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

Immediate Management of ST-Segment Elevation Myocardial Infarction (STEMI)

First 10 Minutes: Diagnosis and Initial Actions

Obtain and interpret a 12-lead ECG within 10 minutes of first medical contact to confirm ST-segment elevation or STEMI-equivalent patterns (new left bundle branch block, hyperacute T-waves, isolated anterior ST-depression with aVR elevation, or diffuse ST-depression with aVR elevation). 1, 2, 3

• Initiate continuous ECG monitoring with defibrillator capability immediately, as ventricular fibrillation is the most common early lethal arrhythmia. 1, 3

• Administer aspirin 150–325 mg orally (chewable or soluble) or 250–500 mg intravenously if the patient cannot swallow—give this immediately at first medical contact. 1, 2, 3

• Avoid routine supplemental oxygen unless arterial oxygen saturation is below 90%; routine oxygen in non-hypoxemic patients worsens myocardial injury. 1, 2, 3

• Activate the catheterization laboratory immediately upon STEMI diagnosis—do not wait for troponin results, echocardiography, or other imaging. 3

Reperfusion Strategy Selection: The 120-Minute Rule

Primary percutaneous coronary intervention (PCI) is the preferred reperfusion strategy when it can be performed within 120 minutes of STEMI diagnosis. 1, 2, 3

When Primary PCI Is Achievable (≤120 minutes)

• Transfer the patient directly to the catheterization laboratory, bypassing the emergency department and intensive care unit entirely. 1, 2, 3

• Target a door-to-balloon time ≤90 minutes (≤60 minutes if the patient presents within 120 minutes of symptom onset or arrives at a PCI-capable center). 4

• 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 and ticagrelor are unavailable or contraindicated. 1, 2, 3

• 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. 1, 2, 3

• Fondaparinux is absolutely contraindicated for primary PCI. 1, 2

• Perform PCI via radial artery access to minimize bleeding complications. 2, 3

• Implant drug-eluting stents as the standard device. 2, 3

• Routine thrombus aspiration and deferred stenting are contraindicated—they worsen outcomes. 2, 3

When Primary PCI Cannot Be Achieved (>120 minutes)

If the anticipated first-medical-contact-to-device time exceeds 120 minutes, initiate fibrinolytic therapy within 10 minutes of STEMI diagnosis, preferably in the pre-hospital setting. 1, 2, 4, 3

• Use a fibrin-specific agent: tenecteplase, alteplase, or reteplase administered according to weight-based dosing. 1, 2, 4, 3

• For patients ≥75 years old, reduce the tenecteplase dose by 50% to lower stroke risk. 2, 3

• Give clopidogrel 600 mg loading dose with fibrinolysis; do not use prasugrel or ticagrelor as the initial P2Y12 inhibitor with fibrinolytic therapy. 2, 4, 3

• Provide enoxaparin IV bolus followed by subcutaneous dosing (preferred over unfractionated heparin) for at least 48 hours and up to 8 days after fibrinolysis. 1, 2, 4, 3

• Transfer all fibrinolyzed patients to a PCI-capable center immediately for coronary angiography within 3–24 hours (pharmaco-invasive strategy). 1, 2, 4, 3

• Perform immediate rescue PCI if ST-segment resolution is <50% at 60–90 minutes or if hemodynamic/electrical instability or worsening ischemia occurs at any time. 1, 2, 4, 3

• Switch from clopidogrel to prasugrel or ticagrelor at the time of angiography/PCI after fibrinolysis. 4, 3

Absolute Indications for Immediate Primary PCI (Regardless of Time Delay)

Proceed directly to primary PCI irrespective of anticipated delays in the following scenarios:

• Cardiogenic shock or acute severe heart failure at any time after symptom onset. 1, 2, 3

• Contraindications to fibrinolytic therapy (active bleeding, recent stroke, recent major surgery, terminal illness). 2, 3

• Resuscitated cardiac arrest with ST-elevation on post-resuscitation ECG. 1, 2, 3

• Initiate targeted temperature management early in unresponsive post-cardiac-arrest patients; avoid pre-hospital cooling with large volumes of cold IV fluid. 1, 2

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. 1, 4, 3

• Perform routine transthoracic echocardiography during admission to assess left and right ventricular function, detect mechanical complications, and exclude left ventricular thrombus. 1, 4, 3

• Initiate high-intensity statin therapy immediately (atorvastatin 80 mg or rosuvastatin 40 mg). 2, 3

• 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, 3

• Begin ACE inhibitors within 24 hours in patients with heart failure, left ventricular systolic dysfunction, diabetes, or anterior infarction. 2, 4, 3

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. 1, 2, 4, 3

• Co-prescribe a proton pump inhibitor in patients at high gastrointestinal bleeding risk (age >65, prior GI bleed, concurrent anticoagulation). 2, 4, 3

Special Clinical Scenarios

Late Presentation (>12 hours)

• Routine PCI of an occluded infarct-related artery >48 hours after symptom onset is not indicated in asymptomatic patients. 1, 2, 3

• PCI is warranted in patients with hemodynamic or electrical instability, or persistent symptoms, regardless of time delay. 2, 3

Multivessel Disease

• Evaluate severe non-infarct-related artery stenoses before discharge and consider revascularization during the index PCI or as a staged procedure. 2, 3

• In cardiogenic shock, perform non-infarct-related artery PCI during the index procedure. 2, 3

MINOCA (Myocardial Infarction with Non-Obstructive Coronary Arteries)

• A substantial proportion of STEMI patients have no significant coronary stenosis on urgent angiography; perform additional diagnostic testing to identify the underlying cause and tailor therapy accordingly. 1, 2

Critical Pitfalls to Avoid

• Do not delay reperfusion for serial troponins, echocardiography, or additional testing when the ECG meets STEMI criteria; each 30-minute delay increases mortality. 3

• Do not administer routine oxygen when SpO₂ ≥90%; this worsens outcomes. 1, 2, 3

• Do not use prasugrel or ticagrelor as the initial P2Y12 inhibitor with fibrinolytic therapy; clopidogrel is required initially, with transition at the time of PCI. 2, 4, 3

• Do not perform routine thrombus aspiration or deferred stenting during primary PCI; these strategies are contraindicated. 2, 3

• Do not postpone PCI to "stabilize" comorbidities (pneumonia, COPD, active GI bleeding); the mortality risk from untreated STEMI exceeds that from the comorbid condition. 2, 3

• Do not miss the 3–24 hour window for routine angiography after successful fibrinolysis. 4

• Patients on oral anticoagulants, with renal insufficiency, or who are elderly require careful dose adjustments of antithrombotic therapies. 1, 2