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.

Factors associated with morbidity, mortality, and hemodynamic failure after biventricular conversion in borderline hypoplastic left hearts

OBJECTIVE

A subset of patients with borderline hypoplastic left heart may be candidates for single to biventricular conversion, but long-term morbidity and mortality persist. Prior studies have shown conflicting results regarding the association of preoperative diastolic dysfunction and outcome, and patient selection remains challenging.

METHODS

Patients with borderline hypoplastic left heart undergoing biventricular conversion from 2005 to 2017 were included. Cox regression identified preoperative factors associated with a composite outcome of time to mortality, heart transplant, takedown to single ventricle circulation, or hemodynamic failure (defined as left ventricular end-diastolic pressure >20 mm Hg, mean pulmonary artery pressure >35 mm Hg, or pulmonary vascular resistance >6 international Woods units).

RESULTS

Among 43 patients, 20 (46%) met the outcome, with a median time to outcome of 5.2 years. On univariate analysis, endocardial fibroelastosis, lower left ventricular end-diastolic volume/body surface area (when <50 mL/m2), lower left ventricular stroke volume/body surface area (when <32 mL/m2), and lower left:right ventricular stroke volume ratio (when <0.7) were associated with outcome; higher preoperative left ventricular end-diastolic pressure was not. Multivariable analysis demonstrated that endocardial fibroelastosis (hazard ratio, 5.1, 95% confidence interval, 1.5-22.7, P = .033) and left ventricular stroke volume/body surface area 28 mL/m2 or less (hazard ratio, 4.3, 95% confidence interval, 1.5-12.3, P = .006) were independently associated with a higher hazard of the outcome. Approximately all patients (86%) with endocardial fibroelastosis and left ventricular stroke volume/body surface area 28 mL/m2 or less met the outcome compared with 10% of those without endocardial fibroelastosis and with higher stroke volume/body surface area.

CONCLUSIONS

History of endocardial fibroelastosis and smaller left ventricular stroke volume/body surface area are independent factors associated with adverse outcomes among patients with borderline hypoplastic left heart undergoing biventricular conversion. Normal preoperative left ventricular end-diastolic pressure is insufficient to reassure against diastolic dysfunction after biventricular conversion.

Patterns of endocardial fibroelastosis without atrioventricular block in fetuses exposed to anti-Ro/SSA antibodies

Anti-Ro/SSA-antibody-mediated endocardial fibroelastosis (EFE) without atrioventricular (AV) block at presentation is a rare cardiac phenotype. We report on 11 fetuses with this rare type of anti-Ro/SSA-antibody-mediated cardiac involvement, presenting with a distinctive echocardiographic pattern of EFE. Eleven fetuses with isolated EFE at presentation were included from four cardiac centers, and experienced fetal cardiologists reached a consensus regarding EFE location on echocardiography at presentation. Interval changes to subsequent fetal and postnatal echocardiograms were assessed to evaluate response to therapy. Echocardiographic markers of cardiac performance, including diastolic function and AV conduction, were reviewed. Ten fetuses were found to have EFE of the aortic root, proximal aorta and/or left ventricular outflow tract. In the same 10 cases, EFE of the pulmonary root, pulmonary artery and/or right ventricular outflow tract was identified. Six cases had atrial EFE and six had EFE of the crux. Four cases were known to be positive for anti-Ro/SSA antibodies prior to diagnosis, whereas, in the remaining seven, echocardiographic findings prompted testing, which was positive in all cases. The AV interval at presentation was normal in all cases, but one fetus subsequently developed AV block. Nine patients were treated with transplacental dexamethasone, five of which also received intravenous immunoglobulin (IVIG), and one received IVIG only. Of the 10 treated cases, six had improvement in EFE as shown by serial imaging and, in four cases, the severity was unchanged. All patients were liveborn. In our cohort, EFE of the aortic and pulmonary arteries and outflow tracts was nearly universal, and involvement of the atria and the crux of the heart was also common. The high survival rate and low burden of AV block are also suggestive of a distinct phenotype of anti-Ro/SSA-antibody-mediated cardiac disease with a favorable prognosis. © 2023 International Society of Ultrasound in Obstetrics and Gynecology.

