What is the stepwise management of acute myocardial infarction (MI)?

Stepwise Management of Acute Myocardial Infarction

The management of acute myocardial infarction requires immediate diagnosis and reperfusion therapy, with primary PCI being the preferred strategy when available within 120 minutes of STEMI diagnosis, or fibrinolysis when PCI cannot be performed within this timeframe. 1

Initial Assessment and Diagnosis (0-10 minutes)

• Immediate ECG recording and interpretation within 10 minutes of first medical contact 1
• Establish continuous ECG monitoring with defibrillator capacity 1
• Obtain rapid history focusing on chest pain characteristics, radiation, duration, and risk factors
• Assess vital signs and Killip class (indicator of heart failure severity)
• Establish IV access and draw blood for cardiac biomarkers, but do not wait for results to initiate reperfusion 1
• Administer oxygen only if SaO2 <90% (routine oxygen is not recommended) 1

Immediate Management (0-30 minutes)

• Pain relief and anti-thrombotic therapy:

  • Aspirin 160-325 mg (chewed or oral) 2
  • Potent P2Y12 inhibitor (prasugrel or ticagrelor preferred over clopidogrel) 1
  • IV morphine for pain relief if needed
  • Anticoagulation based on reperfusion strategy:
    • For primary PCI: Unfractionated heparin (enoxaparin or bivalirudin as alternatives) 1
    • For fibrinolysis: Enoxaparin (unfractionated heparin as alternative) 1

• Reperfusion strategy decision (time zero = STEMI diagnosis) 1:

  • Primary PCI if available within 120 minutes of STEMI diagnosis
  • Immediate fibrinolysis (within 10 minutes) if PCI not available within 120 minutes
  • Transfer all patients to PCI-capable centers regardless of initial strategy

Reperfusion Therapy (30-120 minutes)

Primary PCI Strategy:

• Alert catheterization laboratory and bypass emergency department if possible 1
• Perform primary PCI with:
  • Routine radial access preferred
  • Drug-eluting stent implantation
  • Avoid routine thrombus aspiration or deferred stenting 1
• Consider non-infarct related artery PCI:
  • For severe stenosis, before hospital discharge
  • During index procedure if cardiogenic shock present 1

Fibrinolytic Strategy:

• Administer fibrin-specific agent (tenecteplase, alteplase, or reteplase) 1
• Add clopidogrel to aspirin 1
• Transfer immediately to PCI-capable center after fibrinolysis 1
• Perform emergency angiography and PCI if:
  • Fibrinolysis fails (<50% ST-segment resolution at 60-90 min)
  • Hemodynamic/electrical instability occurs
  • Heart failure/shock develops 1
• If fibrinolysis successful, perform angiography and PCI of infarct-related artery between 2-24 hours 1

Early In-Hospital Care (First 24-48 hours)

• Pharmacological therapy:

  • IV beta-blockers (if hemodynamically stable):
    • Metoprolol tartrate: three 5 mg IV boluses at 2-minute intervals 3
    • Follow with oral metoprolol 50 mg every 6 hours for 48 hours, then 100 mg twice daily 3
    • Avoid in hypotension, acute heart failure, AV block or severe bradycardia 1
  • ACE inhibitors within 24 hours for patients with:
    • Anterior infarction
    • Heart failure
    • LVEF <40% 1, 2
  • High-intensity statin therapy regardless of baseline cholesterol 1, 2

• Monitoring:

  • Continue ECG monitoring for at least 24 hours 2
  • Monitor vital signs and ST-segment recovery
  • Consider invasive monitoring with arterial line/pulmonary artery catheter in cardiogenic shock 2

• Imaging:

  • Perform echocardiography to assess LV and RV function and detect mechanical complications 1

Subsequent Care (48 hours to discharge)

• Continue dual antiplatelet therapy (DAPT) with aspirin plus P2Y12 inhibitor 1
• Add proton pump inhibitor for patients at high risk of gastrointestinal bleeding 1
• Monitor for and manage complications:
  • Heart failure
  • Arrhythmias
  • Mechanical complications (ventricular septal rupture, papillary muscle rupture, free wall rupture)
• Consider early ambulation and discharge for uncomplicated patients 1
• Plan for cardiac rehabilitation referral 1, 2

Discharge Planning and Secondary Prevention

• Medication regimen:

  • Continue DAPT for 12 months 1
  • Long-term beta-blocker therapy, especially for patients with heart failure or LVEF <40% 1
  • ACE inhibitors/ARBs for patients with heart failure, hypertension, diabetes, or LVEF <40% 1
  • High-intensity statin therapy with LDL-C goal <1.8 mmol/L (70 mg/dL) 1

• Lifestyle modifications:

  • Smoking cessation with support and pharmacotherapy 1, 2
  • Regular physical activity and cardiac rehabilitation participation 1, 2
  • Diet low in saturated fat and cholesterol 2
  • Weight management 2

Special Considerations

• Women: May present with atypical symptoms (up to 30%) and later than men, but should receive the same evidence-based treatments 2
• Elderly: May require dose adjustments of antithrombotic therapy due to higher bleeding risk 1
• Renal insufficiency: Requires careful dose adjustment of medications 1
• Cardiac arrest: Primary PCI strategy indicated for patients with post-resuscitation ECG showing ST-elevation 1
• MINOCA (MI with non-obstructive coronary arteries): Requires additional diagnostic tests to identify etiology and tailor therapy 1

Common Pitfalls to Avoid

• Delaying reperfusion while waiting for cardiac biomarker results 1, 2
• Failing to transfer patients to PCI-capable centers after fibrinolysis 1
• Using calcium channel blockers as first-line therapy 2
• Discontinuing beta-blockers prematurely 2
• Neglecting cardiac rehabilitation referral 1, 2
• Administering routine oxygen to patients with normal oxygen saturation 1