What role does digoxin play in treating heart failure?

Digoxin primarily acts by increasing myocardial contractility, which is crucial in the management of heart failure. It achieves this through its inhibition of the Na+/K+ ATPase pump on cardiac myocytes. By blocking this pump, digoxin leads to an increase in intracellular sodium levels. This, in turn, alters the function of the Na+/Ca2+ exchanger, resulting in increased intracellular calcium concentrations. The elevated calcium enhances the force of myocardial contraction (positive inotropic effect), thereby improving the overall pumping efficiency of the heart.

This increased contractility is particularly beneficial in patients with heart failure due to reduced ejection fraction, as it helps augment cardiac output and relieve symptoms such as fatigue and dyspnea. Consequently, while digoxin also has other effects such as modest heart rate reduction through vagal stimulation, its primary and most clinically significant role in heart failure treatment is the enhancement of myocardial contractility.