Catecholaminergic Polymorphic Ventricular Tachycardia

Clinical characteristics and follow-up of complex arrhythmias associated with RYR2 gene mutations in children

Objective

The aim of this study was to analyze the diagnosis, treatment, and follow-up of six cases of complex arrhythmias associated with RYR2 gene mutations in children.

Method

A retrospective analysis was conducted on six children diagnosed with complex arrhythmias associated with RYR2 gene mutations. The study included an analysis of the age of onset, initial symptoms, electrocardiographic characteristics, genetic results, treatment course, and follow-up outcomes.

Results

Among the six cases included in the study, there were four males and two females, with an average age of 3.5 ± 0.5 years. The average time from initial symptoms to diagnosis was 2.7 ± 1.3 years. The most common clinical manifestation was syncope, with exercise and emotions being the main triggers. All six children had de novo missense mutations in the RYR2 gene identified through whole-exome sequencing. In Holter electrocardiogram, atrial arrhythmias and sinoatrial node dysfunction were commonly observed in younger children. Four patients underwent exercise stress testing, with two experiencing bidirectional ventricular premature contractions and two experiencing bidirectional ventricular tachycardia and polymorphic ventricular tachycardia. Initial treatment involved oral propranolol or metoprolol. If arrhythmias persisted, flecainide or propafenone was added as adjunctive therapy. Two patients received permanent cardiac pacemaker treatment (single chamber ventricular pacemaker, VVI). All patients survived, with three experiencing occasional syncope during treatment. The follow-up period ranged from 12 to 37 months, with an average follow-up time of 24.3 ± 3.7 months.

Conclusion

Complex arrhythmias associated with RYR2 gene mutations in children can present with various clinical manifestations. Atrial arrhythmias combined with sinoatrial node dysfunction are commonly observed in younger children, and the combination of pharmacological therapy and cardiac pacemaker treatment yields favourable treatment outcomes.

Primary Electrical Heart Disease-Principles of Pathophysiology and Genetics

Primary electrical heart diseases, often considered channelopathies, are inherited genetic abnormalities of cardiomyocyte electrical behavior carrying the risk of malignant arrhythmias leading to sudden cardiac death (SCD). Approximately 54% of sudden, unexpected deaths in individuals under the age of 35 do not exhibit signs of structural heart disease during autopsy, suggesting the potential significance of channelopathies in this group of age. Channelopathies constitute a highly heterogenous group comprising various diseases such as long QT syndrome (LQTS), short QT syndrome (SQTS), idiopathic ventricular fibrillation (IVF), Brugada syndrome (BrS), catecholaminergic polymorphic ventricular tachycardia (CPVT), and early repolarization syndromes (ERS). Although new advances in the diagnostic process of channelopathies have been made, the link between a disease and sudden cardiac death remains not fully explained. Evolving data in electrophysiology and genetic testing suggest previously described diseases as complex with multiple underlying genes and a high variety of factors associated with SCD in channelopathies. This review summarizes available, well-established information about channelopathy pathogenesis, genetic basics, and molecular aspects relative to principles of the pathophysiology of arrhythmia. In addition, general information about diagnostic approaches and management is presented. Analyzing principles of channelopathies and their underlying causes improves the understanding of genetic and molecular basics that may assist general research and improve SCD prevention.

Interpretation and management of premature ventricular beats in athletes: An expert opinion document of the Italian Society of Sports Cardiology (SICSPORT)

Premature ventricular beats (PVBs) are recorded in a sizeable proportion of athletes during pre-participation screening, especially if the evaluation includes both resting and exercise ECG. While in the majority of cases no underlying heart disease is present, in others PVBs may be the sign of a condition at risk of sudden cardiac death, including cardiomyopathies, congenital, coronary artery, heart valves and ion channels diseases. In this expert opinion document of the Italian Society of Sports Cardiology, we propose a multiparametric interpretation approach to PVBs in athletes and a stepwise diagnostic algorithm. The clinical work-up should include the assessment of the probable site of origin based on the ECG pattern of the ectopic QRS and of the arrhythmia behavior (including the number of different PVB morphologies, complexity, response to exercise and reproducibility), as well as first-line tests such as echocardiography. Based on this initial evaluation, most athletes can be reassured of the benign nature of PVBs and cleared for competition under periodical follow-up. However, when the clinical suspicion is high, further investigations with non-invasive (e.g. cardiac magnetic resonance, cardiac computed tomography, genetic testing) and, in very selected cases, invasive (e.g. endocardial voltage mapping and endomyocardial biopsy) tests should be carried out to rule out a high-risk condition. Importantly, such advanced tests should be performed in centers with a consolidated experience not only in the technique, but also in evaluation of athletes.

