Junctional rhythm
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. Junctional rhythm can be classified into junction escape rhythm, accelerated junctional rhythm, junctional bradycardia, and junctional tachycardia. The junctional rhythm can be originated by many medications that affect the sinoatrial node and make the atrioventricular node an ectopic impulses foci. Many conditions as well causes junctional rhythm by creating new pacemaker instead of the sinoatrial node. In junctional rhythm, the heart beats rate are not controlled by the sinoatrial node. The new pacemaker in the junctional rhythm is the atrioventricular node. Common causes of junctional rhythm include 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, Chest trauma, Radiation therapy, Collagen vascular disease, Myocarditis, Clonidine, Reserpine, Adenosine, and Cimetidine. In the United States, the prevalence of junctional rhythm is 166 in 100,000 individuals with sinus node dysfunction. If left untreated, junctional rhythm can lead to syncope and other severe complications. Patients presenting with juncitonal rhythm disease should be asked properly for history of other cardiac conditions as heart failure and sick sinus syndrome. Symptoms of junctional rhythm can be non specific and includes syncope, dizziness, and faitgue. Physical examination findings of junctional rhythm include pulsating veins and canon a waves in case the right atrium contracting against a closed tricuspid valve. Electrocardiogram may show QRS complexes are narrow 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 rapid in which case the rhythm is referred to as a junctional tachycardia. Asymptomatic patients with only juncitonal rhythm and no other cardiac conditions do not require further management. The rhythm here is due to increased vagal tone only. Patients with sinus node dysfunction should be managed cautiously as the pulse originating from other foci keeps the heart rate. Patients with junctional rhythm due to digoxin toxicity are given atropine and digoxin specific antibody. In children, symptomatic patients can undergo percutaneous radiofrequency ablation. Pacemaker is indicated for patients with sick sinus syndrome and complete AV block.

# Classification
- Junctional rhythm can be classified according to the rate of the heart rate as the following:

## Junctional Rhythm
- The junctional rate is normal.

## Junction escape rhythm:
- The junctional rate is about 40-60 beats per minute.

## Accelerated junctional rhythm:
- The juncitonal rate can be accelerated (60-100 beats per minute).

## 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 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.
- This sinus rhythm indicates the atria normally contracts before the ventricles.

## Pathogenesis
- The junctional rhythm can be originated by many medications that affect the sinoatrial node and make the atrioventricular node an ectopic impulses foci. Many conditions as well causes junctional rhythm by creating new pacemaker instead of the sinoatrial node.
- In junctional rhythm, the heart beats rate are not controlled by the sinoatrial node. The new pacemaker in the junctional rhythm is the atrioventricular node.
- The atria contracts before the ventricles but from a different signal. The impulse contracting the atria comes from the ventricles not the normal impulse coming from the sinoatrial node.
- Junctional tacycardia:
Occurs when the atrioventricular node becomes the pacemaker and spreads impulse in a rapid pattern.
It takes place when the myocardial tissue is inflammed and ischemic as in patients undergo a heart surgery.
- Occurs when the atrioventricular node becomes the pacemaker and spreads impulse in a rapid pattern.
- It takes place when the myocardial tissue is inflammed and ischemic as in patients undergo a heart surgery.

