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.
Key red flags
Shock, syncope, myocardial ischaemia or severe heart failure attributable to bradycardia requires immediate treatment.
Investigation priorities
Confirm sinus origin and distinguish SND from AV block, blocked atrial ectopy or AF with a slow ventricular response.
Management branches
Bradycardia is causing shock, syncope, ischaemia or severe heart failure.
- 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.
- Give atropine 500 micrograms IV; repeat every 3-5 minutes if needed to a maximum total of 3 mg.
Bradycardia or pauses are present without life-threatening features.
Key medicines
Atropine500 micrograms IV, repeat every 3-5 minutes if needed to a maximum total of 3 mg.
IsoprenalineStart 5 micrograms/min by IV infusion and titrate with continuous monitoring.