Prevalence, clinical characteristics and management of atrial fibrillation in patients with Brugada syndrome

Prevalence and Clinical Significance of Latent Brugada Syndrome in Atrial Fibrillation Patients Below 45 Years of Age

Aim: This study aims to describe prevalence and clinical significance of latent Brugada syndrome (BrS) in a young population with atrial fibrillation (AF).

Methods: Between September 2015 and November 2017, among 111 AF patients below 45 years of age, those without pre-existing pathologies and/or known risk factors were selected for the study. Based on baseline 12-lead−24-h Holter electrocardiogram (ECG), previous class 1C antiarrhythmic drug therapy, or ajmaline testing, patients were stratified as latent type 1 BrS or not.

Results: Within the 78 enrolled patients, 13 (16.7%; group 1) revealed a type 1 BrS ECG pattern, while 65 (83.3%; group 2) did not. Mean age was 37 ± 8 vs. 35 ± 7 (p = 0.42), and males were 7 (54%) vs. 54 (83%) (p = 0.02) in the two groups, respectively. Family history of BrS was significantly more common within group 1 patients (2, 15% vs. 0; p = 0.03), and 4 (31%) patients experienced syncope in group 1 vs. 5 (8%) in group 2 (p = 0.02). After a mean follow-up of 42 ± 18 months from the index AF event, more than 80% of the patients, in both study groups, were in sinus rhythm.

Conclusion: In young patients with AF without pre-existing pathologies and/or known risk factors, latent BrS should be suspected. Syncope and a family history of BrS emerge as easily identifiable factors related to BrS. Long-term sinus rhythm maintenance appears satisfactory, either in the presence or not of BrS.

Incidence and predictors of atrial fibrillation in a Chinese cohort of Brugada syndrome

BACKGROUND

Atrial electrophysiological abnormalities have previously been reported in Brugada syndrome. We investigated the incidence and electrocardiographic predictors of atrial fibrillation (AF) in a Chinese cohort of Brugada syndrome patients.

METHODS

A retrospective study of Brugada syndrome patients admitted to tertiary centers in Hong Kong.

RESULTS

A total of 275 patients were included (median age at presentation: 53 [40-64], 247 (90%) males) with a median follow-up duration of 67 (31-113) months. A total of 14 patients (5%) developed AF. Inter-atrial block and AV block were found in 36% (n = 100) and 13% (n = 37) of all patients. Compared to those in sinus rhythm, patients with AF showed significantly longer P-wave duration (PWD) (125 [116-137] vs. 114 [106-124] ms, P = 0.009) and PR interval (190 [163-214] vs. 169 [153-184] ms; P = 0.023). They were more likely to develop syncope (79 vs. 43%; P = 0.012) or VT/VF (43 vs. 14%; P = 0.012), undergo electrophysiological studies (36 vs. 19%; P = 0.005) and receive ICDs (71 vs. 25%; P = 0.001). Univariate logistic regression showed that mean PWD (odds ratio [OR]: 1.03 [1.00-1.06], P = 0.021), PR interval (OR: 1.02 [1.01-1.04]; P = 0.010) and QT interval (OR: 1.02 [1.00-1.04], P = 0.012), syncope (OR: 4.80 [1.31-17.61], P = 0.018) and R-wave amplitude in lead V5 (OR: 0.30 [0.09-1.00]; P = 0.05) significantly predicted incident AF. Receiver operating characteristic analysis revealed an optimum cut-off point of 123 ms and area under the curve of 0.71 for PWD.

CONCLUSION

The incidence of AF was 5% in this cohort. PWD, PR and QT intervals significantly predicted AF and are simple electrocardiographic markers for identifying potential at-risk patients.

Clinical characterisation of a novel SCN5A variant associated with progressive malignant arrhythmia and dilated cardiomyopathy

INTRODUCTION

The SCN5A gene is implicated in many arrhythmogenic and cardiomyopathic processes. We identified a novel SCN5A variant in a family with significant segregation in individuals affected with progressive sinus and atrioventricular nodal disease, atrial arrhythmia, dilated cardiomyopathy, and early sudden cardiac arrest.

