Synchronized cardioversion

See critical care quick reference for doses by weight.


  • Low energy shock synchronized with peak of QRS complex
  • Machine leads synchronized with patient's EKG rhythm


It is important to note that the procedure and indications differ between defibrillation and cardioversion

Defibrillation (Unsynchronized Cardioversion)

Synchronized Cardioversion


  • None

Equipment Needed

  • Defibrillator
  • Consider sedation medication in conscious patient (e.g. etomidate, ketamine), but do not delay procedure in unstable patient
    • Give fentanyl 1 μg/kg before sedation, and consider slow 0.5 mg/kg lidocaine IV 1 min before sedative
    • Etomidate superior to propofol in terms of recovery and hemodynamic stability[1]
      • Etomidate 0.1 mg/kg, followed by etomidate second dose of 0.05 mg/kg just prior to shock
      • VS propofol 1 mg/kg, followed by propofol second dose of 0.5 mg/kg just prior to shock



  • Apply pads
    • Anterior-Posterior placement is preferred [2] but may not be as important as previously thought and most studies are for atrial fibrillation or flutter [3]
      • Avoid placing in close proximity to implanted devices if possible [4]
  • Select appropriate energy (Joules)
  • Ensure machine is "synced" before each discharge
    • Most machines show an indicator (arrow or dot) above each beat if appropriately synchronized
  • Ensure R or S wave is bigger than T wave
    • Machine may read T wave as depolarization and shock during an actual repolarization phase
    • May induce shock on T and subsequent VT/VF
    • Move leads to avoid this
  • Give sedation, if indicated
    • All awake and hemodynamically stable patients
  • Ensure safety of environment prior to cardioversion
    • Nobody touching patient
    • Nobody touching equipment that is touching patient
    • Consider removing supplemental oxygen
  • Cardiovert
    • Hold 'Shock' button until shock discharged
      • Shock delayed until peak of QRS complex in synchronized cardioversion (keep holding button down)
  • Repeat PRN
    • May require escalating energy


Initial recommendations:

  • Tachycardia with pulse
    • Narrow regular (SVT): 50-100 J
    • Narrow irregular (A fib, A flutter)
      • Biphasic: 120-200 J (may start as low as 50 - 100 J for A flutter)
      • Monophasic: 200 J
    • Wide regular (VT with pulse): 100 J
    • Wide irregular: defibrilate (NOT synchronized)


See Also

External Links




  • AHA 2010 ACLS Recommendations
  1. Desai PM, Kane D, Sarkar MS. Cardioversion: What to choose? Etomidate or propofol. Ann Card Anaesth. 2015;18(3):306–311. doi:10.4103/0971-9784.159798.
  2. Kirchhof P et al. Anterior-posterior versus anterior-lateral electrode positions for external cardioversion of atrial fibrillation: A randomised trial. Lancet 2002 Oct 26; 360:1275-9
  3. Kirkland S et al. The efficacy of pad placement for electrical cardioversion of atrial fibrillation/flutter: A systematic review. Acad Emerg Med. 2014 Jul;21(7):717-26
  4. Manegold J. External cardioversion of atrial fibrillation in patients with implanted pacemaker or cardioverter-defibrillator systems: A randomized comparison of monophasic and biphasic shock energy application. European Heart Journal, 28(14);1731–1738