Results of ajmaline testing in patients with arrhythmogenic right ventricular dysplasia–cardiomyopathy

The diagnostic role of pharmacological provocation testing in cardiac electrophysiology: a clinical consensus statement of the European Heart Rhythm Association and the European Association of Percutaneous Cardiovascular Interventions (EAPCI) of the ESC, the ESC Working Group on Cardiovascular Pharmacotherapy, the Association of European Paediatric and Congenital Cardiology (AEPC), the Paediatric & Congenital Electrophysiology Society (PACES), the Heart Rhythm Society (HRS), the Asia Pacific Heart Rhythm Society (APHRS), and the Latin American Heart Rhythm Society (LAHRS)

The pharmacological provocation test is a pivotal tool in cardiac electrophysiology for the diagnosis of potential causes of sudden cardiac death, sudden cardiac arrest (SCA), arrhythmias, symptoms, or ECG abnormalities. The 2022 European Society of Cardiology Guidelines for the Treatment of Ventricular Arrhythmias and Prevention of Sudden Cardiac Death offered guidance on provocation testing but did not describe the indications and requirements in depth. This clinical consensus statement, led by the European Heart Rhythm Association and approved by major international stakeholders, aims to advise the general cardiologist and the arrhythmia expert who to test and when, where, and how to do it. The statement focuses on current practice for the diagnosis of subclinical arrhythmia syndromes and the causes of SCA, building upon the recommendations of the Guidelines. We address the sodium channel blocker provocation test for patients suspected of Brugada syndrome as well as the use of epinephrine, isoproterenol, adenosine, ergonovine, and acetylcholine.

Inherited Arrhythmias in the Pediatric Population: An Updated Overview

Pediatric cardiomyopathies (CMs) and electrical diseases constitute a heterogeneous spectrum of disorders distinguished by structural and electrical abnormalities in the heart muscle, attributed to a genetic variant. They rank among the main causes of morbidity and mortality in the pediatric population, with an annual incidence of 1.1-1.5 per 100,000 in children under the age of 18. The most common conditions are dilated cardiomyopathy (DCM) and hypertrophic cardiomyopathy (HCM). Despite great enthusiasm for research in this field, studies in this population are still limited, and the management and treatment often follow adult recommendations, which have significantly more data on treatment benefits. Although adult and pediatric cardiac diseases share similar morphological and clinical manifestations, their outcomes significantly differ. This review summarizes the latest evidence on genetics, clinical characteristics, management, and updated outcomes of primary pediatric CMs and electrical diseases, including DCM, HCM, arrhythmogenic right ventricular cardiomyopathy (ARVC), Brugada syndrome (BrS), catecholaminergic polymorphic ventricular tachycardia (CPVT), long QT syndrome (LQTS), and short QT syndrome (SQTS).

Investigation of Unexplained Cardiac Arrest: Phenotyping and Genetic Testing

Unexplained cardiac arrest (UCA) is a working diagnosis that should be replaced by a final diagnosis once evaluation is completed. Complete evaluation of UCA should include high-yield tests like cardiac magnetic resonance imaging, exercise treadmill test, and sodium-channel blocker challenge to identify latent causes of UCA. If no clear etiology is revealed after complete evaluation, idiopathic ventricular fibrillation may be diagnosed, and the strength of its diagnosis can be divided into definitive, probable, and possible based on the number of high-yield tests performed. Care should be provided by a multidisciplinary team with expertise in this area.

Brugada Syndrome: From Molecular Mechanisms and Genetics to Risk Stratification

Brugada syndrome (BrS) is a rare hereditary arrhythmia disorder, with a distinctive ECG pattern, correlated with an increased risk of ventricular arrhythmias and sudden cardiac death (SCD) in young adults. BrS is a complex entity in terms of mechanisms, genetics, diagnosis, arrhythmia risk stratification, and management. The main electrophysiological mechanism of BrS requires further research, with prevailing theories centered on aberrant repolarization, depolarization, and current-load match. Computational modelling, pre-clinical, and clinical research show that BrS molecular anomalies result in excitation wavelength (k) modifications, which eventually increase the risk of arrhythmia. Although a mutation in the SCN5A (Sodium Voltage-Gated Channel Alpha Subunit 5) gene was first reported almost two decades ago, BrS is still currently regarded as a Mendelian condition inherited in an autosomal dominant manner with incomplete penetrance, despite the recent developments in the field of genetics and the latest hypothesis of additional inheritance pathways proposing a more complex mode of inheritance. In spite of the extensive use of the next-generation sequencing (NGS) technique with high coverage, genetics remains unexplained in a number of clinically confirmed cases. Except for the SCN5A which encodes the cardiac sodium channel NaV1.5, susceptibility genes remain mostly unidentified. The predominance of cardiac transcription factor loci suggests that transcriptional regulation is essential to the Brugada syndrome's pathogenesis. It appears that BrS is a multifactorial disease, which is influenced by several loci, each of which is affected by the environment. The primary challenge in individuals with a BrS type 1 ECG is to identify those who are at risk for sudden death, researchers propose the use of a multiparametric clinical and instrumental strategy for risk stratification. The aim of this review is to summarize the latest findings addressing the genetic architecture of BrS and to provide novel perspectives into its molecular underpinnings and novel models of risk stratification.

Arrhythmogenic Right Ventricular Cardiomyopathy and Differential Diagnosis with Diseases Mimicking Its Phenotypes

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited heart muscle disease, which is characterized by fibro-fatty replacement of predominantly the right ventricle (RV). The disease can result in ventricular tachyarrhythmias and sudden cardiac death. Our understanding of the pathophysiology and clinical expressivity of ARVC has been continuously evolving. The diagnosis can be challenging due to its variable expressivity, incomplete penetrance and the lack of specific diagnostic criteria. Idiopathic RV outflow tract tachycardia, Brugada Syndrome, athlete’s heart, dilated cardiomyopathy, myocarditis, cardiac sarcoidosis, congenital aneurysms and diverticula may mimic clinical phenotypes of ARVC. This review aims to provide an update on the differential diagnosis of ARVC.

