Junctional rhythm: Difference between revisions
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=== Physiology === | === Physiology === | ||
* The sinoatrial node in the heart is the pacemaker that determine the rate of the heart beats. The electrical impulse starts from the sinoatrial node then travels through the atria. It continues through the bundle of his, Purkinje fibers, and the ventricles ending one heart beat.<ref>[http://www.merriam-webster.com/medical/junctional%20rhythm Merriam-Webster dictionary > Junctional rhythm] Retrieved September 2010</ref> | * The sinoatrial node in the heart is the pacemaker that determine the rate of the heart beats. The electrical impulse starts from the sinoatrial node then travels through the atria. It continues through the bundle of his, Purkinje fibers, and the ventricles ending one heart beat.<ref>[http://www.merriam-webster.com/medical/junctional%20rhythm Merriam-Webster dictionary > Junctional rhythm] Retrieved September 2010</ref><ref name="pmid20797495">{{cite journal| author=Kim D, Shinohara T, Joung B, Maruyama M, Choi EK, On YK | display-authors=etal| title=Calcium dynamics and the mechanisms of atrioventricular junctional rhythm. | journal=J Am Coll Cardiol | year= 2010 | volume= 56 | issue= 10 | pages= 805-12 | pmid=20797495 | doi=10.1016/j.jacc.2010.03.070 | pmc=3050609 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=20797495 }}</ref> | ||
*This sinus rhythm indicates the atria normally contracts before the ventricles. | |||
* | * | ||
=== Pathogenesis === | |||
In junctional rhythm, however, the sinoatrial node does not control the heart's rhythm - this can happen in the case of a block in conduction somewhere along the pathway described above. When this happens, the heart's [[atrioventricular node]] takes over as the pacemaker.<ref> eMedicine:"Junctional Rhythms" http://www.emedicine.com/MED/topic1212.htm </ref>. In the case of a junctional rhythm, the atria will actually still contract before the ventricles; however, this does not happen by the normal pathway and instead is due to retrograde conduction (conduction comes from the ventricles or from the AV node into and through the atria).<ref> medical dictionary http://medical-dictionary.thefreedictionary.com/retrograde+conduction</ref>. | In junctional rhythm, however, the sinoatrial node does not control the heart's rhythm - this can happen in the case of a block in conduction somewhere along the pathway described above. When this happens, the heart's [[atrioventricular node]] takes over as the pacemaker.<ref> eMedicine:"Junctional Rhythms" http://www.emedicine.com/MED/topic1212.htm </ref>. In the case of a junctional rhythm, the atria will actually still contract before the ventricles; however, this does not happen by the normal pathway and instead is due to retrograde conduction (conduction comes from the ventricles or from the AV node into and through the atria).<ref> medical dictionary http://medical-dictionary.thefreedictionary.com/retrograde+conduction</ref>. | ||
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
See also: Junctional bradycardia for slow junctional rhythms, and junctional tachycardia for fast jucntional rhythms
Overview
Junctional rhythm describes an abnormal heart rhythm resulting from impulses coming from a locus of tissue in the area of the atrioventricular node, the "junction" between atria and ventricles.
Classification
Junctional Bradycardia
- The junctional rate may be slow (40-60 beats per minute) in which case the rhythm is referred to as junctional bradycardia
Junctional Rhythm
- The junctional rate is normal
Junctional Tachycardia
- The junctional rate may be rapid in which case the rhythm is referred to as a junctional tachycardia
Pathophysiology
Physiology
- The sinoatrial node in the heart is the pacemaker that determine the rate of the heart beats. The electrical impulse starts from the sinoatrial node then travels through the atria. It continues through the bundle of his, Purkinje fibers, and the ventricles ending one heart beat.[1][2]
- This sinus rhythm indicates the atria normally contracts before the ventricles.
Pathogenesis
In junctional rhythm, however, the sinoatrial node does not control the heart's rhythm - this can happen in the case of a block in conduction somewhere along the pathway described above. When this happens, the heart's atrioventricular node takes over as the pacemaker.[3]. In the case of a junctional rhythm, the atria will actually still contract before the ventricles; however, this does not happen by the normal pathway and instead is due to retrograde conduction (conduction comes from the ventricles or from the AV node into and through the atria).[4].
Causes
Junctional bradycardia
- 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
Junctional tachycardia
Diagnosis
Electrocardiogram
- The QRS complexes are narrow in so far as conduction down the His bundle is normal
- The junctional rate may be slow (40-60 beats per minute) in which case the rhythm is referred to as junctional bradycardia
- The junctional rate may be normal as shown in the tracing below
- The junctional rate may be rapid in which case the rhythm is referred to as a junctional tachycardia
- There is dissociation of the narrow complex QRS from an upright atrial p wave or the p wave is missing, or the p wave is retrograde (a retrograde p wave) due to retrograde conduction from the AV node back into the atrium.
EKG Examples
Shown below is an EKG depicting AV dissociation with variable timing of the p wave in relation to the QRS. A narrow complex junctional escape rhythm at 75 beats per minute is present.
Shown below is an EKG with a a regular rhythm at a rate of about 43/minute. There are no P waves to be seen and the QRS duration is about 80 ms. This is a nodal rhythm.
Copyleft images obtained courtesy of ECGpedia, http://en.ecgpedia.org.
Related Chapters
References
- ↑ Merriam-Webster dictionary > Junctional rhythm Retrieved September 2010
- ↑ Kim D, Shinohara T, Joung B, Maruyama M, Choi EK, On YK; et al. (2010). "Calcium dynamics and the mechanisms of atrioventricular junctional rhythm". J Am Coll Cardiol. 56 (10): 805–12. doi:10.1016/j.jacc.2010.03.070. PMC 3050609. PMID 20797495.
- ↑ eMedicine:"Junctional Rhythms" http://www.emedicine.com/MED/topic1212.htm
- ↑ medical dictionary http://medical-dictionary.thefreedictionary.com/retrograde+conduction
- ↑ "Junctional Rhythm: Overview - eMedicine". Retrieved 2008-12-21.