Autonomic and antiarrhythmic drug modulation of ST segment elevation in patients with Brugada syndrome

Fever associated with gastrointestinal shigellosis unmasks probable brugada syndrome

Since it was first described approximately 15 years ago, the Brugada Syndrome has spurred a significant quantity of interest in its underlying mechanism and physiology. The Brugada electrocardiographic pattern is characterized by right bundle branch block morphology and ST segment elevations in the right precordial leads with an absence of identifiable underlying structural heart disease. The syndrome is clinically significant since these patients are at a higher risk of developing malignant ventricular arrhythmias. One of the mechanisms behind the disorder involves mutations in specific myocardial sodium channels. Furthermore, these electrocardiographic changes appear to be temperature dependent. We present the case of a 35-year-old male who presented with intestinal Shigellosis and was also found to have Brugada-type electrocardiographic changes on ECG. The electrocardiographic changes that were present when the patient was admitted and febrile resolved following antibiotic therapy and defervescence.

Ventricular late potential in patients with apparently normal electrocardiogram; predictor of Brugada syndrome

BACKGROUND

Brugada syndrome can be overlooked due to its dynamic change in its electrocardiogram (ECG) manifestation. We hypothesized that positive ventricular late potential (VLP) in patients with nonspecific ECG would predict the inducible coved ST elevation (type-1 Brugada ECG) and the patients at high risk.

METHODS

Thirty-four patients of nonspecific ECG without structural heart disease were eligible for this study. All patients were referred for evaluation of syncopal episodes and/or cardiac arrest and/or frequent episodes of ventricular premature contractions. We assessed the correlation between baseline VLP and the alteration to a drug-induced type-1 Brugada ECG, and also evaluated the diagnostic accuracy of positive VLP in normal ECG subjects for the appearance of a drug-induced type-1 Brugada ECG.

RESULTS

Twenty-one patients presented positive VLP and 13 patients showed negative VLP. Parameters of VLP (fQRSd, RMS(40), LAS(40)) presented significant correlation with the alteration to a type-1 ECG by pilsicainide. VLP demonstrated high sensitivity and negative predictive value for the prediction of type-1 Brugada ECG. Furthermore, in their follow-up, at least two cases of ventricular fibrillation were recognized in 21 of positive VLP patients with apparently normal ECGs.

CONCLUSIONS

VLP in apparently normal ECG can predict the alteration to a drug-induced type-1 Brugada ECG and unmask the patients at risk.

The genetic basis of Brugada syndrome: a mutation update

Brugada syndrome (BrS) is a condition characterized by a distinct ST-segment elevation in the right precordial leads of the electrocardiogram and, clinically, by an increased risk of cardiac arrhythmia and sudden death. The condition predominantly exhibits an autosomal dominant pattern of inheritance with an average prevalence of 5:10,000 worldwide. Currently, more than 100 mutations in seven genes have been associated with BrS. Loss-of-function mutations in SCN5A, which encodes the alpha-subunit of the Na(v)1.5 sodium ion channel conducting the depolarizing I(Na) current, causes 15-20% of BrS cases. A few mutations have been described in GPD1L, which encodes glycerol-3-phosphate dehydrogenase-1 like protein; CACNA1C, which encodes the alpha-subunit of the Ca(v)1.2 ion channel conducting the depolarizing I(L,Ca) current; CACNB2, which encodes the stimulating beta2-subunit of the Ca(v)1.2 ion channel; SCN1B and SCN3B, which, in the heart, encodes beta-subunits of the Na(v)1.5 sodium ion channel, and KCNE3, which encodes the ancillary inhibitory beta-subunit of several potassium channels including the Kv4.3 ion channel conducting the repolarizing potassium I(to) current. BrS exhibits variable expressivity, reduced penetrance, and "mixed phenotypes," where families contain members with BrS as well as long QT syndrome, atrial fibrillation, short QT syndrome, conduction disease, or structural heart disease, have also been described.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Neurally mediated syncope as a cause of syncope in patients with Brugada electrocardiogram

INTRODUCTION

Patients with type 1 Brugada electrocardiogram (ECG) and an episode of syncope are diagnosed as symptomatic Brugada syndrome; however, all episodes of syncope may not be due to ventricular tachyarrhythmia.

