Novel Gene Locus for Autosomal Dominant Left Ventricular Noncompaction Maps to Chromosome 11p15

A novel gene-trap line reveals the dynamic patterns and essential roles of cysteine and glycine-rich protein 3 in zebrafish heart development and regeneration

Mutations in cysteine and glycine-rich protein 3 (CSRP3)/muscle LIM protein (MLP), a key regulator of striated muscle function, have been linked to hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM) in patients. However, the roles of CSRP3 in heart development and regeneration are not completely understood. In this study, we characterized a novel zebrafish gene-trap line, gSAIzGFFM218A, which harbors an insertion in the csrp3 genomic locus, heterozygous fish served as a csrp3 expression reporter line and homozygous fish served as a csrp3 mutant line. We discovered that csrp3 is specifically expressed in larval ventricular cardiomyocytes (CMs) and that csrp3 deficiency leads to excessive trabeculation, a common feature of CSRP3-related HCM and DCM. We further revealed that csrp3 expression increased in response to different cardiac injuries and was regulated by several signaling pathways vital for heart regeneration. Csrp3 deficiency impeded zebrafish heart regeneration by impairing CM dedifferentiation, hindering sarcomere reassembly, and reducing CM proliferation while aggravating apoptosis. Csrp3 overexpression promoted CM proliferation after injury and ameliorated the impairment of ventricle regeneration caused by pharmacological inhibition of multiple signaling pathways. Our study highlights the critical role of Csrp3 in both zebrafish heart development and regeneration, and provides a valuable animal model for further functional exploration that will shed light on the molecular pathogenesis of CSRP3-related human cardiac diseases.

Left Ventricular Noncompaction in Children: The Role of Genetics, Morphology, and Function for Outcome

Left ventricular noncompaction (LVNC) is a ventricular wall anomaly morphologically characterized by numerous, excessively prominent trabeculations and deep intertrabecular recesses. Accumulating data now suggest that LVNC is a distinct phenotype but must not constitute a pathological phenotype. Some individuals fulfill the morphologic criteria of LVNC and are without clinical manifestations. Most importantly, morphologic criteria for LVNC are insufficient to diagnose patients with an associated cardiomyopathy (CMP). Genetic testing has become relevant to establish a diagnosis associated with CMP, congenital heart disease, neuromuscular disease, inborn error of metabolism, or syndromic disorder. Genetic factors play a more decisive role in children than in adults and severe courses of LVNC tend to occur in childhood. We reviewed the current literature and highlight the difficulties in establishing the correct diagnosis for children with LVNC. Novel insights show that the interplay of genetics, morphology, and function determine the outcome in pediatric LVNC.

Left Ventricular Noncompaction Detected by Cardiac Magnetic Resonance Screening: A Reexamination of Diagnostic Criteria

In a previous cross-sectional screening study of 5,169 middle and high school students (mean age, 13.1 ± 1.78 yr) in which we estimated the prevalence of high-risk cardiovascular conditions associated with sudden cardiac death, we incidentally detected by cardiac magnetic resonance (CMR) 959 cases (18.6%) of left ventricular noncompaction (LVNC) that met the Petersen diagnostic criterion (noncompaction:compaction ratio >2.3). Short-axis CMR images were available for 511 of these cases (the Short-Axis Study Set). To determine how many of those cases were truly abnormal, we analyzed the short-axis images in terms of LV structural and functional variables and applied 3 published diagnostic criteria besides the Petersen criterion to our findings. The estimated prevalences were 17.5% based on trabeculated LV mass (Jacquier criterion), 7.4% based on trabeculated LV volume (Choi criterion), and 1.3% based on trabeculated LV mass and distribution (Grothoff criterion). Absent longitudinal clinical outcomes data or accepted diagnostic standards, our analysis of the screening data from the Short-Axis Study Set did not definitively differentiate normal from pathologic cases. However, it does suggest that many of the cases might be normal anatomic variants. It also suggests that cases marked by pathologically excessive LV trabeculation, even if asymptomatic, might involve unsustainable physiologic disadvantages that increase the risk of LV dysfunction, pathologic remodeling, arrhythmias, or mural thrombi. These disadvantages may escape detection, particularly in children developing from prepubescence through adolescence. Longitudinal follow-up of suspected LVNC cases to ascertain their natural history and clinical outcome is warranted.

Noncompaction cardiomyopathy is caused by a novel in-frame desmin (DES) deletion mutation within the 1A coiled-coil rod segment leading to a severe filament assembly defect

Mutations in DES, encoding desmin protein, are associated with different kinds of skeletal and/or cardiac myopathies. However, it is unknown, whether DES mutations are associated with left ventricular hypertrabeculation (LVHT). Here, we performed a clinical examination and subsequent genetic analysis in a family, with two individuals presenting LVHT with conduction disease and skeletal myopathy. The genetic analysis revealed a novel small in-frame deletion within the DES gene, p.Q113_L115del, affecting the α-helical rod domain. Immunohistochemistry analysis of explanted myocardial tissue from the index patient revealed an abnormal cytoplasmic accumulation of desmin and a degraded sarcomeric structure. Cell transfection experiments with wild-type and mutant desmin verified the cytoplasmic aggregation and accumulation of mutant desmin. Cotransfection experiments were performed to model the heterozygous state of the patients and revealed a dominant negative effect of the mutant desmin on filament assembly. DES:p.Q113_L115del is classified as a pathogenic mutation associated with dilated cardiomyopathy with prominent LVHT.

