Clinical meaning
Unstable angina (UA) sits on the ACS spectrum between stable angina and NSTEMI, characterized by plaque disruption with non-occlusive thrombus and ischemia WITHOUT myocardial necrosis. The nurse must distinguish UA from NSTEMI through serial high-sensitivity troponin (hs-cTn) monitoring, risk-stratify using validated tools, and implement protocol-based management. Braunwald Classification categorizes UA by severity: Class I (new-onset severe or accelerated angina, no rest pain), Class II (subacute rest angina within past month, no pain within 48 hours), Class III (acute rest angina within 48 hours). Clinical circumstance is also classified: A (secondary, triggered by anemia, fever, hypotension), B (primary, without extracardiac trigger), C (post-infarction within 2 weeks of MI). With the advent of high-sensitivity troponin assays, many patients previously classified as UA are now reclassified as NSTEMI (type 2) due to detection of previously undetectable troponin elevations. The 0/1-hour or 0/3-hour hs-cTn algorithms allow rapid rule-out of MI: hs-cTnT below 5 ng/L at presentation effectively excludes MI with 99% negative predictive value. The nurse implements chest pain protocols, manages heparin infusions, interprets dynamic ECG changes, calculates TIMI risk scores, and coordinates care transitions.