FFinalistSouthampton · 2027
Cardiovascular
AKT · Cardiovascular/Arrhythmias & conduction

Ventricular tachycardia & fibrillation

Ventricular re-entry/ectopic focus (VT) → disorganised ventricular activity (VF)

Overview

Broad-complex tachycardias arising from the ventricles. Monomorphic VT (often post-MI scar) and polymorphic VT (e.g. torsades de pointes from a long QT) can degenerate into ventricular fibrillation — a non-perfusing rhythm and the commonest cause of cardiac arrest. A broad-complex tachycardia is VT until proven otherwise.

Recognise

  • Broad-complex (QRS >120 ms) regular tachycardia; may cause palpitations, syncope, chest pain or cardiac arrest
  • VF / pulseless VT: no output → cardiac arrest, shockable rhythm
  • Torsades de pointes: polymorphic VT with a twisting axis on a background of long QT

Red flags

  • Pulseless VT or VF → immediate defibrillation + ALS (shockable arm)
  • Unstable VT with a pulse → synchronised DC cardioversion
  • Torsades → IV magnesium sulfate; stop QT-prolonging drugs; correct K/Mg

Differentials & how to tell them apart

SVT with aberrancy/bundle branch blockalso broad — but treat a broad-complex tachycardia as VT unless clearly known SVT
Pre-excited AF (WPW)irregular broad complex
Artefactunderlying normal complexes visible through it
Ventricular tachycardia — regular broad-complex tachycardia (ECG)

Ventricular tachycardia — regular broad-complex tachycardia (ECG)

Kshe (orig. uploader) / CC BY-SA 2.5 — Wikimedia Commons

Investigations

12-lead ECG (broad complex; capture beats/fusion beats/AV dissociation favour VT); electrolytes (K, Mg, Ca), troponin; echo for structural disease; QTc on the recovery ECG; consider ischaemia/channelopathy work-up.

Management

Pulseless → defibrillate + ALS; stable VT → IV amiodarone; torsades → IV magnesium

  1. 1Is there a pulse? Pulseless VT/VF → immediate defibrillation and ALS (shockable arm): adrenaline after the 3rd shock then 3–5-minutely, amiodarone 300 mg after the 3rd shock; treat 4 Hs & 4 Ts.Gate: VT WITH a pulse: if unstable → synchronised DC cardioversion; if stable → IV amiodarone. Polymorphic VT on long QT (torsades) → IV magnesium, not amiodarone.
  2. 2After return of circulation, find and treat the cause (ischaemia, electrolytes, drugs, channelopathy); consider an ICD for secondary prevention.
Pulseless VT/VF: defibrillate + CPR; adrenaline 1 mg after 3rd shock then every 3–5 min; amiodarone 300 mg after 3rd shock — shockable ALS arm; treat reversible causes (4 Hs & 4 Ts)
Stable VT with pulse: IV amiodarone — correct electrolytes; cardiology input
Unstable VT with pulse: synchronised DC cardioversion — under sedation
Torsades: IV magnesium sulfate 2 g — stop QT-prolonging drugs, correct K/Mg; overdrive pacing if recurrent
ICD — secondary prevention after sustained VT/VF not due to reversible cause; primary prevention in severe LV dysfunction

Key points

Broad-complex tachycardia = VT until proven otherwise. No pulse (VT/VF) → shock + ALS. Pulse but unstable → synchronised cardioversion. Twisting polymorphic VT on long QT = torsades → IV magnesium and remove QT-prolonging drugs.

Monitor & prognosis

Continuous ECG, electrolytes, QTc; ICD interrogation.

VF is the leading cause of sudden cardiac death; early defibrillation is decisive.

Source: Resuscitation Council UK ALS; cross-ref acute_care (cardiac arrest)