Intrafamilial variability of noncompaction of the ventricular myocardium

Hypertrabeculation; a phenotype with Heterogeneous etiology

Left ventricular hypertrabeculation (LVHT) is a phenotype with multiple etiologies and variable clinical presentation and significance. It is characterized by a 2-layer myocardium with an enlarged trabecular layer and a thinner compacted layer. The prevalence has been increasing due to advances in cardiac imaging. Initial attention was focused on the congenital noncompaction syndrome, and the presence of LVHT was always attributed to this etiology. However, due to the lack of consensus diagnostic criteria, LVHT has now been reported in a broad spectrum of cardiomyopathies, congenital heart diseases, monogenetic disorders, neuromuscular diseases, and even healthy individuals. LVHT is often associated with systolic dysfunction, arrhythmias, and thromboembolic events. Given the etiologic heterogeneity, the prognosis and outcomes are primarily determined by comorbidities, and treatment is dictated by known guidelines. We present hypertrabeculation (HT) as a phenotype and discuss the varied landscape in the classification, etiology, diagnosis, and management of the condition.

Noncompaction Cardiomyopathy-History and Current Knowledge for Clinical Practice

Noncompaction cardiomyopathy (NCCM) has gained increasing attention over the past twenty years, but in daily clinical practice NCCM is still rarely considered. So far, there are no generally accepted diagnostic criteria and some groups even refuse to acknowledge it as a distinct cardiomyopathy, and grade it as a variant of dilated cardiomyopathy or a morphological trait of different conditions. A wide range of morphological variants have been observed even in healthy persons, suggesting that pathologic remodeling and physiologic adaptation have to be differentiated in cases where this spongy myocardial pattern is encountered. Recent studies have uncovered numerous new pathogenetic and pathophysiologic aspects of this elusive cardiomyopathy, but a current summary and evaluation of clinical patient management are still lacking, especially to avoid mis- and overdiagnosis. Addressing this issue, this article provides an up to date overview of the current knowledge in classification, pathogenesis, pathophysiology, epidemiology, clinical manifestations and diagnostic evaluation, including genetic testing, treatment and prognosis of NCCM.

Catheter ablation of ventricular arrhythmias in left ventricular noncompaction cardiomyopathy

BACKGROUND

There are limited data on ventricular arrhythmias (VAs) associated with left ventricular noncompaction (LVNC) cardiomyopathy.

OBJECTIVES

This study aims to analyze the clinical and electrocardiographic characteristics of VAs in a group of patients with LVNC.

METHODS

Forty-two nonrelated patients with LVNC and VAs were included that were evaluated at the Inherited Cardiac Disease Unit of the University Hospital Virgen Arrixaca (Murcia-Spain) (ERN Guard-Heart Centre, European Reference Network for Rare and Low Prevalence Complex Diseases of the Heart).

RESULTS

Thirteen patients (30.9%) had isolated LVNC, 27 (64.3%) had LVNC associated with dilated cardiomyopathy, and 2 (4.8%) had LVNC associated with hypertrophic cardiomyopathy. Among isolated LVNC individuals, 9 (69.2%) had premature ventricular complexes (PVCs)/nonsustained ventricular tachycardias (VTs), and 4 (30.8%) VTs (1 VT degenerating in ventricular fibrillation). In the dilated cardiomyopathy group, 11 (40.7%) patients had PVCs, 14 (51.9%) VTs, and 2 (7.4%) ventricular fibrillation. In the hypertrophic cardiomyopathy group, one patient had PVCs and the other VTs. Endocardial mapping and ablation were performed in 19 patients (45.2%): 7 ventricular outflow tracts (4 right ventricular outflow tract, 1 left coronary cusp, and 2 right coronary cusp), 2 in the left ventricular summit, 5 related to Purkinje potentials at the mid inferoseptal area, and 5 associated with endocardial scar localized in the basal anterolateral and inferolateral segments. Epicardial ablation was performed in 3 cases.

CONCLUSION

The substrate of VAs in LVNC cardiomyopathy is heterogeneous, with origin in ventricular outflow tracts, Purkinje system related, and resembling scar patterns in nonischemic cardiomyopathy.

