Clinical manifestations of arrhythmogenic right ventricular cardiomyopathy in Korean patients

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.

Correlation between the parameters of signal-averaged ECG and two-dimensional echocardiography in patients with arrhythmogenic right ventricular cardiomyopathy

BACKGROUND

The correlation between parameters of two-dimensional echocardiography and signal-averaged ECG (SAECG) in patients with arrhythmogenic right ventricular cardiomyopathy (ARVC) is not known well.

METHODS

Thirty-three patients (13 females, 40.3 +/- 14.4 years old) were included in this study. Both the right and left ventricular dimensions and systolic function were assessed with two-dimensional echocardiography. The SAECG was performed with high-gain amplification and filtered using bidirectional Butterworth filters between 40 and 250 Hz. We evaluated the correlation between the parameters of the SAECG and two-dimensional echocardiography.

RESULTS

The right ventricular (RV) outflow tract was the most frequently (n = 18, 54%) involved segment. Six (18%) patients had only mildly decreased RV systolic function. All the other patients had normal RV systolic function. Although localized left ventricular wall motion abnormalities were observed in 14 (42%) patients, the left ventricular ejection fraction was normal in most (n = 32, 97%). Late potentials were positive in 22 (63%) patients. There was no significant correlation between parameters of the SAECG and two-dimensional echocardiography for the entire patient population.

CONCLUSIONS

The SAECG parameters exhibited no correlation to any of two-dimensional echocardiography parameters in the patients with ARVC. Fragmented electrical activity may develop with no significant relation to the anatomical changes in the patients with ARVC.