Nikos Protonotarios

Diagnosis of arrhythmogenic right ventricular cardiomyopathy/dysplasia: proposed modification of the Task Force Criteria.

BACKGROUND In 1994, an International Task Force proposed criteria for the clinical diagnosis of arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) that facilitated recognition and interpretation of the frequently nonspecific clinical features of ARVC/D. This enabled confirmatory clinical diagnosis in index cases through exclusion of phenocopies and provided a standard on which clinical research and genetic studies could be based. Structural, histological, electrocardiographic, arrhythmic, and familial features of the disease were incorporated into the criteria, subdivided into major and minor categories according to the specificity of their association with ARVC/D. At that time, clinical experience with ARVC/D was dominated by symptomatic index cases and sudden cardiac death victims-the overt or severe end of the disease spectrum. Consequently, the 1994 criteria were highly specific but lacked sensitivity for early and familial disease. METHODS AND RESULTS Revision of the diagnostic criteria provides guidance on the role of emerging diagnostic modalities and advances in the genetics of ARVC/D. The criteria have been modified to incorporate new knowledge and technology to improve diagnostic sensitivity, but with the important requisite of maintaining diagnostic specificity. The approach of classifying structural, histological, electrocardiographic, arrhythmic, and genetic features of the disease as major and minor criteria has been maintained. In this modification of the Task Force criteria, quantitative criteria are proposed and abnormalities are defined on the basis of comparison with normal subject data. CONCLUSIONS The present modifications of the Task Force Criteria represent a working framework to improve the diagnosis and management of this condition. Clinical Trial Registration clinicaltrials.gov Identifier: NCT00024505.

Diagnosis of Arrhythmogenic Right Ventricular Cardiomyopathy/Dysplasia Proposed Modification of the Task Force Criteria

Background— In 1994, an International Task Force proposed criteria for the clinical diagnosis of arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) that facilitated recognition and interpretation of the frequently nonspecific clinical features of ARVC/D. This enabled confirmatory clinical diagnosis in index cases through exclusion of phenocopies and provided a standard on which clinical research and genetic studies could be based. Structural, histological, electrocardiographic, arrhythmic, and familial features of the disease were incorporated into the criteria, subdivided into major and minor categories according to the specificity of their association with ARVC/D. At that time, clinical experience with ARVC/D was dominated by symptomatic index cases and sudden cardiac death victims—the overt or severe end of the disease spectrum. Consequently, the 1994 criteria were highly specific but lacked sensitivity for early and familial disease. Methods and Results— Revision of the diagnostic criteria provides guidance on the role of emerging diagnostic modalities and advances in the genetics of ARVC/D. The criteria have been modified to incorporate new knowledge and technology to improve diagnostic sensitivity, but with the important requisite of maintaining diagnostic specificity. The approach of classifying structural, histological, electrocardiographic, arrhythmic, and genetic features of the disease as major and minor criteria has been maintained. In this modification of the Task Force criteria, quantitative criteria are proposed and abnormalities are defined on the basis of comparison with normal subject data. Conclusions— The present modifications of the Task Force Criteria represent a working framework to improve the diagnosis and management of this condition. Clinical Trial Registration— URL: http://www.clinicaltrials.gov. Unique identifier: NCT00024505.

Identification of a deletion in plakoglobin in arrhythmogenic right ventricular cardiomyopathy with palmoplantar keratoderma and woolly hair (Naxos disease)

