Brugada phenocopy: new terminology and proposed classification

Yellow phosphorus-induced Brugada phenocopy

BACKGROUND

Metallic phosphides (of aluminum and phosphide) and yellow phosphorus are commonly used rodenticide compounds in developing countries. Toxicity of yellow phosphorus mostly pertains to the liver, kidney, heart, pancreas and the brain. Cardiotoxicity with associated Brugada ECG pattern has been reported only in poisoning with metallic phosphides.

METHODS AND RESULTS

Brugada phenocopy and hepatic dysfunction were observed in a 29-year-old male following yellow phosphorus consumption. He had both type 1 (day1) and type 2 (day2) Brugada patterns in the electrocardiogram, which resolved spontaneously by the third day without hemodynamic compromise.

CONCLUSION

Toxins such as aluminum and zinc phosphide have been reported to induce Brugada ECG patterns due to the generation of phosphine. We report the first case of yellow phosphorus-related Brugada phenocopy, without hemodynamic compromise or malignant arrhythmia.

Brugada-Phenocopy Induced by Propafenone Overdose and Successful Treatment: A Case Report

Background:

Brugada syndrome is an inherited arrhythmogenic disease that may cause sudden cardiac death due to ventricular fibrillation in young adults. Brugada syndrome caused by propafenone intoxication has been noted rarely in the literature. We report a rare case, Brugada phenocopy due to propafenone intoxication and its treatment.

Case Report:

A 15-year-old girl having a seizure was brought to the emergency room. She took 1.5 g propafenone (Rythmol, Abbott, Chicago, IL, USA) for suicidal intention. She had metabolic acidosis. Long QRS interval and ST elevation in leads V₁ through V₃ were seen on electrocardiography. After bicarbonate infusion for 4 hours, haemodynamic and neurologic findings were recovered, and all electrocardiography abnormalities disappeared. The Brugada-like electrocardiography pattern was not recognized in her surface and 24-hour Holter electrocardiography at follow-up. Ajmaline challenge test was negative 2 weeks later.

Conclusion:

Absence of symptoms and documented ventricular tachycardia, negative challenge test, and a negative family history demonstrated that the Brugada phenocopy was a transient finding in this case and related to propafenone intoxication.

Depolarization of the conductance-voltage relationship in the NaV1.5 mutant, E1784K, is due to altered fast inactivation

E1784K is the most common mixed long QT syndrome/Brugada syndrome mutant in the cardiac voltage-gated sodium channel NaV1.5. E1784K shifts the midpoint of the channel conductance-voltage relationship to more depolarized membrane potentials and accelerates the rate of channel fast inactivation. The depolarizing shift in the midpoint of the conductance curve in E1784K is exacerbated by low extracellular pH. We tested whether the E1784K mutant shifts the channel conductance curve to more depolarized membrane potentials by affecting the channel voltage-sensors. We measured ionic currents and gating currents at pH 7.4 and pH 6.0 in Xenopus laevis oocytes. Contrary to our expectation, the movement of gating charges is shifted to more hyperpolarized membrane potentials by E1784K. Voltage-clamp fluorimetry experiments show that this gating charge shift is due to the movement of the DIVS4 voltage-sensor being shifted to more hyperpolarized membrane potentials. Using a model and experiments on fast inactivation-deficient channels, we show that changes to the rate and voltage-dependence of fast inactivation are sufficient to shift the conductance curve in E1784K. Our results localize the effects of E1784K to DIVS4, and provide novel insight into the role of the DIV-VSD in regulating the voltage-dependencies of activation and fast inactivation.

Brugada syndrome, Brugada phenocopy or none?

Brugada syndrome is a form of inherited arrhythmia syndrome characterized by a distinct ST-segment elevation in the right precordial leads. Brugada phenocopies are clinical entities that present with an electrocardiographic pattern identical to Brugada syndrome and may obey to various clinical conditions. We present a case of a suicidal attempt using a high dose of propafenone causing a Brugada-type electrocardiographic pattern. Is this a Brugada syndrome case, a Brugada phenocopy or something else?

