**Core Concept**
Paroxysmal Supraventricular Tachycardia (PSVT) is a type of abnormal heart rhythm characterized by rapid heartbeats originating from the atria or the AV node. The treatment goal is to restore a normal sinus rhythm and alleviate symptoms.

**Why the Correct Answer is Right**
The drug of choice for PSVT is Adenosine, a short-acting vasodilator that selectively blocks AV nodal conduction. Adenosine acts by binding to A1 receptors in the AV node, which leads to a transient block in AV conduction, resulting in termination of the PSVT episode. This mechanism is particularly effective because the AV node is the primary site of origin for PSVT in many cases.

**Why Each Wrong Option is Incorrect**
**Option A:** Digoxin is incorrect because it is a cardiac glycoside that increases contractility and slows AV conduction, but it can actually worsen PSVT by increasing the heart rate.
**Option B:** Amiodarone is incorrect because, although it can be used for various arrhythmias, it is not the first-line treatment for PSVT due to its potential side effects and slower onset of action.
**Option C:** Verapamil is incorrect because, although it is a calcium channel blocker that can slow AV conduction, it is not the preferred initial treatment for PSVT due to its potential for causing hypotension.

**Clinical Pearl / High-Yield Fact**
Adenosine is often administered via rapid IV bolus (6-12 mg) over 1-2 seconds, followed by a saline flush, to take advantage of its brief half-life and minimize side effects.

**Correct Answer: A. Adenosine**