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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.

Ventricular arrhythmias

Cardiology · UK scope · Sources checked 25 Aug 2026 · Clinical review pending

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Escalate

Pulseless VT/VF is cardiac arrest: start high-quality CPR and defibrillate immediately. VT with a pulse plus shock, syncope with severe/ongoing hypotension, myocardial ischaemia, pulmonary oedema/severe heart failure or immediately post-ROSC needs synchronised cardioversion.

Synopsis

Recognise ventricular ectopy, VT, torsades and VF, then choose the correct shock, drug and investigation branch without delaying resuscitation.

  • A ventricular ectopic is a premature broad QRS without a normal preceding P wave; frequent/complex ectopy is a clue, not by itself an indication for suppression.
  • NSVT is at least three ventricular beats ending spontaneously within 30 seconds; sustained VT lasts at least 30 seconds or requires earlier termination because of instability.
  • Monomorphic VT has a stable QRS morphology; polymorphic VT varies beat to beat; torsades is polymorphic VT in the setting of QT prolongation.
  • Treat an uncertain regular broad-complex tachycardia as VT, especially in structural heart disease or prior MI.
  • Pulseless VT and VF are shockable cardiac-arrest rhythms; synchronised cardioversion is for VT with a pulse.
  • RCUK first manual biphasic defibrillation shock is at least 150 J (130-150 J for pulsed biphasic); if the recommended device setting is unknown, use the highest adult setting.
  • After three total shocks in VF/pVT give adrenaline 1 mg and amiodarone 300 mg; repeat adrenaline every 3-5 minutes and give amiodarone 150 mg after five total shocks.
  • Stable monomorphic VT is not automatically a drug-only case: RCUK recommends electrical cardioversion with structural heart disease or uncertain myocardial damage; drugs are conditional when sedation/anaesthesia risk is high.
  • Long-QT polymorphic VT: magnesium 8 mmol IV over 10 minutes, stop QT-prolonging drugs, correct electrolytes and consider overdrive with isoprenaline or temporary pacing; avoid amiodarone.
  • After stabilisation, investigate substrate—acute ischaemia, cardiomyopathy/scar, inflammation, inherited channelopathy, drug/toxin, electrolytes—and consider ICD/ablation according to cause and recurrence risk.

Key red flags

Monomorphic VT

Regular broad-complex tachycardia with a consistent QRS shape, usually from a fixed re-entry circuit in scar or cardiomyopathy. AV dissociation, capture/fusion beats and concordance support VT, but absence does not exclude it.

Torsades de pointes

Polymorphic VT with QRS complexes appearing to twist around the baseline in a patient with prolonged QT, often pause-dependent and triggered by drugs, bradycardia, hypokalaemia or hypomagnesaemia.

VF or pulseless VT

Unresponsive patient with abnormal/absent breathing and no signs of circulation; VF is chaotic without organised QRS and pVT is an organised ventricular tachycardia without a pulse. Both require immediate defibrillation/CPR.

Life-threatening VT with a pulse

Shock, syncope with severe/ongoing hypotension, myocardial ischaemia, severe heart failure/pulmonary oedema, or immediately post-ROSC.

Investigation priorities

01
Immediate ABCDE, pulse check, continuous ECG/BP/SpO2, defibrillator pads and 12-lead if a pulse is presentFirst step

Separate arrest from peri-arrest VT and capture diagnostic morphology without delaying shock.

Management branches

Cardiac arrestVF or pulseless VT

Unresponsive, abnormal breathing and shockable rhythm with no pulse/signs of circulation.

  1. Start high-quality CPR, call the arrest team and defibrillate as soon as possible. Use one shock followed immediately by two minutes of CPR.
  2. Manual biphasic first shock: at least 150 J (130-150 J for pulsed biphasic); escalate subsequent shocks when possible. If device recommendations are unknown, use the highest adult energy setting.
  3. After the third total shock, during CPR give adrenaline 1 mg IV/IO and amiodarone 300 mg IV/IO. Repeat adrenaline 1 mg every 3-5 minutes.
  4. After the fifth total shock give amiodarone 150 mg IV/IO. If amiodarone is unavailable or the resuscitation service has selected the RCUK-supported lidocaine alternative, give lidocaine 100 mg after three shocks and an additional 50 mg after five shocks; do not routinely combine the two.
  5. Treat reversible causes: hypoxia, hypovolaemia, hypo/hyperkalaemia and other metabolic disorders, hypothermia, thrombosis, tamponade, tension pneumothorax and toxins.
  6. For refractory VF after three consecutive shocks, ensure correct pad placement, escalate energy and consider vector change to antero-posterior pads; RCUK does not recommend routine double-sequential defibrillation.

Key medicines

Adrenaline in shockable cardiac arrest1 mg IV/IO after the third total shock, then 1 mg every 3-5 minutes while ALS continues.Give during CPR without delaying shocks/compressions; confirm route and flush per arrest practice. Post-ROSC bolus dosing is different and requires titration.
Amiodarone in VF/pulseless VT300 mg IV/IO after the third total shock; a further 150 mg after the fifth total shock.Use the arrest dose only in cardiac arrest. Do not substitute the slower perfusing-VT infusion regimen. Avoid for torsades/long-QT polymorphic VT.
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Sources and review status5 sources · checked 25 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 25 Aug 2026; clinical approval remains outstanding.

  • RCUK 2025 Adult Advanced Life Support
  • RCUK Adult tachyarrhythmia algorithm V3 March 2026
  • 2022 ESC ventricular arrhythmia and sudden cardiac death guidelineDiagnostic, ICD, ablation and inherited-disease context where NICE lacks a comprehensive guideline.
  • Amiodarone injection SmPC
  • Lidocaine injection SmPC

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

Authoring stateRapid draftClinical stateAwaiting reviewJurisdictionUnited Kingdom
Stable monomorphic VTElectrical versus pharmacological treatment is conditional

Sustained regular broad monomorphic VT with a pulse and no life-threatening feature.

  1. Treat as VT and seek expert help. RCUK recommends electrical cardioversion when structural heart disease exists or myocardial damage is uncertain.
  2. If sedation/anaesthesia creates increased risk, consider procainamide 10-15 mg/kg IV over 20 minutes (maximum 1 g) with continuous ECG/BP.
  3. If procainamide is unavailable or contraindicated, use amiodarone 300 mg IV over 10-60 minutes, followed by 900 mg IV over 24 hours.
  4. If drug treatment fails, use synchronised cardioversion with expert advice. Investigate ischaemia and structural substrate even after apparently successful termination.