Territory-wide cohort study of Brugada syndrome in Hong Kong: predictors of long-term outcomes using random survival forests and non-negative matrix factorisation

OBJECTIVES

Brugada syndrome (BrS) is an ion channelopathy that predisposes affected patients to spontaneous ventricular tachycardia/fibrillation (VT/VF) and sudden cardiac death. The aim of this study is to examine the predictive factors of spontaneous VT/VF.

METHODS

This was a territory-wide retrospective cohort study of patients diagnosed with BrS between 1997 and 2019. The primary outcome was spontaneous VT/VF. Cox regression was used to identify significant risk predictors. Non-linear interactions between variables (latent patterns) were extracted using non-negative matrix factorisation (NMF) and used as inputs into the random survival forest (RSF) model.

RESULTS

This study included 516 consecutive BrS patients (mean age of initial presentation=50±16 years, male=92%) with a median follow-up of 86 (IQR: 45-118) months. The cohort was divided into subgroups based on initial disease manifestation: asymptomatic (n=314), syncope (n=159) or VT/VF (n=41). Annualised event rates per person-year were 1.70%, 0.05% and 0.01% for the VT/VF, syncope and asymptomatic subgroups, respectively. Multivariate Cox regression analysis revealed initial presentation of VT/VF (HR=24.0, 95% CI=1.21 to 479, p=0.037) and SD of P-wave duration (HR=1.07, 95% CI=1.00 to 1.13, p=0.044) were significant predictors. The NMF-RSF showed the best predictive performance compared with RSF and Cox regression models (precision: 0.87 vs 0.83 vs. 0.76, recall: 0.89 vs. 0.85 vs 0.73, F1-score: 0.88 vs 0.84 vs 0.74).

CONCLUSIONS

Clinical history, electrocardiographic markers and investigation results provide important information for risk stratification. Machine learning techniques using NMF and RSF significantly improves overall risk stratification performance.

Prediction and Prevention of Sudden Death in the Brugada Syndrome

Sudden cardiac death (SCD) secondary to sudden cardiac arrest (SCA) is a leading cause of death in the United States, claiming over a quarter million lives annually, and is directly responsible for 50% of all cardiovascular mortality. Brugada Syndrome (BrS) is an arrhythmogenic cardiovascular channelopathy that predisposes asymptomatic patients who have no identified disease to a high-risk of SCD/SCA as their first cardiac event/disease manifestation. Limited progress has been made in risk prediction of SCA and SCD, with the greatest challenge being the ability to identify the small high-risk subgroups concealed within the larger general population. In conclusion, accurate identification of high-risk asymptomatic BrS patients (through multiparametric risk scores composed of reliable and validated unambiguous clinical variables and biomarkers) may hold utility in improving current SCD prediction algorithms, and the appropriate primary prevention therapy may prove valuable in reducing risk of sudden death for this patient population. This systematic review aims to comprehensively summarize qualitative evidence that explore proposed clinical, electrocardiographic, electrophysiological, and genetic markers for risk stratification of patients with BrS phenotype, and to discuss the best available contemporary evidence regarding therapeutic approach.

Clinical Differences in Japanese Patients Between Brugada Syndrome and Arrhythmogenic Right Ventricular Cardiomyopathy With Long-Term Follow-Up

Some Brugada syndrome (BrS) patients have been suspected of being in the initial state of arrhythmogenic right ventricular cardiomyopathy (ARVC). This study aimed to clarify the electrocardiographic (ECG) and clinical differences between BrS and ARVC in long-term follow-up (mean 11.9 ± 6.3 years). A total of 50 BrS and 65 ARVC patients with fatal ventricular tachyarrhythmia (VTA) were evaluated according to the revised Task Force Criteria for ARVC. Based on the current diagnostic criteria concerning electrocardiographic, repolarization abnormality was positive in 2.0% and 2.6% of BrS patients at baseline and follow-up, and depolarization abnormality was positive in 6.0% and 12.8% of BrS patients at baseline and follow-up, respectively. At baseline, none of the BrS patients were definitively diagnosed with ARVC. Considering patients' lives since birth, Kaplan-Meier analysis revealed that age at first VTA attack showed the same tendency between the groups (BrS: mean 42.2 ± 12.5 years old vs ARVC: mean 44.8 ± 13.7 years old, log-rank p = 0.123). Moreover, the incidence of VTA recurrence was similar between the groups during follow-up (log-rank p = 0.906). Incidence of sustained monomorphic ventricular tachycardia was significantly higher in ARVC than in BrS whereas the opposite was true for ventricular fibrillation (log-rank p <0.001 and p <0.001, respectively). None of the diagnoses of BrS patients were changed to ARVC during follow-up. During long-term follow-up, although age at first VTA attack and VTA recurrence were similar, BrS consistently exhibited features that differed from those of ARVC.

