What are the treatment criteria for a patient with suspected Non-ST-Elevation Myocardial Infarction (NSTEMI)?

NSTEMI Treatment Criteria

The definitive treatment criteria for suspected NSTEMI include immediate administration of aspirin (162-325 mg loading dose followed by 75-100 mg daily), a P2Y12 inhibitor (clopidogrel, ticagrelor, or prasugrel), anticoagulation therapy, and risk stratification to determine the timing of invasive management. 1

Initial Assessment and Diagnosis

• Diagnostic criteria:

  • Elevated cardiac troponins (the definitive diagnostic marker)
  • Serial measurements at presentation and 3-6 hours later
  • ECG changes (ST-segment depression ≥0.5 mm, T-wave inversions >1 mm)
  • Note: Normal ECG does not exclude NSTEMI (occurs in 1-6% of cases) 1

• Immediate measures:

  • Continuous cardiac monitoring
  • Oxygen if SaO₂ <90% or respiratory distress
  • IV access establishment
  • 12-lead ECG within 10 minutes of arrival 1

Risk Stratification

• High-risk features include: 1

  • Age ≥65 years
  • ≥3 coronary artery disease risk factors
  • Known coronary stenosis ≥50%
  • ST-segment deviation on ECG
  • ≥2 anginal episodes in past 24 hours
  • Elevated cardiac markers
  • Prior aspirin use

• Validated risk scoring systems:

  • TIMI Risk Score
  • GRACE Risk Score
  • PURSUIT Risk Score 1

Pharmacological Management

Antiplatelet Therapy

1. Aspirin: 2, 1

   • 162-325 mg loading dose (chewed, non-enteric coated) immediately
   • 75-100 mg daily maintenance dose
   • Continue indefinitely

2. P2Y12 Inhibitor: 2, 1, 3

   • Clopidogrel: 300-600 mg loading dose, then 75 mg daily
   • Ticagrelor: 180 mg loading dose, then 90 mg twice daily
   • Prasugrel: 60 mg loading dose, then 10 mg daily (only after coronary anatomy is known)
   • Continue for 12 months in patients receiving drug-eluting stents (DES) and up to 12 months for bare-metal stents (BMS)

3. Glycoprotein IIb/IIIa inhibitors: 2

   • Consider for high-risk patients, particularly those with elevated troponins
   • Options include eptifibatide and tirofiban
   • Can be administered early ("upstream") or deferred until angiography

Anticoagulation Therapy

• Options include: 2, 1
  • Unfractionated heparin (UFH): 60-70 U/kg IV bolus, 12-15 U/kg/hr
  • Enoxaparin: 1 mg/kg SC every 12 hours
  • Fondaparinux: 2.5 mg SC daily
  • Continue for at least 48 hours or until revascularization

Management Strategy

Early Invasive Strategy (within 24-48 hours)

• Indicated for high-risk patients with: 2, 1
  • Refractory angina
  • Hemodynamic instability
  • Electrical instability
  • Elevated cardiac biomarkers
  • ST-segment changes
  • GRACE score >140
  • Diabetes mellitus
  • Reduced left ventricular function (EF <40%)
  • Recent PCI or prior CABG

Conservative Strategy

• For low-risk patients: 2
  • Stress testing should be performed
  • If stress test indicates high risk, proceed to diagnostic angiography
  • If low risk after stress testing:
    • Continue aspirin indefinitely
    • Continue P2Y12 inhibitor for at least 1 month and ideally up to 1 year
    • Discontinue IV GP IIb/IIIa inhibitor if started
    • Continue anticoagulation for up to 8 days

Revascularization Considerations

For Patients Undergoing PCI

• Continue aspirin (preferably 81 mg/day) 2
• Administer loading dose of P2Y12 inhibitor if not given previously 2
• Consider GP IIb/IIIa inhibitor for troponin-positive and high-risk patients 1

For Patients Undergoing CABG

• Continue aspirin 2
• Discontinue clopidogrel 5-7 days before surgery 2
• Discontinue ticagrelor at least 5 days before surgery 2
• Discontinue IV GP IIb/IIIa inhibitor 4 hours before CABG 2
• Manage anticoagulant therapy appropriately:
  • Continue UFH
  • Discontinue enoxaparin 12-24 hours before CABG
  • Discontinue fondaparinux 24 hours before CABG 2

Secondary Prevention

• Beta-blockers for all patients unless contraindicated 2
• ACE inhibitors/ARBs for patients with reduced left ventricular function, hypertension, or diabetes 2
• High-intensity statins 1
• Lifestyle modifications (smoking cessation, exercise, healthy diet) 1
• Cardiac rehabilitation 1

Important Caveats

• Fibrinolytic therapy is contraindicated in NSTEMI 1
• Monitor for bleeding complications with dual antiplatelet therapy and anticoagulation 1
• Consider proton pump inhibitors for patients at high risk of gastrointestinal bleeding 1
• Prasugrel should not be used in patients with history of stroke or TIA 2
• For patients on ticagrelor, limit aspirin dose to 81 mg daily 2

The CURE trial demonstrated that dual antiplatelet therapy with aspirin and clopidogrel reduced the risk of cardiovascular death, MI, or stroke by 20% compared to aspirin alone in NSTEMI patients 3, highlighting the importance of this treatment approach.