The Brugada syndrome revisited

The Brugada syndrome is a rare but well-defined cause of sudden cardiac death. The key underlying abnormality is a decrease in net depolarising current due to a genetic defect, though recent evidence also implicates structural abnormalities in some patients. Diagnosis requires a Brugada-type ECG as well as typical clinical features: such clinical considerations are currently key in guiding risk stratification and hence management. Whilst pharmacological therapies are under investigation, the only intervention with a robust evidence base remains insertion of an implantable cardioverter defibrillator. Further research will be required to allow more effective risk stratification and hence more rational therapy.

Cardiac autonomic control in Brugada syndrome patients during sleep: the effects of sleep disordered breathing

AIMS

Brugada syndrome is characterized by typical ECG features, ventricular arrhythmias and sudden cardiac death (SCD), more frequent during nighttime. Autonomic cardiovascular control has been implicated in triggering the ventricular arrhythmias. Sleep-disordered breathing (SDB) elicits marked autonomic changes during sleep and is also associated with an increased risk of nighttime SCD. Brugada patients may have a higher likelihood of SDB compared to controls. However, no data are available on cardiac autonomic control in Brugada patients, particularly with regard to the comorbidity of SDB.

METHODS

We evaluated autonomic cardiovascular control in Brugada patients with SDB (BRU-SDB, n=9), without SDB (BRU, n=9), in controls (CON, n=8) and in non-Brugada patients with SDB (n=6), during wakefulness and sleep (N2, N3 and REM). Linear spectral and entropy-derived measures of heart rate variability (HRV) were performed during apnea-free stable breathing epochs.

RESULTS

Total HRV was attenuated in BRU-SDB compared to CON and BRU. During N2 and REM, in BRU-SDB patients sympathetic modulation decreased compared to BRU and CON, while during REM, they showed an increased parasympathetic modulation, compared to the other two groups. BRU-SDB and SDB were similar in terms of spectral components. Entropy-derived indices showed preserved dynamic changes in Brugada patients compared to controls through the different sleep stages.

CONCLUSION

Brugada syndrome per se does not appear associated with an altered autonomic cardiovascular control during wakefulness and sleep. The comorbidity with SDB may contribute to disrupted autonomic cardiovascular regulation during sleep, possibly predisposing to the increased likelihood of sleep-related ventricular tachyarrhythmias and SCD.

Electrical storm in the brain and in the heart: epilepsy and Brugada syndrome

We describe a patient with the coincidence of 2 ion channel disorders with autosomal dominant inheritance: Brugada syndrome, a potentially fatal cardiac condition, and cryptogenic focal epilepsy, likely due to a neurologic channelopathy. Although Brugada syndrome was discovered incidentally, most of the clinical features of epilepsy in this patient shared the risk factor characteristics of sudden unexplained death in epilepsy syndrome. This case provides additional information on the potential interaction between ion channel abnormalities in the heart and in the brain. Furthermore, it may suggest that patients with epilepsy at increased risk for sudden unexplained death in epilepsy syndrome should undergo a careful cardiac evaluation.

Brugada phenocopy in a patient with pectus excavatum: systematic review of the ECG manifestations associated with pectus excavatum

Brugada phenocopies (BrP) have emerged as new clinical entities that are etiologically distinct from true Brugada syndrome (BrS). BrP are characterized by an ECG pattern that is phenotypically identical to true BrS (type 1 or type 2); however, BrP are caused by various other factors such as mechanical mediastinal compression, myocardial ischemia, pericarditis, myocarditis, pulmonary embolism, and metabolic disturbances. We report a case of an electrocardiographic BrP in a patient with pectus excavatum deformity in the absence of true BrS using currently defined BrP diagnostic criteria. A systematic review of ECG manifestations associated with pectus excavatum is also discussed.

Outcome after implantation of a cardioverter-defibrillator in patients with Brugada syndrome: a multicenter study-part 2

BACKGROUND

Implantable cardioverter-defibrillator indications in Brugada syndrome remain controversial, especially in asymptomatic patients. Previous outcome data are limited by relatively small numbers of patients or short follow-up durations. We report the outcome of patients with Brugada syndrome implanted with an implantable cardioverter-defibrillator in a large multicenter registry.

