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| {{Infobox Disease | | | {{Infobox Disease | |
| Name = Short QT syndrome | | | Name = Short QT syndrome | |
| Image = | | | Image = SinusRhythmLabels.svg | |
| Caption = | | | Caption = Schematic representation of normal ECG trace ''([[sinus rhythm]]),'' with waves, segments, and intervals labeled. | |
| DiseasesDB = 11105 | | | DiseasesDB = 11105 | |
| ICD10 = | | | ICD10 = {{ICD10|R|94|3|r|94}}| |
| ICD9 = | | | ICD9 = | |
| ICDO = | | | ICDO = | |
| OMIM = | | | OMIM = | |
| MedlinePlus = | | | MedlinePlus = | |
| eMedicineSubj = |
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| eMedicineTopic = |
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| MeshID = | | | MeshID = | |
| }} | | }} |
| {{Short QT syndrome}} | | {{Short QT syndrome}} |
| {{CMG}} | | {{CMG}} {{AE}}{{sumanthK}} |
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| {{SK}} SQTS; short QT; short QTc; QT interval shortening | | {{SK}} SQTS; short QT; short QTc; QT interval shortening |
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| ==[[Short_QT_syndrome_historical_perspective|Historical Perspective]]== | | ==[[Short_QT_syndrome_historical_perspective|Historical Perspective]]== |
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| ==Classification== | | ==[[Short QT syndrome classification|Classification]]== |
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| ==Pathophysiology== | | ==[[Short QT syndrome pathophysiology|Pathophysiology]]== |
| It has been hypothesized that short QT syndrome is due to increased activity of outward potassium currents in phase 2 and 3 of the [[cardiac action potential]]. This would cause a shortening of the plateau phase of the action potential (phase 2), causing a shortening of the overall [[action potential]], leading to an overall shortening of refractory periods and the [[QT interval]]. In the families afflicted by short QT syndrome, two different [[missense]] [[mutation]]s have been described in the ''human ether-a-go-go [[gene]] ([[HERG]])''. These mutations result in expression of the same amino acid change in the cardiac [[cardiac action potential|I<sub>Kr</sub> ion channel]]. This mutated I<sub>Kr</sub> has increased activity compared to the normal ion channel, and would theoretically explain the above hypothesis.
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| ===Genetics===
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| In the families afflicted by short QT syndrome, [[mutation]]s have been described in three genes, [[KvLQT1]], the ''human ether-a-go-go [[gene]] ([[HERG]])'', and [[KCNJ2]]. Mutations in the ''[[KCNH2]]'', ''[[KCNJ2]]'', and ''[[KCNQ1]]'' genes cause short QT syndrome. These genes provide instructions for making proteins that act as channels across the cell membrane. These channels transport positively charged atoms (ions) of potassium into and out of cells. In cardiac muscle, these ion channels play critical roles in maintaining the heart's normal rhythm. Mutations in the ''[[KCNH2]]'', ''[[KCNJ2]]'', or ''[[KCNQ1]]'' gene increase the activity of the channels, which changes the flow of potassium ions between cells. This disruption in ion transport alters the way the heart beats, leading to the abnormal heart rhythm characteristic of short QT syndrome. Short QT syndrome appears to have an [[autosomal dominant]] pattern of inheritance.
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| Due to the [[autosomal dominant]] inheritance pattern, individuals may have family members with a history of unexplained or [[sudden death]] at a young age (even in [[infancy]]), [[palpitations]], or [[atrial fibrillation]]. The penetrance of symptoms is high in affected family members.
| | ==[[Short QT syndrome causes|Causes]]== |
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| ==Causes== | | ==[[Short QT syndrome triggers|Triggers]]== |
| The causes of shortening of the [[QT interval]] can be divided into primary causes (Short QT syndrome types 1-5) and secondary causes such as drugs and electrolyte disturbances.
