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Educational draft · awaiting clinical reviewUse Rapid for revision, not patient-care decisions. Check current national and local guidance and the BNF or BNFC before acting.

Broad-complex tachycardia

Cardiology · UK scope · Sources checked 27 Aug 2026 · Clinical review pending

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Pulseless VT is a cardiac arrest requiring immediate defibrillation and ALS. With a pulse, shock, severe hypotensive syncope, myocardial ischaemia, pulmonary oedema or post-ROSC status requires synchronised cardioversion.

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.
  • Unstable VT with a pulse: synchronised 120-150 J shock, escalating if needed; pulseless VT: unsynchronised defibrillation under ALS.
  • Current RCUK also recommends electrical cardioversion for stable monomorphic VT with structural heart disease or uncertain myocardial status.
  • If sedation or anaesthesia is judged unusually hazardous in stable monomorphic VT, IV procainamide is the drug option; IV amiodarone is the alternative when procainamide is unavailable or contraindicated.
  • An irregular broad rhythm may be pre-excited AF or polymorphic VT; AV nodal blockers can be dangerous in the former and amiodarone should be avoided in torsades.
  • Adenosine is reserved for a regular broad rhythm suspected to be SVT with aberrancy; if it fails, treat as VT.

Key red flags

Irregular broad rhythm

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.

Life-threatening features

Shock, syncope with severe or ongoing hypotension, myocardial ischaemia, severe pulmonary oedema or immediately post-ROSC triggers the unstable route.

Investigation priorities

01
Continuous monitoring and 12-lead ECGFirst step

Define regularity, QRS morphology and adverse evolution while preserving a diagnostic tracing.

Management branches

pulselessPulseless broad tachycardia

No signs of life or definite pulse.

  1. Call the cardiac-arrest team, start high-quality CPR and attach a defibrillator.
  2. Treat VF/pulseless VT with unsynchronised shocks under the 2025 RCUK ALS algorithm, resuming CPR immediately after each shock.
  3. Give adrenaline and amiodarone at the shock points specified by ALS and treat reversible causes.
  4. After ROSC, obtain a 12-lead ECG and investigate the precipitant and secondary-prevention needs.
stable-regularStable regular broad-complex tachycardia

A pulse is present and no life-threatening adverse feature is identified.

  1. Seek expert help, treat as VT and favour synchronised cardioversion when structural heart disease is present or myocardial status is uncertain.
  2. If sedation/anaesthesia risk is too high, give procainamide 10-15 mg/kg IV over 20 minutes with continuous ECG and blood pressure monitoring.
  3. If procainamide is unavailable or contraindicated, give amiodarone 300 mg IV over 10-60 minutes, followed by 900 mg IV over 24 hours.

Key medicines

Procainamide10-15 mg/kg IV over 20 minutes, maximum 1 g.Continuous ECG and blood-pressure monitoring; slow or stop for hypotension, marked QRS widening or QT prolongation.
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.Avoid in torsades/long-QT polymorphic VT and pre-excited AF. The eMC general SmPC regimen is different: 5 mg/kg over 20 minutes to 2 hours, up to 1200 mg/24 h; the RCUK doses above are the peri-arrest algorithm doses.
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Sources and review status6 sources · checked 27 Aug 2026 · clinical review pending+
Sources

Sources and review status

National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.

  • Resuscitation Council UK: Adult tachyarrhythmia algorithm, March 2026Current broad-complex, torsades and pre-excited AF pathways.
  • Resuscitation Council UK: Adult advanced life support 2025Adverse features, cardioversion energy and failed-shock treatment.
  • Resuscitation Council UK: ALS FAQsRationale for cardioversion in stable monomorphic VT.
  • ESC: 2022 ventricular arrhythmias guidelineDiagnostic evaluation and longer-term management.
  • eMC: Amiodarone 30 mg/mL solution SmPCGeneral licensed IV infusion regimen and torsades caution, contrasted with RCUK.
  • eMC: Adenosine 3 mg/mL injection SmPCProduct-specific licensed dosing, contraindications and interactions, contrasted with the current RCUK algorithm.

Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem · Content changes

  • If a regular SVT with aberrancy is genuinely suspected, monitored rapid-bolus adenosine may be tried; if ineffective, revert immediately to the VT route.
    • Authoring stateRapid draftClinical stateAwaiting reviewJurisdictionUnited Kingdom