Endocardial Fibroelastosis as an Independent Predictor of Atrioventricular Valve Rupture in Maternal Autoimmune Antibody Exposed Fetus: A Systematic Review with Clinicopathologic Analysis

BACKGROUND

Neonatal lupus (NL) is a clinical syndrome that develops in the fetus as a result of maternal autoimmune antibodies. Congenital complete heart block (CHB) is the most common manifestation, while extranodal cardiac manifestations of NL, such as endocardial fibroelastosis (EFE) and myocarditis, are rare but more serious. Less is known about this atrioventricular valve rupture due to valvulitis as a consequence of maternal autoantibodies. We have described a case of cardiac neonatal lupus with an antenatally detected CHB patient who developed mitral and tricuspid valve chordal rupture at 45 days of age. We compared the cardiac histopathology and the fetal cardiac echocardiographic findings of this case with another fetus that was aborted after being antenatally diagnosed with CHB but without valvar rupture. A narrative analysis after a systematic review of the literature regarding atrioventricular valve apparatus rupture due to autoimmune etiology along with maternal characteristics, presentation, treatment, and outcome have been discussed in this article.

OBJECTIVES

To describe published data on atrioventricular valve rupture in neonatal lupus, including clinical presentation, diagnostic evaluation, management, and outcomes.

METHODS

We conducted a PRISMA-compliant descriptive systematic examination of case reports that included accounts of lupus during pregnancy or in the newborn period that resulted in an atrioventricular valve rupture. We gathered information on the patient's demographics, the details of the valve rupture and other comorbidities, the maternal therapy, the clinical course, and the results. We also used a standardized method to evaluate the cases' quality. A total of 12 cases were investigated, with 11 cases drawn from 10 case reports or case series and 1 from our own experience.

RESULTS

Tricuspid valve rupture (50%) is more common than mitral valve rupture (17%). Unlike mitral valve rupture, which occurs postnatally, the timing of tricuspid valve rupture is perinatal. A total of 33% of the patients had concomitant complete heart block, while 75% of the patients had endocardial fibroelastosis on an antenatal ultrasound. Antenatal changes pertaining to endocardial fibroelastosis can be seen as early as 19 weeks of gestation. Patients with both valve ruptures generally have a poor prognosis, especially if they occur at close intervals.

CONCLUSION

Atrioventricular valve rupture in neonatal lupus is rare. A majority of patients with valve rupture had antenatally detected endocardial fibroelastosis in the valvar apparatus. Appropriate and expedited surgical repair of ruptured atrioventricular valves is feasible and has a low mortality risk. Rupture of both atrioventricular valves occurring at close intervals carries a high mortality risk.

Pulmonary atresia with intact ventricular septum in the setting of D-transposition of the great arteries associated with hypoplastic left ventricle and severe mitral regurgitation

We report the first successful Glenn procedure for pulmonary atresia with intact ventricular septum in the setting of D-transposition of the great arteries. This case was complicated by hypoplastic left ventricle and severe mitral regurgitation. Partial closure of the mitral valve at the time of Blalock-Taussig shunting resulted in improvement of heart failure.

Paediatric dilated cardiomyopathy with and without endocardial fibroelastosis - a pathological analysis of 89 explants

Heart failure due to dilated cardiomyopathy is a major indication for paediatric cardiac transplantation. Endocardial fibroelastosis is a recognised pathological finding of unknown prognostic significance in paediatric dilated cardiomyopathy. To evaluate the nature of the association between left ventricular endocardial fibroelastosis and paediatric dilated cardiomyopathy, we reviewed surgical pathology reports of dilated cardiomyopathy explants (1986-2016) in order to characterise the pathological findings and to compare and contrast their frequency among four age groups: less than 1 year; 1-5 years; 6-10 years; and greater than 11 years. The 89 explants (47 males and 42 females) were all characterised by increased weight and left ventricular chamber dilatation without increased wall thickness. Ninety-five per cent of the specimens in the two youngest subsets had left ventricular endocardial fibroelastosis. Compared to the oldest age group, recipients aged 1-5 years had a 6-fold increase and those younger than 1 year a 19-fold increase in the odds of observing left ventricular endocardial fibroelastosis. Explants with and without endocardial fibroelastosis were otherwise phenotypically similar. In paediatric dilated cardiomyopathy endocardial fibroelastosis is a very common pathological finding, especially in infants and young children. We propose that the descriptive, clinico-pathological designation "Dilated Cardiomyopathy with Endocardial Fibroelastosis" should be adopted to facilitate future investigation into the potential prognostic/therapeutic significance of left ventricular endocardial fibroelastosis.

Cardiac manifestations in a Chinese cohort of fetuses from mothers with anti-Ro and anti-La antibodies

OBJECTIVES

To analyze the clinical characteristics, echocardiographic features, and prognosis of fetuses based on three groups of cardiac manifestations associated with maternal anti-Ro and anti-La antibodies in China. This study included three groups: the isolated-arrhythmia, isolated-endocardial fibroelastosis (EFE), and mixed groups.