METHODS AND RESULTS

Forty-six patients with type 1 Brugada ECG (all males, 51 +/- 13 years, 29 spontaneous, 17 Ic-drug induced), 20 healthy control subjects (all males, 35 +/- 11 years), and 15 patients with suspected neurally mediated syncope (NMS; 9 males, 54 +/- 22 years) underwent the head-up tilt (HUT) test. During the HUT test, 12-lead ECGs were recorded in all patients, and the heart rate variability was investigated in some patients. Sixteen (35%) of 46 patients with Brugada ECG, 2 (10%) of 20 control subjects, and 10 (67%) of 15 patients with suspected NMS showed positive responses to the HUT test. Although no significant differences were observed in HUT-positive rate among Brugada patients with documented VT (7/14; 50%), syncope (5/19; 26%) and asymptomatic patients (4/13; 31%), the HUT-positive rate was significantly higher in patients with documented VT (50%) and those with VT or no symptoms (11/27, 41%) compared to that in control subjects (10%) (P < 0.05). Augmentation of ST-segment amplitude (> or =0.05 mV) in leads V1-V3 was observed in 11 (69%) of 16 HUT-positive patients with Brugada ECG during vasovagal responses, and was associated with augmentation of parasympathetic tone following sympathetic withdrawal.

CONCLUSION

Thirty-five percent of patients with Brugada ECG showed vasovagal responses during the HUT test, suggesting that some Brugada patients have impaired balance of autonomic nervous system, which may relate to their syncopal episodes.

Systematic Assessment of Patients With Unexplained Cardiac Arrest

Background— Cardiac arrest without evident cardiac disease may be caused by subclinical genetic conditions. Provocative testing to unmask a phenotype is often necessary to detect primary electrical disease, direct genetic testing, and perform family screening.

Methods and Results— Patients with apparently unexplained cardiac arrest and no evident cardiac disease (normal cardiac function on echocardiogram, no evidence of coronary artery disease, and a normal ECG) underwent systematic evaluation that included cardiac magnetic resonance imaging, signal-averaged ECG, exercise testing, drug challenge, and selective electrophysiological testing. Diagnostic criteria were based on accepted criteria or provocation of the characteristic clinical features for long-QT syndrome, catecholaminergic polymorphic ventricular tachycardia, Brugada syndrome, early repolarization, arrhythmogenic right ventricular cardiomyopathy, coronary spasm, and myocarditis. Sixty-three patients in 9 centers were enrolled (age 43.0±13.4 years, 29 women). A diagnosis was obtained in 35 patients (56%): Long-QT syndrome in 8, catecholaminergic polymorphic ventricular tachycardia in 8, arrhythmogenic right ventricular cardiomyopathy in 6, early repolarization in 5, coronary spasm in 4, Brugada syndrome in 3, and myocarditis in 1. Targeted genetic testing demonstrated evidence of causative mutations in 9 (47%) of 19 patients. Screening of 64 family members of these patients identified 15 affected individuals who were treated (24%). The remaining 28 patients (44%) were considered to have idiopathic ventricular fibrillation.

Conclusions— Systematic clinical testing, including drug provocation and advanced imaging, results in unmasking of the cause of apparently unexplained cardiac arrest in >50% of patients. This approach assists in directing genetic testing to diagnose genetically mediated arrhythmia syndromes, which results in successful family screening.

Response to intravenous ajmaline: a retrospective analysis of 677 ajmaline challenges

AIMS

The diagnostic type I ECG in Brugada syndrome (BS) is often concealed and fluctuates between the diagnostic and non-diagnostic pattern. Challenge with intravenous ajmaline is used to unmask the diagnostic Brugada ECG. The aim of this study was to evaluate the safety of the test and to identify predictors for the response to an intravenous ajmaline challenge.

METHODS AND RESULTS

In four tertiary referral centres, 677 consecutive patients underwent an intravenous ajmaline challenge for diagnosis or exclusion of BS in accordance with the recommendations of the Brugada consensus conferences. Two hundred and sixty-two ajmaline challenges (39%) were positive. Male gender, familial BS, sudden cardiac arrest (SCA), first-degree AV-block, basal saddleback type ECG, and basal right bundle branch block were identified as predictors for a positive ajmaline challenge. A predictor for negative ajmaline test was the absence of ST-segment elevation at baseline. Six of 12 patients who had experienced SCA, and five of 25 patients with a familial sudden death exhibited a positive response to ajmaline. Only one patient (0.15%) developed sustained ventricular tachyarrhythmias (ventricular fibrillation) during ajmaline challenge, which was terminated by a single external defibrillator shock.

CONCLUSION

Ajmaline challenge is a safe procedure to unmask the electrocardiographic pattern of BS. Electrocardiographic and clinical parameters were identified to predict patients' response to ajmaline. The results of this study guide the clinician in which setting an ajmaline challenge is an appropriate diagnostic step.

