Alternative in Beta Blocker Intolerance: The ABBI Trial

Inclusion Criteria: * Age ≥ 21 * Male or female who is post-menopausal or not pregnant and using an approved contraceptive regimen * Previous beta blocker use and intolerant of beta blocker Exclusion Criteria: * Systolic blood pressure \< 100 mmHg unless another blood pressure medication is stopped at the time of study entry * Hospitalized for heart failure within the past 4 weeks * Bradycardia with a heart rate \< 60 * Heart block greater than first degree * History of sick sinus syndrome (unless a permanent pacemaker is in place) * History of severe hepatic or renal dysfunction; serum Creatinine \> 2.0 or Amylase \> 3x normal * Use of CYP2D6 inhibitors (quinidine, propafenone, fluoxetine, paroxetine, etc.) * Ingestion of investigational drug within the past 30 days