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==Overview==
==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.
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. Brugada syndrome is a condition that causes a disruption of the heart's normal rhythm. Specifically, this disorder can lead to uncoordinated electrical activity in the heart's lower chambers ([[ventricles]]), an abnormality called [[ventricular arrhythmia]]. If untreated, the irregular heartbeats can cause [[fainting]] ([[syncope]]), [[seizures]], [[difficulty breathing]], or [[sudden death]]. These complications typically occur when an affected person is resting or asleep.
 
==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.<ref name="pmid13104407">{{cite journal |author=OSHER HL, WOLFF L |title=Electrocardiographic pattern simulating acute myocardial injury |journal=[[The American Journal of the Medical Sciences]] |volume=226 |issue=5 |pages=541–5 |year=1953 |month=November |pmid=13104407 |doi= |url= |issn= |accessdate=2012-10-13}}</ref>
 
Although the ECG findings of Brugada syndrome were first reported<ref>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</ref> among survivors of cardiac arrest in 1989, it was only in 1992  that the Brugada brothers<ref>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</ref> recognized it as a distinct clinical entity, causing sudden [[death]] by causing [[ventricular fibrillation]].


==Historical Perspective==
Brugada syndorme  was potentially first seen on [[EKG]] in survivors of cardiac arrest in 1989, but it was not until 1992 that the Brugada brothers recognized it as a distinct clinical entity which could cause [[sudden death]] by [[ventricular fibrillation]].
==Classification==
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]].
==Pathophysiology==
==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 (biology)|cell]] [[cell membrane|membrane]]s of the muscle cells of the heart (the [[myocyte]]s). 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. <ref name="pmid16972995">{{cite journal |author=Napolitano C, Priori SG |title=Brugada syndrome |journal=Orphanet journal of rare diseases |volume=1 |issue= |pages=35 |year=2006 |pmid=16972995 |doi=10.1186/1750-1172-1-35}}</ref>
Approximately 20% of persons with Brugada syndome have a mutation in the gene [[SCN5A]]. This gene encodes for the sodium ion channel. The mutation is inherited in an [[autosomal dominant]] pattern, and is more commonly seen in males. Brugada syndrome has also been shown to result from defects in a calcium channel.
==Differentiating Brugada syndrome from other Diseases==
Brugada syndrome should be differentiated from other cardiac disorders, electrolyte disturbances, and drug intoxication syndromes. The condition which most similarly presents to Brugada syndrome is [[arrhythmogenic right ventricular dysplasia]], as they both cause [[sudden cardiac death]] in children. Brugada syndrome can be differentiated from [[arrhythmogenic right ventricular dysplasia]] by the genetic counterpart of [[SCN5A]], the lack of structural abnormalities within the heart, the association with [[polymorphic ventricular tachycardia]] during sleep, and [[EKG]] changes that are enhanced by vagotonic agents.


==Differentiating Brugada Syndrome from other Diseases==
==Epidemiology and Demographics==
Abnormalities that can lead to ST-segment elevation in the right precordial leads include the following:<ref name="pmid14687250">{{cite journal |author=Takehara N, Makita N, Kawabe J, Sato N, Kawamura Y, Kitabatake A, Kikuchi K |title=A cardiac sodium channel mutation identified in Brugada syndrome associated with atrial standstill |journal=[[Journal of Internal Medicine]] |volume=255 |issue=1 |pages=137–42 |year=2004 |month=January |pmid=14687250 |doi= |url=http://onlinelibrary.wiley.com/resolve/openurl?genre=article&sid=nlm:pubmed&issn=0954-6820&date=2004&volume=255&issue=1&spage=137 |issn= |accessdate=2012-10-13}}</ref>
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 500 out of every 100,000 individualsIt 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 death]]s among patients with structurally normal hearts.  It is 8-10 times more common in men.
 
