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

STEMI Treatment

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

Reperfusion Strategy Selection

The choice between primary PCI and fibrinolysis depends critically on time to treatment:

• Primary PCI is preferred when it can be performed within 120 minutes of STEMI diagnosis by an experienced team 1, 2, 3
• Fibrinolytic therapy should be initiated immediately if anticipated time to PCI exceeds 120 minutes, particularly in the pre-hospital setting 4, 2, 3
• Patients should bypass the emergency department and go directly to the catheterization laboratory when primary PCI is the chosen strategy 2

Time-Dependent Treatment Windows

• Within 12 hours of symptom onset: Reperfusion therapy (PCI or fibrinolysis) is strongly indicated 1, 3
• 12-24 hours after symptom onset: Primary PCI is reasonable if evidence of ongoing ischemia exists 1, 3
• Beyond 24 hours: Routine PCI of a totally occluded artery is not recommended in stable patients without ongoing ischemia 3
• Cardiogenic shock or severe heart failure: Emergency PCI is indicated regardless of time delay from MI onset 1, 3

Primary PCI Protocol

Immediate Antiplatelet Therapy

Aspirin must be administered as soon as possible:

• Oral: 162-325 mg (or 150-325 mg per European guidelines) 1, 2
• Intravenous: 250-500 mg if unable to swallow 2
• Continue aspirin indefinitely after PCI; 81 mg daily is the preferred maintenance dose 1

P2Y12 inhibitor loading dose before or at time of PCI:

• Ticagrelor: 180 mg (preferred, with 81 mg aspirin maintenance) 1
• Prasugrel: 60 mg (avoid if prior stroke/TIA) 1
• Clopidogrel: 600 mg (if prasugrel/ticagrelor unavailable) 1

Anticoagulation During PCI

Unfractionated heparin (UFH) is the standard:

• 70-100 U/kg IV bolus if no GP IIb/IIIa inhibitor planned (target ACT 250-300 seconds HemoTec or 300-350 seconds Hemochron) 1
• 50-70 U/kg IV bolus if GP IIb/IIIa inhibitor planned (target ACT 200-250 seconds) 1

Bivalirudin alternative:

• 0.75 mg/kg IV bolus, then 1.75 mg/kg/h infusion 1
• Preferred over UFH with GP IIb/IIIa inhibitor in high bleeding risk patients 1
• Reduce infusion to 1 mg/kg/h if creatinine clearance <30 mL/min 1

Fondaparinux is contraindicated as sole anticoagulant for primary PCI 1

Stent Selection and Adjunctive Therapy

• Drug-eluting stents (DES) or bare-metal stents (BMS) are both acceptable 1
• Use BMS in patients with high bleeding risk, inability to comply with 1 year of dual antiplatelet therapy (DAPT), or anticipated surgery within 1 year 1
• GP IIb/IIIa inhibitors (abciximab, high-dose tirofiban, or double-bolus eptifibatide) may be reasonable in selected patients receiving UFH 1
• Do NOT perform PCI of non-infarct arteries at time of primary PCI in hemodynamically stable patients 1

Fibrinolytic Therapy Protocol

When primary PCI cannot be performed within 120 minutes, fibrinolysis should be initiated immediately:

Fibrinolytic Agent Selection

Tenecteplase is the preferred fibrin-specific agent due to single-bolus administration 4, 2:

• Weight-adjusted dosing: 30 mg (<60 kg), 35 mg (60-69 kg), 40 mg (70-79 kg), 45 mg (80-89 kg), 50 mg (≥90 kg) 4, 5
• 50% dose reduction for patients ≥75 years to reduce stroke risk 4
• Alternative agents: alteplase or reteplase 4, 2

Adjunctive Therapy with Fibrinolysis

Antiplatelet therapy:

• Aspirin: 150-325 mg oral or IV 4, 2
• Clopidogrel: 300 mg loading dose (if ≤24 hours after fibrinolysis) or 600 mg (if >24 hours after fibrinolysis) 1
• Continue clopidogrel 75 mg daily without additional loading if already received with fibrinolytic 1

Anticoagulation (continue until revascularization or up to 8 days):

• Enoxaparin IV followed by subcutaneous (preferred over UFH) 4, 2
• UFH: weight-adjusted IV bolus followed by infusion 4, 2

Post-Fibrinolytic Management

All patients require transfer to PCI-capable center immediately after fibrinolysis 4

Assess reperfusion success at 60-90 minutes:

• Rescue PCI indicated immediately if <50% ST-segment resolution or hemodynamic/electrical instability 4
• Routine angiography and PCI of infarct artery recommended 2-24 hours after successful fibrinolysis 4

Critical Contraindications to Fibrinolysis

Tenecteplase is absolutely contraindicated in patients with 5:

• Active internal bleeding
• History of cerebrovascular accident
• Intracranial/intraspinal surgery or trauma within 2 months
• Intracranial neoplasm, arteriovenous malformation, or aneurysm
• Known bleeding diathesis
• Severe uncontrolled hypertension

Long-Term Antiplatelet Therapy

DAPT duration after stenting:

• Continue for 12 months with aspirin plus P2Y12 inhibitor (ticagrelor 90 mg twice daily or prasugrel 10 mg daily preferred over clopidogrel 75 mg daily) 1, 2
• Minimum 30 days for BMS, up to 1 year 1
• Aspirin 75-100 mg daily indefinitely after DAPT period 2

Additional In-Hospital Management

High-intensity statin therapy should be initiated as early as possible 1, 2

Beta-blockers should be started orally in patients with heart failure or LVEF <40% unless contraindicated 2

ACE inhibitors should be started within 24 hours in patients with heart failure, LV dysfunction, diabetes, or anterior infarct 2

Anticoagulation for specific indications:

• Vitamin K antagonist for atrial fibrillation with CHADS2 score ≥2, mechanical valves, venous thromboembolism, or hypercoagulable disorder 1
• Minimize duration of triple therapy (warfarin + aspirin + P2Y12 inhibitor) to reduce bleeding risk 1

Special Populations and Situations

Cardiogenic shock: Emergency revascularization with PCI or CABG is indicated regardless of time delay; if unsuitable for either, fibrinolytic therapy should be administered 1

Out-of-hospital cardiac arrest with STEMI on ECG: Immediate angiography and PCI when indicated 1

Prior stroke/TIA: Prasugrel is contraindicated 1

Common Pitfalls

• Do not combine planned fibrinolysis with immediate PCI - choose one primary reperfusion strategy, as combination therapy increases mortality, heart failure, and recurrent ischemia 5
• Do not use high-dose IV aspirin (>250 mg) as it may increase in-hospital mortality compared to standard dosing 6
• Do not delay reperfusion - every hour of delay significantly reduces myocardial salvage and increases mortality 3
• Do not perform multivessel PCI at time of primary PCI in stable patients without cardiogenic shock 1