Junctional bradycardia: Difference between revisions
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{{CMG}} | {{CMG}} | ||
{{SK}} | {{SK}} Junctional escape; junctional escape rhythm | ||
==Overview== | ==Overview== | ||
Junctional bradycardia is a slow (40 to 60 beats per minute) narrow complex escape rhythm that originates in the [[atrioventricular node]] to compensate for slow or impaired conduction of pacemaker activity in the atrium. | Junctional bradycardia is a slow (40 to 60 beats per minute) narrow complex escape rhythm that originates in the [[atrioventricular node]] to compensate for slow or impaired conduction of pacemaker activity in the atrium. | ||
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==Causes== | ==Causes== | ||
*[[Acute MI]] | * [[Acute MI]] | ||
*[[Acute rheumatic fever]] | * [[Acute rheumatic fever]] | ||
*[[Antiarrhythmic agents]] | * [[Antiarrhythmic agents]] | ||
*[[Beta-blockers]] | * [[Beta-blockers]] | ||
*[[Calcium channel blockers]] | * [[Calcium channel blockers]] | ||
*[[Complete heart block]] | * [[Complete heart block]] | ||
*[[Conduction system disease]] | * [[Conduction system disease]] | ||
*[[Digitalis toxicity]] | * [[Digitalis toxicity]] | ||
*[[Diphtheria]] | * [[Diphtheria]] | ||
*Healthy response during sleep in patients with [[heightened vagal tone]] | * Healthy response during sleep in patients with [[heightened vagal tone]] | ||
*[[Heart surgery]] particularly [[valve replacement]] or surgery for [[congenital heart disease]] | * [[Heart surgery]] particularly [[valve replacement]] or surgery for [[congenital heart disease]] | ||
*[[Ischemic heart disease]] | * [[Ischemic heart disease]] | ||
*[[Lyme disease]] | * [[Lyme disease]] | ||
*[[NSTEMI]] | * [[NSTEMI]] | ||
*[[Sick sinus syndrome]] | * [[Sick sinus syndrome]] | ||
*[[Sinus arrest]] | * [[Sinus arrest]] | ||
*[[Sinus bradycardia]] | * [[Sinus bradycardia]] | ||
*[[STEMI]] particularly inferior MI involving the [[posterior descending artery]] causing ischemia of the [[AV node]] due to poor perfusion in the [[AV nodal artery]] | * [[STEMI]] particularly inferior MI involving the [[posterior descending artery]] causing ischemia of the [[AV node]] due to poor perfusion in the [[AV nodal artery]] | ||
==Epidemiology and Demographics== | ==Epidemiology and Demographics== | ||
===Age=== | ===Age=== | ||
Benign junctional rhythms are common during sleep in both children and athletic young adults. | Benign junctional rhythms are common during sleep in both children and athletic young adults. | ||
===gender=== | |||
Males and females are affected equally. | |||
==Natural History, Complications, Prognosis== | ==Natural History, Complications, Prognosis== | ||
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===Symptoms=== | ===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: | 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: | ||
*[[Dyspnea]] | * [[Dyspnea]] | ||
*[[Fatigue]] | * [[Fatigue]] | ||
*[[Lightheadedness]] | * [[Lightheadedness]] | ||
*[[Palpitations]] | * [[Palpitations]] | ||
*[[Presyncope]] | * [[Presyncope]] | ||
*[[Reduced exercise tolerance]] | * [[Reduced exercise tolerance]] | ||
*[[Syncope]] | * [[Syncope]] | ||
===Physical Examination=== | ===Physical Examination=== | ||
====Vitals==== | ====Vitals==== | ||
=====Pulse===== | =====Pulse===== | ||
The pulse is regular at a rate of 40 to 60 beats per minute | The [[pulse]] is regular at a rate of 40 to 60 beats per minute. | ||
====Neck==== | ====Neck==== | ||
*[[Cannon a waves]] may be present if there is delayed atrial contraction against a closed [[tricuspid valve]] | * [[Cannon a waves]] may be present if there is delayed atrial contraction against a closed [[tricuspid valve]] | ||
===Laboratory | ===Laboratory Findings=== | ||
Based upon the patient's history and demographics, consideration should be given to checking the following: | Based upon the patient's history and demographics, consideration should be given to checking the following: | ||
*[[Digoxin]] levels | * [[Digoxin]] levels | ||
*[[Lyme titers]] in patients where the disease is endemic | * [[Lyme titers]] in patients where the disease is endemic | ||
