Inclusion Criteria- 18 years of age or older;
- Have an atrial arrhythmia with symptoms that has been sustained for greater than 3 hours and up to 45 days.
- Have adequate anticoagulant therapy.
Exclusion Criteria- Have a QRS > 0.14 seconds unless patient has pacemaker or uncorrected QT > 0.440 seconds as measured on a 12-lead ECG.
- Have serious diseases/illnesses that could interfere with the conduct or validity of the study or compromise patient safety.
- Have received intravenous Class I or Class III antiarrhythmic drugs or intravenous amiodarone within 24 hours prior to dosing.