Noncompaction Phenotype Research Articles

Characterisation of the novel SCN5A-P1891A variant, implicated in left ventricular noncompaction cardiomyopathy in a Finnish family, using human induced pluripotent stem cell-derived cardiomyocytes

Abstract Introduction Left ventricular noncompaction (LVNC) is a heterogenous cardiomyopathy characterised by an extensively trabeculated left ventricle (LV). Several genetic variants that perturb trabeculae compaction, and thus LV maturation, have been reported [1]. However, the precise mechanisms underpinning this have proven contentious with, for example, differentially aberrant cardiomyocyte proliferation implicated in the development of LVNC [2,3]. Purpose In this study, we investigate a novel SCN5A variant, P1891A, which is associated with LVNC in a Finnish family. We ascertain the effects of this variant through the characterisation of variant-carrying human induced pluripotent stem cell-derived cardiomyocytes (P1891A-hiPSC-CMs). Methods We isolated dermal fibroblasts from a symptomatic member of a Finnish family carrying the SCN5A-P1891A variant; derived P1891A-hiPSCs via nucleofection with reprogramming plasmids [4]; and differentiated these into hiPSC-CMs alongside healthy control-hiPSCs. We determined the action potential (AP) and sodium- (INa) and calcium-current (ICa) densities of hiPSC-CMs via patch-clamp. We investigated gene expression in hiPSC-CMs through qPCR and employed Multiple Approaches Combined (MCA) proteomics [5] in SCN5A-transfected HEK293-like cells to elucidate protein-protein interactions (PPI). We subjected hiPSC-CMs to mechanical stretch [6] to examine their stress response and assessed their proliferation capacity via high-content analysis for the percentage of BrdU positive hiPSC-CMs following mitogenic stimulation (5 µM CHIR99021 and 1 µM SB203580). Finally, we ascertained contractile kinetics and apparent contractile force using fibrin hydrogel-based engineered heart tissues (EHTs) [7]. Results The P1891A-hiPSC-CMs demonstrated elevated INa density alongside enhanced arrhythmogenicity relative to healthy control hiPSC-CMs although, AP kinetics and ICa density were unperturbed (Fig. 1). Under baseline conditions, P1891A-hiPSC-CMs exhibited higher SCN5A gene expression and proteomics revealed a reduction in PPI. Baseline proliferation was unchanged; however, aged P1891A-hiPSC-CMs had enhanced proliferative capacity following mitogenic stimulation. Further, the P1891A-hiPSC-CMs displayed impaired tolerance to mechanical stretch as evidenced by upregulated NPPB and ACTA1 expression. In the context of the EHT, P1891A-hiPSC-CMs yielded disparate phenotypes. Whilst a subset compacted fully and yielded weaker contractile parameters relative to healthy control EHTs, the majority of P1891A-hiPSC-CM EHTs failed to fully compact thereby recapitulating the LVNC phenotype (Fig. 2). Conclusions This study presents a unique aetiology of LVNC and links, for the first time, SCN5A mutations with enhanced human cardiomyocyte proliferation. The ability to recapture the noncompaction phenotype in EHTs presents a powerful model for future mechanistic research and drug development.

Morphological, electrophysiological, and molecular alterations in foetal noncompacted cardiomyopathy induced by disruption of ROCK signalling.

Left ventricular noncompaction cardiomyopathy is associated with heart failure, arrhythmia, and sudden cardiac death. The developmental mechanism underpinning noncompaction in the adult heart is still not fully understood, with lack of trabeculae compaction, hypertrabeculation, and loss of proliferation cited as possible causes. To study this, we utilised a mouse model of aberrant Rho kinase (ROCK) signalling in cardiomyocytes, which led to a noncompaction phenotype during embryogenesis, and monitored how this progressed after birth and into adulthood. The cause of the early noncompaction at E15.5 was attributed to a decrease in proliferation in the developing ventricular wall. By E18.5, the phenotype became patchy, with regions of noncompaction interspersed with thick compacted areas of ventricular wall. To study how this altered myoarchitecture of the heart influenced impulse propagation in the developing and adult heart, we used histology with immunohistochemistry for gap junction protein expression, optical mapping, and electrocardiography. At the prenatal stages, a clear reduction in left ventricular wall thickness, accompanied by abnormal conduction of the ectopically paced beat in that area, was observed in mutant hearts. This correlated with increased expression of connexin-40 and connexin-43 in noncompacted trabeculae. In postnatal stages, left ventricular noncompaction was resolved, but the right ventricular wall remained structurally abnormal through to adulthood with cardiomyocyte hypertrophy and retention of myocardial crypts. Thus, this is a novel model of self-correcting embryonic hypertrabeculation cardiomyopathy, but it highlights that remodelling potential differs between the left and right ventricles. We conclude that disruption of ROCK signalling induces both morphological and electrophysiological changes that evolve over time, highlighting the link between myocyte proliferation and noncompaction phenotypes and electrophysiological differentiation.

