273.1 🎓 醫學生版

273.1.0.1 📌 一頁重點

273.1.0.1.1 Definition

273.1.0.1.1.1 NSTE-ACS Spectrum

• Unstable angina (UA): chest pain at rest, new-onset severe angina, crescendo pattern
  • ECG may show ST↓ / T↓ but NO troponin elevation
• NSTEMI: same clinical features + positive troponin (myocardial necrosis)
• No ST elevation on ECG (otherwise STEMI — see Ch273)

273.1.0.1.1.2 4th Universal Definition of MI (2018, updated 2024)

• Type 1: Plaque rupture/erosion (atherothrombotic)
• Type 2: Supply-demand mismatch (e.g., anemia, sepsis, hypertensive crisis)
• Type 3: Sudden cardiac death before troponin available
• Type 4a: PCI-related
• Type 4b: Stent thrombosis
• Type 4c: Restenosis
• Type 5: CABG-related

273.1.0.1.2 Pathophysiology

273.1.0.1.2.1 Plaque Disruption

• Rupture (60-70%) — vulnerable plaque with thin cap
• Erosion (30-40%) — endothelial denudation, more in women, smoking
• Calcified nodule (rare)

273.1.0.1.2.2 Thrombus Formation

• Platelet aggregation (white thrombus) + fibrin (red thrombus)
• Non-occlusive thrombus → NSTE-ACS
• Occlusive thrombus → STEMI

273.1.0.1.2.3 Distal Microembolization

• Plaque debris → microvascular obstruction
• Releases troponin even without major epicardial occlusion

273.1.0.1.3 Clinical Presentation

273.1.0.1.3.1 Symptoms

• Chest discomfort at rest (> 20 min) OR new-onset severe OR crescendo
• Quality similar to stable angina but more intense / prolonged
• Atypical presentations more common:
  • Elderly, women, DM
  • Dyspnea (angina equivalent), fatigue, nausea, epigastric pain
• “Angina equivalent” in diabetics — may have no chest pain

273.1.0.1.3.2 Examination

• Often normal between episodes
• During event: tachycardia, hypertension, S4 gallop, transient MR (papillary dysfunction)
• Signs of HF (rales, S3) if extensive ischemia

273.1.0.1.4 Diagnosis

273.1.0.1.4.1 ECG

• ST depression (≥ 0.5 mm horizontal/downsloping) — most concerning
• T-wave inversion (≥ 1 mm in 2 contiguous leads)
• Transient ST elevation (< 20 min)
• Normal ECG does NOT rule out (esp posterior or circumflex MI)
• De Winter T waves (upsloping ST↓ + tall T) → LAD occlusion equivalent
• Wellens syndrome (deep T inversion V2-3) → critical LAD stenosis
• aVR ST elevation + diffuse ST↓ → LM or 3VD

273.1.0.1.4.2 Troponin

• High-sensitivity cardiac troponin (hs-cTn) — preferred since 2017
• 0/1h or 0/2h algorithm (ESC 2023) — fast rule-in/rule-out
  • 0h < LOD: rule out (with low-risk clinical features)
  • 0h ≥ very high threshold: rule in immediately
  • In between: repeat at 1h or 2h, look at delta
• Causes of false positive elevation: HF, PE, sepsis, renal failure, myocarditis, takotsubo, arrhythmia

273.1.0.1.4.3 Risk Stratification

TIMI Score (1 point each, total 7): 1. Age ≥ 65 2. ≥ 3 CAD risk factors 3. Known CAD (≥ 50% stenosis) 4. ASA use within 7 days 5. ≥ 2 anginal episodes in 24 h 6. ST deviation ≥ 0.5 mm 7. Positive cardiac marker

• TIMI 0-2: low risk
• TIMI 3-4: intermediate
• TIMI 5-7: high → early invasive

GRACE Score (better discrimination): - Age, HR, SBP, Cr, Killip class, ST deviation, cardiac arrest, troponin - GRACE > 140 = high risk → invasive within 24h - GRACE > 109 = intermediate