METHODS AND RESULTS

A total of 378 patients (310 male; age, 46±13 years) with a type 1 Brugada ECG pattern implanted with an implantable cardioverter-defibrillator (31 for aborted sudden cardiac arrest, 181 for syncope, and 166 asymptomatic) were included. Fifteen patients (4%) were lost to follow-up. During a mean follow-up of 77±42 months, 7 patients (2%) died (1 as a result of an inappropriate shock), and 46 patients (12%) had appropriate device therapy (5±5 shocks per patient). Appropriate device therapy rates at 10 years were 48% for patients whose implantable cardioverter-defibrillator indication was aborted sudden cardiac arrest, 19% for those whose indication was syncope, and 12% for the patients who were asymptomatic at implantation. At 10 years, rates of inappropriate shock and lead failure were 37% and 29%, respectively. Inappropriate shock occurred in 91 patients (24%; 4±4 shocks per patient) because of lead failure (n=38), supraventricular tachycardia (n=20), T-wave oversensing (n=14), or sinus tachycardia (n=12). Importantly, introduction of remote monitoring, programming a high single ventricular fibrillation zone (>210-220 bpm), and a long detection time were associated with a reduced risk of inappropriate shock.

CONCLUSIONS

Appropriate therapies are more prevalent in symptomatic Brugada syndrome patients but are not insignificant in asymptomatic patients (1%/y). Optimal implantable cardioverter-defibrillator programming and follow-up dramatically reduce inappropriate shock. However, lead failure remains a major problem in this population.

Brugada syndrome

As a clinical entity the Brugada syndrome has existed since 1992 and has been associated with a high risk of sudden cardiac death predominately in younger males. Patients can present with symptoms (ie syncope, palpitations, aborted sudden cardiac death) and asymptomatically. Its three characteristic electrocardiographic patterns can occur both spontaneously or after provocation with sodium channel-blocking agents. Risk stratification and the need for treatment depend on the patient's symptoms, electrocardiography, family history, and electrophysiological inducibility to discern if treatment by implantable cardioverter defibrillator, the only effective treatment to date, is appropriate. This review focuses on Brugada syndrome and various aspects of the disease including proposed mechanisms, epidemiology, clinical presentations, genetics, diagnosis, risk stratification, and treatment options.

Clinical characteristic and clinical course of aborted sudden cardiac death patients with structurally normal heart in King Chulalongkorn Memorial Hospital

BACKGROUND

PED (Primary electrical disease) is an arrhythmogenic disease group that causes serious ventricular tachyarrhythmia in the absence of recognized structural heart disease. Although Thailand, which is a part of Southeast Asia, is an endemic area of PED, especially Brugada syndrome, there is little known about demographic data and clinical outcome of PED among survivors of sudden cardiac death (SCD).

OBJECTIVE

To study demographic data and clinical outcome of PED among survivors of SCD in Thailand.

MATERIAL AND METHOD

The present study was approved by the ethics committee of the Faculty of Medicine, Chulalongkorn University, Bangkok. The authors reviewed patient medical records for clinical characteristics, etiology, and clinical outcome of survivors of SCD between January 2002 and December 2008. The patients with PED who had normal structural heart and no obvious non-cardiac causes of sudden death were enrolled.

RESULTS

Fifty-two survivors of SCD with PED (mean age 39 +/- 12, 49 males), mainly from the northeast and middle regions of Thailand, were recruited for this study. SCD mainly occurred during times when patients were asleep or resting (50% and 15.4%) respectively. Of the 52 survivors, 21 patients (40%) had a documented family history of SCD. The etiology of survivors of SCD is composed of Brugada syndrome (63.5%), Early repolarization syndrome (ERS) (9.6%). Congenital long QT syndrome (LQTS) (7.7%), and idiopathic VF (3.8%). Remaining 15.4% had abnormal ECG but not compatible with any etiology. A large number of patients (78.8%) completely recovered without neurological sequelae. The recurrence of severe ventricular arrhythmia occurred in 27 patients (51.9%) during mean follow-up period 56.5 +/- 35.4 months (4 to 137 months). The recurrence was highest during the first year (32%) of follow-up.

