Asymptomatic Patients With Brugada ECG Pattern: Long-Term Prognosis From a Large Prospective Study

Implantable Cardioverter-Defibrillator Therapy in Brugada Syndrome: A 30-Year Single-Center Experience

BACKGROUND

Brugada syndrome (BrS) continues to pose clinical challenges, despite 3 decades of dedicated research and therapeutic advancements. The pivotal role of implantable cardioverter-defibrillator (ICD) therapy in safeguarding high-risk BrS patients from sudden cardiac death due to ventricular arrhythmias is undeniable. However, the debate on risk stratification and the use of ICDs for primary prevention remains ongoing.

OBJECTIVES

This study aimed to evaluate the clinical features, management, and long-term outcomes of ICD therapy in patients with Brugada syndrome.

METHODS

BrS-diagnosed patients were prospectively enrolled. Inclusion criteria were: 1) a Brugada type 1 electrocardiogram pattern, either spontaneous or drug induced; 2) ICD implantation; and 3) consistent follow-up. Risk stratification was based on prior arrhythmic events, and the multiparametric Brussel risk score was used from 2017. High-risk patients underwent video-thoracoscopic epicardial ablation starting in 2016. ICD implantation strategies evolved over time, guided by patients' clinical and demographic characteristics.

RESULTS

A total of 306 consecutive Brugada patients (186 male [61%]; mean age 41 ± 17 years; range: 1-82 years) received ICDs at our institution from 1992 to 2022. ICDs were implanted for secondary prevention in 16% of patients. Over the 3 decades, the proportions of secondary prevention implants and asymptomatic patients remained stable, while risk factors fluctuated in the first two decades before stabilizing. During long-term follow-up (median 103 months [63-147 months]), 14% of patients experienced at least 1 sustained ventricular arrhythmia (VA) (1.59 per 100 person-years), 15% had at least 1 inappropriate ICD shock-unaffected by the presence of single or dual leads-and 27% required device revision and/or lead replacement. Patients with secondary prevention ICDs had a higher incidence of both ventricular and supraventricular arrhythmias compared to those with primary prevention ICDs. Loss-of-function mutations and prior nonsustained VAs were associated with sustained VAs. Among high-risk patients, those who underwent epicardial ablation experienced significantly fewer ventricular events. The overall mortality rate was 5.88%, with 22.2% of deaths attributed to cardiac causes.

CONCLUSIONS

This 30-year study highlights ICD therapy's critical role in preventing fatal arrhythmias in Brugada syndrome, but also reveals frequent device-related complications, especially in younger patients. Thoracoscopic epicardial ablation significantly reduced VA in high-risk patients, offering a promising adjunctive therapy. These findings emphasize the need for individualized treatment strategies to balance the benefits of ICDs with their risks, and underscore the potential of ablation to improve long-term outcomes.

Paroxysmal, Persistent, and Permanent Type-1 Brugada Pattern: Does Burden Matter?

Spontaneous type-1 Brugada patterns are associated with an elevated risk of major arrhythmic events, yet the relationship between varying degrees of pattern burden and the occurrence of a first major arrhythmic event remains unclear. This retrospective cohort study included 64 adult patients with a spontaneous type-1 Brugada pattern, who were identified at Mayo Clinic sites and followed for ≥12 months after the initial diagnosis. All patients underwent at least three 12-lead electrocardiograms (ECGs) within the first year. Individuals with prior major arrhythmic events were excluded. The percentage of ECGs showing a type-1 pattern was calculated and categorized as paroxysmal (<50%), persistent (50-99%), or permanent (100%). During a median follow-up of 92 months, seven patients (11%) experienced their first major arrhythmic event. Of these, one had paroxysmal, four had persistent, and two had permanent spontaneous type-1 Brugada patterns. Although statistical significance was not reached, the hazard ratios suggested a trend toward increased risk with persistent and permanent patterns compared to paroxysmal patterns. No sudden cardiac deaths occurred during follow-up. These findings suggest that a higher burden of spontaneous type-1 Brugada patterns may be associated with increased arrhythmic risk.

SCN5A variant type-dependent risk prediction in Brugada syndrome

AIMS

The variant in SCN5A with the loss of function (LOF) effect in the cardiac Na+ channel (Nav1.5) is the definitive cause for Brugada syndrome (BrS), and the functional analysis data revealed that LOF variants are associated with poor prognosis. However, which variant types (e.g. missense or non-missense) affect the prognoses of those variant carriers remain unelucidated.

METHODS AND RESULTS

We defined SCN5A LOF variants as all non-missense and missense variants that produce peak INa < 65% of wild-type previously confirmed by patch-clamp studies. The study population consisted of 76 Japanese BrS patients (74% patients were male and the median age [IQR] at diagnosis was 28 [14-45] years) with LOF type of SCN5A variants: 40 with missense and 36 with non-missense variants. Non-missense variant carriers presented significantly more severe cardiac conduction disorder compared to the missense variant carriers. During follow-up periods of 9.0 [5.0-14.0] years, compared to missense variants, non-missense variants were significant risk factors of lifetime lethal arrhythmia events (LAEs) (P = 0.023). When focusing only on the missense variants that produce no peak INa, these missense variant carriers exhibited the same clinical outcomes as those with non-missense (log-rank P = 0.325). After diagnosis, however, both variant types were comparable in risk of LAEs (P = 0.155).