Translating emerging molecular genetic insights into clinical practice in inherited cardiomyopathies

Cardiomyopathies are primarily genetic disorders of the myocardium associated with higher risk of life-threatening cardiac arrhythmias, heart failure, and sudden cardiac death. The evolving knowledge in genomic medicine during the last decade has reshaped our understanding of cardiomyopathies as diseases of multifactorial nature and complex pathophysiology. Genetic testing in cardiomyopathies has subsequently grown from primarily a research tool into an essential clinical evaluation piece with important clinical implications for patients and their families. The purpose of this review is to provide with a contemporary insight into the implications of genetic testing in diagnosis, therapy, and prognosis of patients with inherited cardiomyopathies. Here, we summarize the contemporary knowledge on genotype-phenotype correlations in inherited cardiomyopathies and highlight the recent significant achievements in the field of translational cardiovascular genetics.

Sudden cardiac death in isolated right ventricular hypertrabeculation/noncompaction cardiomyopathy

Hypertrabeculation/noncompaction of the myocardium is a rare disorder that involves most commonly the left ventricle of the heart and it has been recognized as a distinct cardiomyopathy by the World Health Organization. However, it is extremely rare for this condition to involve exclusively the right ventricle. We report the cases of three patients who presented with ventricular tachyarrhythmia and sudden cardiac death. They were found to have isolated right ventricular hypertrabeculation/noncompaction on echocardiography. This supports the hypothesis that this condition is highly arrhythmogenic and is associated with high mortality similarly to the left ventricular hypertrabeculation/noncompaction cardiomyopathy.

Left Ventricular Noncompaction: A Distinct Genetic Cardiomyopathy?

Left ventricular noncompaction (LVNC) describes a ventricular wall anatomy characterized by prominent left ventricular (LV) trabeculae, a thin compacted layer, and deep intertrabecular recesses. Individual variability is extreme, and trabeculae represent a sort of individual "cardioprinting." By itself, the diagnosis of LVNC does not coincide with that of a "cardiomyopathy" because it can be observed in healthy subjects with normal LV size and function, and it can be acquired and is reversible. Rarely, LVNC is intrinsically part of a cardiomyopathy; the paradigmatic examples are infantile tafazzinopathies. When associated with LV dilation and dysfunction, hypertrophy, or congenital heart disease, the genetic cause may overlap. The prevalence of LVNC in healthy athletes, its possible reversibility, and increasing diagnosis in healthy subjects suggests cautious use of the term LVNC cardiomyopathy, which describes the morphology but not the functional profile of the cardiomyopathy.

The role of mutations in the SCN5A gene in cardiomyopathies

The SCN5A gene encodes the alpha-subunit of the Nav1.5 ion channel protein, which is responsible for the sodium inward current (INa). Since 1995 several hundred mutations in this gene have been found to be causative for inherited arrhythmias including Long QT syndrome, Brugada syndrome, cardiac conduction disease, sudden infant death syndrome, etc. As expected these syndromes are primarily electrical heart diseases leading to life-threatening arrhythmias with an "apparently normal heart". In 2003 a new form of dilated cardiomyopathy was identified associated with mutations in the SCN5A gene. Recently mutations have been also found in patients with arrhythmogenic right ventricular cardiomyopathy and atrial standstill. The purpose of this review is to outline and analyze the following four topics: 1) SCN5A genetic variants linked to different cardiomyopathies; 2) clinical manifestations of the known mutations; 3) possible molecular mechanisms of myocardial remodeling; and 4) the potential implications of gene-specific treatment for those disorders. This article is part of a Special Issue entitled: Cardiomyocyte Biology: Integration of Developmental and Environmental Cues in the Heart edited by Marcus Schaub and Hughes Abriel.

Left Ventricular Noncompaction Diagnosis and Management Relevant to Pre-participation Screening of Athletes

Left ventricular noncompaction (LVNC) has been extensively studied over the last years, and an increasing number of cases have been reported worldwide, with a large proportion comprising young and asymptomatic subjects, including athletes. The current epidemic of LVNC is likely the consequence of several causes, that is, the increased awareness of the disease and the refined cardiovascular imaging techniques. The current diagnostic methods, based uniquely on definition of morphologic findings, do not always resolve the overlap of a physiological myocardial architecture comprising a prominent trabecular pattern from a mild phenotypic expression of the real disease. Appropriate criteria for identification and management of LVNC in athletes have, therefore, become a novel challenge for cardiologists and sport physicians, who are required to solve the question of diagnosis and appropriate management in the setting of pre-participation cardiovascular screening. Indeed, although it is important to timely identify a true myocardial disease, to reduce the burden of adverse cardiac event in a young athlete, in contrast, a misdiagnosis of LVNC may lead to unwarranted restriction of the athlete lifestyle, with detrimental psychological, social, and economic consequences. This review report has been planned, therefore, to help physicians in diagnosing and managing athletes presenting with a morphologic pattern suggestive of LVNC with specific focus on criteria for advising sport participation.

A novel association of biventricular cardiac noncompaction and diabetic embryopathy: case report and review of the literature

Diabetic embryopathy refers to a constellation of congenital malformations arising in the setting of poorly controlled maternal diabetes mellitus. Cardiac abnormalities are the most frequently observed findings, with a 5-fold risk over normal pregnancies. Although a diverse spectrum of cardiac defects has been documented, cardiac noncompaction morphology has not been associated with this syndrome. In this report, we describe a novel case of biventricular cardiac noncompaction in a neonate of a diabetic mother. The patient was a late preterm female with right anotia, caudal dysgenesis, multiple cardiac septal and aortic arch defects, and biventricular cardiac noncompaction. Examination of both ventricles demonstrated spongy myocardium with increased myocardial trabeculation greater than 50% left ventricular thickness and greater than 75% right ventricular thickness, with hypoplasia of the bilateral papillary muscles, consistent with noncompaction morphology. Review of the literature highlights the importance of gene expression and epigenomic regulation in cardiac embryogenesis.

