What are the treatments for acute myocardial infarction (AMI)?

Treatments for Acute Myocardial Infarction (AMI)

The cornerstone treatments for acute myocardial infarction include immediate reperfusion therapy (preferably primary PCI within 120 minutes of diagnosis or fibrinolysis if PCI is unavailable), antiplatelet therapy with aspirin plus a P2Y12 inhibitor, anticoagulation during the acute phase, and subsequent medical therapy including beta-blockers, ACE inhibitors, and high-intensity statins. 1

Initial Management

Immediate Interventions

• Reperfusion therapy:
  • Primary PCI: Preferred treatment if available within 120 minutes of STEMI diagnosis 2
  • Fibrinolytic therapy: Recommended when PCI cannot be performed in a timely manner (within 12 hours of symptom onset) 2
  • Immediate transfer to PCI-capable center without waiting for signs of persistent ischemia 1

Antiplatelet Therapy

• Aspirin: Loading dose of 162-325 mg (non-enteric coated, crushed or chewed) followed by 81 mg daily indefinitely 2
• P2Y12 inhibitor: Prasugrel or ticagrelor preferred over clopidogrel, to be continued for 12 months 2
• Dual antiplatelet therapy (DAPT): Combination of aspirin and a P2Y12 inhibitor for 12 months after PCI 2

Anticoagulation

• For primary PCI: Unfractionated heparin (70-100 U/kg) 1
• For fibrinolysis: Enoxaparin (preferred) or unfractionated heparin until revascularization or hospital discharge 2

Hospital Phase Management

Pharmacological Therapy

• Beta-blockers:

  • IV metoprolol followed by oral therapy in hemodynamically stable patients 3
  • Contraindicated in hypotension, acute heart failure, AV block, or severe bradycardia 2
  • Metoprolol tartrate 50 mg every 6 hours initially, then 100 mg twice daily 3

• ACE inhibitors:

  • Start within 24 hours in patients with heart failure, LV systolic dysfunction, diabetes, or anterior infarct 2
  • ARBs (preferably valsartan) are alternatives for ACE inhibitor-intolerant patients 2

• Statins:

  • High-intensity statin therapy started as early as possible 2
  • Target LDL-C < 70 mg/dL or reduction of at least 50% if baseline is 70-135 mg/dL 2

• Nitrates:

  • IV nitroglycerin for 24-48 hours after hospitalization in patients without hypotension, bradycardia, or excessive tachycardia 2
  • Should not be used as substitute for narcotic analgesics 2

• Mineralocorticoid receptor antagonists (MRAs):

  • For patients with ejection fraction < 40% and heart failure or diabetes 2

Management of Complications

• Heart failure:

  • Diuretics (usually IV furosemide) and afterload-reducing agents 2
  • For cardiogenic shock, consider hemodynamic support devices 2

• Right ventricular infarction:

  • Intravascular volume expansion with normal saline and inotropic agents if hypotension persists 2

• Recurrent chest pain:

  • If due to pericarditis: high-dose aspirin (650 mg every 4-6 hours) 2
  • If due to ischemia: IV nitroglycerin, analgesics, and antithrombotic medications 2

Post-Discharge Management

Secondary Prevention

• Antiplatelet therapy:

  • Aspirin 75-100 mg daily indefinitely 2
  • DAPT for 12 months after PCI 2
  • Consider PPI for patients at high risk of GI bleeding 2

• Beta-blockers:

  • Continue indefinitely, especially in patients with reduced ejection fraction 2

• ACE inhibitors/ARBs:

  • Continue indefinitely in patients with heart failure, LV dysfunction, hypertension, or diabetes 2

• Statins:

  • Continue high-intensity statin therapy long-term 2

• Lifestyle modifications:

  • Smoking cessation with support, nicotine replacement, varenicline, and bupropion 2
  • Participation in cardiac rehabilitation program 2
  • Regular physical activity 1
  • Diet low in saturated fat and cholesterol 2
  • Weight management 1

Follow-up

• Standard exercise testing before discharge or shortly thereafter (submaximal at 4-7 days or symptom-limited at 10-14 days) 2
• Echocardiography to assess LV and RV function and detect complications 2
• Regular monitoring of cardiac symptoms and medication adherence 1

Special Considerations

Fibrinolytic Therapy Protocol

• Initiate as soon as possible after STEMI diagnosis, preferably pre-hospital 2
• Use fibrin-specific agent (tenecteplase, alteplase, or reteplase) 2
• Transfer to PCI-capable center immediately after fibrinolysis 2
• Perform angiography and PCI of the infarct-related artery between 2-24 hours after successful fibrinolysis 2

Pharmacoinvasive Strategy

• Only indicated when patient is within thrombolysis window and transfer to PCI center would cause significant delays 1
• Emergency angiography indicated if fibrinolysis fails (<50% ST-segment resolution at 60-90 minutes) 2

Common Pitfalls and Caveats

• Delaying reperfusion therapy increases mortality in a non-linear fashion 1
• Calcium channel blockers have not been shown to reduce mortality and may be harmful in certain patients 2
• Avoid IV beta-blockers in patients with hypotension, acute heart failure, or AV block 2
• Do not use fondaparinux for primary PCI 2
• Routine PCI of an occluded infarct-related artery >48 hours after STEMI onset is not indicated in asymptomatic patients 2