The primary objective of the study is to demonstrate the superiority of vernakalant injection over amiodarone injection in the conversion of atrial fibrillation (AF) to sinus rhythm (SR) within 90 minutes of the start of drug administration. The secondary objective is to compare the safety of vernakalant to amiodarone.

This is a double-blind, active-controlled, double-dummy, multi-center, randomized trial in subjects with symptomatic AF of 3 to 48 hours duration.

Subjects will be randomized to receive vernakalant injection or amiodarone injection in a 1:1 ratio.

Safety will be assessed through the monitoring of adverse events, vital signs, continuous telemetry monitoring, 12-lead Holter monitoring, 12-lead ECGs, and laboratory tests.

At 2 hours after the start of infusion, electrical cardioversion may be performed or rate control medication may be administered. Class I and Class III antiarrhythmics are not to be administered for 24 hours after the start of infusion.

Subjects are to remain in the clinic for at least 6 hours after the start of infusion. Subjects will attend a follow-up visit at 7 (±2) days after treatment and will receive a follow-up telephone call at 30 (±3) days for assessment of serious adverse events, concomitant medications related to serious adverse events, and recurrence of AF.

All roles were blinded with the exception of each site's designated unblinded personnel who were responsible for randomization and preparation, dispensation and accountability of the study medication.

Expanded Access was not available through this protocol.

Key Inclusion Criteria:

• Have symptomatic AF of 3 to 48 hours duration at baseline.
• Be eligible for cardioversion.
• Have adequate anticoagulation therapy for cardioversion in accordance with standard of practice as recommended by ACC/AHA/ESC guidelines [1].
• Be hemodynamically stable and have systolic blood pressure (BP) above 100 mmHg and less than 160 mmHg and diastolic BP less than 95 mmHg at screening and baseline.

Key Exclusion Criteria:

• Known or suspected prolonged QT or uncorrected QT interval of >440 msec as measured at screening on a 12 lead ECG, familial long QT syndrome, or previous torsades de pointes, ventricular fibrillation; or sustained ventricular tachycardia (VT).
• Symptomatic bradycardia, sick sinus syndrome, or ventricular rate less than 50 beats per minute (bpm) as documented by 12-lead ECG at screening.
• A QRS interval >140 msec.
• Atrial flutter.
• Significant valvular stenosis, hypertrophic obstructive cardiomyopathy, restrictive cardiomyopathy or constrictive pericarditis.
• Documented previous episodes of second or third degree atrioventricular (AV) block.
• Had a myocardial infarction (MI), acute coronary syndrome or cardiac surgery within 30 days prior to entry into the study.
• Uncorrected electrolyte imbalance of serum potassium or magnesium. Both K+ and Mg2+ must be corrected prior to dosing.