METHODS

We prospectively evaluated 36 fetuses with cardiac manifestations due to maternal anti-Ro and anti-La antibodies from our center between 2016 and 2020 in China. Clinical and echocardiographic data were collected.

RESULTS

There were 13 patients (36%) in the isolated-arrhythmia group, eight (22%) in the isolated-EFE group, and 15 (42%) in the mixed group. All patients in the isolated-EFE group presented with mild EFE. Severe EFE was identified in four patients (27%) in the mixed group. Atrioventricular block (AVB) was more common in the isolated-arrhythmia group (13, 100%) than in the mixed group (6, 40%; p = 0.001). Moderate-severe mitral regurgitation (p = 0.006), dilated cardiomyopathy (DCM, p = 0.017), and low cardiovascular profile scores (p = 0.013) were more common in the mixed group than in the other two groups. Twenty-one mothers decided to terminate the pregnancy and 15 fetuses were born with regular perinatal treatment. They all survived at 1 year of age. One patient in the isolated-arrhythmia group and two in the mixed group required a pacemaker due to third-degree AVB or atrioventricular junctional rhythm. Five patients in the isolated-EFE group and five in the mixed group had no DCM or heart failure and the location of mild EFE was significantly reduced.

CONCLUSION

Fetal cardiac manifestations due to maternal anti-Ro and anti-La antibodies can be divided into three groups, i.e., the isolated-arrhythmia, isolated-EFE, and mixed groups. AVB usually occurs in the isolated-arrhythmia group. Severe EFE, moderate-severe mitral regurgitation, and DCM mainly appear in the mixed group. Location of mild EFE significantly reduces after birth and the outcome of fetuses with mild EFE depends on the presence of arrhythmia and its subtypes.

The value of cardiac magnetic resonance imaging in endocardial fibroelastosis

INTRODUCTION

Endocardial fibroelastosis (EFE), an uncommon congenital heart disorder often occurring in infants, has a poor prognosis. It is of great significance to perform early diagnosis and accurately analyze cardiac function to enable further clinical treatment and prognosis decisions. This study aimed to explore the findings of cardiac magnetic resonance (CMR) in patients with EFE, including morphological changes and cardiac function analyses. Additionally, we compared the difference in the evaluation of the cardiac function between CMR and echocardiography (Echo).

METHODS

Eleven patients with EFE (nine females and two males, aged between 0.3 and 1.9 years), treated in our hospital, were analyzed retrospectively. Left ventricular posterior wall thickness (LVPW), anterior wall thickness (LVAW), fractional shortening (FS), ejection fraction (EF), end-systolic diameter (ESD), end-diastolic diameter (EDD), end-systolic volume (ESV), and end-diastolic volume (EDV) were assessed using both Echo and CMR. The Original Ross classification and the New York Heart Association functional classification were used to grade the patients' cardiac function. The correlations between clinical cardiac function classification and MRI- and Echo-derived imaging data were determined.

RESULTS

All patients showed a thickened endocardium and left ventricle globular dilatation on CMR. We observed significant systolic dysfunction and whole or segmental abnormal ventricular movement. Compared with those measured by Echo, the EF, FS, and EDV values were significantly lower when measured using CMR. Compared with Echo measurements, the ESV, ESD, LVAW, and LVPW values were significantly higher when measured using CMR. CMR-measured EF and FS correlated better with the clinical cardiac functional score than those derived from Echo (EF, r = 0.646 > 0.224; FS, r = 0.627 > 0.245, respectively).

CONCLUSION

In patients with EFE, the characteristic morphological changes of the heart could be displayed accurately using CMR. The parameters measured by CMR were more accurate than those of Echo and correlated well with clinical cardiac function scores, mainly because it does not make invalid geometrical assumptions.

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.

Intraventricular Septation in the Context of Dilated Cardiomyopathy Associated With TTN Mutation

A 6-month-old infant boy presented with symptomatic heart failure. Dilated cardiomyopathy was found in association with a mutation in TTN. Structural heart disease included novel septation of the left ventricle with a fenestrated membrane resulting from aberrant congenital mitral valve apparatus formation. (Level of Difficulty: Advanced.)

Three de novo variants in KMT2A (MLL) identified by whole exome sequencing in patients with Wiedemann-Steiner syndrome

Background

Wiedemann–Steiner syndrome (WSS) is an autosomal dominant disorder characterized by short stature, hypertrichosis, intellectual disability, developmental delay, along with facial dysmorphism. WSS patients exhibit great phenotypic heterogeneities. Some variants in KMT2A (MLL) gene have been identified as the cause of WSS.