Brugada phenocopy in a patient with acute pulmonary embolism presenting with recurrent syncope

Brugada phenocopy (BrP) refers to a group of clinical conditions that have etiologies distinct from Brugada syndrome (BrS). Although both demonstrate features of ST-segment elevation in the right precordial leads on the electrocardiogram (ECG), one must be distinguished from the other as their treatment options are different. We report a male patient who presented with recurrent syncope with a Brugada and a S1Q3T3 pattern on the ECG. Acute pulmonary embolism (APE) complicated by BrS was suspected. Twenty-four hours Holter monitoring did not demonstrate any evidence of ventricular arrhythmias. Computed tomography pulmonary angiogram confirmed the presence of an APE. He was treated with low molecular weight heparin and a repeat ECG taken the next day showed resolution of the Brugada and S1Q3T3 patterns. This case report illustrates that APE and BrS can present with similar clinical and electrocardiographic features of recurrent syncope and Brugada pattern, respectively.

Right Ventricular Compression Mimicking Brugada-Like Electrocardiogram in a Patient with Recurrent Pectus Excavatum

Pectus excavatum (PE), the most common skeletal anomaly of chest wall, sometimes requires a surgical correction but recurrent PE is not uncommon. PE usually has a benign course; however, this chest deformity may be associated with symptomatic tachyarrhythmias due to mechanical compression. We report a case of a patient with recurrent PE after surgical correction presenting with palpitation and electrocardiogram (ECG) showing ST-segment elevation on the right precordial leads, which could be mistaken for a Brugada syndrome (BrS).

Myotonic dystrophy and Brugada syndrome: A common pathophysiologic pathway?

Type 1 myotonic dystrophy (DM1) is a hereditary neuromuscular disease affecting multiple organs in human adults. Here we report a 42-year-old man diagnosed with DM1. Having a history of progressive muscular weakness and gradual loss of visual acuity, he was referred to us by his ophthalmologist for risk assessment of undergoing cataract surgery. Cardiology workup revealed type 1 Brugada ECG pattern, positive late potentials and inducible ventricular fibrillation in an electrophysiology study. Literature review revealed that those ECG changes may be observed in DM1, suggesting that DM1 and Brugada syndrome may share a common pathophysiologic pathway.

Brugada Syndrome: Evolving Insights and Emerging Treatment Strategies

Brugada syndrome (BrS) is a rare inherited arrhythmia disorder associated with sudden cardiac death secondary to malignant ventricular arrhythmias. Since its first mention approximately 25 years ago, major strides have been made towards unraveling the condition's genetic and mechanistic underpinnings. Despite considerable progress, however, gaps in the understanding of BrS continue to persist, and clinical management of affected individuals remains challenging. Identification of an underlying genetic culprit continues to be elusive in the majority of patients, while discord regarding the condition's underlying pathophysiology also persists, with strong lines of evidence present for both the "depolarization" and "repolarization" hypotheses. Exciting new therapeutic options hold significant promise, including substrate-based catheter ablation and the subcutaneous implantable cardioverter-defibrillator, although the decision of when to intervene in the cases of asymptomatic patients remains unclear. Provided that the risk of events in BrS is not truly stochastic, distinct sub-phenotypes of the condition, possessing variable levels of arrhythmic risk, may exist, and their identification may lead to the improved care of BrS patients and their families.

Brugada Phenocopy Induced by Electrolyte Disorder: A Transient Electrocardiographic Sign

Brugada syndrome (BrS) is an important cause of sudden cardiac death (SCD) with well-defined ST-segment elevation patterns on V1 -V3 . Observation of BrS-Type-electrocardiogram (ECG) patterns in medical conditions without true BrS is called "Brugada Phenocopy" (BrP). We present a case of 61-year-old male patient with hyperkalemia, hyponatremia, and BrS-Type-1 ECG pattern in the setting of acute postrenal failure. He was denying any syncope or family history of SCD. With normalization of electrolyte levels, BrS-Type-1-ECG resolved. Electrolyte disturbances are one of the most common reasons of BrP. Being aware of BrPs and differentiating from an unmasked BrS-ECG pattern could prevent patients from lethal consequences and unnecessary treatments.

