What joules should be used for synchronized electrical cardioversion in an unstable adult with atrial fibrillation or atrial flutter?

Recommended Energy for Synchronized Cardioversion in Unstable AF/Atrial Flutter

For unstable atrial fibrillation or atrial flutter requiring immediate cardioversion, use 120-200 J for AF with biphasic waveforms, but atrial flutter requires much lower energy—typically 50-100 J initially, and often succeeds with as little as 5-50 J. 1, 2

Energy Recommendations by Rhythm Type

Atrial Flutter (Lower Energy Required)

• Start with 50-100 J for atrial flutter using biphasic waveforms, increasing stepwise if the initial shock fails 1
• Atrial flutter responds to markedly lower energies than atrial fibrillation—monophasic shocks of 5-50 J are usually sufficient, and biphasic waveforms often succeed with even less energy 2
• Research confirms that the average cardioversion threshold for atrial flutter using biphasic waveforms is only 33.2 J (median 20 J), with success rates of 95-100% 3, 2

Atrial Fibrillation (Higher Energy Required)

• Use 120-200 J as the initial biphasic energy dose for atrial fibrillation, increasing stepwise if unsuccessful 1
• If using monophasic waveforms, begin at 200 J and increase stepwise 1
• Research shows the average biphasic cardioversion threshold for AF is 70.6 J (median 50 J), significantly lower than the 193.4 J required for monophasic waveforms 3

Critical Clinical Context

When to Cardiovert Immediately

• Perform immediate synchronized cardioversion without delay in any patient with hemodynamic instability, including hypotension, acute heart failure, ongoing chest pain/myocardial ischemia, or altered mental status 1, 2
• Do not delay for IV access or sedation if the patient is extremely unstable 1

Important Caveats

• Ensure the defibrillator is in synchronized mode to avoid shock delivery during the vulnerable period, which could induce ventricular fibrillation 1
• If synchronization is impossible, use high-energy unsynchronized shocks (defibrillation doses) 1
• Establish IV access and provide sedation when possible before cardioversion in conscious patients 1

Special Consideration: Pre-excited Atrial Fibrillation

• Patients with Wolff-Parkinson-White syndrome and atrial fibrillation/flutter typically present with very rapid heart rates and require emergent electrical cardioversion 1
• Never use AV nodal blocking agents (beta-blockers, calcium channel blockers, digoxin, adenosine) in these patients, as they can precipitate ventricular fibrillation 1, 2