Left ventricular noncompaction and cardiomyopathy: cause, contributor, or epiphenomenon? Curr Opin Cardiol. 2008;23:171-175. [PMID: 18382203 DOI: 10.1097/hco.0b013e3282fdc939]

Biventricular noncompaction induced heart failure in premature newborn

Deep intertrabecular recesses and overly pronounced trabeculations in one ventricle are the hallmarks of noncompaction cardiomyopathy (NCCM), a rare congenital cardiomyopathy but very rarely right ventricle (RV), or both ventricles may be involved. We reported a 5-day-old preterm newborn with signs of congestive heart failure that the transthoracic echocardiography (TTE) revealed deep intertrabecular recesses perfused from the left ventricle (LV) and RV cavity, as well as significantly increased wall thickness of the right ventricles and hypertrabeculations in the apical and midventricular segments.

Mouse Models of Cardiomyopathies Caused by Mutations in Troponin C

Cardiac muscle contraction is regulated via Ca2+ exchange with the hetero-trimeric troponin complex located on the thin filament. Binding of Ca2+ to cardiac troponin C, a Ca2+ sensing subunit within the troponin complex, results in a series of conformational re-arrangements among the thin filament components, leading to an increase in the formation of actomyosin cross-bridges and muscle contraction. Ultimately, a decline in intracellular Ca2+ leads to the dissociation of Ca2+ from troponin C, inhibiting cross-bridge cycling and initiating muscle relaxation. Therefore, troponin C plays a crucial role in the regulation of cardiac muscle contraction and relaxation. Naturally occurring and engineered mutations in troponin C can lead to altered interactions among components of the thin filament and to aberrant Ca2+ binding and exchange with the thin filament. Mutations in troponin C have been associated with various forms of cardiac disease, including hypertrophic, restrictive, dilated, and left ventricular noncompaction cardiomyopathies. Despite progress made to date, more information from human studies, biophysical characterizations, and animal models is required for a clearer understanding of disease drivers that lead to cardiomyopathies. The unique use of engineered cardiac troponin C with the L48Q mutation that had been thoroughly characterized and genetically introduced into mouse myocardium clearly demonstrates that Ca2+ sensitization in and of itself should not necessarily be considered a disease driver. This opens the door for small molecule and protein engineering strategies to help boost impaired systolic function. On the other hand, the engineered troponin C mutants (I61Q and D73N), genetically introduced into mouse myocardium, demonstrate that Ca2+ desensitization under basal conditions may be a driving factor for dilated cardiomyopathy. In addition to enhancing our knowledge of molecular mechanisms that trigger hypertrophy, dilation, morbidity, and mortality, these cardiomyopathy mouse models could be used to test novel treatment strategies for cardiovascular diseases. In this review, we will discuss (1) the various ways mutations in cardiac troponin C might lead to disease; (2) relevant data on mutations in cardiac troponin C linked to human disease, and (3) all currently existing mouse models containing cardiac troponin C mutations (disease-associated and engineered).

Prognosis and subtype analysis of left ventricular noncompaction in adults: A retrospective multicenter study

BACKGROUND

Left ventricular noncompaction (LVNC) is a heterogeneous myocardial disorder with an uncertain prognosis. There was a lack of studies on LVNC subtypes at present. This study sought to identify the prognosis of the overall population of LVNC and to describe the distribution of different subtypes and compare their prognosis.

HYPOTHESIS

Patients with different subtypes of LVNC may have different prognoses.

METHODS

Patients who fulfilled the Jenni criteria and/or Petersen criteria were included. Major adverse cardiovascular events (MACE) were defined as a combination of heart failure (HF) hospitalization and all-cause mortality.

RESULTS

A total of 200 patients from four hospitals were included. The mean age at diagnosis was 48.2 years, and 61.5% of the patients were male. Left ventricular ejection fraction (LVEF) < 50% was present in 54% of the patients. Over a mean retrospective time period of 22.2 months, 47 (23.5%) patients experienced MACE. Age (hazard ratio [HR] 1.03; 95% confidence interval [CI] 1.01-1.06; p = .004), LVEF < 50% (HR 2.32; 95% CI 1.09-4.91; p = .028) and ventricular tachycardia/ventricular fibrillation (HR 2.17; 95% CI 1.08-4.37; p = .03) were significantly associated with the risk of MACE. The most common subtype was dilated LVNC (51.3%), followed by benign LVNC (21.3%) and LVNC with arrhythmias (10.5%). Patients with dilated LVNC had significantly increased cumulative incidence of MACE, HF hospitalization, and all-cause mortality (p < .05).

CONCLUSIONS

Age, LVEF < 50%, and ventricular tachycardia/ventricular fibrillation were independent risk factors for prognosis of LVNC. The most common subtype was dilated LVNC, which had a worse prognosis.

