How do you manage a patient with non ST-elevation myocardial infarction (non-STEMI)?

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

All patients with NSTEMI require immediate aspirin 162-325 mg (non-enteric, chewed or oral), dual antiplatelet therapy with a P2Y12 inhibitor (preferably ticagrelor), parenteral anticoagulation, and risk stratification to determine timing of invasive coronary angiography. 1, 2, 3

Immediate Initial Management (First Hour)

• Administer aspirin 162-325 mg immediately as a non-enteric formulation, either chewed or taken orally, regardless of prior aspirin use 1, 3
• Admit to a monitored unit with continuous cardiac rhythm monitoring for at least 24 hours to detect life-threatening arrhythmias 1, 3
• Provide supplemental oxygen only if arterial oxygen saturation is <90%—routine oxygen administration is not indicated and may be harmful 1, 2, 3
• Administer sublingual or intravenous nitroglycerin for ongoing ischemic chest pain, but avoid if:
  • Systolic blood pressure <90 mmHg or ≥30 mmHg below baseline 1, 3
  • Severe bradycardia (<50 bpm) or tachycardia (>100 bpm without heart failure) 1
  • Right ventricular infarction 1, 3
  • Phosphodiesterase inhibitor use within 24 hours (sildenafil) or 48 hours (tadalafil) 1, 3
• Initiate oral beta-blocker therapy (preferred over intravenous) to reduce myocardial oxygen demand by decreasing heart rate, blood pressure, and contractility, unless contraindications exist 1

Antiplatelet Therapy Strategy

Aspirin

• Continue aspirin 75-162 mg daily indefinitely after the initial loading dose 1, 2, 3

P2Y12 Inhibitor Selection

• Ticagrelor is the preferred P2Y12 inhibitor for all NSTEMI patients, with a loading dose of 180 mg followed by 90 mg twice daily, regardless of invasive or conservative strategy 1, 2, 3
• Prasugrel (loading dose 60 mg, maintenance 10 mg daily; 5 mg daily if age ≥75 years or weight <60 kg) is an alternative for patients naive to P2Y12 inhibitors undergoing PCI 2
• Clopidogrel (loading dose 300-600 mg, maintenance 75 mg daily) should only be used when ticagrelor or prasugrel are unavailable, not tolerated, or contraindicated 2, 4
• Continue P2Y12 inhibitor for 12 months unless contraindicated or high bleeding risk 1, 2, 3

Critical Clopidogrel Caveat

• Clopidogrel is significantly less effective in CYP2C19 poor metabolizers (approximately 2% of White, 4% of Black, and 14% of Chinese patients), who form less active metabolite and have reduced antiplatelet effects 4
• Consider genetic testing for CYP2C19 status and use an alternative P2Y12 inhibitor (ticagrelor or prasugrel) in identified poor metabolizers 4

Anticoagulant Therapy

• Administer parenteral anticoagulation to all NSTEMI patients in addition to antiplatelet therapy 1, 2, 3

Agent Selection Based on Clinical Context

• Unfractionated heparin (UFH): Continue for at least 48 hours or until discharge if given before angiography 5, 1, 3
• Enoxaparin: Continue for duration of hospitalization, up to 8 days, if given before angiography 5, 1, 3
• Fondaparinux: Continue for duration of hospitalization, up to 8 days, if given before angiography; must add UFH bolus during PCI to prevent catheter thrombosis 5, 1, 3
• Bivalirudin: Either discontinue or continue at 0.25 mg/kg/h for up to 72 hours at physician's discretion if given before angiography 5

Renal Function Considerations

• For severe renal impairment (CrCl <30 mL/min), UFH is preferred as it does not accumulate with renal dysfunction 3
• Enoxaparin requires dose adjustment in moderate renal impairment 3

Critical Anticoagulation Pitfall

• Never switch between anticoagulants as this significantly increases bleeding risk 3

Risk Stratification and Invasive Strategy Timing

Very High-Risk (Immediate Invasive Strategy <2 Hours)