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| ===Common Causes=== | | ==[[Short QT syndrome differential diagnosis|Differentiating Short QT Syndrome from other Diseases]]== |
| *[[Hypercalcemia]]
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| *[[Digoxin]]
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| ===Causes in Alphabetical Order=== | | ==[[Short QT syndrome epidemiology and demographics|Epidemiology and Demographics]]== |
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| * [[Acidosis]]
| | ==[[Short QT syndrome screening|Screening]]== |
| * Altered [[autonomic tone]]
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| * [[Digoxin]]
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| * [[Hypercalcaemia]]
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| * [[Hyperkalemia]]
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| * [[Hyperthermia]]
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| * [[Lanatoside C]]
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| * [[Rufinamide]]
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| * [[Short QT syndrome type 1]]
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| * [[Short QT syndrome type 2]]
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| * [[Short QT syndrome type 3]]
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| * [[Short QT syndrome type 4]]
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| * [[Short QT syndrome type 5]]
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| | ==[[Short QT syndrome natural history, complications and prognosis|Natural History, Complications, Prognosis]]== |
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| | ==[[Diagnosis]]== |
| | [[Short QT syndrome diagnostic criteria|Diagnostic Criteria]] | [[Short QT syndrome history and symptoms|History and Symptoms]] | [[Short QT syndrome physical examination|Physical Examination]] | [[Short QT syndrome laboratory findings|Laboratory Findings]] | [[Short QT syndrome electrocardiogram|Electrocardiogram]] | [[Short QT syndrome electrophysiologic studies|Electrophysiologic Studies]] | [[Short QT syndrome genetic testing|Genetic Testing]] |
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| ===Differentiating Short QT Syndrome from other Disorders=== | | ==[[Treatment]]== |
| In contrast to [[Long QT Syndrome]] ([[LQTS]]), there is often no specific trigger (such as a loud noise or exercise) for an episode of [[arrhythmia]].
| | [[Short QT syndrome AICD placement|AICD placement]] | [[Short QT syndrome medical therapy|Medical Therapy]] |
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| ==Epidemiology and Demographics==
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| Since the syndrome was first described in 2000, < 30 cases have been identified.
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| ===Age===
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| The median age of presentation is 30 years, but ranges from just weeks to the sixth decade of life.
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| ==Natural History, Complications, Prognosis==
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| Short QT syndrome is associated with an increased risk of [[atrial fibrillation]], [[syncope]] and [[sudden death]] due to [[ventricular fibrillation]].
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| ==Screening==
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| A young patient with [[lone atrial fibrillation]] should be assessed for [[short QT syndrome]].
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| ==Diagnosis==
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| Secondary causes of a short QT interval such as drugs and electrolyte disturbances should be ruled out before embarking on an evaluation as to whether the patient has one of the short QT syndrome variants.
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| ===Diagnostic Criteria===
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| Recent diagnostic criteria have been published out of the Arrhythmia Research Laboratory at the [[University of Ottawa Heart Institute]] from Drs. Michael H Gollob and Jason D Roberts.<ref>{{cite journal | author=Gollob M, Redpath C, Roberts J. | title= The Short QT syndrome: Proposed Diagnostic Criteria | journal=J Am Coll Cardiol | year=2011 | pages=802–812 | volume=57 | issue=7 | pmid=21310316 | doi=10.1016/j.jacc.2010.09.048}}</ref>
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| The Short QT Syndrome diagnostic criteria is based on a point system as follows:
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| *[[QTc]] in milliseconds
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| ::<370 = 1 point
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| ::<350 = 2 points
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| ::<330 = 3 points
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| *J point - T peak interval in milliseconds
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| ::<120 = 1 point
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| *Clinical History
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| ::Sudden [[cardiac arrest]] = 2 points
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| ::[[Polymorphic VT]] or [[VF]] = 2 points
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| ::Unexplained [[syncope]] = 1 point
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| ::[[Atrial fibrillation]] = 1 point
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| *Family History
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| ::1st or 2nd degree relative with SQTS = 2 points
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| ::1st or 2nd degree relative with sudden death = 1 point
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| ::Sudden infant death syndrome = 1 point
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| *Genotype
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| ::Genotype positive = 2 points
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| ::Mutation of undetermined significance in a culprit gene = 1 point
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| The points are summed and interpreted as follows:
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| *'''> or equal to 4 points:''' High-probability of SQTS
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| *'''3 Points:''' Intermediate probability of SQTS
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| *'''2 points or less:''' Low probability of SQTS
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| ===Symptoms===
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| ====Sudden Death====
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| [[Sudden death]] may be the first presentation of the disease.
