What is the management of Non-ST-Elevation Myocardial Infarction (NSTEMI)?

Management of Non-ST-Elevation Myocardial Infarction (NSTEMI)

All patients with NSTEMI should receive immediate aspirin 162-325 mg (non-enteric, chewed or oral), anticoagulation, and risk stratification to determine whether an early invasive strategy (angiography within 24-48 hours) or conservative strategy is appropriate, followed by dual antiplatelet therapy and aggressive secondary prevention measures. 1, 2

Immediate Management (First Hours)

Initial Medications - Administer Immediately

• Aspirin 162-325 mg (non-enteric formulation, chewed or oral) as soon as NSTEMI is suspected 1, 3
• Continue aspirin 75-162 mg daily indefinitely thereafter 4, 1
• Admit to monitored unit with continuous rhythm monitoring for at least 24 hours 1, 3
• Supplemental oxygen only if arterial oxygen saturation <90% 1, 3
• Nitroglycerin for ongoing ischemic symptoms unless contraindicated (systolic BP <90 mmHg, severe bradycardia, right ventricular infarction, or recent phosphodiesterase inhibitor use within 24 hours for sildenafil or 48 hours for tadalafil) 1, 3
• Beta-blockers to reduce myocardial oxygen demand by decreasing heart rate, blood pressure, and contractility 1, 3

Anticoagulation - Choose One Agent

Select based on institutional protocols and planned management strategy:

• Unfractionated heparin (UFH): Preferred if early invasive strategy planned due to short half-life and reversibility 4, 3
• Enoxaparin: Continue for duration of hospitalization up to 8 days 4, 1
• Fondaparinux: Continue for duration of hospitalization up to 8 days 4, 1
• Bivalirudin: May discontinue or continue at 0.25 mg/kg/h for up to 72 hours at physician discretion 4

Risk Stratification - Determines Management Strategy

High-Risk Features Requiring Early Invasive Strategy

Perform angiography within 24-48 hours if any of the following are present 4, 1, 2:

• Refractory angina despite medical therapy
• Hemodynamic instability or cardiogenic shock
• Electrical instability (ventricular arrhythmias)
• Elevated cardiac troponin (particularly high-sensitivity troponin)
• ST-segment depression on ECG
• TIMI risk score ≥3 or elevated GRACE score
• Heart failure symptoms or signs
• Left ventricular ejection fraction (LVEF) ≤0.40 4

Conservative Strategy Appropriate For

Lower-risk patients without ongoing ischemia, stable hemodynamics, negative troponin, and no high-risk ECG changes may be managed conservatively with medical therapy and stress testing 4, 1

Dual Antiplatelet Therapy - Timing Is Critical

For Early Invasive Strategy (Angiography <24-48 Hours)

Delay P2Y12 inhibitor loading until coronary anatomy is known to avoid bleeding risk if urgent CABG is needed 5, 6:

• Administer P2Y12 inhibitor loading dose at time of angiography or at catheterization table 4, 1
• Clopidogrel 300-600 mg loading dose, then 75 mg daily 4, 1, 5
• Prasugrel 60 mg loading dose, then 10 mg daily (contraindicated if prior stroke/TIA; reduce to 5 mg daily if weight <60 kg; generally avoid if age ≥75 years) 6
• Ticagrelor per institutional protocol 2

For Conservative Strategy (No Immediate Angiography Planned)

Administer P2Y12 inhibitor loading dose immediately if angiography will be deferred >24-36 hours 4:

• Clopidogrel 300 mg loading dose, then 75 mg daily 4
• Continue for 12 months unless excessive bleeding risk 2

GP IIb/IIIa Inhibitors - Use Selectively

Indications for Upstream (Pre-Angiography) Administration

• High-risk patients (troponin-positive) undergoing early invasive strategy 4
• Options: eptifibatide, tirofiban, or abciximab 4
• May omit if bivalirudin used as anticoagulant AND clopidogrel 300 mg given ≥6 hours earlier 4
• May omit in troponin-negative patients without other high-risk features 4

