardial fibroelastosis with multiple cardiac structural abnormalities manifests in symptoms of congestive heart failure and rhythm abnormalities. Despite its challenging diagnosis, various findings from ECG and imaging have proven beneficial in further evaluation of this condition. Finally, the treatment approach to endocardial fibroelastosis became complex due to addressing its concurrent cardiac abnormalities. Strategies for managing and preventing this condition are still under investigation. In this review, we intend to highlight the existing knowledge and illuminate future considerations regarding the etiology, diagnosis, and management of this disease.

Endocardial Fibroelastosis Resection: When it Works and When it Does Not

Endocardial fibroelastosis (EFE) is a thickening of the endocardial layer by accumulation of collagen and elastic fibers. Endothelial to mesenchymal transformation is proposed to be the underlying mechanism of formation. Although EFE can occur in both right and left ventricles, this article will focus on management of left ventricular EFE. Through its fibrous, nonelastic manifestation EFE restricts the myocardium leading to diastolic and systolic ventricular dysfunction and prevents ventricular growth in neonates and infants. The presence of EFE may be a marker for underlying myocardial fibrosis as well. The extent of EFE within the left ventricular cavity can be variable ranging from patchy to confluent distribution. Similarly the depth of penetration and degree of infiltration into myocardium can be variable. The management of EFE is controversial, although resection of EFE has been reported as part of the staged ventricular recruitment therapy. Following resection, EFE recurs and infiltrates the myocardium after primary resection. Herein we review the current experience with EFE resection.

Endocardial fibroelastosis in infants and young children: a state-of-the-art review

Endocardial fibroelastosis (EFE) is a rare cardiac condition characterized by excessive endocardial thickening secondary to fibroelastic tissues that commonly present in infants and young children. Most of endocardial fibroelastosis cases are secondary forms, which occur in conjunction with other cardiac diseases. Endocardial fibroelastosis has been associated with poor prognosis and outcomes. In light of recent advancements in understanding pathophysiology, several new data have revealed compelling evidence that abnormal endothelial-to-mesenchymal transition is the root cause of endocardial fibroelastosis. This article aims to review the recent development in pathophysiology, diagnostic workup, and management, and to discuss possible differential diagnoses.

Myocardial Biomechanics and the Consequent Differentially Expressed Genes of the Left Atrial Ligation Chick Embryonic Model of Hypoplastic Left Heart Syndrome

Left atrial ligation (LAL) of the chick embryonic heart is a model of the hypoplastic left heart syndrome (HLHS) where a purely mechanical intervention without genetic or pharmacological manipulation is employed to initiate cardiac malformation. It is thus a key model for understanding the biomechanical origins of HLHS. However, its myocardial mechanics and subsequent gene expressions are not well-understood. We performed finite element (FE) modeling and single-cell RNA sequencing to address this. 4D high-frequency ultrasound imaging of chick embryonic hearts at HH25 (ED 4.5) were obtained for both LAL and control. Motion tracking was performed to quantify strains. Image-based FE modeling was conducted, using the direction of the smallest strain eigenvector as the orientations of contractions, the Guccione active tension model and a Fung-type transversely isotropic passive stiffness model that was determined via micro-pipette aspiration. Single-cell RNA sequencing of left ventricle (LV) heart tissues was performed for normal and LAL embryos at HH30 (ED 6.5) and differentially expressed genes (DEG) were identified.After LAL, LV thickness increased by 33%, strains in the myofiber direction increased by 42%, while stresses in the myofiber direction decreased by 50%. These were likely related to the reduction in ventricular preload and underloading of the LV due to LAL. RNA-seq data revealed potentially related DEG in myocytes, including mechano-sensing genes (Cadherins, NOTCH1, etc.), myosin contractility genes (MLCK, MLCP, etc.), calcium signaling genes (PI3K, PMCA, etc.), and genes related to fibrosis and fibroelastosis (TGF-β, BMP, etc.). We elucidated the changes to the myocardial biomechanics brought by LAL and the corresponding changes to myocyte gene expressions. These data may be useful in identifying the mechanobiological pathways of HLHS.

Prenatal Diagnosis of Fetal Heart Failure

Fetal heart failure (FHF) is a condition of inability of the fetal heart to deliver adequate blood flow for tissue perfusion in various organs, especially the brain, heart, liver and kidneys. FHF is associated with inadequate cardiac output, which is commonly encountered as the final outcome of several disorders and may lead to intrauterine fetal death or severe morbidity. Fetal echocardiography plays an important role in diagnosis of FHF as well as of the underlying causes. The main findings supporting the diagnosis of FHF include various signs of cardiac dysfunction, such as cardiomegaly, poor contractility, low cardiac output, increased central venous pressures, hydropic signs, and the findings of specific underlying disorders. This review will present a summary of the pathophysiology of fetal cardiac failure and practical points in fetal echocardiography for diagnosis of FHF, focusing on essential diagnostic techniques used in daily practice for evaluation of fetal cardiac function, such as myocardial performance index, arterial and systemic venous Doppler waveforms, shortening fraction, and cardiovascular profile score (CVPs), a combination of five echocardiographic markers indicative of fetal cardiovascular health. The common causes of FHF are reviewed and updated in detail, including fetal dysrhythmia, fetal anemia (e.g., alpha-thalassemia, parvovirus B19 infection, and twin anemia-polycythemia sequence), non-anemic volume load (e.g., twin-to-twin transfusion, arteriovenous malformations, and sacrococcygeal teratoma, etc.), increased afterload (intrauterine growth restriction and outflow tract obstruction, such as critical aortic stenosis), intrinsic myocardial disease (cardiomyopathies), congenital heart defects (Ebstein anomaly, hypoplastic heart, pulmonary stenosis with intact interventricular septum, etc.) and external cardiac compression. Understanding the pathophysiology and clinical courses of various etiologies of FHF can help physicians make prenatal diagnoses and serve as a guide for counseling, surveillance and management.

Fluid Mechanical Effects of Fetal Aortic Valvuloplasty for Cases of Critical Aortic Stenosis with Evolving Hypoplastic Left Heart Syndrome

Fetuses with critical aortic stenosis (FAS) are at high risk of progression to HLHS by the time of birth (and are thus termed "evolving HLHS"). An in-utero catheter-based intervention, fetal aortic valvuloplasty (FAV), has shown promise as an intervention strategy to circumvent the progression, but its impact on the heart's biomechanics is not well understood. We performed patient-specific computational fluid dynamic (CFD) simulations based on 4D fetal echocardiography to assess the changes in the fluid mechanical environment in the FAS left ventricle (LV) directly before and 2 days after FAV. Echocardiograms of five FAS cases with technically successful FAV were retrospectively analysed. FAS compromised LV stroke volume and ejection fraction, but FAV rescued it significantly. Calculations to match simulations to clinical measurements showed that FAV approximately doubled aortic valve orifice area, but it remained much smaller than in healthy hearts. Diseased LVs had mildly stenotic mitral valves, which generated fast and narrow diastolic mitral inflow jet and vortex rings that remained unresolved directly after FAV. FAV further caused aortic valve damage and high-velocity regurgitation. The high-velocity aortic regurgitation jet and vortex ring caused a chaotic flow field upon impinging the apex, which drastically exacerbated the already high energy losses and poor flow energy efficiency of FAS LVs. Two days after the procedure, FAV did not alter wall shear stress (WSS) spatial patterns of diseased LV but elevated WSS magnitudes, and the poor blood turnover in pre-FAV LVs did not significantly improve directly after FAV. FAV improved FAS LV's flow function, but it also led to highly chaotic flow patterns and excessively high energy losses due to the introduction of aortic regurgitation directly after the intervention. Further studies analysing the effects several weeks after FAV are needed to understand the effects of such biomechanics on morphological development.

