More than 30 years of Brugada syndrome: a critical appraisal of achievements and open issues

Over the last three decades, what is referred to as Brugada syndrome (BrS) has developed from a clinical observation of initially a few cases of sudden cardiac death (SCD) in the absence of structural heart disease with ECG signs of "atypical right bundle brunch block" to a predominantly electrocardiographic, and to a lesser extent genetic, diagnosis. Today, BrS is diagnosed in patients without overt structural heart disease and a spontaneous Brugada type 1 ECG pattern regardless of symptoms. The diagnosis of BrS is less clear in those with an only transient or drug-induced type 1 Brugada pattern, but should be considered in the presence of an arrhythmic syncope, family history of BrS, or family history of sudden death. In addition to survived cardiac arrest, syncope is probably the single most decisive risk marker for future arrhythmias. For asymptomatic BrS, risk stratification remains challenging. General recommendations to lower the risk in BrS include avoidance of drugs/agents known to induce and/or increase right precordial ST-segment elevation, including treatment of fever with antipyretic drugs. Several ECG markers that have been associated with an increased risk of SCD have been incorporated into a recently published risk score for BrS. The aim of this article is to provide an overview of the status of risk stratification and to illustrate open issues und gaps in evidence in BrS.

Common electrocardiogram measures are not associated with telomere length

AIMS

Aging is accompanied by telomere shortening. Increased telomere shortening is considered a marker of premature aging. Cardiac aging results in the development of cardiac pathologies. Electrocardiogram (ECG) measures reflect cardiac excitation, conduction, and repolarization. ECG measures also prolong with aging and are associated with cardiac pathologies including atrial fibrillation. As premature prolongation of ECG measures is observed, we hypothesized that such prolongation may be associated with telomere length.

METHODS AND RESULTS

We studied the large, community-based KORA F4 Study. Of 3,080 participants enrolled between 2006 and 2007 with detailed information on demographic, anthropometric, clinical, and ECG characteristics, 2,575 presented with available data on leukocyte telomere length. Telomere length was determined by real-time quantitative PCR and expressed relative to a single copy gene. We fitted multivariable adjusted linear regression models to associate the ECG measures RR-interval, PR-interval, QRS-duration, and heart rate corrected QTc with telomere length. In our cohort, the mean age was 54.9±12.9 years and 46.6% were men. Increased age was associated with shorter telomere length (p<0.01), and men had shorter telomere length than women (p<0.05). In unadjusted models, heart rate (p=0.023), PR-interval (p<0.01), and QTc-interval (p<0.01) were significantly associated with shorter telomere length. However, no significant associations remained after accounting for age, sex, and covariates.

CONCLUSIONS

ECG measures are age-dependent, but not associated with shortened telomere length as a marker of biological aging. Further research is warranted to clarify if shortened telomeres are associated with clinical cardiac pathologies including atrial fibrillation.

Prevalence and Related Characteristics of Patients with Brugada Pattern Electrocardiogram in Santa Catarina, Brazil

Fundamento:

A síndrome de Brugada é um distúrbio arritmogênico hereditário caracterizado pela presença de características eletrocardiográficas específicas com ou sem sintomas. Os pacientes apresentam risco aumentado de morte súbita por fibrilação ventricular. A prevalência desse padrão eletrocardiográfico difere de acordo com a região estudada. Porém, informações epidemiológicas, incluindo a população brasileira, são escassas.

Objetivo:

Avaliar a prevalência do padrão eletrocardiográfico da síndrome de Brugada e o perfil epidemiológico associado a ela.

Métodos:

Estudo transversal que incluiu 846.533 registros ECG de 716.973 pacientes do banco de dados de eletrocardiograma (ECG) da Rede de Telemedicina de Santa Catarina por um período de quatro anos. Todos os exames foram ECG de 12 derivações convencionais (sem V1 e V2 em posições altas). Os exames identificados com o diagnóstico de “Síndrome de Brugada” (tipos 1 e 2) foram revisados por um eletrofisiologista. Foram considerados significativos valores de p<0,05.