* [[myocardial ischemia|Acute myocardial ischemia]] or [[Acute myocardial infarction|infarction]]
* [[Acute myocarditis]]
* [[Acute pericarditis]]
* [[Acute pulmonary thromboemboli]]
* [[Arrhythmogenic right ventricular dysplasia]] / [[Arrhythmogenic right ventricular dysplasia|cardiomyopathy]] ([[Arrhythmogenic right ventricular dysplasia|ARVD/C]])<ref>Corrado  D, Nava  A,  Buja  G,  Martini  B, Fasoli  G,  Oselladore  L,  Turrini  P,  Thiene  GFamilial cardiomyopathy  underlies syndrome of right bundle branch block, ST segment elevation and sudden death. J Am Coll Cardiol.  1996;  27:  443–448.</ref><ref> Corrado  D,  Basso  C,  Buja  G,  Nava  A,  Rossi  L,  Thiene  G.  Right bundle branch block, right precordial ST-segment elevation, and sudden death in young people. Circulation.  2001; 103:  710–717.</ref>
 
* [[Cardioversion]]. Brugada-like ECG changes can be observed briefly after direct-current cardioversion.  It is currently unclear if this is a sign that the patient is a gene carrier for Brugada syndrome.<ref name="pmid10758932">{{cite journal |author=Kok LC, Mitchell MA, Haines DE, Mounsey JP, DiMarco JP |title=Transient ST elevation after transthoracic cardioversion in patients with hemodynamically unstable ventricular tachyarrhythmia |journal=[[The American Journal of Cardiology]] |volume=85 |issue=7 |pages=878–81, A9 |year=2000 |month=April |pmid=10758932 |doi= |url=http://linkinghub.elsevier.com/retrieve/pii/S0002914999008863 |issn= |accessdate=2012-10-14}}</ref><ref name="pmid12929296">{{cite journal |author=Gurevitz O, Glikson M |title=Cardiac resynchronization therapy: a new frontier in the management of heart failure |journal=[[The Israel Medical Association Journal : IMAJ]] |volume=5 |issue=8 |pages=571–5 |year=2003 |month=August |pmid=12929296 |doi= |url= |issn= |accessdate=2012-10-14}}</ref><ref name="pmid12418739">{{cite journal |author=Gurevitz O, Lipchenca I, Yaacoby E, Segal E, Perel A, Eldar M, Glikson M |title=ST-segment deviation following implantable cardioverter defibrillator shocks: incidence, timing, and clinical significance |journal=[[Pacing and Clinical Electrophysiology : PACE]] |volume=25 |issue=10 |pages=1429–32 |year=2002 |month=October |pmid=12418739 |doi= |url= |issn= |accessdate=2012-10-14}}</ref>
* [[Cocaine intoxication]]
* [[Coronary spasm]]
* [[Dissecting aortic aneurysm]]<ref>
Myers  GB.  Other QRS-T patterns that may be mistaken for myocardial infarction; IV. Alterations in blood potassium; myocardial ischemia; subepicardial myocarditis; distortion associated with arrhythmias. Circulation.  1950;  2:  75–93.</ref>