Methods

Whole exome sequencing on the probands followed by Sanger sequencing validations in the family were applied to determine genetic variants. In silico analyses were used for predicting potential effects of the variants.

Results

We identified three novel de novo heterozygous variants: c.883A>T (p.Lys295*), c.4171C>T (p.Gln1391*), and c.3499T>C (p.Cys1167Arg), in KMT2A gene from three unrelated Chinese WSS patients. According to the American College of Medical Genetics and Genomics (ACMG) guidelines, these three variants were classified as pathogenic, pathogenic and likely pathogenic variant, respectively. By reviewing all the available cases with same mutated KMT2A regions as the three patients had, we found that in addition to the representative symptoms, our patients exhibited some sporadically observed symptoms, such as severe ophthalmological symptoms, endocardial fibroelastosis, cytomegalovirus infection, and feet eversion. We also revealed that variants in different KMT2A regions contribute to the phenotypic heterogeneity of WSS, highlighting challenges in the diagnosis of syndromic disorders spanning a broad phenotypic spectrum.

Conclusion

Our study would aid in further broadening our knowledge about the genotype–phenotype correlation of WSS.

Dilated cardiomyopathy with endocardial fibroelastosis in a juvenile Pallas cat

Dilated cardiomyopathy (DCM) is a myocardial disease characterized by ventricular chamber dilation associated with systolic myocardial dysfunction in the absence of other cardiac lesions. DCM occasionally develops in conjunction with proliferation of fibroelastic fibers in the endocardium, producing endocardial fibroelastosis (EFE). Although early reports describe EFE as a primary disease, evidence now suggests that EFE may develop as a response to myocardial dysfunction. Echocardiographic evaluation of a 4-wk-old Pallas cat ( Otocolobus manul) with respiratory distress revealed enlargement of both atria, enlarged end-systolic left ventricular dimension, and left ventricular dilation. DCM was diagnosed, and the cat was euthanized, given the poor prognosis. Postmortem examination revealed pericardial effusion and biventricular and biatrial enlargement. The interventricular septum and free walls of ventricles were thin. Histologically, the endocardium of the left and right ventricles was diffusely thickened; Verhoeff-Van Gieson staining of the left ventricular endocardium revealed a moderate amount of endocardial accumulation of elastin and collagen. These fibers were more prominent in papillary muscles and around coronary blood vessels. Based on these findings, we diagnosed DCM with EFE. Cardiac diseases are rarely diagnosed in wild felids.

Misdiagnosed anomalous left coronary artery from the pulmonary artery as endocardial fibroelastosis in infancy: A case series

INTRODUCTION

Anomalous left coronary artery from the pulmonary artery (ALCAPA) is a rare but severe congenital cardiac malformation. The prognosis mainly depends on the early and accurate diagnosis and treatment. However, without a typical and specific clinical manifestation in early stage, ALCAPA has a higher rate of false initial diagnosis.

DIAGNOSTIC AND THERAPEUTIC PROCEDURE

Three infants with impaired left ventricle (LV) function, LV enlargement, mitral valve regurgitation (MR), and LV endocardium thickness were initially diagnosed as endocardial fibroelastosis (EFE). Due to the treatment effectiveness with prednisone acetate and digoxin, abnormal Q waves with T inversion, and dilated right coronary artery (RCA), the diagnosis of ALCAPA was suspected. Lastly, cardiac angiography confirmed the diagnosis. All of them were transferred to the cardiac surgery department and received a successful surgical repair. The follow-up results showed that abnormal Q waves with T waves inversion on electrocardiogram gradually regressed and disappeared, LV ejection fraction and LV dilation returned to a normal range after surgery, with alleviation of MR. Besides, endocardial thickness secondary to ischemia also returned to normal.

CONCLUSION

ALCAPA should be suspected when confronted with patients with left heart enlargement, impaired left ventricular function, and signs of myocardial ischemia, particularly in infancy. EFE is an important differential diagnosis and may also arise as a result of ALCAPA. Abnormal Q waves with T waves inversion, particularly in avL, dilated RCA and increased ratio of RCA/AO are important differential key points for the identification of ALCAPA and EFE. Awareness of this condition is essential for prompt recognition and referral to a tertiary cardiac center to enable early surgical intervention and improved prognosis for these children.