CONCLUSION

We identified, for the first time, that SCN5A non-missense variants were associated with higher probability of LAE than missense variants in BrS patients though it did not change significantly after diagnosis.

Which Brugada patient deserves continuous ECG monitoring through implantable loop recorder? An evidence update

Brugada syndrome (BrS) is a genetic condition that increases the risk of life-threatening arrhythmias, which can result in sudden cardiac death (SCD). Implantable loop recorders (ILRs) have become a key tool in managing patients with unexplained syncope, and guidelines advise their use in individuals with recurrent, unexplained syncope or palpitations. However, the role of ILRs in inherited arrhythmic conditions like BrS remains a topic of debate. Most patients newly diagnosed with BrS show no symptoms, but around 30% may experience symptoms such as syncope or palpitations, which can arise from arrhythmic issues or other causes like neurally mediated reflexes. Accurately assessing the cause of these symptoms is crucial to evaluate the risk of SCD. This document aims to examine current evidence on the role of ILR implantation in patients with BrS. The most frequent arrhythmias recorded by ILR are supraventricular arrhythmias and conduction disorders; ventricular arrhythmias, usually nonsustained, are rarely recorded. Symptoms-to-rhythm correlation by ILR can have therapeutic implications in case of recorded arrhythmias (initiation of drug therapy, ablation procedures or defibrillator/pace-maker implantation), provide reassurance in patients without rhythm disorders documented and improve their quality of life. However, given the low rate of detected arrhythmias, the clinical value of ILR in asymptomatic patients needs further evaluation.

Quinidine for ventricular arrhythmias: A comprehensive review

Quinidine, the first antiarrhythmic drug, was widely used during the 20th century. Multiple studies have been conducted to provide insights into the pharmacokinetics and pleiotropic effects of Class Ia antiarrhythmic drugs. However, safety concerns and the emergence of new drugs led to a decline in their use during the 1990s. Despite this, recent studies have reignited the interest in quinidine, particularly for ventricular arrhythmias, where other antiarrhythmics have failed. In conditions such as Brugada syndrome, idiopathic ventricular fibrillation, early repolarization syndrome, short QT syndrome, and electrical storms, quinidine remains a valuable asset. Starting from the European and American recommendations, this comprehensive review aimed to explore the various indications for quinidine and the studies that support its use. We also discuss the potential future of quinidine, including the necessary research to optimize its use and patient selection. Additionally, it addresses the imperative task of mitigating the iatrogenic burden associated with quinidine usage and confronts the challenge of ensuring drug accessibility.

Spontaneous type 1 ECG and arrhythmic risk in Brugada syndrome: A meta-analysis of adjusted time-to-event data

Background

Brugada syndrome (BrS) is associated with an increased risk of major arrhythmic events (MAEs), particularly in patients with a spontaneous type 1 electrocardiographic (ECG) pattern.

Objective

Because previous meta-analyses used mainly crude or unadjusted data from observational studies, we conducted an updated meta-analysis on the prognostic role of spontaneous type 1 ECG in BrS patients combining adjusted and unadjusted data separately.

Methods

We conducted a systematic search of PubMed and Cochrane Central Register of Controlled Trials from inception to May 2024. Studies providing hazard ratios for MAEs associated with spontaneous type 1 ECG in BrS patients were included.

Results

Eighteen studies comprising 7238 patients were included, with 10 providing adjusted and 17 providing unadjusted data. Separate pooled analyses using a random-effects model demonstrated a significantly increased risk of MAEs in BrS patients with spontaneous type 1 ECG compared with those without, with a pooled adjusted hazard ratio (aHR) of 2.05 (95% CI 1.38-3.03) and an unadjusted hazard ratio of 2.97 (95% CI 2.04-4.34). Subgroup analysis revealed higher risks in studies with non-Asian populations and those including patients with no history of aborted cardiac arrest (aHR 2.36, 95% CI 1.35-4.11; and aHR 3.56, 95% CI 2.35-5.41, respectively) and a persistent significant risk in studies accounting for syncope as a covariate (aHR 2.01, 95% CI 1.24-3.27).

Conclusion

Our analysis indicates that patients with BrS and spontaneous type 1 ECG are at higher risk of MAEs. This is consistent across various subgroups, including asymptomatic individuals.

