Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT) Associated With Ryanodine Receptor (RyR2) Gene Mutations - Long-Term Prognosis After Initiation of Medical Treatment

2024 Heart Disease and Stroke Statistics: A Report of US and Global Data From the American Heart Association

BACKGROUND

The American Heart Association (AHA), in conjunction with the National Institutes of Health, annually reports the most up-to-date statistics related to heart disease, stroke, and cardiovascular risk factors, including core health behaviors (smoking, physical activity, nutrition, sleep, and obesity) and health factors (cholesterol, blood pressure, glucose control, and metabolic syndrome) that contribute to cardiovascular health. The AHA Heart Disease and Stroke Statistical Update presents the latest data on a range of major clinical heart and circulatory disease conditions (including stroke, brain health, complications of pregnancy, kidney disease, congenital heart disease, rhythm disorders, sudden cardiac arrest, subclinical atherosclerosis, coronary heart disease, cardiomyopathy, heart failure, valvular disease, venous thromboembolism, and peripheral artery disease) and the associated outcomes (including quality of care, procedures, and economic costs).

METHODS

The AHA, through its Epidemiology and Prevention Statistics Committee, continuously monitors and evaluates sources of data on heart disease and stroke in the United States and globally to provide the most current information available in the annual Statistical Update with review of published literature through the year before writing. The 2024 AHA Statistical Update is the product of a full year's worth of effort in 2023 by dedicated volunteer clinicians and scientists, committed government professionals, and AHA staff members. The AHA strives to further understand and help heal health problems inflicted by structural racism, a public health crisis that can significantly damage physical and mental health and perpetuate disparities in access to health care, education, income, housing, and several other factors vital to healthy lives. This year's edition includes additional global data, as well as data on the monitoring and benefits of cardiovascular health in the population, with an enhanced focus on health equity across several key domains.

RESULTS

Each of the chapters in the Statistical Update focuses on a different topic related to heart disease and stroke statistics.

CONCLUSIONS

The Statistical Update represents a critical resource for the lay public, policymakers, media professionals, clinicians, health care administrators, researchers, health advocates, and others seeking the best available data on these factors and conditions.

A potent and selective cis-amide inhibitor of ryanodine receptor 2 as a candidate for cardiac arrhythmia treatment

Ryanodine receptor 2 (RyR2) is a Ca2+ release channel mainly located on the sarcoplasmic reticulum (SR) membrane of heart muscle cells and regulates the concentration of Ca2+ in the cytosol. RyR2 overactivation causes potentially lethal cardiac arrhythmias, but no specific inhibitor is yet available. Herein we developed the first highly potent and selective RyR2 inhibitor, TMDJ-035, containing 3,5-difluoro substituents on the A ring and a 4-fluoro substituent on the B ring, based on a comprehensive structure-activity relationship (SAR) study of tetrazole compound 1. The SAR study also showed that the amide conformation is critical for inhibitory potency. Single-crystal X-ray diffraction analysis and variable-temperature 1H NMR revealed that TMDJ-035 strongly favors cis-amide configuration, while the inactive analogue TMDJ-011 with a secondary amide takes trans-amide configuration. Examination of the selectivity among RyRs indicated that TMDJ-035 displayed high selectivity for RyR2. TMDJ-035 suppressed abnormal Ca2+ waves and transients in isolated cardiomyocytes from RyR2-mutated mice. It appears to be a promising candidate drug for treating cardiac arrhythmias due to RyR2 overactivation, as well as a tool for studying the mechanism and dynamics of RyR2 channel gating.

Clinical and genetic characteristics of catecholaminergic polymorphic ventricular tachycardia combined with left ventricular non-compaction

BACKGROUND

Catecholaminergic polymorphic ventricular tachycardia is an ion channelopathy, caused by mutations in genes coding for calcium-handling proteins. It can coexist with left ventricular non-compaction. We aim to investigate the clinical and genetic characteristics of this co-phenotype.

METHODS

Medical records of 24 patients diagnosed with catecholaminergic polymorphic ventricular tachycardia in two Chinese hospitals between September, 2005, and January, 2020, were retrospectively reviewed. We evaluated their clinical and genetic characteristics, including basic demographic data, electrocardiogram parameters, medications and survival during follow-up, and their gene mutations. We did structural analysis for a novel variant ryanodine receptor 2-E4005V.

