The purpose of this study is to demonstrate the safety and efficacy of RSD1235 compared to placebo in the conversion of atrial arrhythmia to sinus rhythm in subjects following valvular and/or coronary artery bypass graft surgery.

This multi-national, multi-center study is a double blind, randomized, placebo-controlled trial with 2 parallel treatment arms (1 active, 1 placebo) to assess the conversion efficacy and safety of 2 intravenous doses of RSD1235 in subjects with atrial fibrillation or atrial flutter following valvular and/or coronary artery bypass graft (CABG) surgery.

Inclusion Criteria:

• Documented atrial arrhythmia after valvular and/or coronary artery bypass graft surgery

Exclusion Criteria:

• Unstable Class IV heart failure