Agent of first choice in an acute attack of Prinzmetals angina is –
**Core Concept**
Prinzmetal's angina, also known as variant angina, is caused by transient coronary artery spasm. The underlying principle involves the **pathophysiology of coronary artery spasm** and its relief.
**Why the Correct Answer is Right**
The agent of choice in an acute attack of Prinzmetal's angina is a **vasodilator**, specifically one that can relieve the coronary artery spasm. **Nitroglycerin** is commonly used as it acts through the release of **nitric oxide**, leading to **smooth muscle relaxation** and subsequent vasodilation of the coronary arteries.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because, while important in managing other forms of angina, it is not the first choice for Prinzmetal's angina.
**Option B:** Incorrect as it is not directly used for acute relief of coronary spasm in Prinzmetal's angina.
**Option D:** Incorrect because, although it has vasodilatory effects, it is not the first line of treatment for an acute attack.
**Clinical Pearl / High-Yield Fact**
Remember, **nitroglycerin** is the key to relieving the spasm in Prinzmetal's angina, acting quickly to improve blood flow to the heart muscle.
**Correct Answer:** D. Nitroglycerin