Resultados:

Apresentavam padrão potencialmente consistente com ECG do tipo Brugada 83 pacientes. Destes, 33 foram confirmados com padrão de Brugada tipo 1, e 22 com tipo 2, após reavaliação. A prevalência de ECG do tipo 1 de Brugada foi de 4,6 por 100.000 pacientes. O ECG do tipo Brugada 1 foi associado ao sexo masculino (81,8% vs. 41,5%, p<0,001) e menor prevalência de obesidade (9,1% vs. 26,4%, p=0,028).

Conclusões:

Este estudo mostrou baixa prevalência de ECG do tipo Brugada no sul do Brasil. A presença de ECG com padrão Brugada tipo 1 esteve associada ao sexo masculino e menor prevalência de obesidade que a população geral.

The 10-Year Prognosis and Prevalence of Brugada-Type Electrocardiograms in Elderly Women: A Longitudinal Nationwide Community-Based Prospective Study

BACKGROUND

Brugada syndrome is a disorder associated with sudden cardiac death and characterized by an abnormal electrocardiogram (ECG). Previous studies were predominantly conducted in men, and the data on long-term prognosis are limited. Information about women, especially elderly women, is lacking.

OBJECTIVE

The aim of this study was to investigate the long-term prognosis of the Brugada ECG pattern in elderly women.

METHOD

We investigated the 10-year prognosis of the Brugada ECG pattern in elderly women in a nationwide community-based population in Taiwan. Community-dwelling women older than 55 years were prospectively recruited from December 2008 to March 2013 by a stratified random sampling method. All enrolled individuals were followed up annually until April 2019, and the cause of death was documented by citizen death records.

RESULTS

Among 2597 women, 60 (2.31%) had a Brugada-type ECG, and this prevalence was higher than the mean global prevalence of 0.23%. One woman had a type 1 ECG (0.04%), whereas 15 (0.58%) and 44 (1.70%) women had type 2 and type 3 ECG patterns, respectively. Cox survival analysis revealed that all-cause mortality and cardiac mortality were similar in the individuals with and without a Brugada-type ECG during a mean follow-up of 96.1 ± 20.5 months.

CONCLUSIONS

Our findings suggest that Brugada ECG patterns are not infrequent in elderly women but are not associated with increased risk of mortality in long-term follow-up; these findings may help reduce unnecessary anxiety for physicians, nurses, allied health caregivers, and patients.

Abnormal Electrocardiographic Findings in the Population Older Than 40 Years. Prevalence and Clinical Significance. Results of the OFRECE Study

INTRODUCTION AND OBJECTIVES

Abnormal electrocardiographic findings are highly common. The aim of this study was to analyze the prevalence of abnormal electrocardiographic patterns in the general Spanish population aged 40 years or older.

METHODS

This subanalysis of the OFRECE study selected a representative sample of the Spanish population aged 40 years or older. Clinical data and electrocardiograms were available in all participants. The electrocardiograms were read centrally. Each electrocardiogram was independently assessed by 2 trained cardiologists and, if there was disagreement, a third was consulted to reach a consensus-based diagnosis. Prior to reading the electrocardiograms, diagnostic criteria were strictly defined for each of the abnormalities analyzed. We analyzed the prevalence and clinical factors associated with cavity enlargement, conduction disorders, repolarization abnormalities, pathological Q waves, atrial and ventricular premature beats, and pre-excitation.

RESULTS

A total of 8343 individuals were evaluated, (mean age, 59.2 years; 52.4% women). Only 4074 (51.2%) participants had a completely normal electrocardiogram. The most frequent abnormalities were nonspecific repolarization abnormalities (16%) associated with coronary heart disease and atrial fibrillation; right bundle-branch block (8.1%) associated with chronic pulmonary obstructive disease; left anterior hemiblock (6.5%) related to hypertension and congestive heart failure; and long PR interval (3.7%), which was associated with coronary heart disease.

CONCLUSIONS

Electrocardiographic abnormalities are very common in the general population aged 40 years or older. Only about half of the population had a completely normal electrocardiogram.

Recent advances in the treatment of Brugada syndrome

INTRODUCTION

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

Comparisons of clinical impacts on individuals with Brugada electrocardiographic patterns defined by ISHNE criteria or EHRA/HRS/APHRS criteria: a nationwide community-based study

INTRODUCTION

Identifying Brugada electrocardiographic pattern (BrP) early is crucial to prevent sudden cardiac death. Two different diagnostic criteria proposed by International Society for Holter and Noninvasive Electrocardiography (ISHNE) and Heart Rhythm Society/European Heart Rhythm Association/Asia-Pacific Heart Rhythm Society (HRS/EHRA/APHRS) were widely used in clinical practice. The difference in prevalence and prognosis of BrP by applying the two different criteria was never studied before.

