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

AVNRT – Seperate condition where a re-entry loop stimulates the AV node again and again.

Aetiology and Risk Factors

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.

Diagnosis

  • AVRT
  • AVNRT

Treatment

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

Discussion

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