Mechanical strain triggers endothelial-to-mesenchymal transition of the endocardium in the immature heart

BACKGROUND

Endothelial-to-mesenchymal-transition (EndMT) plays a major role in cardiac fibrosis, including endocardial fibroelastosis but the stimuli are still unknown. We developed an endothelial cell (EC) culture and a whole heart model to test whether mechanical strain triggers TGF-β-mediated EndMT.

METHODS

Isolated ECs were exposed to 10% uniaxial static stretch for 8 h (stretch) and TGF-β-mediated EndMT was determined using the TGF-β-inhibitor SB431542 (stretch + TGF-β-inhibitor), BMP-7 (stretch + BMP-7) or losartan (stretch + losartan), and isolated mature and immature rats were exposed to stretch through a weight on the apex of the left ventricle. Immunohistochemical staining for double-staining with endothelial markers (VE-cadherin, PECAM1) and mesenchymal markers (αSMA) or transcription factors (SLUG/SNAIL) positive nuclei was indicative of EndMT.

RESULTS

Stretch-induced EndMT in ECs expressed as double-stained ECs/total ECs (cells: 46 ± 13%; heart: 15.9 ± 2%) compared to controls (cells: 7 ± 2%; heart: 3.1 ± 0.1; p < 0.05), but only immature hearts showed endocardial EndMT. Inhibition of TGF-β decreased the number of double-stained cells significantly, comparable to controls (cells/heart: control: 7 ± 2%/3.1 ± 0.1%, stretch: 46 ± 13%/15 ± 2%, stretch + BMP-7: 7 ± 2%/2.9 ± 0.1%, stretch + TGF-β-inhibitor (heart only): 5.2 ± 1.3%, stretch + losartan (heart only): 0.89 ± 0.1%; p < 0.001 versus stretch).

CONCLUSIONS

Endocardial EndMT is an age-dependent consequence of increased strain triggered by TGF- β activation. Local inhibition through either rebalancing TGF-β/BMP or with losartan was effective to block EndMT.

IMPACT

Mechanical strain imposed on the immature LV induces endocardial fibroelastosis (EFE) formation through TGF-β-mediated activation of endothelial-to-mesenchymal transition (EndMT) in endocardial endothelial cells but has no effect in mature hearts. Local inhibition through either rebalancing the TGF-β/BMP pathway or with losartan blocks EndMT. Inhibition of endocardial EndMT with clinically applicable treatments may lead to a better outcome for congenital heart defects associated with EFE.

[Fetal aortic valvuloplasty in critical aortic stenosis: indication, technique and postnatal outcomes]

Aortic stenosis is a complex heart disease that involves the aortic valve and the left ventricle. Impairment of the left ventricle, abnormalities in its size, systolic and diastolic function determine the postnatal outcomes in the same way as the aortic valve. In the most severe forms, the left ventricle cannot provide systemic circulation at birth and the physiology is that of hypoplastic left heart syndrome. Fetal aortic valvuloplasty has been developed in the 90s to prevent in utero progression of aortic stenosis to hypoplastic left heart syndrome. In the present article, the most recently reported data about indications, procedure details and postnatal outcomes were reviewed.

Fluid Mechanics of Fetal Left Ventricle During Aortic Stenosis with Evolving Hypoplastic Left Heart Syndrome

In cases of fetal aortic stenosis and evolving Hypoplastic Left Heart Syndrome (feHLHS), aortic stenosis is associated with specific abnormalities such as retrograde or bidirectional systolic transverse arch flow. Many cases progressed to hypoplastic left heart syndrome (HLHS) malformation at birth, but fetal aortic valvuloplasty can prevent the progression in many cases. Since both disease and intervention involve drastic changes to the biomechanical environment, in-vivo biomechanics likely play a role in inducing and preventing disease progression. However, the fluid mechanics of feHLHS is not well-characterized. Here, we conduct patient-specific echocardiography-based flow simulations of normal and feHLHS left ventricles (LV), to understand the essential fluid dynamics distinction between the two cohorts. We found high variability across feHLHS cases, but also the following unifying features. Firstly, feHLHS diastole mitral inflow was in the form of a narrowed and fast jet that impinged onto the apical region, rather than a wide and gentle inflow in normal LVs. This was likely due to a malformed mitral valve with impaired opening dynamics. This altered inflow caused elevated vorticity dynamics and wall shear stresses (WSS) and reduced oscillatory shear index at the apical zone rather than mid-ventricle. Secondly, feHLHS LV also featured elevated systolic and diastolic energy losses, intraventricular pressure gradients, and vortex formation numbers, suggesting energy inefficiency of flow and additional burden on the LV. Thirdly, feHLHS LV had poor blood turnover, suggesting a hypoxic environment, which could be associated with endocardial fibroelastosis that is often observed in these patients.

Hypoplastic Left Heart Syndrome: Is There a Role for Fetal Therapy?

During fetal life some cardiac defects may lead to diminished left heart growth and to the evolution of a form of hypoplastic left heart syndrome (HLHS). In fetuses with an established HLHS, severe restriction or premature closure of the atrial septum leads to left atrial hypertension and remodeling of the pulmonary vasculature, severely worsening an already poor prognosis. Fetal therapy, including invasive fetal cardiac interventions and non-invasive maternal hyperoxygenation, have been introduced to prevent a possible progression of left heart hypoplasia, improve postnatal outcome, or secure fetal survival. The aim of this review is to cover patient selection and possible hemodynamic effects of fetal cardiac procedures and maternal hyperoxygenation in fetuses with an evolving or established hypoplastic left heart syndrome.

Abnormal Flow Conditions Promote Endocardial Fibroelastosis Via Endothelial-to-Mesenchymal Transition, Which Is Responsive to Losartan Treatment

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EFE is a congenital cardiac pathology contributing to increased morbidity and mortality. The pathologic triggers of EFE remain to be characterized.

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To determine whether abnormal flow promotes EFE development, we used in vivo neonatal rodent surgical models and an in vitro model using human primary endocardial cells

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We established novel surgical model with flow profiles seen in patients that develop EFE. Static and turbulent flow conditions promoted EFE development in neonatal rodent hearts.

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Losartan treatment is shown to significantly ameliorate EFE progression and decreases mRNA and protein expression of EndoMT markers in neonatal rodent hearts.

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RNAseq analysis of human endocardial cells subjected to different flow conditions show that normal flow suppresses gene expression critical for mesenchymal differentiation and Notch signaling.

Endocardial fibroelastosis (EFE) is defined by fibrotic tissue on the endocardium and forms partly through aberrant endothelial-to-mesenchymal transition. However, the pathologic triggers are still unknown. In this study, we showed that abnormal flow induces EFE partly through endothelial-to-mesenchymal transition in a rodent model, and that losartan can abrogate EFE development. Furthermore, we translated our findings to human endocardial endothelial cells, and showed that laminar flow promotes the suppression of genes associated with mesenchymal differentiation. These findings emphasize the role of flow in promoting EFE in endocardial endothelial cells and provide a novel potential therapy to treat this highly morbid condition.