Left ventricular non-compaction cardiomyopathy associated with the PRKAG2 mutation

Left ventricular non-compaction cardiomyopathy (LVNC) is one of the most common inherited cardiovascular diseases. The genetic backgrounds of most LVNC patients are not fully understood. We collected clinical data, family histories, and blood samples and performed genetic analysis using next-generation sequencing (NGS) from a Chinese family of 15 subjects. Clinically LVNC affected subjects showed marked cardiac phenotype heterogeneity. We found that these subjects with LVNC carried a missense heterozygous genetic mutation c.905G>A (p.R302Q) in γ2 subunit of AMP-activated protein kinase (PRKAG2) gene through NGS. Individuals without this mutation showed no symptoms or cardiac structural abnormalities related to LVNC. One subject was the victim of sudden cardiac death. To sum up, PRKAG2 mutation c.905G>A (p.R302Q) caused familial LVNC. Our results described a potentially pathogenic mutation associated with LVNC, which may further extend the spectrum of LVNC phenotypes related to PRKAG2 gene mutations.

Acute-onset heart failure secondary to biventricular non-compaction cardiomyopathy and atrial septal defect in a woman presenting in the seventh decade

We present a case of a previously asymptomatic 63-year-old woman who presented with worsening dyspnoea for 3 weeks. Initial transthoracic and later transoesophageal echocardiography confirmed biventricular non-compaction cardiomyopathy and a large secundum atrial septal defect (ASD) measuring 1.4 cm. Additionally, there was a haemodynamically significant left to right shunt causing acute decompensated systolic heart failure. She eventually underwent closure of the septal defect using a AMPLATZER Septal Occluder device. Decision to close the defect was made as the left to right shunt was causing severe pulmonary hypertension and acute heart failure. Since most heart failure treatments involve lowering of the LV afterload there was consideration that this could cause right to left shunting and could cause an Eisenmenger physiology. Hence the AMPLATZER Septal Occluder device was placed to eliminate the shunt through the ASD. The ASD combined with the non-compaction posed significant treatment challenge in this case.

PRDM16 Is a Compact Myocardium-Enriched Transcription Factor Required to Maintain Compact Myocardial Cardiomyocyte Identity in Left Ventricle

BACKGROUND

Left ventricular noncompaction cardiomyopathy (LVNC) was discovered half a century ago as a cardiomyopathy with excessive trabeculation and a thin ventricular wall. In the decades since, numerous studies have demonstrated that LVNC primarily has an effect on left ventricles (LVs) and is often associated with LV dilation and dysfunction. However, in part because of the lack of suitable mouse models that faithfully mirror the selective LV vulnerability in patients, mechanisms underlying the susceptibility of LVs to dilation and dysfunction in LVNC remain unknown. Genetic studies have revealed that deletions and mutations in PRDM16 (PR domain-containing 16) cause LVNC, but previous conditional Prdm16 knockout mouse models do not mirror the LVNC phenotype in patients, and the underlying molecular mechanisms by which PRDM16 deficiency causes LVNC are still unclear.

METHODS

Prdm16 cardiomyocyte-specific knockout (Prdm16cKO) mice were generated and analyzed for cardiac phenotypes. RNA sequencing and chromatin immunoprecipitation deep sequencing were performed to identify direct transcriptional targets of PRDM16 in cardiomyocytes. Single-cell RNA sequencing in combination with spatial transcriptomics was used to determine cardiomyocyte identity at the single-cell level.

RESULTS

Cardiomyocyte-specific ablation of Prdm16 in mice caused LV-specific dilation and dysfunction, as well as biventricular noncompaction, which fully recapitulated LVNC in patients. PRDM16 functioned mechanistically as a compact myocardium-enriched transcription factor that activated compact myocardial genes while repressing trabecular myocardial genes in LV compact myocardium. Consequently, Prdm16cKO LV compact myocardial cardiomyocytes shifted from their normal transcriptomic identity to a transcriptional signature resembling trabecular myocardial cardiomyocytes or neurons. Chamber-specific transcriptional regulation by PRDM16 was attributable in part to its cooperation with LV-enriched transcription factors Tbx5 and Hand1.

CONCLUSIONS

These results demonstrate that disruption of proper specification of compact cardiomyocytes may play a key role in the pathogenesis of LVNC. They also shed light on underlying mechanisms of the LV-restricted transcriptional program governing LV chamber growth and maturation, providing a tangible explanation for the susceptibility of LV in a subset of LVNC cardiomyopathies.

Prognostic value of plasma big endothelin-1 in left ventricular non-compaction cardiomyopathy

Objective

To determine the prognostic role of big endothelin-1 (ET-1) in left ventricular non-compaction cardiomyopathy (LVNC).