METHODS

This study was prospectively conducted in a nationwide large-scale stratified random sampling community-based cohort (HALST) from Han Chinese population in Taiwan from December 2008 to December 2012. We compared the prevalence and prognosis of BrP defined by the two diagnostic criteria.

RESULTS

A total of 5214 adults were enrolled (2530 men) with mean age of 69.3 years. Four had spontaneous type 1 BrP (0.077%). By the HRS/EHRA/APHRS criteria, 68 individuals have type 2 BrP (1.30%) and 101 have type 3 BrP (1.94%) whereas by the ISHNE criteria, 46 individuals exhibited type 2 BrP (0.88%). When applying the ISHNE criteria, the number of individuals with BrP decreased by 71%. However, all-cause mortality and cardiovascular mortality were not different between individuals with or without BrP, irrespective of the criteria used.

CONCLUSIONS

The two different criteria may impact the diagnostic yield of individuals with BrP, but do not affect the prognosis of the individuals with BrP. Key messages Comparing with the use of HRS/EHRA/APHRS criteria, the number of individuals with Brugada ECG patterns was decreased by 71% when applying the ISHNE criteria. The prognosis of individuals with Brugada ECG patterns defined by 2012 ISHNE or 2013 HRS/EHRA/APHRS criteria were not different.

Prevalence of spontaneous Brugada ECG pattern recorded at standard intercostal leads: A meta-analysis

OBJECTIVE

Typical Brugada ECG pattern is the keystone in the diagnosis of Brugada syndrome. However, the exact prevalence remains unclear, especially in Asia. The present study was designed to systematically evaluate the prevalence of spontaneous Brugada ECG pattern recorded at standard leads.

METHODS

We searched the Medline, Embase and Chinese National Knowledge Infrastructure (CNKI) for studies of the prevalence of Brugada ECG pattern, published between Jan 1, 2003, and September 1, 2016. Pooled prevalence of type 1 and type 2-3 Brugada ECG pattern were estimated in a random-effects model, and group prevalence data by the characteristic of studies. Meta-regression analyses were performed to explore the potential sources of heterogeneity, and sensitivity analyses were conducted to assess the effect of each study on the overall prevalence.

RESULTS

Thirty-nine eligible studies involving 558,689 subjects were identified. Pooled prevalence of type 1 and 2-3 Brugada ECG pattern was 0.03% (95%CI, 0.01%-0.06%), and 0.42% (95%CI, 0.28%-0.59%), respectively. Regions, sample size, year of publication were the main source of heterogeneity. The prevalence of type 1 Brugada ECG pattern was higher in male, Asia, adult, patient, and fever subjects; but the relation between fever and type 2-3 Brugada ECG pattern was not significant. Sensitivity analysis showed that each study did not lonely affect the prevalence of type 1 and type 2-3 Brugada ECG pattern.

CONCLUSION

Brugada ECG pattern is not rare, especially preponderant in adult Asian males, and fever subjects. Clinical screening and further examination of Brugada syndrome in potential population need to be highlighted.

Brugada syndrome: A general cardiologist's perspective

Brugada syndrome (BrS) is one of the commonest inherited primary arrhythmia syndromes typically presenting with arrhythmic syncope or sudden cardiac death (SCD) due to polymorphic ventricular tachycardia and ventricular fibrillation precipitated by vagotonia or fever in apparently healthy adults, less frequently in children. The prevalence of the syndrome (0.01%-0.3%) varies among regions and ethnicities, being the highest in Southeast Asia. BrS is diagnosed by the "coved type" ST-segment elevation≥2mm followed by a negative T-wave in ≥1 of the right precordial leads V₁-V₂. The typical electrocardiogram in BrS is often concealed by fluctuations between normal, non-diagnostic and diagnostic ST-segment pattern in the same patient, thus hindering the diagnosis. Presently, the majority of BrS patients is incidentally diagnosed, and may remain asymptomatic for their lifetime. However, BrS is responsible for 4-12% of all SCDs and for ~20% of SCDs in patients with structurally normal hearts. Arrhythmic risk is the highest in SCD survivors and in patients with spontaneous BrS electrocardiogram and arrhythmic syncope, but risk stratification for SCD in asymptomatic subjects has not yet been fully defined. Recent achievements have expanded our understanding of the genetics and electrophysiological mechanisms underlying BrS, while radiofrequency catheter ablation may be an effective new approach to treat ventricular tachyarrhythmias in BrS patients with arrhythmic storms. The present review summarizes our contemporary understanding and recent advances in the inheritance, pathophysiology, clinical assessment and treatment of BrS patients.

