This study is designed to evaluate the safety, tolerability and preliminary efficacy of vernakalant (oral) in subjects with sustained atrial fibrillation of greater than 72 hours and less than 6 months duration

Inclusion Criteria (partial list):

• Subjects must have sustained, symptomatic atrial fibrillation for greater than 72 hours and less than 6 months duration
• Subjects must have adequate anticoagulant therapy

Exclusion Criteria (partial list):

• Subjects may not have Class III or Class IV congestive heart failure
• Subjects may not have uncorrected electrolyte imbalance