Sustained (more than 30 seconds) or non-sustained tachycardias with QRS wider than 0.12 seconds.

Regular wide QRS tachycardia

Treat as ventricular tachycardia until proved otherwise (regular wide QRS supraventricular tachycardias are uncommon). Refer all cases after resuscitation and stabilisation.

• No cardiac arrest: DC cardioversion 200 J after sedation with A: diazepam IV 10–20 mg; if 200 J fails, use 360 J. DC cardioversion is first-line even if the patient is stable.

• Cardiac arrest: defibrillate (not synchronised) with full CPR.

• Medicines if VT recurs after cardioversion: S: amiodarone IV 5 mg/kg (150–300 mg) over 30 minutes, then maintenance to a total of 1,200 mg in 24 hours; OR S: amiodarone PO 800 mg every 24 hours for 7 days, 600 mg/day for 3 days, then 200–400 mg/day (specialist monitoring – serious long-term side effects).

• OR A: lidocaine IV 50–100 mg (1–2 mg/kg), repeated every 5 minutes if needed to a total of 200–300 mg; for recurrent VT only, then 1–3 mg/minute for 24–30 hours (ends only about 30% of sustained VT; may cause hypotension, heart block or convulsions).

• Never give IV verapamil in wide QRS tachycardia.

Sustained irregular wide QRS tachycardia

• Usually atrial fibrillation with bundle branch block, or pre-excitation (WPW).

• Typical right or left bundle branch block pattern with rate below 170/minute: treat as atrial fibrillation (anticoagulation and rate control).

• Rate above 170/minute and/or atypical or variable complexes: likely WPW with AF through the bypass tract – DC cardioversion.

• Refer to a high-level centre for arrhythmia mapping and radiofrequency ablation.

Non-sustained irregular wide QRS tachycardia

• Usually ventricular, often in acute myocardial infarction; treat only if there is significant haemodynamic compromise. Keep serum potassium above 4 mmol/L.

• S: Amiodarone IV 5 mg/kg (150–300 mg) over 30 minutes, then maintenance to 1,200 mg in 24 hours, or the oral schedule above.

• Only in a haemodynamically stable patient: A: lidocaine IV 50–100 mg (1–2 mg/kg), repeated every 5 minutes to 200–300 mg, then 1–3 mg/minute for 24–30 hours for recurrent VT.

• Without acute ischaemia or infarction, consider torsade de pointes (magnesium sulfate 2 g IV over 5–10 minutes).