Reappraisal of Reported Genes for Sudden Arrhythmic Death: Evidence-Based Evaluation of Gene Validity for Brugada Syndrome

BACKGROUND

Implicit in the genetic evaluation of patients with suspected genetic diseases is the assumption that the genes evaluated are causative for the disease based on robust scientific and statistical evidence. However, in the past 20 years, considerable variability has existed in the study design and quality of evidence supporting reported gene-disease associations, raising concerns of the validity of many published disease-causing genes. Brugada syndrome (BrS) is an arrhythmia syndrome with a risk of sudden death. More than 20 genes have been reported to cause BrS and are assessed routinely on genetic testing panels in the absence of a systematic, evidence-based evaluation of the evidence supporting the causality of these genes.

METHODS

We evaluated the clinical validity of genes tested by diagnostic laboratories for BrS by assembling 3 gene curation teams. Using an evidence-based semiquantitative scoring system of genetic and experimental evidence for gene-disease associations, curation teams independently classified genes as demonstrating limited, moderate, strong, or definitive evidence for disease causation in BrS. The classification of curator teams was reviewed by a clinical domain expert panel that could modify the classifications based on their independent review and consensus.

RESULTS

Of 21 genes curated for clinical validity, biocurators classified only 1 gene ( SCN5A) as definitive evidence, whereas all other genes were classified as limited evidence. After comprehensive review by the clinical domain Expert panel, all 20 genes classified as limited evidence were reclassified as disputed with regard to any assertions of disease causality for BrS.

CONCLUSIONS

Our results contest the clinical validity of all but 1 gene clinically tested and reported to be associated with BrS. These findings warrant a systematic, evidence-based evaluation for reported gene-disease associations before use in patient care.

A balanced translocation disrupting SCN5A in a family with Brugada syndrome and sudden cardiac death

BACKGROUND

Brugada syndrome (BrS) is a primary arrhythmia syndrome affecting 1 in 2000 of the general population. Genetic testing identifies pathogenic variants in the sodium voltage-gated channel α-subunit 5 gene (SCN5A) in up to 25% of familial BrS. Balanced translocations, which involve the exchange of the ends of 2 different chromosomes, are found in approximately 1 in 500 people. They usually are benign and only rarely are reported to cause arrhythmogenic disorders.

OBJECTIVE

The purpose of this study was to identify the genetic mechanism underlying a family with BrS, sick sinus syndrome, cardiac hypertrophy, sudden cardiac death, and multiple miscarriages.

METHODS

We clinically evaluated family members with an electrocardiogram, 2-dimensional echocardiogram, and provocation testing with ajmaline challenge. Cytogenetic testing included karyotype and fluorescent in situ hybridization (FISH) analysis. We performed gene panel, exome, and genome sequencing analysis.

RESULTS

Sequencing of 128 cardiac genes and exome sequencing of a family with BrS, sick sinus syndrome, cardiac hypertrophy, sudden cardiac death, and multiple miscarriages did not reveal a pathogenic variant. Karyotype and FISH analysis identified a balanced translocation breaking the SCN5A gene on chromosome 3 and the multiple chromosome maintenance 10 gene (MCM10) on chromosome 10 t(3;10)(p22.2;p13). We characterized both translocation breakpoint junctions using genome sequencing and found no regions of sequence homology.

CONCLUSION

A balanced translocation breaking SCN5A is a novel mechanism underlying disease in a family with BrS, sick sinus syndrome, cardiac hypertrophy, and sudden cardiac death. Genome sequencing can identify rare chromosomal aberrations causing inherited diseases that may otherwise be missed using gene panel and exome sequencing-based approaches.