Deficient Myocardial Organization and Pathological Fibrosis in Fetal Aortic Stenosis-Association of Prenatal Ultrasound with Postmortem Histology

In fetal aortic stenosis (AS), it remains challenging to predict left ventricular development over the course of pregnancy. Myocardial organization, differentiation and fibrosis could be potential biomarkers relevant for biventricular outcome. We present four cases of fetal AS with varying degrees of severity and associate myocardial deformation on fetal ultrasound with postmortem histopathological characteristics. During routine fetal echocardiography, speckle tracking recordings of the cardiac four-chamber view were performed to assess myocardial strain as parameter for myocardial deformation. After pregnancy termination, postmortem cardiac specimens were examined using immunohistochemical labeling (IHC) of key markers for myocardial organization, differentiation and fibrosis and compared to normal fetal hearts. Two cases with critical AS presented extremely decreased left ventricular (LV) strain on fetal ultrasound. IHC showed overt endocardial fibro-elastosis, which correlated with pathological fibrosis patterns in the myocardium and extremely disturbed cardiomyocyte organization. The LV in severe AS showed mildly reduced myocardial strain and less severe disorganization of the cardiomyocytes. In conclusion, the degree of reduction in myocardial deformation corresponded with high extent to the amount of pathological fibrosis patterns and cardiomyocyte disorganization. Myocardial deformation on fetal ultrasound seems to hold promise as a potential biomarker for left ventricular structural damage in AS.

Endocardial fibroelastosis and dilated cardiomyopathy - the past and future of the interface between histology and genetics

Endocardial fibroelastosis (EFE) signifies the pathological process by which collagen and elastin are focally or diffuse deposited in the endocardium of the left ventricle. The new layer causes left ventricular dysfunction sometimes with fulminant progression to heart failure. EFE is a major component in many congenital heart abnormalities but can also occur in the absence of heart malformations, either as a primary process or in response to cardiac injury. The endothelial–mesenchymal transition (EndMT) abnormalities seem to be main pathogenic factor in fibroelastosis development. The “gold standard” for diagnosis of primary EFE (pEFE) is the histological examination. Additionally, genetic studies may help to establish the natural course of the disease and to communicate prophylactic measures to family members of the affected child. Moreover, in the newborn, EFE takes the form of dilated cardiomyopathy (DCM) with unfavorable evolution. The proper management should be established considering negative prognostic factors, involving early transplantation, drug therapy and long-term follow-up.

Fluid mechanics of the left atrial ligation chick embryonic model of hypoplastic left heart syndrome

Left atrial ligation (LAL) of the chick embryonic heart at HH21 is a model of the hypoplastic left heart syndrome (HLHS) disease, demonstrating morphological and hemodynamic features similar to human HLHS cases. Since it relies on mechanical intervention without genetic or pharmacological manipulations, it is a good model for understanding the biomechanics origins of such HLHS malformations. To date, however, the fluid mechanical environment of this model is poorly understood. In the current study, we performed 4D ultrasound imaging of LAL and normal chick embryonic hearts and 4D cardiac flow simulations to help shed light on the mechanical environment that may lead to the HLHS morphology. Results showed that the HH25 LAL atrial function was compromised, and velocities in the ventricle were reduced. The HH25 LAL ventricles developed a more triangular shape with a sharper apex, and in some cases, the atrioventricular junction shifted medially. These changes led to more sluggish flow near the ventricular free wall and apex, where more fluid particles moved in an oscillatory manner with the motion of the ventricular wall, while slowly being washed out, resulting in lower wall shear stresses and higher oscillatory indices. Consequent to these flow conditions, at HH28, even before septation is complete, the left ventricle was found to be hypoplastic while the right ventricle was found to be larger in compensation. Our results suggest that the low and oscillatory flow near the left side of the heart may play a role in causing the HLHS morphology in the LAL model.

Biomechanics of Human Fetal Hearts with Critical Aortic Stenosis

Critical aortic stenosis (AS) of the fetal heart causes a drastic change in the cardiac biomechanical environment. Consequently, a substantial proportion of such cases will lead to a single-ventricular birth outcome. However, the biomechanics of the disease is not well understood. To address this, we performed Finite Element (FE) modelling of the healthy fetal left ventricle (LV) based on patient-specific 4D ultrasound imaging, and simulated various disease features observed in clinical fetal AS to understand their biomechanical impact. These features included aortic stenosis, mitral regurgitation (MR) and LV hypertrophy, reduced contractility, and increased myocardial stiffness. AS was found to elevate LV pressures and myocardial stresses, and depending on severity, can drastically decrease stroke volume and myocardial strains. These effects are moderated by MR. AS alone did not lead to MR velocities above 3 m/s unless LV hypertrophy was included, suggesting that hypertrophy may be involved in clinical cases with high MR velocities. LV hypertrophy substantially elevated LV pressure, valve flow velocities and stroke volume, while reducing LV contractility resulted in diminished LV pressure, stroke volume and wall strains. Typical extent of hypertrophy during fetal AS in the clinic, however, led to excessive LV pressure and valve velocity in the FE model, suggesting that reduced contractility is typically associated with hypertrophy. Increased LV passive stiffness, which might represent fibroelastosis, was found to have minimal impact on LV pressures, stroke volume, and wall strain. This suggested that fibroelastosis could be a by-product of the disease progression and does not significantly impede cardiac function. Our study demonstrates that FE modelling is a valuable tool for elucidating the biomechanics of congenital heart disease and can calculate parameters which are difficult to measure, such as intraventricular pressure and myocardial stresses.

Fetal aortic valvuloplasty: first report of two cases from Saudi Arabia

Background

Fetal aortic stenosis may progress to hypoplastic left heart syndrome (HLHS), which carries a poor prognosis. We report two infants with fetal aortic stenosis successfully treated with fetal aortic valvuloplasty (FAV) using balloon dilatation.

Case presentation

Of five fetuses with aortic stenosis fulfilling the FAV criteria of severe aortic stenosis with a left ventricular length Z-score of ≥ − 2, retrograde flow in the transverse aortic arch, left-to-right flow across the foramen ovale, monophasic mitral inflow, and significant left ventricular dysfunction, we obtained permission for FAV in two fetuses. FAV was performed successfully under echocardiographic guidance using balloon dilatation. Both fetuses survived to birth. During FAV, mild pericardial effusion developed when introducing the stylet needle in the second fetus, and this resolved within 48 h. No intraprocedural complications occurred in the first patient, and no maternal complications occurred. The first infant underwent the Ross procedure after birth and is currently 7 years old and doing well. The second patient underwent aortic and mitral valve repair with endocardial fibroelastosis resection approximately 2 weeks after birth, which temporarily addressed the mitral valve stenosis; high doses of inotropes were subsequently required. The infant died of sepsis at 2 months of age.

Conclusion

FAV using balloon dilatation to treat fetal aortic stenosis was successful in our two patients, with subsequent neonatal biventricular repair resulting in long-term survival in one patient and death secondary to sepsis in the second patient.

Reassessing endothelial-to-mesenchymal transition in cardiovascular diseases

Endothelial cells and mesenchymal cells are two different cell types with distinct morphologies, phenotypes, functions, and gene profiles. Accumulating evidence, notably from lineage-tracing studies, indicates that the two cell types convert into each other during cardiovascular development and pathogenesis. During heart development, endothelial cells transdifferentiate into mesenchymal cells in the endocardial cushion through endothelial-to-mesenchymal transition (EndoMT), a process that is critical for the formation of cardiac valves. Studies have also reported that EndoMT contributes to the development of various cardiovascular diseases, including myocardial infarction, cardiac fibrosis, valve calcification, endocardial elastofibrosis, atherosclerosis, and pulmonary arterial hypertension. Conversely, cardiac fibroblasts can transdifferentiate into endothelial cells and contribute to neovascularization after cardiac injury. However, progress in genetic lineage tracing has challenged the role of EndoMT, or its reversed programme, in the development of cardiovascular diseases. In this Review, we discuss the caveats of using genetic lineage-tracing technology to investigate cell-lineage conversion; we also reassess the role of EndoMT in cardiovascular development and diseases and elaborate on the molecular signals that orchestrate EndoMT in pathophysiological processes. Understanding the role and mechanisms of EndoMT in diseases will unravel the therapeutic potential of targeting this process and will provide a new paradigm for the development of regenerative medicine to treat cardiovascular diseases.

