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Bradycardia
Slow is only a problem if it's causing trouble — or about to. Look for adverse features, judge the risk of asystole, climb the treatment ladder (atropine, then pacing or adrenaline), and search hard for the reversible causes. Built for revision, not live patient decisions.
Settle them, and check the basics
adverse features?Red flags — what each should make you think
Always ask "why is it slow?" before you reach for the pacing wire. Hyperkalaemia, drug toxicity, inferior MI, hypothermia, hypothyroidism and raised intracranial pressure are all common, treatable causes that pacing won't fix.
If adverse features are present (Resus Council UK)
- AtAtropine 500 micrograms IV
- ⚡Not responding: pace
- AdOr drug infusion
- ☎Expert help
- ECG12-lead + pads on
- K⁺Check K⁺ and drugs
Understand the patient — read the rhythm
which block?The heart blocks
- First-degree — PR over 0.2 s, every P conducts. Usually benign.
- Mobitz I (Wenckebach) — PR lengthens until a beat drops. Often benign (inferior MI, vagal, drugs).
- Mobitz II — fixed PR with sudden dropped beats. High risk of complete block.
- Complete (third-degree) — P waves and QRS unrelated. Narrow escape = junctional (more stable); broad escape = ventricular (unstable).
Even without adverse features, Mobitz II, complete heart block with broad QRS, pauses over 3 s, or recent asystole mean a high risk of asystole: get expert help and arrange pacing.
Reversible causes
- Drugs — beta-blockers, calcium channel blockers, digoxin, amiodarone, ivabradine
- Inferior MI (RCA supplies the AV node)
- Hyperkalaemia, hypothermia, hypothyroidism, hypoxia
- Raised intracranial pressure
- Vagal (vomiting, pain) and athletes (physiological)
Work A–E — assess and act as you go
The diagnoses you must not miss
tap to open eachWhat points toward it, what would rule it in, and how to manage it.
Syncope (Stokes–Adams), dizziness, heart failure, slow broad escape rhythm.
12-lead ECG.
Atropine (often less effective), transcutaneous pacing or adrenaline infusion as a bridge, cardiology for transvenous/permanent pacing.
AKI, CKD, ACEi/ARB, spironolactone; slow broad complexes, peaked T waves.
VBG potassium.
IV calcium, insulin–glucose; see the electrolyte emergencies page.
Bradycardia with hypotension; CCB → hyperglycaemia; digoxin → nausea, visual change, hyperkalaemia, any arrhythmia.
Drug history, digoxin level, glucose, K⁺.
Discuss with TOXBASE/NPIS. High-dose insulin euglycaemia therapy and calcium (CCB, beta-blocker), glucagon (beta-blocker), digoxin-specific antibody fragments (digoxin).
Bradycardia, hypertension and irregular breathing with headache, falling GCS, unequal pupils.
Urgent CT head.
Neurosurgical emergency — don't try to "fix" the heart rate.
Investigate — what to order, when, and what it tells you
test with a question in mindECG
Bloods
Other
How the plan comes together
disposition · handoverhome / outpatient
Asymptomatic sinus bradycardia or first-degree block/Mobitz I with no adverse features and no reversible cause concerns.
CCU / cardiology
Adverse features, risk of asystole, needing pacing or infusion, toxic cause, or MI.
Hand over: rhythm (with ECG), drugs given, pacing status, cause found.
Adverse features? Atropine, then pacing or adrenaline. Risk of asystole? Get help even if they look well. And always check K⁺ and the drug chart. Nicely done getting here.
Clerking template
copy or downloadBradycardia — documentation structure
A structure and prompt list to help you document and think systematically. It is not a completeness check and cannot guarantee nothing is missed — use your trust's own proforma, your seniors, and your clinical judgement.
Test yourself
active recallCover the answer, say it out loud, then reveal. Retrieval beats re-reading.
0 / 11 knownFrequently asked questions
quick answersWhat are the red flags for bradycardia?
- Shock, syncope, ischaemia, heart failure — think adverse features — treat
- Mobitz II / complete heart block — think risk of asystole
- Ventricular pause above 3 s — think risk of asystole
- Recent asystole — think risk of asystole
- High K⁺ + broad QRS — think hyperkalaemia
- Beta-blocker / CCB / digoxin overdose — think toxic bradycardia — antidote
- Bradycardia + hypertension + headache, low GCS — think raised ICP (Cushing)
What is the initial management of bradycardia?
- Atropine 500 micrograms IV — repeat every 3–5 min to a maximum of 3 mg
- Not responding: pace — transcutaneous pacing (with analgesia/sedation)
- Or drug infusion — adrenaline 2–10 micrograms/min IV, or isoprenaline, per local guidance
- Expert help — for transvenous pacing
- 12-lead + pads on — monitor continuously
- Check K⁺ and drugs — calcium for hyperkalaemia; antidotes for toxicity
Always alongside senior support and your local guideline.
What diagnoses must you not miss in bradycardia?
- Complete heart block — P and QRS dissociated
- Hyperkalaemia — bradycardia + broad QRS
- Beta-blocker / CCB / digoxin toxicity — overdose or accumulation
- Raised intracranial pressure — Cushing's reflex
Open each one in the must-not-miss section for what points toward it, how to rule it in, and how to manage it.
What investigations should a junior doctor order for bradycardia?
- ECG — Type of block, ischaemia, hyperkalaemia, digoxin effect.
- Bloods — K⁺, Mg, Ca, troponin, TFT, glucose.
- Other — Hypothermia.
Admit or discharge: how is the plan decided for bradycardia?
- Home / outpatient — Asymptomatic sinus bradycardia or first-degree block/Mobitz I with no adverse features and no reversible cause concerns.
- Ccu / cardiology — Adverse features, risk of asystole, needing pacing or infusion, toxic cause, or MI.
Is there a clerking template for bradycardia?
Yes — there is a free clerking template for bradycardia on this page, structured as presenting complaint, red flags asked, history, examination (A–E), investigations, differentials, plan and escalation. You can copy it or download it as a Word document. Jump to the template.
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