CONCLUSION

The Brugada syndrome is the most common etiology of survivors of SCD with normal structural heart in Thailand Although the prognosis after resuscitation was good, recurrence was especially high during the first year and as a result, an ICD implantation is needed for prevented recurrence of SCD.

Current electrocardiographic criteria for diagnosis of Brugada pattern: a consensus report

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 (I(to)) to generate a voltage gradient in the right ventricular layers. This gradient triggers ventricular tachycardia/ventricular fibrillation possibly through a phase 2 reentrant mechanism. The Brugada electrocardiographic (ECG) pattern, which can be dynamic and is sometimes concealed, being only recorded in upper precordial leads, is the hallmark of Brugada syndrome. Because of limitations of previous consensus documents describing the Brugada ECG pattern, especially in relation to the differences between types 2 and 3, a new consensus report to establish a set of new ECG criteria with higher accuracy has been considered necessary. In the new ECG criteria, only 2 ECG patterns are considered: pattern 1 identical to classic type 1 of other consensus (coved pattern) and pattern 2 that joins patterns 2 and 3 of previous consensus (saddle-back pattern). This consensus document describes the most important characteristics of 2 patterns and also the key points of differential diagnosis with different conditions that lead to Brugada-like pattern in the right precordial leads, especially right bundle-branch block, athletes, pectus excavatum, and arrhythmogenic right ventricular dysplasia/cardiomyopathy. Also discussed is the concept of Brugada phenocopies that are ECG patterns characteristic of Brugada pattern that may appear and disappear in relation with multiple causes but are not related with Brugada syndrome.

[Arrhythmia and genetic background]

Recent studies have demonstrated that genetic abnormalities associated with the regulation of myocardial ionic channels, receptors, transporters, cell membranous proteins etc, can create an arrhythmogenic substrate in some patients with structurally normal hearts, and these are called hereditary arrhythmic diseases. Various arrhythmic diseases (such as congenital long or short QT syndrome, Brugada syndrome, catecholamine-sensitive polymorphic ventricular tachycardia, arrhythmogenic right ventricular cardiomyopathy, early repolarization syndrome etc.) are categorized as hereditary arrhythmic diseases. Among them, we focused on long QT syndrome and Brugada syndrome in this review. In congenital long QT syndrome, either attenuation of the net outward current or augmentation of the net inward current is responsible for prolonging the myocardial action potential duration and QT interval on ECG. Premature ventricular beats triggered due to early after-depolarization infringe on the large spatial dispersion of ventricular repolarization and initiate polymorphic ventricular tachycardia with a specific form (torsade de pointes). Currently, thirteen genotypes in Romano-Ward syndrome and two genotypes in Jervell-Lange Nielsen syndrome have been reported. In Brugada syndrome, large transient outward current (Ito) creates a deep phase 1 notch in the action potential, especially at the epicardial myocardium of the right ventricular outflow tract. In combination with the delayed completion of repolarization and loss of the phase 2 dome in some epicardial myocardium in this area, coved-type ECG abnormality and ventricular fibrillation due to phase 2 reentry are believed to be induced in Brugada syndrome. Eleven genetic abnormalities are presently listed as a possible cause of Brugada syndrome.

A drop dead healthy ECG

The diagnostic and risk stratification implications of a borderline electrocardiogram, which could be a normal variant or a marker for sudden cardiac death, are explored.

Brugada-like electrocardiographic patterns induced by hyperkalemia

Brugada syndrome was described in 1992 as a new clinical and electrocardiographic syndrome involving susceptibility to ventricular arrhythmias and sudden cardiac death in patients with no obvious structural heart disease. Brugada syndrome is characterized by a hereditary anomaly in the sodium ion channel (mutation of the SCN5A gene) identified by a wide QRS associated with the ST-segment elevation and the T‑wave inversion in the right precordial leads. The Brugada-like electrocardiographic pattern can be caused by sodium channel-blocking drugs and electrolyte disorders. Hyperkalemia may produce multiple ECG abnormalities, including the ST-segment elevation and pseudomyocardial infarction with a resolution of these abnormalities after the correction of hyperkalemia. This article describes 8 cases of pseudoanteroseptal myocardial infarction in acute renal insufficiency with hyperkalemia. The ST-segment elevation related to hyperkalemia is resolved by the reduced serum potassium level. Clinicians should recognize that hyperkalemia is one of the etiologies of the Brugada-like electrocardiographic pattern.

