Junctional Escape Rhythm

ECG features of Junctional Escape Rhythm
  • Junctional rhythm with a rate of 40-60 bpm
  • QRS complexes are typically narrow (< 120 ms)
  • No relationship between the QRS complexes and any preceding atrial activity (e.g. P-waves, flutter waves, fibrillatory waves)

Mechanism

Pacemaker cells are found at various sites throughout the conducting system, with each site capable of independently sustaining the heart rhythm. The rate of spontaneous depolarisation of pacemaker cells decreases down the conducting system:

  • SA node (60-100 bpm)
  • Atria (< 60 bpm)
  • AV node (40-60 bpm)
  • Ventricles (20-40 bpm)

Under normal conditions, subsidiary pacemakers are suppressed by the more rapid impulses from above (i.e. sinus rhythm). Junctional and ventricular escape rhythms arise when the rate of supraventricular impulses arriving at the AV node or ventricle is less than the intrinsic rate of the ectopic pacemaker.


Causes

Conditions leading to the emergence of a junctional or ventricular escape rhythm include:


ECG Examples
Example 1
regularised atrial fibrillation ECG

Atrial fibrillation with 3rd degree AV block and a junctional escape rhythm (“regularised AF”)

  • Coarse atrial fibrillation (irregular baseline with atrial complexes at rate > 400 bpm)
  • Regular narrow complex rhythm at 60 bpm
  • The combination of atrial fibrillation with a regular rhythm (“regularised AF”) indicates that none of the atrial impulses are conducted to the ventricles, i.e. complete heart block is present
  • The narrow complex rhythm is therefore a junctional escape rhythm
  • Regularised AF is characteristically seen as a consequence of digoxin toxicity

Example 2
Digoxin toxicity Regularised atrial fibrillation AF

Terminology of junctional rhythms
  • Junctional bradycardia = junctional rhythm at a rate of < 40 bpm
  • Junctional escape rhythm = junctional rhythm at a rate of 40-60 bpm
  • Accelerated junctional rhythm = junctional rhythm at 60-100 bpm
  • Junctional tachycardia = junctional rhythm at > 100 bpm


Advanced Reading

Online

Textbooks


LITFL Further 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 |

MBBS (UWA) CCPU (RCE, Biliary, DVT, E-FAST, AAA) Emergency Medicine Advanced Trainee in Melbourne, Australia. Special interests in diagnostic and procedural ultrasound, medical education, and ECG interpretation. Editor-in-chief of the LITFL ECG Library. Twitter: @rob_buttner

2 Comments

  1. I dont agree with the first example as atrial fibrillation
    Its more like atrial flutter with variable block

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