RESULTS

The patients included 19 with catecholaminergic polymorphic ventricular tachycardia mono-phenotype and 5 catecholaminergic polymorphic ventricular tachycardia-left ventricular non-compaction overlap patients. The median age of onset symptoms was 9.0 (8.0,13.5) years. Most patients (91.7%) had cardiac symptoms, and 50% had a family history of syncope. Overlap patients had lower peak heart rate and threshold heart rate for ventricular tachycardia and ventricular premature beat during the exercise stress test (p < 0.05). Sudden cardiac death risk may be higher in overlap patients during follow-up. Gene sequencing revealed 1 novel ryanodine receptor 2 missense mutation E4005V and 1 mutation previously unreported in catecholaminergic polymorphic ventricular tachycardia, but no left ventricular non-compaction-causing mutations were observed. In-silico analysis showed the novel mutation E4005V broke down the interaction between two charged residues.

CONCLUSIONS

Catecholaminergic polymorphic ventricular tachycardia overlapping with left ventricular non-compaction may lead to ventricular premature beat/ventricular tachycardia during exercise stress test at lower threshold heart rate than catecholaminergic polymorphic ventricular tachycardia alone; it may also indicate a worse prognosis and requires strict follow-up. ryanodine receptor 2 mutations disrupted interactions between residues and may interfere the function of ryanodine receptor 2.

Athletes and suspected catecholaminergic polymorphic ventricular tachycardia: Awareness and current knowledge

INTRODUCTION

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a cardiac inherited arrhythmogenic disease potentially leading to sudden cardiac death that is determined by electrical instability exacerbated by acute adrenergic tone.

METHODS AND RESULTS

Despite its life-threatening nature, CPVT remains potentially unnoticed since diagnosis may be difficult especially in apparently healthy athletes. This review summarizes current knowledge and shortcomings of CPVT, focusing on genetics, arrhythmic mechanisms, sport preparticipation screening, and current recommendations.

CONCLUSIONS

The paper captures the importance of CPVT athletes regarding the necessity of risk stratification, as well as the importance of maintaining a healthy lifestyle.

Heart Disease and Stroke Statistics-2023 Update: A Report From the American Heart Association

BACKGROUND

The American Heart Association, in conjunction with the National Institutes of Health, annually reports the most up-to-date statistics related to heart disease, stroke, and cardiovascular risk factors, including core health behaviors (smoking, physical activity, diet, and weight) and health factors (cholesterol, blood pressure, and glucose control) that contribute to cardiovascular health. The Statistical Update presents the latest data on a range of major clinical heart and circulatory disease conditions (including stroke, congenital heart disease, rhythm disorders, subclinical atherosclerosis, coronary heart disease, heart failure, valvular disease, venous disease, and peripheral artery disease) and the associated outcomes (including quality of care, procedures, and economic costs).

METHODS

The American Heart Association, through its Epidemiology and Prevention Statistics Committee, continuously monitors and evaluates sources of data on heart disease and stroke in the United States to provide the most current information available in the annual Statistical Update with review of published literature through the year before writing. The 2023 Statistical Update is the product of a full year's worth of effort in 2022 by dedicated volunteer clinicians and scientists, committed government professionals, and American Heart Association staff members. The American Heart Association strives to further understand and help heal health problems inflicted by structural racism, a public health crisis that can significantly damage physical and mental health and perpetuate disparities in access to health care, education, income, housing, and several other factors vital to healthy lives. This year's edition includes additional COVID-19 (coronavirus disease 2019) publications, as well as data on the monitoring and benefits of cardiovascular health in the population, with an enhanced focus on health equity across several key domains.

RESULTS

Each of the chapters in the Statistical Update focuses on a different topic related to heart disease and stroke statistics.

CONCLUSIONS

The Statistical Update represents a critical resource for the lay public, policymakers, media professionals, clinicians, health care administrators, researchers, health advocates, and others seeking the best available data on these factors and conditions.

Clinical Characteristics, Genetic Findings and Arrhythmic Outcomes of Patients with Catecholaminergic Polymorphic Ventricular Tachycardia from China: A Systematic Review

INTRODUCTION

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a rare inherited cardiac ion channelopathy. The present study aims to examine the clinical characteristics, genetic basis, and arrhythmic outcomes of CPVT patients from China to elucidate the difference between CPVT patients in Asia and Western countries.

