A patient presents with acute heart failure. Administration of a drug that increases myocardial contractility and decreases heart rate is being considered. Which of the following best describes the cellular mechanism of such a drug on myocardial cells?

✓ Correct Answer: Option A

Inhibition of Na+/K+ ATPase by drugs like digoxin increases intracellular Na+, which then reduces the Na+/Ca2+ exchanger's ability to extrude Ca2+. This leads to increased intracellular Ca2+ and stronger myocardial contractions.