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 (ECG) findings and an increased risk of sudden cardiac death in young adults, and occasionally in children and infants.
Historical Perspective
The Brugada brothers were the first to describe the characteristic ECG findings and link them to sudden death.
Before that the characteristic ECG findings were often mistaken for a right ventricular myocardial infarction. In 1953 a publication by Oscher mentioned that despite being mistaken for right ventricular myocardial infarction, the ECG findings were not associated with myocardial ischemia.[1]
Although the ECG findings of Brugada syndrome were first reported[2] among survivors of cardiac arrest in 1989, it was only in 1992 that the Brugada brothers[3] recognized it as a distinct clinical entity, causing sudden death by causing ventricular fibrillation.
Pathophysiology
Approximately 20% of the cases of Brugada syndrome have been shown to be associated with mutation(s) in the gene that encodes for the sodium ion channel in the cell membranes of the muscle cells of the heart (the myocytes). The gene, named SCN5A, is located on the short arm of the third chromosome (3p21). Loss-of-function mutations in this gene lead to a loss of the action potential dome of some epicardial areas of the right ventricle. This results in transmural and epicardial dispersion of repolarization. Over 160 mutations in the SCN5A gene have been discovered to date, each having varying mechanisms and effects on function, thereby explaining the varying degrees of penetration and expression of this disorder. [4]
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. [5] 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. [5] It is 8-10 times more common in men.
Risk Factors: Agents and Scenarios that Provoke the Brugada Syndrome Pattern
The electrocardiographic findings of Brugada syndrome are often concealed, but can be unmasked or modulated by a number of drugs and pathophysiological states including (in alphabetical order)[5]:
- A combination of glucose and insulin
- Ajmaline (a diagnostic test agent)
- α-adrenergic agonists
- β-adrenergic blockers
- Cocaine
- Fever. It is for this reason that antipyretic agents are recommended to aggressively treat a fever in the patient with Brugada syndrome.
- Flecainide (a diagnostic test agent)
- Hypercalcemia
- Hyperkalemia
- Hypokalemia
- In large studies, a family history of sudden cardiac death among patients with Brugada syndrome does not appear to be a risk factor for sudden cardiac death in siblings.
- Procainamide (a diagnostic test agent)
- Propranolol intoxication
- Sodium channel blockers (a diagnostic test agent)
- Tetracyclic antidepressants
- Tricyclic antidepressants
- Vagotonic agents that mimic sleep
EKG Characteristics
As shown by the racing below, The EKG characteristics of Bugada syndrome include:
- a) A broad P-wave with some PQ prolongation
- b) J point elevation in the right precordial leads (V1-V3)
- c) Coved ST segment elevation
- d) An inverted T wave
References
- ↑ OSHER HL, WOLFF L (1953). "Electrocardiographic pattern simulating acute myocardial injury". The American Journal of the Medical Sciences. 226 (5): 541–5. PMID 13104407. Unknown parameter
|month=ignored (help);|access-date=requires|url=(help) - ↑ Martini B, Nava A, Thiene G, Buja GF, Canciani B, Scognamiglio R, Daliento L, Dalla Volta S. Ventricular fibrillation without apparent heart disease: description of six cases. Am Heart J 1989 Dec;118(6):1203-9 PMID 2589161
- ↑ Brugada P, Brugada J. Right bundle branch block, persistent ST segment elevation and sudden cardiac death: a distinct clinical and electrocardiographic syndrome. A multicenter report. J Am Coll Cardiol. 1992 Nov 15;20(6):1391-6. PMID 1309182
- ↑ Napolitano C, Priori SG (2006). "Brugada syndrome". Orphanet journal of rare diseases. 1: 35. doi:10.1186/1750-1172-1-35. PMID 16972995.
- ↑ 5.0 5.1 5.2 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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