METHODS

PubMed and Embase were systematically searched for case reports or series reporting on CPVT patients from China until 19 February 2022 using the keyword: "Catecholaminergic Polymorphic Ventricular Tachycardia" or "CPVT", with the location limited to: "China" or "Hong Kong" or "Macau" in Embase, with no language or publication-type restriction. Articles that did not state a definite diagnosis of CPVT and articles with duplicate cases found in larger cohorts were excluded. All the included publications in this review were critically appraised based on the Joanna Briggs Institute Critical Appraisal Checklist. Clinical characteristics, genetic findings, and the primary outcome of spontaneous ventricular tachycardia/ventricular fibrillation (VT/VF) were analyzed.

RESULTS

A total of 58 unique cases from 15 studies (median presentation age: 8 (5.0-11.8) years old) were included. All patients, except one, presented at or before 19 years of age. There were 56 patients (96.6%) who were initially symptomatic. Premature ventricular complexes (PVCs) were present in 44 out of 51 patients (86.3%) and VT in 52 out of 58 patients (89.7%). Genetic tests were performed on 54 patients (93.1%) with a yield of 87%. RyR2, CASQ2, TERCL, and SCN10A mutations were found in 35 (71.4%), 12 (24.5%), 1 (0.02%) patient, and 1 patient (0.02%), respectively. There were 54 patients who were treated with beta-blockers, 8 received flecainide, 5 received amiodarone, 2 received verapamil and 2 received propafenone. Sympathectomy (n = 10), implantable cardioverter-defibrillator implantation (n = 8) and ablation (n = 1) were performed. On follow-up, 13 patients developed VT/VF.

CONCLUSION

This was the first systematic review of CPVT patients from China. Most patients had symptoms on initial presentation, with syncope as the presenting complaint. RyR2 mutation accounts for more than half of the CPVT cases, followed by CASQ2, TERCL and SCN10A mutations.

Latent Causes of Sudden Cardiac Arrest

Inherited arrhythmia syndromes are a common cause of apparently unexplained cardiac arrest or sudden cardiac death. These include long QT syndrome and Brugada syndrome, with a well-recognized phenotype in most patients with sufficiently severe disease to lead to cardiac arrest. Less common and typically less apparent conditions that may not be readily evident include catecholaminergic polymorphic ventricular tachycardia, short QT syndrome and early repolarization syndrome. In cardiac arrest patients whose extensive testing does not reveal an underlying etiology, a diagnosis of idiopathic ventricular fibrillation or short-coupled ventricular fibrillation is assigned. This review summarizes our current understanding of the less common inherited arrhythmia syndromes and provides clinicians with a practical approach to diagnosis and management.

Impact of cascade screening for catecholaminergic polymorphic ventricular tachycardia type 1

Objective

Human cardiac ryanodine receptor 2 (RYR2) shows autosomal-dominant inheritance in catecholaminergic polymorphic ventricular tachycardia type 1 (CPVT1); however, de novo variants have been observed in sporadic cases. Here, we investigated CPVT1-related RYR2 variant inheritance and its clinical significance between familial and de novo cases.

Methods

We enrolled 82 independent CPVT1 probands (median age: 10.0 (7.0–13.0) years; 45 male) carrying the RYR2 variants and whose biological origin could be confirmed by parental genetic analysis: assured familial inheritance (familial group: n=24) and de novo variants (de novo group: n=58). We examined the clinical characteristics of the probands and their family members carrying the RYR2 variants.

Results

In the de novo group, the RYR2 variants were more likely located in the C-terminus domain and less likely in the N-terminus domain than those in the familial group. The cumulative incidence of the first cardiac events (syncope and cardiac arrest (CA) or CA only) of the probands at the age of 5 and 10 years was higher in the de novo group than in the familial group. Nearly half of the probands in both groups experienced CA events before diagnosis. Only 37.5% of their genotype-positive parents had symptoms; however, at least 66.7% of the genotype-positive siblings were symptomatic.

Conclusions

CPVT1 probands harbouring de novo RYR2 variants showed an earlier onset of symptoms than those with assured familial inheritance. Cascade screening may enable early diagnosis, risk stratification and prophylactic therapeutic intervention to prevent sudden cardiac death of probands and potential genotype-positive family members.

