How to manage a case of myocardial infarction (MI)?

Management of Myocardial Infarction

Immediate reperfusion therapy is the cornerstone of management for myocardial infarction patients presenting within 12 hours of symptom onset, with primary PCI being the preferred strategy when available within 90 minutes of first medical contact. 1, 2

Initial Assessment and Management

• Immediate measures:
  • Administer oxygen (2-4 L/min) if breathlessness or heart failure are present 2
  • Administer aspirin 162-325 mg immediately (chewed) 2
  • Perform 12-lead ECG immediately to guide reperfusion decisions 2
  • Administer sublingual nitroglycerin unless systolic BP <90 mmHg or heart rate <50 or >100 bpm 2
  • Provide analgesia with morphine sulfate (4-8 mg IV initially, with 2-8 mg IV every 5-15 minutes as needed) 2

Reperfusion Strategy

For STEMI patients:

1. Primary PCI (preferred approach):

   • Recommended when available within 90 minutes of first medical contact 1, 2
   • Patients should bypass emergency department and be transferred directly to catheterization laboratory 1
   • Administer dual antiplatelet therapy:
     • Aspirin 160-325 mg 1, 2
     • A potent P2Y12 inhibitor (prasugrel or ticagrelor), or clopidogrel if these are not available 1, 3

2. Fibrinolytic therapy (if timely PCI not available):

   • Initiate as soon as possible, preferably pre-hospital 1
   • Use a fibrin-specific agent (tenecteplase, alteplase, or reteplase) 1
   • Administer with:
     • Aspirin (oral or IV) 1
     • Clopidogrel 1, 3
     • Anticoagulation (enoxaparin preferred over UFH) 1
   • Transfer to PCI-capable center immediately after fibrinolysis 1
   • Perform angiography and PCI of the infarct-related artery between 2-24 hours after successful fibrinolysis 1

Pharmacological Management

Antiplatelet Therapy

• Aspirin: 160-325 mg initially, then 75-100 mg daily indefinitely 1, 2, 4
• P2Y12 inhibitor: In addition to aspirin for 12 months 1, 3
  • Clopidogrel 75 mg daily (after loading dose) 3
  • Prasugrel or ticagrelor preferred if no contraindications 1

Beta-Blockers

• Early IV administration followed by oral therapy 1, 2, 5
• For metoprolol: Three 5 mg IV boluses at 2-minute intervals, followed by 50 mg orally every 6 hours for 48 hours, then 100 mg twice daily maintenance 5
• Contraindicated in cardiogenic shock, severe bradycardia, high-degree AV block, or severe bronchospasm 5

Other Medications

• ACE inhibitors: Start within 24 hours in patients with anterior infarction, heart failure, or ejection fraction <40% 2
• Statins: High-intensity statin therapy regardless of baseline cholesterol levels 2
• Nitroglycerin: IV for ongoing chest pain, heart failure, or hypertension 1, 2

Management of Complications

Cardiogenic Shock

• Consider intra-aortic balloon pump and emergency coronary angiography followed by PCI or CABG 1, 2
• Administer inotropic agents if hypotension persists 1
• For right ventricular infarction: Aggressive intravascular volume expansion with normal saline 1

Recurrent Chest Pain

• If due to pericarditis: High-dose aspirin (650 mg every 4-6 hours) 1
• If due to ischemia: IV nitroglycerin, analgesics, and antithrombotic medications 1
• Consider coronary angiography with revascularization 1

Heart Failure

• Administer diuretic (usually IV furosemide) 1
• Add afterload-reducing agent 1

Pre-Discharge Assessment

• Perform echocardiography to assess LV and RV function and detect mechanical complications 1
• Conduct exercise testing (submaximal at 4-7 days or symptom-limited at 10-14 days) 1

Long-Term Management

• Medications:

  • Continue aspirin (75-100 mg daily) indefinitely 1
  • Continue beta-blocker therapy 1, 2
  • Continue ACE inhibitor therapy 1, 2
  • Maintain dual antiplatelet therapy for 12 months 1, 3

• Lifestyle modifications:

  • Smoking cessation 1
  • Diet low in saturated fat and cholesterol 1
  • Regular exercise (at least 20 minutes of brisk walking three times weekly) 1
  • Weight management 1
  • Participation in cardiac rehabilitation program 1

• Lipid management:

  • Target LDL <100 mg/dL 1
  • Drug therapy if LDL >130 mg/dL despite diet 1

Common Pitfalls to Avoid

• Delaying reperfusion therapy while waiting for additional tests
• Using calcium channel blockers as first-line therapy (no mortality benefit and potentially harmful) 1
• Failing to transfer patients to PCI-capable centers after fibrinolysis 1
• Discontinuing beta-blockers prematurely (should be continued indefinitely unless contraindicated) 1, 6
• Neglecting cardiac rehabilitation referral (improves outcomes) 1