Impact of clinical and genetic findings on the management of young patients with Brugada syndrome

Gender Differences in Prognosis and Risk Stratification of Brugada Syndrome: A Pooled Analysis of 4,140 Patients From 24 Clinical Trials

Background: Male gender has been consistently shown to be a risk factor for a greater number of arrhythmic events in patients with Brugada Syndrome (BrS). However, there have been no large-scale comprehensive pooled analyses to statistically and systematically verify this association. Therefore, we conducted a pooled analysis on gender differences in prognosis and risk stratification of BrS with a largest sample capacity at present.

Methods: We searched PubMed, Embase, Medline, Cochrane Library databases, Chinese National Knowledge Infrastructure, and Wanfang Data for relevant studies published from 2002 to 2017. The prognosis and risk stratification of BrS and risk factors were then investigated and evaluated according to gender.

Results: Twenty-four eligible studies involving 4,140 patients were included in the analysis. Male patients (78.1%) had a higher risk of arrhythmic events than female patients (95% confidence interval: 1.46–2.91, P < 0.0001). Among the male population, there were statistical differences between symptomatic patients and asymptomatic patients (95% CI: 2.63–7.86, P < 0.00001), but in the female population, no statistical differences were found. In the female subgroup, electrophysiological study (EPS) positive patients had a tendency toward a higher risk of arrhythmic events than EPS-negative patients (95% CI: 0.93–29.77, P = 0.06).

Conclusions: Male patients are at a higher risk of arrhythmic events than female patients. Within the male population, symptomatic patients have a significantly higher risk profile compared to asymptomatic patients, but no such differences are evident within the female population. Consequently, in the female population, the risk of asymptomatic patterns cannot be underestimated.

SCN5A mutation status increases the risk of major arrhythmic events in Asian populations with Brugada syndrome: systematic review and meta-analysis

BACKGROUND

Brugada syndrome (BrS) is an inherited arrhythmic disease linked to SCN5A mutations. It is controversial whether SCN5A mutation carriers possess a greater risk of major arrhythmic events (MAE). We examined the association of SCN5A mutations and MAE in BrS patients.

METHODS

We comprehensively searched the databases of MEDLINE and EMBASE from inception to September 2017. Included studies were published cohort and case-control studies that compared MAE in BrS patients with and without SCN5A mutations. Data from each study were combined using the random-effects model. Generic inverse variance method of DerSimonian and Laird was employed to calculate the risk ratios (RR) and 95% confidence intervals (CI).

RESULTS

Seven studies from March 2002 to October 2017 were included (1,049 BrS subjects). SCN5A mutations were associated with MAE in Asian populations (RR = 2.03, 95% CI: 1.37-3.00, p = 0.0004, I²  = 0.0%), patients who were symptomatic (RR = 2.66, 95% CI: 1.62-4.36, p = 0.0001, I²  = 23.0%), and individuals with spontaneous type-1 Brugada pattern (RR = 1.84, 95% CI: 1.05-3.23, p = 0.03, I²  = 0.0%).

CONCLUSIONS

SCN5A mutations in BrS increase the risk of MAE in Asian populations, symptomatic BrS patients, and individuals with spontaneous type-1 Brugada pattern. Our study suggests that SCN5A mutation status should be an important tool for risk assessment in BrS patients.

Brugada syndrome in the young: an assessment of risk factors predicting future events

Aims

To investigate the clinical characteristics, prognoses, and presence of risk factors in young patients with Brugada syndrome (BS).

Methods and results

A consecutive cohort of 128 young BS patients (≤25 years old at diagnosis) was analysed. Eighty-eight patients (69%) were asymptomatic, whereas 40 (31%) presented with clinical manifestations of BS. Markers of prognosis and risk were identified upon comparison of these two groups. A history of malignant syncope was strong predictors of ventricular arrhythmic events. Family history of sudden cardiac death (SCD) and mutations in the SCN5A gene did not associate with increased risk. Symptomatic patients presented with significantly abnormal baseline electrical characteristics when compared with the asymptomatic cohort, including spontaneous type I electrocardiograph (ECG) patterns, sinus node dysfunction (SND), first-degree atrioventricular (AV) block, and intra-ventricular conduction delay. The symptomatic group more frequently exhibited atrial arrhythmias. Electrophysiological studies resulted positive more frequently in symptomatic patients, but no risk association for future events could be determined. During the follow-up period (mean: 65 months), 10 arrhythmic events occurred in nine symptomatic patients (event rate: 4.5% per year). No events occurred in the asymptomatic group. Variables significantly associated with arrhythmic events during follow-up were presence of symptoms at diagnosis and spontaneous type I ECG. The presence of atrial arrhythmias and conduction abnormalities was also associated with the risk of arrhythmic events during follow-up.