The prognostic value of early repolarization (J wave) and ST-segment morphology after J wave in Brugada syndrome: multicenter study in Japan

BACKGROUND

The prognostic value of a J wave and ST-segment morphology after J wave in inferolateral leads in Brugada syndrome (BS) is still unknown.

OBJECTIVE

To evaluate the prognostic value of a J wave and ST-segment morphology after J wave in a large Japanese cohort of BS.

METHODS

A total of 460 consecutive patients with BS (mean age 52±14 years, 432 men) were enrolled. The presence and location of leads showing a J wave, ST-segment morphology after J wave, and clinical outcomes were evaluated in patients with documented ventricular fibrillation (VF) (N = 84), those with syncope without documented VF (N = 109), and subjects without symptoms (N = 267).

RESULTS

The prevalence of a J wave in the inferior and/or lateral leads was 12% (53 cases). The prevalence of a J wave among the 3 groups was not different. The incidence of cardiac events (sudden cardiac death or VF) during a mean follow-up period of 50±32 months was not different in patients with (11%) or without (8%) a J wave. Patients with a J wave in both inferior and lateral leads or with horizontal ST-segment morphology after J wave showed a higher incidence of cardiac events than those without (P = .04 and .02, respectively). Multivariate analysis revealed symptoms, QRS duration in lead V2>90 ms, and inferolateral J wave and/or horizontal ST-segment morphology after J wave were important for predicting cardiac events.

CONCLUSION

The presence of a J wave in multiple leads and horizontal ST-segment morphology after J wave may indicate a highly arrhythmogenic substrate in patients with BS.

Spectrum and prevalence of mutations involving BrS1- through BrS12-susceptibility genes in a cohort of unrelated patients referred for Brugada syndrome genetic testing: implications for genetic testing

OBJECTIVES

The aim of this study was to provide the spectrum and prevalence of mutations in the 12 Brugada syndrome (BrS)-susceptibility genes discovered to date in a single large cohort of unrelated BrS patients.

BACKGROUND

BrS is a potentially lethal heritable arrhythmia syndrome diagnosed electrocardiographically by coved-type ST-segment elevation in the right precordial leads (V1 to V3; type 1 Brugada electrocardiographic [ECG] pattern) and the presence of a personal/family history of cardiac events.

METHODS

Using polymerase chain reaction, denaturing high-performance liquid chromatography, and DNA sequencing, comprehensive mutational analysis of BrS1- through BrS12-susceptibility genes was performed in 129 unrelated patients with possible/probable BrS (46 with clinically diagnosed BrS [ECG pattern plus personal/family history of a cardiac event] and 83 with a type 1 BrS ECG pattern only).

RESULTS

Overall, 27 patients (21%) had a putative pathogenic mutation, absent in 1,400 Caucasian reference alleles, including 21 patients with an SCN5A mutation, 2 with a CACNB2B mutation, and 1 each with a KCNJ8 mutation, a KCND3 mutation, an SCN1Bb mutation, and an HCN4 mutation. The overall mutation yield was 23% in the type 1 BrS ECG pattern-only patients versus 17% in the clinically diagnosed BrS patients and was significantly greater among young men<20 years of age with clinically diagnosed BrS and among patients who had a prolonged PQ interval.

CONCLUSIONS

We identified putative pathogenic mutations in ∼20% of our BrS cohort, with BrS genes 2 through 12 accounting for <5%. Importantly, the yield was similar between patients with only a type 1 BrS ECG pattern and those with clinically established BrS. The yield approaches 40% for SCN5A-mediated BrS (BrS1) when the PQ interval exceeds 200 ms. Calcium channel-mediated BrS is extremely unlikely in the absence of a short QT interval.