IDENTIFYING NEW SUDDEN DEATH GENES

Inherited conditions that lead to cardiac arrhythmias and sudden cardiac death remain an important cause of morbidity and mortality. Identifying the genes responsible for these rare conditions can provide insights into the more common and heritable forms of sudden cardiac death seen in patients with structural heart disease. We and others have used candidate gene approaches and positional cloning in large families to show that mutations in ion channels and ion channel related proteins cause familial arrhythmia syndromes including long QT and Brugada syndromes. The genes responsible for many familial arrhythmia syndromes and the vast majority of the predisposition to common arrhythmias remain unknown. Using whole exome sequencing in families with Brugada syndrome and idiopathic ventricular fibrillation, we now seek to identify mutations in genes previously not thought to play a significant role in the heart.

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.

A meta-analytic review of prevalence for Brugada ECG patterns and the risk for death

BACKGROUND

The prevalence of Brugada ECG pattern (BrEP) is different in different regions, and its mean prevalence over the world is unknown. The risk of people with BrEP for death remains unknown. We performed a meta-analysis to determine the prevalence of BrEP and risk ratio (RR) for death.

METHODS

Relevant studies published between July 1, 2000 and August 20, 2016, which contain prevalence and RR for all-cause death and cardiac death, were included. The prevalence and RR are analyzed using meta-analysis.

RESULTS

We finally retrieved 24 studies of the prevalence for BrEP and 5 studies of the RR for all-cause death and cardiac death. The worldwide mean prevalence of BrEP is 0.4%, with highest in Asia (0.9%) and lowest in North America (0.2%). Additionally, the mean prevalence in male is 0.9%, whereas it is 0.1% in female. The RR of BrEP for all-cause death is 0.78 (95% confidence interval 0.45-1.37), and for cardiac death it is 0.92 (95% confidence interval 0.23-3.66).

CONCLUSION

The prevalence of BrEP is about 0.4% around the world with different prevalence in region and sex. Our study shows that BrEP may not be taken as a predictor of all-cause death and cardiac death.

Surveillance after cardiac arrest in patients with Brugada syndrome without an implantable defibrillator: An alarm effect of the previous syncope

BACKGROUND

Debate regarding the prognosis of asymptomatic patients with Brugada syndrome (BrS) is possibly affected by the selection bias of survivors of sudden cardiac arrest (SCA). We aimed to determine variables influencing surveillance after SCA.

METHODS

We analyzed a BrS cohort of 145 patients belonging to 37 families. We compared the clinical data and circumstances surrounding SCA (i.e., place of occurrence and people accompanying the subject) in 10 patients who survived an episode of SCA (Group A) vs. 27 deceased relatives (first or second degree) who suffered sudden cardiac death (SCD; Group B). Information concerning Group B was agreed upon by at least 3 relatives. A sub-analysis was performed considering families carrying a mutation in SCN5A (Group B-Mutant).

RESULTS

Syncope was unique in predicting SCA in the BrS cohort. Comparing Groups A vs. B, there were no differences in the mean age at time of SCA/SCD (46.2 [SD 17.1] vs. 39.9 [SD 14.5] years; p=0.271), gender (male 60% vs. 74.1%; p=0.442), prior cardiomyopathy (0%), administration of cardiovascular treatments (anti-hypertensive and lipid-lowering drugs; 20% vs. 14.8%; p=0.653) or conventional cardiovascular risk factors. Environmental circumstances surrounding the SCA/SCD were not significantly different between groups. Prior syncope was more frequent in Group A (80% vs. 3.7%; p<0.001) and unique in predicting surveillance (p<0.001). Group B-Mutant displayed equivalent data.

CONCLUSIONS

A previous syncope, as an alarm symptom, might contribute to better surveillance of SCA compared with subjects with SCA as the debut of BrS. The latter might behave as a factor of selection bias.

Brugada Syndrome: An Electrical Storm without Warning

Brugada Syndrome (BrS) is an inherited channelopathy causing sodium channel dysfunction in cardiac myocyte. These patients are prone to develop Ventricular Fibrillation (VF) or polymorphic Ventricular Tachycardia (VT). Next to coronary artery disease and cardiomyopathies, BrS is an important cause of sudden cardiac death. We report here a case of 22 year unmarried female with "unexplained" cardiac arrest without prior history of syncope and family history of sudden cardiac death. She was resuscitated out of hospital in some local dispensary in rural settings and after prolonged hypoxia with its neurological sequelae, she eventually died. BrS should be considered in differentials of unexplained cardiac arrest even in patients without family history of sudden cardiac death. First episode of VT/VF in BrS patients can be life threatening. Only prompt cardioversion / defibrillation can save life. We have suggested some measures to identify patients of BrS.