Left ventricular noncompaction cardiomyopathy: updated review

The first case of noncompaction was described in 1932 after an autopsy performed on a newborn infant with aortic atresia/coronary-ventricular fistula. Isolated noncompaction cardiomyopathy was first described in 1984. A review on selected/relevant medical literature was conducted using Pubmed from 1984 to 2013 and the pathogenesis, clinical features, and management are discussed. Left ventricular noncompaction (LVNC) is a relatively rare congenital condition that results from arrest of the normal compaction process of the myocardium during fetal development. LVNC shows variability in its genetic pattern, pathophysiologic findings, and clinical presentations. The genetic heterogeneity, phenotypical overlap, and variety in clinical presentation raised the suspicion that LVNC might just be a morphological variant of other cardiomyopathies, but the American Heart Association classifies LVNC as a primary genetic cardiomyopathy. The familiar type is common and follows a X-linked, autosomal-dominant, or mitochondrial-inheritance pattern (in children). LVNC can occur in isolation or coexist with other cardiac and/or systemic anomalies. The clinical presentations are variable ranging from asymptomatic patients to patients who develop ventricular arrhythmias, thromboembolism, heart failure, and sudden cardiac death. Increased awareness over the last 25 years and improvements in technology have increased the identification of this illness and improved the clinical outcome and prognosis. LVNC is commonly diagnosed by echocardiography. Other useful diagnostic techniques for LVNC include cardiac magnetic resonance imaging, computerized tomography, and left ventriculography. Management is symptom based and patients with symptoms have a poorer prognosis. LVNC is a genetically heterogeneous disorder which can be associated with other anomalies. Making the correct diagnosis is important because of the possible associations and the need for long-term management and screening of living relatives.

Pediatric cardiomyopathies: causes, epidemiology, clinical course, preventive strategies and therapies

Pediatric cardiomyopathies, which are rare but serious disorders of the muscles of the heart, affect at least one in every 100,000 children in the USA. Approximately 40% of children with symptomatic cardiomyopathy undergo heart transplantation or die from cardiac complications within 2 years. However, a significant number of children suffering from cardiomyopathy are surviving into adulthood, making it an important chronic illness for both pediatric and adult clinicians to understand. The natural history, risk factors, prevalence and incidence of this pediatric condition were not fully understood before the 1990s. Questions regarding optimal diagnostic, prognostic and treatment methods remain. Children require long-term follow-up into adulthood in order to identify the factors associated with best clinical practice including diagnostic approaches, as well as optimal treatment approaches. In this article, we comprehensively review current research on various presentations of this disease, along with current knowledge about their causes, treatments and clinical outcomes.

[A familial form of ventricular non compaction in a mother and two of his sons in St. Louis, Senegal]

We report a familial form of ventricular non compaction in a mother and two of her sons. It was a young man of 25 years who presented with NYHA stage III dyspnea and a cough with bloody sputum. The clinical examination found left ventricular failure. The echocardiogram done showed left ventricular dilatation with large trabeculae separated by deep intertrabecular recesses in both ventricles suggestive of a non-biventricular compaction. It was possible to note from the family screening by echocardiography of the mother and half-brother a left ventricular non compaction while they were asymptomatic. Thus we concluded a familial form of ventricular non-compaction. This is the first familial case described in Senegal.

Noncompaction of the ventricular myocardium and hydrops fetalis in cobalamin C disease

Cobalamin C disease (cblC), a form of combined methylmalonic acidemia and hyperhomocysteinemia caused by mutations in the MMACHC gene, may be the most common inborn error of intracellular cobalamin metabolism. The clinical manifestations of cblC disease are diverse and range from intrauterine growth retardation to adult onset neurological disease. The occurrence of structural heart defects appears to be increased in cblC patients and may be related to the function of the MMACHC enzyme during cardiac embryogenesis, a concept supported by the observation that Mmachc is expressed in the bulbis cordis of the developing mouse heart. Here we report an infant who presented with hydrops fetalis, ventricular dysfunction, and echocardiographic evidence of LVNC, a rare congenital cardiomyopathy. Metabolic evaluations, complementation studies, and mutation analysis confirmed the diagnosis of cblC disease. These findings highlight an intrauterine cardiac phenotype that can be displayed in cblC disease in association with nonimmune hydrops.

[Isolated noncompaction cardiomyopathy with special emphasis on arrhythmia complications]

Isolated noncompaction cardiomyopathy (NCCM) is a rare genetically determined myocardial disease caused by abnormal fetal development of the myocardium resulting in a thin compacted and a thicker noncompacted layer of the affected left ventricular (LV) wall. The genetic basis of NCCM is heterogenous. Diagnosis can be made using echocardiography or magnetic resonance imaging. The diagnostic criteria for NCCM are still under discussion. Afflicted patients may present with various symptoms caused by arrhythmias, heart failure and cardioembolic events. Severely reduced LV function as well as left bundle branch block and atrial fibrillation were shown to be linked to worse outcomes. Treatment in patients with NCCM should be targeted at individual symptoms and clinical findings. Therapy includes pharmacological treatment, and in individual cases ablation or device therapy, as well as consideration for heart transplantation in selected cases. Aside from regular clinical follow-up of patients with NCCM screening of first degree family members with assessment of medical history, physical examination, ECG recording, and echocardiography are recommended.