Clinical Genetics of Inherited Arrhythmogenic Disease in the Pediatric Population

Sudden death is a rare event in the pediatric population but with a social shock due to its presentation as the first symptom in previously healthy children. Comprehensive autopsy in pediatric cases identify an inconclusive cause in 40-50% of cases. In such cases, a diagnosis of sudden arrhythmic death syndrome is suggested as the main potential cause of death. Molecular autopsy identifies nearly 30% of cases under 16 years of age carrying a pathogenic/potentially pathogenic alteration in genes associated with any inherited arrhythmogenic disease. In the last few years, despite the increasing rate of post-mortem genetic diagnosis, many families still remain without a conclusive genetic cause of the unexpected death. Current challenges in genetic diagnosis are the establishment of a correct genotype-phenotype association between genes and inherited arrhythmogenic disease, as well as the classification of variants of uncertain significance. In this review, we provide an update on the state of the art in the genetic diagnosis of inherited arrhythmogenic disease in the pediatric population. We focus on emerging publications on gene curation for genotype-phenotype associations, cases of genetic overlap and advances in the classification of variants of uncertain significance. Our goal is to facilitate the translation of genetic diagnosis to the clinical area, helping risk stratification, treatment and the genetic counselling of families.

Brugada syndrome and arrhythmogenic cardiomyopathy: overlapping disorders of the connexome?

Arrhythmogenic cardiomyopathy (ACM) and Brugada syndrome (BrS) are inherited diseases characterized by an increased risk for arrhythmias and sudden cardiac death. Possible overlap between the two was suggested soon after the description of BrS. Since then, various studies focusing on different aspects have been published pointing to similar findings in the two diseases. More recent findings on the structure of the cardiac cell-cell junctions may unite the pathophysiology of both diseases and give further evidence to the theory that they may in part be variants of the same disease spectrum. In this review, we aim to summarize the studies indicating the pathophysiological, genetic, structural, and electrophysiological overlap between ACM and BrS.

Evaluating the Use of Genetics in Brugada Syndrome Risk Stratification

The evolution of the current dogma surrounding Brugada syndrome (BrS) has led to a significant debate about the real usefulness of genetic testing in this syndrome. Since BrS is defined by a particular electrocardiogram (ECG) pattern, after ruling out certain possible causes, this disease has come to be defined more for what it is not than for what it is. Extensive research is required to understand the effects of specific individual variants, including modifiers, rather than necessarily grouping together, for example, “all SCN5A variants” when trying to determine genotype-phenotype relationships, because not all variants within a particular gene act similarly. Genetic testing, including whole exome or whole genome testing, and family segregation analysis should always be performed when possible, as this is necessary to advance our understanding of the genetics of this condition. All considered, BrS should no longer be considered a pure autosomal dominant disorder, but an oligogenic condition. Less common patterns of inheritance, such as recessive, X–linked, or mitochondrial may exist. Genetic testing, in our opinion, should not be used for diagnostic purposes. However, variants in SCN5A can have a prognostic value. Patients should be diagnosed and treated per the current guidelines, after an arrhythmologic examination, based on the presence of the specific BrS ECG pattern. The genotype characterization should come in a second stage, particularly in order to guide the familial diagnostic work-up. In families in which an SCN5A pathogenic variant is found, genetic testing could possibly contribute to the prognostic risk stratification.

Role of Provocable Brugada ECG Pattern in The Correct Risk Stratification for Major Arrhythmic Events

The so-called Brugada syndrome (BS), first called precordial early repolarization syndrome (PERS), is characterized by the association of a fascinating electrocardiographic pattern, namely an aspect resembling right bundle branch block with a coved and sometime upsloping ST segment elevation in the precordial leads, and major ventricular arrhythmic events that could rarely lead to sudden death. Its electrogenesis has been related to a conduction delay mostly, but not only, located on the right ventricular outflow tract (RVOT), probably due to a progressive fibrosis of the conduction system. Many tests have been proposed to identify people at risk of sudden death and, among all, ajmaline challenge, thanks to its ability to enhance latent conduction defects, became so popular, even if its role is still controversial as it is neither specific nor sensitive enough to guide further invasive investigations and managements. Interestingly, a type 1 pattern has also been induced in many other cardiac diseases or systemic diseases with a cardiac involvement, such as long QT syndrome (LQTS), arrhythmogenic right ventricular cardiomyopathy (ARVC), hypertrophic cardiomyopathy (HCM) and myotonic dystrophy, without any clear arrhythmic risk profile. Evidence-based studies clearly showed that a positive ajmaline test does not provide any additional information on the risk stratification for major ventricular arrhythmic events on asymptomatic individuals with a non-diagnostic Brugada ECG pattern.

A case of anomalous aortic origin of coronary artery associated with a coved-type electrocardiogram

Brugada syndrome (BrS) is a sudden cardiac death syndrome characterized by a coved-type electrocardiogram (ECG). Different disorders, such as ischemia, can emulate a Brugada-pattern ECG (Brugada phenocopy). We report herein, the first case of surgical epicardial electrophysiological mapping in a successfully resuscitated patient with an anomalous aortic origin of the coronary artery (AAOCA) associated with a coved-type ECG. It was debatable whether the coved-type ECG and the abnormal arrhythmogenic substrate in the epicardial right ventricular outflow tract were derived from BrS or from repetitive ischemia due to AAOCA; however, the epicardial electrophysiological mapping helped in deciding the treatment strategy.