METHODS

A patient pedigree was created following the clinical evaluation of three affected individuals, two monozygotic twins and a paternal half-brother, which lead to the evaluation of a paternal half-sister (four siblings with the same father and three mothers) all of whom experienced varying degrees of atrial arrhythmias, conduction disease, and dilated cardiomyopathy in addition to a paternal history of unexplained death in his 50s with similar autopsy findings. The index male underwent sequencing of 58 genes associated with cardiomyopathies. Sanger sequencing was used to provide data for bases with insufficient coverage and for bases in some known regions of genomic segmental duplications. All clinically significant and novel variants were confirmed by independent Sanger sequencing.

RESULTS

All relatives tested were shown to have the same SCN5A variant of unknown significance (p. Asp197His) and the monozygotic twins shared a co-occurring NEXN (p. Glu575*). Segregation analysis demonstrates likely pathogenic trait for the SCN5A variant with an additional possible role for the NEXN variant in combination.

CONCLUSIONS

There is compelling clinical evidence suggesting that the SCN5A variant p. Asp197His may be re-classified as likely pathogenic based on the segregation analysis of our family of interest. Molecular mechanism studies are pending.

Caring for the pregnant woman with an inherited arrhythmia syndrome

Pregnancy is a period of increased cardiovascular risk in a woman's life. In the setting of an inherited arrhythmia syndrome (IAS), cardiologists and obstetricians may be unfamiliar with cardiovascular optimization and risk stratification in pregnancy. Historically, there were little data addressing the safety of pregnancy in these rare disorders. Recent advances suggest that no type of IAS represents an absolute contraindication to pregnancy. However, it is imperative that obstetric and cardiovascular clinicians understand the major forms of IAS and how they affect the risks and course of pregnancy. This includes any disease-specific proarrhythmic triggers unique to pregnancy, such as the postpartum period in long QT syndrome (especially type 2), which poses the greatest risk of arrhythmias, and the adrenergic nature of labor and delivery, which is relevant to catecholaminergic polymorphic ventricular tachycardia. Fortunately, several effective antiarrhythmic options exist that pose little fetal risk. IAS-specific optimization of implantable cardioverter-defibrillator algorithms, drug therapy, and a maternal cardiac plan addressing the antepartum, labor, and delivery and postpartum periods reduces the risk. Where evidence does not exist, there are plausible mechanistic considerations to guide clinicians. To achieve optimal outcomes, early involvement of an expert pregnancy heart team comprising obstetrics, genetics, cardiology, and anesthesiology team members and a shared decision-making approach to IAS issues in pregnancy are needed.

Multi-disciplinary approach to perioperative risk assessment and post-transplant management for liver transplantation in a patient at risk for Brugada syndrome

Brugada syndrome, an autosomal dominant genetic disorder, is characterised by abnormal electrocardiogram findings and increased risk of ventricular tachyarrhythmias and sudden cardiac death. Our report describes the multi-disciplinary perioperative management of a 28-year-old patient presenting to the Duke Transplant Center with a familial sodium channel gene SCN51 mutation concerning Brugada syndrome. We discuss the preparatory work-up, medication review and appropriate post-surgical follow-up for patients undergoing liver transplant surgery with cardiac monitoring.

The definition of the Brugada syndrome

Brugada syndrome (BS) is an inherited disease characterized by a coved-type ST-segment elevation in the right precordial leads and increased risk of sudden cardiac death (SCD), in the absence of structural abnormalities. The cornerstone of BS diagnosis and definition, is its characteristic ECG pattern that can be present spontaneously or unmasked by drugs. Brugada syndrome was first described 25 years ago; paradoxically, in an era of great technological development, a new syndrome was described with a technology developed almost a century before. Great scientific knowledge has been gathered since the description of the syndrome. The better understanding of its pathophysiology and genetic basis has led to several modifications in its definition. Despite these facts, the essential, the description of the specific ECG pattern has remained almost unchanged since the initial report. In this article, we present the definition of the BS, the rationale behind it and our thoughts about its future.