Drugs and Brugada syndrome patients: review of the literature, recommendations, and an up-to-date website (www.brugadadrugs.org)

BACKGROUND

Worldwide, the Brugada syndrome has been recognized as an important cause of sudden cardiac death in individuals at a relatively young age. Importantly, many drugs have been reported to induce the characteristic Brugada syndrome-linked ECG abnormalities and/or (fatal) ventricular tachyarrhythmias.

OBJECTIVE

The purpose of this study was to review the literature on the use of drugs in Brugada syndrome patients, to make recommendations based on the literature and on expert opinion regarding drug safety, and to ensure worldwide online and up-to-date availability of this information to all physicians who treat Brugada syndrome patients.

METHODS

We performed an extensive review of the literature, formed an international expert panel to produce a consensus recommendation to each drug, and initiated a website (www.brugadadrugs.org).

RESULTS

The literature search yielded 506 reports for consideration. Drugs were categorized into one of four categories: (1) drugs to be avoided (n = 18); (2) drugs preferably avoided (n = 23); (3) antiarrhythmic drugs (n = 4); and (4) diagnostic drugs (n = 4). Level of evidence for most associations was C (only consensus opinion of experts, case studies, or standard-of-care) as there are no randomized studies and few nonrandomized studies in Brugada syndrome patients.

CONCLUSION

Many drugs have been associated with adverse events in Brugada syndrome patients. We have initiated a website (www.brugadadrugs.org) to ensure worldwide availability of information on safe drug use in Brugada syndrome patients.

Usefulness of multichannel Holter ECG recording in the third intercostal space for detecting type 1 Brugada ECG: comparison with repeated 12-lead ECGs

INTRODUCTION

Type 1 Brugada ECG is essential for the diagnosis of Brugada syndrome. We aimed to evaluate the usefulness of multichannel Holter ECG recording in the third intercostal space for detecting type 1 Brugada ECG.

METHODS AND RESULTS

We enrolled 60 consecutive individuals with type 1 Brugada ECG and 31 individuals with type 2 or 3 Brugada ECG, in the presence or absence of Na+ channel blockers. All individuals underwent 12-lead ECGs recorded in the standard position and the third intercostal space at least 5 times every 3 months (4L-ECGs, 3L-ECGs, respectively) and multichannel Holter ECG. On multichannel Holter ECG, the precordial electrodes were attached at standard positions (4L-Holter) and the third intercostal space (3L-Holter) for leads V1 and V2. Among the 60 individuals, type 1 Brugada ECG in 4L-ECGs, 3L-ECGs, 4L-Holter, and 3L-Holter was detected in 15 (25%), 26 (43.3%), 23 (38.3%), and 33 individuals (55%), respectively, whereas detected in none of the 31 individuals. The documented duration of type 1 Brugada ECG on 3L-Holter was significantly longer than that on 4L-Holter (700 +/- 467 vs 372 +/- 422 min; P = 0.01, 3L-Holter vs 4L-Holter, respectively), and type 1 Brugada ECG was most frequently observed between 6 pm and 12 pm. Neither the presence nor the duration of the appearance of type 1 Brugada ECG differed significantly between symptomatic and asymptomatic individuals.

CONCLUSION

Multichannel Holter ECG recording in the third intercostal space is more sensitive and useful for the diagnosis of type 1 Brugada ECG than repeated 12-lead ECGs or multichannel Holter ECG in the standard position.

Electrical storm in Brugada syndrome successfully treated with orciprenaline; effect of low-dose quinidine on the electrocardiogram

We report a case of an electrical storm occurring in a patient implanted with a cardioverter defibrillator for symptomatic Brugada syndrome. Recurrent ventricular fibrillation was initiated by short-coupled premature ventricular beats of right ventricular origin, associated with a fixed Brugada type 2 electrocardiographic pattern. Low-dose orciprenaline application as an intravenous bolus followed by an infusion inhibited the recurrence of ventricular fibrillation and normalized the electrocardiographic pattern. Low-dose oral quinidine had only a moderate effect on the ST-elevation.

Risk stratification of the patients with Brugada type electrocardiogram: a community-based prospective study

AIMS

Risk stratification of patients with Brugada electrocardiogram (ECG) is being strongly debated. Conflicting results have been suggested from international registries, which enrolled non-consecutive cases, studied with different programmed electrical stimulation (PES) protocols. The aim of this study was to prospectively evaluate the incidence of arrhythmic events and the prognostic role of clinical presentation, ECG, and of a standardized PES protocol in consecutive cases from a community-based population.