Brugada syndrome: a fatal disease with complex genetic etiologies - still a long way to go

Brugada syndrome (BrS) is an arrhythmogenic disorder which was first described in 1992. This disease is a channelopathy characterized by ST-segment elevations in the right precordial leads and is susceptible to sudden death. BrS is a fatal disease with gender and age preferences. It occurs mainly in young male subjects with a structurally normal heart and silently progresses to sudden death with no significant symptoms. The prevalence of BrS has been reported in the ranges of 5–20 per 10 000 people. The disease is more prevalent in Asia. Nowadays, numerous variations in 23 genes have been linked to BrS since the first gene SCN5A has been associated with BrS in 1998. Not only can clinical specialists apply these discoveries in risk assessment, diagnosis and personal medicine, but also forensic pathologists can make full use of these variations to conduct death cause identification. However, despite the progress in genetics, these associated genes can only account for approximately 35% of the BrS cases while the etiology of the remaining BrS cases is still unexplained. In this review, we discussed the prevalence, the genes associated with BrS and the application of molecular autopsy in forensic pathology. We also summarized the present obstacles, and provided a new insight into the genetic basis of BrS.

Prevalence of Electrocardiographic Patterns Associated With Sudden Cardiac Death in the Spanish Population Aged 40 Years or Older. Results of the OFRECE Study

INTRODUCTION AND OBJECTIVES

Some electrocardiographic patterns are associated with an increased risk of sudden cardiac death due to ventricular arrhythmias. There is no information on the prevalence of these patterns in the general population in Spain. The objective of this study was to analyze the prevalence of these patterns and associated clinical and epidemiological factors.

METHODS

This subanalysis of the OFRECE study selected a representative sample of the Spanish population aged ≥ 40 years. We studied the presence or absence of electrocardiographic patterns of Brugada syndrome and QT interval abnormalities. Clinical data and electrocardiograms were available in all participants. Electrocardiograms were evaluated by 2 cardiologists and a third cardiologist was consulted if there was disagreement in the diagnosis. We calculated the weighted prevalence and clinical factors associated with the presence of Brugada-type patterns or QT segment abnormalities.

RESULTS

Overall, 8343 individuals were evaluated (59.2 years, 52.4% female). There were 12 Brugada cases (type 1, 2 cases; type 2, 10 cases; weighted prevalence, 0.13%). For corrected QT (QTc) analysis, we excluded participants with left bundle branch block or without sinus rhythm. Weighted prevalences were as follows: short QTc (< 340ms) 0.18%, borderline QTc (441-469ms) 8.33%, long QTc (≥ 470ms criterion) 1.01% and long QTc (≥ 480 criterion) 0.42%.

CONCLUSIONS

A total of 0.6% to 1.1% of the Spanish population aged ≥ 40 years has an electrocardiographic pattern associated with a higher risk of sudden death (Brugada syndrome, long QT, or short QT).

Long-Term Prognosis of Brugada-Type ECG and ECG With Atypical ST-Segment Elevation in the Right Precordial Leads Over 20 Years: Results From the Circulatory Risk in Communities Study (CIRCS)

Background

Brugada syndrome is recognized as being associated with sudden cardiac death; however, the prevalence of non–type 1 Brugada‐type ECG (BrS) or atypical ST‐segment elevation in the right precordial leads (STERP) and the long‐term prognosis for those patients remain unknown.

