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Exercise-induced Ventricular Tachycardia/Ventricular Fibrillation in the Normal Heart: Risk Stratification and Management

Exercise-induced ventricular tachycardia (VT) rarely occurs in the absence of organic heart disease. Idiopathic monomorphic VT has an excellent prognosis. The main aspect of the risk stratification process is recognizing subtle forms of organic heart disease, particularly arrhythmogenic right ventricular cardiomyopathy. Exercise-induced polymorphic VT is potentially malignant. Exercise-induced polymorphic VT has also been seen in mitral valve prolapse. Some patients with stable coronary disease, and even healthy athletes, sometimes have short bursts of polymorphic VT during exercise tests but these arrhythmias are usually not reproducible during repeated testing and have unknown long-term clinical significance.

Management of Brugada Syndrome: Thirty-Three-Year Experience Using Electrophysiologically Guided Therapy With Class 1A Antiarrhythmic Drugs

BACKGROUND

Information on long-term clinical outcome of patients with Brugada syndrome treated with electrophysiologically guided class 1A antiarrhythmic drugs (AAD) is limited.

METHODS AND RESULTS

An aggressive protocol of programmed ventricular stimulation was performed in 96 patients with Brugada syndrome (88% males; mean age, 39.8±15.9 years). Ten patients were cardiac arrest survivors, 27 had presented with syncope, and 59 were asymptomatic. Ventricular fibrillation was induced in 66 patients, including 100%, 74%, and 61% of patients with cardiac arrest, syncope, and no symptoms, respectively. All but 6 of the 66 patients with inducible ventricular fibrillation underwent electrophysiological testing on quinidine (n=54), disopyramide (n=2), or both (n=4). Fifty-four (90%) patients were electrophysiological responders to >1 AAD with similar efficacy rates (≈90%) in all patients groups. Patients with no inducible ventricular fibrillation at baseline were left on no therapy. After a mean follow-up of 113.3±71.5 months, 92 patients were alive, whereas 4 died from noncardiac causes. No arrhythmic event occurred during class 1A AAD therapy in any of electrophysiological drug responders and in patients with no baseline inducible ventricular fibrillation. Arrhythmic events occurred in only 2 cardiac arrest survivors treated with implantable cardioverter-defibrillator alone but did not recur on quinidine. All cases of recurrent syncope (n=12) were attributed to a vasovagal (n=10) or nonarrhythmic mechanism (n=2). Class 1A AAD therapy resulted in 38% incidence of side effects that resolved after drug discontinuation.

CONCLUSIONS

Our data suggest that electrophysiologically guided class 1A AAD treatment has a place in our therapeutic armamentarium for all types of patients with Brugada syndrome.

Diagnostic dilemmas: overlapping features of brugada syndrome and arrhythmogenic right ventricular cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy (ARVC) and Brugada syndrome are distinct clinical entities which diagnostic criteria exclude their coexistence in individual patients. ARVC is a myocardial disorder characterized by fibro-fatty replacement of the myocardium and ventricular arrhythmias. In contrast, the Brugada syndrome has long been considered a functional cardiac disorder: no gross structural abnormalities can be identified in the majority of patients and its electrocardiographic hallmark of coved-type ST-segment elevation in right precordial leads is dynamic. Nonetheless, a remarkable overlap in clinical features has been demonstrated between these conditions. This review focuses on this overlap and discusses its potential causes and consequences.

Brugada syndrome presenting with sustained monomorphic ventricular tachycardia

Typically Brugada syndrome presents with either ventricular fibrillation or polymorphic ventricular tachycardia that may result in sudden death or syncope in patients without any structural heart disease. We report the case of a patient with Brugada syndrome who presented atypically with recurrent presyncope following physical exertion due to sustained monomorphic ventricular tachycardia, which appeared to be sensitive to both adenosine and catecholamine. He refused ICD implantation but remained asymptomatic on treatment with a beta-blocker.

Efficacy of quinidine in high-risk patients with Brugada syndrome

BACKGROUND

Automatic implantable cardioverter-defibrillator therapy is considered the only effective treatment for high-risk patients with Brugada syndrome. Quinidine depresses I(to) current, which may play an important role in the arrhythmogenesis of this disease.

