An Updated Review on the Clinicopathologic Aspects of Arrhythmogenic Right Ventricular Cardiomyopathy An Updated Review on the Clinicopathologic Aspects of Arrhythmogenic Right Ventricular Cardiomyopathy

Decreased Expression of Plakophilin-2 and αT-Catenin in Arrhythmogenic Right Ventricular Cardiomyopathy: Potential Markers for Diagnosis

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a hereditary disease of the heart muscle. Clinical challenges remain, however, in identifying patients with ARVC in the early or concealed stages with subtle clinical manifestations. Therefore, we wanted to identify potential targets by immunohistochemical (IHC) analysis in comparison with controls. Pathogenic mutations were identified in 11 of 37 autopsied patients with ARVC. As observed from IHC analysis of the RV, expression of αT-catenin and plakophilin-2 is significantly decreased in autopsied patients with ARVC as compared to controls, and the decreased expression is consistent in patients with and without pathogenic mutations. Furthermore, ARVC specimens demonstrated a reduced localization of αT-catenin, desmocollin-2, desmoglein-2, desmoplakin, and plakophilin-2 on intercalated discs. These findings have been validated by comparing RV specimens obtained via endomyocardial biopsy between patients with ARVC and those without. The pathogenic mutation was present in 3 of 5 clinical patients with ARVC. In HL-1 myocytes, siRNA was used to knockdown CTNNA3, and western blotting analysis demonstrated that the decline in αT-catenin expression was accompanied by a significant decline in the expression of plakophilin-2. The aforementioned effect was directed towards protein degradation rather than mRNA stability. Plakophilin-2 expression decreases concurrently with the decline in CTNNA3 expression. Therefore, the expression of αT-catenin and plakophilin-2 could be potential surrogates for the diagnosis of ARVC.

Incorporation of desmocollin-2 into the plasma membrane requires N-glycosylation at multiple sites

Desmocollin‐2 (DSC2) is a desmosomal protein of the cadherin family. Desmosomes are multiprotein complexes, which are involved in cell adhesion of cardiomyocytes and of keratinocytes. The molecular structure of the complete extracellular domain (ECD) of DSC2 was recently described, revealing three disulfide bridges, four N‐glycosylation sites, and four O‐mannosylation sites. However, the functional relevance of these post‐translational modifications for the protein trafficking of DSC2 to the plasma membrane is still unknown. Here, we generated a set of DSC2 mutants, in which we systematically exchanged all N‐glycosylation sites, O‐mannosylation sites, and disulfide bridges within the ECD and investigated the resulting subcellular localization by confocal laser scanning microscopy. Of note, all single and double N‐glycosylation‐ deficient mutants were efficiently incorporated into the plasma membrane, indicating that the absence of these glycosylation sites has a minor effect on the protein trafficking of DSC2. However, the exchange of multiple N‐glycosylation sites resulted in intracellular accumulation. Colocalization analysis using cell compartment trackers revealed that N‐glycosylation‐ deficient DSC2 mutants were retained within the Golgi apparatus. In contrast, elimination of the four O‐mannosylation sites or the disulfide bridges in the ECD has no obvious effect on the intracellular protein processing of DSC2. These experiments underscore the importance of N‐glycosylation at multiple sites of DSC2 for efficient intracellular transport to the plasma membrane.

Sudden cardiac death owing to arrhythmogenic right ventricular cardiomyopathy: Two case reports and systematic literature review

BACKGROUND AND OBJECTIVE

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is increasingly recognized in forensic practice with controversial diagnosis. Here we described the epidemiological characteristics and reported the pathogenetic mechanism, diagnostic challenges, and forensic implications of Chinese ARVC autopsy cases.

METHODS

Two cases of sudden cardiac death owing to ARVC were reported. Retrospective analysis were performed on such 2 cases and 45 cases of separate ARVC complete autopsy case reports through Chinese literature databases in the last 30 years.

