What is the management of myocardial infarction (MI)?

Management of Myocardial Infarction

For patients with STEMI presenting within 12 hours of symptom onset, immediate reperfusion with primary PCI is the preferred strategy when it can be performed within 120 minutes of diagnosis; if not, fibrinolytic therapy should be initiated immediately, preferably in the pre-hospital setting. 1

Immediate Initial Management

Pharmacological Therapy - First Line

• Aspirin 160-325 mg should be administered immediately (oral or IV if unable to swallow) to all patients without contraindications 1, 2
• After the acute phase, continue aspirin 75-100 mg daily indefinitely 1, 2

Reperfusion Strategy Decision Algorithm

If Primary PCI can be performed within 120 minutes:

• Transfer patient directly to catheterization laboratory, bypassing emergency department 1
• Administer a potent P2Y12 inhibitor (prasugrel or ticagrelor preferred over clopidogrel) before or at the time of PCI 1
• Continue dual antiplatelet therapy (DAPT) with aspirin plus P2Y12 inhibitor for 12 months unless excessive bleeding risk 1, 2

If Primary PCI cannot be performed within 120 minutes:

• Initiate fibrinolytic therapy immediately within 12 hours of symptom onset 1, 3
• Use a fibrin-specific agent: tenecteplase, alteplase, or reteplase 1, 3
• For patients ≥75 years old, reduce tenecteplase dose by 50% to minimize stroke risk 3
• Administer clopidogrel in addition to aspirin 1, 4
• Provide anticoagulation with enoxaparin IV followed by subcutaneous (preferred over unfractionated heparin) until revascularization or up to 8 days of hospitalization 1, 3
• Fondaparinux is contraindicated for primary PCI 1

Post-Fibrinolysis Management Protocol

Assessment at 60-90 Minutes

• Measure ST-segment resolution in the lead with greatest initial ST elevation 3
• <50% ST-segment resolution = failed fibrinolysis 3

Failed Fibrinolysis (<50% ST-segment resolution):

• Perform rescue PCI immediately 1, 3
• Also perform rescue PCI for hemodynamic instability, electrical instability, worsening ischemia, or cardiogenic shock at any time 1, 3

Successful Fibrinolysis (≥50% ST-segment resolution):

• Transfer all patients to PCI-capable center immediately after fibrinolysis 1, 3
• Perform angiography and PCI of infarct-related artery between 2-24 hours after successful fibrinolysis 1, 3
• Perform emergency angiography immediately for heart failure, cardiogenic shock, recurrent ischemia, or evidence of reocclusion 1, 3

Critical Pitfall: Do not routinely combine fibrinolysis with planned immediate PCI, as this increases mortality 3

Beta-Blocker Therapy

Early Phase (Acute MI)

• For hemodynamically stable patients, initiate metoprolol 5 mg IV at approximately 2-minute intervals for three doses 5
• Monitor blood pressure, heart rate, and ECG during IV administration 5
• 15 minutes after last IV dose, begin oral metoprolol 50 mg every 6 hours for 48 hours if full IV dose tolerated 5
• Avoid IV beta-blockers in patients with hypotension, acute heart failure, AV block, or severe bradycardia 1, 5

Long-Term Maintenance

• Continue oral beta-blocker therapy indefinitely in patients with heart failure and/or LVEF <40% unless contraindicated 1, 2
• Maintenance dosage is typically 100 mg orally twice daily 5

ACE Inhibitor Therapy

• Start ACE inhibitor within first 24 hours of STEMI in patients with heart failure, LV systolic dysfunction, diabetes, or anterior infarction 2
• For lisinopril: initiate 5 mg within 24 hours of symptom onset, 5 mg after 24 hours, then 10 mg daily 6
• Reduce dose to 2.5 mg if systolic blood pressure <120 mmHg at baseline 6
• Continue ACE inhibitors indefinitely 2

Important Caveat: ACE inhibitors increase risk of persistent hypotension (9.0% vs 3.7%) and renal dysfunction (2.4% vs 1.1%) in acute MI patients 6

Statin Therapy

• Initiate high-intensity statin therapy as early as possible and maintain long-term 1, 2

Management of Complications

Heart Failure

• Administer IV furosemide and an afterload-reducing agent 2

Cardiogenic Shock

• Consider intra-aortic balloon counterpulsation 2
• Perform emergency coronary angiography followed by PCI or CABG 2

In-Hospital Assessment

• Perform routine echocardiography during hospital stay to assess LV and RV function, detect mechanical complications, and exclude LV thrombus 1, 2

PPI Co-Therapy

• Prescribe PPI in combination with DAPT for patients at high risk of gastrointestinal bleeding 1

Secondary Prevention and Discharge Planning

Smoking Cessation

• Identify smokers and provide repeated advice with follow-up support, nicotine replacement therapies, varenicline, and bupropion individually or in combination 1

Cardiac Rehabilitation

• Mandatory participation in cardiac rehabilitation program 1, 2

Lifestyle Modifications

• Achieve ideal weight with diet low in saturated fat and cholesterol 2
• Encourage regular exercise (at least 20 minutes of brisk walking three times weekly) 2

Special Consideration: In asymptomatic patients >48 hours after STEMI onset, routine PCI of an occluded infarct-related artery is not indicated 1, 3