METHODS AND RESULTS

A total of 166 consecutive patients (45 +/- 14 years) with Brugada ECG were enrolled. Type 1 ECG was observed spontaneously in 72 (43%) and after pharmacological testing in 94 (57%). One hundred and three (62%) were asymptomatic, 58 (35%) had syncope, and five (3%) had a prior cardiac arrest. One hundred and thirty-five (81%) underwent PES with two extra stimuli up to ventricular refractoriness and 34% had ventricular fibrillation (VF) induced. Arrhythmic events occurred in nine patients at a mean follow-up of 30 +/- 21 months (2.2 events per 100 person-year): in three (60%) patients with aborted sudden death (aSD), five (8.6%) of those with syncope, and one (1%) of the asymptomatic. The only predictors of events were a history of syncope or aSD (P = 0.02) and induction at PES (P = 0.004).

CONCLUSION

Clinical presentation is the most important parameter in the risk stratification of patients with Brugada ECG. Programmed electrical stimulation seems valuable, particularly in patients with previous syncope.

Dynamic change in ST-segment and spontaneous occurrence of ventricular fibrillation in Brugada syndrome with a novel nonsense mutation in the SCN5A gene during long-term follow-up

A 67-year-old male underwent genetic testing under the diagnosis of Brugada syndrome because of recurrent ventricular fibrillation with coincident ST-segment elevation in either right precordial, inferior leads or both since the age of 55 years. Screening of gene mutations using denaturing high-performance liquid chromatography (DHPLC) and direct sequencing identified a novel nonsense mutation (R179X) of SCN5A in a heterozygous manner. The functional assay for the identified mutation, using a whole-cell patch clamp in the heterologous expression system, revealed that the nonsense mutation, located in the second transmembrane segment of the first domain (DI-S2) of the alpha-subunit, failed to synthesize the complete structure of the cardiac sodium channel, thus causing the non-functional channel. Coding effects by the gene mutation was altered during the 12-year follow-up, which might affect the clinical features of the patient through the ion channel density in the ventricle, dynamics of repolarization abnormality and conduction disturbance.

Brugada syndrome: recent advances and controversies

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

Seasonal and circadian distributions of ventricular fibrillation in patients with Brugada syndrome

BACKGROUND

It is well-known that the incidence of ventricular tachyarrhythmias is the highest in winter and during the daytime in patients with structural heart disease. However, little is known about the seasonal and circadian distributions of ventricular fibrillation (VF) in patients with Brugada syndrome.

OBJECTIVE

The aim of this study was to investigate seasonal and circadian distributions of VF in patients with Brugada syndrome.

METHODS

We analyzed the data of appropriate shock episodes for VF recorded by an implantable cardioverter-defibrillator (ICD) in patients with Brugada syndrome.

RESULTS

Among 62 consecutive Brugada syndrome patients with an ICD (48 +/- 14 years, 58 males), 19 patients had at least one episode of an appropriate ICD shock due to VF during a mean follow-up of 70 +/- 36 months, and 98 episodes were evaluated as isolated VF. There was a significant peak between March and June (P = .03). As for the circadian variation, significantly more VF occurred from midnight to 6:00 (P <.0001). Electrical storms of VF occurred in seven patients. The seasonal and circadian variations of electrical storms were similar to those of the isolated VF episodes.

CONCLUSIONS

In patients with Brugada syndrome, there was a significant seasonal peak from spring to early summer and a significant circadian peak from midnight to early morning in terms of the occurrences of VF.

Brugada syndrome

Since its first description in 1992 as a new clinical entity, the Brugada syndrome has aroused great interest among physicians and basic scientists. Two consensus conferences held in 2002 and 2005 helped refine the current accepted definite diagnostic criteria for the syndrome, briefly, the characteristic ECG pattern (right bundle branch block and persistent ST segment elevation in right precordial leads) together with the susceptibility for ventricular fibrillation and sudden death. In the last years, clinical and basic research have provided very valuable knowledge on the genetic basis, the cellular mechanisms responsible for the typical ECG features and the electrical susceptibility, the clinical particularities and modulators, the diagnostic value of drug challenge, the risk stratification of sudden death (possibly the most controversial issue) and, finally, the possible therapeutic approaches for the disease. Each one of these points is discussed in this review, which intends to provide updated information supplied by recent clinical and basic studies.

