Emergency department cardioversion of acute atrial fibrillation

We applaud Ian Stiell and colleagues¹ for their well designed and executed trial comparing two common methods of cardioversion for stable emergency department patients with acute atrial fibrillation. Their efficacy and safety results will better inform the shared decision-making conversations we undertake with our emergency department patients eligible for elective cardioversion.

We have two crucial questions to help us evaluate the translatability of the findings to patient care. First, study participants “received up to three consecutive biphasic waveform shocks. The first shock was set at 200 J but could be higher for subsequent shocks”.¹ The first shock did not restore sinus rhythm in 15% of patients (37 of 244). The protocol allowed for higher energy (>200 J) for the second and third shocks. However, many emergency departments, including ours in Spain and across the US, have only biphasic defibrillators that deliver a maximum of 200 J. This might preclude us from replicating the study’s cardioversion success rates. It would be helpful if the authors could report the number of cases that received energy levels over 200 J.

Second, pretreatment with intravenous procainamide has not been shown to have clinical benefit with monophasic direct-current (DC) cardioversion of patients with atrial fibrillation.^2,3 This study found similar results in patients receiving biphasic DC cardioversion: the procainamide pretreatment group was no more responsive to DC cardioversion than those without pretreatment. This result disconfirmed the authors’ hypothesis as mentioned in their appendix. We would like to know how the authors interpreted these results.