===Electrocardiography=== | ===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 bradycardia should be ascertained such as: | 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 bradycardia should be ascertained such as: | ||
*[[AV dissociation]] | * [[AV dissociation]] | ||
*[[Complete heart block]] | * [[Complete heart block]] | ||
*[[Digitalis toxicity]] | * [[Digitalis toxicity]] | ||
*[[Sinus arrest]] | * [[Sinus arrest]] | ||
*[[Sinus bradycardia]] | * [[Sinus bradycardia]] | ||
*[[ST elevation MI]] | * [[ST elevation MI]] | ||
*The rate is 40-60 beats per minute | * The rate is 40-60 beats per minute. | ||
*The rate is generally regular | * The rate is generally regular. | ||
*The [[QRS]] complex is narrow | * 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. | * [[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 | * The [[p wave]] may be buried within the [[QRS]] complex and may not be discernable. | ||
*A slow [[AV nodal reentry tachycardia]] ([[AVNRT]]) should be excluded. | * A slow [[AV nodal reentry tachycardia]] ([[AVNRT]]) should be excluded. | ||
===EKG Examples=== | ===EKG Examples=== | ||
The EKG below shows a nodal escape rhythm. Note the lack of P or [[P' wave]]s. Often the P' wave is hidden in the QRS as the nodal escape conducts down to the ventricle and up to the atrium in a fashion such that the QRS and P' wave occur simultaneously. | The EKG below shows a nodal escape rhythm. Note the lack of P or [[P' wave]]s. Often the P' wave is hidden in the QRS as the nodal escape conducts down to the ventricle and up to the atrium in a fashion such that the QRS and P' wave occur simultaneously. | ||
[[File:Nodal escape rhythm1.jpg|center|500px]] | [[File:Nodal escape rhythm1.jpg|center|500px]] | ||
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Example of junctional escape rhythm / junctional bradycardia on telemetry: | Example of junctional escape rhythm / junctional bradycardia on telemetry: | ||
{{#ev:youtube|S2xnOJfZOPI}} | {{#ev:youtube|S2xnOJfZOPI}} | ||
| Line 95: | Line 99: | ||
===Electrophysiologic Studies=== | ===Electrophysiologic Studies=== | ||
*There is normal conduction in the [[His bundle]], and the His-ventricular interval is normal. | * 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 | * Preceding each [[QRS]], there should be a [[His bundle]] depolarization | ||
*AV conduction is variable | * AV conduction is variable | ||
*VA conduction is variable | * VA conduction is variable | ||
==Treatment== | ==Treatment== | ||
===Acute Management=== | ===Acute Management=== | ||
*Avoid drugs that suppress the [[AV node]] as the junctional bradycardia may be the patient's only escape rhythm | * Avoid drugs that suppress the [[AV node]] as the junctional bradycardia may be the patient's only escape rhythm | ||
*Treat symptomatic [[digitalis toxicity]] with [[atropine]] and [[digoxin immune Fab]] ([[Digibind]]) | * Treat symptomatic [[digitalis toxicity]] with [[atropine]] and [[digoxin immune Fab]] ([[Digibind]]) | ||
===Asymptomatic Patients=== | ===Asymptomatic Patients=== | ||
*Among healthy patients with heightened vagal tone, no treatment is neccessary | *Among healthy patients with heightened vagal tone, no treatment is neccessary | ||
===Symptomatic Patients=== | ===Symptomatic Patients=== | ||
*Permanent pacemaker placement in indicated in symptomatic patients with: | * Permanent pacemaker placement in indicated in symptomatic patients with: | ||
:*[[Complete heart block]] | :* [[Complete heart block]] | ||
:*High grade [[AV block]] | :* High grade [[AV block]] | ||
:*[[Sick sinus syndrome]] | :* [[Sick sinus syndrome]] | ||
==Related Chapters== | ==Related Chapters== | ||
*[[Junctional rhythm]] | * [[Junctional rhythm]] | ||
*[[Junctional tachycardia]] | * [[Junctional tachycardia]] | ||
==References== | ==References== | ||
Revision as of 16:52, 19 October 2012
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Synonyms and keywords: Junctional escape; junctional escape rhythm
Overview
Junctional bradycardia is a slow (40 to 60 beats per minute) narrow complex escape rhythm that originates in the atrioventricular node to compensate for slow or impaired conduction of pacemaker activity in the atrium.
