The utility of magnetic resonance imaging in the evaluation of arrhythmogenic right ventricular cardiomyopathy

The Role of MicroRNAs in Arrhythmogenic Cardiomyopathy: Biomarkers or Innocent Bystanders of Disease Progression?

Arrhythmogenic cardiomyopathy (AC) is an inherited cardiac disease characterized by a progressive fibro-fatty replacement of the working myocardium and by life-threatening arrhythmias and risk of sudden cardiac death. Pathogenic variants are identified in nearly 50% of affected patients mostly in genes encoding for desmosomal proteins. AC incomplete penetrance and phenotypic variability advocate that other factors than genetics may modulate the disease, such as microRNAs (miRNAs). MiRNAs are small noncoding RNAs with a primary role in gene expression regulation and network of cellular processes. The implication of miRNAs in AC pathogenesis and their role as biomarkers for early disease detection or differential diagnosis has been the objective of multiple studies employing diverse designs and methodologies to detect miRNAs and measure their expression levels. Here we summarize experiments, evidence, and flaws of the different studies and hitherto knowledge of the implication of miRNAs in AC pathogenesis and diagnosis.

Arrhythmogenic Cardiomyopathy and Skeletal Muscle Dystrophies: Shared Histopathological Features and Pathogenic Mechanisms

Arrhythmogenic cardiomyopathy (ACM) is a heritable cardiac disease characterized by fibrotic or fibrofatty myocardial replacement, associated with an increased risk of ventricular arrhythmias and sudden cardiac death. Originally described as a disease of the right ventricle, ACM is currently recognized as a biventricular entity, due to the increasing numbers of reports of predominant left ventricular or biventricular involvement. Research over the last 20 years has significantly advanced our knowledge of the etiology and pathogenesis of ACM. Several etiopathogenetic theories have been proposed; among them, the most attractive one is the dystrophic theory, based on the observation of similar histopathological features between ACM and skeletal muscle dystrophies (SMDs), such as progressive muscular degeneration, inflammation, and tissue replacement by fatty and fibrous tissue. This review will describe the pathophysiological and molecular similarities shared by ACM with SMDs.

Current insights into LMNA cardiomyopathies: Existing models and missing LINCs

The nuclear lamina is a critical structural domain for the maintenance of genomic stability and whole-cell mechanics. Mutations in the LMNA gene, which encodes nuclear A-type lamins lead to the disruption of these key cellular functions, resulting in a number of devastating diseases known as laminopathies. Cardiomyopathy is a common laminopathy and is highly penetrant with poor prognosis. To date, cell mechanical instability and dysregulation of gene expression have been proposed as the main mechanisms driving cardiac dysfunction, and indeed discoveries in these areas have provided some promising leads in terms of therapeutics. However, important questions remain unanswered regarding the role of lamin A dysfunction in the heart, including a potential role for the toxicity of lamin A precursors in LMNA cardiomyopathy, which has yet to be rigorously investigated.

Incremental value of cardiac magnetic resonance imaging in arrhythmic risk stratification of arrhythmogenic right ventricular dysplasia/cardiomyopathy-associated desmosomal mutation carriers

OBJECTIVES

The aim of this study was to identify the incremental value and optimal role of cardiac magnetic resonance (CMR) imaging in arrhythmic risk stratification of arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C)-associated desmosomal mutation carriers without histories of sustained ventricular arrhythmia.

BACKGROUND

Risk stratification of ARVD/C mutation carriers is challenging.

METHODS

Sixty-nine patients (mean age 27.0 ± 15.3 years, 42% men) harboring ARVD/C-associated pathogenic mutations (83% plakophilin 2) without prior sustained ventricular arrhythmias were included. Electrocardiographic and 24-h Holter monitoring findings closest to presentation were analyzed for electrical abnormalities per revised task force criteria. CMR studies were done to identify abnormal cardiac structure and function according to the revised task force criteria.

RESULTS

Overall, 42 patients (61%) presented with electrical abnormalities on the basis of electrocardiography and Holter monitoring, of whom 20 (48%) had abnormal results on CMR. Only 1 of 27 patients (4%) without electrical abnormalities at initial evaluation had abnormal CMR results. Over a mean follow-up period of 5.8 ± 4.4 years, 11 patients (16%) experienced sustained ventricular arrhythmias, exclusively in patients with both electrical abnormalities (electrocardiography and/or Holter monitoring) and abnormal CMR results.

CONCLUSIONS

These results suggest that electrical abnormalities on electrocardiography and Holter monitoring precede detectable structural abnormalities in ARVD/C mutation carriers. Therefore, evaluation of cardiac structure and function using CMR is probably not necessary in the absence of baseline electrical abnormalities. Among ARVD/C mutation carriers, the presence of both electrical and CMR abnormalities identifies patients at high risk for events and thus patients who might benefit from prophylactic implantable cardioverter-defibrillator placement.

[Arrhythmogenic cardiomyopathy. Patterns of ventricular involvement using cardiac magnetic resonance]

INTRODUCTION AND OBJECTIVES

Biventricular arrhythmogenic cardiomyopathy and left dominant arrhythmogenic cardiomyopathy forms had recently been included in the spectrum of arrhythmogenic cardiomyopathy. The aim of the study was to describe, using cardiovascular magnetic resonance, the patterns of ventricular involvement as well as late gadolinium enhancement in these conditions.

METHODS

Medical databases and records from the cardiology units of 3 hospitals were reviewed to obtain data from patients with arrhythmogenic cardiomyopathy.