Malonyl coenzyme A decarboxylase deficiency: early dietary restriction and time course of cardiomyopathy

Malonyl coenzyme A (CoA) decarboxylase (MCD) deficiency is a rare autosomal recessive organic acidemia characterized by varying degrees of organ involvement and severity. MCD regulates fatty acid biosynthesis and converts malonyl-CoA to acetyl-CoA. Cardiomyopathy is 1 of the leading causes of morbidity and mortality in this disorder. It is unknown if diet alone prevents cardiomyopathy development based in published literature. We report a 10-month-old infant girl identified by newborn screening and confirmed MCD deficiency with a novel homozygous MLYCD mutation. She had normal echocardiogram measurements before transition to high medium-chain triglycerides and low long-chain triglycerides diet. Left ventricular noncompaction development was not prevented by dietary interventions. Further restriction of long-chain triglycerides and medium-chain triglycerides supplementation in combination with angiotensin-converting enzyme inhibitors helped to improve echocardiogram findings. Patient remained asymptomatic, with normal development and growth. Our case emphasizes the need for ongoing cardiac disease screening in patients with MCD deficiency and the benefits and limitations of current dietary interventions.

Value of cardiovascular MR in diagnosing left ventricular non-compaction cardiomyopathy and in discriminating between other cardiomyopathies

Objectives

To analyse the value of cardiovascular magnetic resonance (CMR)-derived myocardial parameters to differentiate left ventricular non-compaction cardiomyopathy (LVNC) from other cardiomyopathies and controls.

Methods

We retrospectively analysed 12 patients with LVNC, 11 with dilated and 10 with hypertrophic cardiomyopathy and compared them to 24 controls. LVNC patients had to fulfil standard echocardiographic criteria as well as additional clinical and imaging criteria. Cine steady-state free precession and late gadolinium enhancement (LGE) imaging was performed. The total LV myocardial mass index (LV-MMI), compacted (LV-MMI_compacted), non-compacted (LV-MMI_{non-compacted}), percentage LV-MM_{non-compacted}, ventricular volumes and function were calculated. Data were compared using analysis of variance and Dunnett’s test. Additionally, semi-quantitative segmental analyses of the occurrence of increased trabeculation were performed.

Results

Total LV-MMI_{non-compacted} and percentage LV-MM_{non-compacted} were discriminators between patients with LVCN, healthy controls and those with other cardiomyopathies with cut-offs of 15 g/m² and 25 %, respectively. Furthermore, trabeculation in basal segments and a ratio of non-compacted/compacted myocardium of ≥3:1 were criteria for LVNC. A combination of these criteria provided sensitivities and specificities of up to 100 %. None of the LVNC patients demonstrated LGE.

Conclusions

Absolute CMR quantification of the LV-MMI_{non-compacted} or the percentage LV-MM_{non-compacted} and increased trabeculation in basal segments allows one to reliably diagnose LVNC and to differentiate it from other cardiomyopathies.

Key Points

• Cardiac magnetic resonance imaging can reliably diagnose left ventricular non-compaction cardiomyopathy.

• Differentiation of LVNC from other cardiomyopathies and normal hearts is possible.

• The best diagnostic performance can be achieved if combined MRI criteria for the diagnosis are used.

Diagnostic uncertainties and future perspectives in noncompaction cardiomyopathy

BACKGROUND

Noncompaction cardiomyopathy (NCCM) is a new pathoanatomic entity, disputably believed to result from abnormal arrest in embryonic endomyocardial morphogenesis. During almost three decades of research of NCCM, more knowledge has developed alongside diagnostic uncertainties and precise definition. In this article, we present these uncertainties and provide perspectives on how to overcome these challenges.

AREAS COVERED

The uncertainties, about NCCM regarding nomenclature, classification, pathophysiology, and limitations of the current diagnostic criteria will be reviewed. The application of newer imaging modalities will be contrasted in relation to conventional assessments. Finally, future aspirations will be outlined providing a more thoughtful appraisal toward NCCM diagnosis.

EXPERT OPINION

Our current understanding of NCCM is limited by heterogeneity of disease spectrum and phenotype-genotype overlap with other cardiac anomalies. Selection bias, small sampling, and retrospective nature limit most of published studies on NCCM. There are three main research fields related to NCCM: pathoanatomic studies, imaging studies, and genetic screening. Besides conventional echocardiography, imaging should include both structural (cardiac MRI, contrast and 3D echocardiography) and functional diagnosis using deformation imaging. These research aspects should be integrated in a collaborative international registry of nonselective populations in order to achieve better understanding and optimal diagnosis of NCCM. Moreover, it holds the promise of the detection of earlier stages of disease. A clear pathoanatomic cut-off definition of NCCM should be the initial step toward uniform imaging diagnosis.

Coffin-Lowry syndrome and left ventricular noncompaction cardiomyopathy with a restrictive pattern

Coffin-Lowry syndrome (CLS) is an X-linked dominant condition characterized by moderate to severe mental retardation, characteristic facies, and hand and skeletal malformations. The syndrome is due to mutations in the gene that encodes the ribosomal protein S6 kinase-2, a growth factor-regulating protein kinase located on Xp22.2. Cardiac anomalies are known to be associated with CLS. Left ventricular noncompaction (LVNC) is a clinically heterogeneous disorder characterized by left ventricular (LV) myocardial trabeculations and intertrabecular recesses that communicate with the LV cavity. Patients may present with a variety of clinical phenotypes, ranging from a complete absence of symptoms to a rapid, progressive decline in LV systolic and diastolic function, resulting in congestive heart failure, malignant ventricular tachyarrhythmias, and systemic thromboembolic events. Restrictive cardiomyopathy is an uncommon primary cardiomyopathy characterized by biatrial enlargement, normal or decreased biventricular volume, impaired ventricular filling, and normal or near-normal systolic function. We describe a patient with CLS and LVNC with a restrictive pattern, as documented by echocardiography and cardiac catheterization. To our knowledge, there have been no previous reports of concomitant CLS and LVNC. On the basis of our case, we suggest that patients with CLS be screened not only for congenital structural heart defects but also for LVNC cardiomyopathy.