Identification of differentially expressed proteins in heart of mouse death from smother based on label-free proteomics

Identification of mechanical asphyxia deaths without obvious injuries is a difficult problem for forensic medicine. This study aimed to identify molecular biological markers to predict death from mechanical asphyxia (smother). We established a smother model of mice by over the head with plastic bag tightly until the mice died and applied label-free proteomic technology to identify differentially expressed proteins (DEPs) in heart. A total of 3307 proteins were quantified, and a Fold Change (FC) > 1.2 (or <1/1.2) and Q value < 0.05 were considered as DEPs. Through comparative analysis, we identified 606 DEPs compared to the control group, comprising 219 upregulated and 387 downregulated proteins. Bioinformatics analysis (MCODE analysis) showed that the candidate proteins were mainly involved in regulation of ribosome function, myocardial contraction and calcium regulation, regulation of coagulation and regulation of mitochondrial oxidative respiration. Seven of these proteins were validated using parallel reaction monitoring (PRM), including fibrinogen alpha chain (FIBA), fibrinogen gamma chain (FIBG), Calsequestrin-2 (CASQ2), NADH dehydrogenase [ubiquinone] 1 alpha subcomplex subunit 11 (NDUAB), NADH dehydrogenase [ubiquinone] 1 alpha subcomplex subunit 3 (NDUA3), NADH dehydrogenase [ubiquinone] 1 alpha subcomplex subunit 13 (NDUAD) and Rab7 (RAB7A). CASQ2 and FIBG were further validated by immunohistochemistry. In conclusion, our results may provide some auxiliary indices for identifying the death from mechanical asphyxia.

Precision medicine in catecholaminergic polymorphic ventricular tachycardia: Recent advances toward personalized care

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a rare inherited cardiac ion channelopathy where the initial disease presentation is during childhood or adolescent stages, leading to increased risks of sudden cardiac death. Despite advances in medical science and technology, several gaps remain in the understanding of the molecular mechanisms, risk prediction, and therapeutic management of patients with CPVT. Recent studies have identified and validated seven sets of genes responsible for various CPVT phenotypes, including RyR2, CASQ-2, TRDN, CALM1, 2, and 3, and TECRL, providing novel insights into the molecular mechanisms. However, more data on atypical CPVT genotypes are required to investigate the underlying mechanisms further. The complexities of the underlying genetics contribute to challenges in risk stratification as well as the uncertainty surrounding nongenetic modifiers. Therapeutically, although medical management involving beta-blockers and flecainide, or insertion of an implantable cardioverter defibrillator remains the mainstay of treatment, animal and stem cell studies on gene therapy for CPVT have shown promising results. However, its clinical applicability remains unclear. Current gene therapy studies have primarily focused on the RyR2 and CASQ-2 variants, which constitute 75% of all CPVT cases. Alternative approaches that target a broader population, such as CaMKII inhibition, could be more feasible for clinical implementation. Together, this review provides an update on recent research on CPVT, highlighting the need for further investigation of the molecular mechanisms, risk stratification, and therapeutic management of this potentially lethal condition.

Arrhythmia-associated calmodulin variants interact with KCNQ1 to confer aberrant membrane trafficking and function

Missense variants in calmodulin (CaM) predispose patients to arrhythmias associated with high mortality rates ("calmodulinopathy"). As CaM regulates many key cardiac ion channels, an understanding of disease mechanism associated with CaM variant arrhythmias requires elucidating individual CaM variant effects on distinct channels. One key CaM regulatory target is the KCNQ1 (KV7.1) voltage-gated potassium channel that carries the IKs current. Yet, relatively little is known as to how CaM variants interact with KCNQ1 or affect its function. Here, we take a multipronged approach employing a live-cell fluorescence resonance energy transfer binding assay, fluorescence trafficking assay, and functional electrophysiology to characterize >10 arrhythmia-associated CaM variants for effect on KCNQ1 CaM binding, membrane trafficking, and channel function. We identify one variant (G114W) that exhibits severely weakened binding to KCNQ1 but find that most other CaM variants interact with similar binding affinity to KCNQ1 when compared with CaM wild-type over physiological Ca2+ ranges. We further identify several CaM variants that affect KCNQ1 and IKs membrane trafficking and/or baseline current activation kinetics, thereby delineating KCNQ1 dysfunction in calmodulinopathy. Lastly, we identify CaM variants with no effect on KCNQ1 function. This study provides extensive functional data that reveal how CaM variants contribute to creating a proarrhythmic substrate by causing abnormal KCNQ1 membrane trafficking and current conduction. We find that CaM variant regulation of KCNQ1 is not uniform with effects varying from benign to significant loss of function, suggesting how CaM variants predispose patients to arrhythmia via the dysregulation of multiple cardiac ion channels. Classification: Biological, Health, and Medical Sciences, Physiology.