Ajmaline Testing and the Brugada Syndrome

Brugada syndrome (BrS) diagnosis requires the presence of a typical type 1 ECG pattern. Owing to the spontaneous ECG variability, the real BrS prevalence in the general population remains unclear. The aim of the present study was to evaluate the prevalence of positive ajmaline challenge for BrS in a cohort of consecutive patients who underwent electrophysiological evaluation for different clinical reasons. All consecutive patients from 2008 to 2019 who underwent ajmaline testing were prospectively included. A total of 2,456 patients underwent ajmaline testing, 742 (30.2%) in the context of familial screening for BrS. In non-familial screening group (1,714) ajmaline testing resulted positive in 186 (10.9%). Indications for ajmaline testing were: suspicious BrS ECG in 23 cases (12.4%), palpitations in 27 (14.5%), syncope in 71 (38.2%), presyncope in 7 (3.8%), family history of sudden cardiac death in 18 (9.7%), documented ventricular arrhythmias in 12 (6.5%), unexplained cardiac arrest in 4 (2.2%), atrial fibrillation in 16 (8.5%), brady-arrhythmias in 1 (0.5%), and cerebrovascular accidents in 7 (3.7%). Compared with the overall population, ajmaline testing positive patients were younger (42.8 ± 15.5 vs 48.9 ± 20.4; p <0.001) and more frequently male (65.1% vs 56.3%; p = 0.023). Implantable cardioverter defibrillator was implanted in 84 patients (45.2%). During a median follow-up of 42.4 months, 12 appropriate shocks and 13 implantable cardioverter defibrillator related complications were reported. In conclusion, the BrS was diagnosed in an unexpected high proportion of patients that underwent ajmaline testing for a variety of cardiovascular symptoms. This can lead to an adequate counseling and clinical management in BrS patients.

Worse Prognosis in Brugada Syndrome Patients With Arrhythmogenic Cardiomyopathy Features

OBJECTIVES

This study aimed to assess the presence of echocardiographic and electrocardiographic similarities in patients with Brugada syndrome (BrS) and arrhythmogenic cardiomyopathy (AC) and the prevalence and prognostic value of AC structural/electrical features in patients with BrS.

BACKGROUND

BrS and AC are genetic cardiac diseases with high risk for sudden cardiac death. Although BrS and AC display different features, previous reports suggest a phenotypic overlap.

METHODS

We acquired clinical data, electrocardiogram, and transthoracic echocardiography in patients with BrS and AC. We assessed the presence of AC diagnostic criteria according to the 2010 AC task force criteria for right ventricular outflow tract (RVOT), fractional area change, depolarization, and repolarization in the patients with BrS. We compared arrhythmic outcome in BrS patients with and without AC structural/electrical criteria.

RESULTS

A total of 116 BrS and 141 AC patients were included. AC electrical features were present in 28 (24%) BrS patients and structural features in 97 (84%) BrS patients. BrS patients with an RVOT or depolarization AC criterion showed a trend towards worse severe arrhythmia-free survival compared to BrS patients without (p = 0.05). The criterion for RVOT dilation showed high sensitivity and improved detection of arrhythmic BrS patients when added to type 1 electrocardiogram pattern and syncope (area under the curve 0.73 [95% confidence interval: 0.59 to 0.87] vs. area under the curve 0.79 [95% confidence interval: 0.69 to 0.90]); p = 0.009).

CONCLUSIONS

In this large cohort comparison, Brugada syndrome (BrS) and arrhythmogenic cardiomyopathy patients had phenotypic overlap. The presence of arrhythmogenic cardiomyopathy diagnostic criteria in BrS patients was associated with a trend towards higher arrhythmic risk. The right ventricular outflow tract dilation criterion improved detection of arrhythmic BrS patients.

Clinical Diagnosis, Imaging, and Genetics of Arrhythmogenic Right Ventricular Cardiomyopathy/Dysplasia: JACC State-of-the-Art Review

Arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) is an inherited cardiomyopathy that can lead to sudden cardiac death and heart failure. Our understanding of its pathophysiology and clinical expressivity is continuously evolving. The diagnosis of ARVC/D remains particularly challenging due to the absence of specific unique diagnostic criteria, its variable expressivity, and incomplete penetrance. Advances in genetics have enlarged the clinical spectrum of the disease, highlighting possible phenotypes that overlap with arrhythmogenic dilated cardiomyopathy and channelopathies. The principal challenges for ARVC/D diagnosis include the following: earlier detection of the disease, particularly in cases of focal right ventricular involvement; differential diagnosis from other arrhythmogenic diseases affecting the right ventricle; and the development of new objective electrocardiographic and imaging criteria for diagnosis. This review provides an update on the diagnosis of ARVC/D, focusing on the contribution of emerging imaging techniques, such as echocardiogram/magnetic resonance imaging strain measurements or computed tomography scanning, new electrocardiographic parameters, and high-throughput sequencing.

The Diagnostic Yield of Brugada Syndrome After Sudden Death With Normal Autopsy

BACKGROUND

Familial evaluation after a sudden death with negative autopsy (sudden arrhythmic death syndrome; SADS) may identify relatives at risk of fatal arrhythmias.

OBJECTIVES

This study aimed to assess the impact of systematic ajmaline provocation testing using high right precordial leads (RPLs) on the diagnostic yield of Brugada syndrome (BrS) in a large cohort of SADS families.

METHODS

Three hundred three SADS families (911 relatives) underwent evaluation with resting electrocardiogram using conventional and high RPLs, echocardiography, exercise, and 24-h electrocardiogram monitor. An ajmaline test with conventional and high RPLs was undertaken in 670 (74%) relatives without a familial diagnosis after initial evaluation. Further investigations were guided by clinical suspicion.

RESULTS

An inherited cardiac disease was diagnosed in 128 (42%) families and 201 (22%) relatives. BrS was the most prevalent diagnosis (n = 85, 28% of families; n = 140, 15% of relatives). Ajmaline testing was required to unmask the BrS in 97% of diagnosed individuals. The use of high RPLs showed a 16% incremental diagnostic yield of ajmaline testing by diagnosing BrS in an additional 49 families. There were no differences of the characteristics between individuals and families with a diagnostic pattern in the conventional and the high RPLs. On follow-up, a spontaneous type 1 Brugada pattern and/or clinically significant arrhythmic events developed in 17% (n = 25) of the concealed BrS cohort.

