Tachyarrhythmias in the emergency department

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Target exams

Red flags

• An unstable tachyarrhythmia — hypotension, shock, syncope, ischaemic chest pain, acute heart failure, or altered consciousness — is cardioverted immediately, regardless of the rhythm
• A regular broad-complex tachycardia is ventricular tachycardia until proven otherwise — do NOT give verapamil, which can collapse a failing ventricle
• In pre-excited atrial fibrillation (Wolff-Parkinson-White, an irregular broad-complex rhythm with a delta wave), atrioventricular-node blockers — adenosine, verapamil, diltiazem, a beta-blocker, digoxin — are contraindicated; they preferentially block the AV node and accelerate conduction down the accessory pathway to ventricular fibrillation
• Adenosine is avoided in asthma (bronchospasm risk) and in high-grade heart block, and can cause a brief asystole — warn the patient and monitor continuously
• Torsades de pointes — a polymorphic broad-complex tachycardia with a twisting axis on a long QT — is treated with an intravenous magnesium bolus