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Brugada Syndrome

by L. Brent Mitchell, MD

Brugada syndrome is an inherited disorder of cardiac electrophysiology causing an increased risk of syncope and sudden death.

Several different mutations are involved, most affecting the SCN5A gene that encodes the α-subunit of the voltage-dependent cardiac Na channel. Typically, patients have no structural heart disease. Nevertheless, relationships with other genetic and acquired structural heart diseases are increasingly being recognized, as are overlap syndromes with long QT syndrome type 3 and with arrhythmogenic right ventricular dysplasia (ARVD).

In some patients, Brugada syndrome has no clinical expression. However, in many patients it leads to syncope or sudden cardiac death due to polymorphic ventricular tachycardia and ventricular fibrillation. Events occur more often at night and are not usually related to exercise. Events may also be brought on by fever and by treatment with certain drugs including Na channel blockers, β-blockers, tricyclic antidepressants, lithium, and cocaine.

Initial diagnosis is based on a characteristic ECG pattern (type 1 Brugada ECG pattern—see Figure: Type 1 Brugada syndrome.) with prominent ST elevation in V 1 and V 2 (sometimes involving V 3 ) that causes the QRS complex in these leads to resemble right bundle branch block. The ST segment is coved and descends to an inverted T-wave. Lesser degrees of these patterns (type 2 and type 3 Brugada ECG patterns) are not considered diagnostic. The type 2 and type 3 patterns may change to a type 1 pattern spontaneously, with fever, or in response to drugs. The latter is the basis of a challenge diagnostic test usually using ajmaline or procainamide. Diagnosis should be considered in patients with unexplained cardiac arrest or syncope or a family history of such. Role of electrophysiologic testing is currently unclear and is the subject of ongoing study.

Patients presenting with syncope and patients resuscitated from arrest should receive an implantable cardioverter-defibrillator. Best treatment of patients diagnosed based on ECG changes and family history is unclear, although they do have increased risk of sudden death.

Type 1 Brugada syndrome.

Prominent J-point elevation to a coved ST segment, leading to an inverted T-wave in leads V 1 and V 2 .

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