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 rate below 60 beats per minute (junctional bradycardia) as the electrical impulses once they are generated are conducted with normal velocity down the usual pathways. Retrograde P waves (i.e. upside down) P waves due to retrograde or backward conduction may or may not be present.
Causes
- Acute MI
- Acute rheumatic fever
- Antiarrhythmic agents
- Beta-blockers
- Calcium channel blockers
- Complete heart block
- Conduction system disease
- Digitalis toxicity
- Diphtheria
- Healthy response during sleep in patients with heightened vagal tone
- Heart surgery particularly valve replacement or surgery for congenital heart disease
- Ischemic heart disease
- Lyme disease
- NSTEMI
- Sick sinus syndrome
- Sinus arrest
- Sinus bradycardia
- STEMI particularly inferior MI involving the posterior descending artery causing ischemia of the AV node due to poor perfusion in the AV nodal artery
Epidemiology and Demographics
Age
Benign junctional rhythms are common during sleep in both children and athletic young adults.
gender
Males and females are affected equally.
Natural History, Complications, Prognosis
The natural history and prognosis of the disease depends upon the underlying cause that triggered the junctional escape rhythm. A junctional escape rhythm during sleep is benign in children and young adults.
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 40 to 60 beats per minute.
Neck
- Cannon a waves may be present if there is delayed atrial contraction against a closed tricuspid valve
Laboratory Findings
Based upon the patient's history and demographics, consideration should be given to checking the following:
- Digoxin levels
- Lyme titers in patients where the disease is endemic
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 bradycardia should be ascertained such as:
- AV dissociation
- Complete heart block
- Digitalis toxicity
- Sinus arrest
- Sinus bradycardia
- ST elevation MI
- The rate is 40-60 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.
- A slow AV nodal reentry tachycardia (AVNRT) should be excluded.
EKG Examples
The EKG below shows a nodal escape rhythm. Note the lack of P or P' waves. Often the P' wave is hidden in the QRS as the nodal escape conducts down to the ventricle and up to the atrium in a fashion such that the QRS and P' wave occur simultaneously.
Copyleft images obtained courtesy of ECGpedia, http://en.ecgpedia.org/index.php?title=Special:NewFiles&offset=&limit=500.
Example of junctional escape rhythm / junctional bradycardia on telemetry:
{{#ev:youtube|S2xnOJfZOPI}}
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
Acute Management
- Avoid drugs that suppress the AV node as the junctional bradycardia may be the patient's only escape rhythm
- Treat symptomatic digitalis toxicity with atropine and digoxin immune Fab (Digibind)
Asymptomatic Patients
- Among healthy patients with heightened vagal tone, no treatment is neccessary
Symptomatic Patients
- Permanent pacemaker placement in indicated in symptomatic patients with:
- Complete heart block
- High grade AV block
- Sick sinus syndrome