Heart Disease and Stroke Statistics-2022 Update: A Report From the American Heart Association

BACKGROUND

The American Heart Association, in conjunction with the National Institutes of Health, annually reports the most up-to-date statistics related to heart disease, stroke, and cardiovascular risk factors, including core health behaviors (smoking, physical activity, diet, and weight) and health factors (cholesterol, blood pressure, and glucose control) that contribute to cardiovascular health. The Statistical Update presents the latest data on a range of major clinical heart and circulatory disease conditions (including stroke, congenital heart disease, rhythm disorders, subclinical atherosclerosis, coronary heart disease, heart failure, valvular disease, venous disease, and peripheral artery disease) and the associated outcomes (including quality of care, procedures, and economic costs).

METHODS

The American Heart Association, through its Statistics Committee, continuously monitors and evaluates sources of data on heart disease and stroke in the United States to provide the most current information available in the annual Statistical Update. The 2022 Statistical Update is the product of a full year's worth of effort by dedicated volunteer clinicians and scientists, committed government professionals, and American Heart Association staff members. This year's edition includes data on the monitoring and benefits of cardiovascular health in the population and an enhanced focus on social determinants of health, adverse pregnancy outcomes, vascular contributions to brain health, and the global burden of cardiovascular disease and healthy life expectancy.

RESULTS

Each of the chapters in the Statistical Update focuses on a different topic related to heart disease and stroke statistics.

CONCLUSIONS

The Statistical Update represents a critical resource for the lay public, policymakers, media professionals, clinicians, health care administrators, researchers, health advocates, and others seeking the best available data on these factors and conditions.

The link between abnormalities of calcium handling proteins and catecholaminergic polymorphic ventricular tachycardia

Catecholaminergic polymorphic ventricular tachycardia (CPVT), a rare autosomal dominant or recessive disease, usually results in syncope or sudden cardiac death. Most CPVT patients do not show abnormal cardiac structure and electrocardiogram features and symptoms, usually onset during adrenergically mediated physiological conditions. CPVT tends to occur at a younger age and is not easy to be diagnosed and managed. The main cause of CPVT is associated with mishandling Ca²⁺ in cardiomyocytes. Intracellular Ca²⁺ is strictly controlled by a protein located in the sarcoplasm reticulum (SR), such as ryanodine receptor, histidine-rich Ca²⁺-binding protein, triadin, and junctin. Mutation in these proteins results in misfolding or malfunction of these proteins, thereby affecting their Ca²⁺-binding affinity, and subsequently disturbs Ca²⁺ homeostasis during excitation–contraction coupling (E-C coupling). Furthermore, transient disturbance of Ca²⁺ homeostasis increases membrane potential and causes Ca²⁺ store overload-induced Ca²⁺ release, which in turn leads to delayed after depolarization and arrhythmia. Previous studies have focused on the interaction between ryanodine receptors and protein kinase or phosphatase in the cytosol. However, recent studies showed the regulation signaling for ryanodine receptor not only from the cytosol but also within the SR. The changing of Ca²⁺ concentration is critical for protein interaction inside the SR which changes protein conformation to regulate the open probability of ryanodine receptors. Thus, it influences the threshold of Ca²⁺ released from the SR, making it easier to release Ca²⁺ during E-C coupling. In this review, we briefly discuss how Ca²⁺ handling protein variations affect the Ca²⁺ handling in CPVT.

Heart Disease and Stroke Statistics-2021 Update: A Report From the American Heart Association

BACKGROUND

The American Heart Association, in conjunction with the National Institutes of Health, annually reports the most up-to-date statistics related to heart disease, stroke, and cardiovascular risk factors, including core health behaviors (smoking, physical activity, diet, and weight) and health factors (cholesterol, blood pressure, and glucose control) that contribute to cardiovascular health. The Statistical Update presents the latest data on a range of major clinical heart and circulatory disease conditions (including stroke, congenital heart disease, rhythm disorders, subclinical atherosclerosis, coronary heart disease, heart failure, valvular disease, venous disease, and peripheral artery disease) and the associated outcomes (including quality of care, procedures, and economic costs).

