## **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. Nitroglycerin works by releasing nitric oxide (NO), which stimulates guanylate cyclase, increasing cyclic guanosine monophosphate (cGMP) levels. This leads to smooth muscle relaxation and vasodilation.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Beta blockers are generally contraindicated in Prinzmetal's angina because they can cause unopposed alpha-adrenergic receptor-mediated coronary artery vasoconstriction, potentially worsening the spasm.
- **Option B:** Calcium channel blockers are used in the long-term management of Prinzmetal's angina but are not the first choice for acute relief during an attack because their onset of action is slower compared to nitroglycerin.
- **Option D:** Aspirin is not used as a first-line treatment for acute Prinzmetal's angina because it does not relieve acute vasospasm and may even worsen ischemia by inhibiting prostacyclin synthesis.

## **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, distinguishing it from typical angina caused by atherosclerotic coronary artery disease. Nitroglycerin is effective for immediate relief but long-term management may involve calcium channel blockers and lifestyle modifications.

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