Stable Angina vs Unstable Angina

Stable angina is predictable chest pain triggered by exertion or stress, lasting less than 5 minutes, and relieved by rest or sublingual nitroglycerin (up to 3 doses, 5 minutes apart). It results from a fixed atherosclerotic plaque that limits blood flow during increased demand but doesn't rupture. The pattern is consistent — the client can tell you exactly what brings it on. Unstable angina is an acute coronary syndrome. The plaque has ruptured or eroded, forming a partial thrombus that critically narrows the vessel. Pain occurs at rest or with minimal exertion, lasts longer than 15-20 minutes, is more severe than the client's usual pattern, and does NOT fully resolve with nitroglycerin. Any change in a previously stable pattern — new onset, increasing frequency, lower threshold, or pain at rest — reclassifies the angina as unstable and demands emergency evaluation. Unstable angina produces no troponin elevation (distinguishing it from MI), but it is treated as a medical emergency because it can progress to infarction at any moment. The nursing priority is recognizing the shift from stable to unstable: this is when you activate the rapid response, not when you reassure and reposition.