Familial evaluation for diagnosis of arrhythmogenic right ventricular dysplasia

Most sudden cardiac deaths in young athletes are caused by previously undetected inherited cardiac diseases. Here, we report a case of a young male athlete in whom a presumptive diagnosis of hypertrophic cardiomyopathy (HCM) was made following a near sudden cardiac death. Although his imaging studies initially suggested HCM, a detailed clinical and genetic evaluation of the patient and his asymptomatic father led to the diagnosis of arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVD) in both. DNA sequencing revealed that each individual was heterozygous for two rare variants in the PKP2 and DSC2 genes, both of which were previously shown to be associated with ARVD and to encode desmosomal proteins, i.e. the previously reported splicing variant c2489 + 1A > G in the PKP2 gene and the novel p.I109M variant in the DSC2 gene. Imaging and electrophysiologic studies further supported a diagnosis of ARVD in the father. This case highlights the importance of detailed clinical evaluation and genetic testing of family members when dealing with sudden cardiac death or unexplained cardiomyopathies in the young.

Sarcomere Gene Mutations in Isolated Left Ventricular Noncompaction Cardiomyopathy Do Not Predict Clinical Phenotype

Background—

Left ventricular noncompaction of the myocardium (LVNC) has been recognized as a cardiomyopathy with a genetic etiology. Mutations in genes encoding sarcomere proteins were shown to be associated with LVNC. We evaluated the potential clinical impact of genetic analysis of sarcomere genes in patients with LVNC.

Methods and Results—

We identified 5 mutations in cardiac myosin-binding protein C ( MYBPC3 ) and 2 mutations in α-tropomyosin ( TPM1 ) in a cohort of unrelated adult probands with isolated LVNC. The mutations in MYBPC3 and TPM1 and in 6 other previously reported sarcomere genes in this cohort resulted in a total of 18 (29%) heterozygous mutations in 63 probands. β-myosin heavy chain ( MYH7 ) was the most prevalent disease gene and accounts for 13% of cases, followed by MYBPC3 (8%). Comparing sarcomere mutation-positive and mutation-negative LVNC probands showed no significant differences in terms of average age, myocardial function, and presence of heart failure or tachyarrhythmias at initial presentation or at follow-up. Familial disease was found in 16 probands of whom 8 were sarcomere mutation positive. Nonpenetrance was detected in 2 of 8 mutation-positive families with LVNC.

Conclusions—

Mutations in sarcomere genes account for a significant (29%) proportion of cases of isolated LVNC in this cohort. The distribution of disease genes confirms genetic heterogeneity and opens new perspectives in genetic testing in patients with LVNC and their relatives at high risk of inheriting the cardiomyopathy. The presence or absence of a sarcomere gene mutation in LVNC cannot be related to the clinical phenotype.

Left ventricular non-compaction revisited: a distinct phenotype with genetic heterogeneity?

Non-compaction of the left ventricular myocardium (LVNC) has gained increasing recognition during the last 25 years. There is a morphological trait of the myocardial structure with a spectrum from normal variants to the pathological phenotype of LVNC, which reflects the embryogenic structure of the human heart due to an arrest in the compaction process during the first trimester. It must be cautioned not to overdiagnose LVNC: the morphological spectrum of trabeculations, from normal variants to pathological trabeculations with the morphological feature of LVNC must be carefully considered. The classical triad of complications are heart failure, arrhythmias, including sudden cardiac death, and systemic embolic events. Non-compaction of the left ventricular myocardium can occur in isolation or in association with congenital heart defects (CHDs), genetic syndromes, and neuromuscular disorders among others. The clinical spectrum is wide and the outcome is more favourable than in previously described populations with a negative selection bias. Familial occurrence is frequent with autosomal dominant and X-linked transmissions. Different mutations in sarcomere protein genes were identified and there seems to be a shared molecular aetiology of different cardiomyopathic phenotypes, including LVNC, hypertrophic and dilated cardiomyopathies. Thus, genetic heterogeneity, with an overlap of different phenotypes, and the variability of hereditary patterns, raise the questions whether there is a morphological trait from dilated/hypertrophic cardiomyopathy to LVNC and what are the triggers and modifiers to develop either dilated, hypertrophic cardiomyopathy, or LVNC in patients with the same mutation. The variety in clinical presentation, the genetic heterogeneity, and the phenotype of the first transgenetic animal model of an LVNC-associated mutation question the hypothesis that LVNC be a distinct cardiomyopathy: it seems to be rather a distinct phenotype or phenotypic, morphological expression of different underlying diseases than a distinct cardiomyopathy.

Isolated ventricular noncompaction syndrome in a nigerian male: case report and review of the literature

Isolated ventricular non-compaction cardiomyopathy (IVNC) is a rare, morphologically distinct primary genetic cardiomyopathy, which is now gaining prominence as an important differential diagnosis in patients presenting with cardiac failure. We describe a case report of a Nigerian male with facial dysmorphism presenting with cardiac failure. This is followed by a review of the literature with focus on the diagnosis of this condition, which may be difficult especially in non-Caucasian populations.

The importance of genetic counseling, DNA diagnostics, and cardiologic family screening in left ventricular noncompaction cardiomyopathy

BACKGROUND

Left ventricular (LV) noncompaction (LVNC) is a distinct cardiomyopathy featuring a thickened bilayered LV wall consisting of a thick endocardial layer with prominent intertrabecular recesses with a thin, compact epicardial layer. Similar to hypertrophic and dilated cardiomyopathy, LVNC is genetically heterogeneous and was recently associated with mutations in sarcomere genes. To contribute to the genetic classification for LVNC, a systematic cardiological family study was performed in a cohort of 58 consecutively diagnosed and molecularly screened patients with isolated LVNC (49 adults and 9 children).

