<prompt> Digoxin increases cardiac contractility by directly engaging in wofInhibiting myocardial Na Ca 2 -ATPaseActivating L-type Ca 2 channelsInhibiting cardiac phosphodiesteraseInhibiting myocardial Na K -ATPase  <response>: Mechanism of action:- Digoxin increases force of cardiac contraction by a direct action independent of innervation. It selectively binds to extracellular face of the membrane associated NaK ATPase of myocardial fibres and inhibitis this enzyme. Inhibition of this cation pump results in progressive accumulation of Na intracellularly. This indirectly results in intracellular Ca2 accumulation. During depolarization Ca2 ions enter the cell driven by the steep Ca2 gradient through voltage sensitive L type Ca2 channels. This triggers release of larger amount of Ca2 stored in sarcoplasmic reticulum SR through Ryanodine calcium channel 2 RYR2 - cytosolic Ca2 increases transiently calcium transients - triggers contraction by activating troponin C on myofibrils. Ref:- kd tripathi; pg num:-514 