Conclusion

Symptomatic BS in the young age is a rare but malignant condition that can manifest with a spectrum of electrical abnormalities (i.e. SND, atrial tachycardias, AV block, and infra-nodal conduction delay) and result in the extreme cases in lethal arrhythmic events and SCD.

Cardiac channelopathies: The role of sodium channel mutations

INTRODUCTION AND OBJECTIVES

The importance of sodium channels for the normal electrical activity of the heart is emphasized by the fact that mutations (inherited or de novo) in genes that encode for these channels or their associated proteins cause arrhythmogenic syndromes such as the Brugada syndrome and the long QT syndrome (LQTS). The aim of this study is to conduct a review of the literature on the mutations in the sodium channel complex responsible for heart disease and the implications of a close relationship between genetics and the clinical aspects of the main cardiac channelopathies, namely at the level of diagnosis, risk stratification, prognosis, screening of family members and treatment.

METHODS

The online Pubmed® database was used to search for articles published in this field in indexed journals. The MeSH database was used to define the following query: "Mutation [Mesh] AND Sodium Channels [Mesh] AND Heart Diseases [Mesh]", and articles published in the last 15 years, written in English or Portuguese and referring to research in human beings were included.

CONCLUSIONS

In the past few years, significant advances have been made to clarify the genetic and molecular basis of these syndromes. A greater understanding of the underlying pathophysiological mechanisms showed the importance of the relationship between genotype and phenotype and led to progress in the clinical approach to these patients. However, it is still necessary to improve diagnostic capacity, optimize risk stratification, and develop new specific treatments according to the genotype-phenotype binomial.

Age of First Arrhythmic Event in Brugada Syndrome

Background

Data on the age at first arrhythmic event (AE) in Brugada syndrome are from limited patient cohorts. The aim of this study is 2-fold: (1) to define the age at first AE in a large cohort of patients with Brugada syndrome, and (2) to assess the influence of the mode of AE documentation, sex, and ethnicity on the age at first AE.

Methods and Results

A survey of 23 centers from 10 Western and 4 Asian countries gathered data from 678 patients with Brugada syndrome (91.3% men) with first AE documented at time of aborted cardiac arrest (group A, n=426) or after prophylactic implantable cardioverter–defibrillator implantation (group B, n=252). The vast majority (94.2%) of the patients were 16 to 70 years old at the time of AE, whereas pediatric (<16 years) and elderly patients (>70 years) comprised 4.3% and 1.5%, respectively. Peak AE rate occurred between 38 and 48 years (mean, 41.9±14.8; range, 0.27–84 years). Group A patients were younger than in Group B by a mean of 6.7 years (46.1±13.2 versus 39.4±15.0 years; P <0.001). In adult patients (≥16 years), women experienced AE 6.5 years later than men ( P =0.003). Whites and Asians exhibited their AE at the same median age (43 years).

Conclusions

SABRUS (Survey on Arrhythmic Events in Brugada Syndrome) presents the first analysis on the age distribution of AE in Brugada syndrome, suggesting 2 age cutoffs (16 and 70 years) that might be important for decision-making. It also allows gaining insights on the influence of mode of arrhythmia documentation, patient sex, and ethnic origin on the age at AE.

Genetic causes of sudden cardiac death in children: inherited arrhythmogenic diseases

PURPOSE OF REVIEW

In this chapter we will discuss the most recent and relevant evidences published in the field of inherited arrhythmogenic disorders, focusing on the so called 'channelopathies' that are associated with sudden cardiac death (SCD) in children: long QT syndrome (LQTS), short QT syndrome (SQTS), Brugada syndrome (BrS), and catecholaminergic polymorphic ventricular tachycardia (CPVT).

RECENT FINDINGS

We will discuss the latest diagnostic criteria for channelopathies released by the European Society of Cardiology, the new data on BrS in children and the recent evidence supporting a genotype-specific therapy for LQTS type 3. Moreover, we will present further insights into the risk stratification of the children affected by LQTS, analyzing the role of imaging for the prediction of life-threatening arrhythmias. In addition, we will offer a perspective on how to deal with genetic results in families affected by SCD at very young ages.

