Junctional bradycardia

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mugilan Poongkunran M.B.B.S [2]

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 or an AV junctional escape is a delayed heartbeat originating from an ectopic focus somewhere in the AV junction to compensate for an SA node that is no longer handling the pacemaking activity.

Junctional bradycardia occurs when the rate of depolarization of the SA node falls below the rate of the AV node or when the electrical impulses from the SA node fail to reach the AV node because of SA or AV block. SA node fibrosis and inferior wall myocardial infarction causing sinus arrest may cause the AV node to become the dominant pacemaker of the heart.

Junctional bradycardia or junctional escape rhythm need to be differentiated from other bradycardia conditions which has the bundle of His or the ventricles as their pacemaker compensating for the failed SA node.

Junctional bradycardia is fairly uncommon. It can occur in any age group, however it is more likely to be observed in elderly people with underlying heart disease.

Junctional bradycardia mostly results due to failure of impulse transmission from SA node. Its severity of symptoms depends on the underlying cause.

Junctional bradycardia symptoms mostly are due to decrease cardiac output and may present with sometimes with loss of consciousness and syncope.

Complete physical examination help determine any heart defects as a cause for junctional bradycardia and assess the severity of the condition.

Junctional bradycardia patients may have no definite cause or may be the result of various other problems. If junctional bradycardia patients present with symptoms, a generalized approach is done to find the precipitating factors.

Junctional bradycardia or AV junction rhythm is usually caused by the absence of the electrical impulse from the SA node. This usually appears on an EKG with a normal QRS complex accompanied with an inverted P wave either before, during, or after the QRS complex.

Treatment of junctional bradycardia depends on the severity of presentation. Atropine can be used to manage symptomatic patients.

Junctional bradycardia patients should be placed on pacemaker if there is complete AV block or sick sinus syndrome.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mugilan Poongkunran M.B.B.S [2]

Junctional bradycardia or an AV junctional escape is a delayed heartbeat originating from an ectopic focus somewhere in the AV junction to compensate for an SA node that is no longer handling the pacemaking activity.

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.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mugilan Poongkunran M.B.B.S [2]

Junctional bradycardia occurs when the rate of depolarization of the SA node falls below the rate of the AV node or when the electrical impulses from the SA node fail to reach the AV node because of SA or AV block. SA node fibrosis and inferior wall myocardial infarction causing sinus arrest may cause the AV node to become the dominant pacemaker of the heart.

Life-threatening causes include conditions which may result in death or permanent disability within 24 hours if left untreated.

• Acute coronary syndrome
• Acute hyperkalemic renal failure
• Diabetic ketoacidosis
• Myocardial rupture
• NSTEMI
• Organophosphate poisoning
• Parathion poisoning
• Poisonous spider bites
• Severe brain injury
• STEMI

• Acetylcholine
• Acute rheumatic fever
• Amiodarone
• Antiarrhythmic agents
• Beta-blockers
• Calcium channel blockers
• Cardiac catheterization
• Digitalis toxicity
• Dilated cardiomyopathy
• Diltiazem
• Hyperkalemia
• Hypermagnesemia
• Hypertensive heart disease
• Ischemic heart disease
• Methylprednisolone
• Phenytoin
• Sick sinus syndrome
• Sinus arrest
• Sinus bradycardia
• STEMI
• Verapamil

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mugilan Poongkunran M.B.B.S [2]

Junctional bradycardia or junctional escape rhythm need to be differentiated from other bradycardia conditions which has the bundle of His or the ventricles as their pacemaker compensating for the failed SA node.

• Complete heart block : In complete or third degree heart block there is sinus node activity but failure of conduction through the AV node. There are P waves dissociated from the ventricular complexes with a rate faster than the ventricular rate that differentiates complete heart block from junctional escape beat where there is absence of P waves.
• Idioventricular rhythm : An ventricular escape beat is a form of cardiac arrhythmia, in this case known as an ectopic beat. If there are only one or two ectopic beats, they are considered escape beats. If this causes a semi-normal rhythm to arise it is considered an idioventricular rhythm. A wide QRS because of ventricular origin of the idioventricular rhythm differentiate it from junctional bradycardia where the QRS is narrow.
• Premature ventricular contraction : An absence of P wave activity, associated with a widened QRS complex resembles a PVC and occuring after a pause of variable duration is characteristic of PVCs.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mugilan Poongkunran M.B.B.S [2]

Junctional bradycardia is fairly uncommon. It can occur in any age group, however it is more likely to be observed in elderly people with underlying heart disease.

Junctional bradycardia occurs in normal children and adults, particularly during sleep when rates may transiently drop as low as of 30 beats per minute and pauses of up to 2 seconds are not uncommon. Benign junctional rhythms are common in both children and athletic young adults.

Males and females are affected equally.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mugilan Poongkunran M.B.B.S [2]

Junctional bradycardia mostly results due to failure of impulse transmission from SA node. Its severity of symptoms depends on the underlying cause.

• 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.

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