Which feature is most indicative of unstable angina?

• A. Angina relieved after two doses of sublingual nitroglycerin
• B. Angina responsive to amlodipine
• C. Chest pain lasting more than 10 minutes
• D. Painful midsternal spasms at rest with preserved exercise capacity

Answer: (C)

Unstable angina is an acute coronary syndrome defined by a change in the pattern of ischemia—new or worsening angina, angina at rest, or a crescendo of symptoms. The most telling feature is chest pain that persists for more than about 10 minutes, indicating ongoing myocardial ischemia despite rest or therapy. Shorter, nitro-responsive episodes fit stable angina, and rest angina with preserved exercise capacity can point toward other etiologies such as vasospasm but doesn’t define instability. So prolonged pain (>10 minutes) is the hallmark sign that raises concern for unstable angina.