A 70-year-old man with chronic heart failure and atrial fibrillation on digoxin presents with nausea, visual halos, and a regular bradycardic rhythm. ECG shows scooping of the ST segment. Which electrolyte abnormality most potentiates digoxin toxicity?
- A Hypokalemia ✓
- B Hyperkalemia
- C Hypercalcemia
- D Hyponatremia
Correct answer: A. Hypokalemia
Explanation
Hypokalemia increases digoxin binding to the Na+/K+ ATPase pump, making the heart more susceptible to digoxin toxicity. Hyperkalemia, though dangerous in toxicity, is not a precipitating factor. Hypercalcemia can exacerbate digitalis toxicity but hypokalemia is the classic and most potentiating electrolyte disturbance.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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