Event rates and risk factors in patients with Brugada syndrome and no prior cardiac arrest: a cumulative analysis of the largest available studies distinguishing ICD-recorded fast ventricular arrhythmias and sudden death

Exercise in the Genetic Arrhythmia Syndromes - A Review

Provide a brief summary of your article (100-150 words; no references or figures/tables). The synopsis appears only in the table of contents and is often used by indexing services such as PubMed. Genetic arrhythmia syndromes are rare, yet harbor the potential for highly consequential, often unpredictable arrhythmias or sudden death events. There has been historical uncertainty regarding the correct advice to offer to affected patients who are reasonably wanting to participate in sporting and athletic endeavors. In some cases, this had led to abundantly cautious disqualifications, depriving individuals from participation unnecessarily. Societal guidance and expert opinion has evolved significantly over the last decade or 2, along with our understanding of the genetics and natural history of these conditions, and the emphasis has switched toward shared decision making with respect to the decision to participate or not, with patients and families becoming better informed, and willing participants in the decision making process. This review aims to give a brief update of the salient issues for the busy physician concerning these syndromes and to provide a framework for approaching their management in the otherwise aspirational or keen sports participant.

A Multicenter External Validation of a Score Model to Predict Risk of Events in Patients With Brugada Syndrome

A multivariate risk score model was proposed by Sieira et al in 2017 for sudden death in Brugada syndrome; their validation in 150 patients was highly encouraging, with a C-index of 0.81; however, this score is yet to be validated by an independent group. A total of 192 records of patients with Brugada syndrome were collected from 2 centers in the United Kingdom and retrospectively scored according to a score model by Sieira et al. Data were compiled summatively over follow-up to mimic regular risk re-evaluation as per current guidelines. Sudden cardiac death survivor data were considered perievent to ascertain the utility of the score before cardiac arrest. Scores were compared with actual outcomes. Sensitivity in our cohort was 22.7%, specificity was 57.6%, and C-index was 0.58. In conclusion, up to 75% of cardiac arrest survivors in this cohort would not have been offered a defibrillator if evaluated before their event. This casts doubt on the utility of the score model for primary prevention of sudden death. Inherent issues with modern risk scoring strategies decrease the likelihood of success even in robustly designed tools such as the Sieira score model.

Brugada syndrome and syncope: a practical approach for diagnosis and treatment

Syncope in patients with Brugada electrocardiogram pattern may represent a conundrum in the decision algorithm because incidental benign forms, especially neurally mediated syncope, are very frequent in this syndrome similarly to the general population. Arrhythmic syncope in Brugada syndrome typically results from a self-terminating sustained ventricular tachycardia or paroxysmal ventricular fibrillation, potentially leading to sudden cardiac death. Distinguishing syncope due to malignant arrhythmias from a benign form is often difficult unless an electrocardiogram is recorded during the episode. We performed a review of the existing literature and propose a practical approach for diagnosis and treatment of the patients with Brugada syndrome and syncope.

Dynamic changes in ventricular depolarization during exercise in patients with Brugada syndrome

Brugada syndrome (BS) is a genetic pathological condition associated with a high risk for sudden cardiac death (SCD). Ventricular depolarization disorders have been suggested as a potential electrophysiological mechanism associated with high SCD risk on patients with BS. This paper aims to characterize the dynamic changes of ventricular depolarization observed during physical exercise in symptomatic and asymptomatic BS patients. To this end, cardiac ventricular depolarization features were automatically extracted from 12-lead ECG recordings acquired during standardized exercise stress test in 110 BS patients, of whom 25 were symptomatic. Conventional parameters were evaluated, including QRS duration, R and S wave amplitudes (AR, AS), as well as QRS morphological features, such as up-stroke and down-stroke slopes of the R and S waves (UR, DR and US). The effects of physical exercise and recovery on the dynamics of these markers were assessed in both BS populations. Features showing significantly different dynamics between the studied groups were used alone and in combination with the clinical characteristics of the patients in a logistic regression analysis. Results show larger changes in the second half of the QRS complex through AS and US measured in the right precordial leads for asymptomatic patients, especially during recovery, when the vagal tone is more pronounced. Multivariate analysis involving both types of features resulted in a reduced model of three relevant features (ΔAS in lead V2, Sex and heart rate recovery, HRR), which achieved a suitable discrimination performance between groups; sensitivity = 80% and specificity = 75% (AUC = 83%). However, after controlling the model for possible confounding factors, only one feature (ΔAS) remained meaningful. This adjusted model significantly improved the overall discrimination performance by up to: sensitivity = 84% and specificity = 100% (AUC = 94%). The study highlights the importance of physical exercise test to unmask differentiated behaviors between symptomatic and asymptomatic BS patients through depolarization dynamic analysis. This analysis together with the obtained model may help to identify asymptomatic patients at low or high risk of future cardiac events, but it should be confirmed by further prospective studies.

