Accelerated Junctional Rhythm Overview
Accelerated junctional rhythm (AJR) occurs when the rate of an 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 of Accelerated Junctional Rhythm
- Digoxin toxicity (= the classic cause of AJR)
- Beta-agonists, e.g. isoprenaline, adrenaline
- Myocardial ischaemia
- Cardiac surgery
Junctional rhythms are arbitrarily classified by their rate:
- Junctional Escape Rhythm: 40-60 bpm
- Accelerated Junctional Rhythm: 60-100 bpm
- Junctional Tachycardia: > 100 bpm
They may also be classified by aetiology:
- Automatic Junctional Rhythms (e.g. AJR) = Due to enhanced automaticity in AV nodal cells
- Re-entrant Junctional Rhythms (e.g. AVNRT) = Due to re-entrant loop involving AV node
ECG Features of AJR
- Narrow complex rhythm; QRS duration < 120ms (unless pre-existing bundle branch block or rate-related aberrant conduction).
- Ventricular rate usually 60 – 100 bpm.
- 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 (II, III, aVF), upright in aVR + V1.
- AV dissociation may be present with the ventricular rate usually greater than the atrial rate.
- There may be associated ECG features of digoxin effect or digoxin toxicity.
Differential Diagnosis of AJR
- 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.
NOTE: 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.
- 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.
- AV nodal re-entry tachycardia (AVNRT)
- Atrioventricular re-entry tachycardia (AVRT)
- Accelerated idioventricular rhythm (AIVR)
- Dr Smith’s ECG Blog – Accelerated Junctional Rhythm
- JJ Larkin’s ECG of the Week – Accelerated Junctional Rhythm
LITFL Further Reading
- ECG Library Basics – Waves, Intervals, Segments and Clinical Interpretation
- ECG A to Z by diagnosis – ECG interpretation in clinical context
- ECG Exigency and Cardiovascular Curveball – ECG Clinical Cases
- 100 ECG Quiz – Self-assessment tool for examination practice
- ECG Reference SITES and BOOKS – the best of the rest
- Brady WJ, Truwit JD. Critical Decisions in Emergency and Acute Care Electrocardiography
- Surawicz B, Knilans T. Chou’s Electrocardiography in Clinical Practice: Adult and Pediatric
- Wagner GS. Marriott’s Practical Electrocardiography 12e
- Chan TC. ECG in Emergency Medicine and Acute Care
- Rawshani A. Clinical ECG Interpretation
- Mattu A. ECG’s for the Emergency Physician
- Hampton JR. The ECG In Practice, 6e