Arrhythmias, Junctional Rhythm

Basics

Description

Normally, heart beat is initiated by the sinus node (ie, sinus rhythm).
When it originates from the atrioventricular junction, it is called a junctional rhythm.
A rhythm that is <100 bpm is usually considered an escape rhythm, as during sinus bradycardia. If it is faster, it is called junctional tachycardia.

Epidemiology

Depends on patient population, and can be seen in all ages.

Risk Factors

None specific

Etiology

Idiopathic
Junctional ectopic tachycardia (JET) is a rapid arrhythmia that can be life-threatening, seen in youth after congenital heart disease operations with β-adrenergic stimulation.
Seen in older individuals in concert with acute MI (especially inferior with enhanced vagal tone) and as a manifestation of drug toxicity
Catecholamine stimulation

Diagnosis

Signs and symptoms:

Asymptomatic
Palpitations
Dyspnea
Heart failure (if incessant, causing "tachycardia-associated cardiomyopathy")

Tests

EKG shows narrow QRS tachycardia without discernible P waves. If there is retrograde conduction to the atria, a P wave can be seen following the QRS.
For the specific arrhythmia JET, there is often atrioventricular (AV) dissociation because junctional rate is significantly greater than atrial rate.

Lab

Only to assess drug levels if patient is thought to have toxicity

Differential Diagnosis

AV nodal reentry
AV reentry
Permanent form of junctional reciprocating tachycardia, which virtually always has a deeply inverted P wave in ECG leads II, III, and aVF with the RP interval longer than the PR interval; this may result in a tachycardia-induced cardiomyopathy
Ectopic atrial tachycardia
Sinus tachycardia
Atrial flutter

Treatment

Medication

Drugs not often effective
Sometimes substrate may be abatable, but risk for damage to normal AV conduction may be significant (AV node or His bundle)
For postoperative JET, β-blockers, verapamil, procainamide (with hypothermia), and amiodarone have been used with varying success.
For accelerated idioventricular rhythm in acute MI, administration of antiarrhythmic drugs may suppress this escape pacemaker and lead to asystole:In this setting, observation is indicated because the junctional rhythm usually resolves.Especially common in inferior MI.

Additional Treatment

General Measures

Remove precipitating cause (toxic drug, catecholamine stimulation).

Surgery

Usually a pacemaker is not needed.

In-Patient Considerations

Admission Criteria

Usually arrhythmia is 1st recognized in inpatients. Discharge is determined by resolution of other medical problems.

Ongoing Care

Follow-Up Recommendations

Patient Monitoring

Usually arrhythmia is transient and corrects during hospitalization for underlying cause.

Patient Education

Depending on presentation and underlying disease:

If observed in healthy athlete with high vagal tone, no intervention is necessary.
Rarely, electrophysiologic study may be considered to identify substrate and perhaps cure with ablation (ie, AV nodal reentry, AV reentry, ectopic atrial tachycardia).

Prognosis

Depends on underlying diseases

Additional Reading

1Hamdan MH, Scheinman MM. Role of invasive EP testing in the evaluation and management of junctional tachycardia. Cardiol Electrophysiol Rev. 1997;4:439-442.2Walsh EP, Saul P, Sholler GF. Evaluation of a staged treatment protocol for rapid automatic junctional tachycardia after operation for congenital heart disease. J Am Coll Cardiol. 1997;29:1046-1053. [View Abstract]