DiscoVari: A Web-Based Precision Medicine Tool for Predicting Variant Pathogenicity in Cardiomyopathy- and Channelopathy-Associated Genes

BACKGROUND

With genetic testing advancements, the burden of incidentally identified cardiac disease-associated gene variants is rising. These variants may carry a risk of sudden cardiac death, highlighting the need for accurate diagnostic interpretation. We sought to identify pathogenic hotspots in sudden cardiac death-associated genes using amino acid-level signal-to-noise (S:N) analysis and develop a web-based precision medicine tool, DiscoVari, to improve variant evaluation.

METHODS

The minor allele frequency of putatively pathogenic variants was derived from cohort-based cardiomyopathy and channelopathy studies in the literature. We normalized disease-associated minor allele frequencies to rare variants in an ostensibly healthy population (Genome Aggregation Database) to calculate amino acid-level S:N. Amino acids with S:N above the gene-specific threshold were defined as hotspots. DiscoVari was built using JavaScript ES6 and using open-source JavaScript library ReactJS, web development framework Next.js, and JavaScript runtime NodeJS. We validated the ability of DiscoVari to identify pathogenic variants using variants from ClinVar and individuals clinically evaluated at the Duke University Hospitals with cardiac genetic testing.

RESULTS

We developed DiscoVari as an internet-based tool for S:N-based variant hotspots. Upon validation, a higher proportion of ClinVar likely pathogenic/pathogenic variants localized to DiscoVari hotspots (43.1%) than likely benign/benign variants (17.8%; P<0.0001). Further, 75.3% of ClinVar variants reclassified to likely pathogenic/pathogenic were in hotspots, compared with 41.3% of those reclassified as variants of uncertain significance (P<0.0001) and 23.4% of those reclassified as likely benign/benign (P<0.0001). Of the clinical cohort variants, 73.1% of likely pathogenic/pathogenic were in hotspots, compared with 0.0% of likely benign/benign (P<0.01).

CONCLUSIONS

DiscoVari reliably identifies disease-susceptible amino acid residues to evaluate variants by searching amino acid-specific S:N ratios.

Heart Failure in Patients with Arrhythmogenic Cardiomyopathy

Arrhythmogenic cardiomyopathy (ACM) is a rare inherited cardiomyopathy characterized as fibro-fatty replacement, and a common cause for sudden cardiac death in young athletes. Development of heart failure (HF) has been an under-recognized complication of ACM for a long time. The current clinical management guidelines for HF in ACM progression have nowadays been updated. Thus, a comprehensive review for this great achievement in our understanding of HF in ACM is necessary. In this review, we aim to describe the research progress on epidemiology, clinical characteristics, risk stratification and therapeutics of HF in ACM.

Heart failure in patients with arrhythmogenic right ventricular cardiomyopathy: Genetic characteristics

BACKGROUND

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a genetically determined heart muscle disorder. The incidence of heart failure (HF) in ARVC has been reported at 5-13%. We aimed to define the genotype and disease progression of ARVC patients with HF.

METHODS

Patients with a definite diagnosis of ARVC who underwent genetic testing were consecutively recruited. Detailed clinical data was collected at baseline and during follow up. Clinical endpoint was a composite of heart transplantation and death due to HF.

RESULTS

135 patients were included. 8 (5.9%) patients reached the endpoint. Patients reaching the endpoint were significantly more likely to carry a Plakophilin 2 mutation than patients without HF, and 50% had multiple variants, however only one patient had 2 pathogenic mutations.

CONCLUSIONS

HF is a rare but significant outcome of patients with a definite diagnosis of ARVC. Patients with HF predominantly carried Plakophilin 2 mutations and often had multiple variants. RV dysfunction appears to be a determinant of heart transplantation and death.

