What is the treatment for myocardial infarction?

Treatment of Myocardial Infarction

The optimal treatment for myocardial infarction includes immediate administration of aspirin 162-325 mg (chewed, non-enteric coated), establishing ECG monitoring within 10 minutes of first medical contact, and implementing reperfusion therapy with primary PCI as the preferred strategy for STEMI patients presenting within 12 hours of symptom onset. 1

Initial Assessment and Management

1. Immediate interventions:

   • Obtain 12-lead ECG within 10 minutes of first medical contact
   • Establish ECG monitoring with defibrillator capacity immediately
   • Administer aspirin 162-325 mg (chewed, non-enteric coated) immediately 1
   • Administer sublingual nitroglycerin 0.4 mg every 5 minutes (up to 3 doses) for chest pain if systolic BP >90 mmHg
   • Consider IV nitroglycerin for ongoing pain if no contraindications exist
   • Morphine sulfate (2-4 mg IV, with 2-8 mg IV every 5-15 minutes as needed) may be administered for pain relief

2. Reperfusion therapy:

   • Primary PCI is the preferred strategy for STEMI patients within 12 hours of symptom onset (Class I, Level A) 1
   • Primary PCI is recommended for patients with cardiogenic shock regardless of time delay from MI onset
   • Fibrinolytic therapy should be initiated if primary PCI cannot be performed within 120 minutes of first medical contact

Antiplatelet and Anticoagulant Therapy

• Dual antiplatelet therapy (DAPT):

  • Aspirin 75-100 mg daily indefinitely
  • P2Y12 inhibitor for 12 months:
    • Preferred: Ticagrelor (180 mg loading, then 90 mg twice daily) or prasugrel (60 mg loading, then 10 mg daily)
    • Alternative: Clopidogrel (600 mg loading, then 75 mg daily)

• Anticoagulation:

  • For primary PCI: Bivalirudin monotherapy for patients at high bleeding risk
  • For fibrinolytic therapy: Enoxaparin IV followed by SC (preferred over unfractionated heparin)

Early Pharmacological Management

• Beta-blockers:

  • Start metoprolol tartrate within 24 hours for hemodynamically stable patients 1, 2
  • Initial IV administration: Three bolus injections of 5 mg metoprolol tartrate at approximately 2-minute intervals 2
  • Follow with oral therapy: 50 mg every 6 hours for 48 hours, then 100 mg twice daily maintenance 2
  • For patients with intolerance to full IV dose: Start with 25-50 mg orally every 6 hours 2

• ACE inhibitors:

  • Start within 24 hours for patients with heart failure, LV systolic dysfunction, diabetes, or anterior infarct 1
  • ARBs (preferably valsartan) are an alternative for ACE inhibitor-intolerant patients

• Statins:

  • High-intensity statin therapy should be initiated as early as possible
  • Target LDL-C <70 mg/dL or ≥50% reduction

Management of Complications

• Cardiogenic shock:

  • Consider intra-aortic balloon pump and emergency coronary angiography
  • Follow with PCI or CABG as appropriate

• Right ventricular infarction:

  • Vigorous intravascular volume expansion with normal saline
  • Add inotropic agents if hypotension persists

• Recurrent chest pain:

  • Due to pericarditis: High-dose aspirin (650 mg every 4-6 hours)
  • Due to ischemia: IV nitroglycerin, analgesics, and antithrombotic medications

Post-Discharge Care and Secondary Prevention

• Cardiac rehabilitation is recommended for all patients following MI 1

• Medication continuation:

  • Beta-blockers for patients with heart failure and/or LVEF <40%
  • ACE inhibitors/ARBs for patients with heart failure, LV dysfunction, diabetes, or anterior infarct
  • High-intensity statins
  • DAPT for 12 months
  • Mineralocorticoid receptor antagonists for patients with LVEF <40% and heart failure

• Lifestyle modifications:

  • Smoking cessation with repeated advice and support
  • Diet modification and weight management
  • Regular physical activity

Important Considerations and Pitfalls

• Aspirin dosing: While both 162 mg and 325 mg doses are effective for initial treatment, some evidence suggests 162 mg may have a better safety profile with similar efficacy 3

• Contraindications to avoid:

  • Calcium channel blockers in acute MI (may be harmful)
  • Oral nitrates (use IV nitroglycerin instead)
  • NSAIDs (except aspirin) during hospitalization due to increased risk of mortality, reinfarction, and complications 1
  • Fondaparinux for primary PCI due to risk of catheter thrombosis

• Monitoring requirements:

  • Monitor for at least 24 hours after reperfusion
  • During IV metoprolol administration, closely monitor blood pressure, heart rate, and ECG 2
  • Echocardiography to assess LV/RV function and detect complications