Methods

We prospectively enrolled patients whose LVNC was diagnosed by cardiac MRI and who had big ET-1 data available. Primary end point was a composite of all-cause mortality, heart transplantation, sustained ventricular tachycardia/fibrillation and implanted cardioverter defibrillator discharge. Secondary end point was cardiac death or heart transplantation.

Results

Altogether, 203 patients (median age 44 years; 70.9% male) were divided into high-level (≥0.42 pmol/L) and low-level (<0.42 pmol/L) big ET-1 groups according to the median value of plasma big ET-1 levels. Ln big ET-1 was positively associated with Ln N-terminal pro-brain natriuretic peptide, left ventricular diameter, but negatively related to age and Ln left ventricular ejection fraction. Median follow-up was 1.9 years (IQR 0.9–3.1 years). Kaplan-Meier analysis showed that, compared with patients with low levels of big ET-1, those with high levels were at greater risk for meeting both primary (p<0.001) and secondary (p<0.001) end points. The C-statistic estimation of Ln big ET-1 for predicting the primary outcome was 0.755 (95% CI 0.685 to 0.824, p<0.001). After adjusting for confounding factors, Ln big ET-1 was identified as an independent predictor of the composite primary outcome (HR 1.83, 95% CI 1.27 to 2.62, p=0.001) and secondary outcome (HR 1.93, 95% CI 1.32 to 2.83, p=0.001).

Conclusions

Plasma big ET-1 may be a valuable index to predict the clinical adverse outcomes in patients with LVNC.

Non-compaction cardiomyopathy in pregnancy: a case report of spongy myocardium in both mother and foetus and systematic review of literature

PURPOSE

Cardiovascular disease is the main nonobstetric cause of maternal death during pregnancy and is present in 0.5-4% of pregnancies in the western world. While hypertensive disorders remain the most frequent events, occurring in 6-8% of all pregnancies, cardiomyopathies are rare but encompass high complication rates. The aim of this systematic review is to report all data available up to date regarding pregnancies in patients with left ventricular noncompaction (LVNC) cardiomyopathy.

METHODS

PubMed, Medline, Cochrane, Scopus and Embase were searched, up to January 2019, using combinations of these terms: left ventricular noncompaction, hypertrabeculation cardiomyopathy, spongy myocardium, spongiform cardiomyopathy and delivery, gestation, pregnancy, cesarean section (CS). After careful selection, 22 articles, reporting a total of 30 cases, including our own were included in the review.

RESULTS

Fifteen out of 26 women (58%) were diagnosed with LVNC before pregnancy. Around 56% of women presented with symptoms during pregnancy while 44% were asymptomatic. Heart failure is by far the most common symptom occurring in almost half the cases. Uncommon clinical presentations included a heart attack, a stroke, and pulmonary hypertension. Timing of delivery was reported preterm in 58% of cases and at term in 42%. Eleven women gave birth through vaginal delivery, while 15 (58%) underwent a CS. Our reported case is the first case of a pregnancy where both mother and fetus are affected by LVNC and the fetus is diagnosed prenatally.

CONCLUSIONS

LVNC is not a contraindication for pregnancy, but clearly increases the risk of preterm birth and the rate of cesarean section. On the other hand, pregnancy in a LVNC patient exposes her to increased risk of clinical deterioration. Further studies are needed to better characterize the management of pregnancies in women with cardiomyopathies.

Biventricular Noncompaction Cardiomyopathy Accompanied by Severe Pulmonary Valvular Stenosis and Patent Foramen Ovale

Myocardial non-compaction (NC) is a rare genetic cardiomyopathy commonly believed to develop an intrauterine arrest of endomyocardial morphogenesis. NC is characterized by markedly hypertrabeculations in left ventricle or both ventricles with deep intertrabecular recesses. NC is usually seen isolated, but sometimes other congenital heart abnormalities may accompany to the myocardial NC. In this article we have presented an adult patient with biventricular myocardial NC cardiomyopathy accompanied by severe valvular pulmonary stenosis and patent foramen ovale.

Novel Genetic Triggers and Genotype-Phenotype Correlations in Patients With Left Ventricular Noncompaction

BACKGROUND

Left ventricular noncompaction (LVNC) is a genetically and phenotypically heterogeneous disease and, although increasingly recognized in clinical practice, there is a lack of widely accepted diagnostic criteria. We sought to identify novel genetic causes of LVNC and describe genotype-phenotype correlations.