RESULTS

There were 27 males and 20 females, and the mean age at death was 35 years. Sudden cardiac death was the first manifestation observed in most patients, with no previous family and medical history. Exercise, acute stress, increased cardiac workload, and ethanol are frequently involved. The mean heart weight was 393 g (range, 240-590 g), and 10 cases had relative heart hypertrophy. Microscopic abnormalities included replacement of myocardium by adipose infiltration in 68.09% cases and fibroadipose in 31.91% cases; 80.85% cases were restricted to the right ventricle (RV), whereas biventricular subtype was seen in the remaining 19.15% cases. The preliminary quantitative histology showed 60.7% of fat tissues, 12.1% of fibrosis, and 27.2% residual myocytes in RV. Inflammatory cell infiltration was found in 25.53% cases, but myocyte necrosis was found in only 1 case. In 10.64% of cases, cardiac conduction was infiltrated by fibrosis, adipose, or both.

CONCLUSION

In this review, the most characteristic and distinct histopathologic features that are diagnostic or highly suggestive of ARVC for forensic pathologists were identified. Combining gross and histological examinations with postmortem genetic analysis is recommended for identifying ARVC.

Seasonal variation in the frequency of sudden cardiac death and ventricular tachyarrhythmia in patients with arrhythmogenic right ventricular dysplasia/cardiomyopathy: the effect of meteorological factors

BACKGROUND

Sudden cardiac death (SCD) is the most catastrophic presentation in patients with arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C).

OBJECTIVES

To investigate the seasonal variations in the frequency of SCD and ventricular tachyarrhythmia in patients with AVRD/C and to elucidate the meteorological factors that trigger these events.

METHODS

From 1998 to 2012, we enrolled 88 consecutive patients with ARVD/C from Taipei City. The cohort included 20 living patients who received implantable cardioverter-defibrillator (ICD) and 68 autopsied patients with SCD from the Taiwan National Forensic Institute registry. The baseline clinical characteristics, seasonal distribution, and associated meteorological factors were explored to predict the occurrences of events, which include appropriate ICD interventions and SCD.

RESULTS

There were 106 events, including 38 (35.8%, 1.9 episodes per patient) appropriate ICD interventions in living patients with ARVD/C and 68 (64.2%) SCD events. The seasonal peak occurred predominantly in summer (P < .05) in both groups. For meteorological factors, the onset of event was associated with higher average daily temperature and longer sunshine duration. The variation in humidity within 3 days of events was significantly increased. After multivariate logistic regression analysis, higher average daily temperature and larger variation in humidity were associated with increase in events (odds ratio 1.23, 95% confidence interval 1.16-1.31, P < .001, and odds ratio 1.19, 95% confidence interval 1.15-1.23, P < .001, respectively).

CONCLUSIONS

There was seasonal variation with a summer peak in the occurrence of ventricular arrhythmias and SCD in patients with ARVD/C. Meteorological factors including higher temperature and larger variation in humidity within 3 days of events were independently associated with the development of events.

Sudden cardiac death due to arrhythmogenic right ventricular cardiomyopathy and cystic tumor of the AV node

An 18-year-old white male collapsed suddenly in his home and died. At autopsy, the right ventricle of the decedent was noted to be dilated with marked thinning of the wall focally. Microscopically, the myocardium of the right ventricle was noted to be significantly thinned focally, where transmural infiltration with fibroadipose tissue was noted. Depending on the criteria utilized to render such a diagnosis, these findings were consistent with arrhythmogenic right ventricular cardiomyopathy (ARVC). Subsequent microscopic examination of the SA and AV node, however, revealed the presence of a cystic tumor of the AV node (CTAVN), a known cause of sudden death from arrhythmia. The case represents the first reported case of ARVC and CTAVN occurring together in the same individual.

