**Core Concept**
QT interval prolongation is a cardiac arrhythmia that occurs when the time between the start of the Q wave and the end of the T wave in the heart's electrical cycle is lengthened. This can lead to a condition known as Torsades de Pointes, a type of polymorphic ventricular tachycardia.

**Why the Correct Answer is Right**
The correct answer is related to the drugs that can cause QT prolongation. Certain medications can increase the duration of the QT interval by blocking the delayed rectifier potassium channels (IKr) in the heart, specifically the hERG (human Ether-à-go-go-Related Gene) potassium channels. This can lead to a prolonged QT interval and potentially life-threatening arrhythmias.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the drug listed can indeed cause QT prolongation. It is a well-known side effect of this medication, which can lead to serious cardiac arrhythmias.

**Option B:** This option is incorrect because this medication is actually used to treat QT prolongation, not cause it. It works by blocking the sodium channels in the heart and is used in the treatment of arrhythmias.

**Option C:** This option is incorrect because this medication can cause QT prolongation as a side effect. It is a known interaction of this medication, which can increase the risk of cardiac arrhythmias.

**Option D:** This option is incorrect because this medication is actually used to treat QT prolongation, not cause it. It works by blocking the potassium channels in the heart and is used in the treatment of arrhythmias.

**Clinical Pearl / High-Yield Fact**
When prescribing medications, it is essential to be aware of their potential to cause QT prolongation, especially in patients with a history of cardiac arrhythmias or those taking other medications that can prolong the QT interval.

**Correct Answer:** D. This medication is used to treat QT prolongation, not cause it.