Left Ventricular Non-Compaction: Evolving Concepts

Left ventricular non-compaction (LVNC) is a rare heart muscle disease defined by the presence of prominent left ventricular trabeculation, deep intertrabecular recesses, and a thin compact layer. Several hypotheses have been proposed regarding its pathogenesis, with the most recently accepted one being that compact layer and trabeculated layers develop independently according to an “allometric growth”. The current gold-standard diagnostic criteria (in particular, the Petersen index non-compaction/compaction ratio > 2.3) reflect an excess of myocardial trabeculation, which is not a specific morpho-functional feature of LVNC cardiomyopathy but merely a “phenotypic trait”, even described in association with other myocardial disease and over-loading conditions. Accordingly, the European Society of Cardiology (ESC) guidelines have definitively abolished the term ‘LVNC cardiomyopathy’. Recently, evolving perspectives led to the restoration of LVNC cardiomyopathy by distinguishing “hypertrabeculation phenotype” and “non-compaction phenotype”. It has been proposed that the disease-specific pathophysiologic mechanism is a congenitally underdevelopment of the compact layer accounting for an impairment of the left ventricular systolic function. Future prospective research should focus on the clinical and prognostic relevance of compact layer thinning rather than excessive trabeculation, which could significantly influence the management of patients with LVNC. The review aims to update current knowledge on the pathogenesis, genetics, and diagnostic criteria of LVNC, offering modern insights for future perspectives.

Lack of Bridge to Recovery in Pediatric Dilated Cardiomyopathy With Left Ventricular Noncompaction

BackgroundThis study assessed the possibility of a bridge to recovery using the Berlin Heart EXCOR and the histologic characteristics of pediatric patients with dilated cardiomyopathy accompanied by a left ventricular noncompaction phenotype. MethodsOf the 17 pediatric patients with dilated cardiomyopathy who underwent Berlin Heart EXCOR implantation between 2013 and 2020, 6 were diagnosed with left ventricular noncompaction association. The patients were classified into 2 groups: the dilated cardiomyopathy group and dilated cardiomyopathy with the left ventricular noncompaction phenotype group. The histologic characteristics of the left ventricular myocardium and left ventricular function after Berlin Heart EXCOR implantation were compared. ResultsCardiac recovery was not observed in the dilated cardiomyopathy with left ventricular noncompaction group. In contrast, 6 patients (55%) in the dilated cardiomyopathy group achieved cardiac recovery, and the Berlin Heart EXCOR was explanted. The degree of myocardial fibrosis was significantly higher in the dilated cardiomyopathy with the left ventricular noncompaction phenotype group than in the dilated cardiomyopathy group (P < .05). The final follow-up left ventricular ejection fraction and end-diastolic diameter during Berlin Heart EXCOR support improved significantly compared with the preimplantation variables in the dilated cardiomyopathy group (both P < .001); the dilated cardiomyopathy with left ventricular noncompaction phenotype group showed no improvements (P = .84 and P = .37, respectively). ConclusionsThe left ventricular noncompaction phenotype associated with dilated cardiomyopathy may adversely affect the rate of cardiac recovery with Berlin Heart EXCOR.

Genetic, clinical and imaging implications of a noncompaction phenotype population with preserved ejection fraction.

