Efficacy and safety of bepridil for prevention of ICD shocks in patients with Brugada syndrome and idiopathic ventricular fibrillation

The proarrhythmogenic role of autonomics and emerging neuromodulation approaches to prevent sudden death in cardiac ion channelopathies

Ventricular arrhythmias in cardiac channelopathies are linked to autonomic triggers, which are sub-optimally targeted in current management strategies. Improved molecular understanding of cardiac channelopathies and cellular autonomic signalling could refine autonomic therapies to target the specific signalling pathways relevant to the specific aetiologies as well as the central nervous system centres involved in the cardiac autonomic regulation. This review summarizes key anatomical and physiological aspects of the cardiac autonomic nervous system and its impact on ventricular arrhythmias in primary inherited arrhythmia syndromes. Proarrhythmogenic autonomic effects and potential therapeutic targets in defined conditions including the Brugada syndrome, early repolarization syndrome, long QT syndrome, and catecholaminergic polymorphic ventricular tachycardia will be examined. Pharmacological and interventional neuromodulation options for these cardiac channelopathies are discussed. Promising new targets for cardiac neuromodulation include inhibitory and excitatory G-protein coupled receptors, neuropeptides, chemorepellents/attractants as well as the vagal and sympathetic nuclei in the central nervous system. Novel therapeutic strategies utilizing invasive and non-invasive deep brain/brain stem stimulation as well as the rapidly growing field of chemo-, opto-, or sonogenetics allowing cell-specific targeting to reduce ventricular arrhythmias are presented.

Effects of bepridil on early cardiac development of zebrafish

Bepridil is a commonly used medication for arrhythmia and heart failure. It primarily exerts hemodynamic effects by inhibiting Na⁺/K⁺ movement and regulating the Na⁺/Ca²⁺ exchange. In comparison to other Ca²⁺ inhibitors, bepridil has a long half-life and a complex pharmacology. Additionally, it is widely used in antiviral research and the treatment of various diseases. However, the toxicity of this compound and its other possible effects on embryonic development are unknown. In this study, we investigated the toxicity of bepridil on rat myocardial H9c2 cells. After treatment with bepridil, the cells became overloaded with Ca²⁺ and entered a state of cytoplasmic vacuolization and nuclear abnormality. Bepridil treatment resulted in several morphological abnormalities in zebrafish embryo models, including pericardium enlargement, yolk sac swelling, and growth stunting. The hemodynamic effects on fetal development resulted in abnormal cardiovascular circulation and myocardial weakness. After inhibiting the Ca²⁺ transmembrane, the liver of zebrafish larvae also displayed an ectopic and deficient spatial location. Additionally, the results of the RNA-seq analysis revealed the detailed gene expression profiles and metabolic responses to bepridil treatment in zebrafish embryonic development. Taken together, our study provides an important evaluation of antiarrhythmic agents for clinical use in prenatal heart patients.

Brugada syndrome: A comprehensive review of pathophysiological mechanisms and risk stratification strategies

Brugada syndrome (BrS) is an inherited ion channel channelopathy predisposing to ventricular arrhythmias and sudden cardiac death. Originally believed to be predominantly associated with mutations in SCN5A encoding for the cardiac sodium channel, mutations of 18 genes other than SCN5A have been implicated in the pathogenesis of BrS to date. Diagnosis is based on the presence of a spontaneous or drug-induced coved-type ST segment elevation. The predominant electrophysiological mechanism underlying BrS remains disputed, commonly revolving around the three main hypotheses based on abnormal repolarization, depolarization or current-load match. Evidence from computational modelling, pre-clinical and clinical studies illustrates that molecular abnormalities found in BrS lead to alterations in excitation wavelength (λ), which ultimately elevates arrhythmic risk. A major challenge for clinicians in managing this condition is the difficulty in predicting the subset of patients who will suffer from life-threatening ventricular arrhythmic events. Several repolarization risk markers have been used thus far, but these neglect the contributions of conduction abnormalities in the form of slowing and dispersion. Indices incorporating both repolarization and conduction based on the concept of λ have recently been proposed. These may have better predictive values than the existing markers. Current treatment options include pharmacological therapy to reduce the occurrence of arrhythmic events or to abort these episodes, and interventions such as implantable cardioverter-defibrillator insertion or radiofrequency ablation of abnormal arrhythmic substrate.