Autoimmune congenital heart block: complex and unusual situations

Autoimmune congenital heart block (ACHB) is an immune-mediated cardiac disease included among the manifestations collectively referred to as neonatal lupus. The placental transference of maternal Ro/La autoantibodies may damage the conduction tissues during fetal development leading to blocking of signal conduction at the atrioventricular (AV) node in an otherwise structurally normal heart. Irreversible complete AV block is the main cardiac manifestation of ACHB, but some babies may develop endocardial fibroelastosis, valvular insufficiency, and/or frank cardiomyopathies with significantly reduced cardiac function requiring transplant. The severity of ACHB is illustrated by a global mortality rate of 20% and pacemaker rates of at least 64%, often within the first year of life. This review analyses the main complex and/or unusual clinical situations associated with ACHB, including unusual maternal immunological profiles, infrequent maternal autoimmune diseases, cardiac damage unrelated to AV block, fetal invasive management, late complications after birth, risk of congenital heart block (CHB) in ovodonation and in vitro fertilization techniques, the role of maternal features other than autoimmunity, the influence of the birth order or the risk of CHB in twins and triplets.

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.

Characterising adequacy or inadequacy of the borderline left ventricle: what tools can we use?

Borderline left ventricle refers to a spectrum of left ventricular underdevelopment, typically associated with other cardiac anomalies. The left ventricle may be mildly hypoplastic, as is sometimes seen accompanying aortic coarctation, or it can be severely hypoplastic, as is seen in hypoplastic left heart syndrome. For patients with a borderline left ventricle that is at either extreme, the treatment decision is relatively straightforward. Those with the most severe form of left ventricle hypoplasia will require single ventricle palliation or cardiac transplantation, whereas those with the mildest form may not need any intervention. It is the management strategy of children that fall within the grey zone of the spectrum, which continues to be controversial and remains variable within and among different institutions. Cardiac diseases with associated left ventricle hypoplasia include critical aortic stenosis, mitral stenosis, coarctation of the aorta, arch hypoplasia, cor triatriatum, unbalanced common atrioventricular canal, Shone's complex, total anomalous pulmonary venous return, and complex conotruncal abnormalities. In this review, we will discuss the assessment and management of infants with borderline left ventricle with critical aortic stenosis or arch obstruction and associated mitral anomalies.

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.

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.

Noncompaction in the fetus and neonate: an autopsy study

Noncompaction refers to an uncommon structural abnormality of the heart's ventricular myocardium characterized by an abnormally thick layer of left ventricular trabeculations, as well as hypoplastic papillary muscles. The condition is associated with a variable clinical phenotype including heart failure, thromboembolism, and sudden death. In this retrospective study of fetal and neonatal autopsy hearts with noncompaction, clinical profiles were correlated with gross and histologic findings and compared with a set of age-matched controls. Pathologic criteria for noncompaction included hypoplastic left ventricular papillary muscles, abnormal trabecular architecture and greater than 50% penetration of the left ventricular wall thickness by intertrabecular recesses. Among eight fetuses and full-term neonates with pathologic features of noncompaction, all had evidence of severe heart failure, including four with complete heart block and two others with bradycardia. None experienced sudden death. Seven of eight hearts had associated heart malformations-four with left atrial isomerism, two with aortic and/or pulmonary valve dysplasia consistent with stenosis and, one with atrial septal defect. One heart with noncompaction had no associated malformations. With characteristic excessive trabeculation in the left ventricle, noncompaction also included biventricular endocardial fibroelastosis that denoted right ventricular involvement in all hearts. Thus, (1) among autopsied fetuses and neonates with noncompaction, heart failure including heart block is a common cause of death, (2) noncompaction is often associated with various cardiovascular malformations, but even in isolation it can be the basis for severe cardiac failure, and (3) biventricular endocardial fibroelastosis in noncompaction suggests a global pathologic process.

Endocardial fibroelastosis in a quarterhorse mare

A 4-year-old crossbred Quarterhorse mare was submitted to the Clemson Veterinary Diagnostic Center for necropsy examination with a chronic history of inappetence, weight loss and lethargy. Prior to death the horse had developed mild diarrhoea and began showing evidence of colic. Necropsy examination revealed a markedly enlarged heart due predominantly to marked dilation of the right atrium, tortuous congested mesenteric blood vessels, marked ascites, pleural effusion and pulmonary oedema. Further examination of the heart showed the endocardium of the left side of the heart, including the mitral valve leaflets, to be diffusely thickened. Microscopically, the endocardial thickening was due to deposition of fibrous connective tissue and elastin fibres. These findings are consistent with a diagnosis of endocardial fibroelastosis.

Cardiac transplantation in a neonate with endocardial fibroelastosis

An investigational orthotopic cardiac transplantation was performed to manage subendocardial fibroelastosis in a neonate. No unmanageable technical complications arose from the transplantation. Postoperative observation showed the infant developed normally except for moderate cerebral palsy.