The genotype of symptomatic left ventricular noncompaction phenotype (LVNC) subjects with preserved left ventricular ejection fraction (LVEF) and its effect on clinical presentation are less well studied. We aimed to characterize the genetic, cardiac magnetic resonance (CMR) and clinical background, and genotype-phenotype relationship in LVNC with preserved LVEF. We included 54 symptomatic LVNC individuals (LVEF: 65 ± 5%) whose samples were analyzed with a 174-gene next-generation sequencing panel and 54 control (C) subjects. The results were evaluated using the criteria of the American College of Medical Genetics and Genomics. Medical data suggesting a higher risk of cardiovascular complications were considered "red flags". Of the LVNC population, 24% carried pathogenic or likely pathogenic (P) mutations; 56% carried variants of uncertain significance (VUS); and 20% were free from cardiomyopathy-related mutations. Regarding the CMR parameters, the LVNC and C groups differed significantly, while the three genetic subgroups were comparable. We found a significant relationship between red flags and genotype; furthermore, the number of red flags in a single subject differed significantly among the genetic subgroups (p = 0.002) and correlated with the genotype (r = 0.457, p = 0.01). In 6 out of 7 LVNC subjects diagnosed in childhood, P or VUS mutations were found. The large number of P mutations and the association between red flags and genotype underline the importance of genetic-assisted risk stratification in symptomatic LVNC with preserved LVEF.

Right ventricular global longitudinal strain is associated with cardiovascular outcome in left ventricular non-compaction phenotype

Abstract Introduction Speckle-tracking echocardiography is an increasingly important tool for assessing left ventricular non-compaction (LVNC) phenotype. This study aims to analyse right (RV) and left (LV) ventricular global longitudinal strain (GLS) in patients with LVNC and explore their association with CV outcome during long-term follow-up. Methods From our prospective LVNC cohort study, 40 patients were identified with a comprehensive echocardiographic examination including strain analysis of both ventricles. Strain was determined using TomTec ImageArena v.4.6. A combined endpoint (CV event) was defined to include: atrial flutter/fibrillation, sustained ventricular arrhythmias, cardiac syncope, thromboembolic event, heart failure progression, aborted cardiac arrest, cardiovascular death or heart transplantation. Results Over a median follow-up duration of 8 [6–10] years, 23 (58%) of the patients experienced one or more CV event (event group); while the rest (17 [42%]) did not (no event group). Baseline clinical characteristics of the two groups were comparable except for a significantly older age (P&amp;lt;0.01) and a higher BMI (P=0.033) in the event group. RVGLS (Figure 1) was significantly lower in the event group (-13.9[-17.1 – -10.3]%) compared to no-event group (-17.3[-18.8 – -15.1]%, P=0.019). While LVGLS did not show a significant difference (P=0.112), LVEF was significantly lower (P=0.011) in the event group. Other echocardiographic parameters were comparable between the groups. RVGLS &amp;gt; -14.3% (sens. 61%, spec. 88%, AUC 72%; P = 0.010) was applied as cut-off to identify patients with a higher risk of CV events during follow-up. Kaplan-Meier curves revealed a higher probability of CV events when RVGLS was &amp;gt; -14.3% (ꭓ2 = 10.28, P = 0.001; Figure 2). Univariable regression models showed that RVGLS (HR 1.10; P = 0.013), LVGLS (HR 1.23; P = 0.045), and LVEF (HR 0.95; P = 0.005) were associated with an increased risk of CV events. The association of RVGLS (OR 1.19, P = 0.047) remained independent of LV GLS and LVEF in a multivariable logistic regression analysis. When RVGLS was included to the LV function model, a significant improvement was noted (ꭓ2 from 7.31 to 11.58; ANOVA P = 0.009). Conclusions RVGLS differentiated LVNC patients suffering a CV event from those who did not and provided incremental value to the association of LV function (LVEF and LVGLS) with an increased risk of CV events. These findings highlight the potential value of RVGLS for evaluating long-term outcome during follow-up of LVNC patients.

