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Educational draft · awaiting clinical reviewUse Rapid for revision, not patient-care decisions. Check current national and local guidance and the BNF or BNFC before acting.

Sinus node dysfunction

Cardiology · UK scope · Sources checked 27 Aug 2026 · Clinical review pending

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Escalate

Symptomatic bradycardia with shock, syncope, myocardial ischaemia or severe heart failure needs immediate monitored treatment. Give atropine 500 micrograms IV unless a specific contraindicating context applies, repeat every 3-5 minutes to 3 mg, and move promptly to pacing or second-line infusion if ineffective.

Synopsis

Link symptoms to sinus bradycardia or pauses, remove reversible causes, stabilise adverse bradycardia and select permanent pacing on clinical rather than rate criteria alone.

  • Sinus node dysfunction (SND) includes inappropriate sinus bradycardia, sinus arrest, sinoatrial exit block, chronotropic incompetence and tachy-brady syndrome.
  • There is no single heart-rate or pause threshold that diagnoses clinically important SND; demonstrate a symptom-rhythm correlation.
  • Exclude reversible extrinsic causes such as rate-limiting medicines, hypothyroidism, electrolyte disturbance, ischaemia, hypothermia and sleep apnoea.
  • Tachy-brady syndrome combines atrial tachyarrhythmia with long pauses or marked bradycardia, often after the atrial rhythm terminates.
  • In adverse bradycardia, RCUK atropine is 500 micrograms IV every 3-5 minutes to a total of 3 mg.
  • If atropine fails, use transcutaneous pacing as a bridge and arrange early transvenous pacing; isoprenaline or adrenaline infusion are drug bridges.
  • Permanent pacing treats symptomatic bradycardia; it does not treat AF stroke risk or remove the need to manage atrial tachyarrhythmias.

Key red flags

Adverse bradycardia

Shock, syncope, myocardial ischaemia or severe heart failure attributable to bradycardia requires immediate treatment.

Risk of asystole

Recent asystole, Mobitz II block, complete heart block with broad QRS or a ventricular pause longer than 3 seconds increases concern and prompts pacing readiness, although these may represent AV rather than sinus-node disease.

Investigation priorities

01
12-lead ECGFirst step

Confirm sinus origin and distinguish SND from AV block, blocked atrial ectopy or AF with a slow ventricular response.

Management branches

acuteBradycardia with adverse features

Bradycardia is causing shock, syncope, ischaemia or severe heart failure.

  1. Perform ABCDE assessment, monitor ECG/BP/SpO2, record a 12-lead ECG if this does not delay treatment, obtain IV access and correct immediate causes.
  2. Give atropine 500 micrograms IV; repeat every 3-5 minutes if needed to a maximum total of 3 mg.
  3. If ineffective, start transcutaneous pacing as a bridge and consider isoprenaline 5 micrograms/min IV or adrenaline 2-10 micrograms/min IV while arranging early transvenous pacing.
  4. Do not give atropine after cardiac transplantation, and do not use it for high-grade AV block with a wide QRS; move directly to effective pacing/appropriate alternatives with expert help.
stableStable suspected SND

Bradycardia or pauses are present without life-threatening features.

  1. Review rate-limiting medicines, thyroid and electrolytes, ischaemia, hypothermia, sleep apnoea and physiological conditioning.
  2. Select ambulatory-monitor duration based on symptom frequency and ask for time-stamped symptom recording.

Key medicines

Atropine500 micrograms IV, repeat every 3-5 minutes if needed to a maximum total of 3 mg.Do not use after cardiac transplantation; avoid high-grade AV block with wide QRS because it is ineffective and may worsen block. Do not delay pacing when response is poor.
IsoprenalineStart 5 micrograms/min by IV infusion and titrate with continuous monitoring.Can provoke tachyarrhythmia and myocardial ischaemia; specialist monitored use.
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Sources and review status5 sources · checked 27 Aug 2026 · clinical review pending+
Sources

Sources and review status

National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.

  • Resuscitation Council UK: Adult advanced life support 2025Bradycardia drugs, exceptions and temporary-pacing route.
  • Resuscitation Council UK: Adult bradyarrhythmia algorithm 2025Current atropine, second-line drug and temporary-pacing sequence.
  • ESC: 2021 cardiac pacing and CRT guidelineSND evaluation, symptom correlation and pacing selection.
  • NICE TA324: Dual-chamber pacemakers for symptomatic SNDDual-chamber pacing recommendation for symptomatic SND without AV block.
  • NHS: Pacemaker implantationProcedure, recovery, follow-up and urgent complications.

Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem · Content changes

Authoring stateRapid draftClinical stateAwaiting reviewJurisdictionUnited Kingdom
  • Use exercise testing for exertional limitation or suspected chronotropic incompetence.
  • Refer to cardiology when symptoms correlate with SND or unexplained syncope persists; observe asymptomatic physiological bradycardia without unnecessary pacing.