Safety Study of Tecadenoson to Treat Atrial Fibrillation

Inclusion Criteria: * Have a diagnosis of atrial fibrillation in need of treatment for rate control * Be able and willing to abstain from any antiarrhythmics, including atrioventricular (AV) nodal blocking agents (except for esmolol per protocol), from no later than 8:00 p.m. on the day prior to dosing until completion of the last dose period assessment * Be able and willing to abstain from xanthine- or chocolate-containing foods, beverages, and medications * Females must be post-menopausal or sterilized; or if of childbearing potential, must not be breastfeeding and must have a negative pregnancy test at screening and no intention of becoming pregnant during the course of the study. Males and females must be using adequate contraception during the study. Exclusion Criteria: * Have a known accessory pathway * Have active myocardial ischemia or recent acute coronary syndrome * Have acute or overt heart failure, bradycardia, heart block greater than first degree, or cardiogenic shock * Have allergies or contraindications to treatment with esmolol or aminophylline, or any of their constituents * Have a supine cuff systolic blood pressure \< 90 mm Hg * Be undergoing treatment with theophylline/aminophylline preparations, Trental® (pentoxifylline), or carbamazepine * Have asthma or other reactive airways disease currently on-treatment * Have a history of an active or chronic pancreatic disease or clinically significant increased levels of serum amylase or lipase