Management of Myocardial Infarction (MI)

Overview Diagram (STEMI)

FLOWCHART: Management of Acute MI

SUSPECTED MI (Chest pain > 10-20 min + diaphoresis/dyspnea)
              ↓
    IMMEDIATE ASSESSMENT (within 10 min)
    • 12-lead ECG
    • IV access + cardiac monitoring
    • Serial troponin (high-sensitivity)
    • CXR, CBC, electrolytes, coagulation
              ↓
    ┌─────────────────────────────────────┐
    │         STEMI                        │  ← ST elevation ≥ 1mm in ≥2 contiguous leads
    │         (Complete occlusion)         │     OR new LBBB
    └─────────────────────────────────────┘
              ↓
    ┌─────────────────────────────────────────────────────┐
    │         IMMEDIATE PHARMACOTHERAPY (MONA + more)      │
    └─────────────────────────────────────────────────────┘
    • Morphine IV (pain, anxiety)
    • Oxygen (if SpO₂ < 90%)
    • Nitrates (sublingual/IV if no hypotension)
    • Aspirin 162-325 mg (chewed)
    • P2Y₁₂ inhibitor (Ticagrelor 180 mg OR Clopidogrel 600 mg)
    • Anticoagulation: UFH or LMWH (enoxaparin)
    • β-blocker (oral, within 24h if no contraindication)
    • Statin (high-intensity: atorvastatin 80 mg)
              ↓
    ┌─────────────────────────────────────────────────────┐
    │             REPERFUSION STRATEGY                     │
    └─────────────────────────────────────────────────────┘
           ↓                             ↓
   PCI available?                  PCI NOT available /
   Door-to-balloon ≤ 90 min?       Delay > 120 min?
           ↓                             ↓
  PRIMARY PCI (preferred)       FIBRINOLYTIC THERAPY
  - Stenting of culprit artery   - tPA (alteplase) preferred over SK
  - Best outcomes overall        - Door-to-needle < 30 min
  - Less re-infarction           - Within 12h of symptom onset
  - Fewer intracranial bleeds    - Then transfer for PCI (rescue PCI
                                   if lysis fails; elective PCI 3-24h)
              ↓
    CARDIOGENIC SHOCK → Primary PCI immediately
    (fibrinolysis NOT recommended in shock)
              ↓
    ┌──────────────────────────────────────────┐
    │         POST-MI / LONG-TERM THERAPY       │
    └──────────────────────────────────────────┘
    • Dual antiplatelet (Aspirin + P2Y₁₂) → at least 12 months
    • ACE inhibitor / ARB → especially if EF reduced or anterior MI
    • β-blocker → continue long-term (reduces mortality)
    • High-intensity statin (atorvastatin/rosuvastatin)
    • Complete revascularization of non-culprit vessels (at same or
      subsequent procedure, except in cardiogenic shock)
    • Cardiac rehabilitation
    • Lifestyle modification

KEY POINTS (Bullet Summary)

1. Initial Stabilization ("MONA")

• M - Morphine: relieves pain and reduces sympathetic activation
• O - Oxygen: only if SpO₂ < 90% (routine O₂ is no longer recommended)
• N - Nitrates: sublingual/IV for chest pain relief (avoid if SBP < 90 mmHg or RV infarct)
• A - Aspirin: 162-325 mg chewed immediately (inhibits TXA₂-mediated platelet aggregation)

2. Antiplatelet / Antithrombotic Therapy

• Add a P2Y₁₂ inhibitor: Ticagrelor (preferred) or Clopidogrel
• Anticoagulation: UFH bolus + infusion OR enoxaparin (LMWH)
• Duration: dual antiplatelet for ≥12 months post-stent

3. Reperfusion - The Most Important Goal

• Preferred thrombolytics: Tenecteplase (single bolus) or Reteplase (double bolus) - more convenient than alteplase
• Streptokinase is less preferred (lower patency rates)

4. Adjunctive Medications

• β-blocker (metoprolol): within 24h; reduce HR, BP, arrhythmia risk - avoid in acute LVF/cardiogenic shock
• ACE inhibitor (ramipril/lisinopril): start within 24h, especially anterior MI or EF <40%
• High-intensity statin: Atorvastatin 40-80 mg - started immediately, continued indefinitely

5. Complications to Monitor

• Arrhythmias: VT/VF (most common cause of early death) - defibrillation/antiarrhythmics
• Cardiogenic shock: requires emergent PCI + inotropes (dobutamine) ± IABP
• Acute LVF/pulmonary edema: diuretics + vasodilators
• Mechanical complications: free wall rupture, VSD, papillary muscle rupture (surgical emergency)
• RV infarction (inferior STEMI): avoid nitrates + diuretics; give IV fluids

6. Secondary Prevention (Long-term)

• Dual antiplatelet → aspirin lifelong + P2Y₁₂ for 12 months
• ACE inhibitor + β-blocker + statin → lifelong
• Aldosterone antagonist (eplerenone) if EF <40% + symptoms
• Cardiac rehab, exercise, smoking cessation, BP and diabetes control

"MONAB + PCI/Thrombolysis + ABCDES"

• Aspirn + Anticoagulation
• Beta-blocker
• Cholesterol (statin)
• Dual antiplatelet
• Eplerenone (if EF low)
• Secondary prevention