Identifying patients at risk of sudden arrhythmic death

Most GPs will encounter at least one case of sudden arrhythmic death syndrome (SADS) during their career. They may have to evaluate a young person at risk of SADS or offer support and screening to family members. SADS is the term used to describe an unexpected death in individuals with no prior history of cardiac disease and where no underlying pathology is identified despite a comprehensive post-mortem evaluation and toxicology screen. in England alone, SADS is responsible for 544 deaths per year, with a mean age of 32 years and a male predominance. Among the 100,000 cases of sudden cardiac death in the UK per year, SADS makes up around 4%, but this proportion is significantly higher in younger cohorts (13% of sudden cardiac deaths in those aged less than 35). Most cases of SADS are the result of inherited cardiac ion channel abnormalities of the heart which predispose to fatal arrhythmias. These include Brugada syndrome, long QT syndrome, short QT syndrome and catecholaminergic polymorphic ventricular tachycardia. Most individuals remain asymptomaticand are diagnosed incidentally on routine ECG testing or family screening. Syncope or cardiac arrest may be the first manifestation, All first-degree relatives of SADS victims should be referred for comprehensive evaluation in an expert setting. In studies of families of SADS victims evaluation of blood relatives identified a hereditary arrhythmogenic syndrome in almost 50% of families, thereby providing a likely cause of ath and preventing further tragedies.

Brugada phenocopy: new terminology and proposed classification

Brugada syndrome is a channelopathy characterized on ECG by coved ST-segment elevation (≥2 mm) in the right precordial leads and is associated with an increased risk of malignant ventricular arrhythmias. The term Brugada phenocopy is proposed to describe conditions that induce Brugada-like ECG manifestations in patients without true Brugada syndrome. An extensive review of the literature identified case reports that were classified according to their suspected etiological mechanism. Future directions to learn more about these intriguing cases is discussed.

The usefulness of the consensus clinical diagnostic criteria in Brugada syndrome

BACKGROUND

Consensus statements were proposed for the diagnosis of Brugada syndrome (BS). The clinical diagnostic criteria were defined as documented ventricular fibrillation or ventricular tachycardia (VT), family history of sudden cardiac death at <45 years, diagnostic ECGs of family members, inducibility of VT during electrophysiological study, syncope or nocturnal agonal respiration. The clinical validation of these criteria is still missing. Methods and results 280 patients (41 ± 18 years, male: 168 pts) with diagnostic coved type I ECG were included. Consensus clinical diagnostic criteria were present in 244 (87%) patients (40 ± 18 y, 142 males). In 36 pts (13% of the 280 pts, 51 ± 12 years, 27 males) consensus clinical diagnostic criteria were not met. Nine patients (25%) presented with spontaneous type I ECG. Ten of the 36 patients (28%) had a history of atrial fibrillation and 13 (36%) had conduction disease on the baseline ECG. In 23 patients (64%) family screening was not performed. Two of the 36 patients had undocumented syncope during follow-up. Univariate analysis showed no significant difference in event free survival between patients with or without consensus clinical diagnostic criteria.

CONCLUSIONS

In a significant number of patients with diagnostic ECG pattern the current diagnostic criteria for BS are not met. These patients have frequently spontaneous type I ECG and clinical signs of Brugada syndrome as paroxysmal atrial fibrillation or conduction disturbances. Our results suggest that in patients with a diagnostic type I ECG pattern the current clinical consensus diagnostic criteria have limited added diagnostic value.

Brugada pattern mimicking acute coronary syndrome in a febrile state

The Brugada type pattern is characterized by a coved or saddleback shaped ST-segment elevation in the right precordial leads (V1-V3) on a surface 12 lead electrocardiogram (ECG). This pattern can be seen spontaneously, induced by sodium channel blocking drugs or rarely by hyperthermia. The mechanism is secondary to an alteration in the sodium channels induced by a febrile state. Such ECG's could easily be mistaken for acute ST segment elevation myocardial infarction and thus pose a unique clinical challenge to emergency room physicians. We report such a case of fever induced Brugada pattern and discuss the underlying mechanisms.

[Arrhythmic storm in a patient with Brugada syndrome--an unusual case]

Brugada syndrome is characterized by episodes of near sudden death or syncope. The heart is normal on physical, angiographic and echocardiographic examination. The characteristic ECG abnormalities consist of ST-segment elevation in leads V1-V3 and pseudo right bundle branch block. The ECG changes can be transient, causing the diagnosis to be missed. Provocative testing with Flecainide or other sodium channel blocking drugs can be used to unmask the ECG abnormalities. This is a case study of a young male who had been diagnosed as suffering from Brugada syndrome and had a defibrillator implanted five years ago. This time the patient was admitted because of syncope and documented an arrhythmic storm (seven episodes of ventricular fibrillation, treated with the implanted defibrillator). The episode occurred following extreme anger and an "exciting event", evoking sympathetic activity. The issue of a different form of autonomic modulation: involving sodium channels' activity in the heart (sympathetic rather than vagal) is raised.

