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| | {{Junctional tachycardia}} |
| {{SI}} | | {{SI}} |
| {{CMG}} | | {{CMG}} |
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| {{SK}} Accelerated junctional rhythm | | {{SK}} Accelerated junctional rhythm; focal junctional tachycardia; automatic junctional tachycardia; His-bundle tachycardia; ectopic junctional tachycardia; junctional ectopic rhythm. |
| ==Overview== | | ==[[Junctional tachycardia overview|Overview]]== |
| '''Junctional tachycardia''' is a narrow complex [[supraventricular tachycardia]] characterized by electrical impulse generation from the [[AV node]] that is independent of or dissociated from that of the [[sinoatrial node]] ([[SA node]]) at a rate > 60 beats per minute.
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| ==Pathophysiology== | | ==[[Junctional tachycardia historical perspective|Historical Perspective]]== |
| Normally, the [[atrioventricular node]] ([[AVN]]) can generate an escape rhythm of 40-60 beats per minute in case the [[sinoatrial node]] ([[SA node]]) or atrial pacemakers fail ([[sinus arrest]]) or slow ([[sinus bradycardia]]) or if there is [[complete heart block]]. This [[junctional escape rhythm]] generates a normal, narrow [[QRS complex]] rhythm at a rte below 60 beats per minute ([[junctional bradycardia]]) as the electrical impulses once they are generated are conducted with normal velocity down the His-Purkinje system. [[Retrograde P waves]] (i.e. upside down) [[P waves]] due to retrograde or backward conduction may or may not be present in [[junctional bradycardia]].
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| In contrast to a [[junctional escape rhythm]] or [[junctional bradycardia]] at a rate of 40-60 beats per minute, junctional tachycardia is faster, at a rate > 60 beats per minute. Junctional tachycardia generates a normal, narrow [[QRS complex]] rhythm as the electrical impulses are conducted with normal velocity down the His-Purkinje system. [[Retrograde P waves]] (i.e. upside down) [[P waves]] due to retrograde or backward conduction may or may not be present.
| | ==[[Junctional tachycardia classification|Classification]]== |
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| The cause of the more rapid firing of the atrioventricular node is thought to be due to enhanced automaticity as a result of abnormal Ca metabolism in the [[sarcoplastic reticulum]].<ref>Kim D, Shinohara T, Joung B, Maruyama M, Choi EK, On YK. Calcium dynamics and the mechanisms of atrioventricular junctional rhythm. J Am Coll Cardiol. Aug 31 2010;56(10):805-12.</ref>
| | ==[[Junctional tachycardia pathophysiology|Pathophysiology]]== |
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| ==Causes== | | ==[[Junctional tachycardia causes|Causes]]== |
| *[[Acute MI]]
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| *[[Digitalis]] toxicity.<ref name="urlJunctional Rhythm: Overview - eMedicine">{{cite web |url=http://emedicine.medscape.com/article/155146-overview |title=Junctional Rhythm: Overview - eMedicine |format= |work= |accessdate=2008-12-21}}</ref>
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| *[[Heart surgery]]
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| *[[Isoproterenol infusion]]
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| *[[NSTEMI]]
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| *[[STEMI]]
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| ==Differentiation of Junctional Tachycardia from other Tachycardias== | | ==[[Junctional tachycardia differential diagnosis|Differentiating Junctional tachycardia from other Diseases]]== |
| *[[Sinus tachycardia]]:
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| *[[Atrioventricular nodal reentrant tachycardia]]: It can appear similar to [[atrioventricular nodal reentrant tachycardia]].<ref name="pmid17916156">{{cite journal |author=Srivathsan K, Gami AS, Barrett R, Monahan K, Packer DL, Asirvatham SJ |title=Differentiating atrioventricular nodal reentrant tachycardia from junctional tachycardia: novel application of the delta H-A interval |journal=J. Cardiovasc. Electrophysiol. |volume=19 |issue=1 |pages=1–6 |year=2008 |month=January |pmid=17916156 |doi=10.1111/j.1540-8167.2007.00961.x |url=http://www3.interscience.wiley.com/resolve/openurl?genre=article&sid=nlm:pubmed&issn=1045-3873&date=2008&volume=19&issue=1&spage=1}}</ref>
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| One form is [[junctional ectopic tachycardia]].
| | ==[[Junctional tachycardia epidemiology and demographics|Epidemiology and Demographics]]== |
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| ==Epidemiology and Demographics== | | ==[[Junctional tachycardia risk factors|Risk Factors]]== |
| ===Sex=== | | |
| Males and females are affected equally.
