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Pharmacological- and electrical-first cardioversion worked similarly well for treating acute atrial fibrillation (Afib) in the emergency department, according to the Canadian .

The 204 people randomized to IV procainamide (plus electrical cardioversion if necessary, with up to three shocks) showed a 96% rate of conversion to sinus rhythm that was maintained for at least 30 minutes, reported researchers led by Ian Stiell, MD, of The Ottawa Hospital in Ontario.

Similarly, the shock-only arm (192 people getting electrical conversion alone) had sinus rhythm restored in 92% (P=0.07), the authors showed in a .

"Although the drug-shock group had more adverse events, most were transient hypotension, and none were serious. After 14 days, no patients had had a stroke, one had died because of an unrelated condition, and 95% were still in sinus rhythm," according to the investigators.

"The most important finding from this study is that either approach to immediate in the emergency department leads to a very high proportion of patients being discharged in sinus rhythm without serious adverse events. Patients can be rapidly cardioverted in the emergency department, resolving their acute symptoms and enabling discharge home. This avoids unnecessary hospital admission or next-day re-evaluation by cardiologists," Stiell and colleagues concluded.

By administering the class IA antiarrhythmic over just 30 minutes and using a weight-based dosing (15 mg/kg), site investigators reported that procainamide infusion alone converted 52% of patients in a median 23 minutes without need for sedation or electrical cardioversion -- a potential advantage of a drug-first strategy.

"Nevertheless, the choice between pharmacological and electrical cardioversion should be a shared decision between the patient and the physician," the authors said.

"The most important finding of this study is that both the drug-shock and shock-only strategies are equally highly effective. The question of how to decide which strategy to use in each individual patient therefore remains," agreed Giorgio Costantino, MD, of Fondazione IRCCS Ca' Granda-Ospedale Maggiore Policlinico, and Monica Solbiati, MD, PhD, of Università degli Studi di Milano, both of Milan, Italy.

In an accompanying commentary, the pair said that one cannot be so sure that pharmacological cardioversion has the advantage of being safer than electrical shocks, as only one patient in the shock-only group had a serious adverse outcome (due to an absence of synchronization during the electrical cardioversion), whereas several patients in the drug-shock group had mild adverse events.

"Therefore, it is not known whether the drug-shock approach requires less monitoring of patients than the shock-only approach," Costantino and Solbiati commented.

RAFF2 was a partial factorial randomized trial of 396 adults with acute Afib who had presented to one of 11 academic hospital emergency departments in Canada. Mean patient age was 60, two-thirds were men, and the group as a whole presented within ten hours from Afib onset on average.

Beyond the randomization to drug-shock or shock-only protocols, those having electrical cardioversion were also placed in a nested, randomized comparison of anteroposterior versus anterolateral pad positions.

Stiell's group found no significant difference between the two pad positions for electrical cardioversion.

On subgroup analysis, they found that the procainamide-first strategy was more effective for patients with a first Afib episode and for those younger than 70 years.

"We acknowledge that we missed eligible patients because research staff could not always be present during off hours," Stiell and colleagues wrote.

Another limitation of RAFF2 was that the 14-day follow-up could have missed subsequent thromboembolic events. However, according to the authors, "our ongoing 6-month and 12-month follow-ups have not shown this to be the case."

Finally, the choice to study IV procainamide means that the results may not be generalizable to other antiarrhythmic drugs and the countries that prefer them, Costantino and Solbiati suggested.

"The potential advantage of using flecainide or propafenone for pharmacological cardioversion is that the clinician could assess the efficacy of these drugs and prescribe them for long-term maintenance of sinus rhythm," they said. "However, class IA and IC antiarrhythmic drugs are similarly effective for cardioversion, so the study findings could potentially be extended to class IC drugs."