## **Core Concept**
Prinzmetal's angina, also known as variant angina, is a type of angina pectoris caused by transient coronary artery spasm. The management of Prinzmetal's angina focuses on relieving the spasm and restoring blood flow to the heart muscle.

## **Why the Correct Answer is Right**
The correct answer, **C. Nitroglycerin**, is the agent of first choice in an acute attack of Prinzmetal's angina because nitroglycerin acts rapidly to relax vascular smooth muscle, thereby relieving coronary artery spasm and improving blood flow to the myocardium. Nitroglycerin works by releasing nitric oxide (NO), which activates guanylate cyclase, increasing cyclic guanosine monophosphate (cGMP) levels, and leading to smooth muscle relaxation.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Propranolol is a beta-blocker and can actually worsen Prinzmetal's angina by leaving alpha-mediated vasoconstriction unopposed, potentially increasing coronary artery spasm.
- **Option B:** Verapamil is a calcium channel blocker that can be used to prevent Prinzmetal's angina attacks but is not the first choice for immediate relief during an acute attack due to its slower onset of action compared to nitroglycerin.
- **Option D:** Aspirin is an antiplatelet agent and does not have a direct role in relieving acute coronary artery spasm.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that Prinzmetal's angina is often associated with normal or near-normal coronary arteries on angiography, and the condition can be diagnosed with a positive response to vasodilators like nitroglycerin. A classic clinical scenario involves chest pain at rest, often associated with transient ST-segment elevation on the ECG.

## **Correct Answer:** C. Nitroglycerin