Syncope in Brugada syndrome: prevalence, clinical significance, and clues from history taking to distinguish arrhythmic from nonarrhythmic causes

BACKGROUND

Syncope in Brugada syndrome (BrS) patients is a sign of increased risk for sudden cardiac death and usually is ascribed to cardiac arrhythmias. However, syncope often occurs in the general population, mostly from nonarrhythmic causes (eg, reflex syncope).

OBJECTIVE

The purpose of this study was to distinguish arrhythmic events from nonarrhythmic syncope in BrS and to establish the clinical relevance of nonarrhythmic syncope.

METHODS

We reviewed the patient records of 342 consecutively included BrS patients and conducted systematic interviews in 141 patients with aborted cardiac arrest (ACA) or syncope.

RESULTS

In total, 23 patients (7%) experienced ECG-documented ACA and 118 (34%) syncope; of these 118, 67 (57%) were diagnosed with suspected nonarrhythmic syncope. Compared to suspected nonarrhythmic syncope patients, ACA patients were older at first event (45 vs 20 years), were more likely to be male (relative risk 2.1) and to have urinary incontinence (relative risk 4.6), and were less likely to report prodromes. ACA was never triggered by hot/crowded surroundings, pain or other emotional stress, seeing blood, or prolonged standing. During follow-up (median 54 months), ACA rate was 8.7% per year among ACA patients and 0% per year among suspected nonarrhythmic syncope patients.

CONCLUSION

Syncope, especially nonarrhythmic syncope, often occurs in BrS. The high incidence of nonarrhythmic syncope must be taken into account during risk stratification. Arrhythmic events and nonarrhythmic syncope may be distinguished by clinical characteristics (absence of prodromes and, particularly, specific triggers), demonstrating the importance of systematic history taking.

Genetic and forensic implications in epilepsy and cardiac arrhythmias: a case series

Epilepsy affects approximately 3% of the world's population, and sudden death is a significant cause of death in this population. Sudden unexpected death in epilepsy (SUDEP) accounts for up to 17% of all these cases, which increases the rate of sudden death by 24-fold as compared to the general population. The underlying mechanisms are still not elucidated, but recent studies suggest the possibility that a common genetic channelopathy might contribute to both epilepsy and cardiac disease to increase the incidence of death via a lethal cardiac arrhythmia. We performed genetic testing in a large cohort of individuals with epilepsy and cardiac conduction disorders in order to identify genetic mutations that could play a role in the mechanism of sudden death. Putative pathogenic disease-causing mutations in genes encoding cardiac ion channel were detected in 24% of unrelated individuals with epilepsy. Segregation analysis through genetic screening of the available family members and functional studies are crucial tasks to understand and to prove the possible pathogenicity of the variant, but in our cohort, only two families were available. Despite further research should be performed to clarify the mechanism of coexistence of both clinical conditions, genetic analysis, applied also in post-mortem setting, could be very useful to identify genetic factors that predispose epileptic patients to sudden death, helping to prevent sudden death in patients with epilepsy.

Sudden unexplained death in infants and children: the role of undiagnosed inherited cardiac conditions

Sudden unexplained death in childhood is a traumatic event for both the immediate family and medical professionals. This is termed sudden unexplained or arrhythmic death syndrome (SUDS/SADS) for children over 1 year of age while sudden unexplained death in infancy or sudden infant death syndrome (SUDI/SIDS) refers to unexplained deaths in the first year of life. There is increasing evidence for the role of undiagnosed inherited cardiac conditions, particularly channelopathies, as the cause of these deaths. This has far-reaching implications for the family regarding the potential risk to other family members and future pregnancies, providing a challenge not only in the counselling but also in the structured assessment and management of immediate relatives. This review will discuss the cardiac risk involved in sudden unexplained deaths of infants and children, the role of molecular autopsy, family cardiological screening, current management strategies, and future directions in this area.

Outcome after implantation of a cardioverter-defibrillator in patients with Brugada syndrome: a multicenter study-part 2

BACKGROUND

Implantable cardioverter-defibrillator indications in Brugada syndrome remain controversial, especially in asymptomatic patients. Previous outcome data are limited by relatively small numbers of patients or short follow-up durations. We report the outcome of patients with Brugada syndrome implanted with an implantable cardioverter-defibrillator in a large multicenter registry.