Therapeutic hypothermia after out-of-hospital cardiac arrest due to Brugada syndrome

A 56-year-old man was admitted to our hospital after successful resuscitation for out-of-hospital cardiac arrest. Electrocardiogram on admission showed right bundle branch block and ST segment elevation in leads V1-3. Subsequent intravenous infusion of isoproterenol rapidly resolved ST segment elevation, suggesting Brugada syndrome. Therapeutic hypothermia, that was performed with a target temperature of 34.0 degrees C did not induce ST segment elevation in leads V1-3. The J-ST segment elevation rather became much more normal, suggesting a beneficial effect of mild therapeutic hypothermia. Serial ECG showed the temporal variation of ST segment elevation, and pilsicainide challenge test showed the occurrence of ST segment elevation, confirming the diagnosis of Brugada syndrome. Clinical observation suggested that mild therapeutic hypothermia reversed the Brugada phenotype through the prevention of fever as well as being indicated for cerebral protection after cardiac arrest. In conclusion, therapeutic hypothermia with a temperature of 34.0 degrees C can be used safely in Brugada syndrome.

The E1784K mutation in SCN5A is associated with mixed clinical phenotype of type 3 long QT syndrome

Phenotypic overlap of type 3 long QT syndrome (LQT3) with Brugada syndrome (BrS) is observed in some carriers of mutations in the Na channel SCN5A. While this overlap is important for patient management, the clinical features, prevalence, and mechanisms underlying such overlap have not been fully elucidated. To investigate the basis for this overlap, we genotyped a cohort of 44 LQT3 families of multiple ethnicities from 7 referral centers and found a high prevalence of the E1784K mutation in SCN5A. Of 41 E1784K carriers, 93% had LQT3, 22% had BrS, and 39% had sinus node dysfunction. Heterologously expressed E1784K channels showed a 15.0-mV negative shift in the voltage dependence of Na channel inactivation and a 7.5-fold increase in flecainide affinity for resting-state channels, properties also seen with other LQT3 mutations associated with a mixed clinical phenotype. Furthermore, these properties were absent in Na channels harboring the T1304M mutation, which is associated with LQT3 without a mixed clinical phenotype. These results suggest that a negative shift of steady-state Na channel inactivation and enhanced tonic block by class IC drugs represent common biophysical mechanisms underlying the phenotypic overlap of LQT3 and BrS and further indicate that class IC drugs should be avoided in patients with Na channels displaying these behaviors.

Lidocaine-induced Brugada syndrome phenotype linked to a novel double mutation in the cardiac sodium channel

Brugada syndrome has been linked to mutations in SCN5A. Agents that dissociate slowly from the sodium channel such as flecainide and ajmaline unmask the Brugada syndrome electrocardiogram and precipitate ventricular tachycardia/fibrillation. Lidocaine, an agent with rapid dissociation kinetics, has previously been shown to exert no effect in patients with Brugada syndrome. We characterized a novel double mutation of SCN5A (V232I in DI-S4+L1308F in DIII-S4) identified in a rare case of lidocaine (1 mg/kg)-induced Brugada syndrome. We studied lidocaine blockade of I(Na) generated by wild-type and V232I+L1308F mutant cardiac sodium channels expressed in mammalian TSA201 cells using patch clamp techniques. Despite no significant difference in steady-state gating parameters between V232I+L1308F and wild-type sodium currents at baseline, use-dependent inhibition of I(Na) by lidocaine was more pronounced in V232I+L1308F versus wild-type (73.0+/-0.1% versus 18.23+/-0.04% at 10 micromol/L measured at 10 Hz, respectively). A dose of 10 micromol/L lidocaine also caused a more negative shift of steady-state inactivation in V232I+L1308F versus wild-type (-14.1+/-0.3 mV and -4.8+/-0.3 mV, respectively). The individual mutations produced a much less accentuated effect. We report the first case of lidocaine-induced Brugada electrocardiogram phenotype. The double mutation in SCN5A, V232I, and L1308F alters the affinity of the cardiac sodium channel for lidocaine such that the drug assumes Class IC characteristics with potent use-dependent block of the sodium channel. Our results demonstrate an additive effect of the 2 missense mutations to sensitize the sodium channel to lidocaine. These findings suggest caution when treating patients carrying such genetic variations with Class I antiarrhythmic drugs.

Sudden cardiac death secondary to antidepressant and antipsychotic drugs

A number of antipsychotic and antidepressant drugs are known to increase the risk of ventricular arrhythmias and sudden cardiac death. Based largely on a concern over QT prolongation and the development of life-threatening arrhythmias, a number of antipsychotic drugs have been temporarily or permanently withdrawn from the market or their use restricted. Some antidepressants and antipsychotics have been linked to QT prolongation and the development of Torsade de pointes arrhythmias, whereas others have been associated with a Brugada syndrome phenotype and the development of polymorphic ventricular arrhythmias. This review examines the mechanisms and predisposing factors underlying the development of cardiac arrhythmias, and sudden cardiac death, associated with antidepressant and antipsychotic drugs in clinical use.

