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

Management of ST-Elevation Myocardial Infarction (STEMI)

Primary percutaneous coronary intervention (PCI) within 90-120 minutes of first medical contact is the definitive reperfusion strategy for STEMI, with immediate aspirin and potent P2Y12 inhibitor administration before or at the time of PCI. 1

Immediate Actions at First Medical Contact

• Obtain 12-lead ECG within 10 minutes to confirm ST-segment elevation >0.1 mV in at least two contiguous leads 1, 2
• Administer aspirin 150-325 mg orally or IV immediately (if unable to swallow) as soon as possible for all patients without contraindications 1, 2
• Place on continuous cardiac monitoring with defibrillator capacity as tachycardia and arrhythmias are common 1, 2
• Establish IV access and give morphine 4-8 mg IV for pain control and anxiety reduction, with additional 2 mg doses at 5-15 minute intervals as needed 2, 3
• Avoid routine oxygen administration unless SaO2 <90% (Class III recommendation) 1, 3

Reperfusion Strategy Decision (Time Zero = STEMI Diagnosis)

The critical decision point is whether primary PCI can be performed within 120 minutes of STEMI diagnosis:

Primary PCI Strategy (Preferred)

• Perform primary PCI within 90-120 minutes of first medical contact if a PCI-capable facility is accessible 1
• In patients <75 years with large anterior infarction presenting within 2 hours of symptom onset, the time window narrows to 90 minutes 4
• Transfer patients directly to the catheterization laboratory, bypassing the emergency department to minimize door-to-balloon time 1, 2

Fibrinolytic Strategy (When PCI Not Timely)

• If primary PCI cannot be performed within 120 minutes, initiate fibrinolytic therapy immediately within 10 minutes of STEMI diagnosis, preferably in the pre-hospital setting 1
• Use a fibrin-specific agent: tenecteplase, alteplase, or reteplase 1
• All patients receiving fibrinolysis must be transferred to a PCI-capable center immediately after fibrinolysis for angiography between 2-24 hours post-lysis 1, 3

Antithrombotic Regimen

For Primary PCI

• Administer a potent P2Y12 inhibitor (prasugrel 60 mg or ticagrelor) before or at the time of PCI, or clopidogrel 600 mg if these are unavailable or contraindicated 1, 2
• Prasugrel is preferred over clopidogrel due to faster onset and superior effectiveness in reducing nonfatal MI (9.0% to 6.8%) and stent thrombosis (2.8% to 1.6%) 4
• Give unfractionated heparin as weight-adjusted IV bolus followed by infusion (enoxaparin or bivalirudin are alternatives) 1, 2, 3
• Do not delay for laboratory results or cardiac biomarkers—treat based on clinical presentation and ECG 2

Critical caveat: In patients <60 kg body weight, consider lowering prasugrel maintenance dose to 5 mg daily due to increased bleeding risk 5

For Fibrinolytic Strategy

• Clopidogrel 300 mg loading dose is indicated in addition to aspirin 1
• Anticoagulation with enoxaparin IV followed by subcutaneous (preferred over UFH) or UFH as weight-adjusted bolus/infusion until revascularization or up to 8 days 1

Important contraindication: Prasugrel is contraindicated in patients with prior TIA or stroke due to increased ICH risk (4.2% thrombotic stroke + 2.3% ICH vs 1.2% with clopidogrel) 5

Post-Reperfusion Management

Immediate Post-PCI Care

• Continue cardiac monitoring for at least 24-48 hours, as 92% of sustained ventricular arrhythmias occur within this timeframe 2
• Perform rescue PCI immediately if fibrinolysis fails (<50% ST-segment resolution at 60-90 minutes) or with hemodynamic/electrical instability 1
• Emergency angiography and PCI immediately if heart failure or cardiogenic shock develops 1, 3

Routine Imaging and Monitoring

• Perform echocardiography during hospital stay to assess LV/RV function, detect mechanical complications, and exclude LV thrombus 1

Long-Term Medical Therapy (Initiate Within 24 Hours)

Dual Antiplatelet Therapy (DAPT)

• Continue DAPT for 12 months with aspirin 75-100 mg plus prasugrel 10 mg or ticagrelor (or clopidogrel if unavailable/contraindicated) unless excessive bleeding risk 1, 2, 3
• Add a proton pump inhibitor (PPI) in combination with DAPT for patients at high gastrointestinal bleeding risk 1, 3

Additional Therapies

• Initiate oral beta-blocker within 24 hours in patients with heart failure and/or LVEF <40%, unless contraindicated 1
• Start ACE inhibitor within the first 24 hours in appropriate patients 1
• Begin high-intensity statin therapy immediately with LDL-C goal <1.8 mmol/L (70 mg/dL) or ≥50% reduction 1

Critical pitfall to avoid: IV beta-blockers are contraindicated in acute STEMI with hypotension, acute heart failure, AV block, or severe bradycardia (Class III recommendation) 1, 2

Special Considerations

Timing of P2Y12 Inhibitor Loading

• In UA/NSTEMI patients, prasugrel loading should not be administered until coronary anatomy is established to avoid bleeding risk in patients requiring urgent CABG 5
• In STEMI patients presenting within 12 hours, prasugrel can be given at diagnosis, though most receive it at time of PCI 5

Late Presenters (>12 Hours)

• Routine PCI of an occluded infarct-related artery >48 hours after STEMI onset is not indicated in asymptomatic patients (Class III recommendation) 1

Medications to Avoid

• Do not use NSAIDs for pain relief due to increased mortality, reinfarction, and myocardial rupture risk 2
• Fondaparinux is not recommended for primary PCI 1

Secondary Prevention

• Enroll all patients in cardiac rehabilitation programs 1
• Provide smoking cessation counseling with pharmacotherapy (nicotine replacement, varenicline, or bupropion) 1