273.1.0.1.5 Management

273.1.0.1.5.1 Initial (MONA-B is OUTDATED)

• Oxygen only if SpO2 < 90% (AVOID-O2 trial — no benefit if normal)
• Aspirin 300 mg loading then 81-100 mg daily (mortality benefit)
• Sublingual NTG for pain (avoid if SBP < 90, RV MI, or PDE5 use)
• Morphine — Class IIb only (ISAR-REACT 4 showed delayed antiplatelet absorption)
• Beta-blocker within 24h if no HF or shock
• ACEi within 24h if LV dysfunction or HF
• Statin high-intensity (atorvastatin 80 mg) early
• Anticoagulation — UFH or enoxaparin or fondaparinux

273.1.0.1.5.2 Antiplatelet (DAPT)

• ASA 81-100 mg lifelong
• P2Y12 inhibitor:
  • Ticagrelor 90 mg BID (180 mg load) — preferred per ESC 2023 (PLATO trial)
  • Prasugrel 10 mg daily (60 mg load) — alternative, more effective in DM; avoid if prior stroke or > 75 yo
  • Clopidogrel 75 mg (300-600 mg load) — if ticag/prasugrel CI or in elderly
• DAPT duration: 12 months standard
• High bleeding risk (HBR): 1-3 month DAPT then switch to P2Y12 mono (MASTER DAPT 2021, STOPDAPT-2 2019)

273.1.0.1.5.3 Anticoagulation

• Enoxaparin 1 mg/kg SC BID (renal adj)
• UFH (preferred peri-PCI)
• Fondaparinux (less bleeding, but no benefit in PCI alone)
• Bivalirudin (during PCI, reduce bleeding)
• Continue until PCI or discharge

273.1.0.1.5.4 Invasive vs Conservative Strategy

Immediate (< 2h) invasive — high-risk features: - Hemodynamic instability or cardiogenic shock - Recurrent/persistent angina despite OMT - Life-threatening arrhythmias - Mechanical complications - Acute HF

Early (< 24h) invasive — GRACE > 140 or other high-risk: - Troponin rise/fall - Dynamic ST/T changes - GRACE > 140 - 2023 ESC: Class I

Delayed invasive (< 72h) — intermediate risk: - DM, CKD, LVEF < 40%, prior CABG, prior PCI, GRACE 109-140

Selective invasive — low risk: - Negative tropo, no recurrent symptoms - Risk stratification with stress test or CCTA

273.1.0.1.5.5 Revascularization

• PCI for most lesions
• CABG for LM, 3VD with DM, complex disease (SYNTAX high)
• FAME-3 (2022): FFR-guided PCI not non-inferior to CABG for 3VD (CABG still preferred for complex 3VD)

273.1.0.1.5.6 Secondary Prevention (ABCDE — same as stable IHD)

• A: Antiplatelet (DAPT 12 mo, then ASA + maybe rivaroxaban)
• B: Beta-blocker (lifelong if LVEF < 40% or for symptoms)
• C: Cholesterol (atorvastatin 80 mg, goal LDL < 55, add ezetimibe / PCSK9i)
• D: Diabetes (HbA1c < 7%, SGLT2i / GLP-1 if ASCVD)
• E: Exercise, cardiac rehab (Class I — see Ch274)

273.1.0.1.5.7 Cardiac Rehabilitation

• Class I recommendation
• 12-week program
• Reduces mortality, recurrent MI, readmission

273.1.0.2 🩺 床邊速查

• NSTEMI = UA + positive troponin (no ST elevation)
• GRACE > 140: early invasive < 24h
• TIMI score: 7-point (≥ 5 high-risk)
• DAPT 12 months (ticagrelor preferred); high bleeding risk → 1-3 mo
• hs-cTn 0/1h algorithm (ESC 2023)
• aVR STE + diffuse ST↓: LM or 3VD until proven otherwise

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