METHODS AND RESULTS

The effects of quinidine bisulfate (mean dose, 1483+/-240 mg) on the prevention of inducible and spontaneous ventricular fibrillation (VF) were prospectively evaluated in 25 patients (24 men, 1 woman; age, 19 to 80 years) with Brugada syndrome. There were 15 symptomatic patients (including 7 cardiac arrest survivors and 7 patients with unexplained syncope) and 10 asymptomatic patients. All 25 patients had inducible VF at baseline electrophysiological study. Quinidine prevented VF induction in 22 of the 25 patients (88%). After a follow-up period of 6 months to 22.2 years, all patients are alive. Nineteen patients were treated with quinidine for 6 to 219 months (mean+/-SD, 56+/-67 months). None had an arrhythmic event, although 2 had non-arrhythmia-related syncope. Administration of quinidine was associated with a 36% incidence of side effects that resolved after drug discontinuation.

CONCLUSIONS

Quinidine effectively prevents VF induction in patients with Brugada syndrome. Our data suggest that quinidine also suppresses spontaneous arrhythmias and could prove to be a safe alternative to automatic implantable cardioverter-defibrillator therapy for a substantial proportion of patients with Brugada syndrome. Randomized studies comparing these two therapies seem warranted.

[Concurrent long QT and Brugada syndrome in a single patient]

We present a 61-year-old patient with previous cardiac arrest and frequent syncopal spells. ECG showed a typical Brugada pattern and a QTc interval of 425 ms. During programmed ventricular stimulation a self-limited syncopal polymorphic ventricular tachycardia was induced. On diagnosis of the Brugada syndrome an implantable cardioverter defibrillator was implanted. Two days later two episodes of polimorphic ventricular arrhythmia were converted by the device. The ECG at this time showed a prolonged QTc of 500 ms in addition to a typical Brugada pattern. Atenolol was started and after a 36-month follow-up the patient has remained asymptomatic without arrhythmic events. In conclusion, this patient has the Brugada syndrome and also fulfills the clinical and ECG characteristics of the Long QT syndrome. These findings suggest a genetic link between the two syndromes.

Sudden death in high-risk family members: Brugada syndrome

Brugada syndrome (an electrocardiographic pattern of right bundle branch block, ST segment elevation in leads V1 to V3, and sudden death) is genetically determined and caused by mutations in the cardiac ion channels. The mode of inheritance of the disease is autosomal dominant in half of familial forms. Sudden death may, however, occur from a variety of causes in relatives and patients with this syndrome. Twenty-five Flemish families with this syndrome with a total of 334 members were studied. Affected members were recognized by means of the typical electrocardiogram of the syndrome, either occurring spontaneously or after the intravenous administration of antiarrhythmic drugs. Sudden deaths in these families were classified as related or not to the syndrome by analysis of the data at the time of the event, mode of inheritance of the disease, and data provided by survivors. Of the 25 families with the syndrome, 18 were symptomatic (at least 1 sudden death related to the syndrome) and 7 were asymptomatic (no sudden deaths related to the syndrome). In total, there were 42 sudden cardiac deaths (12% incidence). Twenty-four sudden deaths were related to the syndrome and all happened in symptomatic families. Eighteen sudden deaths (43% of total sudden deaths) were not related to the syndrome (9 cases) or were of unclear cause (9 cases). Three of them occurred in 2 asymptomatic families and the remaining 15 in 5 symptomatic families. A total of 24 of the 50 affected members (47%) and 18 of the 284 unaffected members (6%) had aborted sudden death. This difference in the incidence of sudden death was statistically significant (p <0.0001). Patients with aborted sudden death caused by the syndrome were younger than patients with sudden death of other or unclear causes (38 +/- 4 years vs 59 +/- 3 years respectively; p = 0.0003). In families at high risk of sudden death because of genetically determined diseases, the main cause of sudden death remains the disease itself. However, almost half of sudden deaths are caused by unrelated diseases or from unclear causes. Accurate classification of the causes of sudden death is mandatory for appropriate analysis of the causes of death when designing preventive treatments.

Prevalence of the Brugada sign in idiopathic ventricular fibrillation and healthy controls

OBJECTIVE

To determine the prevalence of the Brugada sign (right bundle branch block with ST elevation in V1-V3) in idiopathic ventricular fibrillation and in an age matched healthy population.