A Vision Transformer Model for the Prediction of Fatal Arrhythmic Events in Patients with Brugada Syndrome

Brugada syndrome (BrS) is an inherited electrical cardiac disorder that is associated with a higher risk of ventricular fibrillation (VF) and sudden cardiac death (SCD) in patients without structural heart disease. The diagnosis is based on the documentation of the typical pattern in the electrocardiogram (ECG) characterized by a J-point elevation of ≥2 mm, coved-type ST-segment elevation, and negative T wave in one or more right precordial leads, called type 1 Brugada ECG. Risk stratification is particularly difficult in asymptomatic cases. Patients who have experienced documented VF are generally recommended to receive an implantable cardioverter defibrillator to lower the likelihood of sudden death due to recurrent episodes. However, for asymptomatic individuals, the most appropriate course of action remains uncertain. Accurate risk prediction is critical to avoiding premature deaths and unnecessary treatments. Due to the challenges associated with experimental research on human cardiac tissue, alternative techniques such as computational modeling and deep learning-based artificial intelligence (AI) are becoming increasingly important. This study introduces a vision transformer (ViT) model that leverages 12-lead ECG images to predict potentially fatal arrhythmic events in BrS patients. This dataset includes a total of 278 ECGs, belonging to 210 patients which have been diagnosed with Brugada syndrome, and it is split into two classes: event and no event. The event class contains 94 ECGs of patients with documented ventricular tachycardia, ventricular fibrillation, or sudden cardiac death, while the no event class is composed of 184 ECGs used as the control group. At first, the ViT is trained on a balanced dataset, achieving satisfactory results (89% accuracy, 94% specificity, 84% sensitivity, and 89% F1-score). Then, the discarded no event ECGs are attached to additional 30 event ECGs, extracted by a 24 h recording of a singular individual, composing a new test set. Finally, the use of an optimized classification threshold improves the predictions on an unbalanced set of data (74% accuracy, 95% negative predictive value, and 90% sensitivity), suggesting that the ECG signal can reveal key information for the risk stratification of patients with Brugada syndrome.

Automatized quantitative electrocardiography from digitized paper electrocardiograms: A new avenue for risk stratification in patients with Brugada syndrome

BACKGROUND

Arrhythmic risk stratification is a major challenge in Brugada syndrome. Studies have evaluated risk stratification based on manually measured electrocardiogram (ECG) parameters at baseline and/or after drug challenge.

AIM

To assess the predictive value of multiple ECG parameters measured automatically from digitized paper ECGs.

METHODS

During a prospective, multicentre cohort study that included patients with Brugada syndrome with type 1 ECG (spontaneously or drug-induced), paper ECGs were digitized and analysed. Major events were sudden cardiac death, aborted cardiac arrest and appropriate implantable cardioverter-defibrillator (ICD) therapy in the ventricular fibrillation (VF) zone. The predictive value of clinical and ECG parameters was assessed using univariable and multivariable Cox models.

RESULTS

ECGs from 301 patients (74% male, mean age 43.1±13.3years, mean follow-up 7.1±5.6years) were analysed. Major events occurred in 6% of patients before diagnosis and 8% during follow-up. Two baseline ECG parameters were independently associated with major events: QRS prolongation in lead V1>113ms (hazard ratio [HR] 3.49, 95% confidence interval [CI] 1.72-7.09; P<0.001) and S duration on DI>33.5ms (HR 3.56, 95% CI 1.52-8.31; P<0.01). In drug-induced patients, changes in the Tpeak-Tend interval on V2 were associated with major events (HR 4.69, 95% CI 1.21-18.17; P=0.014).

CONCLUSION

Paper ECG datasets could be used for automatic quantitative ECG measurements. We confirmed the association of previously described parameters with events and identified useful new parameters. Multi-parametric ECG quantification may be used to assess risk in patients with Brugada syndrome.

Nonmodifiable Risk Factors Predict Outcomes in Brugada Syndrome

BACKGROUND

Risk stratification in Brugada syndrome (BrS) is based on the occurrence of dynamic factors, such as unexplained syncope and documentation of spontaneous type 1 pattern. At odds with other channelopathies, the role of nonmodifiable risk factors such as sex or genetics remains uncertain.

OBJECTIVES

This study aims to identify nonmodifiable risk factors for the occurrence of life-threatening arrhythmic events (LAEs) and define their clinical utility.

METHODS

Clinical and genetic data from consecutive, unrelated Italian patients with Brugada syndrome screened on the sodium voltage-gated channel alpha subunit 5 (SCN5A) gene and 3 pivotal single-nucleotide variations (formerly single-nucleotide polymorphisms) associated with BrS (rs11708996, rs10428132, and rs9388451) were analyzed using multivariable Cox proportional hazards model.

RESULTS

In 2,182 unrelated patients with BrS (81% males; median age at diagnosis: 41.6 years [Q1-Q3: 33.4-50.3 years]), male sex (HR: 3.6; 95% CI: 1.9-6.9; P = 0.0001), missense SCN5A mutations in BrS-enriched domains (HR: 2.3; 95% CI: 1.2-4.3; P = 0.008), nonmissense SCN5A mutations (HR: 3.2; 95% CI: 1.8-5.7; P < 0.001), and polygenic risk score for BrS (HR: 1.3; 95% CI: 1.0-1.6; P = 0.041) were all independently associated with a significantly higher risk of a first LAE since birth. Based on these results, we derived the nonmodifiable risk of each patient with BrS, and the division of nonmodifiable risk into tertiles identified 3 distinct risk profiles. In an analysis at follow-up, nonmodifiable risk was independently associated with LAE at follow-up (HR: 1.8; 95% CI: 1.1-2.7; P = 0.014), alongside classical predictors including: history of LAE before diagnosis (HR: 13.8; 95% CI: 8.1-23.7; P < 0.0001), history of unexplained syncope before diagnosis (HR: 4.1; 95% CI: 2.4-6.8; P < 0.0001), and spontaneous type 1 pattern at diagnosis (HR: 2.1; 95% CI: 1.2-3.8; P = 0.010). The model was internally validated, and we derived the equation permitting to calculate the granular 5-year risk of experiencing an LAE at follow-up for each patient with BrS, which may be used to facilitate clinical decision-making.