Incidentally identified genetic variants in arrhythmogenic right ventricular cardiomyopathy-associated genes among children undergoing exome sequencing reflect healthy population variation

BACKGROUND

With expanding use of clinical whole exome sequencing (WES), genetic variants of uncertain significance are increasingly identified. As pathologic mutations in genes associated with arrhythmogenic right ventricular cardiomyopathy (ARVC) carry a risk of sudden death, determining the diagnostic relevance of incidentally identified variants associated with these genes is critical.

METHODS

WES variants from a large, predominantly pediatric cohort (N = 7,066 probands) were obtained for nine ARVC-associated genes (Baylor Miraca). For comparison, a control cohort was derived from the gnomAD database and an ARVC case cohort (N = 1,379 probands) was established from ARVC cases in the literature. Topologic mapping was performed and signal-to-noise analysis was conducted normalizing WES, or case variants, against control variant frequencies. Retrospective chart review was performed of WES cases evaluated clinically (Texas Children's Hospital).

RESULTS

Incidentally identified variants occurred in 14% of WES referrals and localized to genes which were rare among ARVC cases yet similar to controls. Amino acid-level signal-to-noise analysis of cases demonstrated "pathologic hotspots" localizing to critical domains of PKP2 and DSG2 while WES variants did not. PKP2 ARM7 and ARM8 domains and DSG2 N-terminal cadherin-repeat domains demonstrated high pathogenicity while normalized WES variant frequency was low. Review of clinical data available on WES referrals demonstrated none with evidence of ARVC among variant-positive individuals.

CONCLUSIONS

Incidentally identified variants are common among pediatric WES testing with gene frequencies similar to "background" variants. Incidentally identified variants are unlikely to be pathologic.

A global perspective of arrhythmogenic right ventricular cardiomyopathy

Abstract: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a progressive inherited heart disease characterized by ventricular arrhythmias and sudden cardiac death especially in the young. ARVC has been traditionally associated with the Mediterranean basin, as many seminal studies on the disease have originated from research groups of this region. Today, however, numerous ARVC registries from all over the world emphasize that the disease does not have a specific racial or geographical predilection. This work provides a review on the global perspective of ARVC.

Implantable cardioverter defibrillators in arrhythmogenic right ventricular dysplasia/cardiomyopathy: patient outcomes, incidence of appropriate and inappropriate interventions, and complications

BACKGROUND

Arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) is a cardiomyopathy characterized by ventricular arrhythmias and an abnormal right ventricle. Implantable cardioverter defibrillator (ICD) therapy may prevent sudden cardiac death in patients with ARVD/C. Currently, an overview of outcomes, appropriate and inappropriate interventions, and complications of ICD therapy in ARVD/C is lacking.

METHODS AND RESULTS

A literature search was performed to identify studies reporting outcome and complications in patients with ARVD/C who underwent ICD implantation. Of 641 articles screened, 24 studies on 18 cohorts were eligible for inclusion. In case of multiple publications on a cohort, the most recent publication was included in the meta-analysis. There were 610 patients (mean age, 40.4 years; 42% women), who had an ICD for primary or secondary prevention of sudden cardiac death. Risk factors for sudden cardiac death were presyncope (61%), syncope (31%), previous cardiac arrest (14%), ventricular tachycardia (58%), and ventricular fibrillation (6%). Antiarrhythmic medication consisted mostly of β-blockers (38%), amiodarone (14%), or sotalol (30%). During the 3.8-year follow-up, annualized cardiac mortality rate was 0.9%, annualized noncardiac mortality rate was 0.8%, and annualized heart transplant rate was 0.9%. The annualized appropriate and inappropriate ICD intervention rates were 9.5% and 3.7%, respectively. ICD-related complications consisted of difficult lead placement (18.4%), lead malfunction (9.8%), infection (1.4%), lead displacement (3.3%), and any complication (20.3%).

CONCLUSIONS

Cardiac and noncardiac mortality rates after ICD implantation in patients with ARVD/C are low. Appropriate ICD interventions occur at a rate of 9.5%/y. Inappropriate ICD interventions and complications lead to considerable ICD-related morbidity.

