Pharmacological Therapy in Brugada Syndrome

The Novel Familial ST-Depression Syndrome - Current Knowledge and Perspectives

Familial ST-depression syndrome represents a novel inherited disease characterized by nonischemic ST-segment depressions in multiple leads. The ECG phenotype appears to debut around puberty, while the typical onset of arrhythmias occurs around 50 years of age. Clinical manifestations include supraventricular arrhythmias, fast polymorphic ventricular tachycardia, sudden cardiac death, and left ventricular systolic dysfunction. The optimal treatment is unknown but asymptomatic individuals without red flags may not need treatment. In contrast, ICD implantation should be considered in patients with probable arrhythmic syncope and in those fulfilling general criteria for ICD treatment. Future research should focus on establishing the disease prevalence, optimizing risk stratification and treatment, and elucidating the underlying genetic etiology.

Patient-specific iPSC-derived cardiomyocytes reveal variable phenotypic severity of Brugada syndrome

BACKGROUND

Brugada syndrome (BrS) is a cardiac channelopathy that can result in sudden cardiac death (SCD). SCN5A is the most frequent gene linked to BrS, but the genotype-phenotype correlations are not completely matched. Clinical phenotypes of a particular SCN5A variant may range from asymptomatic to SCD. Here, we used comparison of induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) derived from a SCN5A mutation-positive (D356Y) BrS family with severely affected proband, asymptomatic mutation carriers (AMCs) and healthy controls to investigate this variation.

METHODS

26 iPSC lines were generated from skin fibroblasts using nonintegrated Sendai virus. The generated iPSCs were differentiated into cardiomyocytes using a monolayer-based differentiation protocol.

FINDINGS

D356Y iPSC-CMs exhibited increased beat interval variability, slower depolarization, cardiac arrhythmias, defects of Na+ channel function and irregular Ca2+ signaling, when compared to controls. Importantly, the phenotype severity observed in AMC iPSC-CMs was milder than that of proband iPSC-CMs, an observation exacerbated by flecainide. Interestingly, the iPSC-CMs of the proband exhibited markedly decreased Ca2+ currents in comparison with control and AMC iPSC-CMs. CRISPR/Cas9-mediated genome editing to correct D356Y in proband iPSC-CMs effectively rescued the arrhythmic phenotype and restored Na+ and Ca2+ currents. Moreover, drug screening using established BrS iPSC-CM models demonstrated that quinidine and sotalol possessed antiarrhythmic effects in an individual-dependent manner. Clinically, venous and oral administration of calcium partially reduced the malignant arrhythmic events of the proband in mid-term follow-up.

INTERPRETATION

Patient-specific and genome-edited iPSC-CMs can recapitulate the varying phenotypic severity of BrS. Our findings suggest that preservation of the Ca2+ currents might be a compensatory mechanism to resist arrhythmogenesis in BrS AMCs.

FUNDING

National Key R&D Program of China (2017YFA0103700), National Natural Science Foundation of China (81922006, 81870175), Natural Science Foundation of Zhejiang Province (LD21H020001, LR15H020001), National Natural Science Foundation of China (81970269), Key Research and Development Program of Zhejiang Province (2019C03022) and Natural Science Foundation of Zhejiang Province (LY16H020002).

ARumenamides: A novel class of potential antiarrhythmic compounds

Background: Most therapeutics targeting cardiac voltage-gated sodium channels (Nav1.5) attenuate the sodium current (INa) conducted through the pore of the protein. Whereas these drugs may be beneficial for disease states associated with gain-of-function (GoF) in Nav1.5, few attempts have been made to therapeutically treat loss-of-function (LoF) conditions. The primary impediment to designing efficacious therapies for LoF is a tendency for drugs to occlude the Nav1.5 central pore. We hypothesized that molecular candidates with a high affinity for the fenestrations would potentially reduce pore block.

