The positive inotropic effect of digitalis due to inhibition of the Na+/K+ ATPase pump in cardiac muscle cell membrane leads to:
Digitalis selectively binds to the extracellular face of membrane- Na-k ATPase is inhibited. Inhibition of this cation pump results in progressive accumulation of Na intracellularly. Indirectly result in intracellular Calcium accumulation. REF.Essentials of medical pharmacology K D TRIPATHI 6 Edition)