* [[Duchenne muscular dystrophy]]<ref>''Perloff JK, Henze E, Schelbert HR. Alterations in regional myocardial metabolism, perfusion, and wall motion in Duchenne muscular dystrophy studied by radionuclide imaging. Circulation''. '' 1984; 69: 33–42.''</ref>
==Risk Factors==
* [[Early repolarization]]
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 itDuring 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.<ref name="pmid15898165">{{cite journal |author=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 |title=Brugada syndrome: report of the second consensus conference |journal=[[Heart Rhythm : the Official Journal of the Heart Rhythm Society]] |volume=2 |issue=4 |pages=429–40 |year=2005 |month=April |pmid=15898165 |doi= |url= |issn= |accessdate=2012-10-14}}</ref>
* [[Friedreich ataxia]]
* [[Heterocyclic antidepressant overdose]]
* [[Hypercalcemia]]<ref name="pmid6475795">{{cite journal |author=Douglas PS, Carmichael KA, Palevsky PM |title=Extreme hypercalcemia and electrocardiographic changes |journal=[[The American Journal of Cardiology]] |volume=54 |issue=6 |pages=674–5 |year=1984 |month=September |pmid=6475795 |doi= |url= |issn= |accessdate=2012-10-13}}</ref><ref name="pmid6475794">{{cite journal |author=Sridharan MR, Horan LG |title=Electrocardiographic J wave of hypercalcemia |journal=[[The American Journal of Cardiology]] |volume=54 |issue=6 |pages=672–3 |year=1984 |month=September |pmid=6475794 |doi= |url= |issn= |accessdate=2012-10-13}}</ref>
* [[Hyperkalemia]]<ref>Myers  GBOther QRS-T patterns that may be mistaken for myocardial infarction; IV. Alterations in blood potassium; myocardial ischemia; subepicardial myocarditis; distortion associated with arrhythmias. Circulation. 1950;  2:  75–93.</ref><ref>Merrill  JP,  Levine  HD, Somerville  W,  Smith  S.  Clinical recognition and treatment of acute potassium intoxication.        Ann Intern Med.  1950;  33:  797–830.</ref><ref name="pmid12413761">{{cite journal |author=Ortega-Carnicer J, Benezet J, Ruiz-Lorenzo F, Alcázar R |title=Transient Brugada-type electrocardiographic abnormalities in renal failure reversed by dialysis |journal=[[Resuscitation]] |volume=55 |issue=2 |pages=215–9 |year=2002 |month=November |pmid=12413761 |doi= |url=http://linkinghub.elsevier.com/retrieve/pii/S0300957202002101 |issn= |accessdate=2012-10-13}}</ref>
* [[Hypothermia]], can cause an [[Osborn wave]] on the ECG which can sometimes resemble Brugada syndrome<ref> <div>'' Osborn JJ. Experimental hypothermia; respiratory and blood pH changes in relation to cardiac function. Am J Physiol''. '' 1953; 175: 389–398.''</div> </ref><ref name="pmid12693512">{{cite journal |author=Noda T, Shimizu W, Tanaka K, Chayama K |title=Prominent J wave and ST segment elevation: serial electrocardiographic changes in accidental hypothermia |journal=[[Journal of Cardiovascular Electrophysiology]] |volume=14 |issue=2 |pages=223 |year=2003 |month=February |pmid=12693512 |doi= |url=http://onlinelibrary.wiley.com/resolve/openurl?genre=article&sid=nlm:pubmed&issn=1045-3873&date=2003&volume=14&issue=2&spage=223 |issn= |accessdate=2012-10-13}}</ref>
* [[Left ventricular hypertrophy]]
* [[Pectus excavatum]]<ref> <div>'' Kataoka H. Electrocardiographic patterns of the Brugada syndrome in right ventricular infarction/ischemia. Am J Cardiol''. '' 2000; 86: 1056.''</div></ref>
* [[Prinzmetal's angina]]<ref name="pmid14645641">{{cite journal |author=Wang K, Asinger RW, Marriott HJ |title=ST-segment elevation in conditions other than acute myocardial infarction |journal=[[The New England Journal of Medicine]] |volume=349 |issue=22 |pages=2128–35 |year=2003 |month=November |pmid=14645641 |doi=10.1056/NEJMra022580 |url=http://www.nejm.org/doi/abs/10.1056/NEJMra022580?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub%3dpubmed |issn= |accessdate=2012-10-13}}</ref>
* [[Right ventricular outflow tract obstruction|Mediastinal tumor compressing the right ventricular outflow tract]] ([[RVOT]])
* [[RBBB|Right]] or [[left bundle-branch block]] (atypical)
* [[Right ventricular infarction]]
* [[Right ventricular ischemia]]
* [[Right ventricular outflow tract]] compression due to a [[mediastinal tumor]]<ref name="pmid10461308">{{cite journal |author=Tarín N, Farré J, Rubio JM, Tuñón J, Castro-Dorticós J |title=Brugada-like electrocardiographic pattern in a patient with a mediastinal tumor |journal=[[Pacing and Clinical Electrophysiology : PACE]] |volume=22 |issue=8 |pages=1264–6 |year=1999 |month=August |pmid=10461308 |doi= |url= |issn= |accessdate=2012-10-13}}</ref>or [[hemopericardium]]<ref>''Tomcsanyi J, Simor T, Papp L. Images in cardiology. Haemopericardium and Brugada-like ECG pattern in rheumatoid arthritis. Heart''. '' 2002; 87: 234.''</ref>
* [[Thiamine deficiency]]<ref name="pmid7197132">{{cite journal |author=Read DH, Harrington DD |title=Experimentally induced thiamine deficiency in beagle dogs: clinical observations |journal=[[American Journal of Veterinary Research]] |volume=42 |issue=6 |pages=984–91 |year=1981 |month=June |pmid=7197132 |doi= |url= |issn= |accessdate=2012-10-13}}</ref>
* Various central and autonomic nervous system abnormalities
* [[Other conditions that can lead to ST-segment elevation in the right precordial leads]]
* [[Early repolarization syndrome]]
* Other normal variants (particularly in males)


