Safety and Efficacy of Vanoxerine for Conversion of Atrial Fibrillation or Flutter to Normal Sinus Rhythm

Inclusion Criteria: * provide written informed consent, * male or female 18 years of age or greater; women of child bearing potential must use adequate contraception * symptomatic AF/AFL for more than 3 hours and less than 7 days (168 hours), as dated by symptoms * AF/AFL documented by ECG at the start of study drug administration Exclusion Criteria: * Systolic blood pressure \<100 mmHg. * Average heart rate \<50 bpm. * Average QTcF (Fridericia correction) \>440 ms. * Average QRS interval \>140 ms. * Paced atrial or ventricular rhythm on ECG. * Serum potassium \<3.5 meq/L (may be corrected prior to randomization). * Received another intravenous Class I or Class III antiarrhythmic drug within prior 3 days. * received amiodarone (oral or IV) in prior 3 months. * Clinical evidence or history of acute coronary syndrome within 30 days prior to randomization. * Aortic stenosis with aortic valve area equal to or less than 1.0 cm2. * Rheumatic mitral stenosis with valve area of \<1.5 cm2. * Untreated hyperthyroidism. * Acute pericarditis. * AF/AFL as a result of surgery within the last 7 days * History of failed electrical cardioversion * History of polymorphic ventricular tachycardia (PVT, e.g. torsades de pointes). * History or family history of long QT syndrome. * History of ventricular tachycardia requiring drug or device therapy. * History of NYHA Heart Failure Class 3 or 4 or recent (within 1 month) onset of heart failure not related to rapid ventricular response AF. * Ejection fraction (EF) of 35% or less.