Brugada phenocopy: A new electrocardiogram phenomenon

The many faces of takotsubo syndrome: A review

Takotsubo syndrome is a state of an acute heart failure featuring reversible left ventricular dysfunction. In recent years, the incidence of Takotsubo syndrome has risen 8-fold. In this case series and literature review, we present the rare presentations or complications of Takotsubo syndrome and highlight diagnostic or management strategies. We aim to raise the awareness on the pathologic spectrum of takotsubo syndrome for the clinicians encountering this challenging diagnosis.

A rare case with melatonin-induced on top of alcohol intoxication Brugada type 2 pattern

Brugada syndrome (BrS), a genetically inherited ion channelopathy, has been linked to a considerable number of unexplained sudden cardiac deaths in patients without structural heart defects, and Brugada phenocopy (BrP) is a condition where there is an identical electrocardiogram (ECG) pattern to a congenital BrS, but this is due to other reversible etiologies. A 37-year-old male patient with a documented history of hypertension presented with vomiting after taking 43, 10 mg, melatonin pills and binge drinking locally made alcohol 2 days before. ECG showed right ventricular conduction delay with a "saddleback" appearance, with the J point elevated more than 2 mm and the terminal portion of the ST-segment elevated more than 1 mm in leads V1 and/or V2. Which returned to normal after a few hours. The association between the use of melatonin and the finding of the Brugada pattern (BP) in a patient with normal heart structure or abnormal ECGs has been documented in much literature, and although no official melatonin dosage is recommended for adults, melatonin has been reported to cause and protect from arrhythmias through different mechanisms. In our patient, after alcohol intoxication was ruled out as a cause, melatonin was the only significant risk factor related to his ECG findings. The BP can be found in patients with otherwise normal heart structure and ECG records, and an overdose of melatonin, which is used as an over-the-counter sleep medication, was found to be a possible cause of finding this pattern in these patients after excluding other known causes.

Subepicardial Cardiomyopathy: A Disease Underlying J-Wave Syndromes and Idiopathic Ventricular Fibrillation

Brugada syndrome (BrS), early repolarization syndrome (ERS), and idiopathic ventricular fibrillation (iVF) have long been considered primary electrical disorders associated with malignant ventricular arrhythmia and sudden cardiac death. However, recent studies have revealed the presence of subtle microstructural abnormalities of the extracellular matrix in some cases of BrS, ERS, and iVF, particularly within right ventricular subepicardial myocardium. Substrate-based ablation within this region has been shown to ameliorate the electrocardiographic phenotype and to reduce arrhythmia frequency in BrS. Patients with ERS and iVF may also exhibit low-voltage and fractionated electrograms in the ventricular subepicardial myocardium, which can be treated with ablation. A significant proportion of patients with BrS and ERS, as well as some iVF survivors, harbor pathogenic variants in the voltage-gated sodium channel gene, SCN5A, but the majority of genetic susceptibility of these disorders is likely to be polygenic. Here, we postulate that BrS, ERS, and iVF may form part of a spectrum of subtle subepicardial cardiomyopathy. We propose that impaired sodium current, along with genetic and environmental susceptibility, precipitates a reduction in epicardial conduction reserve, facilitating current-to-load mismatch at sites of structural discontinuity, giving rise to electrocardiographic changes and the arrhythmogenic substrate.

Cascade screening can be life-saving: a family with multiple cases of brugada syndrome and sudden cardiac death

Brugada syndrome (BrS) may cause a spectrum of symptoms from asymptomatic patients to those who experience cardiac arrest and sudden cardiac death. The diagnosis is confirmed after observation of type I Brugada pattern on the electrocardiogram. Following the diagnosis, risk stratification can help select therapeutic options. Cascade screening should be started to find other family members with BrS. We present a 41-year-old woman diagnosed with BrS, and cascade screening of her relatives unveiled a pedigree of BrS among their family.

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.