CONCLUSIONS

Our data show that male sex, type of SCN5A mutation, and polygenic risk score for BrS define the nonmodifiable risk of each patient with BrS. Nonmodifiable risk is independently associated with LAE, regardless of symptoms or pattern type.

Advancing the access to cardiovascular diagnosis and treatment among women with cardiovascular disease: a joint British Cardiovascular Societies' consensus document

Despite significant progress in cardiovascular pharmacotherapy and interventional strategies, cardiovascular disease (CVD), in particular ischaemic heart disease, remains the leading cause of morbidity and mortality among women in the UK and worldwide. Women are underdiagnosed, undertreated and under-represented in clinical trials directed at management strategies for CVD, making their results less applicable to this subset. Women have additional sex-specific risk factors that put them at higher risk of future cardiovascular events. Psychosocial risk factors, socioeconomic deprivation and environmental factors have an augmented impact on women's cardiovascular health, highlighting the need for a holistic approach to care that considers risk factors specifically related to female biology alongside the traditional risk factors. Importantly, in the UK, even in the context of a National Health Service, there exist significant regional variations in age-standardised mortality rates among patients with CVD. Given most CVDs are preventable, concerted efforts are necessary to address the unmet needs and ensure parity of care for women with CVD. The present consensus document, put together by the British Cardiovascular Society (BCS)'s affiliated societies, specifically portrays the current status on the sex-related differences in the diagnosis and treatment of each of the major CVD areas and proposes strategies to overcome the barriers in accessing diagnoses and treatments among women. This document aims at raising awareness of the scale of the current problem and hopes to stimulate a multifaceted approach to address sex disparities and enable future comprehensive sex- and gender-based research through collaboration across different affiliated societies within the BCS.

Prevalence and associated factors of ECG abnormality patterns indicative of cardiac channelopathies among adult general population of Tehran, Iran: a report from the Tehran Cohort Study (TeCS)

BACKGROUND

The characteristics of electrocardiogram (ECG) abnormalities related to cardiac channelopathies potentially linked to sudden cardiac death (SCD) are not widely recognized in Iran. We examined the prevalence of such ECG patterns and their related factors among adult residents of Tehran, Iran.

METHODS

The clinical characteristics and 12-lead ECGs of Tehran Cohort Study participants were examined. Long QT intervals, short QT intervals, Brugada syndrome (BrS) patterns, and early repolarization (ER) were evaluated using computer-based assessment software validated by cardiologists. Logistic regression models were employed to identify the factors associated with the prevalence of different ECG patterns.

RESULTS

Out of 7678 available ECGs, 7350 were included in this analysis. Long QT interval, ER pattern, BrS patterns, and short QT interval were found in 3.08%, 1.43%, 0.31%, and 0.03% of participants, respectively. The prevalence of long QT interval increased with age, opium consumption, and presence of hypertension. Younger age, lower body mass index (BMI), alcohol use and male sex were independently linked to an elevated prevalence of ER pattern. Most individuals with BrS patterns were men (95%) and had lower BMI, high- and low-density lipoprotein, and total cholesterol compared to those without the BrS pattern. At a mean follow-up of 30.2 ± 5.5 months, all-cause mortality in the group exhibiting abnormal ECG patterns (6.3%) was approximately twice as high as that in the group without such patterns (2.96%).

CONCLUSION

Abnormal ECG patterns corresponding to channelopathies were relatively rare among adult residents of the Tehran population, and their prevalence was influenced by various factors.

CLINICAL TRIAL NUMBER

Not applicable.

Validation of novel risk prediction models in patients with Brugada syndrome: A multicenter study in Japan

BACKGROUND

Risk stratification in patients with Brugada syndrome (BrS) is challenging, especially in those at intermediate risk. The Predicting Arrhythmic evenT (PAT) score has recently been demonstrated to be excellent for predicting future arrhythmic events in patients without prior ventricular fibrillation (VF). However, validation studies are lacking.

OBJECTIVE

This study aimed to assess the performance of a novel risk stratification model in predicting future VF events in patients with BrS in a Japanese multicenter cohort.

METHODS

The PAT score was calculated for 413 patients with BrS (mean age, 50.9 ± 13.6 years; 395 men) from 59 hospitals in Japan, including 314 patients without prior VF. The incidence of developing VF during the follow-up period was investigated.