Methods and Results

We analyzed standard 12‐lead ECGs of 7178 apparently healthy participants (age range 40–64 years) who underwent health checkups from 1982 to 1986 in the Circulatory Risk in Communities Study, a prospective, large, community‐based cohort study in Japan. ECGs with J point amplitude ≥0.2 mV in the right precordial leads were divided into 3 groups: (1) type 1 BrS, (2) type 2 or 3 BrS (non‐type 1 BrS), and (3) STERP. The others served as the non–ST‐segment elevation group. We identified 8 participants (0.1%) with type1 BrS, 84 (1.2%) with non–type 1 BrS, and 228 (3.2%) with STERP. During a median follow‐up of 18.7 years (133 987.0 person‐years), sudden cardiac death was observed in no participants (0.0%) with type 1 BrS, in 1 (1.2%) with non–type 1 BrS, in 7 (3.1%) with STERP, and in 50 (0.7%) with non–ST‐segment elevation. Participants with STERP had a markedly elevated risk of sudden cardiac death (multivariable hazard ratio 3.9, 95% CI 1.7–9.0).

Conclusions

STERP was associated with an elevated risk of sudden cardiac death in a middle‐aged population.

Genetics of sudden cardiac death

Sudden cardiac death (SCD) is defined by the World Health Organization (WHO) as death within 1 h of symptom onset (witnessed) or within 24 h of being observed alive and symptom free (unwitnessed). It affects more than 3 million people annually worldwide and affects approximately 1/1000 people each year in the USA. Familial studies of syndromes with Mendelian inheritance, candidate genes analyses, and genome-wide association studies (GWAS) have helped our understanding of the genetics of SCD. We will review the genetics of arrhythmogenic hereditary syndromes with Mendelian inheritance from familial studies with structural heart disease (hypertrophic cardiomyopathy, dilated cardiomyopathy, and arrhythmogenic cardiomyopathy) as well as primary electrical causes (long QT syndrome, Brugada syndrome, catecholaminergic polymorphic ventricular tachycardia, and short QT syndrome). In addition, we will review the genetics of intermediate phenotypes for SCD such as coronary artery disease and electrocardiographic variables (QT interval, QRS duration, and RR interval). Finally, we will review rare and common variants that are associated with SCD in the general population and were identified from candidate gene analyses and GWAS. Our understanding of the genetics of SCD will improve by the use of next-generation sequencing/whole-exome sequencing as well as whole-genome sequencing which have the potential to discover unsuspected common and rare genetic variants that might be associated with SCD.

Brugada Syndrome

Brugada syndrome might stay undetected in patients until surviving cardiac arrest. Despite the prominent advances in exploring the disease in the past 2 decades, many questions remain unanswered and the controversies continue. Despite all mutations identified to be associated with the disease, two-thirds of cases have a negative genetic test. Future studies should be more directed on modulating factors and their impact on patients' risk for sudden death to help physicians in risk stratifying their patients and optimally implementing an implantable cardioverter defibrillator to prevent sudden cardiac death.

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

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

Electrocardiographic T Wave Abnormalities and the Risk of Sudden Cardiac Death: The Finnish Perspective

The identification of patients at risk for sudden cardiac death (SCD) is still a significant challenge to clinicians and scientists. Noninvasive identification of high-risk patients has been of great interest, and several ventricular depolarization and repolarization abnormalities in the standard 12-lead electrocardiogram (ECG) have been associated with increased vulnerability to lethal ventricular arrhythmias. Several benign and pathological conditions can induce changes in repolarization detected as alteration of the ST segment or T wave. Changes in the ST segment and T waves can be early markers of an underlying cardiovascular disease, and even minor ST-T abnormalities have predicted reduced survival and increased risk of SCD in the adult population. In this review, we will discuss the current knowledge of the SCD risk with standard 12-lead ECG T wave abnormalities in the general population, and possible T wave changes in various cardiac conditions predisposing to SCD.

