What is the initial evaluation and treatment for acute ST-Elevation Myocardial Infarction (STEMI)?

Initial Evaluation and Treatment for Acute ST-Elevation Myocardial Infarction (STEMI)

The most effective management of acute STEMI requires immediate diagnosis with 12-lead ECG within 10 minutes of first medical contact, followed by primary percutaneous coronary intervention (PCI) within 120 minutes of diagnosis when feasible, or fibrinolytic therapy when timely PCI is not available.

Initial Diagnosis and Assessment

• A 12-lead ECG recording and interpretation should be obtained as soon as possible at first medical contact, with a maximum target delay of 10 minutes 1
• ECG monitoring with defibrillator capacity should be initiated immediately in all patients with suspected STEMI 1
• STEMI diagnosis is defined by:
  • ST-segment elevation in two contiguous leads
  • New or presumed new left bundle branch block
  • Isolated ST depression in anterior leads with ST elevation in aVR (suggesting left main or multivessel disease) 2
• Routine oxygen therapy is not recommended in patients with oxygen saturation ≥90% 1

Reperfusion Strategy Selection

• Primary PCI is the preferred reperfusion strategy when performed by an experienced team within 120 minutes of STEMI diagnosis 2, 1
• If the anticipated time from STEMI diagnosis to PCI exceeds 120 minutes, fibrinolysis should be initiated immediately (within 10 minutes of diagnosis) 2, 1
• Patients should be transferred directly to the catheterization laboratory, bypassing the emergency department 2, 1

Primary PCI Strategy

• Immediate antiplatelet therapy should include:
  • Aspirin (oral 150-325 mg or IV 250-500 mg if unable to swallow) 1
  • A potent P2Y12 inhibitor (prasugrel or ticagrelor, or clopidogrel if these are unavailable) 1, 3
• Prasugrel loading dose is 60 mg followed by 10 mg daily maintenance (5 mg for patients <60 kg) 3
• Anticoagulation during PCI should be provided with unfractionated heparin (UFH) as an IV bolus at 100 U/kg (60 U/kg if GPIIb/IIIa inhibitors are used) 1
• Fondaparinux is not recommended for primary PCI 1
• Routine radial access and drug-eluting stent implantation are the standard of care 2
• Routine thrombus aspiration or deferred stenting are contraindicated 2

Fibrinolytic Strategy (when PCI is not available within 120 minutes)

• Fibrinolytic therapy should be initiated as soon as possible, preferably in the pre-hospital setting 1, 4
• A fibrin-specific agent (tenecteplase, alteplase, or reteplase) is recommended 1, 4
• Tenecteplase dosing is weight-adjusted:
  • 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, a 50% dose reduction of tenecteplase is recommended 1, 4
• Adjunctive therapy with fibrinolytics should include:
  • Aspirin (150-325 mg) 1, 4
  • Clopidogrel 1, 4
  • Anticoagulation with enoxaparin (preferred) or unfractionated heparin 1, 4

Post-Fibrinolytic Management

• Transfer to a PCI-capable center following fibrinolysis is indicated for all patients 4
• Rescue PCI is indicated immediately when fibrinolysis has failed (<50% ST-segment resolution at 60-90 minutes) 4
• Angiography and PCI of the infarct-related artery is recommended between 2-24 hours after successful fibrinolysis 4, 5

In-Hospital Management

• Dual antiplatelet therapy (DAPT) with aspirin plus a P2Y12 inhibitor should be maintained for 12 months 1
• High-intensity statin therapy should be initiated as early as possible 1
• Beta-blockers should be started orally in patients with heart failure and/or LVEF <40% unless contraindicated 1
• ACE inhibitors should be started within 24 hours in patients with heart failure, LV systolic dysfunction, diabetes, or anterior infarct 1
• Routine echocardiography should be performed during hospitalization to assess LV and RV function and detect mechanical complications 1

Special Considerations

• In patients with cardiogenic shock, emergency angiography and PCI are recommended 1
• For patients with cardiac arrest and ST-elevation on post-resuscitation ECG, a primary PCI strategy should be pursued 2
• In patients without ST-elevation post-resuscitation but with high suspicion of ongoing myocardial ischemia, urgent angiography should be performed within 2 hours 2
• Women and men receive equal benefit from reperfusion and other STEMI-related therapies and should be managed equally 2

Common Pitfalls and Caveats

• Delays in ECG acquisition and interpretation are common but should be minimized as "time is muscle" 6, 7
• Atypical presentations (especially in women, elderly, and diabetic patients) may lead to delayed diagnosis 2, 6
• Prasugrel is contraindicated in patients with prior stroke/TIA and generally not recommended in patients ≥75 years of age 3
• When possible, prasugrel should be discontinued at least 7 days prior to CABG surgery due to bleeding risk 3
• Non-infarct related artery lesions should be evaluated before hospital discharge in stable patients 2