**Core Concept**
The prolongation of the QT interval is associated with an increased risk of torsades de pointes, a type of polymorphic ventricular tachycardia. This condition can lead to syncope, seizures, or even cardiac arrest. The QT interval represents the time from the start of the Q wave to the end of the T wave in the heart's electrical cycle.

**Why the Correct Answer is Right**
The prolongation of the QT interval is often caused by drugs that block potassium channels in the heart, specifically the hERG (human Ether-à-go-go-Related Gene) channel. This leads to a decrease in the inward potassium current, which prolongs the action potential duration and, consequently, the QT interval. The correct answer, **Erythromycin**, is a macrolide antibiotic that is known to block the hERG channel, leading to QT interval prolongation.

**Why Each Wrong Option is Incorrect**
* **Option A:** **Digoxin** is actually known to shorten the QT interval by increasing the inward sodium current.
* **Option B:** **Furosemide** is a loop diuretic that can cause hypokalemia, which may indirectly lead to QT interval prolongation, but it is not a direct cause.
* **Option C:** **Amiodarone** is an antiarrhythmic drug that can prolong the QT interval, but it is not the most commonly associated drug with this effect compared to erythromycin.

**Clinical Pearl / High-Yield Fact**
When prescribing antibiotics like erythromycin, it is essential to monitor patients for signs of QT interval prolongation, especially in those with a history of heart disease or taking other medications that can prolong the QT interval.

**Correct Answer:** E. Erythromycin