<prompt> The positive inotropic effect of digitalis due to inhibition of the NaK ATPase pump in cardiac muscle cell membrane leads to:Decreased activity of NaCa exchanger causing decreased influx of sodium and decreased efflux of Ca in the sarcolemmaDecreased efflux of Na leading to less negative resting membrane potential and opening of voltage gated Ca channels on the T tubulesIncreased intracellular Na causing increased efflux of Na and increased influx of Ca through Na Ca exchanger in the sarcolemmaIncreased intracellular Na decreasing the activity of Ca pump in the sarcoplasmic reticulum  <response>: 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 