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At least 19 recordsLinked to original sources

PubMed2002

Long QT syndrome, Brugada syndrome, and conduction system disease are linked to a single sodium channel mutation.

The function of the 12 positive charges in the 53-residue III/IV interdomain linker of the cardiac Na(+) channel is unclear. We have identified a four-generation family, including 17 gene carriers with long QT syndrome, Brugada syndrome, and conduction system disease with deletion of lysine 1500 (DeltaK1500) within the linker. Three family members died suddenly. We have examined the functional consequences of this mutation by measuring whole-cell and single-channel currents in 293-EBNA cells expressing the wild-type and DeltaK1500 mutant channel. The mutation shifted V(1/2)h( infinity ) to more negative membrane potentials and increased k(h) consistent with a reduction of inactivation valence of 1. The shift in h( infinity ) was the result of an increase in closed-state inactivation rate (11-fold at -100 mV). V(1/2)m was shifted to more positive potentials, and k(m) was doubled in the DeltaK1500 mutant. To determine whether the positive charge deletion was the basis for the gating changes, we performed the mutations K1500Q and K1500E (change in charge, -1 and -2, respectively). For both mutations, V(1/2)h was shifted back toward control; however, V(1/2)m shifted progressively to more positive potentials. The late component of Na(+) current was increased in the DeltaK1500 mutant channel. These changes can account for the complex phenotype in this kindred and point to an important role of the III/IV linker in channel activation.

Arrhythmias, Cardiac↗

PubMed1999

[Right bundle branch block, ST segment elevation and sudden cardiac death. A clinical and electrocardiographic syndrome--Brugada syndrome].

The association of an abnormal electrocardiogram (ecg) consisting of right bundle branch block and ST segment elevation in leads V1-V3 and sudden arrhythmic death has been described in patients with no demonstrable structural heart disease. A patient with these ecg findings and aborted sudden death is presented. The patient had no structural heart disease and received an implantable cardioverter-defibrillator which seems to be the treatment of choice.

Adult↗

PubMed2000

[Anesthetic management of a patient with Brugada syndrome].

Brugada syndrome is characterized by right bundle-branch block, ST elevation in leads V 1 through V 3 and normal QT interval. Ventricular fibrillation frequently occurs in patients with Brugada syndrome. There have been few reports of anesthetic management of Brugada patients. We managed a 47-year-old man with Brugada syndrome, who underwent hemilaminectomy under general anesthesia, without untoward cardiovascular events. Potential problems in anesthetic management of patients with Brugada syndrome are also discussed.

Anesthesia, General↗

PubMed2006

[Anesthetic management for patients with Brugada syndrome].

Brugada syndrome should not be neglected in terms of anesthetic management because its perioperative autonomic imbalance may cause ventricular fibrillation and sudden cardiac arrest. Diagnosis of Brugada syndrome is easily made by unique electrocardiographic pattern of right bundle branch block and ST segment elevation in the right precordial leads. Thus the number of patients with Brugada syndrome for anesthetic management tends to increase. We review current concept of anesthetic management for patients with Brugada syndrome including fourteen cases in our institution, two out of which developed VF during operation.

Adult↗

PubMed2000

Enhanced Na(+) channel intermediate inactivation in Brugada syndrome.

Brugada syndrome is an inherited cardiac disease that causes sudden death related to idiopathic ventricular fibrillation in a structurally normal heart. The disease is characterized by ST-segment elevation in the right precordial ECG leads and is frequently accompanied by an apparent right bundle-branch block. The biophysical properties of the SCN5A mutation T1620M associated with Brugada syndrome were examined for defects in intermediate inactivation (I:(M)), a gating process in Na(+) channels with kinetic features intermediate between fast and slow inactivation. Cultured mammalian cells expressing T1620M Na(+) channels in the presence of the human beta(1) subunit exhibit enhanced intermediate inactivation at both 22 degrees C and 32 degrees C compared with wild-type recombinant human heart Na(+) channels (WT-hH1). Our findings support the hypothesis that Brugada syndrome is caused, in part, by functionally reduced Na(+) current in the myocardium due to an increased proportion of Na(+) channels that enter the I:(M) state. This phenomenon may contribute significantly to arrhythmogenesis in patients with Brugada syndrome. The full text of this article is available at http://www.circresaha.org.