Propofol-induced coved-type electrocardiogram during catheter ablation of paroxysmal atrial fibrillation. A case of Brugada syndrome?

We report a case of a young man with paroxysmal atrial fibrillation, in whom a characteristic coved-type Brugada pattern developed during catheter ablation performed under sedation with propofol. After immediate discontinuation of the propofol infusion, coved-type ST-segment elevation gradually resolved and no ventricular arrhythmias occurred. An ajmaline challenge failed to unmask a coved-type electrocardiogram and genetic testing was negative for ion channel mutations related to Brugada syndrome.

Development of Brugada syndrome following photodynamic therapy in a patient with cholangiocarcinoma

Brugada syndrome can be unmasked by several conditions including a febrile state, marked leukocytosis, and electrolyte disturbances. Herein, we describe a 62-year-old man with cholangiocarcinoma in the first reported case of Brugada syndrome onset following photodynamic therapy.

Oral amiodarone provoking inferior ST elevation and unmasking Brugada-like electrocardiogram feature

A woman presented with broad complex tachycardia. She was converted to sinus rhythm with intravenous amiodarone and continued on oral amiodarone. The amiodarone was stopped 3 weeks later as she was pregnant. Electrocardiogram (ECG) then revealed coved-type ST elevation in C1, suggestive of Brugada syndrome, and widespread inferior ST elevation. Electrocardiogram several months later showed resolution of inferior ST elevation.

[Recent clinical picture of Brugada syndrome]

Brugada syndrome is a genetically-based autosomal dominant condition. It occurs as a result of some disorder of ion channels which regulate currents responsible for development of activity potential. Brugada syndrome may appear as a family disease or as a sporadic condition. The syndrome can develop at every age of human life, yet, most frequently in the 3-4th life decade, mostly in men (85%). Its main symptoms include: malignant ventricular arrhythmia leading to fainting, and consequently accounting for, at least 4-12% of all sudden cardiac deaths and for 20-50% of deaths without any confirmed organic heart disease. The purpose of the paper was to present the currently-possessed knowledge about the condition and to highlight the necessity of an indepth ECG analysis, especially with respect to discovery of rare conditions. Due to different clinical symptoms of Brugada syndrome and a possibility of occurrence of changes in the ECG record, it is necessary to regularly monitor and check Brugada syndrome patients. Moreover, it is important to make both patients and first-contact doctors aware of a Brugada syndrome diagnosis and to inform them about a necessity of eliminating certain medicaments and factors (infections, intense physical activity) responsible for sudden cardiac death. Despite possessing great and advanced knowledge about the disorder, the implementation of cardioverter-defibrillator remains the only effective way of treating malignant arrhythmia and of preventing sudden cardiac death.

[Brugada syndrome--case report]

Brugada syndrome (BS) is a rare genetically-based condition occurring usually in the third and fourth decade of human life, mainly developing in men (85%). It is manifested through permanent or periodic malignant ventricular arrhythmia leading to fainting, and consequently sudden cardiac death. Despite possessing great knowledge of the condition, implementation of cardioverter-defibrillator still remains the only effective way of treating malignant arrhythmia and of preventing sudden cardiac death. The following paper presents a case of a healthy nineteen-year-old man who was admitted to the Outpatient Cardiologic Center for a sport qualifying check-up. During examination, the ECG showed some features of Brugada syndrome and the patient was sent for further hospital diagnostics. During the aimaline provocative test the ECG revealed ST elevation up to 4mm in V1-V2 leads, whereas the electrophysiological examination with standard protocol and with right ventricular apex and right ventricular output aggressive protocol did not provoke any ventricular arrhythmia. The patient was qualified for preventive treatment with recommendation for regular check-up in an outpatient cardiologic center and with a total ban on extreme sport exercises.

