What is the management of ST-Elevation Myocardial Infarction (STEMI)?

Management of ST-Elevation Myocardial Infarction (STEMI)

Immediate Actions Upon First Medical Contact

Administer 162-325 mg of non-enteric coated aspirin (chewed) immediately to all STEMI patients without contraindications 1, 2. This should occur at first medical contact, not delayed until hospital arrival.

• Obtain a 12-lead ECG within 10 minutes of first medical contact or emergency department arrival 1, 2
• STEMI is defined as ST-segment elevation >0.1 mV in at least two contiguous precordial or adjacent limb leads, new left bundle branch block, or true posterior MI 2
• If initial ECG is non-diagnostic but suspicion remains high, repeat ECGs at 5-10 minute intervals 2
• Initiate continuous ECG monitoring with defibrillator capacity 3
• Avoid routine oxygen therapy unless oxygen saturation is <90% 3

Reperfusion Strategy: The Critical Time-Based Decision

Primary PCI is the preferred reperfusion strategy if first medical contact-to-device time can be achieved within 90-120 minutes 1, 2. This is the single most important decision point in STEMI management.

When to Choose Primary PCI:

• First medical contact-to-device time ≤90 minutes at PCI-capable centers 3
• First medical contact-to-device time ≤120 minutes with transfer 1, 2
• Patients should bypass the emergency department and go directly to the catheterization laboratory 1
• Use radial access and drug-eluting stents as standard of care 3

When to Choose Fibrinolytic Therapy:

If primary PCI cannot be performed within 120 minutes of STEMI diagnosis, initiate fibrinolytic therapy immediately, preferably in the pre-hospital setting 1, 2.

• Fibrinolysis is indicated for patients with symptoms <12 hours duration and persistent ST-segment elevation 1
• Use fibrin-specific agents: tenecteplase, alteplase, or reteplase 1
• For patients 12-24 hours after symptom onset with ongoing ischemia, large area of myocardium at risk, or hemodynamic instability, fibrinolysis is reasonable 1

Critical contraindications to fibrinolysis:

• Active pathological bleeding 1
• History of transient ischemic attack or stroke 1, 4
• ST depression (except true posterior MI or ST elevation in aVR) 1

Antithrombotic Therapy for Primary PCI

Administer dual antiplatelet therapy with aspirin plus a potent P2Y12 inhibitor before or at the time of PCI 1, 2, 3.

P2Y12 Inhibitor Selection:

• Prasugrel 60 mg loading dose or ticagrelor are strongly preferred over clopidogrel 1, 2, 3
• Prasugrel is contraindicated in patients with prior TIA/stroke 4
• For patients ≥75 years old, prasugrel is generally not recommended except in high-risk situations (diabetes or prior MI) 4
• Consider prasugrel 5 mg maintenance dose (instead of 10 mg) for patients <60 kg due to increased bleeding risk 4
• Clopidogrel is acceptable if prasugrel or ticagrelor are unavailable or contraindicated 1, 2

Anticoagulation:

• Unfractionated heparin IV bolus at 100 U/kg (60 U/kg if glycoprotein IIb/IIIa inhibitors are used) 3
• Fondaparinux is not recommended for primary PCI 1

Antithrombotic Therapy for Fibrinolytic Strategy

For patients receiving fibrinolysis, administer aspirin plus clopidogrel with anticoagulation 1, 2.

Antiplatelet Therapy:

• Aspirin 162-325 mg loading dose, then 81-325 mg daily (81 mg preferred for maintenance) 1
• Clopidogrel 300 mg loading dose for patients <75 years; 75 mg loading dose for patients ≥75 years 1
• Continue clopidogrel 75 mg daily for at least 14 days, up to 1 year 1

Anticoagulation (choose one):

• Enoxaparin (preferred over UFH): IV bolus followed by subcutaneous injection for duration of hospitalization up to 8 days or until revascularization 1
• UFH: weight-adjusted IV bolus and infusion to achieve aPTT 1.5-2.0 times control for 48 hours or until revascularization 1
• Fondaparinux: initial IV dose, then daily subcutaneous injections if creatinine clearance >30 mL/min, for up to 8 days or until revascularization 1

Post-Fibrinolysis Management: The Pharmaco-Invasive Approach

All patients receiving fibrinolysis must be transferred to a PCI-capable center immediately after fibrinolysis 1.

Timing of Angiography After Fibrinolysis:

• Immediate emergency angiography and PCI for cardiogenic shock or heart failure 1
• Rescue PCI immediately if fibrinolysis fails (<50% ST-segment resolution at 60-90 minutes) or hemodynamic/electrical instability develops 1
• Routine angiography 2-24 hours after successful fibrinolysis 1, 5
• Emergency angiography for recurrent ischemia or evidence of reocclusion 1

Management of Cardiogenic Shock

Emergency revascularization (PCI or CABG) is recommended regardless of time delay from MI onset for patients with cardiogenic shock 1, 2, 3.

• Immediate transfer to PCI-capable hospital for patients developing cardiogenic shock or acute severe heart failure 1
• CABG is indicated for patients <75 years with shock within 36 hours of STEMI who have severe multivessel or left main disease, if revascularization can be performed within 18 hours of shock 3
• Intra-aortic balloon counterpulsation for patients not quickly stabilized with pharmacological therapy 2

Long-Term Medical Management Post-STEMI

Continue dual antiplatelet therapy for 12 months after PCI unless contraindications exist 1, 3.

Maintenance Antiplatelet Therapy:

• Aspirin 75-100 mg daily indefinitely 1, 3
• P2Y12 inhibitor (ticagrelor, prasugrel, or clopidogrel) for 12 months 1, 3

Additional Medical Therapy:

• Initiate ACE inhibitors within 24 hours in all patients, particularly those with anterior MI, heart failure, or ejection fraction ≤0.40 2
• Continue oral beta-blockers indefinitely in all eligible patients, especially those with heart failure or LVEF <40% 2, 3
• High-intensity statin therapy as early as possible 3

Surgical Considerations

If CABG is required, discontinue prasugrel at least 7 days prior to surgery when possible 4.

• Do not start prasugrel in patients likely to undergo urgent CABG 4
• The risk of CABG-related bleeding is substantial in patients recently treated with antiplatelet agents 1

Post-Discharge Assessment and Follow-Up

Routine echocardiography during hospital stay is recommended to assess LV and RV function, detect mechanical complications, and exclude LV thrombus 1, 2.

• Follow-up ECGs at 24 hours and hospital discharge to assess reperfusion success and infarct extent 2
• Participation in cardiac rehabilitation program is strongly recommended 1
• Identify smokers and provide repeated cessation advice with pharmacotherapy support 1

Critical Pitfalls to Avoid

Never delay reperfusion therapy beyond guideline-recommended time windows 1, 2. The effectiveness of all treatments declines rapidly with time, and patient outcomes worsen 6.

• Do not miss STEMI equivalents: hyperacute T-waves, true posterior MI (ST depression in V1-V4), or multilead ST depression with ST elevation in aVR suggesting left main disease 3
• Atypical presentations are common in women, elderly, and diabetic patients who may present without chest pain 3
• Do not discontinue antiplatelet therapy prematurely, particularly in the first few weeks after ACS, as this increases the risk of stent thrombosis, MI, and death 4
• Suspect bleeding in any hypotensive patient who has recently undergone coronary angiography, PCI, CABG, or other surgical procedures while on prasugrel 4
• If possible, manage bleeding without discontinuing antiplatelet therapy 4