Junctional rhythms
Junctional rhythms Overview : j unctional 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