The spectrum of epidemiology underlying sudden cardiac death

Sudden cardiac death (SCD) from cardiac arrest is a major international public health problem accounting for an estimated 15%-20% of all deaths. Although resuscitation rates are generally improving throughout the world, the majority of individuals who experience a sudden cardiac arrest will not survive. SCD most often develops in older adults with acquired structural heart disease, but it also rarely occurs in the young, where it is more commonly because of inherited disorders. Coronary heart disease is known to be the most common pathology underlying SCD, followed by cardiomyopathies, inherited arrhythmia syndromes, and valvular heart disease. During the past 3 decades, declines in SCD rates have not been as steep as for other causes of coronary heart disease deaths, and there is a growing fraction of SCDs not due to coronary heart disease and ventricular arrhythmias, particularly among certain subsets of the population. The growing heterogeneity of the pathologies and mechanisms underlying SCD present major challenges for SCD prevention, which are magnified further by a frequent lack of recognition of the underlying cardiac condition before death. Multifaceted preventative approaches, which address risk factors in seemingly low-risk and known high-risk populations, will be required to decrease the burden of SCD. In this Compendium, we review the wide-ranging spectrum of epidemiology underlying SCD within both the general population and in high-risk subsets with established cardiac disease placing an emphasis on recent global trends, remaining uncertainties, and potential targeted preventive strategies.

A mutation causing Brugada syndrome identifies a mechanism for altered autonomic and oxidant regulation of cardiac sodium currents

BACKGROUND

The mechanisms of the electrocardiographic changes and arrhythmias in Brugada syndrome (BrS) remain controversial. Mutations in the sodium channel gene, SCN5A, and regulatory proteins that reduce or eliminate sodium current (INa) have been linked to BrS. We studied the properties of a BrS-associated SCN5A mutation in a protein kinase A (PKA) consensus phosphorylation site, R526H.

METHODS AND RESULTS

In vitro PKA phosphorylation was detected in the I-II linker peptide of wild-type (WT) channels but not R526H or S528A (phosphorylation site) mutants. Cell surface expression of R526H and S528A channels was reduced compared with WT. Whole-cell INa through all channel variants revealed no significant differences in the steady-state activation, inactivation, and recovery from inactivation. Peak current densities of the mutants were significantly reduced compared with WT. Infection of 2D cultures of neonatal rat ventricular myocytes with WT and mutant channels increased conduction velocity compared with noninfected cells. PKA stimulation significantly increased peak INa and conduction velocity of WT but not mutant channels. Oxidant stress inhibits cardiac INa; WT and mutant INa decreases with the intracellular application of reduced nicotinamide adenine dinucleotide (NADH), an effect that is reversed by PKA stimulation in WT but not in R526H or S528A channels.

CONCLUSIONS

We identified a family with BrS and an SCN5A mutation in a PKA consensus phosphorylation site. The BrS mutation R526H is associated with a reduction in the basal level of INa and a failure of PKA stimulation to augment the current that may contribute to the predisposition to arrhythmias in patients with BrS, independent of the precipitants.

The genetic component of Brugada syndrome

Brugada syndrome (BrS) is a clinical entity first described in 1992. BrS is characterized by ST-segment elevations in the right precordial leads and susceptibility to ventricular arrhythmias and sudden cardiac death. It affects young subjects, predominantly males, with structurally normal hearts. The prevalence varies with ethnicity ranging from 1:2,000 to 1:100,000 in different parts of the world. Today, hundreds of variants in 17 genes have been associated with BrS of which mutations in SCN5A, coding for the cardiac voltage-gated sodium channel, accounts for the vast majority. Despite this, approximately 70% of BrS cases cannot be explained genetically with the current knowledge. Moreover, the monogenic role of some of the variants previously described as being associated with BrS has been questioned by their occurrence in about 4% (1:23) of the general population as found in NHLBI GO Exome Sequencing Project (ESP) currently including approximately 6500 individuals. If we add the variants described in the five newest identified genes associated with BrS, they appear at an even higher prevalence in the ESP (1:21). The current standard treatment of BrS is an implantable cardioverter-defibrillator (ICD). The risk stratification and indications for ICD treatment are based on the ECG and on the clinical and family history. In this review we discuss the genetic basis of BrS.