METHODS

The American Heart Association, through its Statistics Committee, continuously monitors and evaluates sources of data on heart disease and stroke in the United States to provide the most current information available in the annual Statistical Update. The 2021 Statistical Update is the product of a full year's worth of effort by dedicated volunteer clinicians and scientists, committed government professionals, and American Heart Association staff members. This year's edition includes data on the monitoring and benefits of cardiovascular health in the population, an enhanced focus on social determinants of health, adverse pregnancy outcomes, vascular contributions to brain health, the global burden of cardiovascular disease, and further evidence-based approaches to changing behaviors related to cardiovascular disease.

RESULTS

Each of the 27 chapters in the Statistical Update focuses on a different topic related to heart disease and stroke statistics.

CONCLUSIONS

The Statistical Update represents a critical resource for the lay public, policy makers, media professionals, clinicians, health care administrators, researchers, health advocates, and others seeking the best available data on these factors and conditions.

Heart Disease and Stroke Statistics-2020 Update: A Report From the American Heart Association

BACKGROUND

The American Heart Association, in conjunction with the National Institutes of Health, annually reports on the most up-to-date statistics related to heart disease, stroke, and cardiovascular risk factors, including core health behaviors (smoking, physical activity, diet, and weight) and health factors (cholesterol, blood pressure, and glucose control) that contribute to cardiovascular health. The Statistical Update presents the latest data on a range of major clinical heart and circulatory disease conditions (including stroke, congenital heart disease, rhythm disorders, subclinical atherosclerosis, coronary heart disease, heart failure, valvular disease, venous disease, and peripheral artery disease) and the associated outcomes (including quality of care, procedures, and economic costs).

METHODS

The American Heart Association, through its Statistics Committee, continuously monitors and evaluates sources of data on heart disease and stroke in the United States to provide the most current information available in the annual Statistical Update. The 2020 Statistical Update is the product of a full year's worth of effort by dedicated volunteer clinicians and scientists, committed government professionals, and American Heart Association staff members. This year's edition includes data on the monitoring and benefits of cardiovascular health in the population, metrics to assess and monitor healthy diets, an enhanced focus on social determinants of health, a focus on the global burden of cardiovascular disease, and further evidence-based approaches to changing behaviors, implementation strategies, and implications of the American Heart Association's 2020 Impact Goals.

RESULTS

Each of the 26 chapters in the Statistical Update focuses on a different topic related to heart disease and stroke statistics.

CONCLUSIONS

The Statistical Update represents a critical resource for the lay public, policy makers, media professionals, clinicians, healthcare administrators, researchers, health advocates, and others seeking the best available data on these factors and conditions.

Catecholaminergic polymorphic ventricular tachycardia managed as orthostatic dysregulation and epilepsy in 11- and 15-year-old sisters

BACKGROUND

In pediatric patients, syncope commonly occurs as vasovagal syncope, or in epilepsy or orthostatic dysregulation. Cardiogenic syncope is rare but it is lethal, and needs to be promptly diagnosed and treated.

METHODS AND RESULTS

We describe the cases of 11- and 15-year-old sisters with frequent syncope during exercise and emotional stress since the age of 10 and 12, respectively. There were no abnormalities on 12-lead electrocardiogram (ECG) at rest. They were first diagnosed with orthostatic dysregulation and epilepsy. Because of recurrent exercise-induced syncope, cardiac examinations were performed. On treadmill exercise stress test, bidirectional ventricular tachycardia was induced in the 11-year-old girl, which degenerated into ventricular fibrillation; frequent polymorphic premature ventricular contractions were induced in her elder sister. They were diagnosed with catecholaminergic polymorphic ventricular tachycardia (CPVT) and started on oral beta-blockers and exercise restriction.

CONCLUSIONS

It is important to suspect CPVT in pediatric exercise-induced syncope, and to recognize that CPVT does not show ECG abnormalities at rest.

Novel approaches for the treatment of ventricular tachycardia

Ventricular tachycardia (VT) is a crucial cause of sudden cardiac death (SCD) and a primary cause of mortality and morbidity in patients with structural cardiac disease. VT includes clinical disorders varying from benign to life-threatening. Most life-threatening episodes are correlated with coronary artery disease, but the risk of SCD varies in certain populations, with various underlying heart conditions, specific family history, and genetic variants. The targets of VT management are symptom alleviation, improved quality of life, reduced implantable cardioverter defibrillator shocks, prevention of reduction of left ventricular function, reduced risk of SCD, and improved overall survival. Antiarrhythmic drug therapy and endocardial catheter ablation remains the cornerstone of guideline-endorsed VT treatment strategies in patients with structural cardiac abnormalities. Novel strategies such as epicardial ablation, surgical cryoablation, transcoronary alcohol ablation, pre-procedural imaging, and stereotactic ablative radiotherapy are an appealing area of research. In this review, we gathered all recent advances in innovative therapies as well as experimental evidence focusing on different aspects of VT treatment that could be significant for future favorable clinical applications.

