Editing Brugada syndrome (section)

== Diagnosis ==

=== Electrocardiography ===
[[Image:Brugada.jpg|right|thumb|upright=1.6|ECG pattern in Brugada syndrome. According to consensus guidelines, Type 1 ST segment elevation, either spontaneously present or induced with the sodium channel-blocker challenge test, is considered diagnostic. Type 2 and 3 may lead to suspicion, but provocation testing is required for diagnosis. The ECGs in the right and left panels are from the same patient before (right panel, type 3) and after (left panel, type 1) administration of Ajmaline.]]

Brugada syndrome is diagnosed by identifying characteristic patterns on an [[Electrocardiography|electrocardiogram]].<ref name="Postema_2009" /> The pattern seen on the ECG includes [[ST elevation]] in leads V<sub>1</sub>-V<sub>3</sub> with a [[right bundle branch block]] (RBBB) appearance. There may be evidence of a slowing of electrical conduction within the heart, as shown by a prolonged [[PR interval]]. These patterns may be present all the time, but may appear only in response to particular drugs (see below), when the person has a [[fever]], during exercise, or as a result of other triggers. The ECG pattern may become more obvious by performing an ECG in which some of the electrodes are placed in different positions from usual, specifically by placing leads V<sub>1</sub> and V<sub>2</sub> higher up the chest wall in the 1st or 2nd intercostal spaces.<ref name="Obeyesekere_2011" />

Three forms of the Brugada ECG pattern have historically been described,<ref name=":3">{{Cite journal|last1=Wilde|first1=A. a. M.|last2=Antzelevitch|first2=C.|last3=Borggrefe|first3=M.|last4=Brugada|first4=J.|last5=Brugada|first5=R.|last6=Brugada|first6=P.|last7=Corrado|first7=D.|last8=Hauer|first8=R. N. W.|last9=Kass|first9=R. S.|last10=Nademanee|first10=K.|last11=Priori|first11=S. G.|date=November 2002|title=Proposed diagnostic criteria for the Brugada syndrome|journal=European Heart Journal|volume=23|issue=21|pages=1648–1654|doi=10.1053/euhj.2002.3382|issn=0195-668X|pmid=12448445|doi-access=free}}</ref> although the Type 3 pattern is frequently merged with the Type 2 pattern in contemporary practice.<ref name=":4">{{Cite journal|last1=Bayés de Luna|first1=Antonio|last2=Brugada|first2=Josep|last3=Baranchuk|first3=Adrian|last4=Borggrefe|first4=Martin|last5=Breithardt|first5=Guenter|last6=Goldwasser|first6=Diego|last7=Lambiase|first7=Pier|last8=Riera|first8=Andrés Pérez|last9=Garcia-Niebla|first9=Javier|last10=Pastore|first10=Carlos|last11=Oreto|first11=Giuseppe|date=September 2012|title=Current electrocardiographic criteria for diagnosis of Brugada pattern: a consensus report|url=https://pubmed.ncbi.nlm.nih.gov/22920782|journal=Journal of Electrocardiology|volume=45|issue=5|pages=433–442|doi=10.1016/j.jelectrocard.2012.06.004|issn=1532-8430|pmid=22920782}}</ref>
* Type 1 has a coved type ST elevation with at least 2&nbsp;mm (0.2 mV) [[QRS complex#J-point|J-point]] elevation and a gradually descending [[ST segment]] followed by a negative [[T wave|T-wave]].<ref name=":4" />
* Type 2 has a saddle-back pattern with at least 2&nbsp;mm J-point elevation and at least 0.5&nbsp;mm elevation of the terminal ST segment with a positive or biphasic T-wave.<ref name=":4" /> A type 2 pattern can occasionally be seen in healthy subjects.
* Type 3 has  a saddle-back (type 2 like) pattern, with at least 2&nbsp;mm J-point elevation but less than 1&nbsp;mm elevation of the terminal ST segment.<ref name=":3" /> 
According to current recommendations, only a Type 1 ECG pattern, occurring either spontaneously or in response to medication, can be used to confirm the diagnosis of Brugada syndrome as Type 2 and 3 patterns are not infrequently seen in persons without the disease.<ref name = Pri2013/>