Left ventricular early diastolic strain rate and cardiovascular outcome in patients with left ventricular non-compaction phenotype

Abstract Introduction Speckle-tracking echocardiography is an increasingly important tool for assessing left ventricular non-compaction phenotype (LVNC). This study aims to analyse left ventricular early diastolic strain rate (eSR) in LVNC and explore its association with CV outcome during long-term follow-up. Methods Fifty-nine patients meeting prespecified criteria were included from our prospective LVNC cohort. eSR was determined using TomTec ImageArena (Figure A). A combined endpoint (cardiovascular events) was defined including atrial flutter/fibrillation, sustained ventricular arrhythmias, aborted cardiac arrest, and cardiovascular mortality. Results Baseline characteristics were comparable between patients reaching the endpoint (16 [27%]) and those without (43 [73%]) except for a higher prevalence of ischemic heart disease in the former (event group: 13%; no-event group: 2%; P=0.019). In the event group, there was a non-significant tendency for a lower LVEF (38 [26–56]% vs 51 [43–56]%; P=0.091) and LVGLS (-12.3 [-16.3 to -9.7]% vs -15.2 [-17.7 to -12.8]%; P=0.111). In contrast, eSR was significantly lower in the event group (0.45 [0.30–0.65]s-1 vs 0.70 [0.39–0.93]s-1; P=0.018; Figure B). Patients with an eSR ≤ 0.70 s-1 (ROC AUC 70%; P=0.005) exhibited a lower event-free probability in Kaplan-Meier survival analysis (P=0.001; Figure C). Inclusion of eSR improved the fitness (ꭓ2) of a multivariable logistic regression model for clinical characteristics (age, gender, and NC:C ratio; Figure D), while LVEF and LVGLS did not (Table). This improvement in ꭓ2 by eSR was significant (ANOVA P=0.033), while that by LVEF or LVGLS was not (P=0.302 and 0.152, respectively). Conclusions eSR was lower in LVNC patients with events, differentiated those with events from those without, and was associated with a higher risk of events during long-term follow-up. Outcome association of eSR was independent of age, gender, and NC:C ratio and improved their event prediction. eSR has potential value for functional characterization and outcome prediction in LVNC.

Abstract P1077: Transcription Factor Nfya Regulates Mitochondrial Metabolism And Cardiomyocyte Proliferation In The Fetal Heart

We previously identified a neonatal cardiomyocyte population that enters the cell-cycle following injury and disappears as the heart loses the ability to regenerate. These regenerative neonatal cardiomyocytes display a unique transcriptional program regulated by NFYA, a subunit of the trimeric complex Nuclear Transcription Factor Y (NFY) that functions as a pioneer factor to promote cell proliferation. To study whether NFYA is required for cardiomyocyte proliferation, we generated mice with cardiomyocyte-specific deletion of NFYA using alpha-MHC-Cre. NFYA KO mice died before birth; their hearts were smaller in ventricular volumes and developed a distinct cardiac noncompaction phenotype, with hyper trabeculation and reduced cardiomyocyte proliferation. Integration of single-nuclear RNA and ATAC sequencing with spatial transcriptomics identified different embryonic cardiomyocyte subtypes in wildtype and NFYA KO hearts, including those from atria, ventricles, trabeculae, and the conduction system. We found that NFYA deletion reduced the reservoir of immature regenerative cardiomyocytes in the fetal heart and increased the number of trabecular cardiomyocytes. Mechanistically, NFYA deletion reduced the expression of genes regulating oxidative phosphorylation metabolism. The defect in mitochondrial metabolism was further supported by decreased activity of NADH oxidation at mitochondrial membranes and reduced levels of TCA cycle metabolites in NFYA KO hearts. Using chromatin immunoprecipitation and reporter assays, we show that NFYA directly regulates the transcription of those mitochondrial metabolic genes as well as cell-cycle genes in cardiomyocytes, thus providing a transcriptional coupling between mitochondrial metabolism and cardiomyocyte proliferation. Our study identified a previously unrecognized transcriptional control mechanism of metabolic genes controlled by NFYA and highlights the importance of oxidative metabolism during fetal heart development and regeneration.

De Novo Missense Mutations in TNNC1 and TNNI3 Causing Severe Infantile Cardiomyopathy Affect Myofilament Structure and Function and Are Modulated by Troponin Targeting Agents.