A Case of Multivessel Coronary Artery Disease and Anomalous Origin of the Right Coronary Artery With a Malignant Course Presenting With Non-exertional Chest Discomfort and Brugada Phenocopy

Coronary artery anomalies (CAAs) are an uncommon cause of chest pain in the younger population. Misdiagnosis can be detrimental and lead to sudden cardiac deaths. We present a 62-year-old male with a past medical history significant for chest pain history with a workup in 2001 presumed to be non-cardiac in origin from bronchial asthma. He presented from a Micronesian Island for the evaluation of non-exertional chest discomfort. Further workup showed a Brugada type I pattern on ECG and ST wave depressions on anterolateral and inferior leads with associated AVR elevation on exercise stress testing. Further ischemic workup with coronary angiography revealed right dominant circulation with three-vessel coronary artery disease (CAD), including mid-left anterior descending (LAD) artery chronic total occlusion (CTO) with the right to left collaterals, left circumflex, and right coronary artery (RCA) with the accompanied anomalous origin of RCA. The patient underwent surgical correction of the anomalous RCA and coronary artery bypass grafting for the multi-vessel CAD. CAAs are usually found incidentally during ischemic workups similar to this case. Patients with CAAs can be managed conservatively with caution regarding physical activity. However, high-risk patients will warrant surgical treatment to avoid sudden cardiac death. The diagnosis of CAAs can be challenging and prone to misdiagnosis and maltreatment. It may be beneficial to pursue this in younger patients with ischemia-like symptoms. Further studies should be performed to identify the true incidence and guide medical practitioners regarding the risks, costs, and benefits of diagnosing and surgically treating CAAs in the general population.

A dynamic Brugada sign due to left anterior descending coronary artery occlusion

Brugada phenocopies (BrP) include several conditions with a common electrocardiographic (ECG) pattern that are indistinguishable from classical Brugada syndrome (BrS). In this report, we describe two cases of acute myocardial infarction (AMI) presenting as BrP. The majority of cases of BrP in AMI have been reported due to right coronary artery (RCA) occlusion. Rarely, the left anterior descending artery (LAD) is incriminated as the cause. In both our cases of BrP, LAD was the culprit vessel.

Italian Cardiological Guidelines (COCIS) for Competitive Sport Eligibility in athletes with heart disease: update 2020

Since 1989, SIC Sport and a FMSI, in partnership with leading Italian Cardiological Scientific Associations (ANCE, ANMCO and SIC) have produced Cardiological Guidelines for Completive Sports Eligibility for athletes with heart disease (COCIS -- 1989, 1995, 2003, 2009 and 2017). The English version of the Italian Cardiological Guidelines for Competitive Sports Eligibility for athletes with heart disease was published in 2013 in this Journal. This publication is an update with respect to the document previously published in English in 2013. It includes the principal innovations that have emerged over recent years, and is divided into five main chapters: arrhythmias, ion channel disorders, congenital heart diseases, acquired valve diseases, cardiomyopathies, myocarditis and pericarditis and ischemic heart disease. Wherever no new data have been introduced with respect to the 2013 publication, please refer to the previous version. This document is intended to complement recent European and American guidelines but an important difference should be noted. The European and American guidelines indicate good practice for people engaging in physical activity at various levels, not only at the competitive level. In contrast, the COCIS guidelines refer specifically to competitive athletes in various sports including those with high cardiovascular stress. This explains why Italian guidelines are more restrictive than European and USA ones. COCIS guidelines address 'sports doctors' who, in Italy, must certify fitness to participate in competitive sports. In Italy, this certificate is essential for participating in any competition.

Type 2 Brugada Electrocardiogram Pattern Due to Supra-Therapeutic Phenytoin Level

Brugada syndrome (BS) is a hereditary cardiac disease leading to sudden cardiac death. It does not display any structural cardiac abnormalities. It was first described in 1992, as the syndrome of ‘right bundle branch block, persistent ST segment elevation, and sudden death.’ Brugada phenocopy (BP) is a relatively new term used to describe electrocardiogram (ECG) patterns that resemble BS but are due to other reversible causes such as electrolyte abnormalities, fever, cocaine or alcohol intoxication, and side effect of certain medications such as sodium channel blockers, beta blockers, antidepressants, alpha adrenergic blockers, etc. Earlier studies have shown that patients taking sodium channel blocking antiepileptic drugs (AEDs) especially phenytoin can have Brugada type 1 like ECG pattern. Previously, type 2 ECG pattern secondary to supra-therapeutic phenytoin level has not been described. We describe a case with type 2 Brugada ECG pattern due to supra-therapeutic phenytoin level; the ECG pattern completely resolved following lowering the phenytoin to a therapeutic level. These patients need special considerations in ED management, disposition, and follow-up.