For Conservative Strategy

GP IIb/IIIa inhibitors may be reasonable for high-risk patients but evidence is weaker 4

Post-Angiography Management - Three Pathways

Pathway 1: PCI Performed

• Continue aspirin indefinitely 4, 1
• Administer P2Y12 inhibitor loading dose if not given before angiography 4, 1
• Continue P2Y12 inhibitor for 12 months 2
• Discontinue anticoagulant after uncomplicated PCI 4
• Discontinue GP IIb/IIIa inhibitor if started previously 4

Pathway 2: CABG Planned

• Continue aspirin 4, 1
• Discontinue clopidogrel 5-7 days before elective CABG 4, 1
• Discontinue prasugrel 7 days before CABG 6
• Discontinue enoxaparin 12-24 hours before CABG and dose with UFH 4
• Discontinue fondaparinux 24 hours before CABG and dose with UFH 4
• Discontinue bivalirudin 3 hours before CABG and dose with UFH 4

Pathway 3: Medical Management (No Revascularization)

• Continue aspirin indefinitely 4, 1
• Administer P2Y12 inhibitor loading dose if not given before angiography 4
• Discontinue GP IIb/IIIa inhibitor if started previously 4
• Continue anticoagulation:
  • UFH for at least 48 hours or until discharge 4
  • Enoxaparin for duration of hospitalization up to 8 days 4
  • Fondaparinux for duration of hospitalization up to 8 days 4
  • Bivalirudin: discontinue or continue at 0.25 mg/kg/h for up to 72 hours 4

Long-Term Management and Secondary Prevention

Mandatory Therapies for All Patients

• Aspirin 75-162 mg daily indefinitely 4, 1
• High-intensity statin therapy regardless of baseline LDL 1
• Beta-blockers unless contraindicated 2
• ACE inhibitors for patients with heart failure, LVEF <0.40, hypertension, or diabetes 4, 1, 2
• ARBs for ACE inhibitor-intolerant patients 4, 1

LVEF Assessment and Follow-Up

• Measure LVEF in all patients 4
• If LVEF ≤0.40: perform diagnostic angiography if not already done 4
• If LVEF >0.40: perform stress test 4

Lifestyle Modifications

• Cardiac rehabilitation recommended, particularly for moderate-to-high-risk patients 4
• Physical activity: 30-60 minutes of moderate aerobic activity 5-7 days per week 4
• Weight management: target BMI 18.5-24.9 kg/m² and waist circumference <40 inches (men) or <35 inches (women) 4
• Smoking cessation: intensive counseling and pharmacotherapy 4

Critical Contraindications and Pitfalls

Absolute Contraindications

• Fibrinolytic therapy is contraindicated in NSTEMI without ST-segment elevation 4
• Prasugrel is contraindicated in patients with prior stroke or TIA 6

Medications to Avoid

• NSAIDs (except aspirin) increase mortality, reinfarction, hypertension, heart failure, and myocardial rupture risk 4, 1
• Immediate-release dihydropyridine calcium channel blockers without adequate beta-blockade 1, 3
• Intravenous ACE inhibitors within first 24 hours due to hypotension risk 1, 3
• Omeprazole or esomeprazole with clopidogrel due to significant reduction in antiplatelet activity 5

Bleeding Risk Management

• Clopidogrel: platelet inhibition lasts 7-10 days; platelet transfusions may be less effective within 4 hours of loading dose or 2 hours of maintenance dose 5
• Prasugrel: higher bleeding risk than clopidogrel, especially in patients ≥75 years, weight <60 kg, or history of stroke 6
• Consider dose reduction: prasugrel 5 mg daily (instead of 10 mg) for patients <60 kg 6

Special Populations

• Patients on warfarin: do not initiate anticoagulant therapy until INR <2.0; however, initiate antiplatelet therapy even if therapeutically anticoagulated, especially if invasive strategy planned 4
• Elderly patients (≥75 years): prasugrel generally not recommended except in high-risk situations (diabetes or prior MI) 6