What are the differences in management between STEMI (ST-Elevation Myocardial Infarction) and NSTEMI (Non-ST-Elevation Myocardial Infarction)?

Management Differences Between STEMI and NSTEMI

The primary difference in management between STEMI and NSTEMI is the timing of reperfusion therapy, with STEMI requiring immediate reperfusion (ideally within 90 minutes of first medical contact) while NSTEMI management follows a risk-stratified approach with early invasive strategy typically within 24-72 hours. 1

Pathophysiology and Diagnosis

• STEMI: Characterized by complete coronary artery occlusion with persistent ST-segment elevation on ECG
• NSTEMI: Characterized by subtotally occlusive thrombus without persistent ST-segment elevation, diagnosed by elevated cardiac troponins 1

The distinction between these two forms of acute coronary syndrome (ACS) is critical as it determines the urgency and approach to management.

Initial Management

STEMI Management

1. Immediate reperfusion therapy (door-to-balloon time ≤90 minutes)

   • Primary percutaneous coronary intervention (PCI) is preferred
   • Fibrinolytic therapy if PCI cannot be performed within 120 minutes of first medical contact 2, 1

2. Pharmacotherapy:

   • Dual antiplatelet therapy (DAPT): Aspirin plus P2Y12 inhibitor (loading dose)
   • Anticoagulation with unfractionated heparin during primary PCI
   • Consider glycoprotein IIb/IIIa inhibitors in high-risk cases 3

NSTEMI Management

1. Risk stratification using validated tools (GRACE, TIMI scores)

   • High-risk features: Ongoing chest pain, hemodynamic instability, heart failure, arrhythmias, dynamic ST-T changes

2. Timing of invasive strategy:

   • Early invasive (<24 hours): For high-risk patients
   • Delayed invasive (24-72 hours): For intermediate-risk patients
   • Selective invasive: For low-risk patients 2, 1

3. Pharmacotherapy:

   • DAPT: Aspirin plus P2Y12 inhibitor (clopidogrel, ticagrelor, or prasugrel)
   • Anticoagulation: Low molecular weight heparin, fondaparinux, or unfractionated heparin 2

Antiplatelet and Anticoagulation Therapy

STEMI

• Immediate loading dose of P2Y12 inhibitor (prasugrel 60mg or clopidogrel 300-600mg)
• Anticoagulation during PCI with unfractionated heparin
• Consider GP IIb/IIIa inhibitors for large thrombus burden 3

NSTEMI

• P2Y12 inhibitor timing may be deferred until coronary anatomy is known if early CABG is likely
• Longer duration anticoagulation before catheterization
• Fondaparinux may be preferred for patients not going for immediate angiography 2

Clinical Outcomes and Prognosis

• STEMI: Higher short-term mortality due to complete occlusion and larger infarct size
• NSTEMI: Higher long-term mortality due to greater comorbidity burden and older age 1

Recent research shows that approximately 40% of patients with acute coronary occlusion do not present with STEMI criteria (NSTEMI-OMI), leading to treatment delays and increased morbidity 4, 5. These patients have similar angiographic findings and complications as STEMI patients but experience significant delays to catheterization.

Secondary Prevention

For both STEMI and NSTEMI:

• DAPT for 12 months (aspirin plus P2Y12 inhibitor)
• High-intensity statin therapy
• Beta-blockers (especially with reduced ejection fraction)
• ACE inhibitors/ARBs for patients with hypertension, diabetes, or LV dysfunction
• Cardiac rehabilitation
• Risk factor modification 1

Common Pitfalls and Caveats

1. Delayed recognition of NSTEMI-OMI: Some NSTEMI patients have complete coronary occlusion but don't meet STEMI criteria, leading to delayed reperfusion and worse outcomes 4, 5

2. Overreliance on troponin: Initial troponin may be normal in early presenters; serial measurements are essential

3. Underestimating NSTEMI risk: Despite lacking ST elevation, NSTEMI patients often have extensive coronary disease and worse long-term outcomes 6

4. Inappropriate risk stratification: Failure to properly risk-stratify NSTEMI patients may lead to suboptimal timing of invasive management

5. Bleeding risk with antithrombotic therapy: Careful assessment of bleeding risk is essential, especially in elderly patients and those with low body weight (<60kg) 3

By understanding these key differences in management approaches between STEMI and NSTEMI, clinicians can optimize outcomes for patients across the spectrum of acute coronary syndromes.