Hyperkalemia mimicking brugada pattern in electrocardiogram: A rare case report from Nepal

Hyperkalemia is one of the dangerous complications of renal impairment (acute kidney injury or chronic kidney disease). Hyperkalemia may present with the electrocardiogram (ECG) changes as nonspecific repolarization abnormalities. Here, we report a case of AKI with hyperkalemia and the Brugada pattern of ECG, which reverted to normal after effective management of hyperkalemia. A 55-year-old male reported to the Emergency Department of National Academy of Medical Sciences (Bir Hospital) with injuries in his lower limbs and spine after he had met an accident two days back. He also had decreased urine output for the last one day. On physical examination, he had injuries in the spine and lower limbs. His laboratory investigations showed impaired renal function parameters with serum sodium 130 mEq/L and serum potassium of 7.3 mEq/L. His ECG was consistent with Brugada pattern. Patient was treated with 10% calcium gluconate, insulin and dextrose, salbutamol nebulization, and sodium polystyrene sulfonate till hemodialysis was initiated. Hyperkalemia and acidosis can manifest with the Brugada pattern in ECG. Thus, a careful evaluation of hyperkalemia and its treatment must be instituted in such an ECG pattern.

Importance of thorough investigation in a patient presenting with recurrent collapse and ST elevation

There is increasing literature to suggest numerous subgroups of Brugada syndrome (BrS), including those with ST elevation in the lateral or inferior leads. We present a case of a patient presenting with recurrent collapse and inferior ST elevation degenerating to ventricular fibrillation and ultimately leading to a diagnosis of BrS.

Hyperkalemia induced Brugada phenocopy

We illustrate the case Brugada Type 1 pattern on electrocardiogram in a setting of hyperkalemia, changes which were reversible following normalization of serum potassium levels. Although Brugada Type 1 syndrome is associated with sudden cardiac death, a quick search for alternate reversible pathology is essential to timely management and avoid unnecessary cardiac intervention.

The Brugada Type 1 Electrocardiogram and Ventricular Tachycardia With High-Dose Amitriptyline

A 32-year-old woman with anorexia nervosa experienced ventricular tachycardia while on therapeutic-dose amitriptyline despite normal blood tests, imaging, and intracardiac recordings. Electrocardiograms over several years featured the Type 1 Brugada pattern. Careful electrocardiogram monitoring should be made if using high doses of amitriptyline, especially in those with low body weight. (Level of Difficulty: Intermediate.).

The Heart in Diabetic Ketoacidosis: A Narrative Review Focusing on the Acute Cardiac Effects and Electrocardiographic Abnormalities

Diabetic ketoacidosis (DKA) is a serious complication of diabetes mellitus. Hyperglycemia, acidosis, and electrolyte imbalances can directly affect the heart by inducing toxicity, impairing myocardial blood flow, autonomic dysfunction, and altering activation and conduction of electrical impulses throughout the heart, increasing the risk of arrhythmias and ischemia. The electrocardiogram is useful in monitoring patients during and after an episode of DKA, as it allows the detection of arrhythmias and guides metabolic correction. Unfortunately, reports on electrocardiographic abnormalities in patients with DKA are lacking. We found two electrocardiographic patterns that are frequently reported in the literature: a pseudo-myocardial infarction and a Brugada Phenocopy. Both are associated with DKA metabolic anomalies and they resolve after treatment. Because of their clinical relevance and the challenge they represent for clinicians, we analyzed the clinical characteristics of these patients and the mechanisms involved in these electrocardiographic findings.

Brugada phenocopy induced by consumption of yellow oleander seeds - A case report

Brugada phenocopy is a brugada-like pattern in ECG seen in some diseases without an inherited channelopathy. The causes of brugada phenocopy are usually reversible. Once the reversible condition resolves, the ECG pattern disappears. There are many conditions that cause brugada phenocopy like myocardial infarction, hyperkalemia etc. Here we report a case of brugada phenocopy induced by consumption of yellow oleander seeds (T. Peruviana).

