Last Updated on August 19, 2026
Steps
- Explain to patient and/or next of kin the indication of cardioversion
- Analgesia ± sedation e.g. IV
Fentanyl
50 – 100 mcg ± IV Midazolam 1 – 2 mg×Fentanyl
Fentanyl: https://www.myhouseman.my/fentanyl/
- Turn on defibrillator
- Attach monitor leads to the patient
- Ensure proper display of the patient’s rhythm
- Press ‘sync‘ button
- Look for
markers
on R wave×
If no markers, adjust the monitor gain until markers seen on each R wave
Doses of Synchronized Cardioversion
Initial recommended doses: e.g. atrial fibrillation VF / pulseless VT
• Narrow regular: 50 – 100 J
•
Narrow irregular
• Wide regular: 100 J
•
Wide irregular
Aim
- To restore sinus rhythm
Risks / Complications[1]
- Skin burn
- Cardiac arrhythmias, most often bradycardia & sinus arrest
- Increased risk for thromboembolic complications if no adequate anticoagulation is used
Thromboembolic event
- Majority of thromboembolic events occurring shortly after cardioversion (median 2 days); up to 30 days post cardioversion
- If AF >48 hours, sustained period of anticoagulant is recommended.
- Cardioversion of patients with AF of >48 hours duration had a 5–7% risk of stroke without preceding anticoagulation
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Practical notes:
- If patient has underlying atrial fibrillation but not on anticoagulant, admitted for fast AF in failure, DO NOT SIMPLY DO SYNCHRONIZED CARDIOVERSION. Consult Cardiology team if in doubt.
Defibrillation VS Synchronized Cardioversion
Defibrillation | Cardioversion |
A process of stopping ventricular fibrillation by delivery of controlled electric shock to the heart | A process of converting perfusing but unstable rhythm back to sinus rhythm |
Method: electrical | Method: electrical / pharmacological |
NOT synchronised to cardiac rhythm | MUST be synchronized with cardiac rhythm (shock is timed to discharge immediately after large R wave / S wave) |
Indication:
shockable
Shockable rhythm: Ventricular fibrillation, pulseless ventricular tachycardia Non-shockable rhythm: asystole, pulseless electrical activity (PEA) | Indication: unstable tachyarrhythmia except sinus tachycardia (e.g. unstable atrial fibrillation) |
Energy delivered: usually start with 120 J, then escalate | Energy delivered: depends on rhythm e.g. in SVT start with 50J then escalate |