Impact of Supraventricular Tachyarrhythmia in Patients With Inherited Cardiac Arrhythmia

Supraventricular tachyarrhythmia (SVT), especially atrial fibrillation (AF), has been observed in patients with inherited cardiac arrhythmia (ICA). Data on the time course of SVT and the occurrence of SVT other than AF is limited. In this study, we examined the prevalence, co-existence, and the time course of different types of SVT in patients with various ICAs. In this retrospective study, we selected 393 patients (median 49 years, range 17 to 87, 57% male) from a cohort of patients visiting the outpatient clinic for cardiogenetic screening of ICA. Patients' medical records were examined for the occurrence of AF and other SVT. AF/SVT was found in 49 patients (12%, 31 male, 42 ± 17 years). Patients presenting with only AF (n = 12, 3%) were older than patients presenting with only SVT (n = 28, 7%), respectively 52 ± 18 versus 37 ± 14, p = 0.007. Nineteen patients (5%) had multiple episodes of either AF (n = 7, 2%) or SVT (n = 12, 3%). Alternating episodes of AF and SVT occurred in 9 patients (2%). Intervals between second and third AF episodes were significantly shorter than between first and second episodes (p = 0.02). An implantable cardioverter defibrillator (ICD) was implanted in 158 patients (40.2%) and 26 patients (16%) had inappropriate ICD shocks (SVT 25, AF 1), particularly those with multiple SVT episodes (p = 0.003). In patients with a variety of ICAs, episodes of AF/SVT occurred in 12%. In patients with multiple AF episodes, intervals between consecutive episodes became significantly shorter over time. AF/SVT episodes are associated with inappropriate ICD shocks and aggressive therapy of AF/SVT is therefore justified.

Brugada syndrome in children - Stepping into unchartered territory

Brugada syndrome (BrS) is an autosomal dominant inherited channelopathy. It is associated with a typical pattern of ST-segment elevation in the precordial leads V1-V3 and potentially lethal ventricular arrhythmias in otherwise healthy patients. It is frequently seen in young Asian males, in whom it has previously been described as sudden unexplained nocturnal death syndrome. Although it typically presents in young adults, it is also known to present in children and infants, especially in the presence of fever. Our understanding of the genetic pathogenesis and management of BrS has grown substantially considering that it has only been 24 years since its first description as a unique clinical entity. However, there remains much to be learned, especially in the pediatric population. This review aims to discuss the epidemiology, genetics, and pathogenesis of BrS. We will also discuss established standards and new innovations in the diagnosis, prognostication, risk stratification, and management of BrS. Literature search was run on the National Center for Biotechnology Information's website, using the Medical Subject Headings (MeSH) database with the search term "Brugada Syndrome" (MeSH), and was run on the PubMed database using the age filter (birth-18 years), yielding 334 results. The abstracts of all these articles were studied, and the articles were categorized and organized. Articles of relevance were read in full. As and where applicable, relevant references and citations from the primary articles were further explored and read in full.

Scn2b Deletion in Mice Results in Ventricular and Atrial Arrhythmias

BACKGROUND

Mutations in SCN2B, encoding voltage-gated sodium channel β2-subunits, are associated with human cardiac arrhythmias, including atrial fibrillation and Brugada syndrome. Because of this, we propose that β2-subunits play critical roles in the establishment or maintenance of normal cardiac electric activity in vivo.

METHODS AND RESULTS

To understand the pathophysiological roles of β2 in the heart, we investigated the cardiac phenotype of Scn2b null mice. We observed reduced sodium and potassium current densities in ventricular myocytes, as well as conduction slowing in the right ventricular outflow tract region. Functional reentry, resulting from the interplay between slowed conduction, prolonged repolarization, and increased incidence of premature ventricular complexes, was found to underlie the mechanism of spontaneous polymorphic ventricular tachycardia. Scn5a transcript levels were similar in Scn2b null and wild-type ventricles, as were levels of Na_v1.5 protein, suggesting that similar to the previous work in neurons, the major function of β2-subunits in the ventricle is to chaperone voltage-gated sodium channel α-subunits to the plasma membrane. Interestingly, Scn2b deletion resulted in region-specific effects in the heart. Scn2b null atria had normal levels of sodium current density compared with wild type. Scn2b null hearts were more susceptible to atrial fibrillation, had increased levels of fibrosis, and higher repolarization dispersion than wild-type littermates.

CONCLUSIONS

Genetic deletion of Scn2b in mice results in ventricular and atrial arrhythmias, consistent with reported SCN2B mutations in human patients.