Atrial fibrillation and risk of major arrhythmic events in Brugada syndrome: A meta-analysis

BACKGROUND

Brugada syndrome (BrS) is a common cause of sudden cardiac death (SCD). There is recent evidence that atrial fibrillation (AF) is associated with increased risk of SCD in general population. However, whether AF increases a risk of major arrhythmic events (MAE) in patients with BrS is still unclear. We performed a systematic review and meta-analysis to explore the effect of AF on MAE in BrS population.

METHODS

We searched the databases of MEDLINE and EMBASE from inception to March 2019. Included studies were published cohort studies reporting rates of MAE (ventricular fibrillation, sustained ventricular tachycardia, SCD, or sudden cardiac arrest) in BrS patients, with and without previous documented AF. Data from each study were combined using the random-effects model.

RESULTS

Six studies from 1,703 patients were included. There was a significant association between AF and an increased risk of MAE in patients with BrS (pooled OR = 2.37, 95% CI = 1.36-4.13, p-value = .002, I²  = 40.3%).

CONCLUSIONS

Our meta-analysis demonstrated that AF is associated with an increased risk of MAE in patients with BrS.

Brugada Syndrome: Progress in Genetics, Risk Stratification and Management

Brugada syndrome (BrS) is one of the most common causes of sudden cardiac death in normal structural heart individuals. First characterised in 1992, the global prevalence of BrS is unclear, with estimates placing it at around 0.05% and presenting most frequently in southeast Asian countries. This review aims to summarise the development in the understanding of BrS and, importantly, progress in its management, underpinned by knowledge regarding its genetics and molecular mechanisms. It also provides update on risk stratification and promising new therapies for BrS, including epicardial ablation. Future studies are required to increase understanding of the pathogenesis of this disease and to guide clinical practice.

Ablation of atrial fibrillation in patients with Brugada syndrome: A systematic review of the literature

Supraventricular arrhythmias are common in Brugada syndrome (BS), and notoriously difficult to manage with medical therapy secondary to associated risks. Pulmonary vein isolation (PVI) is often utilized instead, but its outcomes in this population are not well-known. We aim to provide a holistic evaluation of interventional treatment for Atrial fibrillation (AF) in the BS population. Electronic databases Medline, Embase, Cinahl, Cochrane, and Scopus were systematically searched for publications between 01/01/1995 and 12/31/2017. Studies were screened based on predefined inclusion and exclusion criteria. A total of 49 patients with BS and AF were included. Age range from 28.8 to 64 years, and 77.5% were male. 38 patients were implanted with implantable cardioverter-defibrillators (ICD) at baseline, and of them, 39% suffered inappropriate shocks for rapid AF. 34/49 (69%) of patients achieved remission following a single PVI procedure. Of the remaining, 13 patients underwent one or more repeat ablation procedures. Overall, 45/49 (91.8%) of patients remained in remission during long-term follow-up after one or more PVI procedures in the absence of antiarrhythmic drug (AAD) therapy. Postablation, no patients suffered inappropriate ICD shock. Furthermore, no major complications secondary to PVI occurred in any patient. AF ablation achieves acute and long-term success in the vast majority of patients. It is effective in preventing inappropriate ICD therapy secondary to rapid AF. Complication rates of PVI in BS are low. Thus, in light of the risks of AADs and risk of inappropriate ICD shocks in the BS population, catheter ablation could represent an appropriate first-line therapy for paroxysmal atrial fibrillation in BS patients.