Cardiac function and dysfunction in the fetus

Evaluation of fetal cardiac function is one of the most important components of fetal echocardiography. Fetal cardiac dysfunction is closely linked to risk of intrauterine fetal demise, in many, but not all cases is indicative of worse postnatal prognosis and may prompt the use of medications or interventions to optimize outcomes. There may be implications for termination versus continuation of pregnancy, an indication for early delivery, a change in location and even mode of delivery. In extreme cases, fetal cardiac dysfunction may prompt prenatal or early neonatal listing for cardiac transplantation. There are several important differences between the fetal and postnatal circulatory physiology which affect echocardiographic assessment of cardiac dysfunction. In this review, we examine the echocardiographic findings according to their underlying pathophysiology with reference to common causes.

Improved technical success, postnatal outcome and refined predictors of outcome for fetal aortic valvuloplasty

OBJECTIVES

Fetal aortic valvuloplasty (FAV) may prevent progression of mid-gestation aortic stenosis to hypoplastic left heart syndrome (HLHS). The aim of this study was to evaluate whether technical success and biventricular (Biv) outcome after FAV have changed from an earlier (2000-2008) to a more recent (2009-2015) era and identify pre-FAV predictors of Biv outcome.

METHODS

We evaluated procedural and postnatal outcomes in 123 fetuses that underwent FAV for evolving HLHS at Boston Children's Hospital between 2000 and 2015. The primary outcome measure was circulation type (Biv vs single ventricle) at the time of neonatal hospital discharge. Classification and regression tree (CART) analysis was performed to construct a stratification algorithm to predict Biv circulation based on pre-FAV fetal variables.

RESULTS

The FAV procedure was technically successful in 101/123 (82%) fetuses, with a higher technical success rate in the more recent era than in the earlier one (49/52 (94%) vs 52/71 (73%); P = 0.003). In liveborn patients, the incidence of Biv outcome was higher in the recent than in the earlier era, both in the entire liveborn cohort (29/49 (59%) vs 16/62 (26%); P = 0.001) and in those in whom the procedure was technically successful (27/46 (59%) vs 15/47 (32%); P = 0.007). Independent predictors of Biv outcome were higher left ventricular (LV) pressure, larger ascending aorta, better LV diastolic function and higher LV long-axis Z-score. On CART analysis, fetuses with LV pressure > 47 mmHg and ascending aorta Z-score ≥ 0.57 had a 92% probability of Biv outcome (n = 24). Those with a lower LV pressure, or mitral dimension Z-score < 0.1 and mitral valve inflow time Z-score < -2 (n = 34) were unlikely to have Biv (probability of 9%). The remainder of the patients had an intermediate (∼40-60%) likelihood of Biv circulation.

CONCLUSIONS

The proportion of patients achieving Biv outcome after FAV has increased, probably owing to an improved technical success rate and modified selection criteria. Fetal factors, including LV pressure, size of the ascending aorta and diastolic function, are associated with likelihood of Biv circulation after FAV. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Fetal hemodynamic response to aortic valvuloplasty and postnatal outcome: a European multicenter study

OBJECTIVE

Fetal aortic stenosis may progress to hypoplastic left heart syndrome. Fetal valvuloplasty (FV) has been proposed to improve left heart hemodynamics and maintain biventricular (BV) circulation. The aim of this study was to assess FV efficacy by comparing survival and postnatal circulation between fetuses that underwent FV and those that did not.

METHODS

This was a retrospective multicenter study of fetuses with aortic stenosis that underwent FV between 2005 and 2012, compared with contemporaneously enrolled natural history (NH) cases sharing similar characteristics at presentation but not undergoing FV. Main outcome measures were overall survival, BV-circulation survival and survival after birth. Secondary outcomes were hemodynamic change and left heart growth. A propensity score model was created including 54/67 FV and 60/147 NH fetuses. Analyses were performed using logistic, Cox or linear regression models with inverse probability of treatment weighting (IPTW) restricted to fetuses with a propensity score of 0.14-0.9, to create a final cohort for analysis of 42 FV and 29 NH cases.

RESULTS

FV was technically successful in 59/67 fetuses at a median age of 26 (21-34) weeks. There were 7/72 (10%) procedure-related losses, and 22/53 (42%) FV babies were delivered at < 37 weeks. IPTW demonstrated improved survival of liveborn infants following FV (hazard ratio, 0.38; 95% CI, 0.23-0.64; P = 0.0001), after adjusting for circulation and postnatal surgical center. Similar proportions had BV circulation (36% for the FV cohort and 38% for the NH cohort) and survival was similar between final circulations. Successful FV cases showed improved hemodynamic response and less deterioration of left heart growth compared with NH cases (P ≤ 0.01).

CONCLUSIONS

We report improvements in fetal hemodynamics and preservation of left heart growth following successful FV compared with NH. While the proportion of those achieving a BV circulation outcome was similar in both cohorts, FV survivors showed improved survival independent of final circulation to 10 years' follow-up. However, FV is associated with a 10% procedure-related loss and increased prematurity compared with the NH cohort, and therefore the risk-to-benefit ratio remains uncertain. We recommend a carefully designed trial incorporating appropriate and integrated fetal and postnatal management strategies to account for center-specific practices, so that the benefits achieved by fetal therapy vs surgical strategy can be demonstrated clearly. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Fibroblasts in an endocardial fibroelastosis disease model mainly originate from mesenchymal derivatives of epicardium

Endocardial fibroelastosis (EFE) refers to the thickening of the ventricular endocardium as a result of de novo deposition of subendocardial fibrous tissue layers during neonatal heart development. The origin of EFE fibroblasts is proposed to be postnatal endocardial cells that undergo an aberrant endothelial-to-mesenchymal transition (EndMT). Genetic lineage tracing of endocardial cells with the inducible endocardial Cre line Npr3-CreER and the endothelial cell tracing line Cdh5-CreER on an EFE-like model did not reveal any contribution of neonatal endocardial cells to fibroblasts in the EFE-like tissues. Instead, lineage tracing of embryonic epicardium by Wt1-CreER suggested that epicardium-derived mesenchymal cells (MCs) served as the major source of EFE fibroblasts. By labeling MCs using Sox9-CreER, we confirmed that MCs of the embryonic heart expand and contribute to the majority of neonatal EFE fibroblasts. During this pathological process, TGFβ signaling, the key mediator of fibroblasts activation, was highly upregulated in the EFE-like tissues. Targeting TGFβ signaling by administration of its antagonist bone morphogenetic protein 7 effectively reduced fibroblast accumulation and tissue fibrosis in the EFE-like model. Our study provides genetic evidence that excessive fibroblasts in the EFE-like tissues mainly originate from the epicardium-derived MCs through epicardial to mesenchymal transition (EpiMT). These EpiMT-derived fibroblasts within the EFE-like tissues could serve as a potential therapeutic target.

