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Brugada syndrome
Brugada syndrome, also known as Sudden Unexpected Death Syndrome
(SUDS), is the most common cause of sudden death in young men without
known underlying cardiac disease. It is due to a dysfunction of the
myocardial voltage-gated sodium channels which renders patients
vulnerable to ventricular tachycardia and/or fibrillation that often
results in sudden cardiac death.
Causes
Dysfunction in cardiac ion channels underlies the clinical
manifestations of Brugada syndrome (i.e. cardiac channelopathy). About
20% have mutations in the gene SCN5A, which encodes the cardiac
voltage-gated sodium channel Nav1.5. This leads to a loss of the action
potential dome of some epicardial areas of the right ventricle. Which
results in transmural and epicardial dispersion of repolarization. The
transmural dispersion underlies ST-segment elevation and the development
of a vulnerable window across the ventricular wall, whereas the
epicardial dispersion of repolarization facilitates the development of
phase 2 reentry, which generates a phase 2 reentrant extrasystole that
captures the vulnerable window to precipitate ventricular tachycardia
and/or fibrillation that often results in sudden cardiac death.
This condition is inherited in an autosomal dominant pattern in 50%
of familial cases and is more common in males. In addition it has a
higher prevalence in most Asian populations (e.g. Laos and Thailand).
Symptoms and signs
Patients with Brugada syndrome are prone to develop ventricular
tachyarrhythmias, which may lead to syncope, cardiac arrest, or sudden
cardiac death.
Diagnosis
In some cases, the disease can be detected by observing
characteristic patterns on an electrocardiograph, which may be present
all the time, or might be elicited by strenuous exercise, or by the
administration of particular drugs (infusion of flecainide, procainamide
or a beta-blocker). In these cases, the disorder is characterized by a
complete or incomplete right bundle-branch block and T-wave inversion
with a characteristic coved or saddle-shaped ST-segment elevation in
leads V1 through V3 on ECG.
Treatment
1. Implantable cardiac defibrillator (ICD)
At present, implantation of an implantable cardiac defibrillator (ICD)
is the only treatment that has been proven effective for Brugada
syndrome. This is indicated for patients who have a history of cardiac
arrest and those with a high risk of sudden death.
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