Amino Acid Substitution↗

PubMed1999

Ion channels and ventricular arrhythmias: cellular and ionic mechanisms underlying the Brugada syndrome.

Brugada syndrome is characterized by ST segment elevation in the right precordial leads, V1-V3 (unrelated to ischemia or structural disease), normal QT intervals, apparent right bundle branch block, and sudden cardiac death, particularly in men of Asian origin. An autosomal dominant mode of inheritance with variable expression has been described. The only gene thus far linked to the Brugada syndrome is the cardiac sodium channel gene, SCN5A. The possible cellular and ionic basis for these features of the Brugada syndrome are discussed. Strong sodium channel block, among other modalities, has been shown to be capable of inducing epicardial and transmural dispersion of repolarization, thus providing the substrate for the development of phase 2 and circus movement reentry, which underlies ventricular tachycardia/ventricular fibrillation.

Animals↗

PubMed2002

Novel mutations in domain I of SCN5A cause Brugada syndrome.

Brugada syndrome, an autosomal dominantly inherited form of ventricular fibrillation characterized by ST-segment elevation in leads V1-V3 and right bundle-branch block on surface electrocardiogram, is caused by mutations in the cardiac sodium channel gene SCN5A. Patients with Brugada syndrome were studied using single-strand conformation polymorphism analysis, denaturing high-performance liquid chromatography, and DNA sequencing of SCN5A. Mutations were identified in SCN5A in two families and one sporadic case. In one family, a missense mutation leading to a glycine to valine substitution (G351V) in the pore region between the DIS5 and DIS6 transmembrane segments was detected. Biophysical analysis demonstrated that this mutation caused significant current reduction. In the other family, a 20-bp deletion of the exon 5 splice acceptor site was identified; as exon 5 encodes part of the intracellular loop between DIS2 and DIS3, this portion of the channel is disrupted. In the sporadic patient, a missense mutation resulting in the substitution of lysine by glutamic acid (K126E) in the intracellular loop at the boundary with DIS1 was identified. These three new SCN5A mutations in Brugada syndrome patients are all located within domain I of SCN5A, a region not previously considered important in the development of ventricular arrhythmias.

Animals↗

PubMed2003

The Brugada syndrome.

Brugada syndrome describes the syndrome of sudden cardiac death in the setting of the following electrocardiographic findings: right bundle branch block pattern with ST-segment elevation in the right precordial leads. The right bundle branch block may be incomplete while the ST segment elevation is minimal. The electrocardiographic findings are not constant. Patients suspected of having Brugada syndrome should be promptly referred for electrophysiological testing and treatment. Rapid referral and placement of an implantable cardioverter defibrillator (ICD) is associated with an excellent prognosis, whereas failure to diagnose this condition is associated with a high risk for sudden death. Therefore, it is imperative that all emergency physicians be familiar with the typical ECG manifestations of Brugada syndrome. Three illustrative cases are presented with a review of the syndrome.

Adult↗

PubMed2002

Expression and intracellular localization of an SCN5A double mutant R1232W/T1620M implicated in Brugada syndrome.

