Arrhythmogenic right ventricular cardiomyopathy: a challenging disease of the intercalated disc

A comparative study on the analysis of hemodynamics in the athlete's heart

The pathophysiological mechanisms underlying the development of the athlete’s heart are still poorly understood. To characterize the intracavitary blood flows in the right ventricle (RV) and right-ventricular outflow tract (RVOT) in 2 healthy probands, patients with arrhythmogenic right ventricular cardiomyopathy (ARVC) and 2 endurance athletes, we performed 4D-MRI flow measurements to assess differences in kinetic energy and shear stresses. Time evolution of velocity magnitude, mean kinetic energy (MKE), turbulent kinetic energy (TKE) and viscous shear stress (VSS) were measured both along the whole RV and in the RVOT. RVOT regions had higher kinetic energy values and higher shear stresses levels compared to the global averaging over RV among all subjects. Endurance athletes had relatively lower kinetic energy and shear stresses in the RVOT regions compared to both healthy probands and ARVC patients. The athlete’s heart is characterized by lower kinetic energy and shear stresses in the RVOT, which might be explained by a higher diastolic compliance of the RV.

Crosstalk between coagulation and complement activation promotes cardiac dysfunction in arrhythmogenic right ventricular cardiomyopathy

Aims: We previously found that complement components are upregulated in the myocardium of patients with arrhythmogenic right ventricular cardiomyopathy (ARVC), and inhibiting the complement receptor C5aR reduces disease severity in desmin knockout (Des-/- ) mice, a model for ARVC. Here, we examined the mechanism underlying complement activation in ARVC, revealing a potential new therapeutic target. Methods: First, immunostaining, RT-PCR and western blot were used to detect the expression levels of complement and coagulation factors. Second, we knocked out the central complement component C3 in Des-/- mice (ARVC model) by crossing Des-/- mice with C3-/- mice to explore whether complement system activation occurs independently of the conventional pathway. Then, we evaluated whether a targeted intervention to coagulation system is effective to reduce myocardium injury. Finally, the plasma sC5b9 level was assessed to investigate the role in predicting adverse cardiac events in the ARVC cohort. Results: The complement system is activated in the myocardium in ARVC. Autoantibodies against myocardial proteins provided a possible mechanism underlying. Moreover, we found increased levels of myocardial C5 and the serum C5a in Des-/-C3-/- mice compared to wild-type mice, indicating that C5 is activated independently from the conventional pathway, presumably via the coagulation system. Crosstalk between the complement and coagulation systems exacerbated the myocardial injury in ARVC mice, and this injury was reduced by using the thrombin inhibitor lepirudin. In addition, we found significantly elevated plasma levels of sC5b9 and thrombin in patients, and this increase was correlated with all-cause mortality. Conclusions: These results suggest that crosstalk between the coagulation and complement systems plays a pathogenic role in cardiac dysfunction in ARVC. Thus, understanding this crosstalk may have important clinical implications with respect to diagnosing and treating ARVC.

Mechanotranduction Pathways in the Regulation of Mitochondrial Homeostasis in Cardiomyocytes

Mitochondria are one of the most important organelles in cardiomyocytes. Mitochondrial homeostasis is necessary for the maintenance of normal heart function. Mitochondria perform four major biological processes in cardiomyocytes: mitochondrial dynamics, metabolic regulation, Ca2+ handling, and redox generation. Additionally, the cardiovascular system is quite sensitive in responding to changes in mechanical stress from internal and external environments. Several mechanotransduction pathways are involved in regulating the physiological and pathophysiological status of cardiomyocytes. Typically, the extracellular matrix generates a stress-loading gradient, which can be sensed by sensors located in cellular membranes, including biophysical and biochemical sensors. In subsequent stages, stress stimulation would regulate the transcription of mitochondrial related genes through intracellular transduction pathways. Emerging evidence reveals that mechanotransduction pathways have greatly impacted the regulation of mitochondrial homeostasis. Excessive mechanical stress loading contributes to impairing mitochondrial function, leading to cardiac disorder. Therefore, the concept of restoring mitochondrial function by shutting down the excessive mechanotransduction pathways is a promising therapeutic strategy for cardiovascular diseases. Recently, viral and non-viral protocols have shown potentials in application of gene therapy. This review examines the biological process of mechanotransduction pathways in regulating mitochondrial function in response to mechanical stress during the development of cardiomyopathy and heart failure. We also summarize gene therapy delivery protocols to explore treatments based on mechanical stress-induced mitochondrial dysfunction, to provide new integrative insights into cardiovascular diseases.

