What are the recommended synchronized cardioversion settings—including pad placement, energy levels, and sedation—for atrial fibrillation/flutter, atrial tachycardia, and pulseless ventricular tachycardia?

Synchronized Cardioversion Settings

For atrial fibrillation, start with 200 J biphasic using anteroposterior (AP) pad placement; for atrial flutter, use 200 J biphasic AP placement; for pulseless ventricular tachycardia, use unsynchronized defibrillation at maximum energy (not synchronized cardioversion). 1

Critical Distinction: Pulseless VT is NOT Cardioverted

Pulseless ventricular tachycardia is cardiac arrest—treat it identically to ventricular fibrillation with unsynchronized defibrillation at maximum energy (360 J monophasic or 200 J biphasic). Synchronized cardioversion is only for patients with a pulse and organized rhythms.

Energy Settings by Rhythm

Atrial Fibrillation

• Initial energy: 200 J biphasic 1
• This provides optimal balance of efficacy (approaching 90-95% success), efficiency, and safety
• If unsuccessful, escalate to maximum energy available on your defibrillator
• Biphasic waveforms are superior to monophasic (which required 300-360 J) 2

Atrial Flutter

• Initial energy: 200 J biphasic 1
• While flutter theoretically requires less energy (50-75% success at 50 J, 85-90% at 100 J), starting at 200 J is recommended because:
  • Distinguishing AF from flutter on single-lead monitoring is challenging in emergent settings
  • Higher initial energy provides shorter procedural times
  • No safety concerns with 200 J
  • Prevents undertreating misidentified AF
  • Success approaches 100% at 200 J 1

Atrial Tachycardia

• Initial energy: 100-200 J biphasic 3, 4
• Most atrial tachycardias cardiovert successfully at these energies
• Consider starting at 200 J for consistency and to avoid multiple shocks

Pad Placement

Anteroposterior (AP) position is preferred over anterolateral (AL) for all atrial arrhythmias:

• AP placement: One pad on the anterior chest (right of sternum or left precordium), one on the back between the scapulae
• AL placement: One pad right upper chest, one at cardiac apex

For persistent AF, AP positioning with biphasic truncated exponential waveform (BTE) using patches (not paddles) at maximum energy showed the highest efficacy (RR 1.35 vs. standard AP incremental) 5. Recent data for ventricular arrhythmias also supports AP placement superiority 6.

Technical Pad Considerations

• Use self-adhesive patches rather than paddles when possible—better outcomes in persistent AF 5
• Ensure firm pad-to-skin contact to minimize transthoracic impedance
• Apply active compression to pads if initial shock fails 1
• Pads should be widely separated to avoid current shunting along chest wall 3
• If shock-refractory, consider pad repositioning before repeat attempts 1

Sedation Protocol

Effective anesthesia (not merely sedation) is required to achieve amnesia and avoid pain 3:

• Preferred agents:

  • Propofol (1-2 mg/kg IV)
  • Etomidate (0.2-0.3 mg/kg IV)
  • Midazolam (0.05-0.1 mg/kg IV) 4

• Ensure adequate depth of sedation before delivering shock

• Have reversal agents available (flumazenil for benzodiazepines) 4

• Requires physician experienced in procedural sedation or anesthesia support

Synchronization Technique

• Always synchronize to R wave to avoid delivering shock during vulnerable period (T wave), which could induce ventricular fibrillation 3
• Verify synchronization markers appear on each QRS complex before delivering shock
• If synchronization fails (irregular rhythm, low amplitude QRS), reposition electrodes or change lead selection

Refractory Cases

If initial maximum-energy shock fails (shock-refractory AF):

1. Apply firm pad pressure during next shock (improves success from 87% to 93%) 1
2. Reposition pads to redirect shock vector (improves to 96%) 1
3. Consider antiarrhythmic pretreatment (amiodarone, ibutilide) to lower defibrillation threshold
4. Double synchronized cardioversion (two simultaneous shocks from separate defibrillators) may be considered but requires specialized equipment and expertise—provides only modest incremental benefit (98% vs. 96%) 1

Common Pitfalls

• Don't start with low energy for AF: While older protocols suggested 100 J initial, 200 J biphasic is now standard 1
• Don't use synchronized mode for pulseless VT: This is cardiac arrest requiring immediate unsynchronized defibrillation
• Don't use paddles when patches available: Patches provide superior outcomes for persistent AF 5
• Don't forget anticoagulation: Requires 3 weeks before and 4 weeks after cardioversion for AF/flutter ≥48 hours duration (or TEE-guided approach) 7
• Don't cardiovert multifocal atrial tachycardia: This rhythm does not respond to electrical cardioversion 4