Acute isoproterenol leads to age-dependent arrhythmogenesis in guinea pigs

Sudden cardiac death from ventricular arrhythmias is more common in adult patients with with heart failure compared with pediatric patients with heart failure. We identified age-specific differences in arrhythmogenesis using a guinea pig model of acute β-adrenergic stimulation. Young and adult guinea pigs were exposed to the β-adrenergic agonist isoproterenol (ISO; 0.7 mg/kg) for 30 min in the absence or presence of flecainide (20 mg/kg), an antiarrhythmic that blocks Na⁺ and ryanodine channels. Implanted cardiac monitors (Reveal LINQ, Medtronic) were used to monitor heart rhythm. Alterations in phosphorylation and oxidation of ryanodine receptor 2 (RyR2) were measured in left ventricular tissue. There were age-specific differences in arrhythmogenesis and sudden death associated with acute β-adrenergic stimulation in guinea pigs. Young and adult guinea pigs developed arrhythmias in response to ISO; however, adult animals developed significantly more premature ventricular contractions and experienced higher arrhythmia-related mortality than young guinea pigs treated with ISO. Although there were no significant differences in the phosphorylation of left ventricular RyR2 between young and adult guinea pigs, adult guinea pigs exposed to acute ISO had significantly more oxidation of RyR2. Flecainide treatment significantly improved survival and decreased the number of premature ventricular contractions in young and adult animals in association with lower RyR2 oxidation. Adult guinea pigs had a greater propensity to develop arrhythmias and suffer sudden death than young guinea pigs when acutely exposed to ISO. This was associated with higher oxidation of RyR2. The incidence of sudden death can be rescued with flecainide treatment, which decreases RyR2 oxidation. NEW & NOTEWORTHY Clinically, adult patients with heart failure are more likely to develop arrhythmias and sudden death than pediatric patients with heart failure. In the present study, older guinea pigs also showed a greater propensity to arrhythmias and sudden death than young guinea pigs when acutely exposed to isoproterenol. Although there are well-described age-related cardiac structural changes that predispose patients to arrhythmogenesis, the present data suggest contributions from dynamic changes in cellular signaling also play an important role in arrhythmogenesis.

Catecholaminergic polymorphic ventricular tachycardia: a model for genotype-specific therapy

PURPOSE OF REVIEW

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a life-threatening syndrome defined by exercise-induced or emotion-induced ventricular arrhythmias, typically caused by gain-of-function mutations in RYR2-encoded ryanodine receptor-2 (RyR2). This review will discuss recent advances and ongoing challenges in devising genotype-specific CPVT therapies.

RECENT FINDINGS

CPVT patients were once universally thought to be at high risk of sudden death; however, as more cases emerge, CPVT is being re-defined as a complex syndrome of variable expressivity. Treatment was traditionally limited to β-blockers and implantable cardioverter defibrillators, and although β-blockers remain a mainstay of treatment, implantable cardioverter defibrillator use is associated with adverse events and should be limited. New applications for older therapies, like flecainide and cardiac denervation, appear to better target the mechanistic basis of CPVT arrhythmias. Recent advances in our understanding of RyR2 structure and function can help in identifying novel therapeutic targets.

SUMMARY

CPVT is usually related to RyR2 or associated proteins. Emerging studies reveal several genotype-phenotype correlations, which may eventually influence therapeutic decision-making. Flecainide has improved CPVT outcomes and will likely have broader clinical indications in the near future. Gene therapy has shown promise in animal models but has yet to be studied in humans. Sudden death can occur as a sentinel symptom, making preventive therapy that targets molecular mechanism(s) of arrhythmia a key area of ongoing investigation. VIDEO ABSTRACT.