METHODS AND RESULTS

Combined molecular testing and cardiological family screening revealed that 67% of LVNC is genetic. Cardiological screening with electrocardiography and echocardiography of 194 relatives from 50 unrelated LVNC probands revealed familial cardiomyopathy in 32 families (64%), including LVNC, hypertrophic cardiomyopathy, and dilated cardiomyopathy. Sixty-three percent of the relatives newly diagnosed with cardiomyopathy were asymptomatic. Of 17 asymptomatic relatives with a mutation, 9 had noncompaction cardiomyopathy. In 8 carriers, nonpenetrance was observed. This may explain that 44% (14 of 32) of familial disease remained undetected by ascertainment of family history before cardiological family screening. The molecular screening of 17 genes identified mutations in 11 genes in 41% (23 of 56) tested probands, 35% (17 of 48) adults and 6 of 8 children. In 18 families, single mutations were transmitted in an autosomal dominant mode. Two adults and 2 children were compound or double heterozygous for 2 different mutations. One adult proband had 3 mutations. In 50% (16 of 32) of familial LVNC, the genetic defect remained inconclusive.

CONCLUSION

LVNC is predominantly a genetic cardiomyopathy with variable presentation ranging from asymptomatic to severe. Accordingly, the diagnosis of LVNC requires genetic counseling, DNA diagnostics, and cardiological family screening.

Cardiomyopathies--misdiagnosed as Sudden Infant Death Syndrome (SIDS)

Cardiomyopathies are an important and heterogenous group of diseases. With the identification of several new disease entities over the past decade, advances in diagnosis and precise causation, some disease definitions have become outdated. The past decade has witnessed a rapid evolution of molecular genetics in cardiology, e.g. myocardial diseases (Hypertrophic cardiomyopathy-HCM, Arrhythmogenic right ventricular cardiomyopathy-ARVCM) and channelopathies (Long QT syndrome-LQTS, Brugada syndrome-BrS, Catecholaminergic Polymorphic Ventricular Tachycardia-CPVT and Short QT syndrome-SQTS) as diseases predisposing to potentially lethal ventricular tachyarrhythmias. Beside the detection of mutations in several genes, histological and immunohistochemical findings can point to a cardiomyopathy as underlying disease. Therefore, previous microscopical investigations of different parts of the myocardium can help to select those cases of suspected Sudden Infant Death Syndrome (SIDS), where a search for genetic mutations can lead to a diagnosis explaining the sudden and unexpected death.

Isolated non-compaction cardiomyopathy

BACKGROUND

Isolated non-compaction cardiomyopathy (NCCM) was first described in 1984. This disorder, a primary genetic cardiomyopathy, is now attracting increased attention.

METHOD

The current state of the epidemiology, pathogenesis, pathophysiology, clinical features, diagnosis, treatment, and prognosis of NCCM are discussed on the basis of a review of selected literature as well as the authors' personal experience.

RESULTS

The pathogenesis of NCCM is thought to involve a genetically determined disturbance of the myocardial compaction process during fetal endomyocardial morphogenesis. It is not accompanied by any other cardiac anomalies. Echocardiography is the diagnostic method of choice. The diagnosis is based on the following echocardiographic criteria: the presence of at least 4 prominent trabeculations and deep intertrabecular recesses, blood flow from the ventricular cavity into the intertrabecular recesses, and a typical bilaminar structure of the affected portion of the left ventricular myocardium. NCCM can also be diagnosed with magnetic resonance imaging of the heart. The clinical severity of NCCM is variable; its manifestations include heart failure, thromboembolic events, and arrhythmias. The treatment is symptom-based. Patients with symptomatic NCCM have a poor prognosis.

CONCLUSION

NCCM is a type of cardiomyopathy that was first described 25 years ago. Its molecular genetic basis is not yet fully clear, and the same is true of its diagnosis, treatment, and prognosis. Further study of these matters is needed.

A teenager with Marfan syndrome and left ventricular noncompaction

We report a teenager with Marfan syndrome who presented to Cincinnati Children's Hospital Medical Center as part of a preoperative evaluation for an orthopedic procedure after asymptomatic arrhythmia was recognized. Continuous cardiac monitoring showed frequent premature ventricular contractions and nonsustained runs of ventricular tachycardia. Cardiac magnetic resonance imaging showed left ventricular noncompaction (LVNC), prompting insertion of an implantable cardiac defibrillator. Although Marfan syndrome is associated with cardiac lesions, it has not previously been described with LVNC. Likewise LVNC has been seen in association with other cardiac lesions; however, this report represents the first reference of LVNC in the context of Marfan syndrome.

Sudden death: ethical and legal problems of post-mortem forensic genetic testing for hereditary cardiac diseases

Hereditary non-structural diseases such as catecholaminergic polymorphic ventricular tachycardia (CPVT), long QT, and the Brugada syndrome as well as structural disease such as hypertrophic cardiomyopathy (HCM) and arrhythmogenic right ventricular cardiomyopathy (ARVC) cause a significant percentage of sudden cardiac deaths in the young. In these cases, genetic testing can be useful and does not require proxy consent if it is carried out at the request of judicial authorities as part of a forensic death investigation. Mutations in several genes are implicated in arrhythmic syndromes, including SCN5A, KCNQ1, KCNH2, RyR2, and genes causing HCM. If the victim's test is positive, this information is important for relatives who might be themselves at risk of carrying the disease-causing mutation. There is no consensus about how professionals should proceed in this context. This article discusses the ethical and legal arguments in favour of and against three options: genetic testing of the deceased victim only; counselling of relatives before testing the victim; counselling restricted to relatives of victims who tested positive for mutations of serious and preventable diseases. Legal cases are mentioned that pertain to the duty of geneticists and other physicians to warn relatives. Although the claim for a legal duty is tenuous, recent publications and guidelines suggest that geneticists and others involved in the multidisciplinary approach of sudden death (SD) cases may, nevertheless, have an ethical duty to inform relatives of SD victims. Several practical problems remain pertaining to the costs of testing, the counselling and to the need to obtain permission of judicial authorities.