BACKGROUND Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an autosomal dominant heart muscle disorder that causes arrhythmia, heart failure, and sudden death. Previously we mapped the genetic locus for the triad of autosomal recessive ARVC, palmoplantar keratoderma, and woolly hair (Naxos disease) to chromosome 17q21, in which the gene for plakoglobin is encoded. This protein is a key component of desmosomes and adherens junctions, and is important for the tight adhesion of many cell types, including those in the heart and skin. METHODS We studied 19 individuals with Naxos disease, as well as unaffected family members and unrelated individuals from the neighbouring Greek islands of Naxos and Milos. Gene sequence was determined by reverse transcriptase PCR from RNA isolated from the skin of an affected individual and mutations in other cases were confirmed by restriction-enzyme analysis. FINDINGS A homozygous 2 base pair deletion in the plakoglobin gene was identified only in the 19 affected individuals. This deletion caused a frameshift and premature termination of the protein, which was shown by western blot analysis. 29 clinically unaffected family members were heterozygous for the mutation; 20 unrelated individuals from Naxos and 43 autosomal dominant ARVC probands were homozygous for the normal allele. INTERPRETATION The finding of a deletion in plakoglobin in ARVC suggests that the proteins involved in cell-cell adhesion play an important part in maintaining myocyte integrity, and when junctions are disrupted, cell death, and fibrofatty replacement occur. Therefore, the discovery of a mutation in a protein with functions in maintaining cell junction integrity has important implications for other dominant forms of ARVC, related cardiomyopathies, and other cutaneous diseases.

A New Diagnostic Test for Arrhythmogenic Right Ventricular Cardiomyopathy

BACKGROUND The diagnosis of arrhythmogenic right ventricular cardiomyopathy (ARVC) can be challenging because the clinical presentation is highly variable and genetic penetrance is often low. METHODS To determine whether a change in the distribution of desmosomal proteins can be used as a sensitive and specific diagnostic test for ARVC, we performed immunohistochemical analysis of human myocardial samples. RESULTS We first tested myocardium from 11 subjects with ARVC; of these samples, 8 had desmosomal gene mutations. We also tested myocardium obtained at autopsy from 10 subjects with no clinical or pathological evidence of heart disease as control samples. All ARVC samples but no control samples showed a marked reduction in immunoreactive signal levels for plakoglobin (also known as gamma-catenin), a protein that links adhesion molecules at the intercalated disk to the cytoskeleton. Other desmosomal proteins showed variable changes, but signal levels for the nondesmosomal adhesion molecule N-cadherin were normal in all subjects with ARVC. To determine whether a diminished plakoglobin signal level was specific for ARVC, we analyzed myocardium from 15 subjects with hypertrophic, dilated, or ischemic cardiomyopathies. In every sample, levels of N-cadherin and plakoglobin signals at junctions were indistinguishable from those in control samples. Finally, we performed blinded immunohistochemical analysis of heart-biopsy samples from the Johns Hopkins ARVC registry. We made the correct diagnosis in 10 of 11 subjects with definite ARVC on the basis of clinical criteria and correctly ruled out ARVC in 10 of 11 subjects without ARVC, for a sensitivity of 91%, a specificity of 82%, a positive predictive value of 83%, and a negative predictive value of 90%. The plakoglobin signal level was reduced diffusely in ARVC samples, including those obtained in the left ventricle and the interventricular septum. CONCLUSIONS Routine immunohistochemical analysis of a conventional endomyocardial-biopsy sample appears to be a highly sensitive and specific diagnostic test for ARVC.

Gene for Arrhythmogenic Right Ventricular Cardiomyopathy With Diffuse Nonepidermolytic Palmoplantar Keratoderma and Woolly Hair (Naxos Disease) Maps to 17q21

BACKGROUND Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a heart muscle disease of unknown etiology that causes arrhythmias, heart failure, and sudden death. Diagnosis can be difficult, and this hampers investigation of its molecular basis. Forms of ARVC in which gene penetrance and disease expression are greater should facilitate genetic study. We undertook a clinical and genetic investigation of Naxos disease, originally described by Protonotarios in 1986. This disease constitutes the triad of ARVC, diffuse nonepidermolytic palmoplantar keratoderma, and woolly hair. METHODS AND RESULTS We evaluated the population of Naxos, Greece, to identify probands, which was followed by family screening. Twenty-one affected persons from 9 families of 150 persons were identified. Linkage analysis was performed with microsatellite markers. The disease locus mapped to 17q21. A peak 2-point LOD score of 3.62 at theta=0.0 was found with a marker within intron 4 of the keratin 9 gene, a member of the type I (acidic) keratin family. A preserved homozygous disease haplotype was identified. Haplotype analysis delimited the disease interval. CONCLUSIONS Hair and skin abnormalities were found to be reliable markers of subsequent heart disease. This suggests the presence of a single mutant gene with novel cardiac, skin, and hair function or two or more tightly linked disease genes. Recessive inheritance of Naxos disease and a founder effect were demonstrated. Identification of a fully informative genetic marker linked to the disease and uncommon in the background population may be of use as a test to identify disease gene carriers.

