Class III antiarrhythmic agents have been reported to be useful in maintaining sinus rhythm in patients with recurrent symptomatic atrial fibrillation or with chronic atrial fibrillation recently cardioverted to sinus rhythm. Kochiadakis and associates conducted a randomized, double-blind study to compare the safety and efficacy of amiodarone and sotalol, two class III antiarrhythmic drugs, in the treatment of patients with recurrent symptomatic atrial fibrillation.

Seventy patients who were admitted to the emergency department with symptomatic chronic or paroxysmal atrial fibrillation were included in the study. Exclusion criteria were acute myocardial infarction occurring less than one week before entry into the trial, significant comorbidities such as decreased ejection fraction, unstable hepatic or renal function or hyperthyroidism. Patients who had a life expectancy of less than one year due to to a major medical problem were also excluded from the study.

After restoration of sinus rhythm, eligible patients were randomly assigned to receive either amiodarone or sotalol. Amiodarone was initiated with a loading dose of 800 to 1,600 mg per day for seven to 14 days orally and then tapered to a maintenance dosage of 200 mg per day. Patients randomized to sotalol began therapy with 80 mg twice daily; this dosage was titrated up to a maximum dosage of 360 mg twice daily. If adverse effects were noted by the patient or if the rate-corrected QT interval was more than 0.5 seconds, the maintenance dosage of sotalol was lowered accordingly.

The success rate was high for both drugs. Other studies have shown that just 25 percent of patients who converted to sinus rhythm remain so after one year without antiarrhythmic therapy. At one year follow-up in this study, 71 percent of the patients who received amiodarone were still in sinus rhythm, compared with 40 percent of those who received sotalol. Results were not affected by age, sex, left atrial size, fibrillation pattern or underlying cardiac disease.

The authors conclude that amiodarone and sotalol are equally safe when administered over a one-year period. Amiodarone appears to be more effective than sotalol in preventing the recurrence of symptomatic atrial fibrillation. Few patients discontinued therapy with either drug because of adverse effects, although further studies using greater numbers of patients and longer follow-up periods are recommended.