CONCLUSIONS

Systematic use of ajmaline testing with high RPLs increases substantially the yield of BrS in SADS families. Assessment should be performed in expert centers where patients are counseled appropriately for the potential implications of provocation testing.

[Not Available]

This review includes main positions of the revision of diagnostic criteria of "J-wave syndromes in the J-Wave Syndromes Expert Consensus Conference Report: Emerging Concepts and Gaps in Knowledge" (2016). The article, systematized according to the sections of the above-mentioned document, outlines the questions of terminology, new criteria for diagnosis of the Brugada syndrome (BrS) and early repolarization syndrome (ERS). The section devoted to ERS on the issues of new terminology and standardization of measurements, is supplemented with material from the Consensus Paper - The Early Repolarization Pattern (2015). The article also presents the issues of differential diagnosis in BrS, presents modulating factors, defines acquired Brugada-pattern and Brugada phenocopies. The similarities and differences between BrS and ERS are presented in a comparative aspect.

Relations between right ventricular morphology and clinical, electrical and genetic parameters in Brugada Syndrome

BACKGROUND

Increasing evidence suggests the presence of structural changes affecting the right ventricular outflow tract (RVOT) in patients with Brugada Syndrome (BrS). The aim of this study was to characterise the RV morphology in BrS and explore associations between morphologic, clinical, electrical, and genetic parameters using non-invasive multimodality testing.

METHODS

Consecutive BrS patients (recruited 2013-2015) underwent clinical assessment, dedicated RV imaging using cardiac magnetic resonance (CMR) imaging (unless contra-indicated), electrical assessment (electrocardiogram, Holter monitoring, signal-averaged ECG[SAECG]) and genotyping. Morphologic data were compared to matched control and unmatched ARVC (arrhythmogenic right ventricular cardiomyopathy) cohorts, and potential associations between morphologic parameters and other variables were explored.

RESULTS

BrS patients (n = 42, male 86%, age 46±12 years) exhibited normal global RV volume and function, comparable to control, in contrast to significantly larger, impaired RVs in ARVC cohort (RVESV p = 0.0001; RVEDV p<0.0001, RVEF p = 0.002). Compared with control, BrS patients exhibited larger RVOT volumes (7.4 ± 0.7 vs 5.8 ± 0.7 mL/m2, p<0.0001) and wall motion abnormalities (RWMA) (31% vs 0%, p = 0.005); compared with ARVC cohort, the RVOT volumes were similar (7.4 ± 0.7 vs, 8.1 ± 1.7, p = 0.52) and there were less RWMA (31% vs 76%, p = 0.01). Overall 67% BrS patients had abnormal RVOT morphology. Patients with abnormal RVOT tended to be older (48 ± 12 y vs 41 ± 12y, p = 0.06). Rare genetic variants were only observed in patients with abnormal RVOT morphology (36% vs 0%, p = 0.02).

CONCLUSIONS

Patients with BrS frequently exhibit structural abnormalities localised to the RVOT and these changes may be age- and gene-dependent.

An overlap of Brugada syndrome and arrhythmogenic right ventricular cardiomyopathy/dysplasia

Overlapping characteristics of Brugada syndrome (BrS) and arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) have been reported in recent studies, but little is known about the overlapping disease state of BrS and ARVC/D. A 36-year-old man, hospitalized at our institution for syncope, presented with this overlapping disease state. The electrocardiogram showed spontaneous coved-type ST-segment elevation, and ventricular fibrillation was induced by right ventricular outflow tract stimulation in an electrophysiological study. BrS was subsequently diagnosed; additionally, the presence of epsilon-like waves and right ventricular structural abnormalities met with the 2010 revised task force criteria for ARVC/D. After careful investigation for both BrS and ARVC/D, an implantable cardioverter defibrillator was inserted in the patient. This case revealed 2 important clinical findings: (1) BrS and ARVC/D clinical features can coexist in a single patient, and EPS might be useful for determining the phenotype of overlapping disease (e.g., BrS-like or ARVC/D-like). (2) An overlapping disease state of BrS and ARVC/D can change phenotypically during its clinical course. Therefore, careful examination and attentive follow-up are required for patients with BrS or ARVC/D.

Brugada syndrome: an update

More than 20 years have passed since the description of Brugada syndrome as a clinical entity. The original case series depicted patients who all had coved ST-segment elevation in the right precordial leads, associated with a high risk of sudden death and no apparent structural heart disease. As subsequent registry data were published, it became apparent that the spectrum of risk is wide, with the majority of patients classified as low risk. Two consensus documents have been published that will continue to be updated. Despite intense research efforts, many controversies still exist over its pathophysiology and the risk stratification for sudden death. Management continues to be challenging with a lack of drug therapy and high complication rates from implantable cardioverter defibrillators. In this review, we highlight the current state-of-the-art therapies and their controversies.

Silencing of desmoplakin decreases connexin43/Nav1.5 expression and sodium current in HL‑1 cardiomyocytes

Desmosomes and gap junctions are situated in the intercalated disks of cardiac muscle and maintain the integrity of mechanical coupling and electrical impulse conduction between cells. The desmosomal plakin protein, desmoplakin (DSP), also plays a crucial role in the stability of these interconnected components as well as gap junction connexin proteins. In addition to cell‑to‑cell junctions, other molecules, including voltage‑gated sodium channels (Nav1.5) are present in the intercalated disk and support the contraction of cardiac muscle. Mutations in genes encoding desmosome proteins may result in fatal arrhythmias, including arrhythmogenic right ventricular cardiomyopathy (ARVC). Therefore, the aim of the present study was to determine whether the presence of DSP is necessary for the normal function and localization of gap junction protein connexin43 (Cx43) and Nav1.5. To examine this hypothesis, RNA interference was utilized to knock down the expression of DSP in HL‑1 cells and the content, distribution and function of Cx43 and Nav1.5 was assessed. Western blotting and flow cytometry experiments revealed that Cx43 and Nav1.5 expression decreased following DSP silencing. In addition, immunofluorescence studies demonstrated that a loss of DSP expression led to an abnormal distribution of Cx43 and Nav1.5, while scrape‑loading dye/transfer revealed a decrease in dye transfer in DSP siRNA‑treated cells. The sodium current was also recorded by the whole‑cell patch clamp technique. The results indicated that DSP suppression decreased sodium current and slowed conduction velocity in cultured cells. The present study indicates that impaired mechanical coupling largely affects electrical synchrony, further uncovering the pathogenesis of ARVC.

