A nurse in the emergency department is assessing a client who has a history of angina and reports chest pain. Which of the following findings is the priority?

A. Three doses of nitroglycerin relieve the client's pain: Pain relieved by nitroglycerin suggests stable angina rather than an acute, unstable cardiac event. Although important to note, this finding does not indicate immediate danger compared to symptoms that suggest unstable or evolving myocardial ischemia. B. Pain began in the morning while the client was resting: Chest pain occurring at rest is a hallmark of unstable angina and signals a high risk for myocardial infarction. Rest pain indicates reduced coronary perfusion independent of exertion, making this the most urgent finding requiring rapid intervention to prevent cardiac tissue damage. C. Pain is greatest in the client's substernal chest area: Substernal pain is characteristic of angina, but this description alone does not differentiate between stable and unstable patterns. While clinically relevant, it is less critical than identifying ischemic pain that occurs without exertion. D. Pain radiates to the client's left arm: Radiation to the left arm is a classic symptom of myocardial ischemia, but it does not inherently signal instability or immediate progression to infarction. Many clients with chronic stable angina experience similar radiation patterns, so this finding is not as urgent as rest-onset chest pain.