What is the recommended initial management for a patient presenting with acute ST‑segment elevation myocardial infarction (STEMI)?

Initial Management of STEMI

Immediately obtain a 12-lead ECG within 10 minutes of first medical contact, initiate continuous ECG monitoring with defibrillator capacity, administer aspirin loading dose, and select your reperfusion strategy: primary PCI if achievable within 120 minutes of diagnosis, otherwise initiate fibrinolysis within 10 minutes. 1, 2

Immediate Diagnostic Actions

• Obtain and interpret a 12-lead ECG within 10 minutes of first medical contact, whether pre-hospital or in the emergency department 1, 2
• Initiate continuous ECG monitoring with defibrillator capacity immediately upon patient contact 1
• Look beyond classic ST-elevation patterns—recognize STEMI equivalents including new bundle branch block, ventricular pacing, hyperacute T-waves, isolated ST-depression in anterior leads, or universal ST-depression with ST-elevation in aVR 1, 2

Initial Medical Therapy (Administer Immediately)

• Aspirin loading dose (oral or IV if unable to swallow) as soon as possible 1, 2, 3
• Oxygen only if SaO₂ <90%—routine oxygen administration is contraindicated in patients with adequate oxygen saturation 1, 2

Reperfusion Strategy Selection (Time Zero = ECG Diagnosis)

The 2017 ESC guidelines provide clear time-based decision making: 1, 2

Choose Primary PCI if:

• PCI can be performed within 120 minutes of STEMI diagnosis 1, 2
• Administer prasugrel or ticagrelor loading dose (not clopidogrel) before or at the time of PCI 1, 2
• Administer unfractionated heparin as first-line anticoagulant (enoxaparin or bivalirudin are alternatives) 1, 2
• Use radial access as the standard approach 1, 2
• Implant drug-eluting stents routinely 1, 2

Choose Immediate Fibrinolysis if:

• Primary PCI cannot be performed within 120 minutes of STEMI diagnosis 1, 2
• Patient presents within 12 hours of symptom onset 1, 3
• No contraindications exist 1
• Initiate within 10 minutes of STEMI diagnosis 1, 2
• Use a fibrin-specific agent: tenecteplase (preferred), alteplase, or reteplase 3, 4
• Administer clopidogrel loading dose (not prasugrel or ticagrelor initially) 1, 3
• Administer enoxaparin (IV bolus followed by subcutaneous)—preferred over unfractionated heparin 1, 3

Critical Technical Details for Primary PCI

• Do not perform routine thrombus aspiration—this is contraindicated 1, 2
• Do not perform routine deferred stenting—this is contraindicated 1, 2
• Transfer patients directly to the catheterization laboratory, bypassing the emergency department and ICU 1

Post-Fibrinolysis Pathway (Pharmacoinvasive Approach)

• Transfer all patients to a PCI-capable center immediately after fibrinolysis, regardless of apparent success 2, 3
• Perform routine angiography between 2-24 hours after successful fibrinolysis 2, 3
• Switch from clopidogrel to prasugrel or ticagrelor at the time of PCI 2, 3

Tenecteplase Dosing (Weight-Based)

The FDA-approved dosing for tenecteplase is administered as a single IV bolus over 5 seconds: 4

• <60 kg: 30 mg (6 mL)
• 60 to <70 kg: 35 mg (7 mL)
• 70 to <80 kg: 40 mg (8 mL)
• 80 to <90 kg: 45 mg (9 mL)
• ≥90 kg: 50 mg (10 mL)

Flush dextrose-containing IV lines with 0.9% sodium chloride before and after tenecteplase administration to prevent precipitation 4

Post-Reperfusion Care

• Monitor for at least 24 hours after reperfusion therapy 1, 2
• Pursue early ambulation and early discharge in uncomplicated patients 1, 2

Maintenance Antithrombotic Therapy

• Dual antiplatelet therapy with aspirin plus prasugrel or ticagrelor for 12 months after PCI 1, 2
• For patients initially treated with fibrinolysis and clopidogrel, transition to prasugrel or ticagrelor at the time of angiography/PCI 2, 3

Special Consideration: Cardiac Arrest

• Perform primary PCI in patients with resuscitated cardiac arrest and ST-elevation on post-resuscitation ECG 1, 2
• Initiate targeted temperature management early in patients who remain unresponsive after resuscitation 1, 2

Critical Pitfalls to Avoid

• Never use prasugrel or ticagrelor as the initial P2Y12 inhibitor with fibrinolytic therapy—clopidogrel is specifically indicated in this setting, with transition to potent agents only at the time of PCI 2, 3
• Never delay transfer to a PCI-capable center after fibrinolysis—all patients require angiography regardless of apparent lysis success 2, 3
• Never perform routine thrombus aspiration or deferred stenting during primary PCI—these strategies are contraindicated by current guidelines 1, 2
• Never administer routine oxygen to patients with SaO₂ ≥90%—this is contraindicated 1, 2