The hypertrabeculated (noncompacted) left ventricle is different from the ventricle of embryos and ectothermic vertebrates

Ventricular hypertrabeculation (noncompaction) is a poorly characterized condition associated with heart failure. The condition is widely assumed to be the retention of the trabeculated ventricular design of the embryo and ectothermic (cold-blooded) vertebrates. This assumption appears simplistic and counterfactual. Here, we measured a set of anatomical parameters in hypertrabeculation in man and in the ventricles of embryos and animals. We compared humans with left ventricular hypertrabeculation (N=21) with humans with structurally normal left ventricles (N=54). We measured ejection fraction and ventricular trabeculation using cardiovascular MRI. Ventricular trabeculation was further measured in series of embryonic human and 9 animal species, and in hearts of 15 adult animal species using MRI, CT, or histology. In human, hypertrabeculated left ventricles were significantly different from structurally normal left ventricles by all structural measures and ejection fraction. They were far less trabeculated than human embryonic hearts (15-40% trabeculated volume versus 55-80%). Early in development all vertebrate embryos acquired a ventricle with approximately 80% trabeculations, but only ectotherms retained the 80% trabeculation throughout development. Endothermic (warm-blooded) animals including human slowly matured in fetal and postnatal stages towards ventricles with little trabeculations, generally less than 30%. Further, the trabeculations of all embryos and adult ectotherms were very thin, less than 50 μm wide, whereas the trabeculations in adult endotherms and in the setting of hypertrabeculation were wider by orders of magnitude. It is concluded in contrast to a prevailing assumption, the hypertrabeculated left ventricle is not like the ventricle of the embryo or of adult ectotherms. 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.

Digenic mutational inheritance of the integrin alpha 7 and the myosin heavy chain 7B genes causes congenital myopathy with left ventricular non-compact cardiomyopathy

Background

We report an Italian family in which the proband showed a severe phenotype characterized by the association of congenital fiber type disproportion (CFTD) with a left ventricular non-compaction cardiomyopathy (LVNC). This study was focused on the identification of the responsible gene/s.

Methods and results

Using the whole-exome sequencing approach, we identified the proband homozygous missense mutations in two genes, the myosin heavy chain 7B (MYH7B) and the integrin alpha 7 (ITGA7). Both genes are expressed in heart and muscle tissues, and both mutations were predicted to be deleterious and were not found in the healthy population.

The R890C mutation in the MYH7B gene segregated with the LVNC phenotype in the examined family. It was also found in one unrelated patient affected by LVNC, confirming a causative role in cardiomyopathy.

The E882K mutation in the ITGA7 gene, a key component of the basal lamina of muscle fibers, was found only in the proband, suggesting a role in CFTD.

Conclusions

This study identifies two novel disease genes. Mutation in MYH7B causes a classical LVNC phenotype, whereas mutation in ITGA7 causes CFTD. Both phenotypes represent alterations of skeletal and cardiac muscle maturation and are usually not severe. The severe phenotype of the proband is most likely due to a synergic effect of these two mutations.

This study provides new insights into the genetics underlying Mendelian traits and demonstrates a role for digenic inheritance in complex phenotypes.

[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.

Left ventricular noncompaction: a 25-year odyssey

Left ventricular noncompaction (LVNC) is a cardiomyopathy associated with sporadic or familial disease, the latter having an autosomal dominant mode of transmission. The clinical features associated with LVNC vary from asymptomatic to symptomatic patients, with the potential for heart failure, supraventricular and ventricular arrhythmias, thromboembolic events, and sudden cardiac death. Echocardiography is the diagnostic modality of choice, revealing the pathognomonic features of a thick, bilayered myocardium; prominent ventricular trabeculations; and deep intertrabecular recesses. Widespread use and advances in the technology of echocardiography and cardiac magnetic resonance imaging are increasing awareness of LVNC, and cardiac magnetic resonance imaging is improving the ability to stage the severity of the disease and potential for adverse clinical consequences. Study of LVNC through research in embryology, imaging, and genetics has allowed enormous strides in the understanding of this heterogeneous disease over the past 25 years.

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.

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.

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.

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.

[Noncompaction of the left ventricular myocardium]

BACKGROUND

Noncompaction of the left ventricular myocardium is recently described as a cause of left ventricular dysfunction. In the article, we describe epidemiological and clinical aspects of this condition, which presents clinically at any age.

