(See also Overview of Arrhythmias Overview of Arrhythmias The normal heart beats in a regular, coordinated way because electrical impulses generated and spread by myocytes with unique electrical properties trigger a sequence of organized myocardial... read more .)
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 Congenital long QT syndrome Torsades de pointes is a specific form of polymorphic ventricular tachycardia in patients with a long QT interval. It is characterized by rapid, irregular QRS complexes, which appear to be twisting... read more 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 Ventricular Tachycardia (VT) Ventricular tachycardia is ≥ 3 consecutive ventricular beats at a rate ≥ 120 beats/minute. Symptoms depend on duration and vary from none to palpitations to hemodynamic collapse and death. Diagnosis... read more and ventricular fibrillation Ventricular Fibrillation (VF) Ventricular fibrillation causes uncoordinated quivering of the ventricle with no useful contractions. It causes immediate syncope and death within minutes. Treatment is with cardiopulmonary... read more . 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 of Brugada Syndrome
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.
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 Type 1 Brugada ECG pattern Brugada syndrome is an inherited disorder of cardiac electrophysiology causing an increased risk of syncope and sudden death. (See also Overview of Arrhythmias.) Several different mutations... read more ). 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 Bundle Branch Block and Fascicular Block Bundle branch block is partial or complete interruption of impulse conduction in a bundle branch; fascicular block is similar interruption in a hemifascicle of the bundle. The 2 disorders often... read more . 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.
Type 1 Brugada ECG pattern
Prominent J-point elevation to a coved ST segment, leading to an inverted T-wave in leads V1 and V2.
Treatment of Brugada Syndrome
Patients presenting with syncope and patients resuscitated from arrest should receive an implantable cardioverter-defibrillator Implantable Cardioverter-Defibrillators (ICD) The need for treatment of arrhythmias depends on the symptoms and the seriousness of the arrhythmia. Treatment is directed at causes. If necessary, direct antiarrhythmic therapy, including antiarrhythmic... read more .
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.