Genotype-phenotype assessment in autosomal recessive arrhythmogenic right ventricular cardiomyopathy (Naxos disease) caused by a deletion in plakoglobin.

OBJECTIVES The purpose of this study was to examine the genotype-phenotype relation with respect to penetrance, age and severity of expression, disease progression and prognosis in a recessively inherited arrhythmogenic right ventricular cardiomyopathy (ARVC). BACKGROUND Naxos disease is a recessively inherited ARVC caused by a mutation in the gene encoding plakoglobin (cell adhesion protein) in which the cardiac phenotype is associated with palmoplantar keratoderma and woolly hair. METHODS Twelve families with Naxos disease underwent cardiac and molecular genetic investigation. Serial cardiac assessment with annual resting 12-lead and 24-h ambulatory electrocardiogram (ECG) and two-dimensional echocardiography was performed during 1 to 16 years, median 7 +/- 6 years in all 78 surviving members. RESULTS Twenty-eight surviving members were homozygous and 40 were heterozygous for the mutation. All adults who were homozygous (n = 26) fulfilled the diagnostic criteria for ARVC, the youngest by the age of 13 years. In eight who were heterozygous, minor ECG or echocardiographic abnormalities were observed. Of the 26 subjects who were affected homozygotes, 92% showed ECG abnormalities, 92% ventricular arrhythmias, 100% right ventricular structural alterations and 27% left ventricular involvement. During follow-up (10 +/- 6 years), 16 (62%) developed structural progression, 12 (46%) arrhythmic events and 7 (27%) heart failure. The annual disease-related and sudden death mortality was 3% and 2.3%, respectively. CONCLUSIONS Autosomal recessive ARVC caused by a mutation in plakoglobin was 100% penetrant by adolescence. Affected subjects who were homozygous experienced progressive disease with adverse prognosis. A minority of subjects who were heterozygous showed minor ECG/echocardiographic changes, but clinically significant disease did not develop.

Treatment of Arrhythmogenic Right Ventricular Cardiomyopathy/Dysplasia: An International Task Force Consensus Statement

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Altered Desmosomal Proteins in Granulomatous Myocarditis and Potential Pathogenic Links to Arrhythmogenic Right Ventricular Cardiomyopathy

Background— Immunoreactive signal for the desmosomal protein plakoglobin (&ggr;-catenin) is reduced at cardiac intercalated disks in patients with arrhythmogenic right ventricular cardiomyopathy (ARVC), a highly arrhythmogenic condition caused by mutations in genes encoding desmosomal proteins. Previously, we observed a false-positive case in which plakoglobin signal was reduced in a patient initially believed to have ARVC but who actually had cardiac sarcoidosis. Sarcoidosis can masquerade clinically as ARVC but has not been previously associated with altered desmosomal proteins. Methods and Results— We observed marked reduction in immunoreactive signal for plakoglobin at cardiac myocyte junctions in patients with sarcoidosis and giant cell myocarditis, both highly arrhythmogenic forms of myocarditis associated with granulomatous inflammation. In contrast, plakoglobin signal was not depressed in lymphocytic (nongranulomatous) myocarditis. To determine whether cytokines might promote dislocation of plakoglobin from desmosomes, we incubated cultures of neonatal rat ventricular myocytes with selected inflammatory mediators. Brief exposure to low concentrations of interleukin (IL)-17, tumor necrosis factor-&agr; (TNF-&agr;), and IL-6 (cytokines implicated in granulomatous myocarditis) caused translocation of plakoglobin from cell-cell junctions to intracellular sites, whereas other potent cytokines implicated in nongranulomatous myocarditis had no effect, even at much higher concentrations. We also observed myocardial expression of IL-17 and TNF-&agr; and elevated levels of serum inflammatory mediators, including IL-6R, IL-8, monocyte chemoattractant protein 1, and macrophage inflammatory protein 1&bgr;, in patients with ARVC (all P<0.0001 compared with controls). Conclusions— The results suggest novel disease mechanisms involving desmosomal proteins in granulomatous myocarditis and implicate cytokines, perhaps derived in part from the myocardium, in disruption of desmosomal proteins and arrhythmogenesis in ARVC.