Brugada Phenocopy as a Dynamic Electrocardiographic Pattern during Acute Anterior Myocardial Infarction

Brugada phenocopies represent some unusual clinical cases with identical characteristics to Brugada syndrome (BrS) elicited by various clinical circumstances. We report the case of a woman exhibiting "Brugada Phenocopy" during an acute anterior myocardial infarction, highlighting differential diagnosis with true BrS and discussing possible mechanisms underlying its dynamic ECG pattern.

Brugada syndrome and Brugada phenocopy. The importance of a differential diagnosis

To date Brugada syndrome (BrS) is considered a primary electrical heart disease and the diagnosis is based on precise clinical and electrocardiographic features. Many other diseases and conditions can lead to a Brugada-like ECG pattern but the vast majority of patients with BrS possess a structurally normal heart, which is consistent with the notion that this is a primary electrical heart disease. Presently, the terminology used in the literature to describe Brugada type 1 ECG pattern induced in patients without BrS is diverse and variable. Brugada phenocopies (BrP) are clinical entities that present with identical ECG patterns to those of true BrS but are elicited by various other clinical circumstances. They form a group of heterogeneous conditions that are perhaps the most difficult to differentiate from true congenital BrS due to identical ECG patterns and recently has been proposed an updated classification of conditions that may induce BrP and many criteria useful to differentiate BrP from BrS. A systematic diagnostic approach is crucial to avoid diagnostic errors that involve expenditure of time and resources, but above all it is useful to avoid to send patients without a real BrS to inopportune diagnostic and therapeutic paths that are sometimes burdened by considerable risks.

All that looks like "Brugada" is not "Brugada": Case series of Brugada phenocopy caused by hyponatremia

Brugada syndrome (BS), a life-threatening channelopathy associated with reduced inward sodium current due to dysfunctional sodium channels, is characterized by ST-segment elevation with downsloping “coved type” (type 1) or “saddle back” (type 2) pattern in V1–V3 precordial chest leads (1, 2). Brugada phenocopy, a term describing conditions inducing Brugada-like pattern of electrocardiogram (EKG) manifestations in patients without true BS, is an emerging condition (3). We describe a case series of Brugada phenocopy with hyponatremia.

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

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

New methodologies for measuring Brugada ECG patterns cannot differentiate the ECG pattern of Brugada syndrome from Brugada phenocopy

BACKGROUND

Brugada phenocopies (BrP) are clinical entities characterized by ECG patterns that are identical to true Brugada syndrome (BrS), but are elicited by various clinical circumstances. A recent study demonstrated that the patterns of BrP and BrS are indistinguishable under the naked eye, thereby validating the concept that the patterns are identical.

OBJECTIVE

The aim of our study was to determine whether recently developed ECG criteria would allow for discrimination between type-2 BrS ECG pattern and type-2 BrP ECG pattern.

METHODS

Ten ECGs from confirmed BrS (aborted sudden death, transformation into type 1 upon sodium channel blocking test and/or ventricular arrhythmias, positive genetics) cases and 9 ECGs from confirmed BrP were included in the study. Surface 12-lead ECGs were scanned, saved in JPEG format for blind measurement of two values: (i) β-angle; and (ii) the base of the triangle. Cut-off values of ≥58° for the β-angle and ≥4mm for the base of the triangle were used to determine the BrS ECG pattern.

RESULTS

Mean values for the β-angle in leads V1 and V2 were 66.7±25.5 and 55.4±28.1 for BrS and 54.1±26.5 and 43.1±16.1 for BrP respectively (p=NS). Mean values for the base of the triangle in V1 and V2 were 7.5±3.9 and 5.7±3.9 for BrS and 5.6±3.2 and 4.7±2.7 for BrP respectively (p=NS). The β-angle had a sensitivity of 60%, specificity of 78% (LR+ 2.7, LR- 0.5). The base of the triangle had a sensitivity of 80%, specificity of 40% (LR+ 1.4, LR- 0.5).

CONCLUSIONS

New ECG criteria presented relatively low sensitivity and specificity, positive and negative predictive values to discriminate between BrS and BrP ECG patterns, providing further evidence that the two patterns are identical.

