STEMI Management: Diagnostics and Treatment

Initial Diagnosis and Assessment

The American Academy of Family Physicians recommends STEMI diagnosis by >0.1 mV ST-segment elevation in two contiguous leads, new left bundle branch block, or true posterior MI on ECG 1
Obtain 12-lead ECG immediately upon first medical contact—do not delay reperfusion therapy except when alternate diagnoses like aortic dissection or pericarditis are suspected 1
Laboratory studies include troponin I, creatine kinase, complete blood count, INR, aPTT, electrolytes, magnesium, BUN, creatinine, glucose, and lipid panel 1
Chest radiography is recommended but must not delay reperfusion 1

Aspirin 162-325 mg oral (or 250-500 mg IV if unable to swallow) should be administered immediately—patient should chew the tablet 1, 2
P2Y12 inhibitor loading dose before or at time of PCI: ticagrelor 180 mg, prasugrel 60 mg, or clopidogrel 600 mg 2
Morphine sulfate 2-4 mg IV, with 2-8 mg IV every 5-15 minutes as needed for pain 1
Nitroglycerin 0.4 mg sublingual every 5 minutes (up to three doses), but avoid in hypotension, bradycardia, right-sided ischemia, or phosphodiesterase inhibitor use within 24 hours (48 hours for tadalafil) 1
Oxygen supplementation to maintain arterial saturation >90% if pulmonary congestion present 3

Primary PCI is the definitive treatment when performed by an experienced team within 120 minutes of STEMI diagnosis; if this timeframe cannot be met, immediate fibrinolytic therapy should be administered 2
Skilled PCI facility accessible (operators >75 primary PCI cases/year, team >36 cases/year) within 90-120 minutes of first medical contact 1, 2
Diagnosis of STEMI is uncertain 1
High-risk features present: cardiogenic shock, Killip class III or greater 1
Contraindications to fibrinolysis exist, including increased bleeding risk 1
Late presentation (>3 hours from symptom onset) 1
Failed fibrinolysis requiring rescue PCI 1
Early presentation (<3 hours from symptom onset) and PCI not readily available 1
Anticipated time to PCI exceeds 120 minutes, particularly in pre-hospital setting 2, 4
Invasive strategy not an option (catheterization unavailable, vascular access difficulties, skilled PCI facility not accessible) 1

Unfractionated heparin (UFH) 70-100 U/kg IV bolus if no GP IIb/IIIa inhibitor planned 2
Bivalirudin 0.75 mg/kg IV bolus and 1.75 mg/kg/h infusion as alternative to UFH 2
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 1 year DAPT, or anticipated surgery within 1 year 2

Absolute contraindications to fibrinolysis include prior intracranial hemorrhage, known structural cerebral vascular lesion, known malignant intracranial neoplasm, ischemic stroke within 3 months, suspected aortic dissection, active bleeding or bleeding diathesis, and significant closed-head or facial trauma within 3 months 5
Tenecteplase is the preferred fibrin-specific agent due to single-bolus administration 2, 4
Weight-adjusted tenecteplase dosing: 30 mg for weight <60 kg, 35 mg for 60-69 kg, 40 mg for 70-79 kg, 45 mg for 80-89 kg, 50 mg for ≥90 kg 4
For patients ≥75 years old, reduce dose by 50% to minimize stroke risk 4
Aspirin 162-325 mg oral or IV immediately 5, 4
Clopidogrel loading dose: 300 mg for age ≤75 years, 75 mg (no loading dose) for age >75 years 5
Anticoagulation for minimum 48 hours, preferably for duration of hospitalization up to 8 days 5
Enoxaparin preferred: Age <75 years: 30 mg IV bolus, then 1 mg/kg subcutaneous every 12 hours (max 100 mg first 2 doses); Age ≥75 years: no bolus, 0.75 mg/kg subcutaneous every 12 hours (max 75 mg first 2 doses) 5
UFH alternative: 60 U/kg IV bolus (max 4000 U), then 12 U/kg/h infusion (max 1000 U), adjusted to aPTT 1.5-2.0 times control 5

Transfer to PCI-capable center immediately after fibrinolysis is indicated in all patients 4
Rescue PCI immediately when fibrinolysis has failed (<50% ST-segment resolution at 60-90 minutes) or hemodynamic/electrical instability present 1, 4
Routine angiography and PCI of infarct-related artery between 2-24 hours after successful fibrinolysis 4

Dual antiplatelet therapy (DAPT) duration: minimum 12 months for drug-eluting stents and 30 days for bare-metal stents 2
Aspirin 75-100 mg daily indefinitely after DAPT period 2
Continue P2Y12 inhibitor (clopidogrel 75 mg, ticagrelor 90 mg twice daily, or prasugrel 10 mg daily) for specified duration 5, 2

High-intensity statin therapy initiated as early as possible 2
Beta-blockers started orally in patients with heart failure or LVEF <40% unless contraindicated 2
ACE inhibitors within 24 hours in patients with heart failure, LV dysfunction, diabetes, or anterior infarct 2
Avoid beta-blockers or calcium channel blockers acutely in patients with frank cardiac failure evidenced by pulmonary congestion or low-output state 3

Emergency revascularization with PCI or CABG is recommended in cardiogenic shock regardless of time delay 2
Intra-aortic balloon counterpuls