Methods and Results: Virtual docking was performed on 21 compounds, selected based on their affinity for the fenestrations in Nav1.5, which included a class of sulfonamides and carboxamides we identify as ARumenamide (AR). Six ARs, AR-051, AR-189, AR-674, AR-802, AR-807 and AR-811, were further docked against Nav1.5 built on NavAb and rNav1.5. Based on the virtual docking results, these particular ARs have a high affinity for Domain III-IV and Domain VI-I fenestrations. Upon functional characterization, a trend was observed in the effects of the six ARs on INa. An inverse correlation was established between the aromaticity of the AR’s functional moieties and compound block. Due to its aromaticity, AR-811 blocked INa the least compared with other aromatic ARs, which also decelerated fast inactivation onset. AR-674, with its aliphatic functional group, significantly suppresses INa and enhances use-dependence in Nav1.5. AR-802 and AR-811, in particular, decelerated fast inactivation kinetics in the most common Brugada Syndrome Type 1 and Long-QT Syndrome Type 3 mutant, E1784K, without affecting peak or persistent INa.

Conclusion: Our hypothesis that LoF in Nav1.5 may be therapeutically treated was supported by the discovery of ARs, which appear to preferentially block the fenestrations. ARs with aromatic functional groups as opposed to aliphatic groups efficaciously maintained Nav1.5 availability. We predict that these bulkier side groups may have a higher affinity for the hydrophobic milieu of the fenestrations, remaining there rather than in the central pore of the channel. Future refinements of AR compound structures and additional validation by molecular dynamic simulations and screening against more Brugada variants will further support their potential benefits in treating certain LoF cardiac arrhythmias.

Bepridil monotherapy failed to prevent coronary vasospasm in a Brugada syndrome patient

Coronary vasospasm sometimes coexists with Brugada syndrome (BrS) and is reportedly associated with poor prognosis. Although calcium channel blockers are considered first-line drugs to prevent coronary vasospasm, they also have the potential to induce ST elevation and ventricular fibrillation (VF) in BrS. Therefore, the optimal medication for such a complicated case is still underdetermined. We report a male patient who presented with VF due to BrS, which was later found to have coexisted with coronary vasospasm. He was treated with low-dose bepridil expecting both its anti-arrhythmic and vasodilatory effects, but a later acetylcholine provocation test showed no suppression of vasospasm. Based on these results, we decided to add nitrates to the medication. This case report illustrates that drug selection needs caution in BrS when complicated with vasospastic angina and that bepridil monotherapy may not be sufficient to suppress coronary vasospasm in such cases.

Personalized approach in arrhythmology by genetic-based data: a case report

The results of molecular genetic testing may affect recommended treatment or therapeutic decisions and risk assessment, may help with identification of family members at risk. Here, we report a case of a young patient with a paradoxical combination of two inherited arrhythmic syndromes and demonstrate the role of genetic testing as one of the basis of personalized approach in diagnosis, treatment and prevention complications of inherited channelopathies complications. Integration of genetic testing results into clinical practice is a successful example of the concept of personalized medicine.

Modeling genetic cardiac channelopathies using induced pluripotent stem cells - Status quo from an electrophysiological perspective

Long QT syndrome (LQTS), Brugada syndrome (BrS), and catecholaminergic polymorphic ventricular tachycardia (CPVT) are genetic diseases of the heart caused by mutations in specific cardiac ion channels and are characterized by paroxysmal arrhythmias, which can deteriorate into ventricular fibrillation. In LQTS3 and BrS different mutations in the SCN5A gene lead to a gain-or a loss-of-function of the voltage-gated sodium channel Nav1.5, respectively. Although sharing the same gene mutation, these syndromes are characterized by different clinical manifestations and functional perturbations and in some cases even present an overlapping clinical phenotype. Several studies have shown that Na⁺ current abnormalities in LQTS3 and BrS can also cause Ca²⁺-signaling aberrancies in cardiomyocytes (CMs). Abnormal Ca²⁺ homeostasis is also the main feature of CPVT which is mostly caused by heterozygous mutations in the RyR2 gene. Large numbers of disease-causing mutations were identified in RyR2 and SCN5A but it is not clear how different variants in the SCN5A gene produce different clinical syndromes and if in CPVT Ca²⁺ abnormalities and drug sensitivities vary depending on the mutation site in the RyR2. These questions can now be addressed by using patient-specific in vitro models of these diseases based on induced pluripotent stem cells (iPSCs). In this review, we summarize different insights gained from these models with a focus on electrophysiological perturbations caused by different ion channel mutations and discuss how will this knowledge help develop better stratification and more efficient personalized therapies for these patients.

