Diltiazem in the Treatment of Atrial Fibrillation or Atrial Flutter With Rapid Ventricular Rate

Inclusion Criteria: * Age \> 18 years or older * Able to provide informed consent * Primary diagnosis AFF with RVR greater than or equal to 120 bpm Exclusion Criteria: * Pregnancy defined as a positive urine HCG * Hemodynamically unstable patients (SBP \<90, MAP \<65) * Stated history of systolic heart failure with reduced ejection fraction (\<40%) or evidence of acute heart failure or reduced EF (peripheral edema, JVD, pulmonary edema) on clinical exam or bedside echo * Patients with left ventricular assist device * Sinus node dysfunction or preexcitation with accessory pathway (known diagnosis of SVT, WPW or sick sinus syndrome. Delta waves or other evidence of accessory pathway on EKG) * 2nd or 3rd degree atrioventricular block * Allergy or sensitivity to any study drugs * Previously enrolled in this trial during a different patient encounter * Non-English speaking