Brugada syndrome is an inherited cardiac disorder caused by mutations in the cardiac sodium channel gene, SCN5A, that leads to ventricular fibrillation and sudden death. This study reports the changes in functional expression and cellular localization of an SCN5A double mutant (R1232W/T1620M) recently discovered in patients with Brugada syndrome. Mutant and wild-type (WT) human heart sodium channels (hNa(v)1.5) were expressed in tsA201 cells in the presence of the beta(1)-auxiliary subunit. Patch-clamp experiments in whole-cell configuration were conducted to assess functional expression. Immunohistochemistry and confocal microscopy were used to determine the spatial distribution of either WT or mutant cardiac sodium channels. The results show an abolition of functional sodium channel expression of the hNa(v)1.5/R1232W/T1620M mutant in the tsA201 cells. A conservative positively charged mutant, hNa(v)1.5/R1232K/T1620M, produced functional channels. Immunofluorescent staining showed that the FLAG-tagged hNa(v)1.5/WT transfected into tsA201 cells was localized on the cell surface, whereas the FLAG-tagged hNa(v)1.5/R1232W/T1620M mutant was colocalized with calnexin within the endoplasmic reticulum (ER). These results indicate that a positively charged arginine or lysine residue at position 1232 in the double mutant is required for the proper transport and functional expression of the hNa(v)1.5 protein. These results support the concept that loss of function of the cardiac Na(+) channel is responsible for the Brugada syndrome. The full text of this article is available at http://www.circresaha.org.

Animals↗

PubMed2005

Mechanisms of disease: current understanding and future challenges in Brugada syndrome.

Brugada syndrome is a clinical entity characterized by ST-segment elevation in the right precordial leads (V1-V3) and an episode of ventricular fibrillation in the absence of structural heart disease. Data regarding genotype-phenotype relationships are limited, since SCN5A, the gene encoding the a subunit of the sodium channel, is as yet the only gene linked to Brugada syndrome. Studies of SCN5A mutations responsible for the Brugada phenotype have shown the presence of functional defects in the sodium-channel current. Experimental studies employing arterially perfused right-ventricular wedge preparations have elucidated cellular mechanisms for this phenotype. Data indicate that an accentuated action-potential notch, mediated by a prominent transient outward current and loss of the action-potential dome in the epicardium (but not in the endocardium) of the right ventricle give rise to a transmural voltage gradient, resulting in ST-segment elevation and the induction of ventricular fibrillation. On the basis of cellular mechanisms, it might be possible to normalize the Brugada phenotype by use of therapeutic agents or interventions that decrease net outward currents by decreasing the transient outward current or outward potassium currents, or increasing the L-type inward calcium current or fast sodium current. Interventions that increase net outward currents through raising the transient outward current or outward potassium currents or decreasing the L-type inward calcium current or fast sodium current might aggravate or unmask the Brugada phenotype, resulting in an acquired form of this syndrome. In this review, we discuss future challenges relating to risk stratification, genetic heterogeneity, sex and ethnic differences in Brugada syndrome.

Bundle-Branch Block↗

PubMed2005

[Brugada syndrome].

Brugada syndrome is believed to be responsible for 4 to 12% of all sudden deaths and for 20% of deaths in patients with structurally normal hearts. As a distinct clinical entity with a high risk of sudden cardiac death it was first described in 1992. The syndrome characterized by ST segment elevation in right precoardial leads V1 to V3 unrelated to ischemia and by electrolyte disturbance without obvious structural heart disease. The clinical findings are based on ECG and syncope or sudden death. The arrhythmia leading to sudden death is a rapid polymorphic ventricular tachycardia. The electrocardiographic signature of the syndrome is dynamic and often concealed, but can be unmasked by potent sodium channel blockers such as flecainde, ajmaline. The Brugada syndrome is a familial disease displaying an autosomal dominant mode of transmission with incomplete penetration and with incidence ranging between 5 and 66 per 10,000. The syndrome has been linked to mutations in SCNA5, the gene encoding for the a subunit of the sodium channel. Implantation of an automatic cardiverter-defibrillator is the only currently proven effective therapy.

Death, Sudden, Cardiac↗

PubMed2006

Electrocardiogram interpretation and class I blocker challenge in Brugada syndrome.

