Digoxin inhibits Na+/K+ ATPase. Which finding is a classic sign of digoxin toxicity?

• A. Seizures and coma.
• B. Severe tachycardia with hypotension.
• C. Yellow-green vision and bradycardia.
• D. Hyperkalemia causes tremor and panic.

Answer: (C)

Digoxin toxicity most strikingly blends retinal effects with a slow heart rate due to its actions on the heart and nervous system. By inhibiting Na+/K+ ATPase, digoxin raises intracellular calcium in cardiac cells, which enhances contractility, but at toxic levels it also increases vagal (parasympathetic) tone and slows AV conduction. The retinal effect of Na+/K+ ATPase inhibition can produce color vision changes, most classically yellow or yellow-green vision with halos. Put together, seeing yellow-green vision alongside bradycardia is the hallmark presentation of digoxin toxicity. Other signs like seizures, tachycardia with hypotension, or tremor from hyperkalemia can occur in severe cases, but they are not the classic, defining findings.