Predictors of appropriate ICD therapy in patients with arrhythmogenic right ventricular cardiomyopathy: long term experience of a tertiary care center

Introduction

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a rare genetically transmitted disease prone to ventricular arrhythmias. We therefore investigated the clinical, echocardiographical and electrophysiological predictors of appropriate implantable cardioverter defibrillator (ICD) therapy in patients with ARVC.

Methods

A retrospective analysis was performed in 26 patients (median age of 40 years at diagnosis, 21 males and 5 females) with ARVC who underwent ICD implantation.

Results

Over a median (range) follow-up period of 10 (2.7, 37) years, appropriate ICD therapy for ventricular arrhythmias was documented in 12 (46%) out of 26 patients. In all patients with appropriate ICD therapy the ICD was originally inserted for secondary prevention. Median time from ICD implantation to ICD therapy was 9 months (range 3.6, 54 months). History of heart failure was a significant predictor of appropriate ICD therapy (p = 0.033). Left ventricular disease involvement (p = 0.059) and age at implantation (p = 0.063) were borderline significant predictors. Patients with syncope at time of diagnosis were significantly less likely to receive ICD therapy (p = 0.02). Invasive electrophysiological testing was not significantly associated with appropriate ICD therapy.

Conclusion

In our cohort of patients with ARVC, history of heart failure was a significant predictor of appropriate ICD therapy, whereas left ventricular involvement and age at time of ICD implantation were of borderline significance. These predictors should be tested in larger prospective cohorts to optimize ICD therapy in this rare cardiomyopathy.

Prognostic value of QRS fragmentation in patients with arrhythmogenic right ventricular cardiomyopathy/dysplasia

CONTEXT

QRS fragmentation, including epsilon potentials, terminal activation delay and prolonged S wave upstroke, has been recently described as a diagnostic criterion of arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D). Whether QRS fragmentation is a marker of recurrent ventricular tachycardia, primary ventricular fibrillation, implantable cardioverter defibrillator (ICD) discharge and sudden cardiac death in these patients is unknown.

RESULTS

Three hundred and thirty-five patients (167 men, mean age 46.3 ± 14.6 years) with ARVC/D according to International Society and Federation of Cardiology/European Society of Cardiology (ISFC/ESC) criteria were analyzed retrospectively. Patients with complete and incomplete right bundle branch block were excluded from the analysis. At 6.3 ± 3.1 years mean follow-up, seven patients (0.02%) had died suddenly, 39 patients (0.13%) experienced recurrent ventricular tachycardia, 32 patients (0.1%) presented with primary ventricular fibrillation and 30 patients (0.1%) had recurrent ICD discharges. QRS fragmentation was significantly associated with arrhythmic events (P < 0.0000001 for the endpoint of sudden cardiac death, P < 0.01 for recurrent ventricular tachycardia, P < 0.0001 for primary ventricular fibrillation and P < 0.001 for recurrent ICD discharges, respectively).

CONCLUSION

QRS fragmentation predicts arrhythmic events in patients with ARVC/D. Further, properly designed prospective studies are warranted to confirm these findings.

Long-term follow-up in patients with arrhythmogenic right ventricular cardiomyopathy

INTRODUCTION

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a major cause of sudden cardiac death due to tachyarrhythmias. The purpose of this study was to investigate the long-term prognosis in patients with ARVC and the incidence of rapid ventricular arrhythmias during follow-up.

METHODS

Thirty ARVC patients (19 male, 63.3%, mean age 48 ± 15 years) fulfilling modified Task Force criteria 2010 were included. Of them, 13 patients (43.3%) received implantable cardioverter-defibrillator (ICD) implantation. Rapid ventricular arrhythmia was defined as electrical storm or the occurrence of ventricular tachycardia (VT) or ventricular fibrillation (VF) with a cycle length of 240 ms or less that necessitate shock delivery to 2 or more times within a 24-hour period.