MATERIAL AND METHODS

This article is based on a review of articles from our own literature archive and relevant references in these articles.

RESULTS

Ventricular noncompaction results from an arrest in the normal endomyocardial embryogenesis, and often leads to heart failure, thrombo-embolic events and/or ventricular arrhythmias. The disorder is diagnosed by two-dimensional echocardiography or magnetic resonance imaging of the heart. The changes are typically seen in the apex and distal and middle segments of the inferior and lateral walls of the left ventricle. The affected segments of the myocardium have a two-layered structure: a compacted thin epicardial layer and an endocardial layer consisting of a prominent trabecular meshwork with deep intertrabecular spaces. The condition can be isolated with or without extracardiac disorders, or can be associated with other cardiac malformations.

INTERPRETATION

It is essential not to miss the findings of noncompaction, as the condition may lead to serious heart failure, thrombo-embolic events, ventricular tachyarrythmias or death. Early recognition of noncompaction may give better follow-up and management of patients with this condition.

Biventricular noncompaction: a case report

Myocardial noncompaction is an extremely uncommon cardiomyopathy. It can present as an isolated cardiac malformation or in association with other congenital anomalies. The left ventricle is usually affected, but a biventricular involvement rarely occurs. A predominant right ventricular involvement has not been reported. Here, we report an 18-year-old woman with biventricular noncompaction that predominantly involves the right ventricle.

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.

Genetic testing in cardiovascular disease

Genetic testing is increasingly becoming possible for diagnosis, susceptibility testing, and prognostication in cardiovascular medicine. The practicing cardiologist, therefore, needs to be familiar with the clinical utilities and limitations of genetic testing. This review explores the major approaches to genetic testing and issues in test interpretation. Specific applications to cardiovascular diseases, including coronary artery disease, cardiomyopathies, cardiac arrhythmias, and pulmonary arterial hypertension are discussed.

[Non-compacted cardiomyopathy: an uncommon cause of ventricular tachycardia]

We present the case of a patient who was previously diagnosed of hypertrophic cardiomyopathy. The patient was admitted to our coronary unit due to a sustained ventricular tachycardia picture. A coronariography was performed as part of the ventricular tachycardia study protocol. It showed angiographically normal epicardic arteries. In the ventriculography, there was a pattern of dilated cardiomyopathy with prominent left ventricular trabeculation, which suggested the diagnosis of non-compacted cardiomyopathy (NCC). The findings of the transthoracic echocardiography, that showed a dilated and hypertrophic left ventricle, with very depressed systolic function, and ventricular myocardium with a thick internal non-compacted endocardium, with a meshwork of multiple trabeculations and intracardic recesses in communication with the ventricular cavity, confirmed this diagnosis. There continues to be little knowledge on NCC and thus it is probably underdiagnosed. It must be considered in the differential diagnosis of patients diagnosed of hypertrophic or dilated cardiomyopathy.

Dystrobrevins in muscle and non-muscle tissues

The alpha- and beta-dystrobrevins belong to the family of dystrophin-related and dystrophin-associated proteins. As constituents of the dystrophin-associated protein complex, alpha-dystrobrevin was believed to have a role predominantly in muscles and beta-dystrobrevin in non-muscle tissues. Recent reports described novel localisations and molecular characteristics of alpha-dystrobrevin isoforms in non-muscle tissues (developing and adult). While single and double knockout studies have revealed distinct functions of dystrobrevin in some tissues, these also suggested a strong compensatory mechanism, where dystrobrevins displaying overlapping tissue expression pattern and structure/function similarity can substitute each other. No human disease has been unequivocally associated within mutations of dystrobrevin genes. However, some significant exceptions to these overlapping expression patterns, mainly in the brain, suggest that dystrobrevin mutations might underlie some specific motor, behavioural or cognitive defects. Dystrobrevin binding partner DTNBP1 (dysbindin) is a probable susceptibility gene for schizophrenia and bipolar affective disorder in some populations. As dysbindin abnormality is linked to Hermansky-Pudlak syndrome, dystrobrevins and/or their binding partners may also be required for proper function of other non-muscle tissues.