Utility of Cardiovascular Magnetic Resonance-Derived Wave Intensity Analysis As a Marker of Ventricular Function in Children with Heart Failure and Normal Ejection Fraction

OBJECTIVE

This study sought to explore the diagnostic insight of cardiovascular magnetic resonance (CMR)-derived wave intensity analysis to better study systolic dysfunction in young patients with chronic diastolic dysfunction and preserved ejection fraction (EF), comparing it against other echocardiographic and CMR parameters.

BACKGROUND

Evaluating systolic and diastolic dysfunctions in children is challenging, and a gold standard method is currently lacking.

METHODS

Patients with presumed diastolic dysfunction [n = 18; nine aortic stenosis (AS), five hypertrophic, and four restrictive cardiomyopathies] were compared with age-matched control subjects (n = 18). All patients had no mitral or aortic incompetence, significant AS, or reduced systolic EF. E/A ratio, E/E' ratio, deceleration time, and isovolumetric contraction time were assessed on echocardiography, and indexed left atrial volume (LAVi), acceleration time (AT), ejection time (ET), and wave intensity analyses were calculated from CMR. The latter was performed on CMR phase-contrast flow sequences, defining a ratio of the peaks of the early systolic forward compression wave (FCW) and the end-systolic forward expansion wave (FEW).

RESULTS

Significant differences between patients and controls were seen in the E/E' ratio (8.7 ± 4.0 vs. 5.1 ± 1.3, p = 0.001) and FCW/FEW ratio (2.5 ± 1.6 vs. 7.2 ± 4.2 × 10^-5 m/s, p < 0.001), as well as-as expected-LAVi (80.7 ± 22.5 vs. 51.0 ± 10.9 mL/m², p < 0.001). In particular, patients exhibited a lower FCW (2.5 ± 1.6 vs. 7.2 ± 4.2 × 10^-5 m/s, p < 0.001) in the face of preserved EF (67 ± 11 vs. 69 ± 5%, p = 0.392), as well as longer isovolumetric contraction time (49 ± 7 vs. 34 ± 7 ms, p < 0.001) and ET/AT (0.35 ± 0.04 vs. 0.27 ± 0.04, p < 0.001).

CONCLUSION

This study shows that the wave intensity-derived ratio summarizing systolic and diastolic function could provide insight into ventricular function in children, on top of CMR and echocardiography, and it was here able to identify an element of ventricular dysfunction with preserved EF in a small group of young patients.

Hypoplastic left heart syndrome: a review

BACKGROUND

Hypoplastic left heart syndrome (HLHS) is an etiologically multifactorial congenital heart disease affecting one in 5,000 newborns. Thirty years ago there were no treatment options for this pathology and the natural course of the disease led to death, usually within the first weeks of life. Recently surgical palliative techniques have been developed allowing for a five-year survival in more than half the cases.

MATERIALS AND METHODS

We reviewed literature available on HLHS, specifically its anatomy, embryology and pathophysiology, and treatment. The Pubmed and ClinicalKey databases were searched using the key words hypoplastic left heart syndrome, foetal aortic valvuloplasty, foetal septoplasty, Norwood procedure, bidirectional Glenn procedure, Fontan procedure, hybrid procedure. The relevant literature was reviewed and included in the article. We reported a case from Children's Clinical University Hospital, Riga, to illustrate treatment tactics in Latvia.

RESULTS

There are three possible directions for therapy in newborns with HLHS: orthotopic heart transplantation, staged surgical palliation and palliative non-surgical treatment or comfort care. Another treatment mode - foetal therapy - has arisen. Staged palliation and full Fontan circulation is a temporary solution, however, the only means for survival until heart transplantation. Fifty to 70% of patients who have gone through all three stages of palliation live to the age of five years.

CONCLUSIONS

The superior mode of treatment is not yet clear and the management must be based on each individual case, the experience of each clinic, as well as the financial aspects and will of the patient's parents.

Approach an appropriate decision on fetus with endocardial fibroelastosis in collaboration with cardiovascular profile score: A case report

INTRODUCTION

Fetal endocardial fibroelastosis (EFE) is a kind of rare fetal cardiac malformation characterized by the diffuse thickening of the ventricular endocardium. The diagnosis of fetal EFE depends on the echocardiographic features which are still confused that how to make an appropriate pregnant decision due to the conflict between high prenatal mortality and acceptable prognosis once after birth. Here, we seriously built a 4-gradation recommendation system based on cardiovascular profile score (CVPS) to supply a prediction of clarified pregnant outcomes with EFE and provide a practical way to offer optimal medical consultation.

CLINICAL PROCEDURE

A suspected case of fetal EFE has been aware at 24th gestational week by fetal echocardiography. The CVPS of this affected fetus dropped to 6 out of 10 points, which indicated a severe heart condition along with the fetus and predicted an adverse fetal prognosis according to our recommendation system. After fully informed consent, the prospective parents determined to terminate pregnancy. Following the induced abortion, postmortem pathological findings confirmed the echocardiographic suspicion of EFE.

CONCLUSION

According to our experience and previous researches, we could reach a relative clear prediction of the outcomes of the EFE fetuses based on the CVPS of such suspected fetuses, which should lead to approach an appropriate pregnant decision for such fetuses.

Fetal interventions for congenital heart disease

PURPOSE OF REVIEW

This article discusses the rationale, patient selection, technical aspects, and outcomes of percutaneous, ultrasound-guided fetal cardiac intervention (FCI) for structural congenital heart disease.

RECENT FINDINGS

FCI is most commonly performed for three forms of congenital heart disease: severe aortic stenosis with evolving hypoplastic left heart syndrome (HLHS), pulmonary atresia with intact ventricular septum and evolving hypoplastic right heart syndrome, and HLHS with intact or highly restrictive atrial septum. For severe aortic stenosis and pulmonary atresia with intact ventricular septum, the goal of intervention is to alter the natural history such that a biventricular circulation may be achieved postnatally. A growing number of patients have achieved a biventricular circulation; however, patient selection and postnatal management strategy are essential for success. HLHS with intact or highly restrictive atrial septum is one of the most lethal forms of congenital heart disease, and the goal of FCI is to improve survival. Although the creation of an atrial communication in utero is technically feasible and may permit greater stability in the immediate postnatal period, significant improvements in survival have not yet been reported.

SUMMARY

FCI is an evolving form of treatment for congenital heart disease that holds promise for select patients. Critical evaluation of both short and long-term outcomes is warranted.

Assessment of Structural and Functional Abnormalities of the Myocardium and the Ascending Aorta in Fetus with Hypoplastic Left Heart Syndrome

Aims. To detect anatomical and intrinsic histopathological features of the ascending aorta and left ventricular (LV) myocardium and evaluate right ventricular (RV) function in fetuses with hypoplastic left heart syndrome (HLHS). Methods. Twenty-five fetuses diagnosed with HLHS were followed up in the antenatal and postpartum periods. 12 necropsy heart specimens were analyzed for morphological and histological changes. Results. Prenatal echocardiography and pathologic anatomy displayed the typical characteristics of HLHS as a severe underdevelopment of the LV in the form of mitral stenosis or atresia or as aortic atresia or stenosis, with a decreased ratio of aortic diameter to pulmonary artery diameter (median of 0.49 with a range of 0.24 to 0.69, p ≤ 0.001) and a higher ratio of RV diameter to LV diameter (median of 2.44 with a range of 1.33 to 6.25, p ≤ 0.001). The RV volume, stroke volume, and cardiac output in HLHS fetuses were increased compared with the gestational age-matched normal controls (p < 0.01). Histological changes in the 12 HLHS specimens included LV myocardial fibrosis, aortic elastic fragmentation, and fibrosis. Conclusions. In addition to severe anatomical deformity, distinct histological abnormalities in the LV myocardium and aortic wall were identified in the fetuses with HLHS. RV function damage may be potentially exists.