RESULTS

With a mean follow-up of 68 ± 10 months, 6 patients (20%) with ICD implantation had recurrent rapid VT/VF. One (3.3%) of them died of multiple shocks and SCD, and 5 (16.7%) had multiple ICD therapies due to VT/VF and electrical storm. The interval between the diagnosis of ARVC and occurrence of rapid VT/VF was 13.4 ± 4.9 months. Most (5/6, 83.3%) events of recurrent rapid VT/VF occurred within 2 years. Ablated patients who did not receive an ICD implant were totally free of rapid VT/VF.

CONCLUSIONS

For patients with ARVC, long-term prognosis is favorable. During a long-term follow-up, patients meeting the criteria for ICD implantation have a higher rate of rapid and potentially life-threatening arrhythmias. However, early and clustered recurrence of rapid VT/VF in patients with an ICD is common, whereas late occurrence of rapid VT/VF is very rare.

Molecular changes in the heart of a severe case of arrhythmogenic right ventricular cardiomyopathy caused by a desmoglein-2 null allele

INTRODUCTION

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a genetic disorder caused by mutations in desmosomal genes. It is often associated with life-threatening arrhythmias. Some affected individuals develop progressive heart failure and may require cardiac transplantation.

METHODS

The explanted heart of a young adult with end-stage heart failure due to a null allele in desmoglein-2 was studied at macroscopic, microscopic, and molecular level. Myocardial samples were probed for junctional localization of desmosomal components and the gap junction protein connexin43 by immunohistochemical staining. In addition, the protein content of desmosomal and adherens junction markers as well as connexin43 was assessed by Western blotting.

RESULTS

Histological analysis confirmed ARVC. Despite the loss of specific immunoreactive signal for desmosomal components at the cardiac intercalated disks (shown for plakoglobin, desmoplakin, and plakophilin-2), these proteins could be detected by Western blotting. Only for desmoglein-2, desmocollin-2, and plakoglobin were reduced protein levels observed. Adherens junction proteins were not affected. Lower phosphorylation levels were observed for connexin43; however, localization of the gap junction protein displayed regional differences. At the molecular level, disease progression was more severe in the right ventricle compared to the left ventricle.

CONCLUSION

Our data suggest that, in the ARVC heart, plakoglobin is mainly redistributed from the junctions to other cellular pools and that protein degradation only plays a secondary role. Homogenous changes in the phosphorylation status of connexin43 were observed in multiple ARVC samples, suggesting that this might be a general feature of the disease.

Management of a rare case of arrhythmogenic right ventricular dysplasia in pregnancy: a case report

Introduction

Arrhythmogenic right ventricular dysplasia is a heritable disease of the heart muscle characterized by fibrofatty degeneration of cardiomyocytes. Patients present with ventricular arrhythmias or congestive heart failure, and sometimes sudden cardiac death occurs. Prenatal diagnosis has become possible with the detection of mutations, but, to the best of our knowledge, no case of prenatal diagnosis has been reported previously. There is little information about the management of arrhythmogenic right ventricular dysplasia in pregnancy, and the preferred mode of delivery is not certain; therefore, we present the case of a patient with arrhythmogenic right ventricular dysplasia and discuss the prenatal diagnosis, patient management and prognosis in pregnancy.

Case presentation

A 26-year-old Caucasian woman who presented to our hospital with heart palpitations was diagnosed with arrhythmogenic right ventricular dysplasia, and, after three years of follow up with anti-arrhythmic drugs, she wanted to conceive. During pregnancy, she ceased taking her medication. She tolerated pregnancy very well but her cardiac symptoms recurred after her 30th week of pregnancy. She delivered a baby via cesarean section under general anesthesia in her 38th week of pregnancy. She was discharged without any medications and continued lactation for six months.

Conclusion

Patients with mild to moderate arrhythmogenic right ventricular dysplasia tolerate pregnancy and breastfeeding very well, but patients with end-stage arrhythmogenic right ventricular dysplasia should be discouraged from conception.