Histological evidence of left ventricular involvement in arrhythmogenic right ventricular dysplasia

Some previously neglected examples of arrhythmogenic right ventricular dysplasia/cardiomyopathy and frequency of its various reported manifestations

Four patients are described with either parchment-like thinning or partial but extensive myocyte depletion with severe fatty or fibrofatty infiltration of the free wall of the right ventricle in its outflow tract, including 2 previously reported patients who also had focal parchment-like thinning of the left ventricular free wall. Three had documented ventricular tachycardia, and the remaining patient had sudden death as his first and only manifestation of heart disease. Three patients had severe heart failure: in 1, it was fatal, and the other 2 underwent cardiac transplantation. Necropsy cases of parchment-heart syndrome before 1980 are reviewed, as well as large series of cases with arrhythmogenic right ventricular dysplasia (ARVD) reported subsequently. It is suggested that ARVD is not an ideal name for this condition, because malignant ventricular arrhythmias are not universal, the left ventricular free wall and/or ventricular septum are sometimes involved, and the name "ARVD" neglects the fact that severe heart failure may be prominent in these patients. The right ventricular wall can be thin or parchment-like, or it may not be thinned but consist mainly of adipose tissue with or without focal fibrous tissue and a few islands of myocytes. Nevertheless, because the name "ARVD" has been commonly used and recognized for >30 years, it is probably best retained for this condition.

Compound and digenic heterozygosity contributes to arrhythmogenic right ventricular cardiomyopathy

OBJECTIVES

The aim of this study was to define the genetic basis of arrhythmogenic right ventricular cardiomyopathy (ARVC).

BACKGROUND

Arrhythmogenic right ventricular cardiomyopathy, characterized by right ventricular fibrofatty replacement and arrhythmias, causes sudden death. Autosomal dominant inheritance, reduced penetrance, and 7 desmosome-encoding causative genes are known. The basis of low penetrance is poorly understood.

METHODS

Arrhythmogenic right ventricular cardiomyopathy probands and family members were enrolled, blood was obtained, lymphoblastoid cell lines were immortalized, deoxyribonucleic acid was extracted, polymerase chain reaction (PCR) amplification of desmosome-encoding genes was performed, PCR products were sequenced, and diseased tissue samples were studied for intercellular junction protein distribution with confocal immunofluorescence microscopy and antibodies against key proteins.

RESULTS

We identified 21 variants in plakophilin-2 (PKP2) in 38 of 198 probands (19%), including missense, nonsense, splice site, and deletion/insertion mutations. Pedigrees showed wide intra-familial variability (severe early-onset disease to asymptomatic individuals). In 9 of 38 probands, PKP2 variants were identified that were encoded in trans (compound heterozygosity). The 38 probands hosting PKP2 variants were screened for other desmosomal genes mutations; second variants (digenic heterozygosity) were identified in 16 of 38 subjects with PKP2 variants (42%), including desmoplakin (DSP) (n = 6), desmoglein-2 (DSG2) (n = 5), plakophilin-4 (PKP4) (n = 1), and desmocollin-2 (DSC2) (n = 1). Heterozygous mutations in non-PKP 2 desmosomal genes occurred in 14 of 198 subjects (7%), including DSP (n = 4), DSG2 (n = 5), DSC2 (n = 3), and junctional plakoglobin (JUP) (n = 2). All variants occurred in conserved regions; none was identified in 700 ethnic-matched control subjects. Immunohistochemical analysis demonstrated abnormalities of protein architecture.

CONCLUSIONS

These data suggest that the genetic basis of ARVC includes reduced penetrance with compound and digenic heterozygosity. Disturbed junctional cytoarchitecture in subjects with desmosomal mutations confirms that ARVC is a disease of the desmosome and cell junction.

Role of cardiovascular magnetic resonance imaging in arrhythmogenic right ventricular dysplasia

Arrhythmogenic right ventricular dysplasia (ARVD) is a genetic cardiomyopathy characterized clinically by ventricular arrhythmias and progressive right ventricular (RV) dysfunction. The histopathologic hallmark is fibro-fatty replacement of RV myocardium. It is inherited in an autosomal pattern with variable penetrance. ARVD is unique in that it most commonly presents in young, otherwise healthy and highly athletic individuals. The cause of ARVD is not well-known but recent evidence suggests strongly that it is a disease of desmosomal dysfunction. The disease involvement is not limited only to the RV as left ventricle (LV) has also been reportedly affected. Diagnosis of ARVD is challenging and is currently based upon a multi-disciplinary work-up of the patient as defined by the Task Force. Currently, implanted cardioverter defibrillators (ICD) are routinely used to prevent sudden death in patients with ARVD. Cardiovascular MR is an important non-invasive diagnostic modality that allows both qualitative and quantitative evaluation of RV. This article reviews the genetics of ARVD, current status and role of CMR in the diagnosis of ARVD and LV involvement in ARVD.