Methods for Improving the Diagnosis of a Brugada ECG Pattern

Brugada syndrome (BrS) is an inherited channelopathy that predisposes individuals to malignant arrhythmias and can lead to sudden cardiac death. The condition is characterized by two electrocardiography (ECG) patterns: the type-1 or "coved" ECG and the type-2 or "saddleback" ECG. Although the type-1 Brugada ECG pattern is diagnostic for the condition, the type-2 Brugada ECG pattern requires differential diagnosis from conditions that produce a similar morphology. In this article, we present a case that is suspicious but not diagnostic for BrS and discuss the application of ECG methodologies for increasing or decreasing suspicion for a diagnosis of BrS.

Expert cardiologists cannot distinguish between Brugada phenocopy and Brugada syndrome electrocardiogram patterns

AIMS

Brugada phenocopies (BrPs) are electrocardiogram (ECG) patterns that are identical to true Brugada syndrome (BrS) but are induced by various clinical conditions. The concept that both ECG patterns are visually identical has not been formally demonstrated. The aim of our study was to determine if experts on BrS were able to accurately distinguish between the BrS and BrP ECG patterns.

METHODS AND RESULTS

Six ECGs from confirmed cases of BrS and six ECGs from previously published cases of BrP were included in the study. Surface 12-lead ECGs were scanned, saved in JPEG format, and sent to 10 international experts on BrS for evaluation (no clinical history provided). Evaluators were asked to label each case as a Brugada ECG pattern or non-Brugada ECG pattern by visual interpretation alone. The overall accuracy was 53 ± 33% for all cases. Within the BrS cases, the mean accuracy was 63 ± 34% and within the BrP cases, the mean accuracy was 43 ± 33%. Intra-observer repeatability was moderate (κ = 0.56) and inter-observer agreement was fair (κ = 0.36) while evaluator accuracy vs. the true diagnosis was only marginally better than chance (κ = 0.05). Similarly, diagnostic operating characteristics were poor (sensitivity 62%, specificity 43%, +LR 1.1, -LR 0.9).

CONCLUSION

Our results provide strong evidence that BrP and BrS ECG patterns are visually identical and indistinguishable. These findings support the use of systematic diagnostic criteria for differentiating BrP vs. BrS as an erroneous diagnosis may have a negative impact on patient morbidity and mortality.

Massive pulmonary embolism mimicking electrocardiographic pattern of Brugada syndrome

Brugada syndrome is an inherited heart disease without structural abnormalities that is thought to arise as a result of accelerated inactivation of Na channels and predominance of transient outward K current to generate a voltage gradient in the right ventricular layers. Brugada syndrome occurs in patients with structurally normal heart and predisposes patients to malignant ventricular arrhythmias. Acute pulmonary embolism has been associated with a variety of electrocardiograms,and rarely, it may mimic electrocardiographic pattern of Brugada syndrome and this condition was defined as Brugada phenocopy.

[Brugada ECG]

The Brugada syndrome (BrS) is characterized by a typical electrocardiogram (ECG) pattern of right precordial ST-segment elevation and the cardinal symptoms syncope and sudden cardiac death as clinical correlate of malignant ventricular arrhythmias in young adults without structural heart disease. The diagnosis of a type 1 Brugada-ECG is based on the documentation of a coved-type (≥ 0.2 mV) ST elevation followed by a negative T wave. The use of the ECG criteria postulated in the consensus of 2012 is helpful to distinguish between saddleback-type 2 (or type 3) J point/ST elevation and incomplete right bundle branch block. Spontaneous or drug-induced type 1 ST elevation can frequently only be detected in a single right precordial lead (V1 or V2), occurs sometimes together with a type 2 (or type 3) pattern in one and the same 12-lead ECG and can sometimes only be seen in modified right precordial leads. The ST elevation is less pronounced in females. Spontaneous and exercise-induced type 1 ST elevation, fragmented QRS complex, prolonged PR interval (> 200 ms), QRS prolongation in V2 (≥ 120 ms) and markers of an increased heterogeneity of ventricular repolarization are associated with an increased arrhythmic risk. The occurrence of spontaneous or dynamic type 1 ST elevation, a macroscopic T wave alternans or pronounced inferior (lateral) J point/ST elevation are signs of acute electrical instability.

