What is the recommended number of attempts for standard cardioversion?

Recommended Number of Attempts for Standard Cardioversion

For standard cardioversion of atrial fibrillation, it is recommended to make multiple attempts if the initial cardioversion is unsuccessful, with electrode repositioning and/or increasing energy between attempts. 1

General Cardioversion Protocol

• Initial cardioversion should be performed with adequate energy (200J or greater with biphasic defibrillators) for atrial fibrillation 1, 2
• If the first attempt is unsuccessful, repeat cardioversion attempts may be made after:
  • Adjusting the location of the electrodes 1
  • Applying pressure over the electrodes 1
  • Administering an antiarrhythmic medication 1
  • Increasing the energy output in increments (up to maximum available energy) 1, 2

Number of Attempts

• The guidelines do not specify a maximum number of attempts, but rather recommend repeated attempts as long as adjustments are made between attempts 1
• The interval between consecutive shocks should not be less than 1 minute to avoid myocardial damage 1
• It is reasonable to perform repeated cardioversion procedures in patients with persistent AF, provided that sinus rhythm can be maintained for a clinically meaningful period between procedures 1

Improving Success Rates

• Consider alternative electrode placement if initial position is unsuccessful:
  • Anteroposterior or base-apex locations are standard 2
  • A more superoanterior left paddle position may be more effective for atrial fibrillation 2
• Energy considerations:
  • Start with at least 200J for atrial fibrillation (biphasic) 1, 2
  • Increase energy successively in increments up to maximum available energy 1
• Antiarrhythmic medications before subsequent attempts:
  • Amiodarone, flecainide, dofetilide, propafenone, or ibutilide can be considered to lower defibrillation threshold 1
  • Starting pharmacological therapy before cardioversion enhances immediate success and suppresses early recurrences 1

Special Considerations

• For refractory cases that don't respond to standard external cardioversion:
  • Internal cardioversion may be considered as an alternative approach with higher success rates (91% vs 67% in one study) 3
  • Double sequential cardioversion may be considered for difficult cases 2
• Success rates of cardioversion protocols can be significantly improved with standardized approaches (one study showed improvement from 91.8% to 99.2% with a structured protocol) 4

Potential Complications

• Monitor for ventricular arrhythmias, asystole, and transient myocardial depression 2
• Ensure appropriate anticoagulation before, during, and after cardioversion to prevent thromboembolic events 1
• When using antiarrhythmic drugs in conjunction with cardioversion, monitor for QT prolongation and risk of torsades de pointes for 24-48 hours post-procedure if using QT-prolonging medications 1

Remember that while multiple attempts are reasonable, the likelihood of maintaining sinus rhythm decreases with each recurrence of atrial fibrillation, and a rate control strategy may eventually be more appropriate for patients with multiple recurrences 5.