METHODS AND RESULTS

A total of 378 patients (310 male; age, 46±13 years) with a type 1 Brugada ECG pattern implanted with an implantable cardioverter-defibrillator (31 for aborted sudden cardiac arrest, 181 for syncope, and 166 asymptomatic) were included. Fifteen patients (4%) were lost to follow-up. During a mean follow-up of 77±42 months, 7 patients (2%) died (1 as a result of an inappropriate shock), and 46 patients (12%) had appropriate device therapy (5±5 shocks per patient). Appropriate device therapy rates at 10 years were 48% for patients whose implantable cardioverter-defibrillator indication was aborted sudden cardiac arrest, 19% for those whose indication was syncope, and 12% for the patients who were asymptomatic at implantation. At 10 years, rates of inappropriate shock and lead failure were 37% and 29%, respectively. Inappropriate shock occurred in 91 patients (24%; 4±4 shocks per patient) because of lead failure (n=38), supraventricular tachycardia (n=20), T-wave oversensing (n=14), or sinus tachycardia (n=12). Importantly, introduction of remote monitoring, programming a high single ventricular fibrillation zone (>210-220 bpm), and a long detection time were associated with a reduced risk of inappropriate shock.

CONCLUSIONS

Appropriate therapies are more prevalent in symptomatic Brugada syndrome patients but are not insignificant in asymptomatic patients (1%/y). Optimal implantable cardioverter-defibrillator programming and follow-up dramatically reduce inappropriate shock. However, lead failure remains a major problem in this population.

Vulnerability of fourth ventricle choroid plexus in sudden unexplained fetal and infant death syndromes related to smoking mothers

The human choroid plexuses in the ventricular system represent the main source of cerebrospinal fluid secretion and constitute a major barrier interface that controls the brain's environment. The present study focused on the choroid plexus of the fourth ventricle, the main cavity of the brainstem containing important nuclei and/or structures mediating autonomic vital functions. In serial sections of 84 brainstems of subjects aged from 17 gestational weeks to 8 postnatal months of life, the deaths due to both known and unknown causes, we examined the cytoarchitecture and the developmental steps of the fourth ventricle choroid plexus to determine whether this structure shows morphological and/or functional alterations in unexplained perinatal deaths (Sudden Infant Death Syndrome and Sudden Intrauterine Unexplained Death Syndrome). High incidence of histological and immunohistochemical alterations (prevalence of epithelial dark cells, the presence of cystic cells in the stroma, decreased number of blood capillaries, hyperexpression of Substance P and apoptosis) were prevalently observed in unexplained death victims (p<0.05 vs. controls). A significant correlation was found between maternal smoking in pregnancy and choroidal neuropathological parameters (p<0.01). This work underscores the negative effects of prenatal exposure to nicotine on the development of the autonomic nervous system, and in particular of the fourth ventricle choroid plexus that is a very vulnerable structure in the developing CSF-brain system.

Brugada syndrome

As a clinical entity the Brugada syndrome has existed since 1992 and has been associated with a high risk of sudden cardiac death predominately in younger males. Patients can present with symptoms (ie syncope, palpitations, aborted sudden cardiac death) and asymptomatically. Its three characteristic electrocardiographic patterns can occur both spontaneously or after provocation with sodium channel-blocking agents. Risk stratification and the need for treatment depend on the patient's symptoms, electrocardiography, family history, and electrophysiological inducibility to discern if treatment by implantable cardioverter defibrillator, the only effective treatment to date, is appropriate. This review focuses on Brugada syndrome and various aspects of the disease including proposed mechanisms, epidemiology, clinical presentations, genetics, diagnosis, risk stratification, and treatment options.