Prognostic value of secretoneurin in chronic heart failure. Data from the GISSI-Heart Failure trial

BACKGROUND

Circulating secretoneurin (SN) concentrations have been found to provide prognostic information in patients with acute heart failure. We wanted to assess whether SN would improve prognostication also in patients with chronic heart failure (HF) in a large multicenter trial.

METHODS

We measured plasma SN concentrations at randomization (n=1224) and after 3 months (n=1103) in patients with chronic, stable HF from the GISSI-HF study. The co-primary endpoints were (1) time to death or (2) admission to hospital for cardiovascular reasons.

RESULTS

Mean age was 67 years and 80% were male. Median (quartile 1-3) SN concentrations were 42.6 (35.0-62.8) pmol/L on randomization and 42.0 (34.5-53.1) pmol/L after 3 months, which are higher than SN concentrations in healthy subjects. Higher SN concentrations at randomization were associated with lower body-mass index (BMI), lower systolic blood pressure, lower estimated glomerular filtration rate (eGFR), higher B-type natriuretic peptide (BNP) concentrations, and diagnosis of chronic obstructive pulmonary disease. During median follow-up of 3.9 years, 344 patients (27.0%) died. After adjusting for age, sex, left ventricular ejection fraction, BMI, functional class, ischemic etiology, heart rate, blood pressure, eGFR, bilirubin, comorbidities, and BNP concentrations, logarithmically transformed SN concentrations on randomization were associated with mortality (HR 2.60 (95% CI 1.01-6.70), p=0.047). SN concentrations were also associated with admission to hospital for cardiovascular reasons, but the association was attenuated and no longer significant in multivariable analysis.

CONCLUSION

Plasma SN concentrations provided incremental prognostic information to established risk indices and biomarkers in a large cohort of chronic HF patients.

A genetic and developmental biological approach for a family with complex congenital heart diseases-evidence of digenic inheritance

Objective

Congenital heart disease (CHD) is caused by cardiovascular developmental defects and has a global prevalence of ∼1%. The etiology of CHD is multifactorial and remains generally unknown, despite advances in analytical techniques based on next-generation sequencing (NGS). The aim of our study was to elucidate the multi-genetic origin and pathogenesis of an intriguing familial case with complex CHD.

Methods

We performed an original trio-based gene panel analysis using NGS of the family, including two siblings with CHD of single ventricular phenotype, and their unaffected parents. The pathogenicity of the detected rare variants was investigated in silico, and the functional effects of the variants were confirmed in vitro using luciferase assays. The combinatorial effect of gene alterations of the putative responsible genes was tested in vivo using genetically engineered mutant mice.

Results

NGS-based gene panel analyses revealed two heterozygous rare variants in NODAL and in TBX20 common to the siblings and to just one of parents. Both variants were suspected pathogenic in silico, and decreased transcriptional activities of downstream signaling pathways were observed in vitro. The analyses of Nodal and Tbx20 double mutant mice demonstrated that Nodal+/-Tbx20-/- embryos showed more severe defects than Nodal+/+Tbx20-/- embryos during early heart development. The expression of Pitx2, a known downstream target of Nodal, was downregulated in Tbx20-/- mutants.

Conclusions

Two rare variants on NODAL and TBX20 genes detected in this family were considered to be loss-of-function mutations. Our results suggest that NODAL and TBX20 may be complementary for the cardiac development, and a combinatorial loss-of-function of NODAL and TBX20 could be implicated in digenic inherence as the etiology of complex CHD associated with single ventricle defects in this family.