==Differentiating Brugada Syndrome from Arrhythmogenic Right Ventricular Dysplasia==
==Screening==
Although both Brugada syndrome and [[Arrhythmogenic Right Ventricular Dysplasia]] are associated with [[sudden cardiac death]] in young patients, the two syndromes are fairly easy to distinguish electrocardiographically and clinically.
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.<ref name="pmid15898165">{{cite journal |author=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 |title=Brugada syndrome: report of the second consensus conference |journal=[[Heart Rhythm : the Official Journal of the Heart Rhythm Society]] |volume=2 |issue=4 |pages=429–40 |year=2005 |month=April |pmid=15898165 |doi= |url= |issn= |accessdate=2012-10-14}}</ref> Unfortunately, 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.
===Genetics===
There is only one gene associated with Brugada syndrome, namely the SCN5A gene, and there is no overlap of the genetic abnormalities associated with [[Arrhythmogenic Right Ventricular Dysplasia]].


=== Structural Abnormalities of the right Ventricle===
==Natural History, Complications and Prognosis==
While Brugada syndrome is not associated with structural abnormalities in the right ventricle, [[arrhythmogenic right ventricular dysplasia]] is associated with fibrofatty infiltration.
Brugada syndrome usually becomes apparent in adulthood, although it may present in infants and children as [[sudden cardiac death]].  The mean age of sudden death in patients with Brugada syndrome is 40 years old. The Brugada patient may develop atrial arrhythmias and abnormalities in atrial conduction, and these abnormalities are associated with inducibility of [[ventricular fibrillation]]. Implantation of a cardiac defibrillator [[AICD]] can improve prognosis for some.


=== Precipitant of Ventricular Arrhythmias===
==Diagnosis==
[[Arrhythmogenic right ventricular dysplasia]] is associated with [[monomorphic ventricular tachycardia]] with a left bundle branch morphology and is precipitated by catecholamines or exercise. In contrast, Brugada syndrome is associated with [[polymorphic ventricular tachycardia]] and occurs predominantly during sleep or rest.
===Diagnostic Criteria===
The diagnosis of brugada syndrome is based upon electrocardiographic and clinical criteria. Only the Type I Brugada pattern qualifies as part of the diagnostic criteria for Brugada syndrome. Other rhythm abnormalities and family history are also taken into account when making the diagnosis of Brugada syndrome.


=== Response to Pharmacologic Agents===
===History and Symptoms===
The EKG abnormalities of Brugada syndrome are enhanced by [[vagotonic]] agents, beta-adrenergic blockers, and sodium channel blockers whereas the EKG changes of [[arrhythmogenic right ventricular dysplasia]] are constant and do not very with vagotonic agents, beta-adrenergic blockers, or sodium channel blockers.
Patients with Brugada syndrome will sometimes have a family history of [[sudden cardiac death]] and a personal history of of arrhythmias. If patients are symptomatic they often have symptoms of [[syncope]], [[seizures]], [[agonal breathing]], difficulty breathing, and patients may even present with [[sudden death]].  These symptoms most often come on either at rest or during sleep.


==Epidemiology and Demographics==
===Physical Examination===
Insofar as Brugada syndrome is a relatively newly recognized syndrome, its incidence and prevalence continues to increaseBrugada syndrome is quite common in Southeast Asia where it is endemic, and affects 50 out of every 10,000 individualsIt 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.
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 patternIn 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.


==Prevalence==
===Laboratory Findings===
The prevalence of the Brugada syndrome is estimated at 5-50:10,000, largely depending on geographic location.  
[[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.


