Management of Non-ST-Elevation Myocardial Infarction (NSTEMI)
All NSTEMI patients should receive immediate dual antiplatelet therapy (aspirin 162-325 mg loading dose plus a P2Y12 inhibitor) combined with anticoagulation, followed by risk stratification to determine timing of coronary angiography within 2 hours to 48 hours based on clinical risk features. 1, 2
Immediate Medical Therapy (Within Minutes of Diagnosis)
Antiplatelet Therapy
- Aspirin 162-325 mg loading dose (chewed for faster absorption), then 75-100 mg daily indefinitely 1, 2
- Add a P2Y12 inhibitor immediately:
- Prasugrel 60 mg loading dose, then 10 mg daily is preferred for patients undergoing PCI (reduce to 5 mg daily if weight <60 kg) 3
- Ticagrelor is preferred over clopidogrel for higher-risk patients not requiring urgent CABG 2
- Clopidogrel 300 mg loading dose, then 75 mg daily if prasugrel/ticagrelor contraindicated 1, 4
- Critical caveat: Avoid combining clopidogrel with omeprazole or esomeprazole as this significantly reduces antiplatelet efficacy 1, 4
Anticoagulation
- Enoxaparin (LMWH) is preferable to 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 2
Additional Medical Therapy
- Beta-blockers should be initiated 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, 2
- 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 2
- Morphine sulfate 2-4 mg IV with increments of 2-8 mg IV at 5-15 minute intervals for refractory chest pain 2
- Oxygen therapy only if saturation <90% - routine oxygen is not beneficial 2
Risk Stratification for Timing of Invasive Strategy
Immediate Angiography (Within 2 Hours)
Proceed immediately to catheterization laboratory for patients with: 5, 2
- Refractory angina despite maximal medical therapy
- Hemodynamic instability or cardiogenic shock
- Life-threatening ventricular arrhythmias
- Mechanical complications
- Recurrent angina with ST-segment depression ≥0.05 mV or new bundle branch block
Early Invasive Strategy (Within 12-24 Hours)
Recommended for high-risk patients with: 5, 1, 2
- Elevated troponin (troponin T >0.01 ng/mL or troponin I >0.1 ng/mL)
- Dynamic ST-segment or T-wave changes
- GRACE score >140
- TIMI risk score ≥3
- LVEF <40%
- Diabetes mellitus
- Prior PCI or CABG
- Heart failure signs
- Serious ventricular arrhythmias
The TACTICS-TIMI 18 trial demonstrated that early invasive strategy reduced death/MI/rehospitalization at 6 months from 19.4% to 15.9% (p=0.025) in high-risk patients 1
Delayed Invasive Strategy (Within 24-48 Hours)
Reasonable for initially stabilized patients without high-risk features 5
Conservative Strategy (Selective Invasive)
May be considered only for: 5
- Low-risk patients without elevated troponin or high-risk features
- Patients with extensive comorbidities where risks of revascularization outweigh benefits (liver or pulmonary failure, cancer)
- Patients who will not consent to revascularization
GP IIb/IIIa Inhibitor Use
An intravenous GP IIb/IIIa inhibitor (eptifibatide or tirofiban) is generally recommended in UA/NSTEMI patients undergoing PCI 5
For patients managed conservatively, GP IIb/IIIa inhibitors should NOT be used routinely upstream but reserved for high-risk patients undergoing PCI 2
Revascularization Strategy Selection
PCI Indications (Class I)
PCI is indicated for: 5
- Patients with coronary lesions amenable to PCI and high-risk features
- 1- or 2-vessel CAD with or without significant proximal LAD but with large area of viable myocardium and high-risk criteria on noninvasive testing
- Multivessel disease with suitable anatomy, normal LV function, and without diabetes
CABG Indications
CABG is preferred for: 5
- Left main disease >50% stenosis
- Multivessel disease with diabetes or LV dysfunction
- Anatomy unsuitable for PCI
Critical Pitfalls to Avoid
Never administer fibrinolytic therapy in NSTEMI patients - multiple trials (TIMI 11B) demonstrated no benefit and potential harm 5, 2
Do not delay angiography for "cooling off" period in high-risk patients - the ISAR-COOL trial showed that prolonged medical stabilization (median 86 hours) before angiography increased death/MI compared to early approach (median 2.4 hours) 1, 2
Avoid NSAIDs - both COX-2 selective and nonselective agents increase mortality, reinfarction, and myocardial rupture risk 2
Do not start prasugrel in patients likely to undergo urgent CABG - discontinue at least 7 days prior to surgery when possible 3
Prasugrel is contraindicated in patients with prior TIA or stroke - these patients had 6.5% stroke rate on prasugrel versus 1.2% on clopidogrel 3
Consider genetic testing for CYP2C19 poor metabolizers on clopidogrel - these patients form less active metabolite and have reduced antiplatelet effect; consider alternative P2Y12 inhibitor 4
Monitoring and Secondary Prevention
Acute Monitoring
- Continuous ECG monitoring with defibrillator capacity 2
- Serial troponin measurements at presentation, 3-6 hours, and if clinically indicated 2
- Repeat ECG if symptoms recur or worsen 2