Clinical outcome of patients with the Brugada type 1 electrocardiogram without prophylactic implantable cardioverter defibrillator in primary prevention: a cumulative analysis of seven large prospective studies

Aims

Patients with the Brugada type 1 ECG (Br type 1) without previous aborted sudden death (aSD) who do not have a prophylactic ICD constitute a very large population whose outcome is little known. The objective of this study was to evaluate the risk of SD or aborted SD (aSD) in these patients.

Methods and results

We conducted a meta-analysis and cumulative analysis of seven large prospective studies involving 1568 patients who had not received a prophylactic ICD in primary prevention. Patients proved to be heterogeneous. Many were theoretically at low risk, in that they had a drug-induced Br type 1 (48%) and/or were asymptomatic (87%), Others, in contrast, had one or more risk factors. During a mean/median follow-up ranging from 30 to 48 months, 23 patients suffered SD and 1 had aSD. The annual incidence of SD/aSD was 0.5% in the total population, 0.9% in patients with spontaneous Br type 1 and 0.08% in those with drug-induced Br type 1 (P = 0.0001). The paper by Brugada et al. reported an incidence of SD more than six times higher than the other studies, probably as a result of selection bias. On excluding this paper, the annual incidence of SD/aSD in the remaining 1198 patients fell to 0.22% in the total population and to 0.38 and 0.06% in spontaneous and drug-induced Br type 1, respectively. Of the 24 patients with SD/aSD, 96% were males, the mean age was 39 ± 15 years, 92% had spontaneous Br type 1, 61% had familial SD (f-SD), and only 18.2% had a previous syncope; 43% had a positive electrophysiological study. Multiple meta-analysis of individual trials showed that spontaneous Br type 1, f-SD, and previous syncope increased the risk of SD/aSD (RR 2.83, 2.49, and 3.03, respectively). However, each of these three risk factors had a very low positive predictive value (PPV) (1.9-3.3%), while negative predictive values (NPV) were high (98.5-99.7%). The incidence of SD/aSD was only slightly higher in patients with syncope than in asymptomatic patients (2% vs. 1.5%, P = 0.6124). Patients with SD/aSD when compared with the others had a mean of 1.74 vs. 0.95 risk factors (P = 0.026).

Conclusion

(i) In patients with Br type 1 ECG without an ICD in primary prevention, the risk of SD/aSD is low, particularly in those with drug-induced Br type 1; (ii) spontaneous Br type 1, f-SD, and syncope increase the risk. However, each of these risk factors individually has limited clinical usefulness, owing to their very low PPV; (iii) patients at highest risk are those with more than one risk factor.

