Stable Angina vs Unstable Angina

Both cause chest pain, but one means the patient can wait for a cardiology appointment and the other means they're having an acute coronary event right now. The distinction drives every decision you make.

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 patient 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 patient'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.

Key Distinctions

Don't confuse unstable angina with NSTEMI — both have chest pain without ST elevation, but unstable angina has negative troponins while NSTEMI has elevated troponins. Students often think nitroglycerin failure alone defines unstable angina, but new-onset angina or a changing pattern also qualifies even if NTG hasn't been tried. Stable angina is managed outpatient; unstable angina is managed as an inpatient emergency.

Clinical Pearl

Stable angina is a story the patient has told before — same trigger, same relief. The moment the story changes, it's unstable, and you treat it like an emergency.