Brugada ECG pattern: a physiopathological prospective study based on clinical, electrophysiological, angiographic, and genetic findings

Introduction: Brugada syndrome (BrS) is considered a primary electrical disease. However, morphological abnormalities have been reported and localized arrhythmogenic right ventricular (RV) dysplasia/cardiomyopathy (ARVD/C) may mimic its phenotype, raising the question of an overlap between these two conditions and making difficult the therapeutic management of patients with borderline forms. The main objective of this study was to assess prospectively the prevalence of BrS and ARVD/C on the basis of international criteria, in patients with BrS-ECG and normal echocardiography, looking for a potential overlap between the two pathologies. The secondary objectives were to describe and quantify angiographic structural alterations, hemodynamics, electrophysiology, and genetics in the setting of BrS-ECG. Materials and Methods: Hundred and fourteen consecutive patients matched in age underwent prospectively cardiac catheterization and quantitative biventricular contrast angiography to rule out a structural heart disease. Fifty-one patients with a BrS-ECG (BrS group, 7 F, 44 M, 43 ± 11 y) had a spontaneous or ajmaline-induced BrS coved type ECG. For angiographic comparison, 49 patients with localized ARVD/C but without ST segment elevation in the right precordial leads (14 F, 35 M, 39 ± 13 y) were also studied. They fulfilled international ESC/WHF 2000 criteria and presented angiographic localized forms, mainly confined to hypokinetic anteroapical zone (characterized by trabecular dysarray and hypertrophy), and/or diaphragmatic wall, thus resulting in RV normal volumes and preserved systolic function. These two populations were also compared with 14 control patients (7 F, 7 M, 38 ± 16 y). Among BrS group, we identified three main angiographic phenotypes: BrS group I = patients with normal RV (n = 15, 29%); BrS group II = patients with segmental RV wall motion abnormalities but no structural arguments for ARVD/C (n = 26, 51%); BrS group III = patients with localized abnormalities suggestive of focal ARVD/C (n = 10, 20%). Results: Among BrS group, 34/51 patients (67%) fulfilled BrS HRS/EHRA 2005 criteria. Nineteen (37%) were symptomatic for aborted sudden death, agonal nocturnal respiration or syncope. Ventricular stimulation was positive in 14 patients (28%). Angiography showed RV abnormalities in 36/51 patients (71%) of BrS group (BrS groups II and III). Late potentials were present in 73% (100% sensitivity and NPV for an angiographic ARVD/C, but poor specificity and PPV, both 37%). In BrS group III, 8/10 patients (16% of BrS patients) finally fulfilled international ESC/WHF 2000 ARVD/C criteria and 5/10 (10% of BrS patients) fulfilled BrS diagnostic criteria. An overlap was observed in 4 patients (8% of BrS patients) who fulfilled both ARVD/C and BrS criteria. Among the 45 genotyped patients, only one presented a SCN5A mutation, whereas a TRPM4 mutation was found in another patient. Both belonged to BrS group II. MOG1 gene analysis was negative for all patients, as were PKP2, DSP, DSG2, and DSC2 analyzes performed in BrS group III. Conclusions: Seventy-one percent of patients with a BrS-ECG had abnormal RV wall motion and 16 had structural alterations corresponding to localized (anteroapical and/or diaphragmatic) ARVD/C. Moreover, 8% of BrS-ECG patients fulfilled both BrS and ARVD/C criteria. Our results support the hypothesis of an overlap between BrS and localized forms of ARVD/C. Conversely, genetic screening was poorly contributive for both diseases in the present series.

Comparison of late potentials for 24 hours between Brugada syndrome and arrhythmogenic right ventricular cardiomyopathy using a novel signal-averaging system based on Holter ECG

BACKGROUND

Late potentials (LP) detected with signal-averaged ECGs are known to be useful in identifying patients at risk of Brugada syndrome (BS) and arrhythmogenic right ventricular cardiomyopathy (ARVC). Because the pathophysiology is clearly different between these disorders, we clarified the LP characteristics of these disorders.

METHODS AND RESULTS

This study included 15 BS and 12 ARVC patients and 20 healthy controls. All BS patients had characteristic ECG changes and symptomatic episodes. All ARVC patients had findings that were consistent with recent criteria. Three LP parameters (filtered QRS duration, root mean square voltage of the terminal 40 ms of the filtered QRS complex, and duration of low-amplitude signals [<40 µV] in the terminal, filtered QRS complex) were continuously measured for 24 hours using a novel Holter-based signal-averaged ECG system. The incidences of LP determination in BS (80%) and ARVC (91%) patients were higher than in healthy controls (5%; P<0.0001 in both) but did not differ between BS and ARVC patients. In BS patients, the dynamic changes of all LP parameters were observed, and they were pronounced at nighttime. On the contrary, these findings were not observed in ARVC patients. When the SD values of the 3 LP parameters (filtered QRS duration, root mean square voltage of the terminal 40 ms of the filtered QRS complex, and duration of low-amplitude signals [<40 µV] in the terminal, filtered QRS complex) over 24 hours were compared for the 2 patient groups, those values in BS patients were significantly greater than those in ARVC patients (P<0.0001 in all).

CONCLUSIONS

LP characteristics detected by the Holter-based signal-averaged ECG system over 24 hours differ between BS and ARVC patients. Dynamic daily variations of LPs were seen only in BS patients. This may imply that mechanisms of lethal ventricular arrhythmia in BS may be more correlated with autonomic abnormality than that of ARVC.

