Clinical meaning
Acute coronary syndrome (ACS) encompasses unstable angina (UA), NSTEMI, and STEMI, all resulting from atherosclerotic plaque rupture or erosion with superimposed thrombosis. Plaque rupture exposes the lipid-rich necrotic core and collagen to flowing blood, triggering platelet adhesion (via von Willebrand factor and GPIb), activation, and aggregation (via GPIIb/IIIa). The coagulation cascade generates thrombin and fibrin, forming an occlusive or near-occlusive thrombus. STEMI results from complete thrombotic occlusion causing transmural ischemia (ST elevation); NSTEMI results from subtotal occlusion or microembolization causing subendocardial injury (troponin elevation without ST elevation); UA involves ischemia without myocyte necrosis (normal troponin). Risk stratification uses HEART score (History, ECG, Age, Risk factors, Troponin) or TIMI score to guide disposition.
Diagnosis & workup
Diagnostics & workup: - 12-lead ECG within 10 minutes of presentation: STEMI (ST elevation ≥1 mm in 2 contiguous leads, or new LBBB); NSTEMI (ST depression, T-wave inversions); UA (normal or nonspecific changes) - Serial high-sensitivity troponin (hs-cTnI or hs-cTnT): at presentation and 3-6 hours later; rule-out with 0/1-hour or 0/3-hour protocol using hs-troponin algorithms - HEART score calculation: History (0-2), ECG (0-2), Age (0-2), Risk factors (0-2), Troponin (0-2); score 0-3 = low risk, 4-6 = moderate, 7-10 = high risk - CXR: rule out aortic dissection (widened mediastinum), pneumothorax, pneumonia, pericardial effusion - BMP: assess renal function (contrast exposure for cath), electrolytes (arrhythmia risk) - BNP/NT-proBNP if heart failure suspected (prognostic value in ACS) - Echocardiography: assess wall motion abnormalities, EF, complications (papillary muscle rupture, VSD, pericardial effusion) - Stress testing for intermediate-risk patients to assess inducible ischemia before or after discharge