What is the primary difference between stable and unstable angina?

The primary difference between stable and unstable angina is that stable angina is typically relieved by rest or nitroglycerin, while unstable angina is not. Stable angina occurs predictably with exertion or emotional stress and is consistent in terms of intensity and duration. When the provoking factor is removed, the pain subsides. In contrast, unstable angina may occur at rest, is more unpredictable, and can be a precursor to a heart attack. It may not respond to typical relief measures, which makes it a serious condition requiring immediate medical attention.

Understanding this key distinction is crucial for recognizing the urgency of unstable angina, as it can indicate significant coronary artery disease and an increased risk of myocardial infarction.