Background—: Mutations in genes encoding for desmosomal proteins are the most common cause of arrhythmogenic right ventricular cardiomyopathy (ARVC). We assessed the value of genotype for prediction of lifetime major arrhythmic events and sudden cardiac death (SCD) in desmosomal gene–related ARVC. Methods and Results—: The overall study population included 134 desmosomal gene mutation carriers (68 men; median age 36 years [22–52]) from 44 consecutive ARVC families undergoing comprehensive genetic screening. The probability of experiencing a first major arrhythmic event or SCD during a lifetime was determined by using date of birth as start point for the time-to-event analysis, and was stratified by sex, desmosomal genes, mutation types, and genotype complexity (single versus multiple mutations). One hundred thirteen patients (84%) carried a single desmosomal gene mutation in desmoplakin (n=44; 39%), plakophilin-2 (n=38; 34%), desmoglein-2 (n=30; 26%), and desmocollin-2 (n=1; 1%), whereas 21 patients (16%) had a complex genotype with compound heterozygosity in 7 and digenic heterozygosity in 14. Over a median observation period of 39 (22–52) years, 22 patients (16%) from 20 different families had arrhythmic events, such as SCD (n=1), aborted SCD because of ventricular fibrillation (n=6), sustained ventricular tachycardia (n=14), and appropriate defibrillator intervention (n=1). Multiple desmosomal gene mutations and male sex were independent predictors of lifetime arrhythmic events with a hazard ratio of 3.71 (95% confidence interval, 1.54–8.92; P =0.003) and 2.76 (95% confidence interval, 1.19–6.41; P =0.02), respectively. Conclusions—: Compound/digenic heterozygosity was identified in 16% of ARVC-causing desmosomal gene mutation carriers and was a powerful risk factor for lifetime major arrhythmic events and SCD. These results support the use of comprehensive genetic screening of desmosomal genes for arrhythmic risk stratification in ARVC.

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a major cause of juvenile sudden death and is characterized by fibro-fatty replacement of the right ventricle. Mutations in several genes encoding desmosomal proteins have been identified in ARVC. We speculated that αT-catenin, encoded by CTNNA3, might also carry mutations in ARVC patients. Alpha-T-catenin binds plakophilins and this binding contributes to the formation of the area composita, which strengthens cell–cell adhesion in contractile cardiomyocytes. We used denaturing high-performance liquid chromatography and direct sequencing to screen CTNNA3 in 76 ARVC patients who did not carry any mutations in the desmosomal genes commonly mutated in ARVC. Mutations c.281T > A (p.V94D) and c.2293_2295delTTG (p.del765L) were identified in two probands. They are located in important domains of αT-catenin. Yeast two-hybrid and cell transfection studies showed that the interaction between the p.V94D mutant protein and β-catenin was affected, whereas the p.del765L mutant protein showed a much stronger dimerization potential and formed aggresomes in HEK293T cells. These findings might point to a causal relationship between CTNNA3 mutations and ARVC. This first report on the involvement of an area composita gene in ARVC shows that the pathogenesis of this disease extends beyond desmosomes. Since the frequency of CTNNA3 mutations in ARVC patients is not rare, systematic screening for this gene should be considered to improve the clinical management of ARVC families.

Hypertrophic cardiomyopathy (HCM) is the most common inherited heart disease and the leading cause of sudden cardiac death in young people. Mutations in genes that encode structural proteins of the cardiac sarcomere are the more frequent genetic cause of HCM. The disease is characterized by cardiomyocyte hypertrophy and myocardial fibrosis, which is defined as the excessive deposition of extracellular matrix proteins, mainly collagen I and III, in the myocardium. The development of fibrotic tissue in the heart adversely affects cardiac function. In this review, we discuss the latest evidence on how cardiac fibrosis is promoted, the role of cardiac fibroblasts, their interaction with cardiomyocytes, and their activation via the TGF-β pathway, the primary intracellular signalling pathway regulating extracellular matrix turnover. Finally, we summarize new findings on profibrotic genes as well as genetic and non-genetic factors involved in the pathophysiology of HCM.

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited heart muscle disease carrying a risk of sudden death. Information about the clinical features during childhood and the age at disease onset is scanty. The aim of the study was to describe the ARVC phenotype as its initial clinical manifestation in a pediatric population (14 years (42%). At the end of follow-up (9 ± 7 years), 21 (40%) fulfilled the 1994 diagnostic criteria (mean age 16 ± 4 years). By using the 2010 criteria in subjects aged ≤18 years, 53% were unaffected, versus 62% by using the traditional criteria. More than two-thirds of affected subjects had moderate-severe forms of the disease. Contrast-enhanced CMR was performed in 21 (40%); of 13 unaffected gene mutation carriers, six showed ARVC morphological and/or tissue abnormalities. In pediatric ARVC mutation carriers, a diagnosis was achieved in 40% of cases, confirming that the disease usually develops during adolescence and young adulthood. The 2010 modified criteria seem to be more sensitive than the 1994 ones in identifying familial pediatric cases. Contrast-enhanced CMR can provide diagnostic information on gene mutation carriers not fulfilling either traditional or modified criteria. Management of asymptomatic gene mutation carriers remains the main clinical challenge.

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited heart muscle disease characterized by fibrofatty replacement of the myocardium and ventricular arrhythmias, associated with mutations in the desmosomal genes. Only a missense mutation in the DES gene coding for desmin, the intermediate filament protein expressed by cardiac and skeletal muscle cells, has been recently associated with ARVC. We screened 91 ARVC index cases (53 negative for mutations in desmosomal genes and an additional 38 carrying desmosomal gene mutations) for DES mutations. Two rare missense variants were identified. The heterozygous p.K241E substitution was detected in 1 patient affected with a severe form of ARVC who also carried the p.T816RfsX10 mutation in plakophilin-2 gene. This DES substitution, showing an allele frequency of <0.01 in the control population, is predicted to cause an intolerant amino acid change in a highly conserved protein domain. Thus, it can be considered a rare variant with a possible modifier effect on the phenotypic expression of the concomitant mutation. The previously known p.A213V substitution was identified in 1 patient with ARVC who was negative for mutations in the desmosomal genes. Because a greater prevalence of p.A213V has been reported in patients with heart dilation than in control subjects, the hypothesis that this rare variant could have an unfavorable effect on cardiac remodeling cannot be ruled out. In conclusion, our data help to establish that, in the absence of skeletal muscle involvement suggestive of a desminopathy, the probability of DES mutations in ARVC is very low. These findings have important implications in the mutation screening strategy for patients with ARVC.