| | ==[[Junctional tachycardia natural history, complications and prognosis|Natural History, Complications and Prognosis]]== |
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| ==Diagnosis== | | ==Diagnosis== |
| ===Symptoms===
| | [[Junctional tachycardia history and symptoms| History and Symptoms]] | [[Junctional tachycardia physical examination | Physical Examination]] | [[Junctional tachycardia laboratory findings|Laboratory Findings]] | [[Junctional tachycardia electrocardiogram|Electrocardiogram]] | [[Junctional tachycardia other imaging findings|Other Imaging Findings]] | [[Junctional tachycardia other diagnostic studies|Other Diagnostic Studies]] |
| Symptoms are more likely if the atrial rate is faster than the junctional rate (if [[AV dissociation]] or [[complete heart block]] is present) as compared with the scenario whereby the junctional rate is faster than the atrial rate. The following symptoms may be present:
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| *[[Dyspnea]]
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| *[[Fatigue]]
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| *[[Lightheadedness]]
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| *[[Palpitations]]
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| *[[Presyncope]]
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| *[[Reduced exercise tolerance]]
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| *[[Syncope]]
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| ===Physical Examination===
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| ====Vitals====
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| =====Pulse=====
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| The pulse is regular at a rate of >60 beats per minute
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| ====Neck====
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| *[[Cannon a waves]] may be present if there is delayed atrial contraction against a closed [[tricuspid valve]]
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| ===Laboratory Studies===
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| Based upon the patient's history and demographics, consideration should be given to checking the following:
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| *[[Digoxin]] levels
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| ===Electrocardiography===
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| A 12 lead EKG should be obtained to evaluate the rhythm. In so far as it may alter treatment, any co-existing rhythm disturbance that may have precipitated junctional tachycardia should be ascertained such as
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| *[[Digitalis toxicity]].
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| *[[ST elevation MI]]
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| *The rate is >60 beats per minute
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| *The rate is generally regular
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| *The [[QRS]] complex is narrow
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| *[[Retrograde p waves]] may be present due to retrograde conduction from the AV node. The p waves will be inverted in leads II and III.
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| *The [[p wave]] may be buried within the [[QRS]] complex and may not be discernable
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| *[[AV nodal reentry tachycardia]] ([[AVNRT]]) should be excluded.
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| ===EKG Examples===
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| Shown below is an EKG depicting junctional tachycardia (rate about 115/min), dissociated from a slightly slower [[sinus tachycardia]] (rate about 107/min) producing one form of double tachycardia; pairs of ventricular capture (C) beats (5th, 6th, 19th, and 20th beats); see laddergram.
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| [[File:Junctional tachycardia.png|center|600px]] | |
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| Image obtained courtesy of Jason E. Roediger, CCT,CRAT
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| ----
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| ===Holter / Cardiac Event Monitoring===
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| A cardiac event monitor may be helpful in patients with transient symptoms or [[palpitations]] to exclude other rhythms such as [[ventricular tachycardia]].
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| ===Electrophysiologic Studies===
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| *There is normal conduction in the [[His bundle]], and the His-ventricular interval is normal.
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| *Preceding each [[QRS]], there should be a [[His bundle]] depolarization
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| *AV conduction is variable
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| *VA conduction is variable
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| ==Treatment== | | ==Treatment== |
| *Treatment consists of supportive care or correction of the underlying disorder that triggered the junctional automaticity.
| | [[Junctional tachycardia medical therapy|Medical Therapy]] | [[Junctional tachycardia surgery|Surgery]] | [[Junctional tachycardia primary prevention|Primary Prevention]] |[[Junctional tachycardia secondary prevention|Secondary Prevention]] | [[Junctional tachycardia cost-effectiveness of therapy|Cost-Effectiveness of Therapy]] |[[Junctional tachycardia future or investigational therapies|Future or Investigational Therapies]] |
| *Treat symptomatic [[digitalis toxicity]] with [[atropine]] and [[digoxin immune Fab]] ([[Digibind]])
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| ==Related Chapters== | | ==Case Studies== |
| * [[Junctional rhythm]]
| | [[Junctional tachycardia case study one|Case#1]]] |
| * [[Junctional bradycardia]]
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| ==References== | | ==References== |
| {{reflist|2}} | | {{reflist|2}} |
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| {{Heart diseases}}
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| [[Category:Cardiac dysrhythmia]] | | [[Category:Up-To-Date]] |
| | [[Category:Arrhythmia]] |
| [[Category:Cardiology]] | | [[Category:Cardiology]] |
| [[Category:Electrophysiology]] | | [[Category:Electrophysiology]] |
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