Successful radiofrequency catheter ablation for electrical storm of ventricular fibrillation in a patient with Brugada syndrome

The case of a 41-year-old man with Brugada syndrome (BS) who suffered electrical storms (ES) of ventricular fibrillation (VF) is presented. Although intravenous infusion of isoproterenol (ISP) suppressed the VF occurrence, he consistently experienced recurrence of VF following discontinuation of ISP infusion. Quinidine and cilostazol were ineffective. An analysis of VF episodes on electrocardiogram monitoring revealed that the QRS morphology of the first beat of all VF episodes was identical to that of premature ventricular complexes (PVCs) with a left bundle branch-block morphology and inferior axis, which occurred repetitively before the episodes of VF and were recorded throughout the day. In addition, stored electrograms from the implantable cardioverter defibrillator showed that the first beat of all VF episodes had the same morphology. On electrophysiological study, the VF-triggering PVC was found to originate from the posterior portion of the right ventricular outflow tract area and their elimination, which was achieved with radiofrequency catheter ablation (RFCA), resulted in the suppression of ES. Although several other PVCs were still observed, the patient has been free of VF during the 29-month follow-up period. This case indicates that RFCA of VF-triggering PVCs may be useful in the treatment of drug-resistant ES in patients with BS.

Sodium channel blockers enhance the temporal QT interval variability in the right precordial leads in Brugada syndrome

BACKGROUND

Temporal QT interval variability is associated with sudden cardiac death. The purpose of this study was to evaluate temporal QT interval variability in Brugada syndrome (BS).

METHODS

We measured QT and RR intervals in precordial leads (V(1)-V(6)) based on 12-beat resting ECG recordings from 16 BS patients (B group) with spontaneous ST elevation in right precordial leads (V(1)-V(2)) and from 10 patients with normal hearts (C group). We measured the response in B group before and after administration of pilsicainide (1 mg/kg). The standard deviation (QT-SD, RR-SD) of the time domain and total frequency power (QT-TP, RR-TP) were calculated for all precordial leads, and the latter was to analyze the frequency domain.

RESULTS

The right precordial leads in BS exhibited an additional and prominent ST elevation (coved-type) after pilsicainide administration. Both QT-SD and QT-TP values were significantly more increased in B, than in C (5.1 +/- 1.2 vs 3.6 +/- 0.2 and 23.4 +/- 2.9 vs 12.3 +/- 1.7 msec(2), P < 0.01, respectively) and after pilsicainide administration in B. (5.1 +/- 0.4 vs 3.9 +/- 0.3, 25.8 +/- 3.4 vs 16.3 +/- 2.6 msec(2), P < 0.01, respectively) However, QT-SD and QT-TP did not significantly change in any of other leads (V(3)-V(6)) and RR-SD and RR-TP were similar for both groups, as well as after intravenous pilsicainide administration in B.

CONCLUSIONS

The temporal QT interval variability was identified in BS. Moreover, sodium channel blocker induced temporal fluctuation in QT interval and it may possibly provide a substrate for ventricular arrhythmia in BS patients.

Dynamic changes in T-wave amplitude during tilt table testing: correlation with outcomes

BACKGROUND

Changes in autonomic tone may play a role in syncope. Autonomic tone has been shown to affect cardiac repolarization in the ECG. Changes in the T wave can be seen during head-up tilt table (HUT) testing with unknown significance or relationship to outcomes.

METHODS

Twelve-lead ECGs during HUT testing from 150 patients were reviewed from a prospectively collected registry database. ECGs during supine-rest, 30-45-70 degrees tilt, and 5-minute supine recovery were reviewed. Changes in the T wave, that is, decreased amplitude with or without becoming negative or flipping from negative to positive, were recorded for each stage. Outcomes of the HUT test include nondiagnostic, postural orthostatic hypotension (POH), postural orthostatic tachycardia syndrome (POTS), and vasovagal response (VVR). Age (Younger: <50 year old; Older: > or = 50 year old) and gender were analyzed.

