## **Core Concept**
Digitalis, a cardiac glycoside, is used to treat heart conditions like atrial fibrillation and heart failure. It works by inhibiting the **Na+/K+ ATPase pump**, leading to increased intracellular calcium and a subsequent increase in cardiac contractility. However, its therapeutic window is narrow, making it prone to toxicity.

## **Why the Correct Answer is Right**
The correct answer, ., refers to an option that does not align with known side effects of digitalis. Digitalis toxicity can manifest as **gastrointestinal symptoms (nausea, vomiting, diarrhea)**, **visual disturbances (blurred vision, yellow-green halos)**, and **cardiac arrhythmias (atrial tachycardia with AV block, ventricular bigeminy)**.

## **Why Each Wrong Option is Incorrect**
- **Option A:** . This option likely lists a known side effect of digitalis, making it an incorrect choice for "all except."
- **Option B:** . Similarly, this option probably represents another recognized side effect, such as nausea or visual disturbances, which are common with digitalis use.
- **Option C:** . This could be a side effect like cardiac arrhythmias, which are a hallmark of digitalis toxicity.

## **Clinical Pearl / High-Yield Fact**
A key clinical point to remember is that **digitalis toxicity can be exacerbated by factors like hypokalemia, hypomagnesemia, and renal insufficiency**. Monitoring electrolyte levels and renal function is crucial in patients on digitalis.

## **Correct Answer: D. .**