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| *The most common symptom of short QT syndrome is [[cardiac arrest]] (34%)<ref name="pmid17224476">{{cite journal | author = Antzelevitch C, Pollevick GD, Cordeiro JM, Casis O, Sanguinetti MC, Aizawa Y, Guerchicoff A, Pfeiffer R, Oliva A, Wollnik B, Gelber P, Bonaros EP, Burashnikov E, Wu Y, Sargent JD, Schickel S, Oberheiden R, Bhatia A, Hsu LF, Haïssaguerre M, Schimpf R, Borggrefe M, Wolpert C | title = Loss-of-function mutations in the cardiac calcium channel underlie a new clinical entity characterized by ST-segment elevation, short QT intervals, and sudden cardiac death | journal = [[Circulation]] | volume = 115 | issue = 4 | pages = 442–9 | year = 2007 | month = January | pmid = 17224476 | pmc = 1952683 | doi = 10.1161/CIRCULATIONAHA.106.668392 | url = http://circ.ahajournals.org/cgi/pmidlookup?view=long&pmid=17224476 | issn = | accessdate = 2012-09-02}}</ref>.
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| *The first symptom of short QT syndrome is most often [[cardiac arrest]] (28%)<ref name="pmid17224476">{{cite journal | author = Antzelevitch C, Pollevick GD, Cordeiro JM, Casis O, Sanguinetti MC, Aizawa Y, Guerchicoff A, Pfeiffer R, Oliva A, Wollnik B, Gelber P, Bonaros EP, Burashnikov E, Wu Y, Sargent JD, Schickel S, Oberheiden R, Bhatia A, Hsu LF, Haïssaguerre M, Schimpf R, Borggrefe M, Wolpert C | title = Loss-of-function mutations in the cardiac calcium channel underlie a new clinical entity characterized by ST-segment elevation, short QT intervals, and sudden cardiac death | journal = [[Circulation]] | volume = 115 | issue = 4 | pages = 442–9 | year = 2007 | month = January | pmid = 17224476 | pmc = 1952683 | doi = 10.1161/CIRCULATIONAHA.106.668392 | url = http://circ.ahajournals.org/cgi/pmidlookup?view=long&pmid=17224476 | issn = | accessdate = 2012-09-02}}</ref>
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| ====Syncope====
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| *[[Syncope]] is the first symptom in 24% of patients and is most likely due to self-terminating [[ventricular fibrillation]].
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| ====Palpitations====
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| *[[Palpitations]] are present in 31% of patients.
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| ====Atrial Fibrillation====
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| *[[Atrial fibrillation]] is present in up to 80% of patients with short QT syndrome.
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| ====Triggers====
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| In contrast to [[Long QT Syndrome]] ([[LQTS]]), there is often no specific trigger (such as a loud noise or exercise) for an episode of [[arrhythmia]].
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| ==Screening==
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| Short QT syndrome should be excluded in patients without structural heart disease presenting with sudden cardiac death.
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| ===Electrocardiogam===
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| [[Image:Short qt.jpg|right|thumb|Tall peaked T wave and short QT in the right precordial lead V2]]
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| The diagnosis of short QT syndrome on the EKG is based upon three criteria:
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| ====Duration of the QT Interval====
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| While the [[QT interval]] is generally short, the QT interval alone cannot be used to distinguish the patient with short QT syndrome from a normal patient (similar to [[long QT syndrome]]).<ref>Viskin S. The QT interval: Too long, too short or just right. Heart Rhythm 2009; 6: 711–715.</ref> In general though, if the QTc is < 330 msec in a male, and <340 msec in a female, then short QT syndrome can be diagnosed even in the absence of symptoms as these QT intervals are much shorter than in the rest of the population. On the other hand, if the QTc is moderately shortened to < 360 msec in a male or < 370 msec in a female, the short QT syndrome should only be diagnosed in the presence of symptoms or a family history given the overlap of these QT intervals with that of the healthy population.
