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| Caption = Schematic representation of normal ECG trace ''([[sinus rhythm]]),'' with waves, segments, and intervals labeled. | | | 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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| MeshID = | | | MeshID = | |
| }} | | }} |
| {{SI}} | | {{Short QT syndrome}} |
| {{CMG}}; '''Associate Editor-In-Chief:''' {{CZ}} | | {{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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| ==Overview== | | ==[[Short_QT_syndrome_overview|Overview]]== |
| '''Short QT syndrome''' is a [[genetics|genetic]] disease of the electrical system of the [[heart]]. It consists of a constellation of signs and symptoms, consisting of a short [[QT interval]] on an [[EKG]] (≤ 300 [[millisecond|ms]]) that does not significantly change with heart rate, tall and peaked T waves, and a structurally normal heart. Short QT syndrome appears to be inherited in an [[autosomal dominant]] pattern, and a few affected families have been identified.
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| ==Historical Perspective== | | ==[[Short_QT_syndrome_historical_perspective|Historical Perspective]]== |
| The syndrome was first described by Dr. Prebe Bjerregaard MD, DMSc in 1999.
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| ===First Patient with Short QT Syndrome=== | | ==[[Short QT syndrome classification|Classification]]== |
| Shalon Hill, a 17 year old white female, underwent laparoscopic cholecystectomy at Anderson Hospital, Maryville, Illinois in 1999 which was complicated by atrial fibrillation with a rapid ventricular response (RVR) at 150-200 beats/min along with acute [[pulmonary edema]]<ref>http://www.shortqtsyndrome.org/short_qt_history.htm</ref>. The atrial fbrillation with RVR was treated with DC [[cardioversion]] and she was discharged to home in [[normal sinus rhythm]] on [[digoxin]]. The [[atrial fibrillation]] recurred 6 weeks later and she was found at that time to have a short [[QT interval]] of 225 mseconds which was treated with prophylactic therapy with [[propafenone]]. She then remained asymptomatic for 6 months and the [[propafenone]] was discontinued. However, the atrial fibrillation recurred 2 months after the propafenone was discontinued, and it was therefore resumed. She remained asymptomatic on propafenone, but an [[AICD]] was implanted given reports from around the world of [[sudden cardiac death]].
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| ===First Family with Short QT Syndrome=== | | ==[[Short QT syndrome pathophysiology|Pathophysiology]]== |
| The QT interval of her 21 year old brother was 240 msec, the QT interval of her 84 year old maternal grandfather was 240 msec, and the QT interval of her 51 year old mother was 230 msec. The EKG of here father was normal.
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| He brother had no history of [[palpitations]], [[dizziness]] or [[syncope]]. August 13, 2003, he underwent a programmed electrical stimulation study with induction of ventricular fibrillation followed by implantation of an implantable cardioverter defibrillator. During follow-up he admited to occasional palpitations and interrogation of the ICD shows few brief episodes of atrial fibrillation with fast ventricular response. He has so far not received any shocks.
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| Her mother is a 51 year old healthy white female with a QT interval of 230 ms and a history of 3 episodes of sustained palpitations and two of them documented as atrial fibrillation. On propafenone since April, 2003 she has been asymptomatic. She underwent programmed electrical stimulation study September 29, 2003 with induction of both atrial and ventricular fibrillation and received an implantable cardioverter defibrillator. She has so far not received any shocks.
| | ==[[Short QT syndrome causes|Causes]]== |
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| Her maternal grandfather was an 84 year old white male who had chronic [[atrial fibrillation]], [[coronary artery disease]] and [[hypertension]] who died following an embolic [[stroke]].
| | ==[[Short QT syndrome triggers|Triggers]]== |
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| ==Pathophysiology== | | ==[[Short QT syndrome differential diagnosis|Differentiating Short QT Syndrome from other Diseases]]== |
| The etiology of short QT syndrome is unclear at this time. A current [[hypothesis]] is 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=== | | ==[[Short QT syndrome epidemiology and demographics|Epidemiology and Demographics]]== |
| 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]].
| | ==[[Short QT syndrome screening|Screening]]== |
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| ==Causes== | | ==[[Short QT syndrome natural history, complications and prognosis|Natural History, Complications, Prognosis]]== |
| ===Common Causes===
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| *[[Hypercalcemia]]
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| *[[Digoxin]]
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| ===Causes in Alphabetical Order=== | | ==[[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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| * [[Digoxin]]
| | ==[[Treatment]]== |
| * [[Hypercalcaemia]]
| | [[Short QT syndrome AICD placement|AICD placement]] | [[Short QT syndrome medical therapy|Medical Therapy]] |
| * [[Lanatoside C]]
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| * [[Rufinamide]]
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| * [[Short QT syndrome type 1]]
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| ==Epidemiology and Demographics== | |
| Since the syndrome was first described in 2000, < 30 cases have been identified.
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| ==Natural History, Complications, Prognosis==
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| Short QT syndrome is associated with an increased risk of [[sudden cardiac death]], most likely due to [[ventricular fibrillation]].
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| ==Diagnosis==
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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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| Some individuals with short QT syndrome complain of frequent [[palpitations]] and may experience unexplained [[syncope]] ([[loss of consciousness]]).
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| ===Electrocardiogam===
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| The characteristic findings of short QT syndrome on [[EKG]] are a short QT interval, typically ≤ 300 ms, that doesn't significantly change with the heart rate. Tall, peaked T waves may also be noted. Individuals may also have an underlying [[atrium (anatomy)|atrial]] rhythm of [[atrial fibrillation]].
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| ===Electrophysiologic Studies===
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| In the electrophysiology lab, individuals with short QT syndrome are noted to have short refractory periods, both in the [[atrium (anatomy)|atria]] as well as in the [[Ventricle (heart)|ventricles]]. Also, [[ventricular fibrillation]] is frequently induced on [[programmed stimulation]].
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| ===Genetic Testing===
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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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| ==Treatment==
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| Currently, some individuals with short QT syndrome have had implantation of an [[implantable cardioverter-defibrillator]] (ICD) as a preventive action, although it has not been demonstrated that cardiac problems have occurred before deciding to implant an ICD.
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| A recent study has suggested the use of certain [[antiarrhythmic agents]], particularly [[quinidine]], may be of benefit in individuals with short QT syndrome due to their effects on prolonging the action potential and by their action on the I<sub>K</sub> channels.<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>
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| ==See also==
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| * [[Long QT syndrome]]
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| ==References==
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| {{Reflist|2}}
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| ==Additional resource==
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| *[http://ghr.nlm.nih.gov/condition=shortqtsyndrome?wf=1 Short QT syndrome]
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| {{Electrocardiography}} | | {{Electrocardiography}} |
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| [[it:Sindrome del QT breve]] | | [[it:Sindrome del QT breve]] |
| [[ru:Синдром короткого интервала QT]] | | [[ru:Синдром короткого интервала QT]] |
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| [[Category:Cardiology]] | | [[Category:Cardiology]] |
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| [[Category:Genetic disorders]] | | [[Category:Genetic disorders]] |
| [[Category:Syndromes]] | | [[Category:Syndromes]] |
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| {{WikiDoc Help Menu}} | | {{WikiDoc Help Menu}} |
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