Procedure

Synchronized Cardioversion

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Synchronized Cardioversion, Synchronized Shock

  • See Also
  1. Defibrillation
  • Indications
  1. Paroxysmal Supraventricular Tachycardia
  2. Atrial Fibrillation
  3. Atrial Flutter
  4. Ventricular Tachycardia
  • Protocol
  • Sedation Prior to Cardioversion
  1. See Procedural Sedation
  2. Combination Protocol: Etomidate and Fentanyl
    1. Etomidate 0.15 to 0.2 mg/kg and
    2. Fentanyl: 1 mcg/kg/dose up to 50 mcg/dose every 3 minutes, titrating to effect
  3. Combination Protocol: Midazolam and Fentanyl
    1. Midazolam 1 mg IV every 3-5 minutes up to adequate sedation or to maximum 5 mg cummulative dose and
    2. Fentanyl 50 mcg increments
    3. Hypotension risk
  4. Propofol Protocol
    1. Considered superior agent if patient stable
      1. Short induction
      2. Rapid awakening and recuperation
      3. Minimal adverse effects (although risk of Hypotension)
    2. Anesthesia or second provider supervision is recommended
    3. References
      1. Coll-Vinent (2003) Ann Emerg Med 42:767-72 [PubMed]
      2. Basset (2003) Ann Emerg Med 42:773-82 [PubMed]
  • Technique
  • Electrode (paddle) position
  1. Anteroposterior electrodes most effective in Atrial Fib
    1. Anteroposterior placement conversion rate: 96%
    2. Anterolateral placement conversion rate: 78%
    3. Kirchhof (2002) Lancet 360:1275-9 [PubMed]
  2. Avoid placing directly over implanted device (internal Defibrillator or Pacemaker)
    1. Contrast with Defibrillation, where paddles may be positioned over implanted device to prevent delays
  3. In refractory cases, electophysiologists may apply pressure to the anterior electrode during cardioversion shock
    1. This may increase cardioversion efficacy by reducing distance between the anterior and posterior electrode
    2. Place 2 towels on the anterior pad, stand on a step stool and apply pressure to the anterior pad
    3. Biphasic devices appear to be safe despite contact with examiner as they apply pressure to the pads
  • Dosing
  1. Pediatric
    1. Initial: 0.5 Joule per kg
    2. Subsequent: 1 Joule per kg
  2. Adult
    1. Background
      1. Cardioversion is often performed at maximal biphasic joules (e.g. 200 J) to limit number of shocks
      2. Joules listed below are a historical guideline, but starting at lower joules may require additional attempts
      3. Myocardium is "stunned" after each shock, and this adverse effect increases with cummulative shocks
    2. Narrow regular Tachycardia (PSVT, Atrial Flutter)
      1. Initial: 50-100 J (monophasic or biphasic)
    3. Narrow irregular Tachycardia (Atrial Fibrillation)
      1. See Atrial Fibrillation Cardioversion
      2. Initial Monophasic: 200 J synchronized (up to 360 J synchronized)
      3. Initial Biphasic: 150 J synchronized (up to 200 J synchronized)
      4. Consider Amiodarone 150 mg prior to cardioversion if stable
        1. Anecdotal evidence of improved success in electrical cardioversion of Atrial Fibrillation
      5. Unfractionated Heparin or Low Molecular Weight Heparin indications
        1. Atrial Fibrillation of unknown duration or >48 hours (emergent, unstable cases requiring immediate cardioversion) or
        2. High risk of Cerebrovascular Accident (e.g. prior TIA or CVA, Rheumatic Heart Disease, Mechanical Heart Valve)
          1. See CHADS2-VASc Score
    4. Wide regular Tachycardia (Ventricular Tachycardia)
      1. Initial: 100 J (monophasic or biphasic)
    5. Wide irregular Tachycardia
      1. Defibrillation (non-synchronized)
  1. Do not use electrical cardioversion in Digoxin Toxicity (risk of malignant ventricular Arrhythmia)
  2. Modified electrical cardioversion dosing in patients on Digoxin
    1. Start at 10-20 Joules biphasic
    2. Increase in 10-20 Joule increments until cardioversion