Acute Pericarditis-Induced Brugada Phenocopy: A Case Report and Review of the Literature

Brugada phenocopies are interesting clinical entities with electrocardiographic (ECG) patterns indistinguishable from the inherited Brugada syndrome. In patients with Brugada phenocopies, these ECG patterns are expected to resolve with resolution of the underlying condition.

Pathophysiology of Hyperkalemia Presenting as Brugada Pattern on Electrocardiogram (ECG)

BACKGROUND Brugada phenocopies (BrP) are clinical and electrocardiographic (ECG) entities elicited by reversible medical conditions speculated to have pathogenesis rooted in ion current imbalances or conduction delays within the myocardial wall. During an inciting pathologic condition, it produces ECG patterns identical to those of congenitally-acquired Brugada syndrome and subsequently returns to normal ECG patterns upon resolution of the medical condition. This case report describes a 26-year-old man presenting to the Emergency Department (ED) for suspected heroin overdose with a rare ECG consistent with BrP secondary to acute hyperkalemia. CASE REPORT A 26-year-old man with a history of substance abuse and a seizure disorder presented to the ED for acute encephalopathy secondary to a heroin overdose complicated by severe rhabdomyolysis and acute renal failure. Laboratory investigations showed acute hyperkalemia (potassium of 7.2 mmol/L) in addition to an elevated creatine kinase, severe transaminitis, and elevated creatinine. His ECG on admission revealed Brugada-like changes in leads V1-V2, with subsequent resolution upon bicarbonate administration and normalization of potassium. After initial stabilization, the patient was admitted to the Intensive Care Unit (ICU). His rhabdomyolysis and acute kidney injury improved after copious rehydration. He was found to have community-acquired pneumonia, with a negative infectious disease workup, that improved with antibiotics. Upon resolution of his hypoxemic respiratory failure and improvement in mentation, he was discharged from the hospital. CONCLUSIONS Our case report adds to the growing literature on BrP and highlights the importance of recognizing its characteristic ECG pattern as a unique presentation of a common electrolyte derangement.

Brugada Phenocopy Induced by a Lethal Methanol Intoxication

Brugada phenocopies (BrP) are clinical entities that present with an ECG pattern identical to either the type 1 or type 2 Brugada pattern without true congenital Brugada syndrome. This ECG pattern is associated with an identifiable condition and normalizes upon resolution or treatment of the underlying cause. We present a case of a 54-year-old man with extreme metabolic acidosis, hyperkalaemia and a Brugada type 1 ECG pattern in the setting of a suicidal methanol (MeOH) poisoning. Upon correction of these metabolic derangements with bicarbonate infusions and continuous veno-venous haemodiafiltration (CVVH), the Brugada type 1 ECG pattern normalized. Unfortunately, the patient developed signs of cerebral herniation followed by brain death and died on the first day of ICU admission.

Pathogenesis and management of Brugada syndrome in schizophrenia: A scoping review

CONTEXT

Excess cardiovascular morbidity and an increased prevalence of sudden cardiac death (SCD) contributes to premature mortality in schizophrenia. Brugada syndrome (BrS) is an important but underrecognized cause of SCD. It is more commonly seen in schizophrenia than in general population controls.

METHODS

We conducted a scoping review to describe the pathogenesis of BrS in schizophrenia and to identify the psychotropic medications that increase the risk of unmasking BrS and associated ventricular arrhythmias resulting in SCD.

FINDINGS

Schizophrenia and BrS share similar calcium channel abnormalities, which may result in aberrant myocardial conductivity. It remains uncertain if there is a genetic pre-disposition for BrS in a subset of patients with schizophrenia. However, the unmasking of Brugada ECG patterns with the use of certain antipsychotics and antidepressants increases the risk of precipitating SCD, independent of QT prolongation.