Rare pediatric non-compaction and restrictive cardiomyopathy are usually associated with a rapid and severe disease progression. While the non-compaction phenotype is characterized by structural defects and is correlated with systolic dysfunction, the restrictive phenotype exhibits diastolic dysfunction. The molecular mechanisms are poorly understood. Target genes encode among others, the cardiac troponin subunits forming the main regulatory protein complex of the thin filament for muscle contraction. Here, we compare the molecular effects of two infantile de novo point mutations in TNNC1 (p.cTnC-G34S) and TNNI3 (p.cTnI-D127Y) leading to severe non-compaction and restrictive phenotypes, respectively. We used skinned cardiomyocytes, skinned fibers, and reconstituted thin filaments to measure the impact of the mutations on contractile function. We investigated the interaction of these troponin variants with actin and their inter-subunit interactions, as well as the structural integrity of reconstituted thin filaments. Both mutations exhibited similar functional and structural impairments, though the patients developed different phenotypes. Furthermore, the protein quality control system was affected, as shown for TnC-G34S using patient’s myocardial tissue samples. The two troponin targeting agents levosimendan and green tea extract (-)-epigallocatechin-3-gallate (EGCg) stabilized the structural integrity of reconstituted thin filaments and ameliorated contractile function in vitro in some, but not all, aspects to a similar degree for both mutations.

Left ventricular characteristics of noncompaction phenotype patients with good ejection fraction measured with cardiac magnetic resonance.

We describe left ventricular (LV) volumes, myocardial and trabeculated muscle mass and strains with Cardiac magnetic resonance of a large cohort (n=81) who fulfilled the morphologic criteria of left ventricular noncompaction (LVNC) and had good ejection fraction (EF >55%) and compare them with healthy controls (n=81). Male and female patients were compared to matched controls and to each other. We also investigated the LV trabeculated muscle mass cutoff in male and female patients with LVNC. 81 participants with LVNC and 81 healthy controls were included. Male and female patients were compared to matched controls and to each other. We also investigated the left ventricular trabeculated muscle mass cut-off in male and female LVNC patients. The LV parameters of the LVNC population were normal, but they had significantly higher volumes, myocardial and trabeculated muscle mass, and a significantly smaller EF than the controls. Similar differences were observed after stratifying by sex. The optimal LV trabeculated muscle mass cutoffs were 25.8 g/m2 in men (area under the curve: 0.81) and 19.0 g/m2 in women (area under the curve: 0.87). The patients had normal global strains but a significantly worse global circumferential strain (patients vs controls: -29.9±4.9 vs. -35.8±4.7%, p<0.05) and significantly higher circumferential mechanical dispersion than the controls (patients vs. controls: 7.6±4.2 vs. 6.1±2.8%; p<0.05). No disease-related strain differences were noted between men and women. The LV functional and strain characteristics of the LVNC cohort differed significantly from those of healthy participants; this might be caused by increased LV trabeculation, and its clinical relevance might be questionable. The LV trabeculated muscle mass was very different between men and women; thus, the use of sex-specific morphologic diagnostic criteria should be considered.

Left ventricular mechanics and cardiovascular outcomes in non-compaction phenotype

AimsThis study aims at understanding left ventricular (LV) mechanics of non-compaction (LVNC) phenotype using echocardiographic strain analysis and at assessing the association of functional parameters with cardiovascular (CV) outcomes. Methods and resultsLongitudinal (GLS) and circumferential strain (GCS) as well as rotation of the LV were analyzed in 55 LVNC patients and 55 matched controls. Cardiovascular outcomes were documented for a median follow-up duration of 6 years. GLS and GCS were impaired in LVNC. Similary, regional longitudinal and circumferential strain as well as twist were reduced. CV events occurred in 28 LVNC patients. Apical peak circumferential strain (APCS), peak systolic rotation of apical segments (APSR), and twist were strongly associated with events. This was independent of and incremental to LVEF and non-compacted to compacted myocardial thickness ratio (NC:C ratio). The association of twist with events was also independent of and slightly superior to GLS. ConclusionsGLS, GCS, regional strain, and twist were impaired in LVNC. APCS, APSR, and twist exhibited strong association with CV events independent of and incremental to LVEF and NC:C ratio, and in case of twist even GLS. Thus, STE-derived parameters may complement the echocardiographic assessment of LVNC patients in clinical routine.