Catheter Ablation of Ventricular Tachycardia in Patients With Arrhythmogenic Right Ventricular Cardiomyopathy/Dysplasia: A Sequential Approach

Background

It has been suggested that endocardial and epicardial ablation of ventricular tachycardia (VT) improves outcome in arrhythmogenic right ventricular cardiomyopathy/dysplasia. We investigated our sequential approach for VT ablation in patients with arrhythmogenic right ventricular cardiomyopathy/dysplasia in a single center.

Methods and Results

We included 47 patients (44±16 years) with definite (81%) or borderline (19%) arrhythmogenic right ventricular cardiomyopathy/dysplasia between 1998 and 2016. Our ablation strategy was to target the endocardial substrate. Epicardial ablation was performed in case of acute ablation failure or lack of an endocardial substrate. Single and multiple procedural 1‐ and 5‐year outcome data for the first occurrence of the study end points (sustained VT/ventricular fibrillation, heart transplant, and death after the index procedure, and sustained VT/ventricular fibrillation for multiple procedures) are reported. Eighty‐one radiofrequency ablation procedures were performed (mean 1.7 per patient, range 1–4). Forty‐five (56%) ablation procedures were performed via an endocardial, 11 (13%) via an epicardial, and 25 (31%) via a combined endo‐ and epicardial approach. Complete acute success was achieved in 65 (80%) procedures, and partial success in 13 (16%). After a median follow‐up of 50.8 (interquartile range, [18.6; 99.2]) months after the index procedure, 17 (36%) patients were free from the primary end point. After multiple procedures, freedom from sustained VT/ventricular fibrillation was 63% (95% CI, 52–75) at 1 year, and 45% (95% CI, 34–61) at 5 years, with 36% of patients receiving only endocardial radiofrequency ablation. A trend (log rank P=0.058) towards an improved outcome using a combined endo‐/epicardial approach was observed after multiple procedures.

Conclusion

Endocardial ablation can be effective in a considerable number of arrhythmogenic right ventricular cardiomyopathy/dysplasia patients with VT, potentially obviating the need for an epicardial approach.

Plasma testosterone and arrhythmic events in male patients with arrhythmogenic right ventricular cardiomyopathy

AIMS

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is associated with life-threatening ventricular arrhythmia and progressive ventricular dysfunction. Previous studies suggested that sex hormones play an important role in the onset and prognosis of ARVC. This study aimed to investigate the role of testosterone in predicting major adverse cardiac events in the Chinese ARVC cohort.