Calcium Handling in Inherited Cardiac Diseases: A Focus on Catecholaminergic Polymorphic Ventricular Tachycardia and Hypertrophic Cardiomyopathy

Calcium (Ca²⁺) is the major mediator of cardiac contractile function. It plays a key role in regulating excitation-contraction coupling and modulating the systolic and diastolic phases. Defective handling of intracellular Ca²⁺ can cause different types of cardiac dysfunction. Thus, the remodeling of Ca²⁺ handling has been proposed to be a part of the pathological mechanism leading to electrical and structural heart diseases. Indeed, to ensure appropriate electrical cardiac conduction and contraction, Ca²⁺ levels are regulated by several Ca²⁺-related proteins. This review focuses on the genetic etiology of cardiac diseases related to calcium mishandling. We will approach the subject by focalizing on two clinical entities: catecholaminergic polymorphic ventricular tachycardia (CPVT) as a cardiac channelopathy and hypertrophic cardiomyopathy (HCM) as a primary cardiomyopathy. Further, this review will illustrate the fact that despite the genetic and allelic heterogeneity of cardiac defects, calcium-handling perturbations are the common pathophysiological mechanism. The newly identified calcium-related genes and the genetic overlap between the associated heart diseases are also discussed in this review.

Management of Inherited Arrhythmia Syndromes: a HiRO Consensus Handbook on Process of Care

Inherited arrhythmia syndromes are rare genetic conditions that predispose seemingly healthy individuals to sudden cardiac arrest and death. The Hearts in Rhythm Organization is a multidisciplinary Canadian network of clinicians, researchers, patients, and families that aims to improve care for patients and families with inherited cardiac conditions, focused on those that confer predisposition to arrhythmia and sudden cardiac arrest and/or death. The field is rapidly evolving as research discoveries increase. A streamlined, practical guide for providers to diagnose and follow pediatric and adult patients with inherited cardiac conditions represents a useful tool to improve health system utilization, clinical management, and research related to these conditions. This review provides consensus care pathways for 7 conditions, including the 4 most common inherited cardiac conditions that confer predisposition to arrhythmia, with scenarios to guide investigation, diagnosis, risk stratification, and management. These conditions include Brugada syndrome, long QT syndrome, arrhythmogenic right ventricular cardiomyopathy and related arrhythmogenic cardiomyopathies, and catecholaminergic polymorphic ventricular tachycardia. In addition, an approach to investigating and managing sudden cardiac arrest, sudden unexpected death, and first-degree family members of affected individuals is provided. Referral to specialized cardiogenetic clinics should be considered in most cases. The intention of this review is to offer a framework for the process of care that is useful for both experts and nonexperts, and related allied disciplines such as hospital management, diagnostic services, coroners, and pathologists, in order to provide high-quality, multidisciplinary, standardized care.

Arrhythmia-associated Calmodulin Variants Interact with KCNQ1 to Confer Aberrant Membrane Trafficking and Function

Rationale

Missense variants in calmodulin (CaM) predispose patients to arrhythmias associated with high mortality rates. As CaM regulates several key cardiac ion channels, a mechanistic understanding of CaM variant-associated arrhythmias requires elucidating individual CaM variant effect on distinct channels. One key CaM regulatory target is the KCNQ1 (K V 7.1) voltage-gated potassium channel that underlie the I Ks current. Yet, relatively little is known as to how CaM variants interact with KCNQ1 or affect its function.

Objective

To observe how arrhythmia-associated CaM variants affect binding to KCNQ1, channel membrane trafficking, and KCNQ1 function.

Methods and Results

We combine a live-cell FRET binding assay, fluorescence trafficking assay, and functional electrophysiology to characterize >10 arrhythmia-associated CaM variants effect on KCNQ1. We identify one variant (G114W) that exhibits severely weakened binding to KCNQ1 but find that most other CaM variants interact with similar binding affinity to KCNQ1 when compared to CaM wild-type over physiological Ca 2+ ranges. We further identify several CaM variants that affect KCNQ1 and I Ks membrane trafficking and/or baseline current activation kinetics, thereby contextualizing KCNQ1 dysfunction in calmodulinopathy. Lastly, we delineate CaM variants with no effect on KCNQ1 function.

Conclusions

This study provides comprehensive functional data that reveal how CaM variants contribute to creating a pro-arrhythmic substrate by causing abnormal KCNQ1 membrane trafficking and current conduction. We find that CaM variant regulation of KCNQ1 is not uniform with effects varying from benign to significant loss of function. This study provides a new approach to collecting details of CaM binding that are key for understanding how CaM variants predispose patients to arrhythmia via the dysregulation of multiple cardiac ion channels.