Brugada Syndrome Updated Risk Assessment and Perioperative Management in Oral Surgery: A Case Series

Brugada syndrome (BrS) carries the risk of major dysrhythmias increased further by exposure to pro-dysrhythmic factors related to oral surgical procedures such as local anesthetics, anxiety, and postoperative pain. Such risk can be handled by updated multidisciplinary management. In 2020, 3 male BrS patients needed oral surgical treatments at the Complex Unit of Odontostomatology of Aldo Moro University of Bari, Italy. Multidisciplinary individual risk assessment involved cardiologic hazard ratio stratification, event-free survival stratification, and 5-year average risk of ventricular dysrhythmias and sudden cardiac death for Brugada patients; American Society of Anesthesiologists physical status risk class; expected complexity and duration of the procedure; and anxiety score measured by the Modified Dental Anxiety Scale. The authors administered conscious sedation by intravenous diazepam to both a patient susceptible to vasovagal syncope needing tooth extraction with concomitant cystectomy (longer-lasting procedure) and to another who needed routine tooth extraction (brief procedure) but had a moderate dental anxiety score; the last 1 received local anesthesia alone due to his low anxiety, low susceptibility to vasovagal syncope, and need for routine tooth extraction. After positioning external biphasic defibrillator pads, 12-leads continuous electrocardiogram, and peripheral venous access, extractions were performed with local anesthesia by lidocaine 2% with epinephrine 1:100,000; acetaminophen was suggested for postoperative analgesia. No electrocardiographic changes occurred in the perioperative period. The current multidisciplinary individual risk assessment allowed us to detect each BrS patient's risk factors for major dysrhythmias and to adapt oral surgical and anesthesiologic protocols for safe targeted treatment.

Process of Care and a Practical Toolkit for Evaluating and Managing Arrhythmic Risk in the Cardiogenetic Pregnant Patient

Patients with inherited arrhythmia syndromes (IASs) and inherited cardiomyopathies (ICs) are periodically encountered in both general and specialist practices. These syndromes include long QT syndrome, catecholaminergic polymorphic ventricular tachycardia, Brugada syndrome, early repolarisation syndrome, and hypertrophic and arrhythmogenic cardiomyopathies. In general, the presence of an IAS or IC is not a contraindication to pregnancy, but does require additional expertise and patient engagement. In this review, we summarise the various pregnancy-related considerations in patients with IAS and IC, including the impact of physiologic/hemodynamic changes on heart failure progression or arrhythmia propensity, maternal and fetal pregnancy risk stratification, prenatal genetic testing, and the specialised care and monitoring required through pregnancy, labour, and delivery and into the postpartum period. Management of patients with IASs and IC during pregnancy and the postpartum period requires collaboration between patient and provider, with a shared understanding of the general safety and potential risks during the pregnancy and postpartum periods. Patients should be aware of the safety of various medications throughout pregnancy, and those with implantable cardioverter-defibrillators should be managed according to device guidelines. A peripartum care and delivery plan should be established, with multidisciplinary input from various specialists including obstetrics, cardiac obstetrics, and inherited arrhythmia specialists wherever appropriate.

