Junctional tachycardia: Difference between revisions
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'''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. | '''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. | ||
Revision as of 14:46, 24 October 2012
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Synonyms and keywords: Accelerated junctional rhythm
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.
Pathophysiology
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.
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.
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.[1]
Causes
Differentiation of Junctional Tachycardia from other Tachycardias
- Sinus tachycardia:
- Atrioventricular nodal reentrant tachycardia: It can appear similar to atrioventricular nodal reentrant tachycardia.[3]
One form is junctional ectopic tachycardia.
Epidemiology and Demographics
Sex
Males and females are affected equally.
Diagnosis
Symptoms
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:
Physical Examination
Vitals
Pulse
The pulse is regular at a rate of >60 beats per minute
Neck
- Cannon a waves may be present if there is delayed atrial contraction against a closed tricuspid valve
Laboratory Studies
Based upon the patient's history and demographics, consideration should be given to checking the following:
- Digoxin levels
Electrocardiography
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
- The rate is >60 beats per minute
- The rate is generally regular
- The QRS complex is narrow
- 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.
- The p wave may be buried within the QRS complex and may not be discernable
- AV nodal reentry tachycardia (AVNRT) should be excluded.
EKG Examples
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.
Image obtained courtesy of Jason E. Roediger, CCT,CRAT
Holter / Cardiac Event Monitoring
A cardiac event monitor may be helpful in patients with transient symptoms or palpitations to exclude other rhythms such as ventricular tachycardia.
Electrophysiologic Studies
- There is normal conduction in the His bundle, and the His-ventricular interval is normal.
- Preceding each QRS, there should be a His bundle depolarization
- AV conduction is variable
- VA conduction is variable
Treatment
- Treatment consists of supportive care or correction of the underlying disorder that triggered the junctional automaticity.
- Treat symptomatic digitalis toxicity with atropine and digoxin immune Fab (Digibind)
Related Chapters
References
- ↑ 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.
- ↑ "Junctional Rhythm: Overview - eMedicine". Retrieved 2008-12-21.
- ↑ Srivathsan K, Gami AS, Barrett R, Monahan K, Packer DL, Asirvatham SJ (2008). "Differentiating atrioventricular nodal reentrant tachycardia from junctional tachycardia: novel application of the delta H-A interval". J. Cardiovasc. Electrophysiol. 19 (1): 1–6. doi:10.1111/j.1540-8167.2007.00961.x. PMID 17916156. Unknown parameter
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