Mechanism of action of digitalis in atrial fibrillation is:
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.
By decreasing cardiac contractility
Na+ K+ ATPase inhibition
Increase in refractoriness of AV nodal tissue
By causing bradycardia
CHF, Angina Pectoris and Myocardial Infarction