Expert consensus on acute management of ventricular arrhythmias - VT network Austria

The Arrhythmia Working Group of the Austrian Society of Cardiology (ÖKG) has set the goal of systematically structuring and organizing the acute care of patients with ventricular arrhythmias (VA), i.e. ventricular tachycardia (VT) or ventricular fibrillation (VF) in Austria. Within a consensus paper, national recommendations on the basic diagnostic work-up of VA (12-lead ECG, medical history, family history, laboratory analyses, echocardiography, search for reversible causes, ICD interrogation), as well as further medical treatment and therapeutic measures (indication of coronary angiography, ablation therapy) are established. Since acute ablation of VT is indicated in the current ESC guidelines as a class IB indication for scar-associated incessant VT or electrical storm (ES; ≥ 3 ICD therapies in 24 h) as well as for ischemic cardiomyopathy (iCMP) with recurrent ICD shocks, organizational measures must be taken to ensure that these guidelines can be implemented. Therefore, a VT network will be established covering all areas in Austria, consisting of primary and secondary VT centers. Organizational aspects of an acute VT network are defined and should subsequently be implemented by the participating hospitals. All electrophysiologic centers in Austria that deal with VT ablation are to be integrated into the network in the medium-term. Centers that co-operate in the network are divided into primary and secondary VT centers according to predefined criteria.

Brugada syndrome and reduced right ventricular outflow tract conduction reserve: a final common pathway?

Brugada syndrome (BrS) was first described as a primary electrical disorder predisposing to the risk of sudden cardiac death and characterized by right precordial lead ST elevation. Early description of right ventricular structural abnormalities and of right ventricular outflow tract (RVOT) conduction delay in BrS patients set the stage for the current controversy over the pathophysiology underlying the syndrome: channelopathy or cardiomyopathy; repolarization or depolarization. This review examines the current understanding of the BrS substrate, its genetic and non-genetic basis, theories of pathophysiology, and the clinical implications thereof. We propose that the final common pathway for BrS could be viewed as a disease of 'reduced RVOT conduction reserve'.

Sudden Cardiac Death in Brugada Syndrome

The Brugada syndrome is an inherited channelopathy that alters the main transmembrane ion currents that constitute the cardiac action potential. These changes not only modify the resting electrocardiogram but also predispose patients to develop malignant ventricular tachyarrhythmias that can lead to syncope, cardiac arrest, and sudden cardiac death. This syndrome is responsible for nearly 20% of all sudden cardiac deaths in patients with structurally normal hearts and up to 12% of all sudden cardiac deaths. Brugada syndrome is diagnosed by its characteristic electrocardiogram consisting of a coved-type ST-segment elevation of at least 2 mm followed by a negative T wave in either one of the right precordial leads. These changes can be observed spontaneously or after administration of a sodium channel blocker. While our understanding of this disease has increased tremendously since its first description in 1992, the primary therapeutic option remains implantation of an implantable cardioverter-defibrillator to avoid sudden cardiac death. Therefore, tremendous effort is being made to effectively risk stratify patients to determine who would benefit from implantable cardioverter-defibrillator implantation.

Brugada Syndrome: Clinical Features, Risk Stratification, and Management

In 1992, the Brugada brothers published a patient series of aborted sudden death, who were successfully resuscitated from ventricular fibrillation (VF). These patients had a characteristic coved ST-segment elevation in the right precordial leads on their 12-lead electrocardiogram with no apparent structural heart abnormality. This disease was referred to as “right bundle branch block, persistent ST-segment elevation, and sudden death syndrome.” The term Brugada syndrome (BrS) was first coined for this new arrhythmogenic entity in 1996. BrS is more prevalent in Southeast Asian ethnic groups and was considered a familial disease due to the presence of syncope and/or sudden deaths in several members of the same family, however, the genetic alteration was only noted in 1998. The genetic characterization of BrS has proven to be challenging. The most common and well-established BrS genotype involves loss-of-function mutations in the SCN5A gene, but only represents between 15% and 30% of the diagnosed patients. Patients with BrS can present with a range of symptoms which can include syncope, seizures, and nocturnal agonal breathing due to polymorphic ventricular tachycardia or VF. If these arrhythmias are sustained, sudden cardiac death may result. Despite the significant progress on the understanding of BrS over the last two decades, there remain a number of uncertainties and challenges; we present an update review on the subject.