RESULTS

Of 150 patients (108 women; 80 Younger), 135 had T-wave changes during HUT; changes resolved in 114 patients during supine recovery. Changes mostly occurred in inferior and anterolateral leads. POH occurred in 114 patients, POTS in 67, and VVR in 30. T-wave changes in V1 inversely correlated with POH (P = 0.005). T-wave changes in inferior leads II, III, aVF and in anterolateral leads V3-V6 positively correlated with POTS (P < 0.05). Female gender and younger age correlated with POTS independent of the leads (P < 0.05). Concomitant T-wave changes in V5 and V6 correlated with VVR; changes in aVF also correlated with VVR (P < 0.05).

CONCLUSIONS

Dynamic T-wave changes during HUT testing in inferior and anterolateral leads are associated with POTS and VVR independent of age and gender. Changes in autonomic tone may play a role and need further study.

Clinical characteristics and risk stratification in symptomatic and asymptomatic patients with brugada syndrome: multicenter study in Japan

BACKGROUND

Neither the clinical characteristics nor risk stratification in Brugada syndrome have been clearly determined. We compared the clinical and ECG characteristics of symptomatic and asymptomatic patients with Brugada syndrome to identify new markers for high-risk patients.

METHODS

A total of 188 consecutive individuals with Brugada syndrome (mean age 53 +/- 14 years, 178 males) were enrolled in the Japan Idiopathic Ventricular Fibrillation Study (J-IVFS). Clinical and ECG characteristics were evaluated in three groups of patients: Ventricular fibrillation (VF) group: patients with documented VF (N = 33); Syncope (Sy) group: patients with syncope without documented VF (N = 57); and asymptomatic (As) group: subjects without symptoms (N = 98). Their prognostic parameters were evaluated over a 3-year follow-up period.

RESULTS

(1) Clinical characteristics: incidence of past history of atrial fibrillation (AF) was significantly higher in the VF and Sy groups than in the AS group (P = 0.04). (2) On 12-lead ECG, r-J interval in lead V2 and QRS duration in lead V6 were longest in the VF group (P = 0.001, 0.002, respectively). (3) Clinical follow-up: during a mean follow-up period of 37 +/- 16 months, incidences of cardiac events (sudden death and/or VF) were higher in the symptomatic (VF/Sy) groups than in the As group (P < 0.0001). The r-J interval in lead V2 >/= 90 ms and QRS duration in lead V6 >/= 90 ms were found to be possible predictors of recurrence of cardiac events in symptomatic patients.

CONCLUSIONS

Prolonged QRS duration in precordial leads was prominent in symptomatic patients. This ECG marker may be useful for distinguishing high- from low-risk patients with Brugada syndrome.

Influence of meals on variations of ST segment elevation in patients with Brugada syndrome

BACKGROUND

Glucose-induced insulin secretion is one of the contributing factors to fluctuation of ST segment elevation in Brugada syndrome.

OBJECTIVES

The purpose of this study was to explore the influence of meals on variations of ST elevation in Brugada syndrome.

METHODS

We assessed changes of ST segment elevation in lead V1-3 on ECG before and after taking meals, at midnight, and at 3:00 a.m. in 20 patients with Brugada syndrome. Plasma glucose, insulin, and K(+) concentrations were measured. Variations of ST elevation were defined as morphological changes and/or augmentation of ST segment level by >1.0 mm.

RESULT

Variations of ST segment morphology or elevation level after meals were observed in 15 of 20 patients (75%). ST elevation was augmented most markedly after dinner (3.3 +/- 1.7 mm) and decreased both at midnight (2.6 +/- 1.3 mm: P < 0.01 vs after dinner) and at 3:00 a.m. (2.4 +/- 1.2 mm: P < 0.01 vs after dinner). Morphologic changes and elevation levels of ST segment were associated with changes in glucose-induced insulin levels after meals, being highest after dinner (47 +/- 33 microU/mL) and decreasing significantly at midnight (7 +/- 4 microU/mL) and at 3:00 a.m. (5 +/- 2 microU/mL). There were no correlations between ST elevation and changes in serum K(+) level or heart rate.

CONCLUSIONS

The present findings suggest that variations of ST elevation are frequently associated with meals. Aggravation of ST elevation is most prominent in the evening to night after dinner rather than the period between midnight and early morning. This information may help to predict event times at high risk for life-threatening arrhythmias in Brugada syndrome.

Brugada syndrome in the presence of coronary artery disease and parasympathomimetic drug therapy

Brugada pattern ECG changes have been described in various disease states and drug therapies, including electrolyte abnormalities, myocardial pathology, medications, and mechanical abnormalities. Therefore, the diagnosis of Brugada syndrome cannot be made in the presence of confounding variables according to prevailing guidelines. We present a case report which illustrates two important principles regarding Brugada syndrome, the dynamic ECG manifestations and the elimination of confounding variables (in this case significant coronary artery disease and cholinergic pharmacotherapy) prior to definitive diagnosis.