=== Provocation testing ===
Some medications, particularly antiarrhythmic drugs that block the cardiac sodium current ''I''<sub>Na,</sub> can reveal a Type 1 Brugada pattern in susceptible people.  These drugs can be used to help make a diagnosis in those suspected of having Brugada syndrome (e.g. survivors of an unexplained cardiac arrest, family members of a person with Brugada syndrome) but in whom a diagnostic ECG pattern has not been seen.<ref name="Pol2017" />  In these cases, sodium current blocking medications can be given in a controlled environment.<ref name="Obeyesekere_2011">{{cite journal | vauthors = Obeyesekere MN, Klein GJ, Modi S, Leong-Sit P, Gula LJ, Yee R, Skanes AC, Krahn AD | title = How to perform and interpret provocative testing for the diagnosis of Brugada syndrome, long-QT syndrome, and catecholaminergic polymorphic ventricular tachycardia | journal = Circulation: Arrhythmia and Electrophysiology | volume = 4 | issue = 6 | pages = 958–64 | date = December 2011 | pmid = 22203660 | doi = 10.1161/CIRCEP.111.965947 | doi-access = free }}</ref> The most commonly used drugs for this purpose are [[ajmaline]], flecainide, and [[procainamide]], with some suggestions indicating that ajmaline may be the most effective.<ref>{{cite journal | vauthors = Wolpert C, Echternach C, Veltmann C, Antzelevitch C, Thomas GP, Spehl S, Streitner F, Kuschyk J, Schimpf R, Haase KK, Borggrefe M | title = Intravenous drug challenge using flecainide and ajmaline in patients with Brugada syndrome | journal = Heart Rhythm | volume = 2 | issue = 3 | pages = 254–60 | date = March 2005 | pmid = 15851314 | pmc = 1474213 | doi = 10.1016/j.hrthm.2004.11.025 }}</ref> Precaution must be taken in giving these medications as there is a small risk of causing abnormal heart rhythms.<ref name="Obeyesekere_2011" />

=== Genetic testing ===
[[Genetic testing]] can be helpful to identify patients with Brugada syndrome, most commonly in family members of a person with Brugada syndrome, but sometimes performed in a person who has died suddenly and unexpectedly.<ref name=Sar2016/> However, interpretation of the results of genetic testing is challenging.  In family members who all carry a particular genetic variant associated with Brugada syndrome, some family members may show evidence of Brugada syndrome on their ECGs while others may not.<ref name=Sar2016 />  This means that carrying a genetic mutation associated with Brugada syndrome does not necessarily imply that a person is truly affected by the condition.  To further complicate matters, many frequently occurring variations in the SCN5A gene do not cause any problems, and therefore genetic variants are sometimes identified in persons with Brugada syndrome that are not truly causing the disease.<ref>{{cite journal | vauthors = Giudicessi JR, Ackerman MJ | title = Genetic testing in heritable cardiac arrhythmia syndromes: differentiating pathogenic mutations from background genetic noise | journal = Current Opinion in Cardiology | volume = 28 | issue = 1 | pages = 63–71 | date = January 2013 | pmid = 23128497 | pmc = 3705648 | doi = 10.1097/HCO.0b013e32835b0a41 }}</ref>

=== Other investigations ===
Invasive [[Electrophysiology study|electrophysiological studies]], in which wires are passed through a vein to stimulate and record electrical signals from the heart, can sometimes be used to assess the risk of a person with Brugada syndrome experiencing dangerous abnormal heart rhythms.<ref>{{cite journal | vauthors = Sroubek J, Probst V, Mazzanti A, Delise P, Hevia JC, Ohkubo K, Zorzi A, Champagne J, Kostopoulou A, Yin X, Napolitano C, Milan DJ, Wilde A, Sacher F, Borggrefe M, Ellinor PT, Theodorakis G, Nault I, Corrado D, Watanabe I, Antzelevitch C, Allocca G, Priori SG, Lubitz SA | display-authors = 6 | title = Programmed Ventricular Stimulation for Risk Stratification in the Brugada Syndrome: A Pooled Analysis | journal = Circulation | volume = 133 | issue = 7 | pages = 622–30 | date = February 2016 | pmid = 26797467 | pmc = 4758872 | doi = 10.1161/CIRCULATIONAHA.115.017885 }}</ref>  Risk stratification is also sometimes performed using a [[Signal-averaged electrocardiogram|signal averaged ECG]].<ref name=Sar2016 /> [[Holter monitor|Ambulatory ECG monitoring]], including implantation of a [[Implantable loop recorder|loop recorder]], is sometimes used to assess whether dizziness or faints in a person with Brugada syndrome are due to abnormal heart rhythms or other causes such as vasovagal syncope.<ref>{{cite journal | vauthors = Kubala M, Aïssou L, Traullé S, Gugenheim AL, Hermida JS | title = Use of implantable loop recorders in patients with Brugada syndrome and suspected risk of ventricular arrhythmia | journal = Europace | volume = 14 | issue = 6 | pages = 898–902 | date = June 2012 | pmid = 21979995 | doi = 10.1093/europace/eur319 | doi-access = free }}</ref>

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File:Brugada syndrome type1 example1 (CardioNetworks ECGpedia).png|Type 1 Brugada ECG pattern (note non-standard lead position, V<sub>5</sub> is placed one intercostal space above V<sub>1</sub> and V<sub>6</sub> is placed one intercostal space above V<sub>2).</sub>.
File:Brugada syndrome type2 example1 (CardioNetworks ECGpedia).png|Type 2 Brugada ECG pattern
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