Brugada Syndrome: Presentation and Management of the Atypical Patient in the Emergent Setting

Introduction

Brugada syndrome is a genetic disorder of the heart’s electrical system that increases a patient’s risk of sudden cardiac death. It is a syndrome most prevalent in Southeast Asians and is found 36 times more commonly in Asians than in Hispanics.

Case Report

We report and discuss a case of a 68-year-old Hispanic male who presented with clinical and electrocardiogram abnormalities consistent with Brugada syndrome.

Discussion

The patient’s age and ethnicity represents an atypical presentation of this rare syndrome and the lack of reported studies in the literature pertaining to these demographics reflect this.

Conclusion

Further studies and characterizations are necessary as manifestations continue to be unearthed. As such, Brugada Syndrome should be considered in the differential diagnosis for a myriad of patient populations.

Refractoriness to subcutaneous implantable cardioverter defibrillator after frequent therapies for ventricular fibrillation storms in a Brugada syndrome case

Background

The subcutaneous implantable cardioverter defibrillator (S-ICD) is an alternative to the transvenous implantable cardioverter defibrillator for the prevention of sudden cardiac death. Here, we report a rare case of refractoriness to an S-ICD after frequent therapies for ventricular fibrillation (VF) storms.

Case presentation

A 24-year-old man underwent a bout of syncope with vomiting and incontinence at home. He was brought to the emergency room and was witnessed to spontaneously go into VF successfully converted by external defibrillation. Previously, he was diagnosed with a type I Brugada electrocardiogram pattern by a pilsicainide administration test in another hospital. Although he had a family history of sudden cardiac death in 3 relatives, including his brother, he was followed closely without any therapies because he had never had an episode of syncope. He was implanted with an S-ICD without any trouble. Seven months later, frequent S-ICD shocks for VF storms occurred. His VF was controlled by using intravenous amiodarone, which was converted to an oral preparation. However, his VF recurred after another 2 months. The analysis of his S-ICD data revealed that 4 consecutive shock deliveries could not terminate his VF and the final shock delivered could fortunately terminate it because of a high defibrillation threshold test (DFT) due to an increasing shock impedance (64 to 90 Ω). First, we performed an epicardial Brugada syndrome ablation and subsequently replaced and repositioned the S-ICD lead from a left to a right parasternal site. After the re-implantation of the S-ICD, the DFT test improved to within normal range. According to the pathological analysis, infiltration of inflammatory cells and extensive fibrosis were confirmed in the subcutaneous tissue around the shock lead and S-ICD body.

Conclusion

Frequent S-ICD shocks for VF storms might cause various pathological changes around the device and lead to a high DFT.

Current Controversies and Challenges in Brugada Syndrome

More than three decades since its initial description in 1993, Brugada syndrome remains engulfed in controversy. This review aims to shed light on the main challenges surrounding the diagnostic pathway and criteria, risk stratification of asymptomatic patients, pharmacological and interventional risk modification strategies as well as our current pathophysiological understanding of the disease.

Catheter ablation for monomorphic ventricular tachycardia in Brugada syndrome patients: detailed characteristics and long-term follow-up

PURPOSE

Brugada syndrome (BrS) is a risk of sudden cardiac death due to polymorphic ventricular tachycardia and ventricular fibrillation with unusual monomorphic ventricular tachycardia (MVT). Detailed characteristics of MVT and long-term outcome of catheter ablation are still unknown. This study is aimed to identify the detailed characteristics and long-term follow-up of catheter ablation in BrS patients.

METHODS

We evaluated 188 patients who were diagnosed with BrS from March 1999 to March 2018. Of those, patients who developed MVT and underwent catheter ablation were included. We identified eight MVTs in seven BrS patients.

RESULTS

Three of them already had implantable cardioverter-defibrillator, and MVTs were terminated by cardioversion or anti-tachycardia pacing. Four patients presented with MVT originating from the right ventricular outflow tract, one patient had MVT arising from the LV septum, one patient had MVT arising from the tricuspid annulus, and one patient had bundle branch reentry ventricular tachycardia. All MVTs were successfully treated by catheter ablation in the acute phase, and seven of eight (87.5%) were free from ventricular tachyarrhythmia during the long-term follow-up (median, 7.2 years).

