Junctional rhythms

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 – Separate condition where a re-entry loop stimulates the AV node again and again

Etiology

• Digoxin – classic cause
• Beta-agonists, e.g. isoprenaline, adrenaline
• Myocardial ischemia
• 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