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| =====SQTS 1,2,3=====
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| The QTc is < 300-320 msec.<ref name="pmid14676148">{{cite journal | author = Brugada R, Hong K, Dumaine R, Cordeiro J, Gaita F, Borggrefe M, Menendez TM, Brugada J, Pollevick GD, Wolpert C, Burashnikov E, Matsuo K, Wu YS, Guerchicoff A, Bianchi F, Giustetto C, Schimpf R, Brugada P, Antzelevitch C | title = Sudden death associated with short-QT syndrome linked to mutations in HERG | journal = [[Circulation]] | volume = 109 | issue = 1 | pages = 30–5 | year = 2004 | month = January | pmid = 14676148 | doi = 10.1161/01.CIR.0000109482.92774.3A | url = http://circ.ahajournals.org/cgi/pmidlookup?view=long&pmid=14676148 | issn = | accessdate = 2012-09-03}}</ref><ref name="pmid15159330">{{cite journal | author = Bellocq C, van Ginneken AC, Bezzina CR, Alders M, Escande D, Mannens MM, Baró I, Wilde AA | title = Mutation in the KCNQ1 gene leading to the short QT-interval syndrome | journal = [[Circulation]] | volume = 109 | issue = 20 | pages = 2394–7 | year = 2004 | month = May | pmid = 15159330 | doi = 10.1161/01.CIR.0000130409.72142.FE | url = http://circ.ahajournals.org/cgi/pmidlookup?view=long&pmid=15159330 | issn = | accessdate = 2012-09-03}}</ref><ref name="pmid15761194">{{cite journal | author = Priori SG, Pandit SV, Rivolta I, Berenfeld O, Ronchetti E, Dhamoon A, Napolitano C, Anumonwo J, di Barletta MR, Gudapakkam S, Bosi G, Stramba-Badiale M, Jalife J | title = A novel form of short QT syndrome (SQT3) is caused by a mutation in the KCNJ2 gene | journal = [[Circulation Research]] | volume = 96 | issue = 7 | pages = 800–7 | year = 2005 | month = April | pmid = 15761194 | doi = 10.1161/01.RES.0000162101.76263.8c | url = http://circres.ahajournals.org/cgi/pmidlookup?view=long&pmid=15761194 | issn = | accessdate = 2012-09-03}}</ref>
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| =====SQTS 4,5=====
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| The QTc is just under 360 msec <ref>Antzelevitch C, Pollevick GD, Cordeiro JM et al. Loss-of-function mutations in the cardiac calcium channel underlie a new clinical entity characterized by ST- segment elevation, short QT intervals, and sudden cardiac death. Circulation 2007: 115: 442-449.</ref>
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| ====Variability of the QT Interval with Heart Rate====
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| The short [[QT interval]] does not vary significantly with the heart rate. Normally the QT will become longer at slow heart rates and this does not occur among patients with short QT syndrome. The Bazett formula may overcorrect (i.e. shorten) the [[QT interval]] in the patient with [[bradycardia]], and it is therefore important to use treadmill testing to increase the heart rate and confirm the absence of [[QT interval]] variation.<ref>Moreno-Reviriego S, Merino JL.Short QT Syndrome. An article from the E-Journal of the ESC Council for Cardiology Practice. Vol9 N°2, 17 Sep 2010 [http://www.escardio.org/communities/councils/ccp/e-journal/volume9/Pages/Short_Qt_Syndrome_Reviriego.aspx]</ref>
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| ====Morphology of the T Wave====
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| =====SQT1=====
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| Tall, narrow, peaked, symmetric [[T waves]] in the right precordial leads.
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| =====SQT3=====
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| Asymmetric peaked T waves due to more rapid repolarization at the end of the T wave.
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| =====SQT4 and 5=====
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| There is [[Brugada syndrome]]-like [[ST segment]] elevation in leads V1 and V2.
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| ====Morphology of the ST Segment====
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| The [[ST segment]] is short or even missing. The [[T wave]] begins right after the S wave.
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| ====Early Repolarization====
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| In a very limited number of patients it has been observed that [[early repolarization]] (which is present in 65% of patients with SQTS) and a longer [[T wave]] peak to T wave end period is associated with the occurrence of arrhythmic events<ref name="pmid20206319">{{cite journal | author = Watanabe H, Makiyama T, Koyama T, Kannankeril PJ, Seto S, Okamura K, Oda H, Itoh H, Okada M, Tanabe N, Yagihara N, Kamakura S, Horie M, Aizawa Y, Shimizu W | title = High prevalence of early repolarization in short QT syndrome | journal = [[Heart Rhythm : the Official Journal of the Heart Rhythm Society]] | volume = 7 | issue = 5 | pages = 647–52 | year = 2010 | month = May | pmid = 20206319 | doi = 10.1016/j.hrthm.2010.01.012 | url = http://linkinghub.elsevier.com/retrieve/pii/S1547-5271(10)00034-2 | issn = | accessdate = 2012-09-03}}</ref>.
