What is the procedure for electrically cardioverting atrial fibrillation (afib)?

Electrical Cardioversion for Atrial Fibrillation

Synchronized direct current electrical cardioversion is the most effective method for converting atrial fibrillation to sinus rhythm and is the treatment of choice in hemodynamically compromised patients with new-onset AF. 1

Indications for Electrical Cardioversion

• Immediate electrical cardioversion is recommended for patients with AF who have:

  • Ongoing myocardial ischemia 1
  • Symptomatic hypotension 1
  • Angina not responding to pharmacological measures 1
  • Heart failure not responding promptly to pharmacological measures 1
  • Pre-excitation (WPW syndrome) with very rapid tachycardia or hemodynamic instability 1, 2

• Electrical cardioversion is also indicated in stable patients when:

  • Symptoms of AF are unacceptable to the patient 1
  • As part of a long-term rhythm control management strategy 1
  • As a diagnostic tool to assess if restoration of sinus rhythm improves symptoms or left ventricular function 1

Pre-Cardioversion Requirements

• Anticoagulation is mandatory before cardioversion if:

  • AF duration is >24 hours or unknown 1, 2
  • Patient has risk factors for thromboembolism 1, 2

• Anticoagulation options before cardioversion:

  • Therapeutic anticoagulation for at least 3 weeks before cardioversion 1, 2
  • Direct oral anticoagulants (DOACs) are preferred over vitamin K antagonists 1, 2
  • Alternatively, transesophageal echocardiography (TEE) can be performed to exclude left atrial thrombus 1, 2

Technical Aspects of Electrical Cardioversion

• Procedure setup:

  • Synchronized direct current shock must be R-wave synchronized 1
  • Patient should be adequately sedated with intravenous midazolam and/or propofol 1
  • Continuous monitoring of blood pressure and oxygen saturation is essential 1

• Electrode placement and energy settings:

  • Use electrode paddles with diameter of 8-12 cm 1
  • Biphasic defibrillators are more effective than monophasic ones 1
  • Position electrodes anteriorly over the right upper sternum and laterally over the cardiac apex or in anteroposterior position 1
  • Ensure proper skin contact using electrolyte-impregnated pads to minimize electrical resistance 1
  • Deliver shock during expiration when thoracic impedance is lower 1

• Energy protocol:

  • Start with higher energy levels when using biphasic waveforms (150-200J) 1
  • If first shock fails, increase energy for subsequent shocks 1
  • Have atropine, isoproterenol, or temporary transcutaneous pacing available to manage post-cardioversion bradycardia 1

Post-Cardioversion Management

• Anticoagulation:

  • Continue anticoagulation for at least 4 weeks after successful cardioversion 1, 2
  • Long-term anticoagulation should be based on the patient's thromboembolic risk (CHA₂DS₂-VASc score) regardless of rhythm outcome 1, 2

• Antiarrhythmic drugs:

  • Consider antiarrhythmic drugs to maintain sinus rhythm after cardioversion 1
  • Options include amiodarone, flecainide, propafenone, dronedarone, or sotalol based on patient characteristics 1, 3
  • In case of early recurrence, repeated cardioversion with antiarrhythmic medication should be considered 1

Common Pitfalls and Considerations

• Avoid frequent repetition of cardioversion in patients with short periods of sinus rhythm between relapses despite antiarrhythmic therapy 1

• Contraindications to electrical cardioversion:

  • Digitalis toxicity 1
  • Hypokalemia 1
  • Performing cardioversion without appropriate anticoagulation when AF duration >24 hours 1

• Potential complications:

  • Skin burns at electrode sites 1
  • Post-cardioversion bradycardia 1
  • Thromboembolism (highest risk within first few days after cardioversion) 2, 4
  • Immediate reinitiation of AF 3, 4

• Special considerations:

  • For patients with pre-excited AF (WPW), avoid adenosine, digoxin, and non-dihydropyridine calcium channel blockers as they can accelerate ventricular rate 2
  • In patients with hypertrophic cardiomyopathy, anticoagulation is indicated regardless of CHA₂DS₂-VASc score 2

By following this structured approach to electrical cardioversion of atrial fibrillation, you can maximize success rates while minimizing complications and improving patient outcomes.