A Case of Type I and II Brugada Phenocopy Unmasked in a Patient with Normal Baseline Electrocardiogram (ECG)

BACKGROUND Brugada pattern on electrocardiogram (ECG) is seen when there are at least 2 mm J-point elevation and 1 mm ST-segment elevation in two or more of the right precordial leads, with right bundle-branch block (RBBB)-like morphology. Elevation of a coved-type shape in leads V1 and V2 is consistent with type I Brugada pattern, whereas elevation of a saddle-back configuration distinguishes type II Brugada. If accompanied by life-threatening arrhythmias or sudden cardiac death, Brugada syndrome (BrS) is diagnosed. The presence of Brugada ECG pattern in absence of the syndrome has come to be known as Brugada phenocopy (BrP). CASE REPORT We introduce a case of both Brugada type I and II patterns unmasked in a 28-year-old female with fever secondary to mastitis. Though fever-induced BrP is a universally known phenomenon, the presentation of both type I and II patterns presenting in a patient during a single hospitalization makes this case unique from others. The patient was brought to the emergency department after experiencing a syncopal episode that appeared classically vasovagal in nature. Once her fever resolved, her baseline ECG showed no abnormalities. CONCLUSIONS Though Brugada ECG pattern may be very alarming, especially after syncope, appropriate management in the case of a fever-induced event would consist of observation with cardiac monitoring, immediate treatment of fever with antipyretics, and antibiotics for suspected infection. Close follow-up by a cardiologist as an outpatient is imperative to further ascertain if the patient is at high risk of life-threatening arrhythmias, significant for BrS.

Brugada type 1 electrocardiogram: Should we treat the electrocardiogram or the patient?

Patients with a Brugada type 1 electrocardiogram (ECG) pattern may suffer sudden cardiac death (SCD). Recognized risk factors are spontaneous type 1 ECG and syncope of presumed arrhythmic origin. Familial sudden cardiac death (f-SCD) is not a recognized independent risk factor. Finally, positive electrophysiologic study (+EPS) has a controversial prognostic value. Current ESC guidelines recommend implantable cardioverter defibrillator (ICD) implantation in patients with a Brugada type 1 ECG pattern if they have suffered a previous resuscitated cardiac arrest (class I recommendation) or if they have syncope of presumed cardiac origin (class IIa recommendation). In clinical practice, however, many other patients undergo ICD implantation despite the suggestions of the guidelines. In a 2014 cumulative analysis of the largest available studies (including over 2000 patients), we found that 1/3 of patients received an ICD in primary prevention. Interestingly, 55% of these latter were asymptomatic, while 80% had a + EPS. This means that over 30% of subjects with a Brugada type 1 ECG pattern were considered at high risk of SCD mainly on the basis of EPS, to which a class IIb indication for ICD is assigned by the current ESC guidelines. Follow-up data confirm that in clinical practice single, and often frail, risk factors overestimate the real risk in subjects with the Brugada type 1 ECG pattern. We can argue that, in clinical practice, many cardiology centers adopt an aggressive treatment in subjects with a Brugada type 1 ECG pattern who are not at high risk. As a result, many healthy persons may be treated in order to save a few patients with a true Brugada Syndrome. Better risk stratification is needed. A multi-parametric approach that considers the contemporary presence of multiple risk factors is a promising one.

Genotype-Phenotype Correlation of SCN5A Mutation for the Clinical and Electrocardiographic Characteristics of Probands With Brugada Syndrome

Background:

The genotype-phenotype correlation of SCN5A mutations as a predictor of cardiac events in Brugada syndrome remains controversial. We aimed to establish a registry limited to probands, with a long follow-up period, so that the genotype-phenotype correlation of SCN5A mutations in Brugada syndrome can be examined without patient selection bias.

Methods:

This multicenter registry enrolled 415 probands (n=403; men, 97%; age, 46±14 years) diagnosed with Brugada syndrome whose SCN5A gene was analyzed for mutations.

Results:

During a mean follow-up period of 72 months, the overall cardiac event rate was 2.5%/y. In comparison with probands without mutations ( SCN5A (–), n=355), probands with SCN5A mutations ( SCN5A (+), n=60) experienced their first cardiac event at a younger age (34 versus 42 years, P =0.013), had a higher positive rate of late potentials (89% versus 73%, P =0.016), exhibited longer P-wave, PQ, and QRS durations, and had a higher rate of cardiac events ( P =0.017 by log-rank). Multivariate analysis indicated that only SCN5A mutation and history of aborted cardiac arrest were significant predictors of cardiac events ( SCN5A (+) versus SCN5A (–): hazard ratio, 2.0 and P =0.045; history of aborted cardiac arrest versus no such history: hazard ratio, 6.5 and P <0.001).