J wave syndromes as a cause of malignant cardiac arrhythmias

The J wave syndromes, including the Brugada (BrS) and early repolarization (ERS) syndromes, are characterized by the manifestation of prominent J waves in the electrocardiogram appearing as an ST segment elevation and the development of life-threatening cardiac arrhythmias. BrS and ERS differ with respect to the magnitude and lead location of abnormal J waves and are thought to represent a continuous spectrum of phenotypic expression termed J wave syndromes. Despite over 25 years of intensive research, risk stratification and the approach to therapy of these two inherited cardiac arrhythmia syndromes are still rapidly evolving. Our objective in this review is to provide an integrated synopsis of the clinical characteristics, risk stratifiers, as well as the molecular, ionic, cellular, and genetic mechanisms underlying these two syndromes that have captured the interest and attention of the cardiology community over the past two decades.

Recent advances in the treatment of Brugada syndrome

INTRODUCTION

Brugada syndrome (BrS) is an inherited cardiac arrhythmia syndrome characterized by ST-segment elevation in right precordial ECG leads and associated with sudden cardiac death in young adults. The ECG manifestations of BrS are often concealed but can be unmasked by sodium channel blockers and fever. Areas covered: Implantation of a cardioverter defibrillator (ICD) is first-line therapy for BrS patients presenting with prior cardiac arrest or documented VT. A pharmacological approach to therapy is recommended in cases of electrical storm, as an adjunct to ICD and as preventative therapy. The goal of pharmacological therapy is to produce an inward shift to counter the genetically-induced outward shift of ion channel current flowing during the early phases of the ventricular epicardial action potential. This is accomplished by augmentation of I_Ca using □□adrenergic agents or phosphodiesterase III inhibitors or via inhibition of I_to. Radiofrequency ablation of the right ventricular outward flow tract epicardium is effective in suppressing arrhythmogenesis in BrS patients experiencing frequent appropriate ICD-shocks. Expert commentary: Understanding of the pathophysiology and approach to therapy of BrS has advanced considerably in recent years, but there remains an urgent need for development of cardio-selective and ion-channel-specific I_to blockers for treatment of BrS.

Pharmacological Therapy in Brugada Syndrome

Brugada syndrome (BrS) is a cardiac disease caused by an inherited ion channelopathy associated with a propensity to develop ventricular fibrillation. Implantable cardioverter defibrillator implantation is recommended in BrS, based on the clinical presentation in the presence of diagnostic ECG criteria. Implantable cardioverter defibrillator implantation is not always indicated or sufficient in BrS, and is associated with a high device complication rate. Pharmacological therapy aimed at rebalancing the membrane action potential can prevent arrhythmogenesis in BrS. Quinidine, a class 1A antiarrhythmic drug with significant Ito blocking properties, is the most extensively used drug for the prevention of arrhythmias in BrS. The present review provides contemporary data gathered on all drugs effective in the therapy of BrS, and on ineffective or contraindicated antiarrhythmic drugs.

Brugada Syndrome:Risk Stratification And Management

The Brugada syndrome (BrS) is an arrhythmogenic disease associated with an increased risk of ventricular fibrillation and sudden cardiac death. The risk stratification and management of BrS patients, particularly of asymptomatic ones, still remains challenging. A previous history of aborted sudden cardiac death or arrhythmic syncope in the presence of spontaneous type 1 ECG pattern of BrS phenotype appear to be the most reliable predictors of future arrhythmic events. Several other ECG parameters have been proposed for risk stratification. Among these ECG markers, QRS-fragmentation appears very promising. Although the value of electrophysiological study still remains controversial, it appears to add important information on risk stratification, particularly when incorporated in multiparametric scores in combination with other known risk factors. The present review article provides an update on the pathophysiology, risk stratification and management of patients with BrS.

