A patient is admitted with the diagnosis of variant or Prinzmetal angina. The nurse knows that the physiological mechanism present is most likely which of the following?

Rationale: A. Vasospasm of a coronary artery is correct because Prinzmetal (variant) angina is caused by transient spasm of a coronary artery, which leads to temporary myocardial ischemia. The spasm can occur at rest, often at night, and is not necessarily associated with atherosclerotic plaque. Symptoms include chest pain, ST-segment elevation during episodes, and relief with nitroglycerin or calcium channel blockers. B. Partial occlusion of a coronary artery with a thrombus is incorrect because this mechanism is typical of unstable angina or acute coronary syndrome, not Prinzmetal angina. In these conditions, pain is usually precipitated by exertion or plaque rupture, rather than spontaneous vasospasm. C. Complete occlusion of a coronary artery is incorrect because complete blockage leads to myocardial infarction, which is more severe and causes persistent chest pain and irreversible myocardial damage, unlike the transient ischemia of Prinzmetal angina. D. Fatty streak within the intima of a coronary artery is incorrect because fatty streaks represent early atherosclerotic changes. While atherosclerosis may coexist, Prinzmetal angina is primarily due to dynamic coronary artery spasm, not the presence of a fatty streak alone.