Left ventricular noncompaction: a rare cause of hydrops fetalis

We present a case of isolated left ventricular noncompaction (LVNC), a severe congenital cardiomyopathy, which presented in the neonatal period as fetal hydrops. To our knowledge, this is the first child with LVNC presenting with hydrops fetalis to survive infancy. Once considered a uniformly fatal and extremely rare form of cardiomyopathy, LVNC has recently been shown to be more common than previously reported, with a varying range of clinical severity. Although long-term morbidity and mortality are not clearly known, recent work suggests better survivability than once reported.

Cardiogenetics, neurogenetics, and pathogenetics of left ventricular hypertrabeculation/noncompaction

BACKGROUND

Left ventricular hypertrabeculation (LVHT), also known as noncompaction or spongy myocardium, is a cardiac abnormality of unknown etiology and pathogenesis frequently associated with genetic cardiac and noncardiac disorders, particularly genetic neuromuscular disease. This study aimed to review the current knowledge about the genetic or pathogenetic background of LVHT.

METHODS

A literature review of all human studies dealing with the association of LVHT with genetic cardiac and noncardiac disorders, particularly neuromuscular disorders, was conducted.

RESULTS

Most frequently, LVHT is associated with mitochondrial disorders (mtDNA, nDNA mutations), Barth syndrome (G4.5, TAZ mutations), hypertrophic cardiomyopathy (MYH7, ACTC mutations), zaspopathy (ZASP/LDB3 mutations), myotonic dystrophy 1 (DMPK mutations), and dystrobrevinopathy (DTNA mutations). More rarely, LVHT is associated with mutations in the DMD, SCNA5, MYBPC3, FNLA1, PTPN11, LMNA, ZNF9, AMPD1, PMP22, TNNT2, fibrillin2, SHP2, MMACHC, LMX1B, HCCS, or NR0B1 genes. Additionally, LVHT occurs with a number of chromosomal disorders, polymorphisms, and not yet identified genes, as well in a familial context. The broad heterogeneity of LVHT's genetic background suggests that the uniform morphology of LVHT not only is attributable to embryonic noncompaction but also may result from induction of hypertrabeculation as a compensatory reaction of an impaired myocardium.

CONCLUSIONS

Most frequently, LVHT is associated with mutations in genes causing muscle or cardiac disease, or with chromosomal disorders. These associations require comprehensive cardiac, neurologic, and cytogenetic investigations.

Ventricular noncompaction in a female patient with nephropathic cystinosis: a case report

Introduction

We report an unusual and interesting case of a 24-year-old woman with nephropathic cystinosis in association with concomitant isolated noncompaction of the left ventricle. Left ventricular noncompaction usually presents with reduced exercise tolerance as a consequence of ventricular dysfunction, the result of embolus or with palpitations and syncope due to arrhythmia. There is no specific treatment directed at isolated noncompaction. Treatment is focused on the cause of presentation, with medication aimed at improving ventricular dysfunction, as well as treating and preventing thrombosis and arrhythmia.

Case presentation

Our patient presented with an episode of decompensated heart failure. Trans-thoracic echocardiography demonstrated excessive trabeculation with inter-trabecular recesses in the left ventricle typical of noncompaction of the left ventricle. The patient's admission was complicated by a cardiac arrest precipitated by ventricular tachycardia for which she subsequently underwent implantation of an automatic implantable cardioverter defibrillator.

Conclusion

This is, as far as we know, the first case report of the co-existence of nephropathic cystinosis and isolated noncompaction of the left ventricle. It highlights the importance of being vigilant to the diagnosis of left ventricular noncompaction.

Embryogenesis of the heart muscle

This article concerns the development of myocardial architecture--crucial for contractile performance of the heart and its conduction system, essential for generation and coordinated spread of electrical activity. Topics discussed include molecular determination of cardiac phenotype (contractile and conducting), remodeling of ventricular wall architecture and its blood supply, and relation of trabecular compaction to noncompaction cardiomyopathy. Illustrated are the structure and function of the tubular heart, time course of trabecular compaction, and development of multilayered spiral systems of the compact layer.

Genetic heterogeneity of left-ventricular noncompaction cardiomyopathy

Isolated noncompaction of the ventricular myocardium (INVM) sometimes referred to as spongy myocardium is a rare, congenital and also acquired cardiomyopathy. It appears to divide the presentation into neonatal, childhood and adult forms of which spongy myocardium and systolic dysfunction is the commonality. The disorder is characterized by a left ventricular hypertrophy with deep trabeculations, and with diminished systolic function, with or without associated left ventricular dilation. In half or more of the cases, the right ventricle is also affected. The sporadic type, however, in some patients, may be due to chromosomal abnormalities and the occurrence of familial incidence. Isolated noncompaction of the left ventricular myocardium in the majority of adult patients is an autosomal dominant disorder. The familial and X-linked disorders have been described by various authors. We here describe the genetic background of this disorder: some of the most mutated genes that are responsible for the disease are (G4.5 (tafazzin gene): alpha-dystrobrevin gene (DTNA); FKBP-12 gene; lamin A/C gene; Cypher/ZASP (LIM, LDB3) gene); and some genotype-phenotype correlations (Becker muscular dystrophy, Emery-Dreifuss muscular dystrophy or Barth syndrome) based on the literature review.