Brugada Syndrome: Clinical, Genetic, Molecular, Cellular, and Ionic Aspects

Brugada syndrome (BrS) is an inherited cardiac arrhythmia syndrome first described as a new clinical entity in 1992. Electrocardiographically characterized by distinct coved type ST segment elevation in the right-precordial leads, the syndrome is associated with a high risk for sudden cardiac death in young adults, and less frequently in infants and children. The electrocardiographic manifestations of BrS are often concealed and may be unmasked or aggravated by sodium channel blockers, a febrile state, vagotonic agents, as well as by tricyclic and tetracyclic antidepressants. An implantable cardioverter defibrillator is the most widely accepted approach to therapy. Pharmacologic therapy is designed to produce an inward shift in the balance of currents active during the early phases of the right ventricular action potential (AP) and can be used to abort electrical storms or as an adjunct or alternative to device therapy when use of an implantable cardioverter defibrillator is not possible. Isoproterenol, cilostazol, and milrinone boost calcium channel current and drugs like quinidine, bepridil, and the Chinese herb extract Wenxin Keli inhibit the transient outward current, acting to diminish the AP notch and thus to suppress the substrate and trigger for ventricular tachycardia or fibrillation. Radiofrequency ablation of the right ventricular outflow tract epicardium of patients with BrS has recently been shown to reduce arrhythmia vulnerability and the electrocardiographic manifestation of the disease, presumably by destroying the cells with more prominent AP notch. This review provides an overview of the clinical, genetic, molecular, and cellular aspects of BrS as well as the approach to therapy.

Long-Term Outcome of Patients With Idiopathic Ventricular Fibrillation: A Meta-Analysis

BACKGROUND

The long-term outcome of the patients with idiopathic ventricular fibrillation (IVF) is not well known.

METHODS AND RESULTS

Relevant studies published through May 21, 2014 were searched and identified in the MEDLINE, PsycINFO, Cochrane Library, CINAHL, and EMBASE databases and a hand search of article references was also performed. Random-effect models were used for pooling proportions of mortality and recurrent events. Twenty-three studies were included with a total of 639 patients (449 males) with a mean age ranging from 33 to 51 years. Eighty percent of patients had received ICD implantation. Over an average of 5.3 years follow-up, 167 patients (31%) experienced a recurrence of ventricular arrhythmic events (proportion, 0.29 [95% CI 0.21-0.38]). Moreover, 17 patients (3.1%) died among all studies (proportion, 0.01 [95% CI 0.00-0.04]). No association was found between the induction of sustained ventricular tachycardia or ventricular fibrillation at baseline electrophysiological study and risk of recurrent ventricular arrhythmias (risk difference: 0.12 [95% CI, 0.08-0.32]).

CONCLUSIONS

In patients with IVF, this meta-analysis revealed an estimated recurrent event rate of 31% and a pooled mortality rate of 3.1% during an average of 5 years follow-up. The results of baseline electrophysiological studies are not predictive of future ventricular arrhythmias.

J-wave syndromes: Brugada and early repolarization syndromes

A prominent J wave is encountered in a number of life-threatening cardiac arrhythmia syndromes, including the Brugada syndrome and early repolarization syndromes. Brugada syndrome and early repolarization syndromes differ with respect to the magnitude and lead location of abnormal J waves and are thought to represent a continuous spectrum of phenotypic expression termed J-wave syndromes. Despite two decades of intensive research, risk stratification and the approach to therapy of these 2 inherited cardiac arrhythmia syndromes are still undergoing rapid evolution. Our objective in this review is to provide an integrated synopsis of the clinical characteristics, risk stratifiers, and molecular, ionic, cellular, and genetic mechanisms underlying these 2 fascinating syndromes that have captured the interest and attention of the cardiology community in recent years.

Novel Therapeutic Strategies for the Management of Ventricular Arrhythmias Associated with the Brugada Syndrome

INTRODUCTION

Brugada syndrome (BrS) is an inherited cardiac arrhythmia syndrome characterized by prominent J waves appearing as distinct coved type ST segment elevation in the right precordial leads of the ECG. It is associated with a high risk for sudden cardiac death.