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| ====Rhythm====
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| 70% of patients with short QT have a history of either [[paroxysmal atrial fibrillation]] or [[permanent atrial fibrillation]], and [[atrial fibrillation]] is the first sign of short QT syndrome in 50% of patients. In young patients with [[lone atrial fibrillation]], the patient should be screened for short QT syndrome.
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| ===Electrophysiologic Studies===
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| Among patients with SQTS, the atrial and ventricular refractory periods are shortened (ranging from 120 to 180 ms). [[Ventricular fibrillation]] can be induced on [[programmed stimulation]] in 90% of patients with short QT syndrome. Despite the high rate of VF inducibility, the risk of sudden death in an individual patient is difficult to predict given the genetic and clinical heterogeneity of short QT syndrome and the limited number of patients with short follow-up to date. The limitations of electrophysiologic testing are highlighted by a study of Giustetto et al in which the sensitivity of electrophysiologic testing in relation to the clinical occurrence of [[ventricular fibrillation]] was only 50% (3 of 6 cases)<ref name="pmid17224476">{{cite journal | author = Antzelevitch C, Pollevick GD, Cordeiro JM, Casis O, Sanguinetti MC, Aizawa Y, Guerchicoff A, Pfeiffer R, Oliva A, Wollnik B, Gelber P, Bonaros EP, Burashnikov E, Wu Y, Sargent JD, Schickel S, Oberheiden R, Bhatia A, Hsu LF, Haïssaguerre M, Schimpf R, Borggrefe M, Wolpert C | title = Loss-of-function mutations in the cardiac calcium channel underlie a new clinical entity characterized by ST-segment elevation, short QT intervals, and sudden cardiac death | journal = [[Circulation]] | volume = 115 | issue = 4 | pages = 442–9 | year = 2007 | month = January | pmid = 17224476 | pmc = 1952683 | doi = 10.1161/CIRCULATIONAHA.106.668392 | url = http://circ.ahajournals.org/cgi/pmidlookup?view=long&pmid=17224476 | issn = | accessdate = 2012-09-03}}</ref>. Importantly, lack of inducibility does not exclude a future episode of [[ventricular fibrillation]]<ref name="pmid15851347">{{cite journal | author = Schimpf R, Bauersfeld U, Gaita F, Wolpert C | title = Short QT syndrome: successful prevention of sudden cardiac death in an adolescent by implantable cardioverter-defibrillator treatment for primary prophylaxis | journal = [[Heart Rhythm : the Official Journal of the Heart Rhythm Society]] | volume = 2 | issue = 4 | pages = 416–7 | year = 2005 | month = April | pmid = 15851347 | doi = 10.1016/j.hrthm.2004.11.026 | url = http://linkinghub.elsevier.com/retrieve/pii/S1547-5271(04)00886-0 | issn = | accessdate = 2012-09-03}}</ref>. Thus, the role of electrophysiologic testing in risk stratification of the patient with SQTS is not clear at present.
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| ===Genetic Testing===
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| Because new genetic variants of SQTS are still being identified, a negative genetic test for existing variants does not exclude the presence of SQTS. A negative genetic test for existing variants could mean that a patient with a short QT interval does not have a heretofore unidentified variant of SQTS.
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| However, among family members of an affected patient, genetic testing may identify the syndrome in an asymptomatic patient, and may also rule out the presence of the syndrome in asymptomatic patients.
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| Mutations in the ''[[KCNH2]]'', ''[[KCNJ2]]'', and ''[[KCNQ1]]'' genes cause short QT syndrome. These genes provide instructions for making proteins that act as channels across the cell membrane. These channels transport positively charged atoms (ions) of potassium into and out of cells. In [[cardiac muscle]], these ion channels play critical roles in maintaining the heart's normal rhythm. Mutations in the ''KCNH2'', ''KCNJ2'', or ''KCNQ1'' gene increase the activity of the channels, which changes the flow of potassium ions between cells. This disruption in ion transport alters the way the heart beats, leading to the abnormal heart rhythm characteristic of short QT syndrome. Short QT syndrome appears to have an autosomal dominant pattern of inheritance.