Molecular genetics and functional anomalies in a series of 248 Brugada cases with 11 mutations in the TRPM4 channel

Brugada syndrome (BrS) is a condition defined by ST-segment alteration in right precordial leads and a risk of sudden death. Because BrS is often associated with right bundle branch block and the TRPM4 gene is involved in conduction blocks, we screened TRPM4 for anomalies in BrS cases. The DNA of 248 BrS cases with no SCN5A mutations were screened for TRPM4 mutations. Among this cohort, 20 patients had 11 TRPM4 mutations. Two mutations were previously associated with cardiac conduction blocks and 9 were new mutations (5 absent from ∼14′000 control alleles and 4 statistically more prevalent in this BrS cohort than in control alleles). In addition to Brugada, three patients had a bifascicular block and 2 had a complete right bundle branch block. Functional and biochemical studies of 4 selected mutants revealed that these mutations resulted in either a decreased expression (p.Pro779Arg and p.Lys914X) or an increased expression (p.Thr873Ile and p.Leu1075Pro) of TRPM4 channel. TRPM4 mutations account for about 6% of BrS. Consequences of these mutations are diverse on channel electrophysiological and cellular expression. Because of its effect on the resting membrane potential, reduction or increase of TRPM4 channel function may both reduce the availability of sodium channel and thus lead to BrS.

The prognostic value of early repolarization (J wave) and ST-segment morphology after J wave in Brugada syndrome: multicenter study in Japan

BACKGROUND

The prognostic value of a J wave and ST-segment morphology after J wave in inferolateral leads in Brugada syndrome (BS) is still unknown.

OBJECTIVE

To evaluate the prognostic value of a J wave and ST-segment morphology after J wave in a large Japanese cohort of BS.

METHODS

A total of 460 consecutive patients with BS (mean age 52±14 years, 432 men) were enrolled. The presence and location of leads showing a J wave, ST-segment morphology after J wave, and clinical outcomes were evaluated in patients with documented ventricular fibrillation (VF) (N = 84), those with syncope without documented VF (N = 109), and subjects without symptoms (N = 267).

RESULTS

The prevalence of a J wave in the inferior and/or lateral leads was 12% (53 cases). The prevalence of a J wave among the 3 groups was not different. The incidence of cardiac events (sudden cardiac death or VF) during a mean follow-up period of 50±32 months was not different in patients with (11%) or without (8%) a J wave. Patients with a J wave in both inferior and lateral leads or with horizontal ST-segment morphology after J wave showed a higher incidence of cardiac events than those without (P = .04 and .02, respectively). Multivariate analysis revealed symptoms, QRS duration in lead V2>90 ms, and inferolateral J wave and/or horizontal ST-segment morphology after J wave were important for predicting cardiac events.

CONCLUSION

The presence of a J wave in multiple leads and horizontal ST-segment morphology after J wave may indicate a highly arrhythmogenic substrate in patients with BS.

[Brugada syndrome: diagnosis and risk stratification]

Brugada syndrome is a genetic disease, leading to a functional reduction in sodium channel current. This anomaly occurs in the absence of other demonstrable cardiac anomalies. The ECG diagnostic pattern is characterized by coved ST-segment elevation in V1-V3 leads. Brugada syndrome may be complicated by malignant ventricular arrhythmias and sudden death. Risk stratification in individuals with type 1 Brugada ECG pattern for primary prevention of sudden death is an unsolved issue. Recognized risk factors for sudden death are spontaneous type 1 ECG pattern, syncope, or documented cardiac arrest. Family history of sudden death is a controversial risk factor. However, all these factors have a low positive predictive value. The prognostic significance of electrophysiological study (EPS) is debated. There is a consensus about the low predictive value of a positive EPS and a low specificity. However, while some authors deny at all its usefulness, others suggest that EPS is useful when considered together with other clinical risk factors. According to Brugada brothers our personal data suggest that (i) in subjects with type 1 Brugada ECG no single clinical risk factor nor EPS alone are able to identify subjects at the highest risk; (ii) a multiparametric approach (including syncope, family history of sudden death and positive EPS) helps to identify populations at the highest risk; (iii) subjects at the highest risk are those with a spontaneous type 1 ECG and at least two risk factors; (iv) the remaining are at low risk.

Current review of Brugada syndrome: from epidemiology to treatment

Brugada syndrome is a genetic cause of sudden cardiac arrest characterized by abnormal electrocardiographic (ECG) pattern in the right precordial leads either at rest or after provocation. In this condition, sudden death may occur due to polymorphic ventricular tachycardia or ventricular fibrillation. In approximately 30% of patients, sudden cardiac arrest is the initial clinical manifestation of Brugada syndrome. Treatment strategies for Brugada syndrome are evolving. Currently, the implanted cardioverter defibrillator (ICD) is the only proven treatment for Brugada syndrome. Candidates for ICD include patients include those with the type 1 ECG pattern or who have been successfully resuscitated from sudden death or have had unexplained syncope.