METHODS AND RESULTS

A total of 190 patients from 174 families with left ventricular hypertrabeculation (LVHT) or LVNC were referred for cardiac magnetic resonance and whole-exome sequencing. A total of 425 control individuals were included to identify variants of interest (VOIs). We found an excess of 138 VOIs in 102 (59%) unrelated patients in 54 previously identified LVNC or other known cardiomyopathy genes. VOIs were found in 68 of 90 probands with LVNC and 34 of 84 probands with LVHT (76% and 40%, respectively; P<0.001). We identified 0, 1, and ≥2 VOIs in 72, 74, and 28 probands, respectively. We found increasing number of VOIs in a patient strongly correlated with several markers of disease severity, including ratio of noncompacted to compacted myocardium (P<0.001) and left ventricular ejection fraction (P=0.01). The presence of sarcomeric gene mutations was associated with increased occurrence of late gadolinium enhancement (P=0.004).

CONCLUSIONS

LVHT and LVNC likely represent a continuum of genotypic disease with differences in severity and variable phenotype explained, in part, by the number of VOIs and whether mutations are present in sarcomeric or nonsarcomeric genes. Presence of VOIs is common in patients with LVHT. Our findings expand the current clinical and genetic diagnostic approaches for patients with LVHT and LVNC.

Adaptation and validation of the ACMG/AMP variant classification framework for MYH7-associated inherited cardiomyopathies: recommendations by ClinGen's Inherited Cardiomyopathy Expert Panel

Purpose

Integrating genomic sequencing in clinical care requires standardization of variant interpretation practices. The Clinical Genome Resource has established expert panels to adapt the American College of Medical Genetics and Genomics/Association for Molecular Pathology classification framework for specific genes and diseases. The Cardiomyopathy Expert Panel selected MYH7, a key contributor to inherited cardiomyopathies, as a pilot gene to develop a broadly applicable approach.

Methods

Expert revisions were tested with 60 variants using a structured double review by pairs of clinical and diagnostic laboratory experts. Final consensus rules were established via iterative discussions.

Results

Adjustments represented disease-/gene-informed specifications (12) or strength adjustments of existing rules (5). Nine rules were deemed not applicable. Key specifications included quantitative frameworks for minor allele frequency thresholds, the use of segregation data, and a semiquantitative approach to counting multiple independent variant occurrences where fully controlled case-control studies are lacking. Initial inter-expert classification concordance was 93%. Internal data from participating diagnostic laboratories changed the classification of 20% of the variants (n = 12), highlighting the critical importance of data sharing.

Conclusion

These adapted rules provide increased specificity for use in MYH7-associated disorders in combination with expert review and clinical judgment and serve as a stepping stone for genes and disorders with similar genetic and clinical characteristics.

Pediatric Cardiomyopathies

Pediatric cardiomyopathies are rare diseases with an annual incidence of 1.1 to 1.5 per 100 000. Dilated and hypertrophic cardiomyopathies are the most common; restrictive, noncompaction, and mixed cardiomyopathies occur infrequently; and arrhythmogenic right ventricular cardiomyopathy is rare. Pediatric cardiomyopathies can result from coronary artery abnormalities, tachyarrhythmias, exposure to infection or toxins, or secondary to other underlying disorders. Increasingly, the importance of genetic mutations in the pathogenesis of isolated or syndromic pediatric cardiomyopathies is becoming apparent. Pediatric cardiomyopathies often occur in the absence of comorbidities, such as atherosclerosis, hypertension, renal dysfunction, and diabetes mellitus; as a result, they offer insights into the primary pathogenesis of myocardial dysfunction. Large international registries have characterized the epidemiology, cause, and outcomes of pediatric cardiomyopathies. Although adult and pediatric cardiomyopathies have similar morphological and clinical manifestations, their outcomes differ significantly. Within 2 years of presentation, normalization of function occurs in 20% of children with dilated cardiomyopathy, and 40% die or undergo transplantation. Infants with hypertrophic cardiomyopathy have a 2-year mortality of 30%, whereas death is rare in older children. Sudden death is rare. Molecular evidence indicates that gene expression differs between adult and pediatric cardiomyopathies, suggesting that treatment response may differ as well. Clinical trials to support evidence-based treatments and the development of disease-specific therapies for pediatric cardiomyopathies are in their infancy. This compendium summarizes current knowledge of the genetic and molecular origins, clinical course, and outcomes of the most common phenotypic presentations of pediatric cardiomyopathies and highlights key areas where additional research is required.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifiers: NCT02549664 and NCT01912534.

