AV dissociation, bradycardia, syncope, cannon a-waves
ABCDE
Monitor + pads; atropine; transcutaneous pacing if unstable; treat reversible causes.
Symptomatic bradycardia: Atropine 1 mg IV every 3–5 min (max 3 mg)
If atropine insufficient → Transcutaneous pacing
Definitive → Permanent pacemaker
Decision tree
Adverse signs (shock, syncope, ischaemia, HF)?
YesResponds to atropine?
YesObserve; identify reversible cause; plan pacing
NoTranscutaneous pacing → transvenous → permanent pacemaker
NoMonitor; permanent pacemaker for high-grade/symptomatic block
Order set
- ECG
- Continuous monitoring
- Atropine ready
- Transcutaneous pacing pads
- K⁺, drug review, troponin
Criteria
AdmitAll symptomatic/high-grade block
ICUUnstable awaiting pacing
DischargePaced (temporary→permanent), reversible causes excluded
Never
- Delay transcutaneous pacing while escalating drugs in unstable bradycardia — drugs are a bridge only
Key
- Atropine blocks ACh at SA/AV node → ↑ rate; often fails in infranodal block → pace.
- Atropine ineffective → dopamine infusion 5–20 mcg/kg/min or epinephrine infusion 2–10 mcg/min are equal second-line alternatives to pacing (2025 AHA); temporary transvenous pacing reasonable (Class 2a) for persistent unstable bradycardia.
Clinical detail — differentials, red flags, pitfalls, disposition
Red flags
- Syncope
- Hemodynamic instability
- Wide escape/asystole pauses
Differentials
- High-grade AV block
- Sinus arrest
- Drug/electrolyte cause
Common mistakes
- Relying on drugs alone when pacing is indicated
- Missing reversible cause (drugs, ↑K⁺, ischaemia)
Disposition & follow-up
Pacing → permanent pacemaker.
Discharge package
MedicationsReview AV-blocking drugs
Follow-upPacemaker clinic
Warning symptomsSyncope, dizziness, device-site issues
💊 Treatment detail — doses & preparation
Atropineantimuscarinic
DoseBradycardia: 1 mg IV q3–5 min (max 3 mg). Organophosphate: 1–2 mg IV bolus, double q5 min until secretions dry, then infusion 10–20% of loading dose/h
Preparation1 mg/mL ampoule undiluted; organophosphate needs many mg — stock 10+ ampoules
MonitorHR, secretions, pupils (not a target in OP); tachycardia, urinary retention
Adrenaline infusionvasopressor/inotrope
Dose0.05–1 mcg/kg/min IV infusion, titrate to effect
Preparation4 mg in 250 mL D5W/NS (16 mcg/mL) via pump; central access for prolonged use
MonitorTachycardia, arrhythmia, lactate rise; invasive MAP
Pacingdefinitive
DoseTranscutaneous pads NOW if unstable → transvenous wire → permanent pacemaker
PreparationPads front-back, start 60–80 bpm, increase mA until capture
MonitorCheck mechanical capture by pulse, not just ECG
📖 ESC Pacing / ACC-AHA BradycardiaReviewed July 2026