Electrical heart disease: Genetic and molecular basis of cardiac arrhythmias in normal structural hearts

Purely electrical heart diseases, defined by the absence of any structural cardiac defects, are responsible for a large number of sudden, unexpected deaths in otherwise healthy, young individuals. These conditions include the long QT syndrome, Brugada syndrome, catecholaminergic polymorphic ventricular tachycardia and the short QT syndrome. Collectively, these conditions have been referred to as channelopathies. Ion channels provide the molecular basis for cardiac electrical activity. These channels have specific ion selectivity and are responsible for the precise and timely regulation of the passage of charged ions across the cell membrane in myocytes, and the summation of their activity in cardiac muscle defines the surface electrocardiogram. Impairment in the flow of these ions in heart cells may mean the difference between a normal, prosperous life and the tragedy of a sudden, unexpected death due to ventricular arrhythmia. The present paper reviews the current clinical and molecular understanding of the electrical diseases of the heart associated with sudden cardiac death.

Clinical characteristics and risk stratification in symptomatic and asymptomatic patients with brugada syndrome: multicenter study in Japan

BACKGROUND

Neither the clinical characteristics nor risk stratification in Brugada syndrome have been clearly determined. We compared the clinical and ECG characteristics of symptomatic and asymptomatic patients with Brugada syndrome to identify new markers for high-risk patients.

METHODS

A total of 188 consecutive individuals with Brugada syndrome (mean age 53 +/- 14 years, 178 males) were enrolled in the Japan Idiopathic Ventricular Fibrillation Study (J-IVFS). Clinical and ECG characteristics were evaluated in three groups of patients: Ventricular fibrillation (VF) group: patients with documented VF (N = 33); Syncope (Sy) group: patients with syncope without documented VF (N = 57); and asymptomatic (As) group: subjects without symptoms (N = 98). Their prognostic parameters were evaluated over a 3-year follow-up period.

RESULTS

(1) Clinical characteristics: incidence of past history of atrial fibrillation (AF) was significantly higher in the VF and Sy groups than in the AS group (P = 0.04). (2) On 12-lead ECG, r-J interval in lead V2 and QRS duration in lead V6 were longest in the VF group (P = 0.001, 0.002, respectively). (3) Clinical follow-up: during a mean follow-up period of 37 +/- 16 months, incidences of cardiac events (sudden death and/or VF) were higher in the symptomatic (VF/Sy) groups than in the As group (P < 0.0001). The r-J interval in lead V2 >/= 90 ms and QRS duration in lead V6 >/= 90 ms were found to be possible predictors of recurrence of cardiac events in symptomatic patients.

CONCLUSIONS

Prolonged QRS duration in precordial leads was prominent in symptomatic patients. This ECG marker may be useful for distinguishing high- from low-risk patients with Brugada syndrome.

Role of programmed ventricular stimulation in patients with Brugada syndrome: a meta-analysis of worldwide published data

AIMS

Brugada syndrome (BS) is an ion channelopathy with the risk of sudden cardiac death. The role of programmed ventricular stimulation (PVS) in risk stratification has been controversially discussed. Therefore, we performed a meta-analysis on the prognostic role of PVS in BS.

METHODS AND RESULTS

A Medline search until July 2006 documented 822 entries for BS. Only English publications with > 10 patients and a follow-up period were considered (n = 15). Patients [n = 1217; 974 males (80%)] were divided into three groups: survived sudden cardiac arrest (SCA) [n = 222 (18%)], syncope (Syncope) [n = 275 (23%)], and asymptomatic patients (Asympt) [n = 720 (59%)]. PVS was conducted in 1036 patients (85%). In 548 patients (53%), sustained ventricular tachyarrhythmias (VT) or ventricular fibrillation (VF) was inducible. During follow-up (34 +/- 40 months), VT/VF occurred in 141 patients. SCA bore the highest chance for a VT/VF occurrence during follow-up [odds ratio (OR) 14.4 compared with asymptomatic patients; P < 0.0005]. However, except for one study, the OR for VT/VF during follow-up in relation to VT/VF inducibility was non-significant (OR 1.5; P = ns).

CONCLUSION

The main finding is that we were unable to identify a significant role of PVS with regard to arrhythmic events during follow-up in BS, thus questioning the role of PVS for risk stratification in patients with BS. Patients with BS and survived SCA show the highest chance for VT/VF occurrence during follow-up.