MIB2 variants altering NOTCH signalling result in left ventricle hypertrabeculation/non-compaction and are associated with Ménétrier-like gastropathy

We performed whole exome sequencing in individuals from a family with autosomal dominant gastropathy resembling Ménétrier disease, a premalignant gastric disorder with epithelial hyperplasia and enhanced EGFR signalling. Ménétrier disease is believed to be an acquired disorder, but its aetiology is unknown. In affected members, we found a missense p.V742G variant in MIB2, a gene regulating NOTCH signalling that has not been previously linked to human diseases. The variant segregated with the disease in the pedigree, affected a highly conserved amino acid residue, and was predicted to be deleterious although it was found with a low frequency in control individuals. The purified protein carrying the p.V742G variant showed reduced ubiquitination activity in vitro and white blood cells from affected individuals exhibited significant reductions of HES1 and NOTCH3 expression reflecting alteration of NOTCH signalling. Because mutations of MIB1, the homolog of MIB2, have been found in patients with left ventricle non-compaction (LVNC), we investigated members of our family with Ménétrier-like disease for this cardiac abnormality. Asymptomatic left ventricular hypertrabeculation, the mildest end of the LVNC spectrum, was detected in two members carrying the MIB2 variant. Finally, we identified an additional MIB2 variant (p.V984L) affecting protein stability in an unrelated isolated case with LVNC. Expression of both MIB2 variants affected NOTCH signalling, proliferation and apoptosis in primary rat cardiomyocytes.In conclusion, we report the first example of left ventricular hypertrabeculation/LVNC with germline MIB2 variants resulting in altered NOTCH signalling that might be associated with a gastropathy clinically overlapping with Ménétrier disease.

iPSC-derived cardiomyocytes reveal abnormal TGF-β signalling in left ventricular non-compaction cardiomyopathy

Left ventricular non-compaction (LVNC) is the third most prevalent cardiomyopathy in children and its pathogenesis has been associated with the developmental defect of the embryonic myocardium. We show that patient-specific induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) generated from LVNC patients carrying a mutation in the cardiac transcription factor TBX20 recapitulate a key aspect of the pathological phenotype at the single-cell level and this was associated with perturbed transforming growth factor beta (TGF-β) signalling. LVNC iPSC-CMs have decreased proliferative capacity due to abnormal activation of TGF-β signalling. TBX20 regulates the expression of TGF-β signalling modifiers including one known to be a genetic cause of LVNC, PRDM16, and genome editing of PRDM16 caused proliferation defects in iPSC-CMs. Inhibition of TGF-β signalling and genome correction of the TBX20 mutation were sufficient to reverse the disease phenotype. Our study demonstrates that iPSC-CMs are a useful tool for the exploration of pathological mechanisms underlying poorly understood cardiomyopathies including LVNC.

The pathogenicity of genetic variants previously associated with left ventricular non-compaction

Background

Left ventricular non‐compaction (LVNC) is a rare cardiomyopathy. Many genetic variants have been associated with LVNC. However, the number of the previous LVNC‐associated variants that are common in the background population remains unknown. The aim of this study was to provide an updated list of previously reported LVNC‐associated variants with biologic description and investigate the prevalence of LVNC variants in healthy general population to find false‐positive LVNC‐associated variants.

Methods and Results

The Human Gene Mutation Database and PubMed were systematically searched to identify all previously reported LVNC‐associated variants. Thereafter, the Exome Sequencing Project (ESP) and the Exome Aggregation Consortium (ExAC), that both represent the background population, was searched for all variants. Four in silico prediction tools were assessed to determine the functional effects of these variants. The prediction results of those identified in the ESP and ExAC and those not identified in the ESP and ExAC were compared. In 12 genes, 60 LVNC‐associated missense/nonsense variants were identified. MYH7 was the predominant gene, encompassing 24 of the 60 LVNC‐associated variants. The ESP only harbored nine and ExAC harbored 18 of the 60 LVNC‐associated variants. In total, eight out of nine ESP‐positive variants overlapped with the 18 variants identified in ExAC database.

Conclusions

In this article, we identified 9 ESP‐positive and 18 ExAC‐positive variants of 60 previously reported LVNC‐associated variants, suggesting that these variants are not necessarily the monogenic cause of LVNC.

Role of left ventricular twist mechanics in cardiomyopathies, dance of the helices

Left ventricular twist is an essential part of left ventricular function. Nevertheless, knowledge is limited in “the cardiology community” as it comes to twist mechanics. Fortunately the development of speckle tracking echocardiography, allowing accurate, reproducible and rapid bedside assessment of left ventricular twist, has boosted the interest in this important mechanical aspect of left ventricular deformation. Although the fundamental physiological role of left ventricular twist is undisputable, the clinical relevance of assessment of left ventricular twist in cardiomyopathies still needs to be established. The fact remains; analysis of left ventricular twist mechanics has already provided substantial pathophysiological understanding on a comprehensive variety of cardiomyopathies. It has become clear that increased left ventricular twist in for example hypertrophic cardiomyopathy may be an early sign of subendocardial (microvascular) dysfunction. Furthermore, decreased left ventricular twist may be caused by left ventricular dilatation or an extensive myocardial scar. Finally, the detection of left ventricular rigid body rotation in noncompaction cardiomyopathy may provide an indispensible method to objectively confirm this difficult diagnosis. All this endorses the value of left ventricular twist in the field of cardiomyopathies and may further encourage the implementation of left ventricular twist parameters in the “diagnostic toolbox” for cardiomyopathies.

