How is action of digoxin in increasing contractility?

Digoxin increases the force of cardiac contraction, causing cardiac output to more closely resemble that of the normal heart Vagal tone is also enhanced, so both heart rate and myocardial oxygen demand decrease. Digoxin slows conduction velocity through the AV node, making it useful for atrial fibrillation. [Note: In the normal heart, the positive inotropic effect of digitalis glycosides is counteracted by compensatory autonomic reflexes.]