Brugada syndrome is characterized by the presence of an electrocardiographic pattern of ST-segment elevation in leads V1 to V3 and a history of sudden cardiac death in the absence of structural heart disease [Brugada P, Brugada J. Right bundle branch block, persistent ST segment elevation and sudden cardiac death: a distinct clinical and electrocardiographic syndrome. A multicenter report. J Am Coll Cardiol 1992;20(6):1391]. The disease usually affects individuals in their 40s, at the prime of their life, and the appearance of cardiac arrest in these otherwise healthy individuals brings an important burden to families and to health care. Brugada syndrome is in several instances a familial disease, caused by mutations in SCN5A in up to 25% of the individuals [Chen Q, Kirsch GE, Zhang D, Brugada R, Brugada J, Brugada P, et al. Genetic basis and molecular mechanism for idiopathic ventricular fibrillation. Nature 1998;392(6673):293]. The identification of the electrocardiographic pattern in an individual will therefore trigger an important cascade of events in the families. Several family members, including children, will be under the scrutiny of a cardiologist to decide on preventive measures, especially if there is a history of sudden death in the family. The presence of abnormal repolarization patterns, which in otherwise sporadic individuals might be classified under normal variations, have become a diagnostic challenge for clinicians facing a family with the disease [Hong K, Brugada J, Oliva A, Berruezo-Sanchez A, Potenza D, Pollevick GD, et al. Value of electrocardiographic parameters and ajmaline test in the diagnosis of Brugada syndrome caused by SCN5A mutations. Circulation 2004;110(19):3023].

Bundle-Branch Block↗

PubMed2004

Anaesthesia in patients with Brugada syndrome.

Brugada syndrome is characterized by right bundle branch block, ST segment elevation in the precordial leads and sudden death caused by ventricular fibrillation. We present two successful anaesthetic management cases in patients with Brugada syndrome.

Adult↗

PubMed2005

Electrophysiological basis and genetics of Brugada syndrome.

Brugada syndrome is a primary arrhythmic syndrome arising in the structurally normal heart. Any proposed mechanism should account for the major features of the syndrome: localization of the ST segment and T-wave changes to the right precordial leads, association of conduction slowing at several levels, precipitation or aggravation of the major ECG changes by sodium channel-blocking drugs and the occurrence of ventricular fibrillation. Heterogeneity of repolarization across the ventricle wall plays a major role. Any agency that shifts the net current gradient during phase I outward would exaggerate the normal heterogeneity of repolarization and result in the ST segment and T-wave changes characteristic of the syndrome. When the outward current shift is marked, premature repolarization may occur in epicardial zone and the resulting gradient may precipitate reentry. The syndrome is inherited as an autosomal dominant. However, 75% of clinically affected individuals are males. In 20% of cases, the syndrome is associated with mutations of the cardiac sodium channel gene SCN5A. The mutations result in a loss-of-function as a result of the synthesis of a non-functional protein, altered protein trafficking, or change in gating. Agencies that reduce the sodium current may precipitate the characteristic ECG changes, for example, sodium channel blockers and membrane depolarization by hyperkalemia. Sympathetic stimulation may reverse the ECG changes and reduce arrhythmia recurrence. By its nonspecific potassium channel blocking action, quinidine may also reduce arrhythmia recurrence. We still do not know the basis for defect in the majority of patients with Brugada syndrome.

Bundle-Branch Block↗

PubMed2005

[Long QT syndrome and Brugada syndrome. Drugs, ablation or ICD?].

Long QT syndrome and Brugada syndrome are potentially fatal inherited arrhythmogenic diseases. Thanks to the contribution of molecular genetics, the genetic bases, pathogenesis, and genotype-phenotype correlation of both diseases have been progressively unveiled and shown to have an extremely high degree of genetic heterogeneity. The clinical manifestation of the diseases is also highly variable. Symptomatic patients experience ventricular tachyarrhythmias which may lead to recurrent syncope and/or sudden cardiac death. In long QT syndrome patients with syncope, therapy with beta-blockers has proven effective. When, despite beta-blocker treatment, arrhythmia-related symptoms continue to occur, an implantable cardioverter defibrillator is indicated. Such a device should also be implanted in resuscitated patients. In symptomatic patients with Brugada syndrome, the implantable cardioverter defibrillator is the only life-saving option. In asymptomatic patients with a Brugada ECG pattern, risk stratification has become of utmost importance in order to discover which patients really need definitive treatment.

Anti-Arrhythmia Agents↗

PubMed2007

Drug-induced pericarditis mimicking Brugada syndrome.