High prevalence of genetic variants previously associated with Brugada syndrome in new exome data

More than 300 variants in 12 genes have been associated with Brugada syndrome (BrS) which has a prevalence ranging between 1:2000 and 1:100,000. Until recently, there has been little knowledge regarding the distribution of genetic variations in the general population. This problem was partly solved, when exome data from the NHLI GO Exome Sequencing Project (ESP) was published. In this study, we aimed to report the prevalence of previously BrS-associated variants in the ESP population. We performed a search in ESP for variants previously associated with BrS. In addition, four variants in ESP were genotyped in a second Danish control population (n = 536) with available electrocardiograms. In ESP, we identified 38 of 355 (10%) variants, distributed on 272 heterozygote carriers and two homozygote carriers. The genes investigated were on average screened in 6258 individuals. This corresponds to a surprisingly high genotype prevalence of 1:23 (274:6258). Genotyping the four common ESP-derived variants CACNA2D1 S709N, SCN5A F2004L, CACNB2 S143F, and CACNB2 T450I in the Danish controls, we found a genotype prevalence comparable with that found in ESP. We suggest that exome data are used in research, as an additive tool to predict the pathogenicity of variants in patients suspected for BrS.

Repolarization syndromes

Repolarization syndromes, including early repolarization, Brugada, and short and long QT, have been implicated increasingly as causes of sudden cardiac death (SCD) despite no obvious mechanical cardiac abnormalities. So-called idiopathic ventricular fibrillation is now often reassigned to one of the aforementioned entities. Underlying causes are diverse; genetic mutation has been proven in many but not all cases. Although high-risk individuals generally can be identified, most of the potential victim pool is still unknown and cannot be discovered at this time. Awareness of these entities' existence, knowledge of family history, and 12-lead electrocardiography are the initial steps toward preventing SCD in this population. Underlying mechanisms for ventricular tachycardia/fibrillation in such individuals include phase 2 reentry, early after depolarization, and vortex reentry. For the time-being, although most forms of long QT syndrome can be treated with β-blockers, an implantable cardioverter-defibrillator remains the only definitive therapy for the prevention of arrhythmic death among high-risk populations.

Specificity of elevated intercostal space ECG recording for the type 1 Brugada ECG pattern

BACKGROUND

Right precordial (V1-3) elevated electrode placement ECG (EEP-ECG) is often used in the diagnosis of Brugada syndrome (BrS). However, the specificity of this has only been studied in smaller studies in Asian populations. We aimed to study this in a larger European population.

METHODS

Two different populations consisting of healthy subjects were used. A total of 340 subjects were included, 80% were men, the median age was 43 year (interquartile range: 31-51) and all were of European ethnicity.

RESULTS

No type 1 ECG patterns were identified but 16 (4.7%) subjects with a type 2 ECG and 32 (9.4%) subjects with a type 3 ECG were identified in any lead placement. In total 43 (13%) subjects had any BrS ECG pattern in any lead placement. The specificity was 100% (one-sided 97.5% CI: 99%) for the use of EEP-ECG to uncover type 1 pattern. For type 2 pattern the specificity was 95% (95% CI: 92-97%) and for type 3 pattern 91% (95% CI: 88-94%).

CONCLUSIONS

Elevated electrode placement ECG in the diagnosis of BrS seems to have a very high specificity with regards to the finding of a type 1 ECG pattern in a European population; conversely a finding of a type 2 or 3 pattern is of a significantly lower specificity and should perhaps be disregarded.

Prevalence of the type 1 Brugada electrocardiogram in Caucasian patients with suspected coronary spasm

AIMS

Sporadic cases have reported the coexistence of coronary spasm and Brugada syndrome. However, the prevalence of the Brugada phenotype in coronary spasm is unknown, particularly in non-Japanese populations. In this study, we sought to examine the prevalence of the type 1 Brugada electrocardiogram (ECG) in a large European patient population undergoing intracoronary provocation testing for suspected coronary spasm.

METHODS AND RESULTS

We retrospectively evaluated ECG data for the presence of type 1, 2, and 3 Brugada ECGs from 955 consecutive German patients without obstructive coronary artery disease undergoing intracoronary acetylcholine (ACH) provocation (ACH-test). Eight hundred and twenty-seven patients (age 63 ± 12 years; 42% male) with complete ECG data were eligible for further analysis. The ACH-test revealed coronary spasm in 325 patients (39.3%). A Brugada ECG of any type was found in six patients (0.7%) at baseline and eight patients (0.9%) at any time. There was no difference in the prevalence of coronary spasm in patients with (37.5%) and without (39.3%) Brugada-type ECGs. The type 1 Brugada ECG was not seen at baseline, but two type 1 Brugada ECGs were observed during ACH-administration into the right coronary artery (RCA; 0.2%), one with simultaneous RCA spasm and one without. Ajmaline provocation testing reproduced the type-1 Brugada ECG in the patient without coronary spasm but she had no other features of the Brugada syndrome.

