This study is being conducted to demonstrate the effectiveness of RSD1235 in the conversion of atrial fibrillation to sinus rhythm.

There are approximately 2 million reported prevalent cases of atrial fibrillation (AF) and atrial flutter in the United States (Heart Disease & Stroke Statistics - 2003 Update, AHA). These arrhythmias may be occasional or sustained. While not directly fatal, these arrhythmias cause discomfort and can lead to stroke or congestive heart failure.

This Phase III trial is Cardiome's first pivotal study with RSD1235. The study seeks to confirm the findings of the Phase II proof-of-concept through demonstration of RSD1235's abilities to convert AF to sinus rhythm. The patient population will include recent onset AF (AF duration of 3 hours to 7 days) and patients with longer AF duration.

This is a double-blind, placebo-controlled, randomized study in patients with AF; stratification will be based on duration of AF. Treatment will be considered successful if there is a treatment-induced conversion of atrial arrhythmia to sinus rhythm for a minimum of 1-minute by Hour 1.5 (Time 0 = start of first infusion). All patients will be evaluated for safety.

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.