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Broad Complex Tachycardia / Ventricular Tachycardia
A broad complex tachycardia (QRS >120ms, rate >100) is VT until proven otherwise. Do not give AV nodal blockers (verapamil, diltiazem, adenosine) to a patient in VT — this can cause haemodynamic collapse. Treat according to haemodynamic stability.
Resuscitation Council UK Tachycardia Algorithm
The pathway
1 · Is the patient stable or unstable?
- Unstable (SBP <90, syncope, chest pain, HF signs): IMMEDIATE synchronised DC cardioversion.
- Stable: 12-lead ECG, continuous monitoring, senior review.
2 · 12-lead ECG analysis
Apply Brugada criteria: concordance, fusion/capture beats, AV dissociation, QRS morphology. VT is most likely unless proven otherwise. If in doubt, treat as VT.
3 · Unstable — DC cardioversion
Synchronised DC shock: 120–200J biphasic. Sedate with midazolam/propofol (anaesthetics help). Call ITU. Up to 3 shocks. If pulseless: unsynchronised defibrillation (ALS).
4 · Stable VT — pharmacological
Amiodarone 300mg IV over 20–60 minutes. If monomorphic VT with no structural heart disease: lidocaine 100mg IV over 2 minutes may be used under cardiologist guidance.
5 · Torsades de Pointes
Check QTc on ECG. Stop QT-prolonging drugs. MgSO₄ 2g IV over 10 minutes. If haemodynamically unstable: unsynchronised DC shock. Temporary pacing if bradycardia-dependent.
6 · Post-cardioversion
12-lead ECG after each intervention. Correct electrolytes (K+ >4, Mg >1). Identify underlying cause: ischaemia (troponin, coronary angiogram), cardiomyopathy, channelopathy (long QT, Brugada). Implantable defibrillator (ICD) discussion.
Drugs
| Drug | Dose | Route | Notes |
|---|---|---|---|
| Amiodarone | 300mg over 20–60 min | IV | Then 900mg over 23h maintenance. First-line for stable VT. |
| Lidocaine | 100mg over 2 min | IV | Alternative for monomorphic VT. Cardiologist guidance. |
| Magnesium sulphate | 2g over 10 min | IV | For Torsades de Pointes. Then 5–10mg/min infusion. |
| Midazolam | 2.5–5mg | IV | Sedation before DC cardioversion. Anaesthetic involvement preferred. |
When to escalate
Pulseless VT → ALS, defibrillation,Haemodynamic instability → immediate DC cardioversion,Torsades de Pointes → MgSO₄ + stop QT drugs,Refractory VT storm — ITU, amiodarone infusion, possible overdrive pacing,All VT requires cardiology review and long-term risk assessment
Reference: Resuscitation Council UK Tachycardia Algorithm 2021 / ESC VT Guidelines
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