Clinical and electrocardiographic predictors of positive response to the intravenous sodium channel blockers in patients suspected of the Brugada syndrome

BACKGROUND/OBJECTIVES

Sodium channel blockers are used to unmask the diagnostic ECG pattern of the Brugada syndrome (BrS) in case of a non-diagnostic baseline ECG. The aim of the study was to determine clinical and ECG predictors of a positive challenge test in patients suspected to the BrS.

METHODS

A total of 106 consecutive patients (91 men; mean age, 35 ± 12 years) suspected of the BrS underwent the intravenous sodium channel blocker challenge test with procainamide or flecainide.

RESULTS

Of the 106 patients, positive tests were detected in 20 (19%) patients. During test, a transient episode of a second-degree atrioventricular block and isolated ventricular ectopies were observed in 1 (0.9%) and 2 (1.9%) patients, respectively. A QRS prolongation ≥ 30% was observed in 4 (3.8%) patients. Baseline QRS duration in V1 ≥ 110 ms had a sensitivity of 70% and a specificity of 80% for a positive response. An ST-segment elevation ≥ 0.17 mV in V2 had a sensitivity of 60% and a specificity of 82% for a positive response. Of the multiple clinical and ECG variables entered into a binary logistic regression analysis, a history of syncope (P=0.001), previous cardiac arrest (P=0.001), baseline QRS duration in V1 ≥ 110 ms (P=0.001), and baseline ST-segment elevation in V2 ≥ 0.17 mV (P=0.012) emerged as the independent predictors of a positive response to the intravenous challenge with sodium channel blockers.

CONCLUSION

The results of the sodium channel blocker challenge test can be predicted by clinical presentation and baseline ECG features.

Brugada pattern masking anterior myocardial infarction

A middle-aged male smoker presented with atypical chest pain. Initial electrocardiogram (ECG) showed Brugada Type 1 pattern. Subsequent ECGs demonstrated evolving anterior ST elevation myocardial infarction (STEMI), consistent with the elevated cardiac enzymes. Coronary angiogram showed significant stenoses in the left anterior descending artery, which were stented emergently. In retrospect, subtle changes were noted in the initial ECG, which could have alerted one to the STEMI. However, the presence of a Brugada Type 1 pattern masked the ECG changes of anterior STEMI and made the diagnosis difficult. A discussion of the literature surrounding Brugada syndrome is undertaken, including its clinical features, risk stratification and management.

[Brugada syndrome]

Brugada syndrome (BrS) is, along with the long QT syndrome, one of the most frequently diagnosed inherited arrhythmogenic syndromes. It is a primary electric heart disease manifested by ST segment elevations in the right precordial leads. BrS is responsible for more than 4% of all sudden deaths and at least 20% of sudden deaths in patients with structurally normal hearts. In 1998, the first mutations in the gene coding the structure of the cardiac sodium channel were identified in patients with BrS. Nowadays, several hundreds of mutations in at least 8 genes have been already associated with BrS. Functional consequences of many of these mutations on the molecular level have been revealed and, in some of them, even the consequences for the overall cardiac electrophysiology were suggested thank to the mathematical modelling. However, despite intense study of many scientific teams and formulation of several hypotheses, arrhythmogenic mechanisms in BrS have not been fully elucidated yet. This review provides a contemporary view of clinical symptoms, pathophysiology, diagnostics and therapy in BrS.

Genetics of cardiac arrhythmias

Continued research into the identification of mutated genes that cause inherited arrhythmogenic diseases has helped forward understanding into their pathophysiology. Over the last two decades the progress that has been made in the realm of genetic arrhythmias has made it possible not only for symptomatic patients to improve their outcomes, but also family members to better understand their risks and allow them in conjunction with their care providers to make the best decisions for their care. With this continued progress, significant changes will continue to occur in clinical practice. The advances in technology coupled with the improving understanding of genetically determined arrhythmias assists in earlier recognition of potentially fatal diseases, which leads to earlier implementation of treatment. It is the aim of this article to abridge the current knowledge of the genetic background of inherited arrhythmogenic diseases, namely long QT syndrome, short QT syndrome, Brugada syndrome and catecholaminergic polymorphic ventricular tachycardia. Pathogenesis and genotype-phenotype correlations are also discussed.