Left ventricular non-compaction cardiomyopathy

Left ventricular non-compaction, the most recently classified form of cardiomyopathy, is characterised by abnormal trabeculations in the left ventricle, most frequently at the apex. It can be associated with left ventricular dilation or hypertrophy, systolic or diastolic dysfunction, or both, or various forms of congenital heart disease. Affected individuals are at risk of left or right ventricular failure, or both. Heart failure symptoms can be induced by exercise or be persistent at rest, but many patients are asymptomatic. Patients on chronic treatment for compensated heart failure sometimes present acutely with decompensated heart failure. Other life-threatening risks of left ventricular non-compaction are ventricular arrhythmias or complete atrioventricular block, presenting clinically as syncope, and sudden death. Genetic inheritance arises in at least 30-50% of patients, and several genes that cause left ventricular non-compaction have been identified. These genes seem generally to encode sarcomeric (contractile apparatus) or cytoskeletal proteins, although, in the case of left ventricular non-compaction with congenital heart disease, disturbance of the NOTCH signalling pathway seems part of a final common pathway for this form of the disease. Disrupted mitochondrial function and metabolic abnormalities have a causal role too. Treatments focus on improvement of cardiac efficiency and reduction of mechanical stress in patients with systolic dysfunction. Further, treatment of arrhythmia and implantation of an automatic implantable cardioverter-defibrillator for prevention of sudden death are mainstays of therapy when deemed necessary and appropriate. Patients with left ventricular non-compaction and congenital heart disease often need surgical or catheter-based interventions. Despite progress in diagnosis and treatment in the past 10 years, understanding of the disorder and outcomes need to be improved.

Diagnosis and management of hypertrophic cardiomyopathy

The clinical spectrum of hypertrophic cardiomyopathy (HCM) is complex and includes a variety of phenotypes, which leads to different types of manifestations. Although most of the patients are asymptomatic, a significant proportion of them will develop symptoms or risk of arrhythmias and sudden cardiac death (SCD). Therefore, the objectives of HCM diagnosis and management are to relieve the patients' symptoms (chest pain, heart failure, syncope, palpitations, etc.), prevent disease progression and major cardiovascular complications and SCD. The heterogeneity of HCM patterns, their symptoms and assessment is a challenge for the cardiologist.

Ventricular non-compaction cardiomyopathy: prenatal diagnosis and pathology

OBJECTIVE

The objective of this study is to evaluate the prenatal diagnosis of ventricular non-compaction cardiomyopathy (NCCM) and to report the pathologic features and the characteristic myocardial ultrastructure of fetal NCCM.

METHOD

We examined nine cases of fetal NCCM by prenatal echocardiography from 2004 to 2013. These cases were evaluated with respect to prenatal diagnosis, outcomes, pathology, and characteristics of the myocardial ultrastructure.

RESULTS

Trabeculated myocardium and non-compaction/compaction ratio (N/C ratio) ≥2.0 is the echocardiographic feature that allowed diagnosis. Among the nine fetuses with a prenatal diagnosis of NCCM, six were diagnosed with left ventricular non-compaction (LVNC), two with non-compaction of both ventricles (biventricular NCCM), and one with right ventricular non-compaction. Among the nine fetuses, the LVNC diagnosis was confirmed by postnatal echocardiography in 2; the other patients chose to terminate their pregnancies, and those cases were confirmed at autopsy. Muscle biopsies were performed on three of the aborted fetuses, and abnormal mitochondria, sarcomeres, and myocardial fibers were observed.

CONCLUSION

Non-compaction can be identified in the fetus. Fetal non-compaction most often involves the left ventricle, but can involve the right ventricle or both ventricles. The myocardial ultrastructure of fetal ventricular non-compaction has certain unique characteristics regarding the maturation of the mitochondria, sarcomeres, and myocardial fibers. © 2014 John Wiley & Sons, Ltd.

Right ventricular cardiomyopathies: a multidisciplinary approach to diagnosis

The physiological importance of the right ventricle (RV) has been underestimated over the past years. Finally in the early 1950s through the 1970s, cardiac surgeons recognized the importance of RV function. Since then, the importance of RV function has been recognized in many acquired cardiac heart disease. RV can be mainly or together with left ventricle (LV) affected by inherited or acquired cardiomyopathy. In fact, RV morphological and functional remodeling occurs more common during cardiomyopathies than in ischemic cardiomyopathies and more closely parallels LV dysfunction. Moreover, there are some cardiomyopathy subtypes showing a predominant or exclusive involvement of the RV, and they are probably less known by cardiologists. The clinical approach to right ventricular cardiomyopathies is often challenging. Imaging is the first step to raise the suspicion and to guide the diagnostic process. In the differential diagnosis, cardiologists should consider athlete's heart, congenital heart diseases, multisystemic disorders, and inherited arrhythmias. However, a multiparametric and multidisciplinary approach, involving cardiologists, experts in imaging, geneticists, and pathologists with a specific expertise in these heart muscle disorders is required.