Postprandial Augmentation of Bradycardia-Dependent ST Elevation in Patients with Brugada Syndrome

INTRODUCTION

In patients with Brugada syndrome, the circadian variation of ST elevation could be modulated by the autonomic nervous activity and RR interval. Recently, glucose-induced insulin secretion was also reported to contribute to fluctuation of ST elevation. Therefore, we assessed the effects of taking meals on the ST-RR relationship in the daily life of patients with Brugada syndrome.

METHODS AND RESULTS

Twenty-eight patients with Brugada syndrome, who had the type I ST elevation, were categorized into 12 symptomatic and 16 asymptomatic patients. Unipolar lead (V2) Holter ECG was recorded and ST-RR relationships for a 2-hour period were compared before and after each meal. From ST-RR linear regression lines, ST-RR slope (mm/sec) and ST(mm) at RR intervals of both 0.6 seconds and 1.2 seconds (ST(0.6) and ST(1.2)) were determined. The ST-RR slope increased significantly after lunch (2.6 +/- 0.4 vs 4.4 +/- 1.2, P < 0.05) and dinner (2.1 +/- 1.0 vs 5.2 +/- 1.9, P < 0.01) in symptomatic patients, but not in asymptomatic patients. In both groups, ST(0.6) was not different before or after each meal. However, ST(1.2) increased after each meal in symptomatic patients. After dinner, ST(1.2) was significantly higher in symptomatic patients than in asymptomatic patients (5.0 +/- 2.7 vs 3.6 +/- 0.8, P < 0.05). Postprandial increase in both ST-RR slope and ST(1.2) was greatest at dinner in symptomatic patients; however, this tendency was not seen in asymptomatic patients.

CONCLUSIONS

In symptomatic patients with Brugada syndrome, bradycardia-dependent augmentation of ST elevation was enhanced for the postprandial period, especially after dinner. This could be related to occurrence of ventricular fibrillation in the late evening.

Brugada pattern electrocardiogram associated with supratherapeutic phenytoin levels and the risk of sudden death

The emergence of Brugada pattern on electrocardiogram in response to class IA or IC antiarrhythmic agents is widely utilized to diagnose concealed Brugada syndrome and recognized as a risk factor for sudden death. Phenytoin, a class IB antiarrhythmic agent, has not been reported to induce Brugada pattern. We report a patient who presented with Brugada electrocardiogram at supratherapeutic phenytoin level. Considering that patients with syncope may falsely be labeled to have seizures and some epilepsy patients are at increased risk of sudden death, all patients with supratherapeutic phenytoin level should be evaluated with an electrocardiogram for emergence of Brugada pattern.

Ionic basis of pharmacological therapy in Brugada syndrome

An implantable cardioverter-defibrillator is considered the only effective therapy to terminate ventricular arrhythmias in symptomatic patients with Brugada syndrome. However, it does not prevent future arrhythmic episodes. Only antiarrhythmic drug therapy can prevent them. There have been several reports of a beneficial effect of oral quinidine in both asymptomatic and symptomatic patients. Other possible beneficial oral agents could be I(to) blockers. Intravenous isoproterenol has been reported to be especially useful in abolishing arrhythmic storms in emergency situations. Also, isolated case reports on the usefulness of cilostazol, sotalol, and mexiletine have been described. The present article reviews the mechanisms by which these drugs may act and their possible role in the pharmacotherapy of this disease.

Syndrome de Brugada

Brugada syndrome is characterized clinically by the onset of syncopes or sudden death related to ventricular tachyarrhythmias in patients with a structurally normal heart. Its electrocardiographic features include right bundle branch bloc and ST-segment elevations in the precordial leads V1-V3. The estimated prevalence is 1 per 1000 in Asian countries and probably lower elsewhere: Asia is probably a birthplace of the syndrome. Its transmission is autosomal dominant with variable penetrance. Mutations have been identified in a gene coding for the alpha subunit of the sodium channel (SCN5A) in only 25% of cases. These genetic abnormalities cause a reduction of the density of the sodium current and explain the aggravation of electrocardiographic abnormalities caused by antiarrhythmic sodium channel blockers. Prognosis is very serious in symptomatic patients: prevention of sudden death requires implantation of an automatic defibrillator. The treatment decision is much more difficult for asymptomatic subjects with no family history.