A 76 year old patient has been in atrial fibrillation and having palpitations. They have been treated with amiodarone and diltiazem without improvement. The cardiologist decides to start them on digoxin therapy. How does digoxin work? Digoxin:

A) Increases cardiac contractility
B) Decreases heart rate
C) Promotes vasodilation
D) Inhibits renin secretion