What is the initial treatment plan for a patient with acute myocardial infarction (MI)?

Initial Treatment Plan for Acute Myocardial Infarction (MI)

The initial treatment for acute myocardial infarction must include immediate oxygen administration, aspirin 160-325 mg, adequate analgesia with morphine, and prompt reperfusion therapy for patients with ST-segment elevation or new left bundle branch block. 1, 2

Immediate Emergency Department Management

• On arrival to the emergency department, patients with suspected MI should immediately receive:

  • Oxygen via nasal prongs 1
  • Sublingual nitroglycerin (unless systolic BP <90 mmHg or heart rate <50 or >100 bpm) 1
  • Adequate analgesia with morphine sulfate or meperidine 1, 3
  • Aspirin 160-325 mg orally 1, 4
  • 12-lead ECG within 10 minutes of arrival (ideally) and no more than 20 minutes 1

• For patients with ST-segment elevation ≥1 mV in contiguous leads or new LBBB:

  • Immediate reperfusion therapy is indicated 1, 2
  • Options include fibrinolytic therapy or primary percutaneous coronary intervention (PCI) 1
  • Primary PCI is preferred when available in a timely manner 2
  • If primary PCI cannot be performed promptly, fibrinolytic therapy should be administered within 12 hours of symptom onset 2

Pharmacological Therapy

• Antiplatelet therapy:

  • Aspirin 160-325 mg initially, then 160-325 mg daily indefinitely 1, 2
  • For patients receiving fibrinolytic therapy, consider adding a second antiplatelet agent 5

• Anticoagulation:

  • For patients receiving fibrinolytic therapy, intravenous heparin is recommended for at least 48 hours 1
  • For patients undergoing primary PCI, high-dose intravenous heparin is recommended 1

• Beta-blockers:

  • Early intravenous beta-blocker therapy followed by oral therapy should be initiated in all patients without contraindications 1, 2
  • For metoprolol: administer three 5 mg IV boluses at approximately 2-minute intervals, followed by oral metoprolol 50 mg every 6 hours for 48 hours, then 100 mg twice daily maintenance 6
  • Beta-blockers should be given regardless of whether reperfusion therapy was administered 1

• Nitrates:

  • Intravenous nitroglycerin for 24-48 hours after hospitalization 1
  • Titrate dose according to heart rate and blood pressure 1
  • Not to be used as a substitute for narcotic analgesics 1

• Other medications:

  • Magnesium sulfate as needed to replete magnesium deficits for 24 hours 1
  • ACE inhibitors should be started within 24 hours in patients with anterior infarction, heart failure, or LV dysfunction 2
  • High-intensity statin therapy should be initiated as early as possible 2

Management of Complications

• For heart failure:

  • Administer intravenous furosemide and an afterload-reducing agent 1
  • Monitor hemodynamic status closely 1

• For cardiogenic shock:

  • Consider intra-aortic balloon pump 1
  • Emergency coronary angiography followed by PCI or CABG 1

• For right ventricular infarction with dysfunction:

  • Vigorous intravascular volume expansion with normal saline 1
  • Inotropic agents if hypotension persists 1

• For recurrent chest pain:

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

Common Pitfalls and Caveats

• Delaying reperfusion therapy: Time is myocardium - the greatest benefit occurs when thrombolysis is initiated within 6 hours of symptom onset 1
• Calcium channel blockers: These have not been shown to reduce mortality in acute MI and may be harmful in certain patients 1
• Oral nitrates: Use with caution in acute MI due to inability to titrate the dose in an evolving hemodynamic situation 1
• Aspirin dosing: An initial dose of 162 mg may be as effective as and potentially safer than 325 mg for acute treatment of STEMI 7
• Thrombolytics in non-STEMI: Patients without ST-segment elevation should not receive thrombolytic therapy 1