==Age==
===Electrocardiogram===
The average age at the time of initial diagnosis or sudden death is 40 ± 22 years, with the youngest patient diagnosed at 2 days of age and the oldest at 84 years.  Brugada syndrome usually becomes apparent in adulthood, although signs and symptoms, including sudden death, can occur any time from early infancy to old age. The mean age of sudden death is approximately 40 years. This condition may explain some cases of sudden infant death syndrome (SIDS), which is a major cause of death in babies younger than one year. It is characterized by sudden and unexplained death, usually during sleepSudden unexplained nocturnal death syndrome (SUNDS) is a condition characterized by unexpected cardiac arrest in young adults, usually at night during sleep. This condition was originally described in Southeast Asian populations, where it is a major cause of death. Researchers have determined that SUNDS and Brugada syndrome are the same disorder.
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 changesPatients 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 [[Brugada syndrome risk factors|triggers]] or [[Brugada syndrome risk factors|risk factors]].


==Race==
===Chest X Ray===
This condition occurs much more frequently in people of Asian ancestry, particularly in Japanese and Southeast Asian populations. It is the most common cause of sudden death in young men without known underlying cardiac disease in Thailand and Laos<ref>Brugada J, Brugada P, Brugada R. The syndrome of right bundle branch block ST segment elevation in V1 to V3 and sudden death--the Brugada syndrome. Europace. 1999 Jul;1(3):156-66. PMID 11225790 </ref>.  In some southeast Asian countries the disease is considered endemic and believed to be the second cause of death among young men (after car accidents). In these countries Brugada syndrome is believed to underly (in part) the 'Sudden Unexpected Death Syndrome' (SUDS). This relation has, however, not been thoroughly investigated and there are almost no epidemiological studies into Brugada syndrome ECGs (apart from Japan). In different Asian countries, different names have been given to SUDS: in the Phillipines it is called ''bangungut'' (to rise and moan in sleep) and in Thailand ''lai tai'' (death during sleep).
Insofar as Brugada syndrome is not associated with structural abnormalities of the heart, there are no associated abnormalities on the chest x-ray.
===Echocardiography or Ultrasound===
There is ongoing controversy as to whether there are structural abnormalities among patients with Brugada syndrome. There was one small study of 11 patients with Brugada syndrome that demonstrated a rapid swinging motion shifting towards the right ventricle of the basal segment of the intraventricular septum and early systole in 73% (8/11) of patients with Brugada syndrome.  None of the control patients demonstrated this abnormality.<ref name="pmid18067763">{{cite journal |author=Huang ZR, Chen LL, Li WH, Tang QZ, Huang CX, Xie Q, Wu G, Fan L |title=Interventricular septum motion abnormalities: unexpected echocardiographic changes of Brugada syndrome |journal=[[Chinese Medical Journal]] |volume=120 |issue=21 |pages=1898–901 |year=2007 |month=November |pmid=18067763 |doi= |url=http://www.cmj.org/Periodical/LinkIn.asp?journal=Chinese%20Medical%20Journal&linkintype=pubmed&year=2007&vol=120&issue=21&beginpage=1898 |issn= |accessdate=2012-10-13}}</ref>


