Armando Hasudungan
Biology and Medicine videos

Junctional Arrythmias

Overview Junctional rhythms occur when the AV node takes over as the primary pacemaker.  Junctional rhythm usually is associated with a benign course

Mechanism

  • SA node has failed
  • AV node just wants to be faster and takes over
    • Enhanced automaticity in AV nodal cells
Think AVNRT – Seperate condition where a re-entry loop stimulates the AV node again and again

Aetiology

  • Digoxin – classic cause
  • Beta-agonists, e.g. isoprenaline, adrenaline
  • Myocardial ischaemia
  • Myocarditis
  • Cardiac surgery
  • Hypokalaemia
  • Cardiac surgery

Junctional rhythm ECG features

  • Narrow QRS (<1.2)
  • Ventricular rate 60-100
  • Shortened PR interval
  • Inverted P wave just before QRS
  • P wave buried in QRS
Remember Junctional tachycardia has narrow QRS, absent or inverted P waves

Differential Diagnoses

  • AVRT
  • AVNRT

Management

  • Usually observation
  • Treat underlying cause if needed
  • Discontinue causative medications
  • Permanent pacemaker