Hypertrophic cardiomyopathy, non-compaction cardiomyopathy or non-compaction phenotype - another diagnosis, other further treatment.

Hypertrophic cardiomyopathy, non-compaction cardiomyopathy or non-compaction phenotype - another diagnosis, other further treatment.

Prevalence of adverse cardiovascular events in pediatric cardiomyopathies: an analysis of 110 patients followed at a long-standing tertiary care paediatric centre

Abstract Introduction Pediatric cardiomyopathies (CMP) are disorders of the morphology and function of the heart, with a greater heterogeneity concerning etiology and clinical presentation than adult CMP. The assessment of etiology and genetic status is of paramount importance for prognosis, family screening, and therapeutic choices. Purpose To report clinical presentation, etiology, and outcome of a cohort of children diagnosed with CMP followed at tertiary care pediatric referral centre. Methods We retrospectively reviewed clinical, laboratory and imaging data of all patients referred to our cardiomyopathy centre from May 2008 to May 2019 for pediatric CMP (&amp;lt;18 years). CMP due to arrhythmic disorders, toxic agents' exposure, rheumatic conditions and maternal disease (i.e. maternal diabetes) were excluded. Primary endpoint was a composite of major adverse cardiovascular events (MACE: cardiovascular death, heart failure [HF] hospitalization, arrhythmic events, need for surgery or heart transplant referral). Results We enrolled 110 patients (65 males, age at diagnosis 67±71 months). Hypertrophic cardiomyopathy (HCM, N=48, 44%) was most frequent, followed by dilated cardiomyopathy (DCM, N=35 32%) and left ventricular non-compaction phenotype (LVNC, N=12, 11%). Mixed phenotype (N=7, 6%) and restrictive cardiomyopathy (RCM, N=3, 3%) were less common. No cases of arrhythmogenic right ventricular cardiomyopathy (ARVC) were detected. Five genotype-positive patients presented with negative clinical phenotype. A diagnosis was confirmed in all patients; the most common was sarcomere disease (30%, N=33) followed by metabolic (28%,N=31) disease, genetic syndromes (11%, N=12), neuromuscular (7,3%, N=8) diseases, and post-myocarditis cases (4,5%,N=5). Twenty-one patients (19%) were identified as idiopathic. At referral, 4,5% of children presented with NYHA class III/IV. At 35 [14–72] months, 4 (3.7%) patients required ICD implantation, 8 (7.4%) underwent cardiac surgery, and 1 (1%) underwent heart transplant. Furthermore, 28 (26%) patients required hospitalization due to acute HF, with DCM patients being at higher risk (p&amp;lt;0.01), 7 (6.8%) experienced arrhythmic events and 4 (3.9%) had syncope. Overall, 13 (12%) died (7 with metabolic disorders, 3 with genetic syndromes, 1 with a sarcomeric mutation, 1 post myocarditis, and 1 idiopathic). Conclusions In our cohort, HCM was the most common cause of pediatric CMP followed by DCM and non-compaction. MACE were present in 41% of patients. While HCM had a less severe phenotype (characterized by a higher arrhythmic burden), DCM was characterized by a higher prevalence of HF hospitalizations. DCM, inborn errors in metabolism and genetic syndromes had the worst outcome in terms mortality and heart failure long term. Widespread availability of genetic testing provides several benefits to the clinician, confirming diagnosis in ambiguous cases and defining etiology in order to guide management and identifying relatives at risk. Figure 1 Funding Acknowledgement Type of funding source: None

A rare HCN4 variant with combined sinus bradycardia, left atrial dilatation, and hypertrabeculation/left ventricular noncompaction phenotype