The myocardial and coronary histopathology and pathogenesis of hypoplastic left heart syndrome

Hypoplastic left heart syndrome has the greatest mortality rate among all CHDs and without palliation is uniformly fatal. Despite noble efforts, the aetiology of this syndrome is unknown and a cure remains elusive. The genetic and anatomic heterogeneity of hypoplastic left heart syndrome supports a rethinking of old hypotheses and warrants further investigation into the histological and vascular variations recognised with this syndrome. In an effort to elucidate the pathogenesis of hypoplastic left heart syndrome, this review will focus on its unique myocardial and coronary pathology as well as evaluate the association of hypoplastic left heart syndrome with the endocardial fibroelastosis reaction.

Left Ventricular Remodeling and Function in Children with Biventricular Circulation After Fetal Aortic Valvuloplasty

Fetal aortic valvuloplasty (FAV) has shown promise in averting the progression of fetal aortic stenosis to hypoplastic left-heart syndrome. Altered loading conditions due to valvar disease, intrinsic endomyocardial abnormalities, and procedures that alter endomyocardial mechanics may place patients with biventricular circulation (BiV) after FAV at risk of abnormal LV remodeling and function. Using the most recent echo data on BiV patients after technically successful FAV (n = 34), we evaluated LV remodeling pattern, risk factors for pathologic LV remodeling, and the association between LV remodeling pattern and LV function. Median age at follow-up was 4.7 years (range 1.0-12.5). Cardiac interventions were common. At latest follow-up, no patient had hypoplastic LV. Nineteen patients (55 %) had dilated LV, and five (16 %) patients had severely dilated LV. LV remodeling patterns were as follows: 12 (35 %) normal ventricle, 11 (32 %) mixed hypertrophy, 8 (24 %) eccentric hypertrophy or remodeling, and 3 (9 %) concentric hypertrophy. Univariate factors associated with pathologic LV remodeling were long-standing AR, ≥2 cardiac interventions, EFE resection, and aortic or mitral regurgitation ≥ moderate at most recent follow-up. In multivariate analysis, only long-standing AR fraction remained associated with pathologic remodeling. Pathologic LV remodeling was associated with depressed ejection fraction, lower septal E´, and higher E/E´. Pathologic LV remodeling, primarily eccentric or mixed hypertrophy, is common in BiV patients after FAV and is related to LV loading conditions imposed by valvar disease. Pathologic remodeling is associated with both systolic and diastolic dysfunction in this population.

A mouse model of endocardial fibroelastosis

BACKGROUND

Endocardial fibroelastosis (EFE) is a pathologic condition of abnormal deposition of collagen and elastin within the endocardium of the heart. It is seen in conjunction with a variety of diseases including hypoplastic left heart syndrome and viral endocarditis. While an experimental model using heterotopic heart transplant in rats has been described, we sought to fully describe a mouse model that can be used to further elucidate the potential mechanisms of and treatments for EFE.

MATERIALS AND METHODS

The hearts of 2-day-old C57BL/6 mice were transplanted into the abdomen of 7-week-old C57BL/6 mice. At 2 weeks, the hearts were harvested and histologic analysis was performed using hematoxylin and eosin, Masson's trichrome, Russell-Movat's pentachrome, Picrosirius red, Hart's, Verhoeff-Van Gieson, and Weigert's Resorcin-Fuchsin stains. Additionally, one heart was analyzed using transmission electron microscopy (TEM).

RESULTS

Specimens demonstrated abnormal accumulation of both collagen and elastin within the endocardium with occasional expansion into the myocardium. Heterogeneity in extracellular matrix deposition was noted in the histologic specimens. In addition, TEM demonstrated the presence of excess collagen within the endocardium.

CONCLUSIONS

The heterotopic transplantation of an immature heart into a mouse results in changes consistent with EFE. This model is appropriate to investigate the etiology and treatment of EFE.

Fetal cardiac interventions: an update of therapeutic options

Objective

This article aims to present updated therapeutic options for fetal congenital heart diseases.

Methods

Data source for the present study was based on comprehensive literature retrieval on fetal cardiac interventions in terms of indications, technical approaches and clinical outcomes.

Results

About 5% of fetal congenital heart diseases are critical and timely intrauterine intervention may alleviate heart function. Candidates for fetal cardiac interventions are limited. These candidates may include critical aortic valve stenosis with evolving hypoplastic left heart syndrome, pulmonary atresia with an intact ventricular septum and evolving hypoplastic right heart syndrome, and hypoplastic left heart syndrome with an intact or highly restrictive atrial septum as well as fetal heart block. The advocated option are prenatal aortic valvuloplasty, pulmonary valvuloplasty, creation of atrial communication and fetal cardiac pacing.

Conclusion

Fetal cardiac interventions are feasible at midgestation with gradually improved technical success and fetal/postnatal survival due mainly to a well-trained multidisciplinary team, sophisticated equipment and better postnatal care.

Distention of the Immature Left Ventricle Triggers Development of Endocardial Fibroelastosis: An Animal Model of Endocardial Fibroelastosis Introducing Morphopathological Features of Evolving Fetal Hypoplastic Left Heart Syndrome

Background. Endocardial fibroelastosis (EFE), characterized by a diffuse endocardial thickening through collagen and elastin fibers, develops in the human fetal heart restricting growth of the left ventricle (LV). Recent advances in fetal imaging indicate that EFE development is directly associated with a distended, poorly contractile LV in evolving hypoplastic left heart syndrome (HLHS). In this study, we developed an animal model of EFE by introducing this human fetal LV morphopathology to an immature rat heart. Methods and Results. A neonatal donor heart, in which aortic regurgitation (AR) was created, was heterotopically transplanted into a recipient adult rat. AR successfully induced the LV morphology of evolving HLHS in the transplanted donor hearts, which resulted in the development of significant EFE covering the entire LV cavity within two weeks postoperatively. In contrast, posttransplants with a competent aortic valve displayed unloaded LVs with a trace of EFE. Conclusions. We could show that distention of the immature LV in combination with stagnant flow triggers EFE development in this animal model. This model would serve as a robust tool to develop therapeutic strategies to treat EFE while providing insight into its pathogenesis.

Endocardial fibroelastosis is caused by aberrant endothelial to mesenchymal transition

RATIONALE

Endocardial fibroelastosis (EFE) is a unique form of fibrosis, which forms a de novo subendocardial tissue layer encapsulating the myocardium and stunting its growth, and which is typically associated with congenital heart diseases of heterogeneous origin, such as hypoplastic left heart syndrome. Relevance of EFE was only recently highlighted through the establishment of staged biventricular repair surgery in infant patients with hypoplastic left heart syndrome, where surgical removal of EFE tissue has resulted in improvement in the restrictive physiology leading to the growth of the left ventricle in parallel with somatic growth. However, pathomechanisms underlying EFE formation are still scarce, and specific therapeutic targets are not yet known.

OBJECTIVE

Here, we aimed to investigate the cellular origins of EFE tissue and to gain insights into the underlying molecular mechanisms to ultimately develop novel therapeutic strategies.