RESULTS

During the 106.8-month follow-up period, 54 patients (13.1%) experienced VF events. Of the 314 patients without prior VF at enrollment, 14 (4.5%) experienced VF events. The incidence of VF events during the follow-up period was significantly higher in patients with PAT scores ≥ 10 than in those with scores < 10 (41/173 [23.7%] vs 13/240 [5.4%]; P < .0001) in the total cohort. No difference was observed in the incidence of VF events between patients with PAT scores ≥ 10 and < 10 among the 314 patients without prior VF (6/86 [7.0%] vs 8/228 [3.5%]; P = .22). PAT scores ≥ 10 predicted future VF events with a sensitivity and specificity of 42.9% and 73.3%, respectively.

CONCLUSION

This Japanese multicenter registry demonstrated that the novel risk stratification model could not accurately predict future VF events in patients with BrS but without prior VF.

Continuous Rhythm Monitoring With Implanted Loop Recorders in Children and Adolescents With Brugada Syndrome

BACKGROUND

Young (<18 years of age) patients with Brugada syndrome (BrS) are often under-represented in BrS studies and their management, especially related to syncopal episodes, remains unclear.

OBJECTIVES

This study sought to describe the arrhythmia prevalence among young patients with BrS undergoing continuous rhythm monitoring by implantable loop recorder (ILR) and to assess the etiology behind syncope of undetermined origin.

METHODS

A total of 147 patients with BrS with ILR were enrolled in 12 international centers and divided into pediatric (age <12 years; n = 77, 52%) and adolescents (age 13-18 years; n = 70, 48%).

RESULTS

Mean age was 11.3 years, 53 patients (36.1%) were female, and 31 (21.1%) had spontaneous type 1 electrocardiograms. Over a median follow-up of 3.6 years (Q1-Q3: 1.6-4.8 years), an arrhythmic event was recorded in 33 patients (22.4%), mainly of nonventricular origin: 15 atrial (10.2%) and 16 bradyarrhythmic events (10.9%). Ventricular arrhythmias occurred in 4 patients, all with spontaneous BrS, and were fever-related in one-half. Among all patients with recurrence of syncope during follow-up, true arrhythmic syncope was documented in 5 (17.8%), and it was due to bradyarrhythmias or atrial arrhythmias in 3 cases (60%).

CONCLUSIONS

Continuous rhythm monitoring with ILRs in young patients with BrS detects a broad range of arrhythmias. Ventricular arrhythmias occur predominantly in patients with spontaneous type 1 electrocardiograms and during fever. Despite the young age, bradyarrhythmias and atrial arrhythmias are frequent and represent the cause of arrhythmic syncope in 60% of patients. Young patients with BrS with syncope of undetermined origin may benefit from ILR implant.

Predicting ventricular arrhythmia inducibility in ajmaline-induced Brugada type I pattern: Validation of the dST-Tiso interval

INTRODUCTION

The dST-Tiso is a newly proposed electrocardiographic (ECG) marker during Brugada (BrS) type I pattern, that predicts the likelihood of ventricular arrhythmia (VA) inducibility in patients with ajmaline-induced pattern. The objective of this study was to validate the effectiveness of this criterion using an independent data set.

METHODS

Consecutive patients exhibiting a BrS type I ECG pattern following ajmaline administration underwent programmed ventricular stimulation (PVS). dST-Tiso interval was measured in all patients and tested as a predictor for positive VA inducibility.

RESULTS

Among 128 patients (median age 43 years, 59% male) with drug-induced BrS type I ECG pattern who underwent PVS, 32 (25.0%) had VA inducibility that required defibrillation. Compared to noninducible subjects, those with positive PVS were more commonly male (81% vs. 51%, p = 0.003), had longer PQ (165 vs. 160 ms, p = 0.016) and dST-Tiso (310 vs. 230 ms, p < 0.001) intervals, and shorter QT interval (412 vs. 420 ms, p = 0.022). When treated as a continuous variable, dST-Tiso confirmed significant association with VA inducibility, with an adjusted odds ratio of 1.02 (95% confidence interval: 1.01-1.03, p < 0.001) for each 1 ms increase in duration. A dST-Tiso interval >300 ms yielded a sensitivity of 75%, a specificity of 86%, and positive and negative predictive values of 69% and 91%, respectively.

CONCLUSION

The validation of the model based on the dST-Tiso interval >300 ms confirmed its high accuracy in predicting VA inducibility in drug-induced BrS type I pattern. This straightforward ECG marker might be linked to the extent of the electrical substrate of the disease.

Zebrafish as a Model System for Brugada Syndrome

Brugada syndrome (BrS) is an inheritable cardiac arrhythmogenic disease, associated with an increased risk of sudden cardiac death. It is most common in males around the age of 40 and the prevalence is higher in Asia than in Europe and the United States. The pathophysiology underlying BrS is not completely understood, but several hypotheses have been proposed. So far, the best effective treatment is the implantation of an implantable cardioverter-defibrillator (ICD), but device-related complications are not uncommon. Therefore, there is an urgent need to improve diagnosis and risk stratification and to find new treatment options. To this end, research should further elucidate the genetic basis and pathophysiological mechanisms of BrS. Several experimental models are being used to gain insight into these aspects. The zebrafish (Danio rerio) is a widely used animal model for the study of cardiac arrhythmias, as its cardiac electrophysiology shows interesting similarities to humans. However, zebrafish have only been used in a limited number of studies on BrS, and the potential role of zebrafish in studying the mechanisms of BrS has not been reviewed. Therefore, the present review aims to evaluate zebrafish as an animal model for BrS. We conclude that zebrafish can be considered as a valuable experimental model for BrS research, not only for gene editing technologies, but also for screening potential BrS drugs.