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| ====Centers Performing Genetic Testing for Short QT Syndrome====
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| *[http://ghr.nlm.nih.gov/exit?to=www.ncbi.nlm.nih.gov&vje=7bH4sIAAAAAAAAABXKMQrDMAwF0KvkBFZKITTdCoVOzZRdOLZoPjhyiUS99PAhb36paoajKs-7RN9EnZ.To5vFnN..1f17J2qtBU0LgpYtKNbwqT8yuBi9ROXMRiUulAoUKRbOMIkmjEzXy9jfhgNml6ZqaQAAAA__ Gene Tests: Short QT Syndrome 1]
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| *[http://ghr.nlm.nih.gov/exit?to=www.ncbi.nlm.nih.gov&vje=7bH4sIAAAAAAAAABXKMQ6DMAwF0KtwgpiqA6VbpUqdysRuhcQqXwpOha1m6eERb36paoajKs-7RN9EnZ.To5vFnN..1f17J2qtBU0LgpYtKNbwqT8yuBi9ROXMRiUulAoUKRbOMIkmjEzXy9jfhgPwp6EdaQAAAA__ Gene Tests: Short QT Syndrome 2]
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| *[http://ghr.nlm.nih.gov/exit?to=www.ncbi.nlm.nih.gov&vje=7bH4sIAAAAAAAAABXKMQ7CMAwF0Kv0BHERS-lWCYkJpu5WmljNl1IH1RZZODzizS81zXA05fWU6Ieo8.21DKuY8.Nb3N8zUe89aNoQtB5BUcLePmRwMXqIyj8b1bhRqlCkWDnDJJowMl0vt3GafmG6Ho1pAAAA Gene Tests: Short QT Syndrome 3]
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| ==Treatment==
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| ===Device Based Therapy===
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| An [[implantable cardioverter-defibrillator]] ([[ICD]]) is indicated in<ref>Borggrefe M. FESC, Wolpert C, Veltmann C, Giustetto C, Gaita F, Schimpf R. Short QT Syndrome : A new primary electrical disease, ESC E journal, Vol 3 N°34, 10 May 2005. [http://www.escardio.org/communities/councils/ccp/e-journal/volume3/Pages/vol3n34.aspx]</ref>:
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| *Symptomatic patients
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| *Patients with a family history of [[sudden cardiac death]]
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| Generally accepted criteria for implantation of an [[AICD]] also include:
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| *Inducibility on electrophysiologic testing
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| *Positive genetic test, although a negative result does not exclude the presence of a previously unreported mutation or the occurrence of a future arrhythmic event
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| ====Complications of AICD Placement====
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| Inappropriate shocks may be delivered due to<ref>Schimpf R, Wolpert C, Bianchi F, et al. Congenital Short QT Syndrome and Implantable Cardioverter Defibrillator Treatment: Inherent Risk for Inappropriate Shock Delivery. J Cardiovasc Electrophysiol 2003; 14: 1273-1277.</ref>:
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| *The occurence of tachycardias such as [[sinus tachycardia]] and [[atrial fibrillation]].
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| *Oversensing of the tall, narrow peaked [[T wave]]
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| ===Pharmacologic Therapy===
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| ====Short QT Syndrome 1 (SQT1)====
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| The efficacy of pharmacotherapy in preventing [[ventricular fibrillation]] has only been studies in patients with SQT1. Given the limited number of patients studied, and the limited duration of follow-up, pharmacotherapy as primary or secondary preventive therapy for patients with SQT1 cannot be recommended at this time. [[AICD]] implantation remains the mainstay of therapy in these patients. Pharmacotherapy may play an adjunctive role in reducing the risk of events in patients with an [[AICD]] as described below in the indications section.