DESIGN

ECGs from 39 consecutive patients with idiopathic ventricular fibrillation and 592 healthy controls were reviewed. They were classified as definite, questionable, and no Brugada sign (according to predetermined criteria) by four investigators blinded to the subjects' status.

RESULTS

Eight patients (21%) with idiopathic ventricular fibrillation but none of the 592 controls had a definite Brugada sign (p < 0.005). Thus the estimated 95% confidence limits for the prevalence of a definite Brugada sign among healthy controls was less than 0.5%. A questionable Brugada sign was seen in two patients with idiopathic ventricular fibrillation (5%) but also in five controls (1%) (p < 0.05). Normal ECGs were found following resuscitation and during long term follow up in 31 patients with idiopathic ventricular fibrillation (79%). Patients with idiopathic ventricular fibrillation and a normal ECG and those with the Brugada syndrome were of similar age and had similar spontaneous and inducible arrhythmias. However, the two groups differed in terms of sex, family history, and the incidence of sleep related ventricular fibrillation.

CONCLUSIONS

A definite Brugada sign is a specific marker of arrhythmic risk. However, less than obvious ECG abnormalities have little diagnostic value, as a "questionable" Brugada sign was observed in 1% of healthy controls. In this series of consecutive patients with idiopathic ventricular fibrillation, most had normal ECGs.

Sodium channel blockers identify risk for sudden death in patients with ST-segment elevation and right bundle branch block but structurally normal hearts

BACKGROUND

A mutation in the cardiac sodium channel gene (SCN5A) has been described in patients with the syndrome of right bundle branch block, ST-segment elevation in leads V1 to V3, and sudden death (Brugada syndrome). These electrocardiographic manifestations are transient in many patients with the syndrome. The present study examined arrhythmic risk in patients with overt and concealed forms of the disease and the effectiveness of sodium channel blockers to unmask the syndrome and, thus, identify patients at risk.

METHODS AND RESULTS

The effect of intravenous ajmaline (1 mg/kg), procainamide (10 mg/kg), or flecainide (2 mg/kg) on the ECG was studied in 34 patients with the syndrome and transient normalization of the ECG (group A), 11 members of 3 families in whom a SCN5A mutation was associated with the syndrome and 8 members in whom it was not (group B), and 53 control subjects (group C). Ajmaline, procainamide, or flecainide administration resulted in ST-segment elevation and right bundle branch block in all patients in group A and in all 11 patients with the mutation in group B. A similar pattern could not be elicited in the 8 patients in group B who lacked the mutation or in any person in group C. The follow-up period (37+/-33 months) revealed no differences in the incidence of arrhythmia between the 34 patients in whom the phenotypic manifestation of the syndrome was transient and the 24 patients in whom it was persistent (log-rank, 0.639).

CONCLUSIONS

The data demonstrated a similar incidence of potentially lethal arrhythmias in patients displaying transient versus persistent ST-segment elevation and right bundle branch block, as well as the effectiveness of sodium channel blockers to unmask the syndrome and, thus, identify patients at risk.

The Brugada syndrome: clinical, electrophysiologic and genetic aspects

This review deals with the clinical, basic and genetic aspects of a recently highlighted form of idiopathic ventricular fibrillation known as the Brugada syndrome. Our primary objective in this review is to identify the full scope of the syndrome and attempt to correlate the electrocardiographic manifestations of the Brugada syndrome with cellular and ionic heterogeneity known to exist within the heart under normal and pathophysiologic conditions so as to identify the cellular basis and thus potential diagnostic and therapeutic approaches. The available data suggest that the Brugada syndrome is a primary electrical disease resulting in abnormal electrophysiologic activity in right ventricular epicardium. Recent genetic data linking the Brugada syndrome to an ion channel gene mutation (SCN5A) provides further support for the hypothesis. The electrocardiographic manifestations of the Brugada syndrome show transient normalization in many patients, but can be unmasked using sodium channel blockers such as flecainide, ajmaline or procainamide, thus identifying patients at risk. The available data suggest that loss of the action potential dome in right ventricular epicardium but not endocardium underlies the ST segment elevation seen in the Brugada syndrome and that electrical heterogeneity within right ventricular epicardium leads to the development of closely coupled premature ventricular contractions via a phase 2 reentrant mechanism that then precipitates ventricular tachycardia/ventricular fibrillation (VT/VF). Currently, implantable cardiac defibrillator implantation is the only proven effective therapy in preventing sudden death in patients with the Brugada syndrome and is indicated in symptomatic patients and should be considered in asymptomatic patients in whom VT/VF is inducible at time of electrophysiologic study.