Diagnosis of Brugada Syndrome With a Sodium-Channel-Blocker Test: Who Should Be Tested? Who Should Not?

Intravenous infusion of sodium-channel blockers (SCB) with either ajmaline, flecainide, procainamide, or pilsicainide to unmask the ECG of Brugada syndrome is the drug challenge most commonly used for diagnostic purposes when investigating cases possibly related to inherited arrhythmia syndromes. For a patient undergoing an SCB challenge, the impact of a positive result goes well beyond its diagnostic implications. It is, therefore, appropriate to question who should undergo a SCB test to diagnose or exclude Brugada syndrome and, perhaps more importantly, who should not. We present a critical review of the benefits and drawbacks of the SCB challenge when performed in cardiac arrest survivors, patients presenting with syncope, family members of probands with confirmed Brugada syndrome, and asymptomatic patients with suspicious ECG.

[Cardiac channelopathies in the context of hereditary arrhythmia syndromes]

Genetic arrhythmia disorders are rare diseases; however, they are a common cause of sudden cardiac death in children, adolescents, and young adults. In principle, a distinction can be made between channelopathies and cardiomyopathies in the context of genetic diseases. This paper focuses on the channelopathies long and short QT syndrome, Brugada syndrome, and catecholaminergic polymorphic ventricular tachycardia (CPVT). Early diagnosis of these diseases is essential, as drug therapy, behavioral measures, and if necessary, implantation of a cardioverter defibrillator can significantly improve the prognosis and quality of life of patients. This paper highlights the pathophysiological and genetic basis of these channelopathies, describes their clinical manifestations, and comments on the principles of diagnosis, risk stratification and therapy.

Electrophysiological patterns and structural substrates of Brugada syndrome: Critical appraisal and computational analyses

Brugada syndrome (BrS) is a cardiac electrophysiological disease with unknown etiology, associated with sudden cardiac death. Symptomatic patients are treated with implanted cardiac defibrillator, but no risk stratification strategy is effective in patients that are at low to medium arrhythmic risk. Cardiac computational modeling is an emerging tool that can be used to verify the hypotheses of pathogenesis and inspire new risk stratification strategies. However, to obtain reliable results computational models must be validated with consistent experimental data. We reviewed the main electrophysiological and structural variables from BrS clinical studies to assess which data could be used to validate a computational approach. Activation delay in the epicardial right ventricular outflow tract is a consistent finding, as well as increased fibrosis and subclinical alterations of right ventricular functional and morphological parameters. The comparison between other electrophysiological variables is hindered by methodological differences between studies, which we commented. We conclude by presenting a recent theory unifying electrophysiological and structural substrate in BrS and illustrate how computational modeling could help translation to risk stratification.

Temperature and ST-segment morphology remote monitoring: new perspectives for implantable cardiac monitors in Brugada syndrome

INTRODUCTION

Patients with Brugada syndrome (BrS) face an increased risk of ventricular arrhythmias and sudden cardiac death. Implantable cardiac monitors (ICMs) have emerged as effective tools for detecting arrhythmias in BrS. Technological advancements, including temperature sensors and improved subcutaneous electrocardiogram (subECG) signal quality, hold promise for further enhancing their utility in this population.

METHODS AND RESULTS

We present a case of a 40-year-old man exhibiting a BrS type 2 pattern on 12-lead ECG, who underwent ICM insertion (BIOMONITOR IIIm, BIOTRONIK) due to drug-induced BrS type 1 pattern and a history of syncope, with a negative response to programmed ventricular stimulation. The device contains an integrated temperature sensor and can transmit daily vital data, such as mean heart rate and physical activity. Several months later, remote alerts indicated a temperature increase, along with transmitted subECGs suggesting a fever-induced BrS type 1 pattern. The patient was promptly advised to commence antipyretic therapy. Over the following days, remotely monitored parameters showed decreases in mean temperature, physical activity, and mean heart rate, without further recurrence of abnormal subECGs.

CONCLUSION

ICMs offer valuable insights beyond arrhythmia detection in BrS. Early detection of fever using embedded temperature sensors may improve patient management, while continuous subECG morphological analysis has the potential to enhance risk stratification in BrS patients.

