Mechanism of action of digitalis in atrial fibrillation is:
By decreasing cardiac contractility
Na+ K+ ATPase inhibition
Increase in refractoriness of AV nodal tissue
By causing bradycardia
Digoxin reduces ventricular rate in A. Fib. by decreasing the number of impulses that are able to pass down the A-V node and bundle of His. It increases ERP of A-V node by direct, vagomimetic and antiadrenergic actions --> Minimum interval between consecutive impulses that can successfully traverse the conducting tissue is prolonged.
CHF, Angina Pectoris and Myocardial Infarction