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Emergency Medicine

Synchronized Cardioversion

Last Updated on February 13, 2023

Steps

  1. Explain to patient and/or next of kin the indication of cardioversion
  2. Analgesia ± sedation e.g. IV Fentanyl 50 – 100 mcg ± IV Midazolam 1 – 2 mg
  3. Turn on defibrillator
  4. Attach monitor leads to the patient
  5. Ensure proper display of the patient’s rhythm
  6. Press ‘sync‘ button
  7. Look for markers on R wave

Doses of Synchronized Cardioversion

Initial recommended doses:
• Narrow regular: 50 – 100 J
Narrow irregular: 120 – 200 J biphasic OR 200 J monophasic
• Wide regular: 100 J
Wide irregular: defibrillation dose (not for synchronized cardioversion)

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 rhythm in cardiac arrest

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  

Related Post

  1. Basic life support
  2. Atrial fibrillation

References

  1. Arrhythmic complications after electrical cardioversion of acute atrial fibrillation: The FinCV study
  2. Cardioverting acute atrial fibrillation and the risk of thromboembolism: not all patients are created equal

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