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Junctional Tachycardia

caution
Lead II
25 mm/s10 mm/mV
HR
72
bpm
RR
833
ms
QT
273
ms

Junctional Tachycardia

An automatic AV-junctional focus firing above 100 bpm. A narrow-complex tachycardia that, unlike AVNRT/AVRT, is automatic (not re-entrant) — so it warms up and cools down rather than starting and stopping abruptly, and does not usually terminate with adenosine.

Recognition· 4
  • Regular narrow QRS tachycardia (>100 bpm)
  • Absent, retrograde, or dissociated P waves
  • Warm-up/cool-down, not abrupt on/off
  • Often does NOT respond to adenosine
Mechanism

An irritable junctional focus fires fast on its own

Enhanced automaticity in the AV junction drives the ventricles above 100 bpm. Because it is automatic rather than re-entrant, it accelerates and decelerates gradually and is not sustained by a circuit adenosine can interrupt.

Findings· 3
  • Regular narrow-complex tachycardia >100 bpm (often 100–140).
  • P waves absent, retrograde, or dissociated.
  • QRS morphology identical to sinus.
Clinical Impact
Digoxin toxicity (classic in adults)
↓
Junctional ectopic tachycardia after paediatric cardiac surgery
↓
Loss of AV synchrony at fast ratesRISK

Automatic junctional focus — find and treat the cause

Management· 2
1

Primary Treatment

Treat the cause (hold digoxin, correct electrolytes/ischaemia).

2

Additional Options

Adenosine is diagnostic but usually non-converting; refractory cases may need antiarrhythmics or, in children, cooling and overdrive pacing.