What is the immediate management of a patient presenting with ST‑segment‑elevation myocardial infarction (STEMI)?

Management of ST-Segment Elevation Myocardial Infarction (STEMI)

Primary percutaneous coronary intervention (PCI) performed within 120 minutes of diagnosis is the definitive reperfusion strategy for STEMI, and every minute of delay increases mortality. 1

Immediate Actions at First Medical Contact (0–10 Minutes)

• Obtain and interpret a 12-lead ECG within 10 minutes of first medical contact, whether pre-hospital or in the emergency department. 2, 1
• Activate the catheterization laboratory immediately upon STEMI diagnosis—do not wait for troponin results, echocardiography, or additional imaging. 1, 3
• Administer aspirin 150–325 mg orally (chewable/soluble) or 250–500 mg intravenously if the patient cannot swallow. 2, 1, 4
• Initiate continuous ECG monitoring with defibrillator capacity because ventricular fibrillation is the most common early arrhythmia. 2, 1, 4
• Provide supplemental oxygen only if oxygen saturation is <90%—routine oxygen in non-hypoxemic patients worsens myocardial injury and is contraindicated. 2, 1, 4

Reperfusion Strategy Selection: The 120-Minute Rule

Primary PCI Pathway (Preferred)

If primary PCI can be performed ≤120 minutes from STEMI diagnosis, proceed directly to the catheterization laboratory. 2, 1

• Transfer the patient directly to the catheterization laboratory, bypassing the emergency department and intensive care unit. 2, 1
• Target door-to-balloon time is <90 minutes for patients presenting directly to a PCI-capable hospital, and <60 minutes if symptom onset is within 2 hours. 1
• Administer a potent P2Y12 inhibitor before or at the time of PCI: prasugrel 60 mg loading dose or ticagrelor 180 mg loading dose; use clopidogrel 600 mg only if prasugrel or ticagrelor are unavailable or contraindicated. 2, 1, 4
• Give unfractionated heparin 100 U/kg IV bolus (reduce to 60 U/kg if a GPIIb/IIIa inhibitor is used); enoxaparin or bivalirudin are acceptable alternatives, but fondaparinux is contraindicated for primary PCI. 2, 1

Technical Standards During Primary PCI

• Use radial artery access as the standard approach to minimize bleeding complications. 1, 4
• Implant drug-eluting stents routinely for the culprit lesion. 1, 4
• Do not perform routine thrombus aspiration or deferred stenting—these strategies are contraindicated. 1, 4

Fibrinolytic Pathway (When PCI >120 Minutes)

If primary PCI cannot be performed within 120 minutes of diagnosis, administer fibrinolytic therapy within 10 minutes of diagnosis. 2, 1

• Use a fibrin-specific agent: tenecteplase (single weight-adjusted bolus 30–50 mg), alteplase, or reteplase. 1
• For patients ≥75 years old, reduce tenecteplase dose by 50% to minimize stroke risk. 1
• Administer clopidogrel 600 mg loading dose with fibrinolysis—do not use prasugrel or ticagrelor initially. 1, 4
• Provide anticoagulation with enoxaparin (preferred) or unfractionated heparin for at least 48 hours and up to 8 days. 1
• Transfer all fibrinolysed patients to a PCI-capable center for coronary angiography within 3–24 hours (pharmaco-invasive approach). 1, 4
• Perform immediate rescue PCI if ST-segment resolution is <50% at 60–90 minutes or if hemodynamic or electrical instability occurs. 1

Absolute Indications for Primary PCI (Regardless of Time Delay)

Proceed with primary PCI immediately, even if >120 minutes from diagnosis, in the following situations:

• Cardiogenic shock or acute severe heart failure at any time after symptom onset. 2, 1
• Contraindications to fibrinolytic therapy (e.g., active bleeding, recent stroke, recent surgery). 1
• Resuscitated cardiac arrest with ST-elevation on post-resuscitation ECG. 2, 1, 4

In-Hospital Management (First 24 Hours)

• Monitor all STEMI patients for at least 24 hours in a coronary care unit to detect arrhythmias, heart failure, and mechanical complications. 2, 1
• Perform routine echocardiography during hospitalization to assess left and right ventricular function, detect mechanical complications, and exclude left ventricular thrombus. 2, 1, 4
• Initiate high-intensity statin therapy immediately: atorvastatin 80 mg or rosuvastatin 40 mg. 1
• Start oral beta-blockers in patients with heart failure or left ventricular ejection fraction <40%, unless contraindicated by hypotension, acute heart failure, AV block, or severe bradycardia. 2, 1
• Initiate ACE inhibitors within 24 hours in patients with heart failure, left ventricular systolic dysfunction, diabetes, or anterior infarction. 2, 1

Post-Discharge Antiplatelet Therapy

• Continue dual antiplatelet therapy (DAPT) with aspirin 75–100 mg daily plus prasugrel 10 mg daily or ticagrelor 90 mg twice daily for 12 months after PCI. 2, 1, 4
• For patients initially treated with fibrinolysis and clopidogrel, switch to prasugrel or ticagrelor at the time of angiography/PCI. 4
• Reduce prasugrel maintenance dose to 5 mg daily in patients weighing <60 kg due to increased bleeding risk. 5
• Prasugrel is generally not recommended in patients ≥75 years old except in high-risk situations (diabetes or prior MI), and is contraindicated in patients with prior stroke or TIA. 5
• Co-prescribe a proton pump inhibitor in patients at high gastrointestinal bleeding risk (age >65, prior GI bleed, concurrent anticoagulation). 1

Special Clinical Scenarios

Cardiac Arrest with STEMI

• Perform primary PCI immediately in patients with resuscitated cardiac arrest and ST-elevation on post-resuscitation ECG. 2, 1, 4
• Initiate targeted temperature management early in unresponsive patients after cardiac arrest; avoid pre-hospital cooling with large volumes of cold intravenous fluid. 2, 1

Multivessel Disease

• Evaluate severe non-infarct-related artery stenoses before hospital discharge and consider revascularization during the index PCI or in a staged procedure. 1
• In cardiogenic shock, perform non-infarct-related artery PCI during the index procedure. 1

Late Presentation (>12 Hours)

• Routine PCI of an occluded infarct-related artery >48 hours after symptom onset is not indicated in asymptomatic patients. 2, 1
• PCI is warranted in patients with hemodynamic or electrical instability, or persistent symptoms, regardless of time delay. 1

Critical Pitfalls to Avoid

• Never delay reperfusion for serial troponins, echocardiography, or additional testing when the ECG meets STEMI criteria—each 30-minute delay increases mortality. 1, 3
• Never administer routine oxygen when oxygen saturation is ≥90%—this practice worsens outcomes. 2, 1, 4
• 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 at the time of PCI. 4
• Never perform routine thrombus aspiration or deferred stenting during primary PCI—these strategies are contraindicated. 1, 4
• Never postpone PCI to "stabilize" comorbidities (e.g., pneumonia, COPD, active GI bleeding)—the mortality risk from untreated STEMI exceeds that from these conditions. 1, 3