Identification of a SCN5A Genetic Variant Associated With Type 1 Brugada Syndrome (BrS) in a Family

The Brugada pattern is associated with a genetic disorder characterized by ST-segment elevation in the right precordial leads on electrocardiogram (EKG) in the absence of structural heart disease. Patients with the Brugada pattern have an increased risk for ventricular tachyarrhythmia and sudden cardiac death. Loss-of-function mutations in the SCN5A gene which encodes the alpha subunit of the cardiac sodium channel have been associated with Brugada syndrome (BrS). We report a case of a patient who was found to have a spontaneous type 1 Brugada pattern on a routine EKG done prior to travel. He underwent electrophysiological testing (EPS) which provoked ventricular tachycardia and underwent implantable cardioverter defibrillator (ICD) placement. His family history revealed a history of sudden cardiac death, abnormal EKG, syncope, dilated cardiomyopathy, and BrS. Genetic testing revealed a variant of uncertain significance (VUS) in the SCN5A gene in the proband and six of his relatives. The SCN5A VUS in this clinical context and segregation with the disease in his family supports its reclassification to pathogenic.

The role for ambulatory electrocardiogram monitoring in the diagnosis and prognostication of Brugada syndrome: a sub-study of the Rare Arrhythmia Syndrome Evaluation (RASE) Brugada study

AIMS

Brugada syndrome (BrS) diagnosis and risk stratification rely on the presence of a spontaneous type 1 (spT1) electrocardiogram (ECG) pattern; however, its spontaneous fluctuations may lead to misdiagnosis and risk underestimation. This study aims to assess the role for repeat high precordial lead (HPL) resting and ambulatory ECG monitoring in identifying a spT1, and evaluate its prognostic role.

METHODS AND RESULTS

HPL resting and ambulatory monitoring ECGs of BrS subjects were reviewed retrospectively, and the presence of a spT1 associated with ventricular dysrhythmias and sudden cardiac death (SCD). Three-hundred and fifty-eight subjects (77 with spT1 pattern at presentation, Group 1, and 281 without, Group 2) were included. In total, 1651 resting HPL resting and 621 ambulatory monitoring ECGs were available for review, or adequately described. Over a median follow-up of 72 months (interquartile range - IQR - 75), 42/77 (55%) subjects in Group 1 showed a spT1 in at least one ECG. In Group 2, 36/281 subjects (13%) had a newly detected spT1 (1.9 per 100 person-year) and 23 on an HPL ambulatory recording (8%). Seven previously asymptomatic subjects, five of whom had a spT1 (four at presentation and one at follow-up), experienced arrhythmic events; survival analysis indicated that a spT1, either at presentation or during lifetime, was associated with events. Univariate models showed that a spT1 was consistently associated with increased risk [spT1 at presentation: hazard ratio (HR) 6.3, 95% confidence interval (CI) 1.4-28, P = 0.016; spT1 at follow-up: HR 3.1, 95% CI 1.3-7.2, P = 0.008].

CONCLUSION

Repeated ECG evaluation and HPL ambulatory monitoring are vital in identifying transient spT1 Brugada pattern and its associated risk.

Long-term clinical outcomes of patients with drug-induced type 1 Brugada electrocardiographic pattern: A nationwide cohort registry study

BACKGROUND

There are limited real-world data on the extended prognosis of patients with drug-induced type 1 Brugada electrocardiogram (ECG).

OBJECTIVE

We assessed the clinical outcomes and predictors of life-threatening arrhythmias in patients with drug-induced type 1 Brugada ECG.

METHODS

This multicenter retrospective study, conducted at 21 Italian and Swiss hospitals from July 1997 to May 2021, included consecutive patients with drug-induced type 1 ECG. The primary outcome, a composite of appropriate ICD therapies and sudden cardiac death, was assessed along with the clinical predictors of these events.

RESULTS

A total of 606 patients (mean age 49.7 ± 14.7 years; 423 [69.8%] men) were followed for a median of 60.3 months (interquartile range 23.0-122.4 months). Nineteen patients (3.1%) experienced life-threatening arrhythmias, with a median annual event rate of 0.5% over 5 years and 0.25% over 10 years. The SCN5A mutation was the only predictor of the primary outcome (hazard ratio 4.54; P = .002), whereas a trend was observed for unexplained syncope (hazard ratio 3.85; P = .05). In patients who were asymptomatic at presentation, the median annual rate of life-threatening arrhythmias is 0.24% over 5 years and increases to 1.2% if they have inducible ventricular fibrillation during programmed ventricular stimulation.

CONCLUSION

In patients with drug-induced type 1 Brugada ECG, the annual risk of life-threatening arrhythmias is low, with the SCN5A mutation as the only independent predictor. Unexplained syncope correlated with worse clinical outcomes. Ventricular fibrillation inducibility at programmed ventricular stimulation significantly increases the median annual rate of life-threatening arrhythmias from 0.24% to 1.2% over 5 years.

Sudden Cardiac Death in the Young: State-of-the-Art Review in Molecular Autopsy

Sudden cardiac death (SCD) is defined as unexpected death due to a cardiac cause that occurs rapidly. Despite the identification of prevention strategies, SCD remains a serious public health problem worldwide, accounting for 15-20% of all deaths, and is therefore a challenge for modern medicine, especially when it affects young people. Sudden cardiac death in young people affects the population aged ≤ 35 years, including athletes and non-athletes, and it is due to various hereditary and non-hereditary causes. After an autopsy, if the cause remains unknown, it is called sudden unexplained death, often attributable to genetic causes. In these cases, molecular autopsy-post-mortem genetic testing-is essential to facilitate diagnostic and therapeutic pathways and/or the monitoring of family members of the cases. This review aims to elaborate on cardiac disorders marked by genetic mutations, necessitating the post-mortem genetic investigation of the deceased for an accurate diagnosis in order to facilitate informed genetic counseling and to implement preventive strategies for family members of the cases.