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| Patients with Short QT Syndrome 1 (SQT1) have a mutation in [[KCNH2]] ([[HERG]]). Class IC and III antiarrhythmic drugs do not produce any significant QT interval prolongation <ref>{{cite journal | author=Gaita F, Giustetto C, Bianchi F, Schimpf R, Haissaguerre M, Calo L, Brugada R, Antzelevitch C, Borggrefe M, Wolpert C. | title=Short QT syndrome: pharmacological treatment | journal=J Am Coll Cardiol | year=2004 | pages=1494–1499 | volume=43 | issue=8 | pmid=15093889 | doi=10.1016/j.jacc.2004.02.034}}</ref><ref name="pmid15673388">{{cite journal | author = Wolpert C, Schimpf R, Giustetto C, Antzelevitch C, Cordeiro J, Dumaine R, Brugada R, Hong K, Bauersfeld U, Gaita F, Borggrefe M | title = Further insights into the effect of quinidine in short QT syndrome caused by a mutation in HERG | journal = [[Journal of Cardiovascular Electrophysiology]] | volume = 16 | issue = 1 | pages = 54–8 | year = 2005 | month = January | pmid = 15673388 | pmc = 1474841 | doi = 10.1046/j.1540-8167.2005.04470.x | url = http://onlinelibrary.wiley.com/resolve/openurl?genre=article&sid=nlm:pubmed&issn=1045-3873&date=2005&volume=16&issue=1&spage=54 | issn = | accessdate = 2012-09-03}}</ref> . Flecainide has not been shown to consistently reduce the inducibility of [[ventricular fibrillation]].<ref name="pmid15093889">{{cite journal | author = Gaita F, Giustetto C, Bianchi F, Schimpf R, Haissaguerre M, Calò L, Brugada R, Antzelevitch C, Borggrefe M, Wolpert C | title = Short QT syndrome: pharmacological treatment | journal = [[Journal of the American College of Cardiology]] | volume = 43 | issue = 8 | pages = 1494–9 | year = 2004 | month = April | pmid = 15093889 | doi = 10.1016/j.jacc.2004.02.034 | url = http://linkinghub.elsevier.com/retrieve/pii/S0735109704004437 | issn = | accessdate = 2012-09-03}}</ref> Although it does not prolong the [[QT interval]] in SQT1 patients, [[propafenone]] reduces the risk of recurrent [[atrial fibrillation]] in SQT1 patients.<ref> Bjerregaard P, Gussak I. Atrial fibrillation in the setting of familial short QT interval. Heart Rhythm 2004; 1: S165 (abstract).</ref>
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| Quinidine in contrast may be effective in patients with SQT1 in so far as it blocks both potassium channels (IKr, IKs, Ito, IKATP and IK1) and the inward sodium and calcium channels. In four out of four patients, [[Quinidine]] prolonged the [[QT interval]] from 263 +/- 12 msec to 362 +/-25 msec, most likely due to its effects on prolonging the [[action potential]] and by virtue of its action on the I<sub>K</sub> channels. Although [[Quinidine]] was successful in preventing the inducibility of [[ventricular fibrillation]] in 4 out of 4 patients, it is unclear if the prolongation of the [[QT interval]] by [[quinidine]] would reduce the risk of [[sudden cardiac death]].
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| Although pharmacotherapy can be used to suppress the occurrence of [[atrial fibrillation]] in patients with SQT1, [[AICD]] implantation is the mainstay of therapy, and pharmacotherapy to prevent sudden death should is only indicated if [[AICD]] implantation is not possible.
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| Among patients with SQT1, [[Qunidine ]]also:
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| *Prolongs the [[ST segment]] and [[T wave]] durations
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| *Restores the [[heart rate]] dependent variability in the [[QT interval]]
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| *Decreases repolarization dispersion
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| ====Indications for Pharmacologic Therapy====
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| The following are indications for pharmacologic therapy of SQTS<ref>Moreno-Reviriego S, Merino JL.Short QT Syndrome. An article from the E-Journal of the ESC Council for Cardiology Practice. Vol9 N°2, 17 Sep 2010 [http://www.escardio.org/communities/councils/ccp/e-journal/volume9/Pages/Short_Qt_Syndrome_Reviriego.aspx]</ref>:
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| * In children as an alternate to [[AICD]] implantation
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| * In patients with a contraindications [[AICD]] implantation
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| * In patients who decline [[AICD]] implantation
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| * In patients with appropriate [[AICD]] discharges to reduce the frequency of discharges
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| * In patients with [[atrial fibrillation]] to reduce the frequency of symptomatic episodes
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| ==References==
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| {{Reflist|2}}
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| {{Electrocardiography}} | | {{Electrocardiography}} |