Long-Term Follow-Up of Probands With Brugada Syndrome

This study analyzes the natural history of a large cohort of probands with Brugada syndrome (BrS) to assess the predictive value of different clinical and electrocardiographic parameters for the development of ventricular fibrillation (VF) or sudden cardiac death (SCD) during a long-term follow-up. Baseline characteristics of 289 consecutive probands (203 men; mean age 45 ± 16 years) with a Brugada type 1 electrocardiogram were analyzed. After a mean follow-up of 10.1 ± 4.6 years, 29 malignant arrhythmias occurred. On multivariate analysis, a history of VF and syncopal episodes, fragmented QRS (f-QRS), spontaneous type 1 electrocardiogram, and early repolarization pattern were significantly associated with later occurrence of VF/SCD. In patients with drug-induced BrS, the accentuation or de novo appearance of f-QRS in other leads was always associated with VF/SCD. Cerebrovascular events occurred in 8 patients with atrial fibrillation (15.1%), most of them (75%) presenting as the first clinical manifestation. The time-to-diagnosis was found to be significantly shorter in those patients who directly came to our center than in those who referred to our center for a second opinion. In conclusion, systematic use of the pharmacologic challenge in patients with unexplained cardiovascular symptoms and/or atrial fibrillation might significantly improve the identification of BrS with a shortening of the time-to-diagnosis. The CHA₂DS₂VASc score might be inappropriate for predicting transient ischemic attack or stroke in BrS. This study confirms the independent predictive value of previous VF and syncopal episodes, f-QRS, type 1 electrocardiogram, and early repolarization pattern. In BrS a sufficiently long follow-up is necessary before conclusions on prognosis are apparent.

Brugada Pattern Caused by a Flecainide Overdose

BACKGROUND

Brugada pattern can be found on the electrocardiogram (ECG) of patients with altered mental status, usually with fever or drug intoxication. Diagnosis remains challenging, because the ECG changes are dynamic and variable. In addition, triggers are not always clearly identified. In patients with atrial fibrillation (AF), the use of class IC antidysrhythmic drugs can unmask a Brugada pattern on the ECG, especially if combined with other medications acting on sodium channels.

CASE REPORT

A 62-year-old man with a medical history of AF was admitted to our emergency department for altered mental status. The ECG at the time of admission showed a Brugada pattern, triggered by a flecainide overdose (about 1 g), in association with an unknown dose of lamotrigine and quetiapine. After discontinuation of all medications, the Brugada pattern disappeared and his ECG showed no abnormalities. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: In patients with AF, the use of class IC antidysrhythmic drugs, if overdosed, can trigger a Brugada ECG pattern, and therefore it can increase the risk for malignant dysrhythmias. It is important to provide, to all patients with a Brugada ECG pattern, a list of drugs to avoid, and to underline the synergistic interplay between drugs, taking into consideration all patients' comorbidities.

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.

Atrial arrhythmias in inherited arrhythmogenic disorders

Atrial arrhythmias are being increasingly recognized in inherited arrhythmogenic disorders particularly in patients with Brugada syndrome and short QT syndrome. Atrial arrhythmias in inherited arrhythmogenic disorders have significant epidemiologic, clinical, and prognostic implications. There has been progress in the understanding of underlying genetic characteristics and the mechanistic link between atrial arrhythmias and inherited arrhythmogenic disorders. Appropriate management of these patients is of paramount importance.

Brugada Syndrome: Defining the Risk in Asymptomatic Patients

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

Brugada syndrome: More than 20 years of scientific excitement

In 1992 we reported on eight patients with a particular electrocardiograph (ECG) showing ST segment elevation in the right precordial leads. All patients had a structurally normal heart and had survived one or multiple episodes of near sudden death caused by ventricular fibrillation. We showed 6 years later that this disease, known nowadays as Brugada syndrome, was caused by mutations in the SCN5A gene which encodes for the cardiac sodium channel. Other genes where mutations result in the same ECG have been also identified, with at present more than 17 different genes published. These data show that Brugada syndrome is a genetically heterogeneous disease as is also the case in the long QT syndrome. In Brugada syndrome, the clue to the initial clinical diagnosis remains the abnormal ECG. However, it was evident from the beginning that the ECG of Brugada syndrome is variable and sensitive to many autonomic, drug, exercise, emotions and other external influences such as a meal, fever, changes in heart rate from any cause, and even body position. When followed intensively, all patients with a Brugada ECG will show a completely normal ECG at one or another moment in their lives. The spontaneous normalization of the ECG represents a major diagnostic challenge, because a patient with Brugada syndrome seen during normalization of the ECG may fail to get the correct diagnosis. In these more than 20 years great challenges have been overcome but some remain, mainly the approach to the asymptomatic individual with a diagnosis of Brugada syndrome. In 30-50% of individuals who die suddenly because of documented or suspected Brugada syndrome, sudden death is the first manifestation of the disease. Thus, these individuals were fully asymptomatic until the first fatal event.