Implantable loop recorders in patients with Brugada syndrome: the BruLoop study

BACKGROUND AND AIMS

Available data on continuous rhythm monitoring by implantable loop recorders (ILRs) in patients with Brugada syndrome (BrS) are scarce. The aim of this multi-centre study was to evaluate the diagnostic yield and clinical implication of a continuous rhythm monitoring strategy by ILRs in a large cohort of BrS patients and to assess the precise arrhythmic cause of syncopal episodes.

METHODS

A total of 370 patients with BrS and ILRs (mean age 43.5 ± 15.9, 33.8% female, 74.1% symptomatic) from 18 international centers were included. Patients were followed with continuous rhythm monitoring for a median follow-up of 3 years.

RESULTS

During follow-up, an arrhythmic event was recorded in 30.7% of symptomatic patients [18.6% atrial arrhythmias (AAs), 10.2% bradyarrhythmias (BAs), and 7.3% ventricular arrhythmias (VAs)]. In patients with recurrent syncope, the aetiology was arrhythmic in 22.4% (59.3% BAs, 25.0% VAs, and 15.6% AAs). The ILR led to drug therapy initiation in 11.4%, ablation procedure in 10.9%, implantation of a pacemaker in 2.5%, and a cardioverter-defibrillator in 8%. At multivariate analysis, the presence of symptoms [hazard ratio (HR) 2.5, P = .001] and age >50 years (HR 1.7, P = .016) were independent predictors of arrhythmic events, while inducibility of ventricular fibrillation at the electrophysiological study (HR 9.0, P < .001) was a predictor of VAs.

CONCLUSIONS

ILR detects arrhythmic events in nearly 30% of symptomatic BrS patients, leading to appropriate therapy in 70% of them. The most commonly detected arrhythmias are AAs and BAs, while VAs are detected only in 7% of cases. Symptom status can be used to guide ILR implantation.

Brugada syndrome: identification of subjects at risk and therapy

Brugada syndrome mainly affects young subjects with structurally normal heart and can cause x syncope or sudden death due to ventricular arrhythmias, even as the first manifestation, in approximately 5-10% of cases. To date, two questions remain open: how to recognize subjects who will experience arrhythmic events and how to treat them. The guidelines suggest treating subjects with a previous history of cardiac arrest or arrhythmogenic syncope, while they are unconclusive about the management of asymptomatic patients, who represent ∼90% of Brugada patients. We recently demonstrated that in asymptomatic patients, the presence of spontaneous Brugada type 1 electrocardiogram (ECG) pattern and inducibility of ventricular arrhythmias at electrophysiological study allows us to identify a group of patients at greater risk who deserve treatment. Regarding treatment, there are three options: implantable cardioverter defibrillator, drugs, and epicardial transcatheter ablation. Recent studies have shown that the latter is effective and free from serious side effects, thus opening a new scenario in the treatment of Brugada patients at risk. Subjects who present drug-induced-only type 1 Brugada ECG pattern, in whom a spontaneous type 1 pattern has been ruled out with repeated ECGs and 12-lead 24-h Holter monitoring, represent a very low-risk group, provided they adhere to behavioural recommendations and undergo regular follow-up.

Intracardiac electrophysiology to characterize susceptibility to ventricular arrhythmias in murine models

Introduction: Sudden cardiac death (SCD) and ventricular fibrillation are rare but severe complications of many cardiovascular diseases and represent a major health issue worldwide. Although the primary causes are often acute or chronic coronary diseases, genetic conditions, such as inherited channelopathies or non-ischemic cardiomyopathies are leading causes of SCD among the young. However, relevant experimental models to study the underlying mechanisms of arrhythmias and develop new therapies are still needed. The number of genetically engineered mouse models with cardiac phenotype is growing, making electrophysiological studies in mice essential tools to study arrhythmogenicity and arrhythmia mechanisms and to test novel treatments. Recently, intracardiac catheterization via the jugular vein was described to induce and record ventricular arrhythmias in living anesthetized mice. Several strategies have been reported, developed in healthy wild-type animals and based on aggressive right ventricular stimulation. Methods: Here, we report a protocol based on programmed electrical stimulation (PES) performed in clinical practice in patients with cardiac rhythm disorders, adapted to two transgenic mice models of arrhythmia - Brugada syndrome and cardiolaminopathy. Results: We show that this progressive protocol, based on a limited number of right ventricular extrastimuli, enables to reveal different rhythmic phenotypes between control and diseased mice. In this study, we provide detailed information on PES in mice, including catheter positioning, stimulation protocols, intracardiac and surface ECG interpretation and we reveal a higher susceptibility of two mouse lines to experience triggered ventricular arrhythmias, when compared to control mice. Discussion: Overall, this technique allows to characterize arrhythmias and provides results in phenotyping 2 arrhythmogenic-disease murine models.