What is the immediate management of a patient with ST-Elevation Myocardial Infarction (STEMI)?

Immediate Management of ST-Elevation Myocardial Infarction (STEMI)

All STEMI patients should receive immediate aspirin (162-325 mg chewed, non-enteric coated) at first medical contact, followed by urgent reperfusion therapy with primary PCI within 90 minutes of first medical contact or fibrinolytic therapy within 30 minutes if PCI cannot be achieved within 120 minutes. 1, 2

Initial Prehospital and Emergency Department Actions

Immediate Medications (Within Minutes of Diagnosis)

• Aspirin 162-325 mg should be chewed immediately upon STEMI recognition unless absolute contraindication exists 1, 2
• Supplemental oxygen should be administered only if arterial saturation is <90% or if pulmonary congestion is present 2
• Morphine sulfate should be given for ongoing ischemic pain or pulmonary congestion 2
• Oral beta-blocker should be administered promptly to patients without contraindications (avoid in frank cardiac failure, pulmonary congestion, or low-output state) 1, 2
• Intravenous beta-blockers should NOT be given routinely to STEMI patients, but may be considered only for hypertension or tachyarrhythmias if no contraindications exist 1, 2

Critical Time-Dependent Decision: Reperfusion Strategy

The fundamental decision point is whether primary PCI can be performed within 120 minutes of first medical contact (or 90 minutes for patients <75 years with large anterior infarction presenting within 2 hours of symptom onset) 1:

If Primary PCI is achievable within these timeframes:

• Transfer patient directly to catheterization laboratory, bypassing emergency department 1
• Administer potent P2Y12 inhibitor (prasugrel 60 mg loading dose or ticagrelor) before or at time of PCI 1, 2
• Use clopidogrel 600 mg only if prasugrel/ticagrelor unavailable or contraindicated 1
• Target door-to-balloon time of 90 minutes 1, 2

If Primary PCI cannot be achieved within these timeframes:

• Initiate fibrinolytic therapy within 30 minutes of first medical contact 1
• Use fibrin-specific agents (tenecteplase, alteplase, or reteplase) 1
• Administer clopidogrel 75 mg (not prasugrel) in addition to aspirin 1
• Provide anticoagulation with enoxaparin IV followed by subcutaneous (preferred over unfractionated heparin) 1
• Transfer all patients to PCI-capable facility immediately after fibrinolysis 1

Anticoagulation During Primary PCI

• Unfractionated heparin should be given as weight-adjusted IV bolus (60 U/kg, maximum 4000 U) followed by infusion (12 U/kg/hr, maximum 1000 U/hr) targeting aPTT 1.5-2.0 times control 1
• Bivalirudin is an alternative, particularly in patients with high bleeding risk 3
• Fondaparinux is contraindicated for primary PCI 1

Post-Fibrinolysis Management Algorithm

After fibrinolytic administration, assess ST-segment resolution at 60-90 minutes 1:

If <50% ST-segment resolution:

• Perform immediate rescue PCI 1

If successful fibrinolysis (≥50% ST-segment resolution):

• Perform angiography and PCI of infarct-related artery between 2-24 hours after successful fibrinolysis 1

If hemodynamic instability, heart failure, or recurrent ischemia at any time:

• Perform emergency angiography and PCI immediately 1

Special Populations Requiring Immediate Transfer

Cardiogenic shock patients <75 years:

• Transfer immediately to PCI-capable facility for revascularization (PCI or CABG) if it can be performed within 18 hours of shock onset (Class I recommendation) 1

Cardiogenic shock patients ≥75 years:

• Consider immediate transfer for revascularization within 18 hours, especially in high-risk situations (diabetes, prior MI) 1

Contraindications to fibrinolysis:

• Transfer immediately to PCI-capable facility with door-to-departure time <30 minutes 1

Critical Pitfalls to Avoid

• Do NOT delay aspirin while waiting for other medications or procedures 1
• Do NOT give IV beta-blockers routinely—this increases mortality risk 1
• Do NOT perform routine PCI of occluded infarct-related artery >48 hours after symptom onset in asymptomatic patients 1
• Do NOT use prasugrel in patients with prior stroke/TIA (absolute contraindication) or age ≥75 years (unless high-risk features present, then use 5 mg maintenance dose) 4
• Do NOT delay fibrinolysis beyond 30 minutes if primary PCI is not achievable within target timeframes 1

Dual Antiplatelet Therapy Duration

• Continue aspirin plus P2Y12 inhibitor for 12 months after PCI regardless of stent type (bare-metal or drug-eluting) 1, 3
• Prasugrel 10 mg daily (or 5 mg daily if ≥75 years or <60 kg body weight) is preferred over clopidogrel 75 mg daily 1, 4
• Add proton pump inhibitor in patients at high gastrointestinal bleeding risk 1

Additional Early Therapies (Within 24 Hours)

• ACE inhibitors should be initiated within 24 hours in patients with anterior STEMI, heart failure, or ejection fraction ≤40% 2
• High-intensity statin therapy should be initiated or continued in all patients without contraindications 2
• Echocardiography should be performed during hospital stay to assess LV/RV function, detect mechanical complications, and exclude LV thrombus 1