A Marker for Sudden Death in Patients Without Demonstrable Structural Heart Dise
A Marker for Sudden Death in Patients Without Demonstrable Structural Heart Disease
ABSTRACT & COMMENTARY
Synopsis: Additional data justify the designation of right bundle branch block with ST segment elevation as a separate syndrome.
Source: Brugada J, et al. Circulation 1998;97:457-460.
In this paper, brugada and associates provide further information about a syndrome they first described six years ago.1 In that earlier paper, eight cases of aborted sudden death in patients without structural heart disease who had a characteristic ECG pattern of a right bundle branch block QRS morphology and ST segment elevation in leads V1 through V3 were described. This paper extends information about this syndrome, including a total of 63 patients identified in 33 centers around the world. In 36 patients, a familial pattern of sudden death had been identified. Forty-one patients were identified after a clinical episode of aborted cardiac arrest or syncope. The remaining 22 patients were identified either during routine ECG screening or after an episode of sudden death in a family member. Six of the 22 patients, who were asymptomatic when they were originally identified, later developed symptoms.
Electrophysiologic studies were performed in 46 of the 63 patients. In 80%, either ventricular fibrillation or long runs of nonsustained polymorphic ventricular tachycardia were reproducibly initiated.
Therapy during follow-up was decided by the local investigators. Thirty-five patients received an implantable defibrillator. Five patients were treated with amiodarone. Twelve patients received beta blockers. Thirteen patients were not treated. Eleven of the 35 patients who received an implantable defibrillator had an episode of rapid ventricular tachycardia that was appropriately treated by the defibrillator. Four of 17 patients treated with either beta blockers or amiodarone and four of 13 patients in the no therapy group died during follow-up. All mortality was due to sudden death. The mean follow-up for the entire group was 37 ± 31 months.
Brugada et al conclude that these additional data justify the designation of right bundle branch block with ST segment elevation as a separate syndrome. Patients with this finding are at high risk for arrhythmic events. Implantable cardioverter defibrillator therapy is the treatment of choice.
COMMENT BY JOHN P. DiMARCO, MD, PhD
This paper provides further information about what has been called the Brugada syndrome. The molecular basis for this syndrome is unknown. Since it frequently occurs in a familial pattern, it is likely that one or more specific genetic mutations are responsible for the repolarization abnormalities described, but, as yet, the defects have not been characterized.
The prevalence of this syndrome is undetermined. Almost all of the centers that provided patients for this study were located in western Europe. Two centers from the United States are listed as contributors. I have yet to encounter a patient with this syndrome in my personal practice. Whether similar findings will be identified in other groups of patients at risk for sudden death are unknown. In particular, it has been speculated that there is a relationship between the Brugada syndrome and the sudden unexpected death syndrome that has been reported to occur in southeast Asia, but the publication of any data to confirm this is still pending.
It is not unexpected that ICD therapy is the treatment of choice in this syndrome. These patients have no identifiable structural heart disease and are only subject to relatively infrequent, paroxysmal attacks of arrhythmia. Therefore, the ICD should provide nearly ideal therapy since the episodes tend to occur at relatively infrequent intervals.
Patients with the Brugada syndrome differ from those with the long QT syndrome in their electrophysiologic properties. Patients with the latter syndrome are usually not inducible into any arrhythmia at electrophysiologic study. Although some authors have argued that induction of ventricular fibrillation or polymorphic ventricular tachycardia should be considered a nonspecific finding at electrophysiologic study, this statement only applies to patients who present with monomorphic ventricular tachycardia. In the patients described here, polymorphic ventricular tachycardia is the clinical arrhythmia, and, therefore, induction of a polymorphic arrhythmia is a positive (though nonspecific) finding.
Only a single sample electrocardiogram is provided in this report. It would be important to know if there is any variability in the electrocardiographic findings. In some patients, minor degrees of ST segment elevation in a right bundle type pattern can be seen on the electrocardiogram. Until more is known about the variability of ECG findings in this syndrome, only classic features should justify this diagnosis.
Reference
1. Brugada P, Brugada J. J Am Coll Cardiol 1992;20: 1391-1396.
Subscribe Now for Access
You have reached your article limit for the month. We hope you found our articles both enjoyable and insightful. For information on new subscriptions, product trials, alternative billing arrangements or group and site discounts please call 800-688-2421. We look forward to having you as a long-term member of the Relias Media community.