What is the treatment for acute myocardial infarction (MI)?

Treatment of Acute Myocardial Infarction

Primary percutaneous coronary intervention (PCI) within 120 minutes of first medical contact is the recommended reperfusion strategy for acute myocardial infarction, with immediate fibrinolytic therapy if PCI is not available within this timeframe. 1

Initial Management

1. Immediate Interventions:

   • Aspirin 162-325 mg loading dose immediately 1, 2
   • Oxygen therapy as needed
   • Pain management with appropriate analgesics (e.g., morphine) 3
   • Continuous ECG monitoring 4

2. Reperfusion Strategy:

   • Primary PCI (preferred if available within 120 minutes) 1
   • Fibrinolytic therapy if PCI not available within 120 minutes, followed by transfer to PCI-capable center within 2-24 hours 1
   • During PCI, high-dose intravenous heparin is recommended 4

Pharmacological Management

Antiplatelet Therapy

• Aspirin: Initial dose of 162-325 mg, followed by 75-100 mg daily indefinitely 1
  • Lower dose (81 mg) may be associated with similar efficacy but lower bleeding risk compared to higher dose (325 mg) 2, 5
• P2Y12 inhibitor (in combination with aspirin for 12 months) 1
  • Ticagrelor or prasugrel preferred over clopidogrel 1
• Consider proton pump inhibitor for patients at high risk of gastrointestinal bleeding 1

Beta-Blockers

• Initiate early intravenous beta-blocker therapy followed by oral therapy 4, 1
• For metoprolol: Three bolus injections of 5 mg IV at approximately 2-minute intervals, followed by 50 mg orally every 6 hours for 48 hours, then 100 mg twice daily maintenance 6
• Avoid in patients with hypotension, acute heart failure, AV block, or severe bradycardia 1

ACE Inhibitors

• Start within 24 hours in patients with:
  • Heart failure
  • Left ventricular systolic dysfunction
  • Diabetes
  • Anterior infarct 1
• ARBs (preferably valsartan) for ACE inhibitor-intolerant patients 1

Statins

• High-intensity statin therapy as early as possible
• Goal: LDL-C <70 mg/dL 1

Anticoagulation

• For patients receiving alteplase, continue intravenous heparin for an additional 48 hours 4
• For patients with large anterior MI or LV mural thrombus, early administration of intravenous heparin is recommended 4

Hospital Management (First 24 Hours)

• Continuous ECG monitoring
• Serial ECGs and cardiac biomarkers to confirm diagnosis
• Limited physical activities for at least 12 hours
• Pain and anxiety management with appropriate analgesics
• Have emergency equipment readily available (atropine, lidocaine, transcutaneous pacing patches, defibrillator) 4

Post-Acute Phase Management

• Echocardiography during hospital stay to assess ventricular function 1
• Exercise testing before discharge 1
• Cardiac rehabilitation program 1
• Lifestyle modifications:
  • Smoking cessation
  • Diet low in saturated fat and cholesterol
  • Regular physical activity
  • Blood pressure control (target <130/80 mmHg)
  • Lipid management 1

Common Pitfalls and Caveats

1. Delay in reperfusion therapy: Time is muscle - ensure rapid diagnosis and treatment
2. Inappropriate aspirin dosing: Lower doses (81 mg) may be preferable for maintenance therapy to reduce bleeding risk while maintaining efficacy 2, 5
3. Beta-blocker contraindications: Avoid in hypotension, acute heart failure, AV block, or severe bradycardia 1
4. Calcium channel blockers: Not shown to reduce mortality in acute MI and may be harmful in certain patients 4
5. Medication adherence: Ensure patients understand the importance of continuing all prescribed medications post-discharge

Special Considerations

• For patients already on chronic aspirin therapy presenting with AMI, a loading dose (200-500 mg) provides greater reduction in platelet reactivity than continuing the standard 100 mg dose 7
• Patients discharged on triple therapy (aspirin, thienopyridine, and warfarin) should be carefully monitored for bleeding risk 8