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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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