Diagnostic dilemmas: overlapping features of brugada syndrome and arrhythmogenic right ventricular cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy (ARVC) and Brugada syndrome are distinct clinical entities which diagnostic criteria exclude their coexistence in individual patients. ARVC is a myocardial disorder characterized by fibro-fatty replacement of the myocardium and ventricular arrhythmias. In contrast, the Brugada syndrome has long been considered a functional cardiac disorder: no gross structural abnormalities can be identified in the majority of patients and its electrocardiographic hallmark of coved-type ST-segment elevation in right precordial leads is dynamic. Nonetheless, a remarkable overlap in clinical features has been demonstrated between these conditions. This review focuses on this overlap and discusses its potential causes and consequences.

A new approach for the comparison of conduction abnormality between arrhythmogenic right ventricular cardiomyopathy/dysplasia and Brugada syndrome

BACKGROUND

Right ventricular outflow tract ventricular tachycardia (RVOT-VT), arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/ARVD), and Brugada syndrome (BrS) were characterized by arrhythmias originating in the right ventricle, and the pathophysiologic mechanism underlying these arrhythmias has not been fully understood.

METHODS

This study consisted of 40 subjects, including 20 patients with RVOT-VT, 10 patients with BrS, and 10 ARVD patients. The parameters on the signal-averaged electrocardiography (ECG) and the frequency components recorded from the wavelet-transformed ECG were compared between the three groups. Late potentials were positive in none of the patients with RVOT-VT, seven of the patients with BrS, and all of ARVD patients.

RESULTS

In Brugada and ARVD patients, the power of high-frequency components (80-150 Hz) was developed to a greater extent than in RVOT-VT patients. In the power analysis of the high-frequency components between BrS and ARVD, the frequency showing the greatest power was significantly higher in ARVD patients than that in BrS patients (145.4 ± 27.9 Hz vs 81.7 ± 19.9 Hz, P < 0.01).

CONCLUSIONS

High-frequency components were developed in ARVD and BrS, but not in RVOT-VT. The frequency levels showing high power by wavelet analysis obviously differ between ARVD and BrS. Wavelet analysis may provide new insight into unsolved mechanisms in arrhythmogenic right heart disease.

Epsilon-like waves and ventricular conduction abnormalities in subjects with type 1 ECG pattern of Brugada syndrome

BACKGROUND

Previous studies have demonstrated an overlap between the arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) and Brugada syndrome (BS). Conduction delay in the right ventricle has been demonstrated in both entities.

OBJECTIVE

This study investigated specific ARVC/D electrocardiographic (ECG) markers in subjects with spontaneous or drug-induced type 1 ECG pattern of BS.

METHODS

The study population consisted of 47 apparently healthy individuals (38 men, mean age 44.1 ± 13.3 years) with spontaneous (n = 17) or drug-induced (n = 30) type 1 ECG phenotype of BS. The clinical records of these individuals were retrospectively analyzed.

RESULTS

Fifteen subjects (31.9%) were symptomatic, with a history of syncope. A family history of BS or sudden cardiac death was reported in 10 (21.3%) and 8 (17.0%) cases, respectively. Epsilon-like waves in leads V1-V3 were observed in 6 subjects (12.7%). Epsilon-like waves were seen in spontaneous type 1 ECGs in 2 cases and after sodium channel blocking test in 4 cases. In baseline ECGs, localized prolongation (>110 ms) of the QRS complex in leads V1-V3, QRS duration ratio in (V1+V2+V3)/(V4+V5+V6) ≥ 1.2, and prolonged S wave upstroke (>55 ms) in leads V1-V3 were seen in 48.8%, 29.8%, and 40.4% of subjects, respectively. Epsilon-like waves and delayed S wave upstroke were more commonly observed in subjects with family history of BS (P = .014 and P = .038, respectively).

CONCLUSION

Specific ECG markers that reflect ventricular conduction delay in ARVC/D are commonly observed in subjects with spontaneous or drug-induced type 1 ECG pattern of BS as well. These depolarization abnormalities may be related to subtle underlying structural abnormalities.

Epsilon-like electrocardiographic pattern in a patient with Brugada syndrome

Both Brugada syndrome (BrS) and arrhythmogenic right ventricle dysplasia/cardiomyopathy (ARVD/C) can cause repolarization abnormalities in right precordial leads and predispose to sudden cardiac death (SCD) due to ventricular arrhythmias. Although there is controversy over whether BrS is distinct from ARVD/C, it is believed that both are different clinical entities with respect to both the clinical presentation and the genetic predisposition. The coexistence of these two relatively rare clinical entities is also reported, but, some hypothesized that it is more possible that disease of the right ventricular muscle might accentuate the Brugada electrocardiographic pattern. In clinic practice, there may be cases where the dividing line is not so clear. We report a 33-year-old male presenting with recurrent syncope, who has a peculiar pattern of coved-type ST-segment elevation (ST-SE) with epsilon-like wave in right precordial leads.

Mechanism of right precordial ST-segment elevation in structural heart disease: excitation failure by current-to-load mismatch

BACKGROUND

The Brugada sign has been associated with mutations in SCN5A and with right ventricular structural abnormalities. Their role in the Brugada sign and the associated ventricular arrhythmias is unknown.

OBJECTIVE

The purpose of this study was to delineate the role of structural abnormalities and sodium channel dysfunction in the Brugada sign.

METHODS

Activation and repolarization characteristics of the explanted heart of a patient with a loss-of-function mutation in SCN5A (G752R) and dilated cardiomyopathy were determined after induction of right-sided ST-segment elevation by ajmaline. In addition, right ventricular structural discontinuities and sodium channel dysfunction were simulated in a computer model encompassing the heart and thorax.

