This double-blind, placebo-controlled study is designed to evaluate the efficacy and safety of azimilide compared with placebo in prolonging the time to the first symptomatic arrhythmia recurrence in patients with a history of atrial fibrillation and congestive heart failure and/or ischemic heart disease) and those without these conditions. Once this phase of the study is completed, a second phase with a different study design will be conducted. The second phase is an open-label, follow-up phase. The follow-up phase of the study is designed to evaluate the long-term efficacy and safety of a daily oral dose of azimilide in patients who complete the double-blind, placebo-controlled phase of this study.