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

Treatment of ST-Elevation Myocardial Infarction (STEMI)

Primary percutaneous coronary intervention (PCI) is the definitive treatment for STEMI when performed by an experienced team within 120 minutes of first medical contact; if this timeframe cannot be met, immediate fibrinolytic therapy should be administered instead. 1, 2

Immediate Assessment and Reperfusion Strategy Selection

Initial Diagnostic Steps

• Obtain a 12-lead ECG within 10 minutes of first medical contact with continuous monitoring and defibrillator availability 3
• Calculate the anticipated time from first medical contact to PCI capability 1

Reperfusion Decision Algorithm

• If PCI can be performed within 120 minutes: Transfer directly to the catheterization laboratory, bypassing the emergency department for primary PCI 1, 3, 2
• If PCI cannot be performed within 120 minutes: Initiate fibrinolytic therapy immediately, preferably in the pre-hospital setting 1, 2
• If symptoms began 12-24 hours ago with ongoing ischemia: Fibrinolysis is reasonable if large myocardium at risk or hemodynamic instability present 1

Primary PCI Protocol

Immediate Antiplatelet Therapy (Before or During PCI)

• Aspirin: 162-325 mg oral (chewable preferred) or 250-500 mg IV if unable to swallow 1, 3, 2

  • The 162 mg dose may be as effective and safer than 325 mg based on fibrinolytic trial data 4
  • Continue 75-100 mg daily indefinitely after the acute phase 1, 2

• P2Y12 Inhibitor Loading Dose (choose one): 1, 2

  • Ticagrelor 180 mg (preferred option, maintenance 90 mg twice daily)
  • Prasugrel 60 mg (maintenance 10 mg daily) - contraindicated if prior stroke/TIA 5
  • Clopidogrel 600 mg (maintenance 75 mg daily) - use if ticagrelor/prasugrel unavailable 6

Anticoagulation During PCI

• Unfractionated heparin (UFH): 1, 2

  • 70-100 U/kg IV bolus if no GP IIb/IIIa inhibitor planned (target ACT 250-300 seconds HemoTec or 300-350 seconds Hemochron)
  • 50-70 U/kg IV bolus if GP IIb/IIIa inhibitor planned (target ACT 200-250 seconds)

• Bivalirudin (alternative to UFH): 0.75 mg/kg IV bolus followed by 1.75 mg/kg/h infusion, preferred in high bleeding risk patients 1

  • Reduce infusion to 1 mg/kg/h if creatinine clearance <30 mL/min 1

• Fondaparinux: Do not use as sole anticoagulant for primary PCI (Class III: Harm) 1

Stent Selection

• Drug-eluting stents (DES) or bare-metal stents (BMS) are both acceptable 2
• Use BMS in patients with high bleeding risk, inability to comply with 12 months dual antiplatelet therapy, or anticipated surgery within 1 year 2

Fibrinolytic Therapy Protocol

Contraindications Assessment

Absolute contraindications (do not give fibrinolytics): 1

• Any prior intracranial hemorrhage
• Known structural cerebrovascular lesion or intracranial neoplasm
• Ischemic stroke within 3 months (except acute ischemic stroke within 4.5 hours)
• Suspected aortic dissection
• Active bleeding or bleeding diathesis
• Significant closed-head/facial trauma within 3 months
• Intracranial/intraspinal surgery within 2 months
• Severe uncontrolled hypertension unresponsive to emergency therapy

Fibrinolytic Agent Selection

• Tenecteplase (preferred): Single weight-adjusted IV bolus 2
  • 50% dose reduction for patients ≥75 years to reduce stroke risk 2
• Alternative agents include alteplase or reteplase if tenecteplase unavailable 1

Adjunctive Antiplatelet Therapy with Fibrinolysis

• Aspirin: 162-325 mg loading dose, then 81-325 mg daily (81 mg preferred for maintenance) 1, 7

• Clopidogrel: 1, 7

  • Age ≤75 years: 300 mg loading dose, then 75 mg daily
  • Age >75 years: No loading dose, give 75 mg daily
  • Continue for minimum 14 days and up to 1 year 1

