What is the medical management of myocardial infarction (MI)?

Medical Management of Myocardial Infarction

The medical management of myocardial infarction requires immediate administration of aspirin 160-325 mg, prompt reperfusion therapy within 12 hours of symptom onset via fibrinolysis or PCI, followed by dual antiplatelet therapy, beta-blockers, and other evidence-based medications to reduce mortality and morbidity. 1

Initial Management

Immediate Interventions

• Aspirin: Administer 162-325 mg immediately upon symptom recognition (patient should chew the tablet) 2, 1
• Reperfusion therapy: For STEMI patients presenting within 12 hours of symptom onset 2
  • Primary PCI (preferred if available within 90 minutes)
  • Fibrinolysis (if PCI not available within required timeframe)
• Antiplatelet therapy:
  • Add clopidogrel 75 mg daily regardless of reperfusion strategy 2
  • Duration varies based on stent type (no stent: 14 days; bare-metal: at least 1 month but ideally 1 year; drug-eluting: 1 year) 2
• Pain management: Administer adequate analgesia with morphine sulfate (4-8 mg IV initially, with 2-8 mg IV every 5-15 minutes as needed) 1
• Oxygen: Provide 2-4 L/min if breathlessness or heart failure are present 1

First 24 Hours

• Continuous monitoring: ECG monitoring for arrhythmia detection 2, 1
• Beta-blockers:
  • IV metoprolol: Three bolus injections of 5 mg at approximately 2-minute intervals 3
  • Follow with oral therapy within 24 hours if no contraindications 2, 3
• Nitroglycerin: IV infusion for 24-48 hours if no hypotension, bradycardia, or tachycardia 2, 1
• Anticoagulation: Consider heparin for patients with large anterior MI or LV mural thrombus 2, 1
• Emergency equipment: Ensure atropine, lidocaine, transcutaneous pacing patches, defibrillator, and epinephrine are readily available 2, 1

Ongoing Management (After First 24 Hours)

• Aspirin: Continue 160-325 mg daily indefinitely 2, 1
• Beta-blockers: Continue IV beta-blockers for at least 6 weeks, then transition to oral therapy 2
• Nitroglycerin: Continue IV infusion for 24-48 hours 2, 1
• Magnesium sulfate: Give as needed to replete magnesium deficits for 24 hours 2
• Anticoagulation: For patients receiving alteplase, continue IV heparin for an additional 48 hours 2
• Discontinue NSAIDs: Patients who routinely took NSAIDs (except aspirin) should discontinue these due to increased risks of mortality, reinfarction, and heart failure 2

Management of Complications

Cardiogenic Shock

• Consider intra-aortic balloon pump, emergency coronary angiography, and revascularization 2, 1
• For right ventricular infarction with hypotension: Aggressive intravascular volume expansion with normal saline and inotropic agents 2, 1

Heart Failure

• Administer IV furosemide and afterload-reducing agents 2, 1

Recurrent Chest Pain

• Pericarditis: High-dose aspirin (650 mg every 4-6 hours) 2
• Ischemia: IV nitroglycerin, analgesics, and antithrombotic medications (aspirin, heparin) 2
• Consider coronary angiography with subsequent revascularization therapy 2

Preparation for Discharge

• Exercise testing: Perform submaximal test at 4-7 days or symptom-limited at 10-14 days 2, 1
• Medication regimen:
  • Aspirin 160-325 mg daily indefinitely 2, 1
  • Beta-blocker for at least 6 weeks 2, 1
  • ACE inhibitor at appropriate dose 1
  • Consider prasugrel as an alternative to clopidogrel in appropriate patients 4
    • Note: Prasugrel is contraindicated in patients with history of TIA/stroke or active bleeding 4
    • Not recommended for patients ≥75 years except in high-risk situations (diabetes or prior MI) 4

Important Considerations and Pitfalls

• Aspirin dosing: While both low-dose (≤200 mg) and high-dose (>200 mg) aspirin are used, high-dose aspirin may increase bleeding risk without additional ischemic benefit 5, 6
• Beta-blocker caution: IV beta-blockers should not be given routinely to all STEMI patients; they may be considered for treatment of hypertension if no contraindications exist 2
• Prasugrel bleeding risk: Increased risk in patients <60 kg (consider 5 mg maintenance dose), those with propensity to bleed, and with concomitant medications that increase bleeding risk 4
• Reperfusion timing: The benefit of reperfusion therapy is time-dependent, with greatest benefit when initiated within the first hour of symptom onset 1
• Calcium channel blockers: Have not been shown to reduce mortality in acute MI patients and may be harmful in certain patients with cardiovascular disease 2

By following this evidence-based approach to MI management, focusing on immediate reperfusion, antiplatelet therapy, and appropriate adjunctive medications, patient outcomes can be significantly improved with reduced mortality and morbidity.