CONCLUSIONS AND FUTURE DIRECTIONS

Specific cardiology assessment and interventions may be required for the congenital or unmasked Brugada ECG pattern in schizophrenia. The current long-term standard of care for BrS is an implantable cardioverter defibrillator (ICD), but post-implantation psychological effects must be considered. Careful use of antipsychotic and other psychotropic medications is necessary to minimize proarrhythmic effects due to impact on cardiac sodium and calcium ion channels. When prescribing such drugs to patients with schizophrenia, clinicians should be mindful of the potentially fatal unmasking of Brugada ECG patterns and how to manage it. We present recommendations for psychiatrists managing this patient population.

Supranormal heart rate during peak exercise stress test triggering type-1 Brugada ECG pattern

We present a remarkable maximal capacity exercise test of a 52-year-old patient diagnosed with Brugada syndrome (BrS). As the patient reaches a supranormal sinus heart rate, the type-1 electrocardiogram pattern of BrS appeared and then disappeared immediately after cessation of exercise.

Wolff-Parkinson-White, Brugada phenocopy, and flecainide toxicity: All in one patient

Accessory pathway Wolff-Parkinson-white is sometimes not manifested till later in life, as the conduction properties of AV node become slower, other mechanisms are also possible. Brugada pattern on EKG can be associated with various underlying clinical conditions, such as mechanical compression of RVOT by tumors. It is essential to have high index of suspicion for flecainide toxicity when encountering arrhythmias in patients taking the drug.

Link between Brugada phenocopy and myocardial ischemia: Results from the International Registry on Brugada Phenocopy

BACKGROUND

Brugada phenocopies clinical entities that have indistinguishable electrocardiographic (ECG) patterns from true congenital Brugada syndrome. However, they are induced by other clinical circumstances such as myocardial ischemia. The purpose of our study was to examine the clinical features and pathogenesis of ischemia-induced Brugada phenocopy (BrP).

METHODS

Data from 17 cases of ischemia-induced BrP were collected from the International Registry (www.brugadaphenocopy.com). Data were extracted from these publications and authors were contacted to provide further insight into each case.

RESULTS

Of the patients included in this study, 71% were male. Mean age was 59 ± 11 years (range: 38-76). Type-1 Brugada ECG pattern occurred in 15/17 (88%) of the cases, while a type-2 Brugada ECG pattern was observed in the other 2/17 (12%). In all cases, the Brugada ECG pattern resolved upon correction of the ischemia, indicating ischemia as the inducing circumstance. No arrhythmic events have been detected acutely or during the follow-up. Reported time to resolution ranged from 2 minutes to 5 hours. Provocative challenges using sodium channel blocking agents were performed in 7/17 cases (41%), and all failed to induce a Brugada ECG pattern (BrP Class A). The remaining 10/17 cases (59%) did not undergo provocative testing due to various clinical reasons.

CONCLUSIONS

Myocardial ischemia is a commonly reported etiology of BrP. Importantly, this study found no association between BrP induced by myocardial ischemia and sudden cardiac death or malignant ventricular arrhythmias.

Relation of the Brugada Phenocopy to Hyperkalemia (from the International Registry on Brugada Phenocopy)

Brugada phenocopies (BrPs) are clinical entities that differ in etiology from true congenital Brugada syndrome but have identical electrocardiographic (ECG) patterns. Hyperkalemia is known to be one of the causes of BrP. The aim of this study was to determine the clinical characteristics and evolution of hyperkalemia-induced BrP. Data from 27 cases of hyperkalemia-induced BrP were collected from the International Registry at www.brugadaphenocopy.com. Data were extracted from publications. Of the 27 patients included in the analysis, 18 (67%) were male; mean age was 53 ± 15 years (range 31 to 89). Mean serum potassium concentration was 7.45 ± 0.89 mmol/L. Type-1 Brugada ECG pattern was observed in 21 cases (78%), whereas 6 cases (22%) showed a type-2 Brugada ECG pattern. The Brugada ECG pattern resolved once the hyperkalemia was corrected, with no arrhythmic events. Estimated time to resolution was 7 ± 3 hours. In 4 cases (16%), a concurrent metabolic abnormality was detected: 3 (11%) presented with acidosis, 2 (7%) with hyponatremia, 1 (4%) with hypocalcaemia, 1 (4%) with hyperphosphatemia, and 1 (4%) with hyperglycemia. In 7 cases (26%), provocative testing using sodium channel blockers was performed, and all failed to reproduce a BrS ECG pattern (BrP class A). Additionally, no sudden cardiac death or malignant ventricular arrhythmias were detected. Hyperkalemia was found a common cause of BrP in our International Registry. The Brugada ECG pattern appears to occur at high serum potassium concentrations (>6.5 mmol/L). The ECG normalizes within hours of correcting the electrolyte imbalance. Importantly, hyperkalemia-induced BrP has not been associated with sudden cardiac death or ventricular arrhythmia.

