Prior data indicate that the conversion to a normal sinus rhythm by 8 hours is approximately 20%. If the investigators wish to detect a 25% change between medications then the investigators would need to include a total of 150 patients (75 in each cohort) to reject the null hypothesis that the conversion rates are equal between the 2 medications with probability (power) 0.8 and Type I error < 0.05. The investigators will use a continuity-corrected chi-squared statistic or Fisher's exact test to test our hypothesis. Power analysis performed using GPower Version 3.