SUMMARY

The selected publications will aid pediatricians in their clinical work when managing little patients with inherited arrhythmias, providing the most recent information for diagnosis, risk stratification, and management.

Sudden infant death syndrome and inherited cardiac conditions

Sudden infant death syndrome (SIDS) is the leading cause of post-neonatal infant mortality in developed countries, characterized by the death of infants for no obvious reason and without prior warning. The complex interaction of multiple factors in the pathogenesis of SIDS is illustrated by the 'triple risk hypothesis', which proposed that SIDS results from a convergence of three overlapping risk factors: a critical developmental period, an exogenous stressor, and underlying genetic and/or nongenetic vulnerability in the infant. Rare variants in genes associated with inherited arrhythmia syndromes and cardiomyopathies have been proposed as the substrate for an infant's critical vulnerability in a small subset of SIDS cases. Given the potential risk of inherited cardiac disease, current guidelines recommend post-mortem genetic testing (molecular autopsy) and cardiological investigation of the surviving family, complemented by targeted genetic testing if appropriate. In this Review, we highlight the latest developments in understanding the spectrum and prevalence of cardiac-mediated SIDS, and discuss the clinical implications of SIDS in the surviving family and the general population.

A Clinical Score Model to Predict Lethal Events in Young Patients (≤19 Years) With the Brugada Syndrome

Risk stratification in Brugada syndrome in young patients remains challenging. We investigated the clinical characteristics, prognosis, and risk in young patients with the Brugada syndrome. We studied 95 patients with the Brugada syndrome aged ≤19 years. The median age at diagnosis was 12.9 years. The clinical presentation was sudden cardiac death in 7% and syncope in 21%. The remaining 72% were asymptomatic at diagnosis. Electrical abnormalities were present in 36%, including spontaneous type I electrocardiogram (12%), sinus node dysfunction (9%), atrioventricular block (17%), intraventricular conduction delay (16%), and atrial arrhythmias (8%). An electrophysiologic study was performed in 75%; ventricular arrhythmias were induced in 3%. An implantable cardioverter-defibrillator was placed in 25%. During a mean follow-up of 59 months, 9 patients presented with arrhythmic events (event rate: 1.9% per year). Variables significantly associated with events were: presentation with sudden cardiac death or syncope, spontaneous type I electrocardiogram, sinus node dysfunction and/or atrial tachycardia, conduction abnormality, and induction of ventricular arrhythmias during programmed ventricular stimulation. A model including the previous 4 main clinical variables (1, sudden cardiac death or syncope; 2, spontaneous type I electrocardiogram; 3, sinus node dysfunction and/or atrial tachycardia; and 4, conduction abnormality) had a high predictive power (C: 0.93) for the risk of lethal events. A score of ≥4 conferred a 5-year event probability of 30% that increased to 53% if the score was ≥6. In conclusion, our study validated a model to predict risk in young patients with the Brugada syndrome, which takes into account 4 clinical measures.

Genetic Testing in Inherited Heart Diseases: Practical Considerations for Clinicians

PURPOSE OF REVIEW

Genetic testing has become an important element in the care of patients with inherited cardiac conditions (ICCs). The purpose of this review is to provide clinicians with insights into the utility of genetic testing as well as challenges associated with interpreting results.

RECENT FINDINGS

Genetic testing may be indicated for individuals who are affected with or who have family histories of various ICCs. Various testing options are available and determining the most appropriate test for any given clinical scenario is key when interpreting results. Newly published guidelines as well as various publicly accessible tools are available to clinicians to help with interpretation of genetic findings; however the subjectivity with respect to variant classification can make accurate assessment challenging. Genetic information can provide highly useful and relevant information for patients, their family members, and their healthcare providers. Given the potential ramifications of variant misclassification, expertise in both clinical phenotyping and molecular genetics is imperative in order to provide accurate diagnosis, management recommendations, and family risk assessment for this patient population.