• Refractory or recurrent angina despite medical therapy 5, 1, 3
• Hemodynamic instability or cardiogenic shock 5, 1, 3
• Life-threatening arrhythmias or cardiac arrest 5, 1, 3
• Acute heart failure 3

High-Risk (Early Invasive Strategy <24-48 Hours)

• Elevated cardiac biomarkers (troponin-positive) 5, 1, 3
• Dynamic ST-segment or T-wave changes 3
• High GRACE or TIMI risk score 1, 2, 3
• Diabetes mellitus 3

Lower-Risk (Conservative Strategy)

• Appropriate for patients without ongoing ischemia or significant comorbidities where invasive risks outweigh benefits 1, 2, 3
• Measure LVEF: If ≤0.40, perform diagnostic angiography; if >0.40, perform stress test 5, 2, 3

Post-Angiography Management

If PCI Selected

• Continue aspirin 5, 3
• Administer P2Y12 inhibitor loading dose if not started before diagnostic angiography 5, 3
• Administer intravenous GP IIb/IIIa inhibitor (abciximab, eptifibatide, or tirofiban) for troponin-positive and other high-risk patients if not started before angiography 5
  • Exception: GP IIb/IIIa inhibitor may be omitted if bivalirudin was selected as anticoagulant and at least 300 mg clopidogrel was given ≥6 hours earlier 5
• Discontinue anticoagulant therapy after PCI for uncomplicated cases 5

If CABG Selected

• Continue aspirin 5, 3
• Discontinue clopidogrel 5-7 days before elective CABG 5, 3
• Discontinue prasugrel at least 7 days before surgery 2
• Discontinue ticagrelor at least 5 days before surgery 2
• Discontinue GP IIb/IIIa inhibitor 4 hours before CABG 5
• Anticoagulant management:
  • Continue UFH 5
  • Discontinue enoxaparin 12-24 hours before CABG and dose with UFH 5
  • Discontinue fondaparinux 24 hours before CABG and dose with UFH 5
  • Discontinue bivalirudin 3 hours before CABG and dose with UFH 5

If Medical Therapy Selected

• Continue aspirin 5
• Administer P2Y12 inhibitor loading dose if not given before diagnostic angiography 5
• Discontinue intravenous GP IIb/IIIa inhibitor if started previously 5
• Continue anticoagulation as outlined above for duration of hospitalization 5

Long-Term Secondary Prevention

• Measure LVEF in all patients 5, 2, 3
• Initiate ACE inhibitors for patients with heart failure, LV dysfunction (LVEF <0.40), hypertension, or diabetes 1, 2, 3
• Consider ARBs for ACE inhibitor-intolerant patients 2, 3
• Continue beta-blockers indefinitely in all NSTEMI patients without contraindications 1, 3
• Initiate high-intensity statin therapy regardless of baseline LDL levels 1, 3
• For patients requiring long-term oral anticoagulation, use triple antithrombotic therapy (aspirin + P2Y12 inhibitor + anticoagulant) for the shortest duration possible, typically 1 week to 1 month, then transition to dual therapy 3

Critical Contraindications and Pitfalls to Avoid

• Fibrinolytic therapy is absolutely contraindicated in NSTEMI patients without ST-segment elevation 5, 1
• NSAIDs (except aspirin) must not be administered during hospitalization due to increased mortality, reinfarction, hypertension, heart failure, and myocardial rupture 1, 3
• Immediate-release dihydropyridine calcium channel blockers should not be given without adequate beta-blockade 1, 3
• Intravenous ACE inhibitors should be avoided within the first 24 hours due to hypotension risk (exception: refractory hypertension) 1, 3
• Intravenous beta-blockers should not be administered to patients with signs of heart failure, low-output state, or cardiogenic shock risk factors 1
• Do not use fondaparinux as sole anticoagulant during PCI—it must be supplemented with UFH bolus to prevent catheter thrombosis 3