Sex, Rhythm & Death: The effect of sexual activity on cardiac arrhythmias and sudden cardiac death

Arrhythmias and sudden cardiac death with sexual activity are rare. However, the demographics are changing regarding the cardiovascular patients at risk for these events. Recent studies have highlighted that the individuals having cardiac events during sexual activity are becoming younger, with a higher proportion of female decedents than previously described. There needs to be an open dialog between the cardiovascular team and the cardiac patient to provide the education and reassurance necessary for cardiovascular patients to participate in sexual intercourse safely. This paper reviews how sexual activity can lead to an increase in cardiac arrhythmias and sudden cardiac arrest in patients that are not medically optimized or are unaware of their underlying cardiac condition. The most common cardiovascular diseases associated with sexually induced arrhythmias and arrest are discussed regarding their potential risk and the psychosocial impact of this risk on these patients. Finally, cardiovascular medications and implantable cardioverter-defibrillators (ICDs) are addressed by reviewing the literature on the safety profile of these cardiac interventions in this patient population. Overall, sexual activity is safe for most cardiac patients, and providing proper education to the patient and their partner can improve the safety profile for patients with higher risk cardiovascular conditions. To give the appropriate education and reassurance necessary, cardiovascular team members need an understanding of the pathophysiology of how sexual activity can provoke arrhythmias and sudden cardiac arrest. Healthcare providers also need to build comfort in speaking to all patients and ensure that sexual partners, female patients, and those in the LGBTQIA + community receive the same access to counseling but tailored to their individual needs.

Exercise Testing Using Sprint Protocol vs Bruce Protocol in Catecholaminergic Polymorphic Ventricular Tachycardia

We present the case of a relative of a patient with catecholaminergic polymorphic ventricular tachycardia. This relative underwent a standard (Bruce) exercise stress test (EST), which had normal results. He then underwent our modified “sprint” EST, with positive results. This report underlines how the sprint EST may provoke arrhythmias better than the standard Bruce EST. (Level of Difficulty: Advanced.)

Pharmacogenomics of Pediatric Cardiac Arrest: Cisplatin Treatment Worsened by a Ryanodine Receptor 2 Gene Mutation

In thelast few decades, the roles of cardio-oncology and cardiovascular geneticsgained more and more attention in research and daily clinical practice, shaping a new clinical approach and management of patients affected by cancer and cardiovascular disease. Genetic characterization of patients undergoing cancer treatment can support a better cardiovascular risk stratification beyond the typical risk factors, suchas contractile function and QT interval duration, uncovering a possible patient’s concealed predisposition to heart failure, life threatening arrhythmias and sudden death. Specifically, an integrated cardiogenetic approach in daily oncological clinical practice can ensure the best patient-centered healthcare model, suggesting, also the adequate cardiac monitoring timing and alternative cancer treatments, reducing drug-related complications. We report the case of a 14-month-old girl affected by neuroblastoma, treated by cisplatin, complicated by cardiac arrest. We described the genetic characterization of a Ryanodine receptor 2 (RYR2) gene mutation and subsequent pharmacogenomic approach to better shape the cancer treatment.

Advances in the Molecular Genetics of Catecholaminergic Polymorphic Ventricular Tachycardia

Catecholaminergic polymorphic ventricular tachycardia is a primary arrhythmogenic syndrome with genetic features most commonly seen in adolescents, with syncope and sudden death following exercise or agitation as the main clinical manifestations. The mechanism of its occurrence is related to the aberrant release of Ca²⁺ from cardiomyocytes caused by abnormal RyR2 channels or CASQ2 proteins under conditions of sympathetic excitation, thus inducing a delayed posterior exertional pole, manifested by sympathetic excitation inducing adrenaline secretion, resulting in bidirectional or polymorphic ventricular tachycardia. The mortality rate of the disease is high, but patients usually do not have organic heart disease, the clinical manifestations may not be obvious, and no significant abnormal changes in the QT interval are often observed on electrocardiography. Therefore, the disease is often easily missed and misdiagnosed. A number of genetic mutations have been linked to the development of this disease, and the mechanisms are different. In this paper, we would like to summarize the possible genes related to catecholaminergic polymorphic ventricular tachycardia in order to review the genetic tests currently performed, and to further promote the development of genetic testing techniques and deepen the research on the molecular level of this disease.

Genetic Variants as Sudden-Death Risk Markers in Inherited Arrhythmogenic Syndromes: Personalized Genetic Interpretation

Inherited arrhythmogenic syndromes are the primary cause of unexpected lethal cardiac episodes in young people. It is possible that the first sign of the condition may be sudden death. Inherited arrhythmogenic syndromes are caused by genetic defects that may be analyzed using different technical approaches. A genetic alteration may be used as a marker of risk for families who carry the genetic alterations. Therefore, the early identification of the responsible genetic defect may help the adoption of preventive therapeutic measures focused on reducing the risk of lethal arrhythmias. Here, we describe the use of massive sequencing technologies and the interpretation of genetic analyses in inherited arrhythmogenic syndromes.