Syncope in Hereditary Arrhythmogenic Syndromes

Since the discovery of the first mutation causing long QT syndrome (LQTS) in 1995, the field of hereditary arrhythmogenic syndromes has expanded greatly. Today, these syndromes include LQTS, Brugada syndrome, catecholaminergic polymorphic ventricular tachycardia, and short QT syndrome. There is also evidence suggesting that the newly described malignant early repolarization syndrome also has a genetic cause.

Atrial fibrillation in a large population with Brugada electrocardiographic pattern: prevalence, management, and correlation with prognosis

BACKGROUND

A high prevalence of atrial fibrillation/atrial flutter (AF/AFl) has been reported in small series of Brugada patients, with discordant data.

OBJECTIVE

The purpose of this study was to analyze, in a large population of Brugada patients, the prevalence of AF/AFl, its correlation with prognosis, and the efficacy of hydroquinidine (HQ) treatment.

METHODS

Among 560 patients with Brugada type 1 ECG (BrECG), 48 (9%) had AF/AFl. Three groups were considered: 23 patients with BrECG pattern recognized before AF/AFl (group 1); 25 patients first diagnosed with AF/AFl in whom Class IC antiarrhythmic drugs administered for cardioversion/prophylaxis unmasked BrECG (group 2); and 512 patients without AF/AFl (group 3). Recurrence of AF/AFl and occurrence of ventricular arrhythmias were evaluated at follow-up.

RESULTS

Mean age was 47 ± 15 years, 59 ± 11 years, and 44 ± 14 years in groups 1, 2, and 3, respectively. Seven subjects (32%) in group 1 had syncope/aborted sudden death, 1 (4%) in group 2, and 122 (24%) in group 3. Ventricular arrhythmia occurred in three patients in group 1, none in group 2, and 10 in group 3 at median follow-up of 51, 68, and 41 months, respectively. Nine patients in group 1 and nine in group 2 received HQ for AF/AFl prophylaxis; on therapy, none had AF/AFl recurrence.

CONCLUSION

Prevalence of AF/AFl in Brugada patients is higher than in the general population of the same age. Patients in group 1 are younger than those in group 2 and have a worse prognosis compared to both groups 2 and 3. HQ therapy has proved useful and safe in patients with AF/AFl and BrECG.

Deterioration of the circadian variation of heart rate variability in Brugada syndrome may contribute to the pathogenesis of ventricular fibrillation

AIMS

Abnormal sympathetic innervation triggers ventricular fibrillation (VF). We examined the circadian variation of autonomic nervous system and its relevance to risk stratification of VF in patients with Brugada syndrome (Brs).

METHODS

We enrolled 12 male Brs patients with documented VF (Brs-S; mean age, 42±4 years), 17 without documented VF (Brs-N; mean age 48±4 years), and 16 age- and gender-matched controls. The clinical data, 12-lead electrocardiography (ECG), signal-averaged ECG, electrophysiological study (EPS), and heart rate variability from 24h Holter ECG were compared between the groups.

RESULTS

The low frequency components (LF) in Brs-S and Brs-N and high frequency components (HF) in Brs-S patients were significantly lower than in the controls (409.8±128.6ms(2), 329.5±108ms(2) vs. 945.3±111.3ms(2); 135.1±73.8ms(2) vs. 391.8±63.9ms(2), respectively). The circadian variation of the LF and LF/HF decreased in the Brs patients, the standard deviation (SD) of LF/HF (<2.5) and SD of LF (<400ms(2)) had sufficiently high sensitivity (96.6%) and specificity (92.9%) for the diagnosis of Brs. Most of the Brs-S patients (83.3%) were located under the line formed by the SD/mean of HF=SD/mean of LF in the scatter plots.

CONCLUSION

Lack of the circadian variation of autonomic function occurs in Brs, and this may contribute to the pathogenesis of VF.