This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
A patient of atrial fibrillation is on digoxin therapy. Which of the following responses do you expect? 
Select and explain. 
A. Restoration of normal sinus rhythm, B. Conversion of atrial fibrillation to atrial flutter, C. Increase in atrial fibrillation frequency, but decrease in ventricular rate, D. Decrease in atrial fibrillation frequency but increase in ventricular rate
C: Increase in atrial fibrillation frequency, but decrease in ventricular rate
Answer: C: Increase in atrial fibrillation frequency, but decrease in ventricular rate 
Explanation: Digitalis controls the ventricular rate in AF patients. The frequency of atrial fibrillation may actually increase. Ibutilide is approved for the conversion of AF to sinus rhythm.