What is the recommended approach for cardioversion in patients with arrhythmias?

Cardioversion for Patients with Arrhythmias

Immediate direct-current (DC) cardioversion is recommended for patients with atrial fibrillation who have hemodynamic instability, ongoing myocardial ischemia, or symptomatic hypotension. 1

Initial Assessment and Approach

Hemodynamic Status

• Unstable patients: Immediate synchronized DC cardioversion without delay
• Stable patients: Choice between pharmacological or electrical cardioversion based on:
  • Duration of arrhythmia
  • Type of arrhythmia
  • Presence of structural heart disease
  • Patient preference

Anticoagulation Requirements

For AF duration < 48 hours:

• Start anticoagulation at presentation (LMWH or UFH at full treatment doses)
• Proceed with cardioversion without delay 1

For AF duration > 48 hours or unknown duration:

• Therapeutic anticoagulation for at least 3 weeks before cardioversion, OR
• Transesophageal echocardiography (TEE) to rule out left atrial thrombus 1
• Continue anticoagulation for at least 4 weeks after cardioversion 1
• Long-term anticoagulation based on CHA₂DS₂-VASc score 2

Electrical (DC) Cardioversion

Indications:

1. Hemodynamically unstable patients
2. When rapid restoration of sinus rhythm is necessary
3. When pharmacological cardioversion has failed
4. Patient preference in stable patients

Technique:

• Synchronized shock (R-wave synchronized)
• Start with appropriate energy level (typically 120-200J for biphasic defibrillators)
• Higher energy settings (≥200J) are associated with fewer tachyarrhythmic complications 3
• Position electrodes anteroposteriorly or anterolaterally

Contraindications:

• Digitalis toxicity
• Hypokalemia
• Absence of appropriate anticoagulation (relative)

Pharmacological Cardioversion

First-line agents:

• Flecainide or propafenone: For patients without structural heart disease, severe LV hypertrophy, or coronary artery disease 1
• Amiodarone: For patients with heart failure, coronary artery disease, or structural heart disease 1
• Vernakalant: For recent-onset AF without severe structural heart disease 1

"Pill-in-the-pocket" approach:

• Single oral dose of flecainide or propafenone
• Only for selected patients with:
  • No sinus or AV node dysfunction
  • No bundle branch block
  • No QT prolongation
  • No Brugada syndrome
  • No structural heart disease
• Prior beta-blocker or non-dihydropyridine calcium channel blocker administration recommended 1

Medications to avoid:

• Digoxin and sotalol: May be harmful when used for pharmacological cardioversion 1
• Quinidine, procainamide, disopyramide, and dofetilide: Should not be started out-of-hospital 1

Special Considerations

Pre-excited AF (WPW syndrome):

• Avoid AV nodal blocking agents (beta blockers, calcium channel blockers, digoxin, adenosine)
• Use procainamide or ibutilide 2

Heart failure patients:

• Amiodarone is the preferred agent for pharmacological cardioversion 1
• DC cardioversion is highly effective and safe

Recurrent AF after cardioversion:

• Consider pretreatment with antiarrhythmic drugs before repeat cardioversion 1
• Amiodarone, flecainide, ibutilide, propafenone, or sotalol can enhance success 1
• Consider catheter ablation for symptomatic recurrent AF 2

Common Pitfalls and Caveats

1. Inadequate anticoagulation: Ensure INR ≥2.5 at the time of cardioversion if duration is uncertain or >2 days to prevent thromboembolism 4

2. Overlooking atrial flutter risk: Atrial flutter carries similar thromboembolic risk as AF and requires the same anticoagulation approach 4

3. Inappropriate medication selection: Using class IC drugs (flecainide, propafenone) in patients with structural heart disease can increase mortality

4. Post-cardioversion monitoring: Watch for:

   • Bradycardia or sinus arrest (occurs in ~1% of cases)
   • Early recurrence of AF
   • Thromboembolic events

5. Frequent repetition of cardioversion: Not recommended for patients with short periods of sinus rhythm between relapses despite antiarrhythmic therapy 1

By following this structured approach to cardioversion, clinicians can optimize outcomes while minimizing risks for patients with atrial arrhythmias.