AREAS COVERED

We discuss 1) ECG manifestations of BrS which can be unmasked or aggravated by sodium channel blockers, febrile states, vagotonic agents, as well as tricyclic and tetracyclic antidepressants; 2) Genetic basis of BrS; 3) Ionic and cellular mechanisms underlying BrS; 4) Therapy involving devices including an implantable cardioverter defibrillator (ICD); 5) Therapy involving radiofrequency ablation; and 6) Therapy involving pharmacological therapy which is aimed at producing an inward shift in the balance of the currents active during phase 1 of the right ventricular action potential either by boosting calcium channel current (isoproterenol, cilostazol and milrinone) or by inhibition of transient outward current Ito (quinidine, bepridil and the Chinese herb extract Wenxin Keli).

EXPERT OPINION

This review provides an overview of the clinical and molecular aspects of BrS with a focus on approaches to therapy. Available data suggest that agents capable of inhibiting the transient outward current Ito can exert an ameliorative effect regardless of the underlying cause.

Unveiling specific triggers and precipitating factors for fatal cardiac events in inherited arrhythmia syndromes

Patients with inherited arrhythmia syndromes, such as long QT syndrome, Brugada syndrome, early repolarization syndrome, catecholaminergic polymorphic ventricular tachycardia, and their latent forms, are at risk for fatal arrhythmias. These diseases are typically associated with genetic mutations that perturb cardiac ionic currents. The analysis of cardiac events by genotype-phenotype correlation studies has revealed that fatal arrhythmias in some genotypes are triggered by physical or emotional stress, and those in the others are more likely to occur during sleep or at rest. Thus, the risk stratification and management of affected patients differ strikingly according to the genetic variant of the inherited arrhythmia syndrome. Risk stratification may be further refined by considering the precipitating factors, such as drugs, bradycardia, electrolyte disturbances, fever, and cardiac memory. Moreover, an increasing number of studies imply that the susceptibility of fatal arrhythmias in patients with acute coronary syndrome or takotsubo cardiomyopathy is at least partly ascribed to the genetic variants causing inherited arrhythmia syndromes. In this article, we review the recent advances in the understanding of the molecular genetics and genotype-phenotype correlations in inherited arrhythmia syndromes and consider the triggers and precipitating factors for fatal arrhythmias in these disorders. Further studies to explore the triggers and precipitating factors specific to the genotypes and diseases are needed for better clinical management.

Electrical storm in patients with brugada syndrome is associated with early repolarization

BACKGROUND

Electrical storms (ESs) in patients with Brugada syndrome (BrS) are rare though potentially lethal.

METHODS AND RESULTS

We studied 22 men with BrS and ES, defined as ≥3 episodes/d of ventricular fibrillation (VF) and compared their characteristics with those of 110 age-matched, control men with BrS without ES. BrS was diagnosed by a spontaneous or drug-induced type 1 pattern on the ECG in the absence of structural heart disease. Early repolarization (ER) was diagnosed by J waves, ie, >0.1 mV notches or slurs of the terminal portion of the QRS complex. The BrS ECG pattern was provoked with pilsicainide. A spontaneous type I ECG pattern, J waves, and horizontal/descending ST elevation were found, respectively, in 77%, 36%, and 88% of patients with ES, versus 28% (P<0.0001), 9% (P=0.003), and 60% (P=0.06) of controls. The J-wave amplitude was significantly higher in patients with than without ES (P=0.03). VF occurred during undisturbed sinus rhythm in 14 of 19 patients (74%), and ES were controlled by isoproterenol administration. All patients with ES received an implantable cardioverter defibrillator and over a 6.0±5.4 years follow-up, the prognosis of patients with ES was significantly worse than that of patients without ES. Bepridil was effective in preventing VF in 6 patients.

CONCLUSIONS

A high prevalence of ER was found in a subgroup of patients with BrS associated with ES. ES appeared to be suppressed by isoproterenol or quinidine, whereas bepridil and quinidine were effective in the long-term prevention of VF in the highest-risk patients.