What ECG finding is characteristic of Prinzmetal's angina?

In Prinzmetal's angina, which is also known as variant angina, the ECG finding that is most characteristic is ST elevation during episodes of chest pain. This transient elevation occurs due to coronary artery spasm, which temporarily reduces blood flow to the heart muscle and can lead to ischemic changes manifesting as ST segment alterations on the ECG.

When the coronary arteries spasm, there is a decrease in oxygen supply to the heart, which causes the ischemic response and results in ST segment elevation. Often, this elevation resolves once the spasm goes away, which can occur with rest or the use of nitroglycerin.

In contrast, other findings such as ST depression typically indicate myocardial ischemia due to exertion or stress; no significant changes would be expected in patients without active ischemia; and while arrhythmias can occur in various cardiac conditions, they are not a defining ECG feature of Prinzmetal's angina itself. Understanding these distinctions is crucial for accurate diagnosis and management in an acute care setting.