274.1 🎓 醫學生版

274.1.0.1 📌 一頁重點

274.1.0.1.1 Definition

274.1.0.1.1.1 STEMI ECG Criteria (4th Universal Definition)

• New ST elevation in 2 contiguous leads:
  • ≥ 1 mm in most leads
  • ≥ 1.5 mm in V2-V3 in women
  • ≥ 2 mm in V2-V3 in men ≥ 40 yo
  • ≥ 2.5 mm in V2-V3 in men < 40 yo
• New LBBB or RBBB with appropriate symptoms = STEMI equivalent (with Sgarbossa criteria for LBBB)
• Posterior MI: ST↓ V1-V3 with tall R waves (use posterior leads V7-V9)
• De Winter T waves = STEMI equivalent
• Wellens syndrome = NOT STEMI but critical LAD

274.1.0.1.1.2 Localization

Lead Group	Territory	Coronary Artery
II, III, aVF	Inferior	RCA (~80%) or LCx (20%)
V1-V2	Septal	LAD (septal branches)
V3-V4	Anterior	LAD
V5-V6	Apical/lateral	LAD or LCx
I, aVL	High lateral	LCx or diagonal
V7-V9	Posterior	LCx or RCA
V3R-V4R	Right ventricle	Proximal RCA
aVR + diffuse ST↓	LM or 3VD	LM, LAD ostial

274.1.0.1.2 Pathophysiology

274.1.0.1.2.1 Plaque Rupture → Occlusion

• Vulnerable plaque ruptures → tissue factor exposed → coagulation cascade
• Platelet aggregation + fibrin formation → fully occlusive thrombus
• No collateral flow → transmural ischemia → ST elevation
• Time-dependent necrosis: starts at 20-30 min, complete by 6h
• “Wavefront phenomenon”: subendocardium first, then transmural

274.1.0.1.2.2 Reperfusion Injury

• Restoration of blood flow may paradoxically worsen damage:
  • Calcium overload
  • Oxidative stress
  • Mitochondrial permeability transition pore opening
  • Microvascular obstruction (MVO)
• Strategies: cyclosporine (CIRCUS — neg), remote ischemic conditioning (CONDI-2/ERIC-PPCI — neg), ischemic postconditioning

274.1.0.1.3 Clinical Presentation

274.1.0.1.3.1 Symptoms

• Severe substernal chest pain, > 20 minutes
• Radiation to L arm, jaw, neck, back
• Diaphoresis, nausea, vomiting
• Dyspnea, anxiety, “sense of impending doom”
• Atypical: elderly, women, DM (silent or anginal equivalent)
• 15-20% silent (especially DM, elderly)

274.1.0.1.3.2 Physical Exam

• Diaphoretic, anxious
• Tachycardia or bradycardia (inferior MI with vagal)
• Hypotension or hypertension
• S4 (decreased compliance), S3 (LV dysfunction)
• New MR murmur (papillary dysfunction or rupture)
• Pulmonary rales if HF
• Cool extremities if shock
• JVD + clear lungs = RV MI (inferior + V4R STE)

274.1.0.1.3.3 Killip Classification (Prognostic)

• Class I: no HF (6% 30-d mortality)
• Class II: rales, S3 (17%)
• Class III: pulmonary edema (38%)
• Class IV: cardiogenic shock (81%)

274.1.0.1.4 Initial Diagnosis & Triage

274.1.0.1.4.1 Pre-Hospital

• STEMI alert / cardiac cath lab activation by EMS
• 12-lead ECG within 10 min of FMC
• Direct transport to PCI-capable hospital if feasible (within 120 min)
• Aspirin 162-325 mg chewed
• IV access, monitoring

274.1.0.1.4.2 Hospital Triage

• ECG within 10 min of arrival
• STEMI alert
• Cardiology + interventional team
• Troponin (will become positive at 3-12h)

274.1.0.1.5 Reperfusion Strategy

274.1.0.1.5.1 Primary PCI (Preferred)

• Door-to-balloon (D2B) ≤ 90 min if patient comes to PCI center
• FMC-to-device ≤ 120 min if transferred
• Radial access preferred (RIVAL, MATRIX trials — ↓ bleeding, ↓ mortality)
• DES preferred over BMS
• Complete revasc preferred in stable patients (COMPLETE 2019)
• Aspiration thrombectomy NOT routine (TASTE, TOTAL trials)

274.1.0.1.5.2 Fibrinolysis

• Indications: STEMI symptoms < 12h + cannot reach PCI center within 120 min
• Best within 30 min (door-to-needle ≤ 30 min)
• Drugs:
  • Tenecteplase (TNK) — single bolus, preferred
  • Alteplase (tPA) — older, requires infusion
• Contraindications (HIGH-YIELD):
  • Absolute: prior ICH any time, ischemic stroke < 3 mo, intracranial neoplasm, AVM, suspected aortic dissection, active bleeding, significant closed head trauma < 3 mo
  • Relative: severe HTN > 180/110, oral anticoagulant, recent surgery (< 3 wk), recent internal bleeding (< 2-4 wk), pregnancy, age > 75, traumatic CPR
• Pharmaco-invasive strategy: lyse → transfer for PCI within 3-24h (Class I if not reperfused) — DANAMI-2, STREAM trial