RESULTS

In the explanted heart, disappearance of local activation in unipolar electrograms at the basal right ventricular epicardium was followed by monophasic ST-segment elevation. The local origin of this phenomenon was confirmed by coaxial electrograms. Neither early repolarization nor late activation correlated with ST-segment elevation. At sites of local ST-segment elevation, the subepicardium was interspersed with adipose tissue and contained more fibrous tissue than either the left ventricle or control hearts. In computer simulations entailing right ventricular structural discontinuities, reduction of sodium channel conductance or size of the gaps between introduced barriers resulted in subepicardial excitation failure or delayed activation by current-to-load mismatch and in the Brugada sign on the ECG.

CONCLUSION

Right ventricular excitation failure and activation delay by current-to-load mismatch in the subepicardium can cause the Brugada sign. Therefore, current-to-load mismatch may underlie the ventricular arrhythmias in patients with the Brugada sign.

Brugada syndrome: recent advances and controversies

The Brugada syndrome, first described as a new clinical entity in 1992, is widely recognized today as a form of inherited sudden cardiac arrest. The past 16 years witnessed a progressive increase in the number of reported cases and a dramatic proliferation of articles serving to define the clinical, genetic, cellular, ionic, and molecular aspects of the disease. This article provides a brief overview of recent advances in our understanding of the clinical presentation and molecular and cellular mechanisms and an update of existing controversies.

The utility of magnetic resonance imaging in the evaluation of arrhythmogenic right ventricular cardiomyopathy

PURPOSE OF REVIEW

Perceptions of the utility of cardiovascular magnetic resonance in the evaluation of arrhythmogenic right ventricular cardiomyopathy have changed considerably in the past decade. This review offers an up-to-date perspective on the diagnostic role of cardiovascular magnetic resonance in the genetics era.

RECENT FINDINGS

Originally hailed as a putative gold standard in arrhythmogenic cardiomyopathy, cardiovascular magnetic resonance has received a more guarded reception lately owing to interobserver variability and lack of standardized protocols. Recent studies have nonetheless affirmed its value as an integral component of the diagnostic work-up. Quantitative volume analysis is relatively robust, but visualization of myocardial fat by spin-echo imaging is less reliable. Interpretation of wall motion abnormalities appears reproducible among expert readers. Emerging data suggest a key role for late gadolinium enhancement in detection of left ventricular involvement.

SUMMARY

Cardiovascular magnetic resonance in arrhythmogenic cardiomyopathy is facilitated by appropriate patient selection and preparation, experienced readers and operators, and a dedicated, comprehensive protocol. Indications for magnetic resonance assessment include proven arrhythmogenic cardiomyopathy in the family, unexplained ventricular arrhythmia, inverted T-waves in the right precordial or lateral leads, and/or family history of sudden cardiac death. Arrhythmia suppression is essential for optimal electrocardiographic triggering and image acquisition.

Different Effect of the Pure Na+ Channel-Blocker Pilsicainide on the ST-Segment Response in the Right Precordial Leads in Patients With Normal Left Ventricular Function

BACKGROUND

The response of the ST-segment in the right precordial leads to Na+ channel blockers in patients without structural heart disease and a typical Brugada-type ECG has not been fully elucidated.

METHODS AND RESULTS

A pilsicainide challenge test was performed in 161 patients and according to recently established ECG criteria and an organized computer algorithm, the ST morphology was classified and the maximum increase in the J wave amplitude (maxDeltaJ) from the standard and high right precordial leads V1-3 was examined. Before the test, subjects exhibiting type 1 ECG in the standard leads were excluded. After administering pilsicainide, type 1 ECGs in the standard leads were observed in 31 cases and a maxDeltaJ of >or=200 microV was observed in 29 cases (23 type 1, 2 type 2/3 and 4 normal ECGs). In the additional higher right precordial leads, type 1 ECGs were observed in 55 cases and a maxDeltaJ of >or=200 microV was observed in 45 cases (42 type 1 and 3 type 2/3 ECGs).

CONCLUSIONS

A maxDeltaJ>or=200 microV induced by pilsicainide, including that measured in the high right precordial leads, was associated with a change mainly to a type 1 ECG.

A case of a concealed type of Brugada syndrome with a J wave and mild ST-segment elevation in the inferolateral leads

We report a patient with a concealed type of Brugada syndrome. The electrocardiogram in the emergency department revealed atrial fibrillation with an almost normal ST segment. Slight electrocardiogram abnormalities of the J wave and mild ST-segment elevation appeared in the inferolateral leads a few days later. Although the ST segment in the right precordial leads, including that recorded from the high intercostal space recording sites, was completely normal, a drug challenge test using pilsicainide revealed a coved-type ST-segment elevation only in a modified V2 lead placed 1 or 2 intercostal spaces higher.

Advances in the diagnostic management of arrhythmogenic right ventricular dysplasia-cardiomyopathy

Latest advances in the diagnostic management of arrhythmogenic right ventricular dysplasia-cardiomyopathy (ARVD/C) confirm that ARVD/C is not a rare disease (one affected in 1000-1250 inhabitants) and is of familial origin in 50-80% of cases. Diagnostic criteria defined in 1994 lead to low rates in the diagnosis of ARVD/C. Progress was made in the definition of diagnostic markers. New criteria of localised right precordial QRS prolongation could be identified. The detection of epsilon potentials could be enhanced by highly amplified and modified recording techniques. Vectorcardiography, signal averaging per lead and electroanatomic voltage mapping might become more important in the future. Cardiac MRI does not represent the single diagnostic test to make the diagnosis of ARVD/C. It remains a promising noninvasive imaging technique with advantages in the evaluation of the right ventricle. After the characterisation of mutations in the plakophilin-2 gene, molecular genetics is going to become an important diagnostic tool. Up to now, unsolved problems exist in the differentiation of ARVD/C and other conditions with ventricular arrhythmias evolving from the right ventricle such as Brugada syndrome and right ventricular outflow tract tachycardia. These problems can be overcome by distinct ECG analysis and the use of imaging techniques. With the help of corrected and modified diagnostic criteria it seems to be possible to identify symptomatic and asymptomatic affected by ARVD/C with predominantly major criteria and only in a minority of cases minor criteria.