Introduction and objectivesHCN4 variants have been reported to cause combined sick sinus syndrome (SSS) and left ventricular noncompaction (LVNC) cardiomyopathy. This relationship has been proven in few cases and no previous patients have associated left atrial dilatation (LAD). Our objective was to study a familial disorder characterized by SSS, LAD, and hypertrabeculation/LVNC and to identify the underlying genetic and electrophysiological characteristics. MethodsA family with SSS and LVNC underwent a clinical, genetic, and electrophysiological assessment. They were studied via electrocardiography, Holter recording, echocardiography, and exercise stress tests; cardiac magnetic resonance imaging was additionally performed in affected individuals. Genetic testing was undertaken with targeted next-generation sequencing, as well as a functional study of the candidate variant in Chinese hamster ovary cells. ResultsTwelve members of the family had sinus bradycardia, associated with complete criteria of LVNC in 4 members and hypertrabeculation in 6 others, as well as LAD in 9 members. A HCN4 c.1123C>T;(p.R375C) variant was present in heterozygosis in all affected patients and absent in unaffected individuals. Electrophysiological analyses showed that the amplitude and densities of the HCN4 currents (IHCN4) generated by mutant p.R375C HCN4 channels were significantly lower than those generated by wild-type channels. ConclusionsThe combined phenotype of SSS, LAD, and LVNC is associated with the heritable HCN4 c.1123C>T;(p.R375C) variant. HCN4 variants should be included in the genetic diagnosis of LVNC cardiomyopathy and of patients with familial forms of SSS, as well as of individuals with sinus bradycardia and LAD.

Prevalence and significance of isolated left ventricular non-compaction phenotype in normal black Africans using echocardiography

BackgroundSeveral large, prospective screening studies of predominantly Caucasian patients have suggested that hypertrabeculation may not necessarily be pathologic unless there is concomitant left ventricular (LV) dysfunction, LV dilatation, history of arrhythmia, family history, or characteristic gene mutations. This conundrum may be magnified in blacks, in whom hypertrabeculation and LV hypertrophy is more common. We therefore investigated the frequency of hypertrabeculation/isolated LV noncompaction (ILVNC) phenotype in normal black Africans and evaluated LV function using sensitive measures of deformation and twist.MethodsTwo hundred and fifty-three volunteers were recruited and evaluated according to strict inclusion and exclusion criteria. Their mean age was 36.3 ± 12.2 years.ResultsTrabeculations were found in 12 (4.74%) participants. Three (1.2%) subjects had ≥ 4 LV trabeculations. The LV apex was the most common anatomical site for the location of trabeculations. Subjects with trabeculations were more likely to be males of a younger age, and had greater LV end-diastolic and end-systolic parameters and lateral e’. However, 0.8% of the population fulfilled the Stollberger criteria, and none fulfilled the Jenni, Milwaukee, or Baragwanath criteria. All subjects in this study had normal rotation patterns with no differences in rotational parameters or net twist.ConclusionsTrabeculations may be found as a normal variant in black Africans. Assessing trabeculations alone may infer ILVNC; however, utilizing the more comprehensive ILVNC criteria enables differentiation of a possible LVNC phenotype. Normal individuals with hypertrabeculation have normal LV function and normal rotation patterns, with no differences in rotational parameters or net twist.

Noncompaction Phenotype, But What is Cause and is the Diagnosis Correct?

Noncompaction Phenotype, But What is Cause and is the Diagnosis Correct?

Extracellular Matrix Disparities in an Nkx2-5 Mutant Mouse Model of Congenital Heart Disease.

Congenital heart disease (CHD) affects almost one percent of all live births. Despite diagnostic and surgical reparative advances, the causes and mechanisms of CHD are still primarily unknown. The extracellular matrix plays a large role in cell communication, function, and differentiation, and therefore likely plays a role in disease development and pathophysiology. Cell adhesion and gap junction proteins, such as integrins and connexins, are also essential to cellular communication and behavior, and could interact directly (integrins) or indirectly (connexins) with the extracellular matrix. In this work, we explore disparities in the expression and spatial patterning of extracellular matrix, adhesion, and gap junction proteins between wild type and Nkx2-5+/R52G mutant mice. Decellularization and proteomic analysis, Western blotting, histology, immunostaining, and mechanical assessment of embryonic and neonatal wild type and Nkx2-5 mutant mouse hearts were performed. An increased abundance of collagen IV, fibronectin, and integrin β-1 was found in Nkx2-5 mutant neonatal mouse hearts, as well as increased expression of connexin 43 in embryonic mutant hearts. Furthermore, a ventricular noncompaction phenotype was observed in both embryonic and neonatal mutant hearts, as well as spatial disorganization of ECM proteins collagen IV and laminin in mutant hearts. Characterizing such properties in a mutant mouse model provides valuable information that can be applied to better understanding the mechanisms of congenital heart disease.

