(See also Overview of Arrhythmias.)
Several different mutations are involved, most affecting the SCN5A gene that encodes the alpha-subunit of the voltage-dependent cardiac sodium 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 certain drugs including sodium channel blockers, beta-blockers, tricyclic antidepressants, lithium, and cocaine.
Diagnosis
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 debate.
Initial diagnosis of Brugada syndrome is based on a characteristic ECG pattern, the type 1 Brugada ECG pattern (see figure Type 1 Brugada ECG pattern). The type 1 Brugada ECG pattern has prominent ST elevation in V1 and V2 (sometimes involving V3) 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.
Treatment
Patients presenting with syncope and patients resuscitated from arrest should receive an implantable cardioverter-defibrillator.
Best treatment of Brugada syndrome in patients diagnosed based on ECG changes and family history is unclear, although they do have increased risk of sudden death.