METHODS AND RESULTS

By utilizing a novel EFE model of heterotopic transplantation of hearts from newborn reporter mice and by analyzing human EFE tissue, we demonstrate for the first time that fibrogenic cells within EFE tissue originate from endocardial endothelial cells via aberrant endothelial to mesenchymal transition. We further demonstrate that such aberrant endothelial to mesenchymal transition involving endocardial endothelial cells is caused by dysregulated transforming growth factor beta/bone morphogenetic proteins signaling and that this imbalance is at least in part caused by aberrant promoter methylation and subsequent transcriptional suppression of bone morphogenetic proteins 5 and 7. Finally, we provide evidence that supplementation of exogenous recombinant bone morphogenetic proteins 7 effectively ameliorates endothelial to mesenchymal transition and experimental EFE in rats.

CONCLUSIONS

In summary, our data point to aberrant endothelial to mesenchymal transition as a common denominator of infant EFE development in heterogeneous, congenital heart diseases, and to bone morphogenetic proteins 7 as an effective treatment for EFE and its restriction of heart growth.

Cardiovascular magnetic resonance parameters associated with early transplant-free survival in children with small left hearts following conversion from a univentricular to biventricular circulation

BACKGROUND

We sought to identify cardiovascular magnetic resonance (CMR) parameters associated with successful univentricular to biventricular conversion in patients with small left hearts.

METHODS

Patients with small left heart structures and a univentricular circulation who underwent CMR prior to biventricular conversion were retrospectively identified and divided into 2 anatomic groups: 1) borderline hypoplastic left heart structures (BHLHS), and 2) right-dominant atrioventricular canal (RDAVC). The primary outcome variable was transplant-free survival with a biventricular circulation.

RESULTS

In the BHLHS group (n = 22), 16 patients (73%) survived with a biventricular circulation over a median follow-up of 40 months (4-84). Survival was associated with a larger CMR left ventricular (LV) end-diastolic volume (EDV) (p = 0.001), higher LV-to-right ventricle (RV) stroke volume ratio (p < 0.001), and higher mitral-to-tricuspid inflow ratio (p = 0.04). For predicting biventricular survival, the addition of CMR threshold values to echocardiographic LV EDV improved sensitivity from 75% to 93% while maintaining specificity at 100%. In the RDAVC group (n = 10), 9 patients (90%) survived with a biventricular circulation over a median follow-up of 29 months (3-51). The minimum CMR values were a LV EDV of 22 ml/m² and a LV-to-RV stroke volume ratio of 0.19.

CONCLUSIONS

In BHLHS patients, a larger LV EDV, LV-to-RV stroke volume ratio, and mitral-to-tricuspid inflow ratio were associated with successful biventricular conversion. The addition of CMR parameters to echocardiographic measurements improved the sensitivity for predicting successful conversion. In RDAVC patients, the high success rate precluded discriminant analysis, but a range of CMR parameters permitting biventricular conversion were identified.

Percutaneous fetal cardiac interventions for structural heart disease

INTRODUCTION

Prenatal diagnosis provides valuable information regarding a variety of congenital heart defects. Some defects occur early in gestation with little change throughout pregnancy, whereas others evolve during mid and late gestation. Fetal cardiac intervention (FCI) affords the opportunity to interrupt progression of disease in this latter category, resulting in improved perinatal and lifelong outcomes.

AIM

This chapter addresses three lesions for which percutaneous FCI can be utilized: (1) aortic stenosis with evolving hypoplastic left heart syndrome, for which aortic valvuloplasty may prevent left ventricular hypoplasia and has yielded a biventricular circulation in approximately one third of cases; (2) hypoplastic left heart syndrome with intact atrial septum, for which relief of atrial restriction has potential to improve perinatal survival; and (3) pulmonary atresia with intact ventricular septum and evolving right ventricular hypoplasia, for which pulmonary valvuloplasty has resulted in a biventricular circulation in the majority of patients. The pathophysiology, rationale for intervention, patient selection criteria, procedural technique, and outcomes for each lesion will be reviewed. This chapter will also review complications of FCI and their treatment, and maternal and fetal anesthesia specific to FCI. The importance of a specialized center with experience managing infants delivered after FCI will also be addressed.

Left ventricular diastolic function and characteristics in fetal aortic stenosis

Fetal aortic balloon valvuloplasty (FAV) has shown promise in averting progression of midgestation aortic stenosis (AS) to hypoplastic left heart syndrome in a subset of patients. Patients who achieve biventricular circulation after FAV frequently have left ventricular (LV) diastolic dysfunction (DD). This study evaluates DD in fetuses with AS by comparing echocardiographic indices of LV diastolic function in fetuses underwent FAV (n = 20) with controls (n = 40) and evaluates for LV factors associated with DD in patients with FAV. We also compared pre-FAV and post-FAV DD variables (n = 16). Median gestational age (24 weeks, range 18 to 29 weeks) and fetal heart rate were similar between FAV and controls. Compared with controls, patients with FAV had universally abnormal LV diastolic parameters including fused mitral inflow E and A waves (p = 0.008), higher E velocity (p <0.001), shorter mitral inflow time (p = 0.001), lower LV lateral annulus E' (p <0.001), septal E' (p = 0.003), and higher E/E' (p <0.001) than controls. Patients with FAV had abnormal right ventricular mechanics with higher tricuspid inflow E velocity (p <0.001) and shorter tricuspid inflow time (p = 0.03). Worse LV diastolic function (lower LV E') was associated with higher endocardial fibroelastosis grade (r = 0.74, p <0.001), large LV volume (r = 0.55, p = 0.013), and sphericity (r = 0.58, p = 0.009) and with lower LV pressure by mitral regurgitation jet (r = -0.68, p <0.001). Post-FAV, fewer patients had fused mitral inflow E and A than pre-FAV (p = 0.05) and septal E' was higher (=0.04). In conclusion, fetuses with midgestation AS have evidence of marked DD. Worse DD is associated with larger, more spherical LV, with more extensive endocardial fibroelastosis and lower LV pressure.

Fetal interventions for congenital heart disease in Brazil

Fetal interventions have been performed for some congenital heart diseases. However, these procedures have not gained wide acceptance due to concerns about their efficacy and safety. The aim of this study was to report on a preliminary experience with fetal cardiac interventions in Brazil. Twenty-two cardiac interventions were performed in 21 fetuses. Thirteen fetuses had critical aortic stenosis (CAS), 4 had hypoplastic left heart syndrome (HLHS) and intact interatrial septum or small patent foramen ovale, 1 had pulmonary atresia with intact ventricular septum (IVS), and 3 had critical pulmonary stenosis (CPS). The main outcome variables evaluated were technical success and procedural complications as well as pregnancy and postnatal outcomes. Success was achieved in 20 of 22 procedures (91%) with 1 failed aortic and 1 failed pulmonary valvuloplasties. There was 1 fetal death. No maternal complications occurred. One patient with CAS, severe mitral regurgitation, and hydrops died postnatally within 5 months of age. All patients with HLHS and restrictive atrial septum died after interventional or surgical procedures and prolonged hospitalizations. All patients with CPS/IVS survived and achieved a biventricular (BV) circulation after neonatal valvuloplasty and ductal stenting. A BV circulation was achieved in 4 of 8 patients with CAS and evolving HLHS (one still in utero), including 2 with initial borderline left ventricles (LV) in whom surgical LV overhaul was performed at 9 months of age. In this preliminary experience, the feasibility of fetal cardiac interventions and their outcomes were similar to those previously reported.

