Accelerated Junctional Rhythm

Background

• Accelerated junctional rhythm (AJR) occurs when the rate of the AV junctional pacemaker exceeds that of the sinus node.
• This situation arises when there is increased automaticity in the AV node coupled with decreased automaticity in the sinus node.
• Causes include myocardial ischaemia, digoxin toxicity, cardiac surgery, myocarditis and beta-agonists (e.g. isoprenaline).
• The typical rate of an AJR is 60 – 130 bpm, in contrast to junctional escape rhythms which have a typical rate of 40 – 60 bpm.
• May be described as junctional tachycardia when > 100 bpm.
• Often referred to as non-paroxysmal junctional tachycardia or automatic junctional tachycardia to differentiate it from re-entrant junctional tachycardias such as AVNRT.

Accelerated Junctional Rhythm

ECG Features

• Ventricular rate usually 60 – 130 bpm.
• More rapid rates (> 200 bpm) may occur, particularly with beta-agonists / sympathomimetics.
• Retrograde P waves may be present and can appear before, during or after the QRS complex.
• Retrograde P waves are usually inverted in the inferior leads, upright in aVR and V1.
• QRS duration < 120ms unless pre-existing bundle branch block or rate-related aberrant conduction.
• AV dissociation may be present with the ventricular rate usually faster than the atrial rate.

Differential Diagnosis

Rapid AJR  may be difficult to distinguish from re-entrant junctional tachycardias such as AVNRT or AVRT.

• Irregularity of rhythm and heart-rate variability are suggestive of automatic junctional tachycardia.
• Automatic junctional tachycardia is typically non-responsive to vagal manoeuvres — there may be some transient slowing of the ventricular rate but reversion to sinus rhythm will not occur.

AJR with aberrant conduction may be difficult to distinguish from accelerated idioventricular rhythm.

• The presence of fusion or capture beats indicates a ventricular rather than junctional focus.

ECG Example

Accelerated junctional rhythm:

• Narrow complex tachycardia at 115 bpm.
• Retrograde P waves — inverted in II, III and aVF; upright in V1 and aVR.
• Short PR interval (< 120 ms) indicates a junctional rather than atrial focus.

Related Topics

• AV nodal re-entry tachycardia (AVNRT)
• Atrioventricular re-entry tachycardia (AVRT)
• Accelerated idioventricular rhythm (AIVR)

Further Reading

• ECG BASICS – Waves, Intervals, Segments and Clinical Interpretation
• ECG CLINICAL CASES – Your favourite ECG’s placed in clinical context with a challenging Q&A approach
• ECG and Cardiology Eponymous Syndromes – Cheats guide to eponymous emancipation
• ECG Reference Sites on the WEB – the best of the rest

Author Credits

References

• Surawicz B, Knilans TK. Chou’s Electrocardiography in Clinical Practice. 6th Edition. Saunders Elsevier 2008.
• Chan TC, Brady WJ, Harrigan RA, Ornato JP, Rosen P. ECG in Emergency Medicine and Acute Care. Elsevier Mosby 2005.
• Mattu A, Brady W. ECGs for the Emergency Physician 2, BMJ Books 2008.
• Wagner, GS. Marriott’s Practical Electrocardiography (11th edition), Lippincott Williams & Wilkins 2007.