Electrical Synchronized Cardioversion of Atrial Fibrillation

Atrial Fibrillation with hemodynamic instability
Atrial Fibrillation >48 hours on Anticoagulation for >4 to 6 weeks (or cleared of atrial thrombus by TEE)
Atrial Fibrillation <48 hours and not on Anticoagulation
1. See precautions in Atrial Fibrillation Cardioversion
  1. Thromboembolism risk still exists despite short duration of Atrial Fibrillation
2. Consider Transesophageal Echocardiogram prior to cardioversion
3. Other required criteria
  1. No significant left atrial enlargement
    1. Left atrium >4.5 cm poorly maintains sinus rhythm
  2. CHADS2-VASc Score <2 in men or <3 in women
    1. If CHADS-VASc Score higher, avoid cardioversion unless <12 hours from known onset
  3. NO history of stroke or Transient Ischemic Attack in prior 6 months
  4. NO valvular Atrial Fibrillation (Mechanical Heart Valves, Mitral Stenosis)

Conversion Rate: 86-94% (contrast 51% efficacy of chemical cardioversion)
1. Higher success rates in Atrial Flutter than with Atrial Fibrillation
Emergency department electrical cardioversion is safe and effective
1. Stiell (2017) Ann Emerg Med 69(5): 562-71 +PMID:28110987 [PubMed]

Dose adjustments
1. Adjust dose if on Digoxin (see below)
2. Higher dose (200 Joules) needed in Atrial Fibrillation, whereas lower doses are effective in Atrial Flutter
Monophasic dose
1. Synchronized: 200 joules (up to 360 joules)
2. Starting at monophasic 200 joules minimizes cummulative shock exposure
  1. Justification: 100 J dose in Atrial Fibrillation has only 50% success rate (requiring second shock)
Biphasic dose (preferred)
1. Synchronized: 150 joules (up to 200 joules)
Consider Antiarrhythmic pre-treatment prior to cardioversion in stable patients (controversial)
1. Based on anecdotal experience, may improve electrical cardioversion success rate
2. Option 1: Procainamide
  1. Procainamide 1 gram IV over 1 hour, then Synchronized Cardioversion if needed
  2. See Ottawa Aggressive Protocol in Atrial Fibrillation Cardioversion
3. Option 2: Amiodarone
  1. Amiodarone 150 mg IV, then Synchronized Cardioversion if needed

Do not use electrical cardioversion in Digoxin Toxicity (risk of malignant ventricular Arrhythmia)
Modified electrical cardioversion dosing in patients on Digoxin
1. Start at 10-20 Joules biphasic
2. Increase in 10-20 Joule increments until cardioversion

See Atrial Fibrillation Acute Management
1. Describes overall approach and disposition planning (including safe for discharge indications)
Atrial Fibrillation Anticoagulation
1. Describes indications for Anticoagulation and agents (Warfarin, Dabigatran, Oral Xa Inhibitors)
2. Expert opinion typically recommends Anticoagulation for 3 weeks following cardioversion due to myocardial stunning
  1. Increased risk of stroke in the first 3 weeks after cardioversion
See Atrial Fibrillation Rate Control
1. Discharge patient on Metoprolol Tartrate (25 mg bid) or Metoprolol Succinate (25-50 mg daily) in most cases