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Synchronised DC cardioversion [advanced]

Before you start

Routine indications: AF/atrial flutter after 4 weeks anticoagulation

Emergency indications: tachyarrhythmia with adverse signs (shock, syncope, myocardial ischaemia, heart failure)

Synchronised DC cardioversion is used for patients with a pulse (shock synchronises with R wave to avoid inducing VF)

Unsynchronised DC cardioversion (defibrillation) is used for patients without a pulse (cardiac arrest) – see ALS


Skip this section if it is being performed as an emergency.

  • Read referral letter
  • Check potassium >4mmol/L
  • Check ECG still shows AF/flutter
  • Consent patient
    • Risks: stroke (<1%), pain or burns from pads, failure (1/3), ventricular arrhythmias (may require further shocks/CPR), bradycardia or asystole (may require external pacing)
  • Check anticoagulation has been taken for >4 weeks
    • NOAC – check no missed doses
    • Warfarin – check INRs in last 3 weeks are >2
  • Check patient is clinically well and fit for anaesthetic


  • Anaesthetist must be present to sedate patient
  • Apply 3-lead cardiac monitoring (clockwise from right arm Ride Your Green Bicycle) and connect lead to external cardiac monitor or defibrillator machine
    • Red: anterior aspect of right shoulder
    • Yellow: anterior aspect of right shoulder
    • Green: left anterior superior iliac spine
    • Black: not present on defibrillation machine
  • Apply defibrillator pads (in AP position) after shaving chest if required
    • ‘Right’ pad: place longitudinally on left sternal edge
    • ‘Left’ pad: place longitudinally on left paraspinal muscles (in line with anterior pad)
  • Connect pads lead to defibrillator machine
  • Set defibrillator machine monitoring trace to ‘pads’
  • Set defibrillator to synchronised mode (synchronises shock with R wave to avoid inducing VF)
  • Set energy level (increase as shown if unsuccessful)
    • Broad-complex tachycardia or AF: 150J → 200J → 200J  (biphasic)
    • Narrow complex tachycardia or atrial flutter: 70J → 120J → 200J  (biphasic)
  • Ask anaesthetist to sedate patient and wait until they are happy to proceed
  • Ask everybody to move away from the patient and ask for the oxygen to be moved away
  • Press charge (then move hand away from button)
  • Re-check everybody and oxygen is away from the patient, announce you are about to shock and press and hold the shock until shock is delivered (it will wait for the R wave)
  • Re-assess the rhythm
  • If unsuccessful, repeat at next energy (maximum 3 attempts)

Dealing with complications

  • Asystole or bradycardia with haemodynamic compromise (SBP<90) → if sustained, proceed to transcutaneous pacing
    • Set defibrillator to pacing mode
    • Set onscreen pacing rate (default usually ̴ 70bpm) and energy (default starting energy usually ̴ 30mA)
    • Click onscreen start pacing button
    • Observe the monitor to see if QRS complexes follow every pacing spike – if not, increase the energy until they do – ‘electrical capture’ (usually occurs at 50-100mA)
    • Next check the patients pulse corresponds to the induced QRS complexes – ‘mechanical capture’
    • Seek senior help if does not resolve
    • Note you can touch the patient during pacing
  • Bradycardia without haemodynamic compromise → monitor, reduce β-blockers
  • Ventricular tachycardia with pulse → repeat synchronised DC shock as above
  • Pulseless arrhythmia → unsynchronised DC shock if shockable rhythm (VT/VF); if ongoing or not shockable rhythm, start chest compressions and manage as cardiac arrest (see ALS)


  • Document procedure
  • Complete discharge letter
    • Continue all medications (except digoxin if taking and successfully cardioverted)
    • Continue anticoagulation until patient has been reviewed at least 4 weeks post-cardioversion
  • Book for clinic follow up
  • Re-check ECG and observations
  • Advise patient not to drive for 24 hours and stay with someone overnight
DC cardioversion set up