==Gender==
===Electrophysiologic Studies===
Although Brugada syndrome affects both men and women, the condition appears to be 8 to 10 times more common in men. Researchers suspect that testosterone, a sex hormone present at much higher levels in men, may be responsible for this difference.
Patients who are inducible at the time electrophysiologic study have an eightfold increased risk of aborted [[sudden cardiac death]] compared with those patients who are not inducible.<ref> <div>'' Brugada J, Brugada R, Brugada P. Determinants of sudden cardiac death in individuals with the electrocardiographic pattern of Brugada syndrome and no previous cardiac arrest. Circulation''. '' 2003; 108: 3092–3096.''</div></ref>  Some groups have advocated that programmed electrical stimulation (PES) be performed to induce [[ventricular fibrillation]] for risk assessment in Brugada patients <ref name="pmid11772879">{{cite journal |author=Brugada J, Brugada R, Antzelevitch C, Towbin J, Nademanee K, Brugada P |title=Long-term follow-up of individuals with the electrocardiographic pattern of right bundle-branch block and ST-segment elevation in precordial leads V1 to V3 |journal=[[Circulation]] |volume=105 |issue=1 |pages=73–8 |year=2002 |month=January |pmid=11772879 |doi= |url=http://circ.ahajournals.org/cgi/pmidlookup?view=long&pmid=11772879 |issn= |accessdate=2012-10-13}}</ref><ref name="pmid12776858">{{cite journal |author=Brugada P, Brugada R, Mont L, Rivero M, Geelen P, Brugada J |title=Natural history of Brugada syndrome: the prognostic value of programmed electrical stimulation of the heart |journal=[[Journal of Cardiovascular Electrophysiology]] |volume=14 |issue=5 |pages=455–7 |year=2003 |month=May |pmid=12776858 |doi= |url=http://onlinelibrary.wiley.com/resolve/openurl?genre=article&sid=nlm:pubmed&issn=1045-3873&date=2003&volume=14&issue=5&spage=455 |issn= |accessdate=2012-10-13}}</ref>  Other groups have not reproduced the predictive value of these tests,<ref name="pmid11901046">{{cite journal |author=Priori SG, Napolitano C, Gasparini M, Pappone C, Della Bella P, Giordano U, Bloise R, Giustetto C, De Nardis R, Grillo M, Ronchetti E, Faggiano G, Nastoli J |title=Natural history of Brugada syndrome: insights for risk stratification and management |journal=[[Circulation]] |volume=105 |issue=11 |pages=1342–7 |year=2002 |month=March |pmid=11901046 |doi= |url=http://circ.ahajournals.org/cgi/pmidlookup?view=long&pmid=11901046 |issn= |accessdate=2012-10-13}}</ref><ref name="pmid15642768">{{cite journal |author=Eckardt L, Probst V, Smits JP, Bahr ES, Wolpert C, Schimpf R, Wichter T, Boisseau P, Heinecke A, Breithardt G, Borggrefe M, LeMarec H, Böcker D, Wilde AA |title=Long-term prognosis of individuals with right precordial ST-segment-elevation Brugada syndrome |journal=[[Circulation]] |volume=111 |issue=3 |pages=257–63 |year=2005 |month=January |pmid=15642768 |doi=10.1161/01.CIR.0000153267.21278.8D |url=http://circ.ahajournals.org/cgi/pmidlookup?view=long&pmid=15642768 |issn= |accessdate=2012-10-13}}</ref> so the value of programmed electrical stimulation (PES) and inducibility remains controversial.


==Risk Factors: Agents and Scenarios that Provoke the Brugada Syndrome Pattern==
===Genetic Testing===
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)<ref name="pmid15898165">{{cite journal |author=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 |title=Brugada syndrome: report of the second consensus conference |journal=[[Heart Rhythm : the Official Journal of the Heart Rhythm Society]] |volume=2 |issue=4 |pages=429–40 |year=2005 |month=April |pmid=15898165 |doi= |url= |issn= |accessdate=2012-10-13}}</ref>:
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. Genetic testing can be used to support the diagnosis of Brugada syndrome and to detect relatives at risk.<ref name="pmid15898165">{{cite journal |author=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 |title=Brugada syndrome: report of the second consensus conference |journal=[[Heart Rhythm : the Official Journal of the Heart Rhythm Society]] |volume=2 |issue=4 |pages=429–40 |year=2005 |month=April |pmid=15898165 |doi= |url= |issn= |accessdate=2012-10-14}}</ref>
*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==
==Treatment==
As shown by the racing below, The EKG characteristics of Bugada syndrome include:
Implantation of a [[cardiac defibrillator]] is the only proven method of treatment in Brugada syndrome.Patients with aborted [[sudden cardiac death]] are at high risk for recurrence and should undergo [[AICD]] implantation, and do not require an electrophysiologic study to assess inducibility.  Patients with symptoms (either [[syncope]], [[seizures]] or nocturnal [[agonal respirations]]) should undergo implantation of a [[defibrillator]] if no other cause of their symptoms can be identified.  Asymptomatic patients should undergo electrophysiologic testing, and if [[VT]] / [[VF]] can be induced, they should undergo implantation of an [[ICD]].  Asymptomatic patients who cannot be induced should followed-up closely.  Patients who are asymptomatic with no family history of Brugada syndrome can be followed-up closely.
*a) A broad [[P-wave]] with some [[PQ prolongation]]
===Drugs to Avoid===
*b) [[J point]] elevation in the right precordial leads (V<sub>1</sub>-V<sub>3</sub>)
There are certain drugs that should be avoided in patients with Brugada syndrome.  These drugs include [[ajmaline]], [[flecainide]], pilsicainide, [[procainamide]], and [[propafenone]]. These drugs are all sodium blocking [[antiarrhythmic]]s which are either in the IA class or IC class.
*c) Coved [[ST segment elevation]]
*d) An inverted [[T wave]]


[[File:Brugada ecg characteristics.png|center|500px]]
===Drugs to Preferably Avoid===
Drugs which are not contraindicated in Brugada syndrome, but which should be avoided, are [[amiodarone]], [[cibenzoline]], [[disopyramide]], [[lidocaine]], [[propanolol]], and [[verapamil]]. These agents are all antiarrhythmics. Topical lidocaine used for anesthesia is thought to be safe when used in persons with Brugada syndrome.


