Clinical meaning
Acute coronary syndrome diagnosis integrates clinical presentation, ECG findings, and serial cardiac biomarkers using evidence-based criteria. The clinician recognizes the ACS spectrum: STEMI (ST-elevation myocardial infarction -- transmural ischemia with ST elevation in two or more contiguous leads meeting voltage criteria: 1 mm in limb leads, 1 mm in V4-V6, 1.5 mm in V1-V3 for women, or 2 mm in V1-V3 for men), NSTEMI (non-ST-elevation MI -- subendocardial ischemia with ST depression, T-wave inversion, or no ECG changes but elevated troponin), and unstable angina (no troponin elevation but clinical presentation consistent with ACS). High-sensitivity cardiac troponin (hs-cTnI or hs-cTnT) is the biomarker of choice: the clinician applies the 0/1-hour or 0/3-hour algorithm -- an initial very low hs-cTnT (less than 5 ng/L) with stable or falling values at 1-3 hours effectively rules out MI (negative predictive value greater than 99.5%); rising values with a delta exceeding the assay-specific threshold rules in MI. The clinician calculates HEART score (History, ECG, Age, Risk factors, Troponin) or TIMI risk score to stratify risk and determine disposition (low risk may be candidates for outpatient...