Hypothetical "anatomy" of Brugada phenomenon: "Long QT sine Long QT" syndrome implicating morphologically undefined specific "Brugada's myocells"

The Brugada syndrome (BrS) is associated with increased risk of ventricular arrhythmias and sudden cardiac death. It generates genetically mediated arrhythmias posing a true pathophysiological challenge. In search of the similarities between BrS and long QT syndrome some novel insights are suggested. In patients with BrS the duration of QT interval is usually normal. Some investigators have found prolonged QT interval in the syndrome's natural course or the duration of QT segment have been extended by provocative tests unmasking BrS. Thus, BrS might be characterized as "long QT sine long QT" syndrome. The existence of two functional types of myocites is suspected. Regarding structure and function the majority of ventricular myocardium is probably mostly healthy. The rest of myocardium (preferably the subepicardium of right ventricular outflow tract) due to its genotypic peculiarities demonstrates no negative influence on ventricular performance until early adulthood is reached and/or other unstable preconditions are fulfilled (nocturnal time, fever, specific drugs, etc.). Based on published findings of positive outcomes, following the epicardial ablation of the right ventricular outflow tract region, a new hypothetical concept suggesting the presence of specific, genetically affected "Brugada's myocells" is proposed. These cells as a suitable arrhythmogenic substrate reside intramurally within the subepicardial region of the outflow tract of right ventricle. In the daytime these cells likely are dormant but at rest their nocturnal proarrhythmic behavior is activated occasionally. Presumptions regarding the pathophysiology of BrS might be the focus of further discussion.

Pathogenesis and management of Brugada syndrome

Brugada syndrome is an inherited disease characterized by an increased risk of sudden cardiac death owing to ventricular arrhythmias in the absence of structural heart disease. Since the first description of the syndrome >20 years ago, considerable advances have been made in our understanding of the underlying mechanisms involved and the strategies to stratify at-risk patients. The development of repolarization-depolarization abnormalities in patients with Brugada syndrome can involve genetic alterations, abnormal neural crest cell migration, improper gap junctional communication, or connexome abnormalities. A common phenotype observed on the electrocardiogram of patients with Brugada syndrome might be the result of different pathophysiological mechanisms. Furthermore, risk stratification of this patient cohort is critical, and although some risk factors for Brugada syndrome have been frequently reported, several others remain unconfirmed. Current clinical guidelines offer recommendations for patients at high risk of developing sudden cardiac death, but the management of those at low risk has not yet been defined. In this Review, we discuss the proposed mechanisms that underlie the development of Brugada syndrome and the current risk stratification and therapeutic options available for these patients.

The Brugada Syndrome: A Rare Arrhythmia Disorder with Complex Inheritance

For the last 10 years, applying new sequencing technologies to thousands of whole exomes has revealed the high variability of the human genome. Extreme caution should thus be taken to avoid misinterpretation when associating rare genetic variants to disease susceptibility. The Brugada syndrome (BrS) is a rare inherited arrhythmia disease associated with high risk of sudden cardiac death in the young adult. Familial inheritance has long been described as Mendelian, with autosomal dominant mode of transmission and incomplete penetrance. However, all except 1 of the 23 genes previously associated with the disease have been identified through a candidate gene approach. To date, only rare coding variants in the SCN5A gene have been significantly associated with the syndrome. However, the genotype/phenotype studies conducted in families with SCN5A mutations illustrate the complex mode of inheritance of BrS. This genetic complexity has recently been confirmed by the identification of common polymorphic alleles strongly associated with disease risk. The implication of both rare and common variants in BrS susceptibility implies that one should first define a proper genetic model for BrS predisposition prior to applying molecular diagnosis. Although long remains the way to personalized medicine against BrS, the high phenotype variability encountered in familial forms of the disease may partly find an explanation into this specific genetic architecture.

Brugada Syndrome: Defining the Risk in Asymptomatic Patients

Since the first description of the Brugada syndrome (BS) in 1992, scientific progress in the understanding of this disease has been enormous; at the same time more and more individuals with the disease have been diagnosed. The profile of patients with BS has changed with more asymptomatic individuals and less expressive clinical features. Asymptomatic BS individuals are at lower arrhythmic risk than those presenting with syncope or sudden cardiac death (SCD). The event incidence rate is around 0.5 % per year; this figure is relevant due to the fact that individuals have a long life expectancy and are otherwise healthy. As a result of the risk of SCD, risk stratification is of utmost importance. As the implantation of a cardioverter defibrillator is the main treatment for those patients at higher risk, benefits and long-term potential risks have to be adequately considered. Some risk factors, such as spontaneous type 1 electrocardiogram (ECG) pattern, are widely accepted, whilst for others contradictory data are present. Furthermore, novel risk factors are now available that might help in the management of BS. The presence of a spontaneous type 1 ECG pattern, history of sinus node dysfunction and inducible ventricular arrhythmias during programmed electrical stimulation of the heart allow us to risk stratify these patients.