A delayed diagnosis of catecholaminergic polymorphic ventricular tachycardia with a mutant of RYR2 at c.7580T>G for 6 years in a 9-year-old child

RATIONALE

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a rare but potentially lethal inherited arrhythmia syndrome induced by adrenergic stress. Due to the atypical clinical manifestations in early age, limited recognition and experience of pediatric cardiologists, and low awareness of the significance of genetic diagnosis in some underdeveloped areas in China, a delayed or missed diagnosis of CPVT in children is common and concerning.

PATIENT CONCERNS

A 9-year and 3-month male child with recurrent exercise-induced syncope accompanied by convulsion was initially misdiagnosed as epilepsy since the first manifestation at the age of 3 years. Due to the identification of polymorphic ventricular premature beats, nonsustained ventricular tachycardia (VT), and supraventricular tachycardia, a cardiogenic etiology was established. The patient received a successive treatment by propafenone, amiodarone, a combination of amiodarone with metoprolol, and metoprolol alone for up to 6 years.

DIAGNOSES

Given the poor response to conventional antiarrhythmics, excise-induced syncope, QRS morphology and a structurally normal heart, the diagnosis of CPVT was suspected, and ultimately confirmed by detection of polymorphic and bidirectional VT with degeneration into ventricular fibrillation during exercise testing. In addition, a heterozygous mutant of RYR2 at c.7580T > G was identified by genetic testing.

INTERVENTIONS

Due to the unavailability of flecainide in China and the refusal of implantable cardioverter defibrillator implantation by his parents, this patient continued to be treated with oral metoprolol.

OUTCOMES

Unfortunately, the effect was unfavorable during 4 months outpatient follow-up.

LESSONS

CPVT should be suspected in young patients with a normal baseline electrocardiogram (EKG), a structurally normal heart and polymorphic and/or bidirectional ventricular tachycardia induced by exercise or emotional stress. Exercise and genetic testing is essential and significant for a timely and accurate diagnosis of CPVT. The current study firstly reported a case with CPVT associated with a mutant of RYR2 at c.7580T > G in children.

Syncope in patients with inherited arrhythmias

Syncope, a common symptom of cerebral ischemia often shows a multifactorial etiopathogenesis. Although inherited arrhythmias causing syncope is uncommon, such an occurrence could be a warning sign preceding cardiac arrest. Long QT syndrome (LQTS) is a typical inherited arrhythmia causing syncope in children. Early diagnosis and treatment of LQTS using beta-blockers prevents recurrent syncope in LQTS. Brugada syndrome, another typical inherited arrhythmia causes syncope or sudden cardiac arrest in young individuals. Syncope as a symptom is useful for risk stratification of fatal arrhythmias and in selection of appropriate therapy. Catecholaminergic polymorphic ventricular tachycardia, another rare inherited arrhythmia causing recurrent syncope is associated with poor outcomes without medication. Early detection and therapeutic intervention improve prognosis; thus, correct diagnosis of syncope is imperative in cases of these inherited arrhythmias. We describe syncope associated with three typical inherited arrhythmias and discuss various diagnostic modalities.

Genomic-based diagnosis of arrhythmia disease in a personalized medicine era

INTRODUCTION

Although thousands of potentially disease-causing mutations have been identified in a handful of genes, the genetic heterogeneity has led to diagnostic confusions, stemming directly from the limitations in our arsenal of genetic tools.

AREAS COVERED

We discuss the genetic basis of cardiac ion channelopathies, the gaps in our knowledge and how Next-generation sequencing technology (NGS) and can be used to bridge them, and how induced pluripotent stem cell (iPSC) derived-cardiomyocytes can be used for drug discovery.

EXPERT COMMENTARY

Univariate, arrhythmogenic arrhythmias can explain some congenital arrhythmias, however, it is far from a comprehensive understanding of the complexity of many arrhythmias. Mutational screening is a critical step in personalized medicine and is critical to the management of patients with arrhythmias. The success of personalized medicine requires a more efficient way to identify a high number of genetic variants potentially implicated in cardiac arrhythmogenic diseases than traditional sequencing methods (eg, Sanger sequencing). Next-generation sequencing technology provides us with unprecedented opportunities to achieve high-throughput, rapid, and cost-effective detection of congenital arrhythmias in patients. Moreover, in personalized medicine era, IPSC derived-cardiomyocytes can be used as 'cardiac arrhythmia in a dish' model for drug discovery, and help us improve management of arrhythmias in patients by developing patient-specific drug therapies with target specificity.