Sudden Cardiac Death in the Young: A Strategy for Prevention by Targeted Evaluation

The annual incidence of sudden cardiac death (SCD) in the general population is estimated as 1 in a 1,000. Since survival rates from out-of-hospital cardiac arrests are poor, primary prevention is key to reducing the burden of SCD in the community. Prominent causes of SCD include ischaemic heart disease, anomalous coronary arteries, and the primary myocardial diseases: hypertrophic cardiomyopathy, dilated cardiomyopathy, and ar rhythmogenic right ventricular cardiomyopathy (ARVC). In 4% of sudden deaths in the 16-64 age group, post-mortem examination fails to identify a cause, yielding a default diagnosis of sudden arrhythmic death syndrome (SADS). The inherited arrhythmia syndromes (long QT, short QT, and Brugada syndromes, and familial catecholaminergic polymorphic ventricular tachycardia) may be implicated in SADS, owing to their propensity for producing ventricular tachyarrhythmia in the structurally normal heart. Monogenic disorders therefore predominate as causes of SCD in the young. The advent of effective therapies for these diseases, particularly implantable cardioverter defibrillators, has prompted calls for universal screening to enable timely diagnosis of occult cardiac disease. Since prospective cardiac assessment of the general population is not feasible, the solution may be to target high-risk subgroups, namely, patients with cardiac symptoms, relatives of SCD victims, and competitive athletes. The recommended preliminary work-up includes a 12-lead ECG, signal-averaged ECG, transthoracic echocardiogram, exercise test, and ambulatory ECG monitoring. Cardiovascular magnetic resonance is a useful adjunct in patients with suspected ARVC or anomalous coronary arteries. Provocative challenge with a sodium challenge blocker may be of value in unmasking the Brugada syndrome. Identification of disease-causing mutations in affected individuals facilitates cascade screening of families.

Sodium Channel Variants in Heart Disease: Expanding Horizons

Inherited arrhythmia syndromes have advanced our understanding of cardiac sodium (Na) channel function in health and disease. Long QT syndrome (LQT3) is consistently caused by increased net Na current secondary to inactivation defects, which give rise to persistent Na current. Conversely, various gating changes that ultimately result in reduced Na current may elicit Brugada syndrome, conduction disease, atrial standstill, and sinus node disease. Emerging insights now also link these gating defects to enhanced arrhythmia susceptibility in common, acquired, disease. For instance, action potential prolongation in congestive heart failure may be explained by increased persistent Na current. Of note, recent studies have also linked Na current reduction to structural cardiac defects, notably cardiac fibrosis, dilated cardiomyopathy and, possibly, arrhythmogenic right ventricular cardiomyopathy. These structural changes may also be conducive to (reentrant) arrhythmias. Clearly, these observations highlight the cardiac Na channel as an interesting target for novel therapy strategies.

Right ventricular fibrosis and conduction delay in a patient with clinical signs of Brugada syndrome: a combined electrophysiological, genetic, histopathologic, and computational study

BACKGROUND

The mechanism of ECG changes and arrhythmogenesis in Brugada syndrome (BS) patients is unknown.

METHODS AND RESULTS

A BS patient without clinically detected cardiac structural abnormalities underwent cardiac transplantation for intolerable numbers of implantable cardioverter/defibrillator discharges. The patient's explanted heart was studied electrophysiologically and histopathologically. Whole-cell currents were measured in HEK293 cells expressing wild-type or mutated sodium channels from the patient. The right ventricular outflow tract (RVOT) endocardium showed activation slowing and was the origin of ventricular fibrillation without a transmural repolarization gradient. Conduction restitution was abnormal in the RVOT but normal in the left ventricle. Right ventricular hypertrophy and fibrosis with epicardial fatty infiltration were present. HEK293 cells expressing a G1935S mutation in the gene encoding the cardiac sodium channel exhibited enhanced slow inactivation compared with wild-type channels. Computer simulations demonstrated that conduction slowing in the RVOT might have been the cause of the ECG changes.

CONCLUSIONS

In this patient with BS, conduction slowing based on interstitial fibrosis, but not transmural repolarization differences, caused the ECG signs and was the origin of ventricular fibrillation.

Mechanisms of syncopes in arrhythmogenic right ventricular dysplasia–cardiomyopathy beyond monomorphic ventricular tachycardia

Syncopes appear in 10-20% in arrhythmogenic right ventricular dysplasia-cardiomyopathy (ARVD/C). In the majority of cases sustained or non-sustained monomorphic ventricular tachycardias represent the underlying mechanism of syncope. In other cases the mechanism remains unclear. In 37 patients (23 females, mean age 43.6+/-12.8 years) without detectable and inducible monomorphic ventricular tachycardia, a diagnostic algorithm including repeat ECG, holter monitoring, telemetry, electrophysiological examination, ajmaline challenge, tilt table testing and neurological work-up (EEG, cranial computer tomography) was used in order to identify the mechanism of syncopes. Constant AV block 3 degrees could be found in 3 patients (2 males). Intermittant AV block 2 degrees or 3 degrees could be identified in 3 females. Four males had abnormal Wenckebach point during rapid atrial stimulation, 3 males demonstrate isolated HV interval prolongation. Rapid polymorphic VT and VF could be induced in a young female with ARVD/C. Eight patients (7 females) presented with recurrent syncopes and provocable right precordial ST elevation and right bundle branch block during ajmaline challenge. Three patients had abnormal tilt table testing as the only pathological finding. In one female with intermittent AV block 2 degrees tilt table testing and ajmaline challenge was positive. One female had the diagnosis of focal epilepsia after neurological work-up. In 11 cases the mechanism of syncopes remained unclear. In patients with ARVD/C and syncopes beyond detectable or inducible monomorphic VT, several mechanisms of syncopes could be identified with conduction disease as the predominant finding. These results may help in identifying rare mechanisms of syncopes in ARVD/C.