The purpose of this study is to determine the safety and efficacy of an investigational antiarrhythmic drug (ATI-2042) in the treatment of atrial fibrillation in patients with a dual chamber pacemaker.

ATI-2042 is being developed as an alternative to amiodarone, which is considered a first-line therapy for patients with atrial fibrillation and is known to have serious side effects. ATI-2042 was designed to have a reduced plasma half-life and a lower volume of distribution, which is expected to result in an improved safety profile. In contrast to amiodarone, ATI-2042 undergoes rapid metabolism via plasma and tissue esterases, which may reduce tissue accumulation and toxicity. The current trial will determine if ATI-2042 retains the efficacy profile of amiodarone without the side effects attributable to tissue accumulation seen with long-term dosing.

This study is an early phase trial and some specific protocol information is proprietary and not publicly available at this time. (Full information is available to trial participants.)

Inclusion Criteria:

• Proven paroxysmal atrial fibrillation
• Pacemaker with appropriate AF diagnostics and recording capabilities

Exclusion Criteria:

• Known allergy to Amiodarone or previous treatment for severe Amiodarone toxicity
• Cardioversion within one month of screening
• Severe left ventricular dysfunction or CHF with NYHA Class III or above