Adjunctive Anticoagulation with Fibrinolysis (choose one)

First-line: Enoxaparin 1, 7

• Age <75 years: 30 mg IV bolus, then 1 mg/kg subcutaneous every 12 hours (maximum 100 mg for first 2 doses)
• Age ≥75 years: No bolus, 0.75 mg/kg subcutaneous every 12 hours (maximum 75 mg for first 2 doses)
• Creatinine clearance <30 mL/min: 1 mg/kg subcutaneous every 24 hours
• Duration: Until revascularization or up to 8 days of hospitalization

Second-line: Unfractionated heparin 1, 7

• 60 U/kg IV bolus (maximum 4000 U), then 12 U/kg/h infusion (maximum 1000 U/h initially)
• Adjust to maintain aPTT 1.5-2.0 times control (50-70 seconds)
• Duration: 48 hours or until revascularization

Third-line: Fondaparinux 1, 7

• 2.5 mg IV initial dose, then 2.5 mg subcutaneous daily
• Only if creatinine clearance >30 mL/min
• Duration: Until revascularization or up to 8 days

Post-Fibrinolysis Management

• Transfer immediately to PCI-capable center 7, 2
• Perform angiography with possible PCI: 7, 2
  • Immediately if fibrinolysis failed (persistent chest pain, <50% ST-segment resolution at 60-90 minutes)
  • Between 2-24 hours after successful fibrinolysis

Long-Term Dual Antiplatelet Therapy (DAPT)

Duration After Stenting

• Drug-eluting stents: Minimum 12 months of DAPT (aspirin + P2Y12 inhibitor) 1, 2
• Bare-metal stents: Minimum 30 days of DAPT, ideally up to 12 months unless high bleeding risk 1, 2
• After DAPT period, continue aspirin 75-100 mg daily indefinitely 1, 2

Duration After Fibrinolysis Without Stenting

• Continue DAPT for minimum 14 days, reasonable to extend up to 1 year 1, 2

Additional In-Hospital Management

Medications to Initiate

• High-intensity statin: Start immediately (target LDL-C <70 mg/dL or ≥50% reduction) 3, 2
• Beta-blockers: Start orally in patients with heart failure or LVEF <40% unless contraindicated 2
• ACE inhibitors: Start within 24 hours in patients with heart failure, LV dysfunction, diabetes, or anterior infarct 1, 2

Diagnostic Testing

• Perform echocardiography during hospitalization to assess LV/RV function, detect mechanical complications, and exclude LV thrombus 3

Special Populations and Critical Situations

Cardiogenic Shock

• Emergency revascularization with PCI or CABG regardless of time delay 2
• If unsuitable for either, administer fibrinolytic therapy 2

Out-of-Hospital Cardiac Arrest with STEMI on ECG

• Proceed immediately to angiography and PCI when indicated 2

Patients Requiring Warfarin (Atrial Fibrillation, LV Thrombus)

• Target INR 2.0-2.5 when combining with aspirin 75-81 mg and clopidogrel 75 mg 1, 7
• Monitor closely for increased bleeding risk with triple therapy 1, 7

Low Body Weight (<60 kg)

• Consider reducing prasugrel maintenance dose to 5 mg daily due to increased bleeding risk 5

Elderly (≥75 Years)

• Prasugrel generally not recommended due to increased fatal and intracranial bleeding risk, except in high-risk situations (diabetes or prior MI) 5
• No clopidogrel loading dose if receiving fibrinolytic therapy 1

Critical Pitfalls to Avoid

• Never delay primary PCI to obtain additional imaging or consultations - the 120-minute window is absolute 1, 3, 2
• Do not use fondaparinux as sole anticoagulant during primary PCI - associated with catheter thrombosis 1
• Avoid prasugrel in patients with prior stroke or TIA - contraindicated due to increased stroke risk 2, 5
• Do not discontinue DAPT prematurely - increases risk of stent thrombosis and recurrent cardiovascular events, particularly in first few weeks 5
• Discontinue prasugrel at least 7 days before elective surgery when possible 5
• Do not give fibrinolytics to patients with ST depression alone unless true posterior MI suspected or ST elevation in aVR present 1