Conclusions:

Brugada syndrome patients with SCN5A mutations exhibit more conduction abnormalities on ECG and have higher risk for cardiac events.

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.

Genetics of inherited primary arrhythmia disorders

A sudden unexplained death is felt to be due to a primary arrhythmic disorder when no structural heart disease is found on autopsy, and there is no preceding documentation of heart disease. In these cases, death is presumed to be secondary to a lethal and potentially heritable abnormality of cardiac ion channel function. These channelopathies include congenital long QT syndrome, catecholaminergic polymorphic ventricular tachycardia, Brugada syndrome, and short QT syndrome. In certain cases, genetic testing may have an important role in supporting a diagnosis of a primary arrhythmia disorder, and can also provide prognostic information, but by far the greatest strength of genetic testing lies in the screening of family members, who may be at risk. The purpose of this review is to describe the basic genetic and molecular pathophysiology of the primary inherited arrhythmia disorders, and to outline a rational approach to genetic testing, management, and family screening.

Circulating heart-type fatty acid-binding protein levels predict ventricular fibrillation in Brugada syndrome

BACKGROUND

The association between ongoing myocardial damage and outcomes in patients with Brugada syndrome who had received an implantable cardioverter-defibrillator (ICD) is unclear.

METHODS

Consecutive patients with Brugada syndrome (n=31, 50±13 years) who had received an ICD were prospectively enrolled. Minor myocardial membrane injury [heart-type fatty acid-binding protein (H-FABP) >2.4ng/mL] and myofibrillar injury (troponin T >0.005ng/mL) were defined using receiver operating characteristic curves. Patients were followed for a median period of 5 years to an endpoint of appropriate ICD shock.

RESULTS

Myocardial membrane injury (29%) and myofibrillar injury (26%) were similarly prevalent among patients with Brugada syndrome who had received ICDs. Appropriate ICD shocks occurred in 19% of patients during the follow-up period. Multivariate Cox regression analysis showed that serum H-FABP level >2.4ng/mL, but not troponin T level, was an independent prognostic factor for appropriate ICD shock due to ventricular fibrillation [hazard ratio (HR) 25.2, 95% confidence interval (CI) 1.33-1686, p=0.03].

CONCLUSIONS

Evaluating myocardial damage using H-FABP may be a promising tool for predicting ventricular arrhythmia in patients with Brugada syndrome who have received ICDs.

Long-term prognosis in patients with Brugada syndrome based on Class II indication for implantable cardioverter-defibrillator in the HRS/EHRA/APHRS Expert Consensus Statement: multicenter study in Japan

BACKGROUND

The HRS/EHRA/APHRS Expert Consensus Statement for implantable cardioverter-defibrillator (ICD) in Brugada syndrome (BrS) has recently been published. However, the validity of the Class II indication for ICD in BrS patients is still unknown.

OBJECTIVE

The purpose of this study was to evaluate the validity of the Class II indication for ICD implantation in the Consensus Statement with a large Japanese cohort of BrS.

METHODS

Among 410 patients with BrS, a total of 213 consecutive BrS patients with the Class II indication for ICD implantation (mean age 53 ± 14 years, 199 men) were enrolled. Clinical outcomes were compared between patients with Class IIa (n = 66) and those with Class IIb (n = 147) indication according to the Consensus Statement.

RESULTS

The incidence of cardiac events (documented ventricular tachyarrhythmias or sudden cardiac death) during follow-up of 62 ± 34 months was significantly higher in patients with Class IIa (n = 8, 2.2% per year) than those with Class IIb indication (n = 4, 0.5% per year; P = .01).

CONCLUSION

We confirmed that Class IIa indication identified a group of patients with increased risk compared to Class IIb indication for ICD in the Consensus Statement of 2013. In patients with Class II indication, the combination of a history of syncope and spontaneous type 1 ECG may be an important factor in distinguishing intermediate- from low-risk patients with BrS in Japan.