[Juvenile neuronal ceroid-lipofuscinosis with hypertrophic cardiomyopathy and left ventricular noncompaction: a case report]

We report a 17-year-old female with juvenile neuronal ceroid-lipofuscinosis (NCL) accompanied by hypertrophic cardiomyopathy (HCM) and left ventricular noncompaction (LVNC). Within our knowledge, this is the first reported case of juvenile NCL with LVNC, and the youngest case of HCM diagnosed by ultrasound. Juvenile NCL is a progressive hereditary disease involving multi-organ accumulation of ceroid-lipofuscin; its resulting complications require prompt attention. Due to its relative rarity, its cardiac involvement is not well known. Based on findings from this patient and related juvenile NCL cases, the risk of cardiac involvement tends to increase with age; a high frequency of ventricular hypertrophy has been reported in patients aged older than 20 years of age. Medical progress and comprehensive care have led to longer survival in patients with juvenile NCL, which likely increases the incidence of cardiac involvement. In relation to HCM in other metabolic disorders, attention should be paid to arrhythmias, including repolarization disturbances, sinus node dysfunction and ventricular tachycardia. LVNC is a cardiomyopathy characterized by prominent left ventricular trabeculae and deep intratrabecular recesses, which are associated with diastolic or systolic dysfunction, thromboembolic complications and arrhythmias. From ours and other case reports, we recommend regular follow-up of NCL patients as follows: echocardiography to estimate cardiomyopathy, Holter monitoring to identify arrhythmias, and computed tomography to detect thrombosis from both ventricles. The mechanism of the HCM and LVNC associated with juvenile NCL remains unclear. Our case requires careful follow-up. Prospective studies of the cardiac involvement in juvenile NCL are necessary to further elucidate its pathomechanism.

Noncompaction cardiomyopathy: Manifestation as a surgical pitfall – rare but real

Objectives

Noncompaction cardiomyopathy is characterized by hyper-trabeculation of the myocardium. The patients present with heart failure and variable combination of arrhythmias and thromboembolism. Although several articles have shed light on the medical aspect of this disease, none have highlighted its surgical relevance. A death following ligation of a patent ductus arteriosus prompted us to evaluate the surgical aspects of this disease.

Methods

Autopsy records from 2003 to 2012 were reviewed, and cases identified as noncompaction cardiomyopathy were retrieved and analyzed. Cases with obligatory hyper-trabeculation were excluded.

Results

Thirteen patients were found to have noncompaction cardiomyopathy in 9427 autopsies performed. Their ages ranged from 4 months to 55 years; 10 were children, and all 3 adults were over 45 years of age. Only one patient had an antemortem diagnosis of noncompaction cardiomyopathy on echocardiography. There were 7 postoperative deaths.

Conclusions

Although noncompaction cardiomyopathy is rare, missing its diagnosis in a patient operated on for another indication can spell disaster postoperatively. As the clinical picture is nonspecific and the disease is not very well known, it needs vigilance on the part of the echocardiographer and surgeon.

Mendelian forms of structural cardiovascular disease

Clinical and molecular genetics are inextricably linked. In the last two decades genetic studies have revealed the causes of several forms of structural heart disease. Recent work is extending the insights from inherited arrhythmias and cardiomyopathies to other forms of heart disease. In this review we outline the current state of the art for the genetics of adult structural heart disease, in particular the cardiomyopathies, valvular heart disease and aortic disease. The general approaches are described with a focus on clinical relevance, while potential areas for imminent innovation in diagnosis and therapeutics are highlighted.

Reduced left ventricular compacta thickness: a novel echocardiographic criterion for non-compaction cardiomyopathy

BACKGROUND

Left ventricular noncompaction (LVNC) is characterized by a two-layered myocardium consisting of a noncompacted inner and a compacted outer layer. The ratio of the thicknesses of these two layers is a major diagnostic criterion, which is, however, often difficult to apply in clinical practice.

METHODS

Transthoracic echocardiography was performed in 41 patients with LVNC, 41 patients with moderate or severe aortic valve stenosis (AVS), and 41 age-matched normal controls. The maximal systolic thicknesses of "noncompacta" and "compacta" were measured in standard short-axis views at the apical or midventricular level, in the segment with most prominent recesses (in patients with LVNC) or trabeculation (in patients with AVS and controls).

