Synopsis
Recognise ventricular pre-excitation, manage AV re-entry and pre-excited atrial fibrillation safely, and identify who needs electrophysiology risk assessment or ablation.
- Pre-excitation means an accessory atrioventricular pathway conducts to the ventricle outside the AV node; WPW syndrome is pre-excitation plus symptomatic tachyarrhythmia.
- The sinus-rhythm ECG classically shows a short PR interval, slurred initial QRS upstroke (delta wave) and a widened QRS.
- Orthodromic AV re-entrant tachycardia is usually regular and narrow because antegrade conduction uses the AV node; antidromic AVRT is broad.
Key red flags
An irregular broad tachycardia with changing QRS morphology and very short RR intervals is the critical pattern.
Investigation priorities
Confirm and localise pre-excitation and look for alternative conduction disease.
Management branches
The rhythm is regular, QRS is under 120 ms and there is no evidence of pre-excited AF.
- Record a 12-lead ECG and perform vagal manoeuvres while monitoring continuously.
- If unsuccessful and there is no pre-excitation in the tachycardia, give adenosine 6 mg as a very rapid IV bolus followed by a flush.
Key medicines
AdenosineRCUK March 2026: 6 mg by very rapid IV bolus, then 12 mg if unsuccessful, then 18 mg if still unsuccessful, each followed by a rapid flush and given with continuous ECG recording. This resuscitation-algorithm sequence differs from the cited product SmPC's licensed 3 mg, 6 mg, then 12 mg sequence.
ProcainamideRCUK: 10-15 mg/kg IV over 20 minutes, maximum 1 g, with continuous ECG and blood-pressure monitoring.