Brugada syndrome overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
The Brugada syndrome is a genetic disease that is characterized by abnormal electrocardiogram (EKG) findings and an increased risk of sudden cardiac death in young adults, and occasionally in children and infants.
Epidemiology and Demographics
Insofar as Brugada syndrome is a relatively newly recognized syndrome, its incidence and prevalence continues to increase. Brugada syndrome is quite common in Southeast Asia where it is endemic, and affects 50 out of every 10,000 individuals. It is the second leading cause of death after car accidents among young people in these countries. It has been estimated that Brugada syndrome accounts for 4% of all sudden cardiac deaths and 20% of sudden cardiac deaths among patients with structurally normal hearts. It is 8-10 times more common in men.
Risk Factors
The EKG changes of Brugada syndrome can vary over time, depending on the autonomic balance and the administration of antiarrhythmic drugs. Adrenergic stimulation decreases the ST segment elevation, while vagal stimulation worsens it. During sleep, there is heightened vagal tone, and the pattern may be exacerbated at that time (as is the risk of sudden cardiac death at that time). The administration of class Ia, Ic and III drugs increases the ST segment elevation, as does fever. The impact of exercise depends upon when the EKG is obtained: during exercise the ST segment elevation may decrease but may increase later after exercise when the body temperature has risen. Similar to early repolarization variant, when the heart rate decreases, the ST segment elevation increases and when the heart rate increases the ST segment elevation decreases. While Brugada syndrome is often associated with polymorphic VT which may be self terminating, in the presence of autonomic imbalance, hypokalemia, fever or exacerbating drugs sustained ventricular fibrillation and sudden cardiac death may result.[1]
Screening
Relatives of patients with Brugada syndrome can be screened for the syndrome by obtaining an EKG, although the diagnostic pattern may be concealed. Genetic testing can also be used to support the diagnosis of Brugada syndrome and to detect relatives at risk.[1] Unfurtunately, despite the association of the Brugada syndrome with the SCN5A genotype, there is unfortunately no association between the results of genetic testing and clinical prognosis.
Natural History, Complications and Prognosis
The Brugada patient may develop atrial arrhythmias and abnormalities in atrial conduction, and these abnormalities are associated with inducibility of ventricular fibrillation.
Diagnosis
Diagnostic Criteria
The diagnosis of brugada syndrome is based upon electrocardiographic and clinical criteria.
History and Symptoms
Patients with Brugada syndrome will sometimes have a family history of sudden cardiac death, and symptoms of syncope, seizures, or agonal breathing. These symptoms most often come on either at rest or during sleep.
Physical Examination
Insofar as Brugada syndrome is not associated with any structural heart disease, there are generally no abnormalities on physical examination. Vagal maneuvers such as carotid sinus massage may increase vagal tone and may unmask the presence of a Type I Brugada pattern. In a patient who has experienced recent symptoms such as syncope, it is important to check the temperature in so far as fever may trigger a self terminating or sustained episode of ventricular tachycardia / ventricular fibrillation. The presence of fever is also a target of antipyretic therapy.
Laboratory Findings
Hypokalemia and hyperkalemia can both trigger either sustained or nonsustained episodes of ventricular tachycardia / ventricular fibrillation and serum electrolytes should therefore be checked. Both alcohol and cocaine intoxication can be associated with either sustained or nonsustained episodes of ventricular tachycardia/ventricular fibrillation and a toxicology screen should be ordered if there is a clinical suspicion. Likewise, tricyclic antidepressants can be associated with exacerbations of the syndrome, and levels of these agents should also be checked if there is a clinical suspicion.
Electrocardiogram
There are three electrocardiographic patterns associated with Brugada syndrome: Type I, Type II and Type III. The diagnosis of Brugada syndrome is based upon the presence of Type I EKG changes. Patients with Type II or Type III Brugada patterns can convert to a Type I Brugada pattern following the administration of sodium channel blockers such as ajmaline and flecainide. Type 1 Brugada syndrome may always be present on the EKG, or it may be elicited by the administration of particular drugs (e.g., Class IC antiarrythmic drugs that blocks sodium channels such as ajmaline, flecainide) or it may be unmasked by various triggers or risk factors.
Chest X Ray
Insofar as Brugada syndrome is not associated with structural abnormalities of the heart, there are no associated abnormalities on the chest x-ray.
References
- ↑ 1.0 1.1 Antzelevitch C, Brugada P, Borggrefe M, Brugada J, Brugada R, Corrado D, Gussak I, LeMarec H, Nademanee K, Perez Riera AR, Shimizu W, Schulze-Bahr E, Tan H, Wilde A (2005). "Brugada syndrome: report of the second consensus conference". Heart Rhythm : the Official Journal of the Heart Rhythm Society. 2 (4): 429–40. PMID 15898165. Unknown parameter
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