Recent-onset atrial fibrillation, defined as an onset within one week, is a major issue in clinical practice, and recent advances have shown that cardioversion to normal sinus rhythm provides better patient outcomes. Cardio-version can be attempted with electric and pharmacologic methods. Immediate electric cardioversion is indicated in patients with recent-onset atrial fibrillation with a rapid ventricular response who have evidence of acute myocardial ischemia, symptomatic hypotension, angina, or heart failure that does not respond to pharmacologic interventions. In all other cases, pharmacologic cardioversion can be attempted. Medications available for cardioversion include the class I and III antiarrhythmic drugs. Class Ic medications such as propafenone and flecainide have been shown to be effective therapeutic options. Amiodarone, a class III agent, also has been shown to be effective in treating this cardiac disease; however, it is not approved by the U.S. Food and Drug Administration for treating this arrhythmia. To evaluate amiodarone, Chevalier and colleagues compared the safety and efficacy of this medication in the treatment of recent-onset atrial fibrillation.

The study design was a meta-analysis of randomized trials on the treatment of recent-onset atrial fibrillation comparing amiodarone with placebo and the class Ic drugs. The database search included MEDLINE, EMBASE, and the Cochrane Controlled Trials Register. The trial had to be a prospective, randomized trial of amiodarone versus placebo or a class Ic antiarrhythmic medication. The main outcome measure was rate of cardioversion within 24 hours. Other data collected included rates of cardioversion at one to two, three to five, and six to eight hours. Mortality and adverse events also were analyzed.

There were six studies that compared amiodarone to placebo, and seven studies compared it to the class Ic antiarrhythmics, for a total of 1,174 patients. The results showed that there was no difference between amiodarone and placebo with regard to cardioversion rates at one to two hours, but there was a significant improvement in cardioversion rates with amiodarone after six to eight hours. The class Ic medications had a significantly better rate of cardioversion than amiodarone for up to eight hours, but there was no difference between the two groups at 24 hours. The adverse events were minimal in all of the studies, with no deaths reported in any of the treatment groups.

The authors conclude that amiodarone is as safe and effective as the class Ic antiarrhythmic medications at 24 hours in cardioversion of recent-onset atrial fibrillation. It provides an alternative for patients who are not candidates for the more rapid-acting antiarrhythmic medication, such as those with ventricular dysfunction and ischemic heart disease, in whom rapid cardioversion is not required. They also state that these data were based on intravenous amiodarone and further studies need to be done using the oral preparation, to establish the optimal dose, and to determine when to start outpatient treatment.