Ventricular strain in fetuses with aortic stenosis and evolving hypoplastic left heart syndrome before and after prenatal aortic valvuloplasty

OBJECTIVE

The impact of prenatal intervention on fetal cardiac function has not been well defined. We assessed standard ventricular function parameters and strain in fetuses with evolving hypoplastic left heart syndrome (HLHS) treated with fetal aortic valvuloplasty (fAVP).

METHODS

Fetuses with valvar aortic stenosis that underwent fAVP were studied. Echocardiographic images prior to intervention (Pre), within 1 week after fAVP (Post), and at the last prenatal follow-up examination (FU) were analyzed. Left ventricular (LV) circumferential (LVCS) and longitudinal strain (LVLS), right ventricular (RV) longitudinal strain (RVLS), and LV end-diastolic dimension Z-scores (LVIDD-Z) were documented and compared according to postnatal outcome.

RESULTS

Among 57 fetuses studied, the postnatal outcome was biventricular in 23 and univentricular in 34. Prior to fAVP, strain was <4 in most cases, regardless of outcome. Biventricular fetuses had higher LVCS and LVLS segmental strain than univentricular fetuses. Among fetuses with a biventricular outcome, LVCS and LVLS increased as LVIDD-Z decreased in late gestation, whereas LVCS and LVLS remained <4 in univentricular fetuses, although the LVIDD-Z decreased to <0 in all cases. Septal RVLS increased after fAVP in the biventricular but not the univentricular outcome group.

CONCLUSION

In utero aortic valve dilation appears to have a beneficial effect on both LV and RV function in some fetuses with evolving HLHS.

Ultrasound assessment of fetal cardiac function

Introduction: Fetal heart evaluation with US is feasible and reproducible, although challenging due to the smallness of the heart, the high heart rate and limited access to the fetus. However, some cardiac parameters have already shown a strong correlation with outcomes and may soon be incorporated into clinical practice. Materials and Methods: Cardiac function assessment has proven utility in the differential diagnosis of cardiomyopathies or prediction of perinatal mortality in congenital heart disease. In addition, some cardiac parameters with high sensitivity such as MPI or annular peak velocities have shown promising results in monitoring and predicting outcome in intrauterine growth restriction or congenital diaphragmatic hernia. Conclusion: Cardiac function can be adequately evaluated in most fetuses when appropriate expertise, equipment and time are available. Fetal cardiac function assessment is a promising tool that may soon be incorporated into clinical practice to diagnose, monitor or predict outcome in some fetal conditions. Thus, more research is warranted to further define specific protocols for each fetal condition that may affect cardiac function.

Obstructive left heart disease in neonates with a "borderline" left ventricle: diagnostic challenges to choosing the best outcome

In most newborns with left heart obstruction, the choice between a single-ventricle or biventricular management pathway is clear. However, in some neonates with a "borderline" left ventricle, this decision is difficult. Existing criteria do not reliably identify neonates who will have a good long-term outlook after biventricular repair (BVR). The objective of this study was prospective assessment of the outcome after BVR for newborns in whom the left ventricle (LV) was considered "borderline" by an expert group. This study was a prospective follow-up evaluation of neonates with obstructive left heart disease related to a "borderline" LV who underwent biventricular management between January 2005 and April 2011. Of 154 neonates who required intervention for left heart obstruction, 13 (7.8 %) met the echocardiographic (echo) inclusion criteria. At the first and last echo, the z-scores were respectively -1.76 ± 1.37 and -0.66 ± 1.47 (p = 0.013) for the mitral valve, -1.02 ± 1.57 and -0.23 ± 1.78 (p = 0.056) for the aortic valve, and 13.77 ± 5.8 and 20.85 ± 8.9 ml/m(2) (p = 0.006) for the LV end-diastolic volume. At this writing, all 12 survivors are clinically well. However, LV diastolic dysfunction and pulmonary artery hypertension was present in 5 (36 %) of 12 patients. Endocardial fibroelastosis (EFE) was detected in five patients at the last follow-up echo, but only in two patients preoperatively. Cardiac magnetic resonance imaging did not confirm EFE in any of assessed patients. The study authors could not reliably predict the outcome after BVR for neonates with left heart obstruction and a "borderline" LV. The presence of EFE with consequent diastolic dysfunction is more important than LV volume in determining the outcome. Prospective identification of EFE remains challenging.

Fetal cardiac interventions: rationale, risk and benefit

Fetal congenital heart disease may progress during pregnancy and may lead to irreversible myocardial or pulmonary damage. The rationale of fetal intracardiac interventions is to change fetal hemodynamics, prevent secondary damage and improve long-term outcome at an acceptable risk for mother and fetus. This review focuses on the current experience about patient selection, risks and benefits of this technique.

An animal model of endocardial fibroelastosis

BACKGROUND

Hypoplastic left heart syndrome (HLHS) is one of the most common severe congenital cardiac anomalies, characterized by a marked hypoplasia of left-sided structures of the heart, which is commonly accompanied by a thick layer of fibroelastic tissue, termed endocardial fibroelastosis (EFE). Because human EFE develops only in fetal or neonatal hearts, and often in association with reduced blood flow, we sought to mimic these conditions by subjecting neonatal and 2-wk-old rat hearts to variations of the heterotopically transplanted heart model with either no intracavitary or normal flow and compare endocardium with human EFE tissue.

MATERIALS AND METHODS

Hearts obtained from neonatal and 2-wk-old rats were heterotopically transplanted in young adult Lewis rats in a working (loaded) or nonworking (unloaded) mode. After 2-wk survival, hearts were explanted for histologic analysis by staining for collagen, elastin, and cellular elements. These sections were compared with human EFE tissue from HLHS.

RESULTS

EFE, consisting of collagen and elastin with scarce cellular and vascular components, developed only in neonatal unloaded transplanted hearts and displayed the same histopathologic findings as EFE from patients with HLHS. Loaded hearts and 2-wk-old hearts did not show these alterations.

CONCLUSIONS

This animal model for EFE will serve as a tool to study the mechanisms of EFE formation, such as fluid forces, in HLHS in a systematic manner. A better understanding of the underlying cause of the EFE formation in HLHS will help to develop novel treatment strategies to better preserve growth of the hypoplastic left ventricle.

Right ventricular mechanics in the fetus with hypoplastic left heart syndrome

BACKGROUND

Right ventricular mechanics influence outcomes in patients with hypoplastic left heart syndrome (HLHS). The aim of this study was to determine whether differences in right ventricular performance have their origins in fetal life and if the architectural character of the hypoplastic left ventricle affects right ventricular mechanics.

METHODS

The first complete fetal echocardiograms after 17 weeks' gestation were reviewed in 84 fetuses with HLHS and in 115 gestational age-matched normal controls. Inflow, outflow, and myocardial tissue Doppler velocities were measured. E/A and E/e' ratios and right ventricular myocardial performance index were calculated.

RESULTS

In fetuses with HLHS, there were lower tricuspid E/A ratios (mean, 0.6 ± 0.1 vs 0.7 ± 0.1; P < .001), higher E/e' ratios (mean, 8.1 ± 2.6 vs 7.0 ± 1.3; P = .006), and higher right ventricular myocardial performance indices (mean, 0.47 ± 0.14 vs 0.40 ± 0.10; P < .001) compared with controls. Among fetuses with HLHS grouped according to left ventricular architecture, those with left ventricular endocardial fibroelastosis had the most striking differences in right ventricular mechanics.

CONCLUSIONS

Right ventricular mechanics are different from normal in fetuses with HLHS and are influenced by the presence of left ventricular endocardial fibroelastosis. These differences precede the imposition of undue loading conditions as a consequence of surgical palliation and may offer clues to the development of later right ventricular failure.