Polymorphic ventricular tachyarrhythmias in the absence of organic heart disease: classification, differential diagnosis, and implications for therapy

Different polymorphic ventricular tachyarrhythmias may cause syncope or cardiac arrest in patients with no heart disease: (1) Catecholamine-sensitive polymorphic ventricular tachycardia (VT) presents during childhood: the hallmark is the reproducible provocation of atrial and polymorphic ventricular arrhythmias during exercise, despite a normal QT. Beta-blockers are the treatment of choice. (2) In the long QT syndromes (LQTS), malfunction of ion channels leads to prolonged ventricular repolarization, early afterdepolarizations, and triggered ventricular arrhythmias. Therapeutic options include: beta-blockers, genotype-specific therapy, cardiac sympathetic denervation, and implantation of pacemakers or defibrillators. (3) The "short-coupled variant of torsade de pointes" is a malignant disease that shares several characteristics with idiopathic ventricular fibrillation. Although verapamil is frequently recommended, mortality rates remain high. (4) Idiopathic ventricular fibrillation (VF) with normal electrocardiogram (ECG) strikes young adults of both genders. In contrast to other polymorphic tachyarrhythmias, idiopathic VF is not generally related to stress. Also, familial involvement is rare. Therapeutic options include implantation of defibrillators and therapy with class 1A drugs. (5) The "Brugada syndrome" and the "syndrome of nocturnal sudden death" strike males almost exclusively. Right bundle branch block (RBBB) with ST elevation in the right precordial leads-the "Brugada sign"--is seen in the ECG of both patient populations. Implantation of defibrillators is recommended.

Mode of onset of malignant ventricular arrhythmias in idiopathic ventricular fibrillation

INTRODUCTION

The mode of onset of malignant ventricular arrhythmias (ventricular tachycardia [VT] or ventricular fibrillation [VF]) has been well described in patients with organic heart disease and in patients with the long QT syndromes. Less is known about the mode of onset of VF in patients with out-of-hospital VF who have no evidence of organic heart disease or identifiable etiology.

METHODS AND RESULTS

We reviewed the ECGs of all our patients with idiopathic VF. Documentation of the onset of spontaneous arrhythmias was available for 22 VF episodes in 9 patients (6 men and 3 women; age 41 +/- 16 years). In all instances, spontaneous VF followed a rapid polymorphic VT, which was initiated by premature ventricular complexes (PVCs) with very short coupling intervals. The PVC initiating VF had a coupling interval of 302 +/- 52 msec and a prematurity index of 0.4 +/- 0.07. These PVCs occurred within 40 msec of the peak of the preceding T wave. Pause-dependent arrhythmias were never observed.

CONCLUSION

Cardiac arrest among patients with idiopathic VF has a very distinctive mode of onset. Documentation of a polymorphic VT that is not pause dependent is of diagnostic value.

Sustained monomorphic ventricular tachycardia in a patient with Brugada syndrome

We report a patient with Brugada syndrome who developed sustained monomorphic ventricular tachycardia (SMVT). The patient was a 29-year-old man who experienced recurrent episodes of palpitation and syncope after drinking alcohol. Electrocardiogram showed right bundle branch block and ST-segment elevation in precordial leads V1-3 without Q-Tc prolongation. Organic heart disease and coronary artery disease were excluded by noninvasive and invasive tests. Ventricular fibrillation was induced by the application of a single extra-stimulus to the right ventricular outflow tract. During isoproterenol infusion, SMVT of left bundle branch block morphology (240/min) was induced by the application of a single extrastimulus to the right ventricular apex. SMVT also developed spontaneously. Pace mapping disclosed that SMVT originated at the free wall of the right ventricular outflow tract. Head-up tilt test and an alcohol provocation test both induced similar SMVT that was associated with hypotension and near syncope. SMVT was not terminated by intravenous administration of lidocaine, procainamide or adenosine triphosphate (10 mg), but was terminated by propranolol. Thus, a beta-adrenoceptor-mediated mechanism appears to play an important role in SMVT in this patient. The site of origin of SMVT might be closely related to the lesion that causes ST-segment elevation.