In terms of the ability of drugs like digoxin to increase cardiac contractility, their primary action on cardiac cells is
Cardiac glycosides increase contractility by inhibiting the Na/K-ATPase pump, causing an increase in intracellular Na. This, in turn, increases intracellular Ca by slowing down Na/Ca exchange. The increase in intracellular Ca leads to its binding to the troponin-tropomyosin complex, causing an allosteric change and facilitating the interaction between actin and myosin.
activation of adenylyl cyclase
inactivation of Na channels
activation of the slow Ca channel
inhibition of Na/K-ATPase
C.V.S