METHODS AND RESULTS

Ninety-nine ARVC patients (median age, 40 years; 70.7% male) and 96 healthy controls (median age, 41 years; 62.5% male) were enrolled. The circulating levels of testosterone were measured by enzyme-linked immunosorbent assays (ELISA). The median follow-up time of all ARVC male patients was 17 months (interquartile range/IQR 9-29). Cox proportional hazards regression was used to analyse the effect of plasma testosterone and other well-described risk factors on malignant arrhythmic events in male ARVC patients. The male ARVC patients had significantly elevated levels of total testosterone [TT, 6.390 (4.438-8.768) ng/mL vs. 3.617 (2.073-4.479) ng/mL, P < 0.0001, data shown as the median with IQR], bioavailable testosterone [BT, 4.11 (1.990-6.545) ng/mL vs. 1.32 (0.7965-2.0350) ng/mL, P < 0.0001, median with IQR], and free testosterone [FT, 0.2055 (0.1000-0.4073) ng/mL vs. 0.0768 (0.0405-0.1105) ng/mL, P < 0.0001, median with IQR] than healthy male volunteer, whereas no differences were observed among female counterparts. There was no significant correlation between the baseline clinical characteristics and testosterone levels in male ARVC patients (Spearman's correlation test, P > 0.05). During the follow-up, the levels of testosterone were higher in male patients who experienced malignant arrhythmic events (N = 22) than in those who did not (N = 25) [TT, 9.034 (7.222-15.370) ng/mL vs. 4.633 (3.363-6.375) ng/mL, P < 0.001; BT, 7.485 (2.070-9.163) ng/mL vs. 3.300 (1.685-4.690) ng/mL, P < 0.05; FT, 0.453 (0.221-0.758) ng/mL vs. 0.161 (0.075-0.337) ng/mL P < 0.05, data expressed as median (IQR) and adjusted by Dunn's multiple comparisons test], whereas such distinction was not observed among patients with significant structural progression events (N = 16). Through multivariable adjustments, the Cox regression analysis showed the level of plasma total testosterone (HR = 1.325, 95% confidence interval = 1.171-1.498, P < 0.001) was an independent predictor for malignant arrhythmic events.

CONCLUSIONS

The levels of plasma testosterone in ARVC male patients are higher than those in healthy males. Testosterone level, without relation to the baseline cardiac function and future significant structural progression events, is a strong predictor of future adverse arrhythmic events in male patients with ARVC. Therefore, our results suggest that testosterone may be a useful biomarker in arrhythmic risk prediction in the ARVC.

Arrhythmogenic right ventricular cardiomyopathy: implications of next-generation sequencing in appropriate diagnosis

Aims

To evaluate potential differences in the genetic profile of cases with 'definite', 'borderline', and 'possible' arrhythmogenic right ventricular cardiomyopathy (ARVC) phenotype by 2010 task force criteria using a custom genetic panel after whole-exome analysis.

Methods and results

We performed whole-exome sequencing in 14 cases with the clinical diagnosis ARVC using an 'Illumina HighSeq 2000' system. We presented our initial results focused on 96 known cardiomyopathy and channelopathy genes. According to the 2010 task force criteria, 7/14 cases (50%) were classified as 'definite' phenotype, 4/14 (29%) were 'borderline', and 3/14 (21%) were diagnosed with the 'possible' phenotype. Nine out of 14 patients (64%) were males, and all were Caucasians, with an average age at genetic diagnosis of 50 ± 15 years. Among the seven cases with the 'definite' phenotype, six (86%) had a putative desmosomal mutation, while none of the seven patients with a 'possible' or borderline task force classification phenotype hosted putative mutations in desmosomal genes. Four (57%) of them had rare variants in other dilated cardiomyopathy (DCM) genes.

Conclusions

Most of the patients with 'definite' ARVC phenotype by task force 2010 host mutations in desmosomal genes. Weaker ARVC phenotypes host variants/mutations in other DCM genes and result in a disease spectrum, including DCM or phenocopies of ARVC.

Sex hormones affect outcome in arrhythmogenic right ventricular cardiomyopathy/dysplasia: from a stem cell derived cardiomyocyte-based model to clinical biomarkers of disease outcome

Aims

Arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) is characterized by fibrofatty infiltration of the myocardium and ventricular arrhythmias that may lead to sudden cardiac death. It has been observed that male patients develop the disease earlier and present with more severe phenotypes as compared to females. Thus, we hypothesized that serum levels of sex hormones may contribute to major arrhythmic cardiovascular events (MACE) in patients with ARVC/D.