Brugada syndrome (BS) is associated with sudden cardiac death in patients with a structurally normal heart. The ECG pattern of BS has also been described in patients with myocardial abnormalities. Cardiac hypersensitivity and myopericarditis have been reported during long-term treatment with mesalazine. We report the case of a man, treated with mesalazine for Crohn's disease who developed drug-induced pericarditis. The ECG showed a coved ST-segment elevation in the right precordial leads V1-V3, a pattern mimicking BS. The ECG normalized in a few days after mesalazine withdrawal and the follow-up was uneventful. The ECG remained normal. Two ajmaline tests were both negative and ruled out the diagnosis of BS. This observation illustrates that a coved ST-segment elevation in the right precordial leads should not be, systematically, regarded as a marker of a specific syndrome, but may also reflect a common electrical manifestation of abnormalities in the right ventricle or pericardium.

Adult↗

PubMed2001

[Long QT syndrome and Brugada syndrome: 2 aspects of the same disease?].

In clinical cardiology, resort has recently been made to molecular genetics in order to explain some mechanisms that underlie sudden cardiac death in young people with structurally normal hearts. It has become evident that genetic mutations regarding cardiac ion channels may disrupt the delicate balance of currents in the action potential, thus inducing malignant ventricular tachyarrhythmias. The cardiac sodium channel gene, SCN5A, is involved in two of such arrhythmogenic diseases, the Brugada syndrome and one form of the long QT syndrome (LQT3). It is believed that these syndromes result from opposite molecular effects: Brugada syndrome mutations cause a reduced sodium current, while LQT3 mutations are associated with a gain of function. The effects of class I antiarrhythmic drugs have been used to differentiate these diseases. Intravenous flecainide is used as a highly specific test to unmask the electrocardiographic phenotype of the Brugada syndrome. On the other hand, on the basis of experimental and clinical studies, the possibility that the same drugs act as a gene-specific therapy in this disorder by contrasting the effect of mutations in LQT3 has been explored. Recent evidence shows that phenotypic overlap may exist between the Brugada syndrome and LQT3. One large family with a SCN5A mutation and a "mixed" electrocardiographic pattern (prolonged QT interval and ST-segment elevation) has been reported. Moreover, our recent data showed that flecainide challenge may elicit ST-segment elevation in some LQT3 patients. The presence of "intermediate" phenotypes highlights a remarkable heterogeneity suggesting that clinical features may depend upon the single mutation. Only deepened understanding of the genotype-phenotype correlation will allow the definition of the individual patient's risk and the development of guidelines for clinical management.

Anti-Arrhythmia Agents↗

PubMed2006

A novel mutation in the SCN5A gene is associated with Brugada syndrome.

Brugada syndrome (BS) is an inherited cardiac disorder associated with a high risk of sudden cardiac death and is caused by mutations in the SCN5A gene encoding the cardiac sodium channel alpha-subunit (Na(v)1.5). The aim of this study was to identify the genetic cause of familial BS and characterize the electrophysiological properties of a novel SCN5A mutation (W1191X). Four families and one patient with BS were screened for SCN5A mutations by PCR and direct sequencing. Wild-type (WT) and mutant Na(v)1.5 channels were expressed in tsA201 cells, and the sodium currents (I(Na)) were analyzed using the whole-cell patch-clamp technique. A novel mutation, W1191X, was identified in a family with BS. Expression of the WT or the mutant channel (Na(v)1.5/W1191X) co-transfected with the beta(1)-subunit in tsA201 cells resulted in a loss of function of Na(v)1.5 channels. While voltage-clamp recordings of the WT channel showed a distinct acceleration of Na(v)1.5 activation and fast inactivation kinetics, the Na(v)1.5/W1191X mutant failed to generate any currents. Co-expression of the WT channel and the mutant channel resulted in a 50% reduction in I(Na). No effect on activation and inactivation were observed with this heterozygous expression. The W1191X mutation is associated with BS and resulted in the loss of function of the cardiac sodium channel.

Adult↗