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

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

pH Modulation of Voltage-Gated Sodium Channels

Changes in blood and tissue pH accompany physiological and pathophysiological conditions including exercise, cardiac ischemia, ischemic stroke, and cocaine ingestion. These conditions are known to trigger the symptoms of electrical diseases in patients carrying sodium channel mutations. Protons cause a diverse set of changes to sodium channel gating, which generally lead to decreases in the amplitude of the transient sodium current and increases in the fraction of non-inactivating channels that pass persistent currents. These effects are shared with disease-causing mutants in neuronal, skeletal muscle, and cardiac tissue and may be compounded in mutants that impart greater proton sensitivity to sodium channels, suggesting a role of protons in triggering acute symptoms of electrical disease.In this chapter, we review the mechanisms of proton block of the sodium channel pore and a suggested mode of action by which protons alter channel gating. We discuss the available data on isoform specificity of proton effects and tissue level effects. Finally, we review the role that protons play in disease and our own recent studies on proton-sensitizing mutants in cardiac and skeletal muscle sodium channels.

Mechanisms and models of cardiac sodium channel inactivation

Shortly after cardiac Na+ channels activate and initiate the action potential, inactivation ensues within milliseconds, attenuating the peak Na+ current, INa, and allowing the cell membrane to repolarize. A very limited number of Na+ channels that do not inactivate carry a persistent INa, or late INa. While late INa is only a small fraction of peak magnitude, it significantly prolongs ventricular action potential duration, which predisposes patients to arrhythmia. Here, we review our current understanding of inactivation mechanisms, their regulation, and how they have been modeled computationally. Based on this body of work, we conclude that inactivation and its connection to late INa would be best modeled with a "feet-on-the-door" approach where multiple channel components participate in determining inactivation and late INa. This model reflects experimental findings showing that perturbation of many channel locations can destabilize inactivation and cause pathological late INa.

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

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

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?

Efficacy and safety of dextrose-insulin in unmasking non-diagnostic Brugada ECG patterns

BACKGROUND

Typical diagnostic, coved-type 1, Brugada ECG patterns fluctuate spontaneously over time with a high proportion of non-diagnostic ECG patterns. Insulin modulates ion transport mechanisms and causes hyperpolarization of the resting potential. We report our experience with unmasking J-ST changes in response to a dextrose-insulin test.

METHODS

Nine patients, mean age 40.5±19.4years (range: 15-65years), presented initially with a non-diagnostic ECG pattern, which was suggestive of Brugada syndrome (group I). They were compared with 10 patients with normal ECG patterns (group II). Participants received an infusion of 50g of 50% dextrose, followed by 10IU of intravenous regular insulin. Positive changes were defined by conversion to a diagnostic ECG pattern.

RESULTS

The dextrose-insulin test was positive in six of seven (85.7%) patients (kappa 0.79, p=0.02) that was confirmed with a pharmacologic test (kappa 1, p=0.003). One had an inconclusive test, and two with a negative test had an early repolarization ECG pattern. All subjects in group II had a negative test (p<0.01). The maximum changes of the J-ST segment were observed 41.3±31.4minutes (range 3-90minutes) after dextrose-insulin infusion. One patient had monomorphic ventricular bigeminy without spontaneous or induced ventricular fibrillation.

CONCLUSION

Changes in J-ST segment in the Brugada syndrome are influenced by glucose-insulin, and this report reproduces and supports the efficacy and safety of this metabolic test in the differential diagnosis of patients with non-diagnostic ECG patterns.

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.