Methods and results

The serum levels of five sex hormones, sex hormone-binding globulin, high sensitivity troponin T, pro-brain natriuretic peptide, cholesterol, triglycerides, insulin, and glucose were measured in 54 ARVC/D patients (72% male). Twenty-six patients (48%) experienced MACE. Total and free testosterone levels were significantly increased in males with MACE as compared to males with a favourable outcome, whereas estradiol was significantly lower in females with MACE as compared to females with a favourable outcome. Increased testosterone levels remained independently associated with MACE in males after adjusting for age, body mass index, Task Force criteria, ventricular function, and desmosomal mutation status. Furthermore, an induced pluripotent stem cell-derived ARVC/D cardiomyocyte model was used to investigate the effects of sex hormones. In this model, testosterone worsened and estradiol improved ARVC/D-related pathologies such as cardiomyocyte apoptosis and lipogenesis, strongly supporting our clinical findings.

Conclusions

Elevated serum testosterone levels in males and decreased estradiol levels in females are independently associated with MACE in ARVC/D, and directly influence disease pathology. Therefore, determining the levels of sex hormones may be useful for risk stratification and may open a new window for preventive interventions.

Myocardial expression profiles of candidate molecules in patients with arrhythmogenic right ventricular cardiomyopathy/dysplasia compared to those with dilated cardiomyopathy and healthy controls

BACKGROUND

Arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) is mainly an autosomal dominant disease characterized by fibrofatty infiltration of the right ventricle, leading to ventricular arrhythmias. Mutations in desmosomal proteins can be identified in about half of the patients. The pathogenic mechanisms leading to disease expression remain unclear.

OBJECTIVE

The purpose of this study was to investigate myocardial expression profiles of candidate molecules involved in the pathogenesis of ARVC/D.

METHODS

Myocardial messenger RNA (mRNA) expression of 62 junctional molecules, 5 cardiac ion channel molecules, 8 structural molecules, 4 apoptotic molecules, and 6 adipogenic molecules was studied. The averaged expression of candidate mRNAs was compared between ARVC/D samples (n = 10), nonfamilial dilated cardiomyopathy (DCM) samples (n = 10), and healthy control samples (n = 8). Immunohistochemistry and quantitative protein expression analysis were performed. Genetic analysis using next generation sequencing was performed in all patients with ARVC/D.

RESULTS

Following mRNA levels were significantly increased in patients with ARVC/D compared to those with DCM and healthy controls: phospholamban (P ≤ .001 vs DCM; P ≤ .001 vs controls), healthy tumor protein 53 apoptosis effector (P = .001 vs DCM; P ≤ .001 vs controls), and carnitine palmitoyltransferase 1β (P ≤ .001 vs DCM; P = 0.008 vs controls). Plakophillin-2 (PKP-2) mRNA was downregulated in patients with ARVC/D with PKP-2 mutations compared with patients with ARVC/D without PKP-2 mutations (P = .04). Immunohistochemistry revealed significantly increased protein expression of phospholamban, tumor protein 53 apoptosis effector, and carnitine palmitoyltransferase 1β in patients with ARVC/D and decreased PKP-2 expression in patients with ARVC/D carrying a PKP-2 mutation.

CONCLUSION

Changes in the expression profiles of sarcolemmal calcium channel regulation, apoptosis, and adipogenesis suggest that these molecular pathways may play a critical role in the pathogenesis of ARVC/D, independent of the underlying genetic mutations.

Association of competitive and recreational sport participation with cardiac events in patients with arrhythmogenic right ventricular cardiomyopathy: results from the North American multidisciplinary study of arrhythmogenic right ventricular cardiomyopathy

AIMS

It has been proposed that competitive sport increases the risk of ventricular tachyarrhythmias (VTA) and death in patients with arrhythmogenic right-ventricular cardiomyopathy (ARVC). However, it is unknown whether this only applies to competitive sport or if recreational sports activity also increases the risk of VTA/death.