Brugada phenocopies are the leading differential diagnosis of Brugada syndrome

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Brugada ECG patterns in athletes

Brugada syndrome is responsible for up to 4% of all sudden cardiac deaths worldwide and up to 20% of sudden cardiac deaths in patients with structurally normal hearts. Heterogeneity of repolarization and depolarization, particularly over the right ventricle and the outflow tract, is responsible for the arrhythmogenic substrate. The coved Type I ECG pattern is considered diagnostic of the syndrome but its prevalence is very low. Distinguishing between a saddle back Type 2 Brugada pattern and one of many "Brugada-like" patterns presents challenges especially in athletes. A number of criteria have been proposed to assess Brugada ECG patterns. Proper precordial ECG lead placement is paramount. This paper reviews Brugada syndrome, Brugada ECG patterns, and recently proposed criteria. Recommendations for evaluating a Brugada ECG pattern are provided.

Electrocardiographic methods for diagnosis and risk stratification in the Brugada syndrome

The Brugada syndrome (BrS) is a malignant, genetically-determined, arrhythmic syndrome manifesting as syncope or sudden cardiac death (SCD) in individuals with structurally normal hearts. The diagnosis of the BrS is mainly based on the presence of a spontaneous or Na + channel blocker induced characteristic, electrocardiographic (ECG) pattern (type 1 or coved Brugada ECG pattern) typically seen in leads V1 and V2 recorded from the 4th to 2nd intercostal (i.c.) spaces. This pattern needs to be distinguished from similar ECG changes due to other causes (Brugada ECG phenocopies). This review focuses mainly on the ECG-based methods for diagnosis and arrhythmia risk assessment in the BrS. Presently, the main unresolved clinical problem is the identification of those patients at high risk of SCD who need implantable cardioverter-defibrillator (ICD), which is the only therapy with proven efficacy. Current guidelines recommend ICD implantation only in patients with spontaneous type 1 ECG pattern, and either history of aborted cardiac arrest or documented sustained VT (class I), or syncope of arrhythmic origin (class IIa) because they are at high risk of recurrent arrhythmic events (up to 10% or more annually for those with aborted cardiac arrest). The majority of BrS patients are asymptomatic when diagnosed and considered to have low risk (around 0.5% annually) and therefore not indicated for ICD. The majority of SCD victims in the BrS, however, had no symptoms prior to the fatal event and therefore were not protected with an ICD. While some ECG markers such as QRS fragmentation, infero-lateral early repolarisation, and abnormal late potentials on signal-averaged ECG are known to be linked to increased arrhythmic risk, they are not sufficiently sensitive or specific. Potential novel ECG-based strategies for risk stratification are discussed based on computerised methods for depolarisation and repolarisation analysis, a composite approach targeting several major components of ventricular arrhythmogenesis, and the collection of large digital ECG databases in genotyped BrS patients and their relatives.

The Brugada Syndrome - Diagnosis, Clinical Implications and Risk Stratification

The Brugada syndrome (BrS) is a hereditary arrhythmic syndrome manifesting as syncope or sudden cardiac death (SCD) in individuals without overt structural heart disease. Currently, its diagnosis is mainly based on the presence of a spontaneous or Na+-channel blocker induced so-called "type 1" Brugada electrocardiographic (ECG) pattern typically seen in leads V1 and V2 recorded from the 4th to 2nd intercostal spaces. Presently the main unresolved clinical problem in the BrS is the identification of patients at high risk of SCD who need implantable cardioverter-defibrillator (ICD). Current guidelines recommend ICD implantation only in patients with spontaneous type 1 ECG pattern and either history of aborted cardiac arrest or documented sustained ventricular tachycardia (class I) or syncope of arrhythmic origin (class IIa) because they are at high risk of recurrent arrhythmias. However, the majority of BrS patients are asymptomatic when diagnosed and have generally low risk (0.5 % annually or lower) and therefore are not indicated for ICD. Most of SCD victims in the BrS have had no symptoms prior to the fatal event and therefore were not protected with an ICD. Currently there are no reliable methods to identify these potential victims of SCD. Although some ECG markers such as QRS fragmentation and infero-lateral early repolarisation have been demonstrated to signify increased arrhythmic risk their value still needs to be confirmed in large prospective studies. Novel risk assessment strategies need to be developed based on computerised quantitative ECG analysis of large digital ECG databases in patients with BrS and their relatives, and combined assessment of the most important factors of ventricular arrhythmogenesis.