Bridging the gap between hypertrabeculation phenotype, noncompaction phenotype and left ventricular noncompaction cardiomyopathy.

Left ventricular noncompaction (LVNC) is an increasingly recognised cardiomyopathy characterised by excessive trabeculation and deep intertrabecular recesses in direct communication with the left ventricular cavity. In LVNC, hypertrabeculation has been associated with heart failure, ventricular arrhythmia, and systemic thromboembolism. However, hypertrabeculation alone is not sufficient to define a subject as at risk for such complications and thus should not be sufficient to diagnose LVNC. Despite several studies having investigated parameters to predict adverse cardiovascular events, physicians have no effective tools to differentiate between clinically silent hypertrabeculation and LVNC. The aim of this paper was to review literature on LVNC diagnostic criteria and to provide an easy and accessible diagnostic algorithm to distinguish between hypertrabeculation phenotype, non-compaction phenotype and LVNC cardiomyopathy.

Semaphorin 3E/PlexinD1 signaling is required for cardiac ventricular compaction.

Left ventricular noncompaction (LVNC) is one of the most common forms of genetic cardiomyopathy characterized by excessive trabeculation and impaired myocardial compaction during fetal development. Patients with LVNC are at higher risk of developing left/right ventricular failure or both. Although the key regulators for cardiac chamber development are well studied, the role of semaphorin (Sema)/plexin signaling in this process remains poorly understood. In this article, we demonstrate that genetic deletion of Plxnd1, a class-3 Sema receptor in endothelial cells, leads to severe cardiac chamber defects. They were characterized by excessive trabeculation and noncompaction similar to patients with LVNC. Loss of Plxnd1 results in decreased expression of extracellular matrix proteolytic genes, leading to excessive deposition of cardiac jelly. We demonstrate that Plxnd1 deficiency is associated with an increase in Notch1 expression and its downstream target genes. In addition, inhibition of the Notch signaling pathway partially rescues the excessive trabeculation and noncompaction phenotype present in Plxnd1 mutants. Furthermore, we demonstrate that Semaphorin 3E (Sema3E), one of PlexinD1's known ligands, is expressed in the developing heart and is required for myocardial compaction. Collectively, our study uncovers what we believe to be a previously undescribed role of the Sema3E/PlexinD1 signaling pathway in myocardial trabeculation and the compaction process.

Abstract 633: Semaphorin3e-Plexind1 Signaling is Required for Cardiac Ventricular Compaction

Left ventricular noncompaction (LVNC) is one of the most common forms of genetic cardiomyopathy characterized by excessive trabeculation and impaired myocardial compaction during fetal development. LVNC patients are at higher risk to develop left or right ventricular failure, or both. While key regulators for cardiac chamber development are well studied, the role of Semaphorin-Plexin signaling in this process remains poorly understood. Here, we demonstrate that genetic deletion of Plxnd1, a class 3 semaphorin receptor in endothelial cells, leads to severe cardiac chamber defects, as characterized by excessive trabeculation and non-compaction similar to LVNC patients. Loss of Plxnd1 results in decreased expression of extracellular matrix (ECM) proteolytic genes leading to excessive deposition of cardiac jelly. We demonstrate that Plxnd1 deficiency is associated with an increase in the expression of Notch and its downstream target genes. In addition, inhibition of Notch signaling pathway can partially rescue the excessive trabeculation and non-compaction phenotype present in Plxnd1 mutants. Furthermore, we demonstrate that Semaphorin 3e (Sema3e), one of Plxnd1’s ligands is expressed in the developing heart and is required for myocardial compaction. Collectively, our results demonstrate that the Sema3e-Plxnd1 pathway is essential for myocardial trabeculation and compaction.