Secondary Hypotheses: To compare the three therapies in regard to: 1. Frequency of episodes of major and minor strokes. 2. Frequency of episodes of major and minor bleeds. 3. Frequency of sudden death, cardiac mortality, and total mortality. 4. Frequency of life-threatening pro-arrhythmic reactions. 5. Frequency of episodes of congestive heart failure. 6. Frequency of side effects necessitating discontinuation of therapy. 7. Frequency and mean duration of hospitalization directly related to atrial fibrillation or flutter. 8. Mean change in maximal exercise capacity on treadmill during atrial fibrillation or flutter versus sinus rhythm. 9. Time to the development of sinus rhythm from randomization to day 28 of the study. 10. Mean duration of the intervals between occurrences of atrial fibrillation or flutter after day 28. 11. The mean ventricular response documented on electrocardiogram (ECG) recordings during occurrences of atrial fibrillation or flutter after day 28. 12. Changes in health-related quality of life as measured by the SF-36 and an atrial fibrillation quality of life questionnaire. 13. Time to first occurrence of atrial fibrillation or flutter after day 28 or cessation of treatment due to adverse drug reactions after randomization.