Arrhythmogenic right ventricular cardiomyopathy/dysplasia on the basis of the revised diagnostic criteria in affected families with desmosomal mutations

Aims To evaluate arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) in affected families with desmosome mutations on the basis of the recently revised Task Force Criteria (TFC). Methods and results One hundred and three consecutive carriers of pathogenic desmosome mutations and 102 mutation-negative relatives belonging to 22 families with dominant and 14 families with recessive ARVC/D were evaluated according to the original and revised TFC. Serial cardiac assessment with 12-lead, signal-averaged, and 24 h ambulatory ECG and two-dimensional echocardiography was performed. Clinical events and outcome were prospectively analysed up to 24 years (median 4 years). With the revised criteria, 16 carriers were newly diagnosed on the basis of ECG abnormalities in 100%, ventricular arrhythmias in 79%, and functional/structural alterations in 31%, increasing diagnostic sensitivity from 57 to 71% (P = 0.001). Task Force Criteria specificity improved from 92 to 99% (P = 0.016). In dominant mutation carriers, penetrance changed significantly (61 vs. 42%, P = 0.001); no changes were observed in recessive homozygous carriers (97 vs. 97%, P = 1.00). Affected carriers according to the revised TFC (n = 73) had 12-lead ECG abnormalities in 96%, ventricular arrhythmias in 91%, and functional/structural alterations fulfilling echocardiographic criteria in 76%. Cumulative and event-free survival did not differ significantly between dominant and recessive affected carriers, being at 78.6 vs. 76 and 51.7 vs. 55.4%, respectively, by the age of 40 years. Conclusion Revised TFC increased diagnostic sensitivity particularly in dominant ARVC/D. Serial family evaluation may rely on electrocardiography which seems to have the best diagnostic utility particularly in early disease that is not detectable by two-dimensional echocardiography.

Arrhythmogenic right ventricular dysplasia, a cell-adhesion cardiomyopathy: insights into disease pathogenesis from preliminary genotype-phenotype assessment

Arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVC) is a genetically determined heart muscle disorder presenting clinically with even lethal ventricular arrhythmias, particularly in the young and athletes. It is reported familial with recessive and most commonly dominant inheritance. Disease-causing genes are increasingly recognised among desmosomal proteins plakoglobin, desmoplakin, plakophilin2, and desmoglein2 displaying phenotypic heterogeneity. Mutations in the plakoglobin and desmoplakin genes have been identified to underlie recessive ARVC associated with woolly hair and palmoplantar keratoderma (Naxos disease), while mutations in plakophilin2, desmoglein2 as well as desmoplakin have been identified to underlie the dominant non-syndromic form. Preliminary genotype–phenotype assessment indicates that mutations affecting the outer dense plaque of desmosome (desmoglein2, plakoglobin, plakophilin2 and the N-terminal of desmoplakin) result in ARVC with the ordinary described phenotype. However, mutations at the inner dense plaque, particularly affecting the desmin-binding site of desmoplakin, may result in ARVC with predominantly left ventricular involvement and clinical overlapping with dilated cardiomyopathy. The interesting finding of abnormal distribution of plakoglobin, independently of the primarily affected protein, might suggest a common pathway for plakoglobin in ARVC pathogenesis.