CONCLUSIONS

All MVT cases were successfully treated by catheter ablation. We observed high ventricular arrhythmia free rate following catheter ablation during the long-term follow-up period. BrS patients who developed MVT should consider catheter ablation.

Clinical approach to the patient with Brugada Syndrome: risk stratification and optimal management

The Brugada Syndrome (BrS) is an inherited cardiac ion channel disorder associated with increased risk of ventricular arrhythmias and mortality. Diagnosis is based on a characteristic electrocardiographic (ECG) pattern of coved type ST-segment elevation >2 mm followed by a negative T-wave in ≥1 of the right precordial leads V1 to V3. Since the first description of BrS, the definition of disease and underlying pathophysiological mechanisms have been significantly improved in recent years. Also, significant progress has been made in the field of genetic testing in these patients. Still, there are several open questions regarding the management and outcome of these patients. There is more information about patients who would need an implantable cardiac defibrillator for the primary prevention of sudden cardiac death (that is, those with spontaneous Type I Brugada ECG pattern and arrhythmia-related syncope), but currently published data concerning asymptomatic patients with Brugada ECG pattern and other less-well defined presentations are conflicting. Whereas the role of cardiac defibrillator in patients with Brugada Syndrome is clear, optimal use of catheter ablation and antiarrhythmic drug therapy needs to be further investigated. In this review, we summarize current evidence and contemporary management of patients with BrS.

Insights for Stratification of Risk in Brugada Syndrome

Brugada syndrome (BrS) is an inherited disease with an increased risk of sudden cardiac death (SCD). However, testing identifies genetic disorders in only 20-30% of patients analysed, indicating a gap in knowledge of its genetic aetiology. Diagnosis relies on ECG, and risk stratification in BrS patients is challenging, primarily because of the complexity of the issue. As a result, clinicians fail to provide the appropriate strategy for SCD prevention for many patients. Several variables and interventions are being studied to improve diagnostics and maximise patient protection. In addition, the scientific community must increase efforts to provide patient care according to knowledge and research for improving stratification of risk. In this article, the authors summarise contemporary evidence on clinical variables and provide an overview of future directions in risk stratification and SCD prevention.

Comparative study of carvedilol and quinidine for inhibiting hKv4.3 channel stably expressed in HEK 293 cells

The inhibition of transient outward potassium current (I_to) is the major ionic mechanism for quinidine to treat Brugada syndrome; however, quinidine is inaccessible in many countries. The present study compared the inhibitory effect of the nonselective β-adrenergic blocker carvedilol with quinidine on human Kv4.3 (hKv4.3, encoding for I_to) channel and action potential notch using a whole-cell patch technique in HEK 293 cell line expressing KCND3 as well as in ventricular epicardial myocytes of rabbit hearts. It was found that carvedilol and quinidine inhibited hKv4.3 current in a concentration-dependent manner. The IC₅₀ of carvedilol was 1.2 μM for inhibiting hKv4.3 charge area, while the IC₅₀ of quinidine was 2.9 μM (0.2 Hz). Both carvedilol and quinidine showed typical open channel blocking properties (i.e. decreasing the time to peak of activation and increasing the inactivation of hKv4.3), negatively shifted the V_1/2 of activation and inactivation, and slowed the recovery from inactivation of the channel. Although carvedilol had weaker in use- and rate-dependent inhibition of hKv4.3 peak current than quinidine, its reduction of the charge area was more than quinidine at all frequencies (0.2-3.3 Hz). Moreover, the inhibitory effect of carvedilol on action potential notch was greater than quinidine. These results provide the novel information that carvedilol, like quinidine, significantly inhibits hKv4.3 and action potential notch, suggesting that carvedilol is likely an alternative drug for preventing malignant ventricular arrhythmias in patients with Brugada syndrome in countries where quinidine is unavailable.