Synopsis
Treat broad-complex tachycardia safely as ventricular tachycardia unless a more secure diagnosis supports a specific alternative.
- A tachycardia with QRS duration 120 ms or more is broad complex; sustained regular broad tachycardia should be treated as VT when uncertain.
- Structural heart disease, previous myocardial infarction and older age increase the prior probability of VT.
- AV dissociation, capture beats, fusion beats and precordial concordance strongly support VT, but their absence does not exclude it.
Key red flags
Consider pre-excited AF, AF with bundle-branch block, frequent ventricular ectopy and polymorphic VT; inspect QT and beat-to-beat QRS morphology before giving drugs.
Investigation priorities
Define regularity, QRS morphology and adverse evolution while preserving a diagnostic tracing.
Management branches
No signs of life or definite pulse.
- Call the cardiac-arrest team, start high-quality CPR and attach a defibrillator.
- Treat VF/pulseless VT with unsynchronised shocks under the 2025 RCUK ALS algorithm, resuming CPR immediately after each shock.
A pulse is present and no life-threatening adverse feature is identified.
Key medicines
Procainamide10-15 mg/kg IV over 20 minutes, maximum 1 g.
AmiodaroneRCUK stable broad-tachycardia alternative: 300 mg IV over 10-60 minutes then 900 mg IV over 24 hours; after failed cardioversion in an unstable patient, 300 mg IV over 10-20 minutes before another shock.