CONCLUSIONS

This study reports a low prevalence of the type 1 Brugada ECG in the largest known European collection of intracoronary ACH provocation. In these patients, we found no evidence for the coexistence of Brugada syndrome and coronary spasm. This is in contrast to available Japanese data.

Prevalence of Brugada-type ECG pattern and early ventricular repolarization pattern in Tunisian athletes

INTRODUCTION

No data regarding the prevalence of the Brugada-type electrocardiogram (ECG) pattern and the early ventricular repolarization pattern (ERP) in the North African population were available. The aims of this study were to determine the frequency of Brugada-type ECG pattern and ERP in Tunisia and to evaluate ECG descriptors of ventricular repolarization in a population of athletes.

METHODS

Over a 2-year period, resting 12-lead ECG recordings were analyzed from athletes (n = 540; 348 males; age 18.3 ± 2.4 years). Brugada-type ECG pattern was defined as Type 1, 2, or 3, and ERP was characterized by an elevation of the J point in the inferior and/or lateral leads. The population was divided into three groups of athletes: ERP group; Brugada-type ECG pattern group; and control group, with neither ERP nor Brugada ECG pattern. Clinical and electrocardiographic parameters were compared among the study groups.

RESULTS

Nine subjects (1.66%) had a Brugada-type ECG pattern. None of them had the coved-type, 3 (0.6%) had the Type 2, and 6 (1.1%) had the Type 3. All subjects were asymptomatic. A Brugada-type ECG pattern was observed in seven males. No female had the Type 2 Brugada ECG pattern. ECG parameters were similar among Brugada-type ECG pattern and control athletes. ERP (119 subjects, 22%) was obtained in 98 males. Heart rate was lower, the QRS duration shorter and QT and Tpeak-Tend intervals were longer in ERP than control groups.

CONCLUSION

The results indicate that the frequency of the Brugada-type ECG pattern and ERP were respectively 1.66% and 22.00% in athletes, being more prevalent in males. The ERP group experienced shorter QRS duration and longer Tpeak-Tend interval than in the control population.

Brugada Syndrome 2010

The Brugada syndrome is a genetically determined cardiac disorder, presenting with characteristic electrocardiogram features and high risk of sudden cardiac death from polymorphic ventricular tachycardia/ventricular fibrillation in young individuals with a structurally normal heart. Scientific knowledge about the disease has grown exponentially in recent years. Two consensus reports on the disease were published (in 2002 and 2005) in an effort to state diagnostic criteria, risk stratification, and treatment indications. However, substantial controversies remain, especially considering risk stratification of asymptomatic patients. Given the enormous amount of valuable information collected by many groups since the consensus reports, current diagnostic criteria, recommended prognostic tools, and treatment must be reviewed. This article briefly reviews recent advances in understanding of Brugada syndrome and its genetic and molecular basis, arrhythmogenic mechanisms, and clinical course. An update of tools for risk stratification and treatment of the condition is also included.

The prevalence and relevance of the Brugada-type electrocardiogram in the Danish general population: data from the Copenhagen City Heart Study

AIMS

The prevalence of the Brugada-type electrocardiogram (ECG) in the Danish population is not known.

METHODS AND RESULTS

Inhabitants from the city of Copenhagen, Denmark, have participated in a prospective study since 1976. Four cross-sectional surveys have been carried out. Follow-up was performed using public registers. At each examination, the participants had an ECG registered. ECGs, showing right bundle branch block (RBBB) were examined for a possible Brugada-type pattern. A total of 42,560 ECGs had been registered from 18,974 participants. 1,284 had been coded as RBBB. Among these ECGs, we found no ECGs showing type 1 Brugada pattern, and 14 showing type 2 or 3 pattern. The prevalence of the total number of ECGs with Brugada pattern was 7/10,000. None of the subjects with a Brugada-pattern ECG died suddenly during follow-up.

CONCLUSION

The Brugada-type ECG pattern is rare in the general Danish population. None of the subjects with a Brugada-type ECG died suddenly during a follow-up of 6-33 years.