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Tachycardia

NEWS calls

Sinus tachycardia is a response, not a rhythm to treat — find the cause.

Adverse features (shock, syncope, myocardial ischaemia, severe heart failure) = unstable.

Act now

  1. 1

    Oxygen if SpO₂ <94%, IV access, check K⁺, Mg²⁺, Ca²⁺.

  2. 2

    Unstable: synchronised DC shock (up to 3 attempts) under sedation/anaesthesia — call for expert help.

Assess

  • ABCDE, 12-lead ECG, continuous monitoring.
  • Decide: stable or unstable? Narrow (<0.12 s) or broad QRS? Regular or irregular?

Investigations

  • U&E, Mg²⁺, Ca²⁺, TFTs, troponin if ischaemia suspected, FBC, CRP; review drug chart.

Manage

  • Narrow regular (likely SVT): vagal manoeuvres, then adenosine if no pre-excitation, then verapamil or a beta-blocker.
  • Narrow irregular (likely AF): rate control with a beta-blocker (or diltiazem); consider digoxin or amiodarone if heart failure. Assess stroke risk (CHA₂DS₂-VASc) and bleeding risk (ORBIT). Discuss any cardioversion with a senior — duration of AF decides whether anticoagulation is needed first.
  • Broad regular (treat as VT unless known SVT with aberrancy): seek expert help. RCUK 2026 algorithm lists procainamide, or amiodarone if procainamide is unavailable.
  • Broad irregular: seek expert help — may be AF with bundle branch block, pre-excited AF or polymorphic VT (torsades: magnesium).

Escalate when

  • Any adverse feature, broad-complex tachycardia, or failure of first-line treatment: senior and cardiology.

Doses and prescribing

Adenosine

6 mg rapid IV bolus with flush via a large vein; then 12 mg; then 18 mg. Avoid in asthma; reduce dose with dipyridamole; warn the patient about transient chest discomfort.

Amiodarone

300 mg IV over 10–60 minutes (10–20 minutes if after failed shocks), then 900 mg over 24 hours, preferably via a central line.

Magnesium sulfate

2 g IV over 10 minutes for torsades de pointes.

Check the BNF and your local formulary before prescribing.

Written to current guidance (NICE NG196) · sources checked 14 Nov 2026. We watch NICE for updates weekly.

Sources (3)

Reviewed by Aboodee Alhasso, MPharm MRCPharm IP on 14 Nov 2026

Calculators for this

For healthcare professionals, as an aid to clinical judgement — not a substitute for it. Follow your local policy and ask a senior when in doubt.