274.1.0.1.5.3 Coronary Artery Bypass Grafting (CABG)

• Rarely emergent for STEMI
• Failed PCI with continued ischemia
• Mechanical complications (VSR, papillary muscle rupture)
• LM or complex 3VD not amenable to PCI

274.1.0.1.6 Adjunctive Therapy

274.1.0.1.6.1 Antiplatelet

• ASA 162-325 mg chewed STAT → 81 mg daily lifelong
• P2Y12 inhibitor loading before PCI:
  • Ticagrelor 180 mg (then 90 mg BID) — preferred per 2023 ESC
  • Prasugrel 60 mg (then 10 mg) — preferred per 2024 ACC for PCI; avoid if prior stroke
  • Clopidogrel 600 mg if others contraindicated
• DAPT for 12 months minimum

274.1.0.1.6.2 Anticoagulation Peri-PCI

• UFH (preferred): 70-100 U/kg bolus, target ACT 250-300
• Bivalirudin: ↓ bleeding (MATRIX trial), now Class IIa
• Enoxaparin: 0.5 mg/kg IV bolus
• GP IIb/IIIa inhibitors (abciximab, eptifibatide, tirofiban): only for bailout (large thrombus)

274.1.0.1.6.3 Statin

• Atorvastatin 80 mg ASAP (before or during admission)
• LDL target < 55 mg/dL

274.1.0.1.6.4 Beta-Blocker

• Within 24h if no HF or shock (Class I)
• Avoid early IV β-blocker in shock or hemodynamic instability (COMMIT-CCS-2 caution)
• Lifelong if LVEF < 40% or persistent symptoms; otherwise 1-3 year per 2024 update (re-evaluating)

274.1.0.1.6.5 ACEi / ARB

• Within 24h if anterior MI, LVEF < 40%, or HF (Class I)
• Lifelong

274.1.0.1.6.6 MRA

• Eplerenone for LVEF ≤ 40% + HF or DM (EPHESUS) — Class I
• Spironolactone alternative

274.1.0.1.6.7 SGLT2 inhibitor

• Empagliflozin 10 mg/d post-MI (EMPACT-MI 2024) — added to standard care for high-risk post-MI patients
• Increasingly Class IIa for post-MI with LV dysfunction

274.1.0.1.7 Complications

274.1.0.1.7.1 Arrhythmias

• VF/VT: most common cause of death pre-hospital; defibrillate, amiodarone
• AV block: inferior MI → vagal/AVN ischemia; usually transient, atropine
• AV block in anterior MI: bad — Mobitz II or CHB → infranodal, often permanent pacer
• Sinus brady: inferior MI vagal; atropine
• AF: pain, atrial ischemia; treat as usual

274.1.0.1.7.2 Mechanical (2-7 days post-MI)

• Papillary muscle rupture: posteromedial PM (single blood supply from RCA) most common → acute severe MR + pulmonary edema → emergency MVR
• Ventricular septal rupture (VSR): holosystolic murmur, biventricular failure → emergency surgical or transcatheter repair
• Free wall rupture: tamponade → death; emergency surgery
• LV aneurysm: late (weeks), persistent ST elevation, ↑ stroke risk → anticoagulate
• LV pseudoaneurysm: contained rupture → emergency surgery

274.1.0.1.7.3 Cardiogenic Shock

• ~ 5-10% of STEMI
• LV failure (>75%), RV failure (5%), mechanical (5%)
• See Ch269 for management (Impella, ECMO, IABP)
• CULPRIT-SHOCK 2017: only PCI culprit lesion in shock (not complete revasc)

274.1.0.1.7.4 Other

• Pericarditis (early, within 1 week) — friction rub, pleuritic pain → ASA + colchicine
• Dressler syndrome (post-cardiac injury syndrome, 2-10 wk) — fever, pericarditis, pleuritis → ASA / NSAIDs / colchicine
• LV thrombus: especially apical anterior MI; anticoagulate 3 months
• Stroke: from LV thrombus, AF, hypoperfusion

274.1.0.2 🩺 床邊速查

• D2B ≤ 90 min at PCI center; FMC-to-device ≤ 120 min if transfer
• Fibrinolysis door-to-needle ≤ 30 min if no PCI in 120 min
• STEMI ECG: ≥ 1 mm STE in 2 contiguous (V2-V3: ≥ 1.5 ♀, ≥ 2 ♂)
• RV MI: inferior STEMI + V4R STE → fluid bolus, AVOID NTG/morphine
• COMPLETE trial: multi-vessel STEMI → complete revasc; CULPRIT-SHOCK: in shock → culprit only

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