A patient reports developing chest pain and dyspnea while walking to the mailbox. The pain does not subside after rest. The patient is likely experiencing:

Unstable angina is chest pain that occurs with minimal exertion or at rest and does not reliably resolve with rest or respond predictably to nitroglycerin. The key distinguishing feature in this scenario is that the pain does not subside after rest, which rules out stable angina. Stable angina is predictable chest pain that occurs with a consistent level of exertion and resolves within a few minutes of rest or nitroglycerin administration. It reflects a fixed coronary artery stenosis that becomes symptomatic only when myocardial oxygen demand exceeds supply during activity. Unstable angina, by contrast, indicates a dynamic process — usually a ruptured atherosclerotic plaque with partial thrombus formation — that limits coronary blood flow even at rest. It is an acute coronary syndrome and requires urgent evaluation. Unpredictable angina is not a standard clinical classification used in cardiology; the recognized categories are stable, unstable, and variant (Prinzmetal's). Atypical angina refers to chest pain presentations that lack the classic features, such as jaw pain or epigastric discomfort without a clear exertional pattern; the client in the stem has a fairly typical exertional presentation but with the critical red flag that rest does not relieve the pain, making unstable angina the correct classification.