METHODS AND RESULTS

Probands diagnosed with ARVC according to the 2010 task force criteria for ARVC (n = 108) were included in the current analysis. At the time of enrolment, study participants were questioned about exercise level prior to and after ARVC diagnosis, within three categories of sports participation: competitive (n = 41), recreational (n = 48), and inactive (n = 19). Competitive sport was associated with a significantly higher risk of VTA/death when compared with both recreational sport [HR = 1.99 (1.21-3.28), P = 0.007] and inactive patients [HR = 2.05 (1.07-3.91), P = 0.030]. No increased risk of VTA/death was associated with recreational sport when compared with patients who were inactive [HR = 1.03 (0.54-1.97), P = 0.930]. Symptoms developed at an earlier age in patients who participated in competitive sport (30 ± 12 years), when compared with patients who participated in recreational sport (38 ± 17 years) (P = 0.015) and inactive patients (41 ± 11 years) (P = 0.002). No difference in age at first symptom was seen between patients who participated in recreational sport and inactive patients (P = 0.651).

CONCLUSION

Competitive sport was associated with a two-fold increased risk of VTA/death, and earlier presentation of symptoms, when compared with inactive patients, and to patients who participated in recreational sport. When compared with inactive patients, recreational sport was not associated with earlier onset of symptoms or increased risk of VTA/death. ClinicalTrials.gov Identifier: NCT00024505.

Electrocardiographic features of disease progression in arrhythmogenic right ventricular cardiomyopathy/dysplasia

BACKGROUND

Arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) is considered a progressive cardiomyopathy. However, data on the clinical features of disease progression are limited. The aim of this study was to assess 12-lead surface electrocardiographic (ECG) changes during long-term follow-up, and to compare these findings with echocardiographic data in our large cohort of patients with ARVC/D.

METHODS

Baseline and follow-up ECGs of 111 patients from three tertiary care centers in Switzerland were systematically analyzed with digital calipers by two blinded observers, and correlated with findings from transthoracic echocardiography.

RESULTS

The median follow-up was 4 years (IQR 1.9-9.2 years). ECG progression was significant for epsilon waves (baseline 14% vs. follow-up 31%, p = 0.01) and QRS duration (111 ms vs. 114 ms, p = 0.04). Six patients with repolarization abnormalities according to the 2010 Task Force Criteria at baseline did not display these criteria at follow-up, whereas in all patients with epsilon waves at baseline these depolarization abnormalities also remained at follow-up. T wave inversions in inferior leads were common (36% of patients at baseline), and were significantly associated with major repolarization abnormalities (p = 0.02), extensive echocardiographic right ventricular involvement (p = 0.04), T wave inversions in lateral precordial leads (p = 0.05), and definite ARVC/D (p = 0.05).

CONCLUSIONS

Our data supports the concept that ARVC/D is generally progressive, which can be detected by 12-lead surface ECG. Repolarization abnormalities may disappear during the course of the disease. Furthermore, the presence of T wave inversions in inferior leads is common in ARVC/D.

Arrhythmogenic ventricular cardiomyopathy: A paradigm shift from right to biventricular disease

Arrhythmogenic ventricular cardiomyopathy (AVC) is generally referred to as arrhythmogenic right ventricular (RV) cardiomyopathy/dysplasia and constitutes an inherited cardiomyopathy. Affected patients may succumb to sudden cardiac death (SCD), ventricular tachyarrhythmias (VTA) and heart failure. Genetic studies have identified causative mutations in genes encoding proteins of the intercalated disk that lead to reduced myocardial electro-mechanical stability. The term arrhythmogenic RV cardiomyopathy is somewhat misleading as biventricular involvement or isolated left ventricular (LV) involvement may be present and thus a broader term such as AVC should be preferred. The diagnosis is established on a point score basis according to the revised 2010 task force criteria utilizing imaging modalities, demonstrating fibrous replacement through biopsy, electrocardiographic abnormalities, ventricular arrhythmias and a positive family history including identification of genetic mutations. Although several risk factors for SCD such as previous cardiac arrest, syncope, documented VTA, severe RV/LV dysfunction and young age at manifestation have been identified, risk stratification still needs improvement, especially in asymptomatic family members. Particularly, the role of genetic testing and environmental factors has to be further elucidated. Therapeutic interventions include restriction from physical exercise, beta-blockers, sotalol, amiodarone, implantable cardioverter-defibrillators and catheter ablation. Life-long follow-up is warranted in symptomatic patients, but also asymptomatic carriers of pathogenic mutations.