==References==
==References==
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[[CME Category::Cardiology]]
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Latest revision as of 05:51, 15 March 2016

Brugada syndrome Microchapters

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Overview

Historical Perspective

Classification

Pathophysiology

Differentiating Brugada syndrome from other Diseases

Epidemiology and Demographics

Risk Factors

Screening

Natural History, Complications and Prognosis

Diagnosis

Diagnostic Criteria

History and Symptoms

Physical Examination

Laboratory Findings

Electrocardiogram

Examples of Type I Brugada Syndrome

Chest X Ray

Echocardiography or Ultrasound

Electrophysiologic Studies

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Treatment

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

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. Brugada syndrome is a condition that causes a disruption of the heart's normal rhythm. Specifically, this disorder can lead to uncoordinated electrical activity in the heart's lower chambers (ventricles), an abnormality called ventricular arrhythmia. If untreated, the irregular heartbeats can cause fainting (syncope), seizures, difficulty breathing, or sudden death. These complications typically occur when an affected person is resting or asleep.

Historical Perspective

Brugada syndorme was potentially first seen on EKG in survivors of cardiac arrest in 1989, but it was not until 1992 that the Brugada brothers recognized it as a distinct clinical entity which could cause sudden death by ventricular fibrillation.

Classification

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.

Pathophysiology

Approximately 20% of persons with Brugada syndome have a mutation in the gene SCN5A. This gene encodes for the sodium ion channel. The mutation is inherited in an autosomal dominant pattern, and is more commonly seen in males. Brugada syndrome has also been shown to result from defects in a calcium channel.

Differentiating Brugada syndrome from other Diseases

Brugada syndrome should be differentiated from other cardiac disorders, electrolyte disturbances, and drug intoxication syndromes. The condition which most similarly presents to Brugada syndrome is arrhythmogenic right ventricular dysplasia, as they both cause sudden cardiac death in children. Brugada syndrome can be differentiated from arrhythmogenic right ventricular dysplasia by the genetic counterpart of SCN5A, the lack of structural abnormalities within the heart, the association with polymorphic ventricular tachycardia during sleep, and EKG changes that are enhanced by vagotonic agents.

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 500 out of every 100,000 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] Unfortunately, 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

Brugada syndrome usually becomes apparent in adulthood, although it may present in infants and children as sudden cardiac death. The mean age of sudden death in patients with Brugada syndrome is 40 years old. The Brugada patient may develop atrial arrhythmias and abnormalities in atrial conduction, and these abnormalities are associated with inducibility of ventricular fibrillation. Implantation of a cardiac defibrillator AICD can improve prognosis for some.

Diagnosis

Diagnostic Criteria

The diagnosis of brugada syndrome is based upon electrocardiographic and clinical criteria. Only the Type I Brugada pattern qualifies as part of the diagnostic criteria for Brugada syndrome. Other rhythm abnormalities and family history are also taken into account when making the diagnosis of Brugada syndrome.

History and Symptoms

Patients with Brugada syndrome will sometimes have a family history of sudden cardiac death and a personal history of of arrhythmias. If patients are symptomatic they often have symptoms of syncope, seizures, agonal breathing, difficulty breathing, and patients may even present with sudden death. 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.

Echocardiography or Ultrasound

There is ongoing controversy as to whether there are structural abnormalities among patients with Brugada syndrome. There was one small study of 11 patients with Brugada syndrome that demonstrated a rapid swinging motion shifting towards the right ventricle of the basal segment of the intraventricular septum and early systole in 73% (8/11) of patients with Brugada syndrome. None of the control patients demonstrated this abnormality.[2]

Electrophysiologic Studies

Patients who are inducible at the time electrophysiologic study have an eightfold increased risk of aborted sudden cardiac death compared with those patients who are not inducible.[3] Some groups have advocated that programmed electrical stimulation (PES) be performed to induce ventricular fibrillation for risk assessment in Brugada patients [4][5] Other groups have not reproduced the predictive value of these tests,[6][7] so the value of programmed electrical stimulation (PES) and inducibility remains controversial.