RESULTS

The mean maximal systolic thickness of noncompacta was 1.8 ± 0.4 cm in patients with LVNC compared with 0.2 ± 0.1 cm in controls and 0.6 ± 0.02 cm in patients with AVS (P < .0001). The mean maximal systolic thickness of compacta was lower in patients with LVNC (0.5 ± 0.1 cm) compared to controls (1.2 ± 0.2 cm; P < .0001) and patients with AVS (1.6 ± 0.06 cm; P < .0001). The maximal systolic thickness of compacta was ≤8.1 mm in patients with LVNC compared with >8.1 mm (P < .0001) in controls and >8.1 mm in patients with AVS (P < .0001). The ratio of the maximal systolic thickness of the indexed basal septum to that of the compacta was ≥0.64/m(2) in patients with LVNC compared to ≤0.62/m(2) in controls and ≤0.96/m(2) in patients with AVS.

CONCLUSIONS

Maximal systolic compacta thickness <8 mm is specific for LVNC and allows the differentiation of LVNC from normal hearts as well as those with myocardial thickening due to AVS. This observation may be particularly useful as an additional diagnostic criterion for preventing the overdiagnosis of LVNC.

Investigation of cardiomyopathy using cardiac magnetic resonance imaging part 2: Rare phenotypes

Cardiac magnetic resonance imaging (CMRI) has emerged as a useful tertiary imaging tool in the investigation of patients suspected of many different types of cardiomyopathies. CMRI images are now of a sufficiently robust quality to enable high spatial and temporal resolution image acquisition. This has led to CMRI becoming an effective non-invasive imaging tool for many cardiomyopathies. In this two-part review we outline the typical sequences used to image cardiomyopathy and present the imaging spectrum of cardiomyopathy. Part I focused on the current classification of cardiomyopathy, the basic CMRI sequences used in evaluating cardiomyopathy and the imaging spectrum of common phenotypes. Part II illustrates the imaging spectrum of the more rare phenotypes.

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.

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.

Subendocardial fibrosis in left ventricular hypertrabeculation-cause or consequence?

Left ventricular noncompaction has been classified as a primary cardiomyopathy with a genetic origin. This condition is morphologically characterized by a thickened, two-layered myocardium with numerous prominent trabeculations and deep, intertrabecular recesses. Recently, it has become clear that these pathological characteristics extend across a continuum with left ventricular hypertrabeculation at one end of the spectrum.

The histological findings include areas of interstitial fibrosis.

We present a case of left ventricular hypertrabeculation which presented as sudden infant death syndrome. Histologically areas of subendocardial fibrosis was prominent and we propose that this entity may be a hidden cause of arrhythmic death in some infants presenting as sudden infant death syndrome., with areas of subendocardial fibrosis as possible arrhythmogenic foci.

Identification of a novel TPM1 mutation in a family with left ventricular noncompaction and sudden death

Left ventricular noncompaction (LVNC) is a cardiomyopathy morphologically characterized by 2-layered myocardium, numerous prominent trabeculations, and deep intertrabecular recesses communicating with the left ventricular cavity. The purpose of this study was to investigate patients with LVNC for possible disease causing mutations. We screened 4 genes (TAZ, LDB3, DTNA and TPM1) in 51 patients with LVNC for mutations by polymerase chain reaction and direct DNA sequencing. A novel missense substitution in exon 1 of TPM1 (c.109A>G: p.Lys37Glu) was identified in three affected members of a family with isolated LVNC. The substitution brings about a change in amino acid charge at a highly conserved residue and could result in aberrant mRNA splicing. This variant was not identified in 200 normal control samples. Pathologic analysis of a right ventricular myocardial specimen from the proband's maternal aunt revealed endocardial and subendocardial fibrosis with prominent elastin deposition, as well as the presence of adipose tissue between muscle layers, pathologic changes that are distinct from those seen in patients with HCM or DCM. Screening of the proband and her mother for variants in other sarcomeric protein-encoding candidate genes, MYH7, MYBPC3, TNNT2, TNNI3, ACTC, MYL2, and MYL3, did not identify any other non-synonymous variants or variants in splice donor-acceptor sequences that were potentially disease causing. We conclude TPM1 is a potential candidate disease-causing gene for isolated LVNC, especially in patients experiencing sudden death.

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.

Uncharted waters: rare and unclassified cardiomyopathies characterized on cardiac magnetic resonance imaging

Cardiac magnetic resonance imaging (CMR) has undergone considerable technology advances in recent years, so that it is now entering into mainstream cardiac imaging practice. In particular, CMR is proving to be a valuable imaging tool in the detection, morphological assessment and functional assessment of cardiomyopathies. Although our understanding of this broad group of heart disorders continues to expand, it is an evolving group of entities, with the rarer cardiomyopathies remaining poorly understood or even unclassified. In this review, we describe the clinical and pathophysiological aspects of several of the rare/unclassified cardiomyopathies and their appearance on CMR.