Accelerated Junctional Rhythm (AJR)

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

Terminology

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 AJR 2
Accelerated Junctional Rhythm

ECG AVNRT QRSPT retrograde P
Re-entrant Junctional Rhythm (AVNRT)

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

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.

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.


ECG Examples
Example 1
Accelerated Junctional Rhythm (AJR) ECG 3

Junctional Tachycardia

  • 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

References

LITFL Further Reading

Advanced Reading

ECG LIBRARY 700

ECG LIBRARY

Electrocardiogram

Emergency Physician in Prehospital and Retrieval Medicine in Sydney, Australia. He has a passion for ECG interpretation and medical education | ECG Library |

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