RESULTS

Twenty-six consecutive patients were included (40 [16] years, 16 males). Right ventricle involvement was present in 19 patients (73%). Among them, 13 patients (50%) had volumes over the upper limit of normality, 11 (42%) patients had late gadolinium enhancement in right ventricle and 6 patients (23%) had just mild involvement with wall motion abnormalities or microaneurysms. Left ventricle involvement was present in 24 patients (92%), all of them with late gadolinium enhancement. In 15 patients (57%) left ventricular systolic dysfunction was observed, and dilatation in 3 patients (11%). Late gadolinium enhancement was more frequent in the inferior, lateral, and inferolateral walls (65%, 57%, and 61% of patients, respectively) while septum was seldom affected (26% of cases). The pattern of late gadolinium enhancement was mainly subepicardial (46% of patients) or transmural (19%), and was intramyocardial in only 12% of the cases.

CONCLUSIONS

In this sample, left ventricle involvement is very common. The most frequent finding was left ventricular late gadolinium enhancement, while the least frequent was dilatation. The pattern of late gadolinium enhancement was more frequently subepicardial and located in the inferior and inferolateral walls.

Magnetic resonance imaging assessment of arrhythmogenic right ventricular cardiomyopathy/dysplasia in children

Arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) is a genetically determined disease that progresses continuously from conception and throughout life. ARVC/D manifests predominantly in young adulthood. Early identification of the concealed cases in childhood is of utmost importance for the prevention of sudden cardiac death later in life. Magnetic resonance imaging (MRI) is routinely requested in patients with a confirmed or suspected diagnosis of ARVC/D and in family members of the patients with ARVC/D. Although the utility of MRI in the assessment of ARVC/D is well recognized in adults, MRI is a low-yield test in children as the anatomical, histological, and functional changes are frequently subtle or not present in the early phase of the disease. MRI findings of ARVC/D include morphologic changes such as right ventricular dilatation, wall thinning, and aneurismal outpouchings, as well as abnormal tissue characteristics such as myocardial fibrosis and fatty infiltration, and functional abnormalities such as global ventricular dysfunction and regional wall motion abnormalities. Among these findings, regional wall motion abnormalities are the most reliable MRI findings both in children and adults, while myocardial fibrosis and fat infiltration are rarely seen in children. Therefore, an MRI protocol should be tailored according to the patient's age and compliance, as well as the presence of other findings, instead of using the protocol that is used for adults. We propose that MRI in children with ARVC/D should focus on the detection of regional wall motion abnormalities and global ventricular function by using a cine imaging sequence and that the sequences for myocardial fat and late gadolinium enhancement of the myocardium are reserved for those who show abnormal findings at cine imaging. Importantly, MRI should be performed and interpreted by experienced examiners to reduce the number of false positive and false negative readings.

Arrhythmogenic cardiomyopathy: etiology, diagnosis, and treatment

Arrhythmogenic right ventricular cardiomyopathy (ARVC) has a prevalence of at least 1 in 1000, is a leading cause of sudden cardiac death in people aged < or =35 years, and accounts for up to 10% of deaths from undiagnosed cardiac disease in the <65 age group. The classic form of the disease has an early predilection for the right ventricle, but recognition of left-dominant and biventricular subtypes has prompted proposal of the broader term arrhythmogenic cardiomyopathy. The clinical profile of the disease bridges the gap between the cardiomyopathies and inherited arrhythmia syndromes. The early "concealed" phase is characterized by propensity toward ventricular tachyarrhythmia in the setting of well-preserved morphology, histology, and ventricular function. As the disease progresses, however, myocyte loss, inflammation, and fibroadiposis become evident. Up to 40% of cases harbor rare variants in genes encoding components of the desmosome, specialized intercellular junctions that confer mechanical strength to cardiac and epithelial tissue, and may also participate in signaling networks. Phenotypic heterogeneity and the nonspecific nature of associated features complicate clinical diagnosis, which requires multipronged cardiovascular investigation rather than a single test. Development of a prospectively validated risk-stratification algorithm for the full disease spectrum remains the foremost clinical challenge.

[The utility of magnetic resonance imaging in the evaluation of arrhythmogenic right ventricular cardiomyopathy]

OBJECTIVE

To discuss the utility of magnetic resonance imaging in the evaluation of arrhythmogenic right ventricular cardiomyopathy.

METHODS

16 patients with suspicious ARVC joined this study from January 2005 to May 2008. CMR was performed on a 1.5 Tesla GE signa scanner. Short axis view, four-chamber view and long axis view of tow ventricle were acquired by white blood technique (Fast cine sequence). Short axis view and long axis view of right ventricle were acquired by black blood techniques (Double IRFSE and Triple IRFSE). The ARVC was diagnosed by MRI and golden criteria respectively.

RESULTS

Of the 16 patients, 11 were diagnosed ARVC by MRI, 9 were by golden criteria. 9 ARVC patients were manifested by thinning of RV wall, dilatation of the RV (8 cases) trabecular hypertrophy and disarray (6 cases), fat signal intensity of right ventricular(RV)wall in DIRFSE,irregular insular pieces or continuity breaking of myocardium in TIRFSE (3 cases) dilatation of the LV (2cases), a bit thickening of ventricular septum (1case), enlargement of the outflow of the right ventricular(RV) (2 cases) and ventricular aneurysm formation (2 cases).And the positions including apex of the right ventricle (4 cases), facies diaphragmatica (6 cases), anterior ventricle (4 cases), infundibulum (4 cases) and the papillary muscle of the RV (1case) were involved.

CONCLUSION

CMR is a specific and sensitive examination technique in diagnosing of ARVC, which could present structural, functional changes and the quality, degree, range of the disease. We should take this examination as the routine method if suspect ARVC in clinical.