Diagnosing left ventricular noncompaction by echocardiography and cardiac magnetic resonance imaging and its dependency on neuromuscular disorders

BACKGROUND

Left ventricular hypertrabeculation (LVHT), also termed noncompaction LVHT, is diagnosed by echocardiography or cardiac magnetic resonance imaging (CMRI), and associated with neuromuscular disorders (NMD). The aim of this study was to assess if LVHT can be diagnosed by CMRI applying echocardiographic definitions.

METHODS AND RESULTS

The CMRI images of 19 echocardiographically diagnosed LVHT patients were re-evaluated (10 female, 14-67 y of age). Left ventricular hypertrabeculation was diagnosed by CMRI in 9 cases. Patients with CMRI-diagnosed LVHT were more often females (67% versus 40%), experienced heart failure more often (100% versus 50%), had an LV end diastolic diameter > 57 mm (67% versus 40%), had an LV fractional shortening < 25% (89% versus 40%), and had a larger extension of LVHT than patients without CMRI-diagnosed LVHT. The prevalence of NMD (87%) did not differ between both groups.

CONCLUSIONS

Echocardiographic definition for CMRI yielded the diagnosis of LVHT in only 47%. When looking for LVHT by CMRI, LV size, function, and extension of LVHT have to be considered.

Atrial parasystole in left ventricular noncompaction: a morphofunctional study by echocardiography and magnetic resonance imaging

Isolated left ventricular noncompaction is a recently recognized age-independent cardiac genetic disorder caused by heterogeneous defects in endo-myocardial morphogenesis. Transthoracic echocardiography and cardiac magnetic resonance are the most reliable techniques to make a diagnosis of the disease, noninvasively. Arrhythmic atrial and ventricular disorders have been reported in 20-50% of these patients. The morphological and functional findings are described in a young woman in whom the exclusive clinical sign of isolated ventricular noncompaction was an atrial parasystole.

Prevalence and characteristics of left ventricular noncompaction in a community hospital cohort of patients with systolic dysfunction

BACKGROUND

Left ventricular noncompaction (LVNC) is felt to be a rare form of cardiomyopathy, although its prevalence in a nonreferred population is unknown. We examined the prevalence and clinical characteristics of LVNC in a community hospital cohort of adult patients with echocardiographic evidence of left ventricular (LV) systolic dysfunction.

METHODS

All adult echocardiograms with global LV dysfunction and an LVEF < or = 45% over a 1-year period were reviewed for signs of LV noncompaction. Its presence was confirmed by the consensus of at least 2/3 readers specifically searching for this using standard criteria for noncompaction.

RESULTS

A 3.7% prevalence of definite or probable LVNC was found in those with LVEF < or = 45% and a 0.26% prevalence for all patients referred for echocardiography during this period. This is appreciably higher than prior reports from tertiary centers.

CONCLUSION

Noncompaction may not be a rare phenomenon and is comparable to other more widely recognized but less common causes of heart failure such as peripartum myopathy, connective tissue diseases, chronic substance abuse and HIV disease.

Noncompaction of the ventricular myocardium is associated with a de novo mutation in the beta-myosin heavy chain gene

Noncompaction of the ventricular myocardium (NVM) is the morphological hallmark of a rare familial or sporadic unclassified heart disease of heterogeneous origin. NVM results presumably from a congenital developmental error and has been traced back to single point mutations in various genes. The objective of this study was to determine the underlying genetic defect in a large German family suffering from NVM. Twenty four family members were clinically assessed using advanced imaging techniques. For molecular characterization, a genome-wide linkage analysis was undertaken and the disease locus was mapped to chromosome 14ptel-14q12. Subsequently, two genes of the disease interval, MYH6 and MYH7 (encoding the α- and β-myosin heavy chain, respectively) were sequenced, leading to the identification of a previously unknown de novo missense mutation, c.842G>C, in the gene MYH7. The mutation affects a highly conserved amino acid in the myosin subfragment-1 (R281T). In silico simulations suggest that the mutation R281T prevents the formation of a salt bridge between residues R281 and D325, thereby destabilizing the myosin head. The mutation was exclusively present in morphologically affected family members. A few members of the family displayed NVM in combination with other heart defects, such as dislocation of the tricuspid valve (Ebstein's anomaly, EA) and atrial septal defect (ASD). A high degree of clinical variability was observed, ranging from the absence of symptoms in childhood to cardiac death in the third decade of life. The data presented in this report provide first evidence that a mutation in a sarcomeric protein can cause noncompaction of the ventricular myocardium.

Noncompaction of the left ventricle: primary cardiomyopathy with an elusive genetic etiology

PURPOSE OF REVIEW

Noncompaction of the left ventricle is a descriptive anatomical term and recently recognized primary cardiomyopathy. Cardiac imaging now allows for prompt detection. The specific etiology remains poorly understood, however, and the major genetic determinants are unknown. This review describes recent data showing the genetic heterogeneity and overlap with other cardiomyopathies. Understanding the genetics may depend on clarifying the distinctive diagnostic features and investigating the contribution of all known cardiomyopathy-causing genes with overlapping morphology.

RECENT FINDINGS

Adding to the known genes (TAZ, DTNA, LDB3 and LMNA), recent work has identified SCN5A, MYH7 and MYBPC3 as associated loci. LDB3 may also be a genetic modifier. Case reports and linkage studies suggest additional loci at 1p36, 1q43 and 11p15. Aside from Barth syndrome, other genetic and metabolic syndromes with noncompaction have been described. Despite this, large studies have failed to identify the etiology in the majority of patients.

SUMMARY

Despite advances in detection, comprehensive clinical, pathological, genetic, and family studies are necessary to define the phenotypic overlap with other cardiomyopathies. Without a more precise understanding of its etiology, the answers to the questions regarding the clinical relevance and management of patients with noncompaction of the left ventricle will remain elusive.