Life-threatening features: shock, syncope, myocardial ischaemia, severe heart failure.
Risk of asystole: recent asystole, Mobitz II block, complete heart block with broad QRS, ventricular pause over 3 seconds.
Act now
- 1
Oxygen if hypoxic, IV access, defibrillator pads on if any adverse feature.
- 2
Life-threatening features: atropine 500 micrograms IV; if not satisfactory, repeat up to a total of 3 mg.
- 3
Still unstable: isoprenaline or adrenaline infusion, or transcutaneous pacing — get expert help.
Assess
- ABCDE, 12-lead ECG, continuous monitoring.
- Causes: drugs (beta-blockers, rate-limiting calcium-channel blockers, digoxin, amiodarone, donepezil), inferior MI, hyperkalaemia, hypothyroidism, hypothermia, raised intracranial pressure.
Investigations
- U&E (K⁺), calcium, magnesium, glucose, TFTs, troponin, digoxin level if on digoxin.
Manage
- No life-threatening features but risk of asystole: expert help and arrange transvenous pacing.
- Neither: observe, correct the cause, hold rate-limiting drugs.
- Beta-blocker or calcium-channel blocker toxicity: consider glucagon (follow TOXBASE).
Escalate when
- Any life-threatening feature or risk of asystole: senior and cardiology.
Doses and prescribing
Atropine
500 micrograms IV, repeat to a maximum of 3 mg.
Isoprenaline
5 micrograms/minute IV infusion.
Adrenaline
2–10 micrograms/minute IV infusion.
Check the BNF and your local formulary before prescribing.
Written to current guidance · sources checked 14 Nov 2026. We watch NICE for updates weekly.
Sources (2)
- Resuscitation Council UK — Adult bradyarrhythmia algorithm (2025)Version 27 Oct 2025, checked 14 Nov 2026
- BNF — check doses, cautions and renal adjustmentchecked 14 Nov 2026
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.