# Causes
- Common causes of junctional rhythm include the following diseases and medications:
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
Chest trauma                                                           
Radiation therapy
Collagen vascular disease
Myocarditis
Clonidine
Reserpine
Adenosine
Cimetidine
Antiarrhythmics class I to IV
Lithium
Amitriptyline
Neuromuscular disorder
X-linked muscular dystrophy
Familial disorder
Vasovagal simulation (endotracheal suctioning)
Carotid sinus hypersensitivity
Opioids
Cannabinoids
Isoproterenol infusion
Hypothyroidism
Sleep apnea
Hypoxia
Intracranial hypertension
Hyperkalemia
Anorexia nervosa
Amyloidosis
Pericarditis
Rheumatic fever
Repair of congenital heart disease
Inherited channelopathy
- 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
- Chest trauma
- Radiation therapy
- Collagen vascular disease
- Myocarditis
- Clonidine
- Reserpine
- Adenosine
- Cimetidine
- Antiarrhythmics class I to IV
- Lithium
- Amitriptyline
- Neuromuscular disorder
- X-linked muscular dystrophy
- Familial disorder
- Vasovagal simulation (endotracheal suctioning)
- Carotid sinus hypersensitivity
- Opioids
- Cannabinoids
- Isoproterenol infusion
- Hypothyroidism
- Sleep apnea
- Hypoxia
- Intracranial hypertension
- Hyperkalemia
- Anorexia nervosa
- Amyloidosis
- Pericarditis
- Rheumatic fever
- Repair of congenital heart disease
- Inherited channelopathy

# Differentiating Junctional Rhythm from other diseases
- Junctional rhythm must be differentiated from other diseases that cause abnormal cardiac electrical conduction.

# Epidemiology and Demographics

## Prevalence
- In the United States, the prevalence of junctional rhythm is 166 in 100,000 individuals with sinus node dysfunction.

## Age
- The prevalence of junctional rhythm increases with age.

## Gender
- Men and women are affected equally by juntional rhythm.

# Natural History, Complications and Prognosis

## Natural History
- If left untreated, junctional rhythm can lead to syncope and other severe complications.

## Complications
- Complications of junctional rhythm include the following:
Syncope
Dizziness
Fatigue
- Syncope
- Dizziness
- Fatigue

## Prognosis
- Prognosis of junctional rhythm is good with the proper treatment.

# History and Symptoms

## History
- Patients presenting with juncitonal rhythm disease should be asked properly for history of other cardiac conditions.
- Other cardiac conditions can affect the presentation of the patients. These cardiac conditions include:
Heart failure
Sick sinus syndrome
- Heart failure
- Sick sinus syndrome

## Symptoms
- Patients with juncitonal rhythm disease can be asymptomatic.
- Symptoms of junctional rhythm can be non specific and includes the following:
Dizziness
Fatigue
Syncope
Palpitaions
- Dizziness
- Fatigue
- Syncope
- Palpitaions
- Symptoms vary according to the underlying cause of junctional rhythm as the following:
Heart failure:
Shortness of breath
Lower extremities edema
Valve dysfunction due to rheumatic fever:
Fever
Arthritis
Skin rash
- Heart failure:
Shortness of breath
Lower extremities edema
- Shortness of breath
- Lower extremities edema
- Valve dysfunction due to rheumatic fever:
Fever
Arthritis
Skin rash
- Fever
- Arthritis
- Skin rash

# Physical Examination
- Common physical examination findings of junctional rhythm include the following:
Pulsating veins
Canon a waves in case the right atrium contracting against a closed tricuspid valve
Regular heart rate in most of cases ranging from 40 to 60 beat per minute
- Pulsating veins
- Canon a waves in case the right atrium contracting against a closed tricuspid valve
- Regular heart rate in most of cases ranging from 40 to 60 beat per minute

# 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,  .

# Treatment

## Medical therapy
- The underlying cause of junctional rhythm should be defined first before attempting treatment.
- Asymptomatic patients with only juncitonal rhythm and no other cardiac conditions do not require further management. The rhythm here is due to increased vagal tone only.
- Patients with sinus node dysfunction should be managed cautiously as the pulse originating from other foci keeps the heart rate.
- Patients with junctional rhythm due to digoxin toxicity are given atropine and digoxin specific antibody.
- Patients who do not respond to the usual medical therapy can be administered phenytoin.

## Surgery
- In children, symptomatic patients can undergo percutaneous radiofrequency ablation. 
- Pacemaker:
Indicated for patients with sick sinus syndrome and complete AV block.
- Indicated for patients with sick sinus syndrome and complete AV block.

# Related Chapters
- Junctional bradycardia
- Junctional tachycardia
- Junctional escape beat