Genetic Testing

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. Genetic testing can be used to support the diagnosis of Brugada syndrome and to detect relatives at risk.[1]

Treatment

Implantation of a cardiac defibrillator is the only proven method of treatment in Brugada syndrome.Patients with aborted sudden cardiac death are at high risk for recurrence and should undergo AICD implantation, and do not require an electrophysiologic study to assess inducibility. Patients with symptoms (either syncope, seizures or nocturnal agonal respirations) should undergo implantation of a defibrillator if no other cause of their symptoms can be identified. Asymptomatic patients should undergo electrophysiologic testing, and if VT / VF can be induced, they should undergo implantation of an ICD. Asymptomatic patients who cannot be induced should followed-up closely. Patients who are asymptomatic with no family history of Brugada syndrome can be followed-up closely.

Drugs to Avoid

There are certain drugs that should be avoided in patients with Brugada syndrome. These drugs include ajmaline, flecainide, pilsicainide, procainamide, and propafenone. These drugs are all sodium blocking antiarrhythmics which are either in the IA class or IC class.

Drugs to Preferably Avoid

Drugs which are not contraindicated in Brugada syndrome, but which should be avoided, are amiodarone, cibenzoline, disopyramide, lidocaine, propanolol, and verapamil. These agents are all antiarrhythmics. Topical lidocaine used for anesthesia is thought to be safe when used in persons with Brugada syndrome.

References

  1. 1.0 1.1 1.2 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 |month= ignored (help); |access-date= requires |url= (help)
  2. Huang ZR, Chen LL, Li WH, Tang QZ, Huang CX, Xie Q, Wu G, Fan L (2007). "Interventricular septum motion abnormalities: unexpected echocardiographic changes of Brugada syndrome". Chinese Medical Journal. 120 (21): 1898–901. PMID 18067763. Retrieved 2012-10-13. Unknown parameter |month= ignored (help)
  3. Brugada J, Brugada R, Brugada P. Determinants of sudden cardiac death in individuals with the electrocardiographic pattern of Brugada syndrome and no previous cardiac arrest. Circulation. 2003; 108: 3092–3096.
  4. Brugada J, Brugada R, Antzelevitch C, Towbin J, Nademanee K, Brugada P (2002). "Long-term follow-up of individuals with the electrocardiographic pattern of right bundle-branch block and ST-segment elevation in precordial leads V1 to V3". Circulation. 105 (1): 73–8. PMID 11772879. Retrieved 2012-10-13. Unknown parameter |month= ignored (help)
  5. Brugada P, Brugada R, Mont L, Rivero M, Geelen P, Brugada J (2003). "Natural history of Brugada syndrome: the prognostic value of programmed electrical stimulation of the heart". Journal of Cardiovascular Electrophysiology. 14 (5): 455–7. PMID 12776858. Retrieved 2012-10-13. Unknown parameter |month= ignored (help)
  6. Priori SG, Napolitano C, Gasparini M, Pappone C, Della Bella P, Giordano U, Bloise R, Giustetto C, De Nardis R, Grillo M, Ronchetti E, Faggiano G, Nastoli J (2002). "Natural history of Brugada syndrome: insights for risk stratification and management". Circulation. 105 (11): 1342–7. PMID 11901046. Retrieved 2012-10-13. Unknown parameter |month= ignored (help)
  7. Eckardt L, Probst V, Smits JP, Bahr ES, Wolpert C, Schimpf R, Wichter T, Boisseau P, Heinecke A, Breithardt G, Borggrefe M, LeMarec H, Böcker D, Wilde AA (2005). "Long-term prognosis of individuals with right precordial ST-segment-elevation Brugada syndrome". Circulation. 111 (3): 257–63. doi:10.1161/01.CIR.0000153267.21278.8D. PMID 15642768. Retrieved 2012-10-13. Unknown parameter |month= ignored (help)

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