Management of Non-ST-Elevation Myocardial Infarction (NSTEMI)
Immediate Medical Therapy
All NSTEMI patients must receive dual antiplatelet therapy (aspirin plus a P2Y12 inhibitor) combined with anticoagulation immediately upon diagnosis, followed by risk stratification to determine timing of invasive intervention. 1
Antiplatelet Therapy
- Aspirin: Administer 162-325 mg loading dose (chewed for faster absorption), then 75-100 mg daily indefinitely 2, 1
- P2Y12 Inhibitor Selection:
- Ticagrelor 90 mg twice daily or prasugrel 60 mg loading dose then 10 mg daily are preferred over clopidogrel for higher-risk patients not requiring urgent CABG 2, 1
- For prasugrel specifically: Do not administer the loading dose until coronary anatomy is established in UA/NSTEMI patients 3
- Clopidogrel 75 mg daily is acceptable if ticagrelor or prasugrel are contraindicated 2
- Continue P2Y12 inhibitor for at least 12 months regardless of stent type 2
Anticoagulation
- Enoxaparin (LMWH) is preferred over unfractionated heparin unless renal failure is present or CABG is planned within 24 hours 1
- If using unfractionated heparin: 60 U/kg IV bolus (maximum 4000 units), then 12 U/kg/hr infusion (maximum 1000 units/hr), adjusted to aPTT 1.5-2.5 times control 4
Additional Medical Therapy
- Beta-blockers: Initiate orally within 24 hours unless contraindicated (heart failure signs, low-output state, heart rate <60, systolic BP <100 mmHg) - avoid IV administration in patients with risk factors for cardiogenic shock 1, 4
- Nitrates: Sublingual nitroglycerin 0.4 mg every 5 minutes × 3 doses or IV infusion starting at 10 mcg/min for symptom relief, unless systolic BP <90 mmHg or suspected right ventricular infarction 4
- Oxygen: Only administer if saturation <90% or respiratory distress - routine oxygen is not beneficial 1, 4
Risk Stratification and Timing of Invasive Strategy
The decision for timing of coronary angiography is based on clinical risk features, not physician or patient preference.
Immediate Invasive Strategy (Within 2 Hours)
Proceed directly to catheterization laboratory for: 2, 4
- Refractory angina despite maximal medical therapy
- Hemodynamic instability or cardiogenic shock
- Life-threatening ventricular arrhythmias
- Mechanical complications of MI
- Recurrent angina with ST-segment depression ≥0.05 mV or new bundle branch block
Early Invasive Strategy (Within 12-24 Hours)
High-risk patients should undergo angiography within 12-24 hours if they have: 2, 1
- Elevated troponin levels (troponin T >0.01 ng/mL or troponin I >0.1 ng/mL)
- Dynamic ST-segment or T-wave changes
- TIMI risk score ≥3 or GRACE score >140
- LVEF <40%
- Diabetes mellitus
- Prior PCI or CABG
- Sustained ventricular arrhythmias
Critical Evidence: The ISAR-COOL trial demonstrated that very early invasive strategy (median 2.4 hours) had superior outcomes compared to delayed strategy (median 86 hours), with 30-day death or large MI occurring in 5.9% vs 11.6% (p=0.04) 2, 4
Delayed Invasive or Selective Conservative Strategy
For patients without high-risk features, a delayed invasive approach (beyond 24 hours) or selective invasive strategy based on recurrent ischemia is reasonable 2
Glycoprotein IIb/IIIa Inhibitors
- Use eptifibatide or tirofiban in high-risk UA/NSTEMI patients undergoing PCI 2, 1
- Do not use upstream routinely - reserve for high-risk patients at time of PCI 4
- Avoid in patients not undergoing PCI due to increased bleeding risk without clear benefit 2
Revascularization Strategy
Percutaneous Coronary Intervention (PCI)
- Drug-eluting stents are preferred over balloon angioplasty alone when PCI is performed 1
- PCI is indicated for patients with coronary lesions amenable to PCI and high-risk features 1
Coronary Artery Bypass Grafting (CABG)
CABG is preferred for: 1
- Left main disease >50% stenosis
- Multivessel disease with diabetes or LV dysfunction
- Anatomy unsuitable for PCI
If CABG is planned: Discontinue prasugrel at least 7 days prior to surgery; discontinue clopidogrel 5 days prior 3
Long-Term Secondary Prevention
- High-intensity statin therapy for aggressive lipid lowering 1
- Continue dual antiplatelet therapy (aspirin plus P2Y12 inhibitor) for at least 12 months 2, 1
- Beta-blockers should be continued unless contraindicated 1
- ACE inhibitors for patients with LVEF <40%, hypertension, or diabetes 1
Critical Pitfalls to Avoid
Do NOT Administer Fibrinolytic Therapy
Fibrinolytic therapy is contraindicated in NSTEMI - multiple trials (TIMI 11B) demonstrated no benefit and potential harm, with increased risk of MI 2, 1, 4
Do NOT Delay Invasive Strategy in High-Risk Patients
Delaying angiography for "cooling off" in high-risk patients increases adverse outcomes - the ISAR-COOL trial showed worse outcomes with delayed approach 2, 4
Do NOT Combine Clopidogrel with Omeprazole or Esomeprazole
This combination significantly reduces antiplatelet efficacy 1
Do NOT Use NSAIDs
Both COX-2 selective and nonselective NSAIDs increase mortality, reinfarction, and myocardial rupture risk 4
Do NOT Assume All Patients Benefit Equally from Early Invasive Strategy
The benefit is primarily in medium- to high-risk patients, not low-risk patients 1
Do NOT Proceed with Early Invasive Strategy in Patients with:
- Extensive comorbidities (liver or pulmonary failure, cancer) where risks outweigh benefits 2
- Acute chest pain with low likelihood of ACS 2
- Patients who will not consent to revascularization 2