Right ventricular cardiomyopathy accompanied by protein-losing enteropathy and chylous effusion

Severe right-side heart failure developed in a 47-year-old Japanese woman who suffered from hypoalbuminemia and a massive right side chylous pleural effusion. She had been diagnosed as having protein-losing enteropathy with right ventricular cardiomyopathy. Autopsy showed congenital anomalies of the lymph ducts and abnormal deposition of fibrous and fatty tissue in the right ventricular myocardium. The clinical and pathological findings are consistent with the nonarrythmogenic form of the arrythmogenic right ventricular dysplasia.

A case of arrhythmogenic right ventricular dysplasia with left and right ventricular hypofunction in an elderly subject--long-term follow-up

A 72-year-old man was admitted with palpitations caused by sustained ventricular tachycardia. He had been followed for 27 years, with admissions on 7 occasions, on account of ventricular tachycardias, atrial fibrillation, and congestive heart failure. Electrophysiologic examination detected 2 points of origin of ventricular tachycardia in the right and left ventricles. During the examination a myocardial infarction led to death. At autopsy, most areas of the right ventricle and the left ventricular apex were found to have been replaced by fatty tissue, pointing to severe fatty infiltration into the myocardium. Thus, this patient represented a unique cause of arrhythmogenic right ventricular dysplasia (ARVD) with severe fatty degeneration causing progression of ARVD. It is important that a diagnosis of ARVD is made carefully and rigorously in elderly subjects.

The arrhythmogenic right ventricle. Dysplasia versus cardiomyopathy

Twenty-four patients presenting with arrhythmogenic right ventricular dysplasia/cardiomyopathy (ventricular tachycardia of right ventricular origin associated with structural abnormalities of the right ventricle) were divided into two groups with left ventricular ejection fraction (LVEF) above or below 45%. The distribution of LVEF in the group with LVEF below 45% was comparable with the distribution in 6 patients with idiopathic dilated cardiomyopathy who had ventricular tachycardia originating in the left ventricle (P = 0.2). They also had the same unfavorable long-term prognosis. Therefore, it is suggested that the term, arrhythmogenic right ventricular cardiomyopathy (ARVC), be restricted to patients with a LVEF below 45%. Histological data obtained in the ARVC group showed signs of acute or chronic myocarditis (in the right and left ventricles). It can be hypothesized that patients with arrhythmogenic right ventricular dysplasia (ARVD) may be prone to develop infectious myocarditis. In patients in whom an abnormal host immune response had been seen, progressive deterioration of right and left ventricular function could be observed. This pattern may be superimposed on the genetically determined background of ARVD. This could explain the wide spectrum of clinical presentation observed in patients with tachycardia originating in an abnormal right ventricle.

Endomyocardial biopsy in right ventricular cardiomyopathy

Right ventricular cardiomyopathy is characterized by a progressive myocyte loss and fibro-fatty substitution of the right ventricle. The aim of our study was to assess the diagnostic accuracy of right ventricular endomyocardial biopsy. Using an imaging analyser system, histomorphometric parameters of myocytes, interstitium, fibrous tissue and fatty tissue were evaluated on endomyocardial biopsy from 30 patients with arrhythmogenic right ventricular cardiomyopathy, 29 patients with dilated cardiomyopathy and 30 control patients. The percent area of myocytes decreased from 78.10 +/- 7.34 in control to 63.39 +/- 9.22 in dilated cardiomyopathy (P < 0.05) and to 47.28 +/- 15.01 in arrhythmogenic right ventricular cardiomyopathy (P < 0.01). Fibrous tissue increased from 8.10 +/- 3.89 in control to 21.80 +/- 9.29 in dilated cardiomyopathy (P < 0.05) and to 24.60 +/- 11.37 in arrhythmogenic right ventricular cardiomyopathy (P < 0.05). Fatty tissue varied from 0.33 +/- 1.44 in control and 0.07 +/- 0.31 in dilated cardiomyopathy to 13.30 +/- 17.30 in arrhythmogenic right ventricular cardiomyopathy (P < 0.05). Fatty tissue was a feature of arrhythmogenic right ventricular cardiomyopathy (67% of patients vs. 6% of control and dilated cardiomyopathy patients). Diagnostic values typifying arrhythmogenic right ventricular cardiomyopathy, obtained by excluding any overlapping between confidence intervals in the three groups, were: myocytes < 44.95%; fibrous tissue > 40.38%, and fatty tissue > 3.21%, with 67% sensitivity and 91.53% specificity for at least one parameter. In conclusion, a significant difference between arrhythmogenic right ventricular cardiomyopathy, dilated cardiomyopathy and control exists in terms of amount of myocytes, fibrous tissue and fatty tissue. Presence of fatty tissue and fibrous tissue exceeding 3.21% and 40.38%, respectively should be considered highly suspect for arrhythmogenic right ventricular cardiomyopathy in right ventricular endomyocardial biopsy.