• Junctional Rhythm
• Junctional Rhythm - Most Common Causes
• ECG and Junctional Rhythm
• Junctional Bradycardia

Junctional Rhythm

• In junctional rhythm, impulses originate in the AV junction
• The AV junction consists of the AV node and the His bundle
• Each impulse then spreads from the AV junction
• To the atria (creates a negative - retrograde P wave)
• To the ventricles (creates a QRS complex)
• Junctional rhythm has a frequency of 40-60/min.

• Junctional rhythm is a secondary pacemaker, activated when:
• Impulses stop arriving at the AV junction
• Impulses arrive at the AV junction with a lower frequency than that generated by the AV junction
• Junctional rhythm is a protective mechanism, protecting the heart from
• Asystole (ventricular standstill)
• Severe sinus bradycardia
• If junctional rhythm fails
• then a ventricular rhythm - the tertiary pacemaker - is activated

ECG and Junctional Rhythm

• Retrograde (Negative) P wave
• Negative in inferior leads (II, III, aVF)
• Positive (aVR, V1)
• P wave may be before, within, or after the QRS complex
• Narrow QRS complexes (< 0.12s)
  • QRS may be wide if aberrant conduction is present
• Heart Rate: 40 - 60/min.
• Heart action is regular (PP and RR interval do not change)

• Upper Junctional Rhythm
• P wave is before QRS

• Middle Junctional Rhythm
• P wave is hidden within QRS

• Lower Junctional Rhythm
• P wave is after QRS

Junctional Bradycardia

• Junctional bradycardia is a junctional rhythm with a frequency of < 40/min.
• Sinus bradycardia has a frequency of < 50/min.
  
  
• Based on frequency, junctional rhythm is classified as:
• Junctional bradycardia: < 40/min.
• Junctional rhythm: 40 - 60/min.
• Accelerated junctional rhythm: 60 - 100/min.
• Junctional tachycardia: > 100/min.

Junctional Bradycardia

• Frequency: 37/min. (< 40/min.)
• Sinus bradycardia has a frequency of < 50/min.
• P waves are hidden within the QRS complex
• Impulses are generated by the middle part of the AV junction
• Narrow QRS complexes (< 0.12s)
• The patient had SA block of the 3rd degree
• SA node generates impulses, but all are blocked

Junctional Rhythm

• Junctional rhythm: 45/min.
• This is not junctional bradycardia (frequency is not < 40/min.)
• P waves are hidden within the QRS complex
• Impulses are generated by the middle part of the AV junction
• Narrow QRS complexes (< 0.12s)