Mutations with pathogenic potential in proteins located in or at the composite junctions of the intercalated disk connecting mammalian cardiomyocytes: a reference thesaurus for arrhythmogenic cardiomyopathies and for Naxos and Carvajal diseases

In the past decade, an avalanche of findings and reports has correlated arrhythmogenic ventricular cardiomyopathies (ARVC) and Naxos and Carvajal diseases with certain mutations in protein constituents of the special junctions connecting the polar regions (intercalated disks) of mature mammalian cardiomyocytes. These molecules, apparently together with some specific cytoskeletal proteins, are components of (or interact with) composite junctions. Composite junctions contain the amalgamated fusion products of the molecules that, in other cell types and tissues, occur in distinct separate junctions, i.e. desmosomes and adherens junctions. As the pertinent literature is still in an expanding phase and is obviously becoming important for various groups of researchers in basic cell and molecular biology, developmental biology, histology, physiology, cardiology, pathology and genetics, the relevant references so far recognized have been collected and are presented here in the following order: desmocollin-2 (Dsc2, DSC2), desmoglein-2 (Dsg2, DSG2), desmoplakin (DP, DSP), plakoglobin (PG, JUP), plakophilin-2 (Pkp2, PKP2) and some non-desmosomal proteins such as transmembrane protein 43 (TMEM43), ryanodine receptor 2 (RYR2), desmin, lamins A and C, striatin, titin and transforming growth factor-β3 (TGFβ3), followed by a collection of animal models and of reviews, commentaries, collections and comparative studies.

Usefulness of immunostaining for plakoglobin as a diagnostic marker of arrhythmogenic right ventricular cardiomyopathy

The clinical diagnosis of arrhythmogenic right ventricular cardiomyopathy (ARVC) is often challenging due to phenotypic variation, reduced/age-related penetrance, and lack of a diagnostic test. A single report has suggested quantitative myocardial immunoanalysis for the desmosomal protein plakoglobin as a diagnostic test with high sensitivity and specificity. We performed immunohistochemistry for plakoglobin and a control protein on myocardial biopsies with fibrofatty replacements from 50 consecutive, unrelated patients. The clinical, genetic, and immunohistochemical data were evaluated by independent observers in a blinded manner. The immunohistochemical and clinical diagnoses were compared and the sensitivity, specificity, and predictive values calculated. Our analysis showed 37 samples (74%) with a reduced immunosignal for plakoglobin. Of the 34 patients with a clinical diagnosis of ARVC, 29 displayed a reduced plakoglobin signal. Of the 14 patients with a clinical diagnosis other than ARVC, 6 displayed a reduced signal. Two patients were excluded from further analysis. A sensitivity of 85%, a specificity of 57%, a positive predictive value of 83%, and a negative predictive value of 62% were found. In conclusion, immunohistochemical analysis for plakoglobin, applied as a diagnostic test for ARVC, seems associated with a relatively high sensitivity, but limited specificity, and although additional validation is required, we advocate caution in basing clinical decision-making on the proposed diagnostic test.

What is Sudden Cardiac Death?

Sudden cardiac death (SCD) is a rapid, unexpected death due to cardiac causes. The differential diagnosis includes diseases from all four structural divisions of the heart: the blood vessels, myocardium, valves, and conduction system. Although ischemic heart disease is a common cause of SCD, acute myocardial infarcts and/or coronary thromboses are not always detected and are not required to make the diagnosis of death due to atherosclerotic coronary disease. Some people die suddenly from heart disease with a grossly and microscopically normal heart. Molecular analysis of some of these autopsy-negative, sudden unexplained deaths (SUD) may detect putative cardiac channel mutations.

There are three SCD scenarios that are of particular interest to forensic pathologists: sudden cardiac deaths in young athletes, during criminal altercations (homicide by heart attack), and in other hostile environments. In young athletes, most sudden deaths involve cardiac disease and include cardiomyopathies, congenital coronary artery anomalies, myocarditis, and channelopathies. One must, however, consider other causes in these deaths (e.g., commotio cordis, hyperthermia, sickle cell trait). Homicide-by-heart-attack deaths are those in which the cause of death is an acute exacerbation of underlying cardiac disease, however, the manner is homicide because a criminal act triggered the lethal pathologic cascade. A sudden cardiac arrest may occur in hostile locations with resultant trauma (e.g., while driving a motor vehicle). When the event occurs in the bathtub or other body of water, the question of whether the person died naturally from heart disease or unnaturally from trauma (e.g., drowning) often arises. One should not be mislead by the initial physical surroundings of the death (i.e., in a motor vehicle collision, or swimming pool) and fail to distinguish a natural sudden death from an accidental one.

