**Core Concept**
Prinzmetal angina, also known as variant angina, is a type of chest pain caused by transient, coronary artery vasospasm. It is characterized by sudden, brief episodes of severe chest pain, often occurring at rest, and is typically associated with electrocardiographic (ECG) changes.

**Why the Correct Answer is Right**
The pathophysiology of Prinzmetal angina involves the transient constriction of a coronary artery, leading to reduced blood flow to the heart muscle. This vasospasm is thought to be caused by the release of vasoconstrictor substances, such as serotonin and thromboxane A2, which stimulate alpha-adrenergic receptors on the smooth muscle cells of the coronary artery. The resulting vasospasm can lead to ischemia and pain in the chest, arm, or jaw.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Prinzmetal angina is not caused by an occlusive thrombus, unlike other forms of angina pectoris.
**Option B:** This option is incorrect because Prinzmetal angina is not typically associated with atherosclerotic plaque rupture or erosion.
**Option C:** This option is incorrect because Prinzmetal angina is not caused by an increase in myocardial oxygen demand, unlike effort angina.

**Clinical Pearl / High-Yield Fact**
Prinzmetal angina is often associated with a normal coronary angiogram between episodes, highlighting the importance of provocative testing, such as ergonovine or acetylcholine challenge, to diagnose this condition.

**Correct Answer: A. Prinzmetal angina is a type of chest pain caused by transient, coronary artery vasospasm.**