Ablation of ventricular arrhythmias in arrhythmogenic right ventricular dysplasia/cardiomyopathy: arrhythmia-free survival after endo-epicardial substrate based mapping and ablation

BACKGROUND

In patients with arrhythmogenic right ventricular dysplasia/cardiomyopathy, freedom from ventricular arrhythmias (VAs) after endocardial ablation is limited. We compared the long-term freedom from recurrent VAs by using endocardial-alone ablation versus endo-epicardial substrate-based ablation.

METHODS AND RESULTS

Forty-nine patients with arrhythmogenic right ventricular dysplasia/cardiomyopathy undergoing ablation of ventricular tachycardia (VT) were divided into 2 groups: endocardial-alone ablation (group 1, n = 23) and endo-epicardial ablation (group 2, n = 26). All patients had an implantable cardioverter-defibrillator (ICD). Conventional and 3D mappings were used to determine the mechanism of induced VTs and to identify area of "scar" or "abnormal" myocardium. All critical sites responsible for VTs and points with "abnormal" potential were targeted for ablation from endocardium (group 1) or from both endocardium and epicardium (group 2). The procedural end point was noninducibility of sustained, monomorphic VT with isoproterenol. The presence of frequent premature ventricular contractions at the end of ablation was recorded. Patients were followed up by ECG, Holter, and ICD interrogation. After a follow-up of at least 3 years, freedom from VAs or ICD therapy was 52.2% (12/23) in group 1 and 84.6% (22/26) in group 2 (P = 0.029), with 21.7% (5/23) and 69.2% (18/26) patients off antiarrhythmic drugs (P < 0.001), respectively. Compared with patients with no premature ventricular contractions after ablation, patients with frequent premature ventricular contractions after ablation were more likely to have VA recurrence/ICD therapy [3/33 (9%) versus 12/16 (75%); log-rank P<0.001].

CONCLUSIONS

An endo-epicardial-based ablation strategy achieves higher long-term freedom from recurrent VAs off antiarrhythmic therapy in patients with arrhythmogenic right ventricular dysplasia/cardiomyopathy when compared with endocardial-alone ablation. The presence of ≥ 10 premature ventricular contractions per minute after ablation is associated with more VA recurrence.

Diagnostic utility of immunohistochemical panel in various thyroid pathologies

BACKGROUND

For management of thyroid nodules, distinction between benign and malignant tumours is essential. The study was performed to evaluate the diagnostic value of molecular markers in different thyroid tumours.

MATERIALS AND METHODS

Immunohistochemistry for CD56, HBME-1, COX-2, Ki-67, p53 and E-cadherin (E-CAD) was performed in 113 benign and 35 malignant thyroid lesions including 36 follicular adenomas (FA), 77 colloid goitres, 26 papillary thyroid carcinomas (PTC) and 9 follicular carcinomas (FC). The results were scored semiquantitatively by staining intensity (0-3 scale) and percentage of positive cells.

RESULTS

PTC was characterised by decreased E-CAD and CD56 expression in contrast to surrounding benign thyroid tissues. HBME-1 expression was absent in benign thyroid tissues but was notably high in PTC and occasionally in FC. The expression of E-CAD and CD56 in FA was significantly higher than in the surrounding thyroid tissues. No expression of p53 was found in any group. The expression of COX-2 was low in all lesions. The proliferation activity by Ki-67 was generally low; however, it was significantly higher in cancers.

CONCLUSIONS

The panel consisting of three markers, HBME-1, E-CAD and CD56, can be recommended as an adjunct to morphology criteria. HBME-1 is found in malignant lesions only and is the most sensitive and specific single marker in PTC. Decreased expression of E-CAD and CD56 distinguishes PTC from FA and FC. Both FA and FC are characterised by high expression of E-CAD and CD56. The practical use of Ki-67 is difficult due to low values. The role of adhesion factors in thyroid malignancies may be superior in comparison with cell proliferation.