Would you consider a patient with new ST depressions on lateral leads, negative troponin (cardiac biomarker) levels, and persistent chest pain as having a non-ST elevation myocardial infarction (NSTEMI) and initiate anticoagulation with heparin (unfractionated heparin) infusion?

Management of Suspected ACS with ST Depressions and Negative Troponins

This patient does NOT meet criteria for NSTEMI and should be classified as unstable angina (UA), but anticoagulation with heparin is still strongly indicated given the high-risk features of new ST depressions and ongoing chest pain. 1

Diagnostic Classification

The distinction between NSTEMI and unstable angina hinges entirely on cardiac biomarkers:

• NSTEMI requires elevated troponin (above the 99th percentile) in addition to clinical evidence of ischemia 2
• Three negative troponins definitively exclude NSTEMI by current diagnostic criteria, classifying this as unstable angina 1
• However, new ST depressions ≥0.5 mm on lateral leads during symptomatic episodes represent high-risk unstable angina requiring aggressive medical therapy 1, 3

Risk Stratification: This is a HIGH-RISK Patient

The presence of ST-segment depression places this patient in a higher mortality risk category compared to those with normal ECGs or isolated T-wave changes, even with negative biomarkers 1, 3:

• ST depressions ≥0.05 mV (0.5 mm) during chest pain strongly suggest acute ischemia and very high likelihood of severe underlying coronary disease 1, 3
• Patients with ST-segment deviation have progressively greater mortality risk independent of troponin status 1
• Persistent chest pain despite medical therapy is itself a high-risk feature 1

Anticoagulation: YES, Start Heparin Immediately

Anticoagulation is recommended for ALL patients with unstable angina/NSTEMI, regardless of troponin status, in addition to antiplatelet therapy 1. The evidence strongly supports this:

Heparin Dosing Options (Choose One):

Unfractionated Heparin (UFH):

• Initial bolus: 60 IU/kg IV (maximum 4000 IU) 1
• Continuous infusion: 12 IU/kg/hour (maximum 1000 IU/hour) 1
• Adjust to maintain aPTT 1.5-2 times normal (50-70 seconds target) 1, 4
• Continue for 48 hours or until PCI is performed 1
• Monitor aPTT every 4 hours initially, then at appropriate intervals 4

OR Low Molecular Weight Heparin (Preferred):

• Enoxaparin: 1 mg/kg subcutaneous every 12 hours (reduce to once daily if CrCl <30 mL/min) 1
• Continue for duration of hospitalization or until PCI 1
• Enoxaparin is preferable to UFH unless CABG is planned within 24 hours 1

OR Fondaparinux:

• 2.5 mg subcutaneous daily 1
• Critical caveat: Must add UFH bolus during PCI to prevent catheter thrombosis 1

Complete Initial Medical Management Algorithm

Immediate Interventions (Within 10 Minutes):

1. Aspirin 162-325 mg orally immediately (if not already given) 1, 3
2. Start anticoagulation with one of the regimens above 1
3. Add P2Y12 inhibitor:
   • Clopidogrel 300-600 mg loading dose, then 75 mg daily 1
   • OR Ticagrelor 180 mg loading dose (preferred over clopidogrel) 1
4. Beta-blocker if no contraindications 1, 3
5. Nitrates (sublingual or IV) for ongoing chest pain 1, 3

Monitoring Requirements:

• Serial troponins: Repeat at 6-12 hours to definitively exclude evolving MI 1, 2
• Continuous ECG monitoring for at least 24 hours to detect arrhythmias 3
• aPTT monitoring if using UFH (every 4 hours initially) 1, 4
• Platelet counts, hematocrit, and occult blood monitoring throughout therapy 4

Invasive Strategy: YES, This Patient Needs Angiography

This patient meets criteria for early invasive strategy (coronary angiography within 24-48 hours) based on multiple high-risk features 1:

High-Risk Features Present:

• New ST depressions on ECG 1, 3
• Persistent/recurrent chest pain despite medical therapy 1

Timing of Angiography:

• Plan for angiography within 24-48 hours for most high-risk UA patients 1, 3
• Immediate angiography (within 1 hour) only if develops: severe ongoing ischemia, hemodynamic instability, or major arrhythmias 1, 3

Additional Antiplatelet Therapy Before Angiography:

Consider adding GP IIb/IIIa inhibitor (eptifibatide or tirofiban) before diagnostic angiography in this high-risk patient with ST depressions 1:

• Class I recommendation for upstream GP IIb/IIIa inhibitor OR clopidogrel before angiography in early invasive strategy 1
• Class IIb recommendation specifically for GP IIb/IIIa inhibitor in patients with intermediate/high-risk features like positive troponin or ST changes 1

Critical Pitfalls to Avoid

1. DO NOT give fibrinolytic therapy - this is absolutely contraindicated in isolated ST depression and may increase mortality 1, 3
2. DO NOT dismiss ST depressions as "non-specific" when they occur during symptomatic episodes 3
3. DO NOT crossover between UFH and LMWH - pick one anticoagulant and stick with it 1
4. DO NOT withhold anticoagulation based on negative troponins alone - the ST depressions and ongoing symptoms mandate treatment 1
5. DO NOT delay angiography in this high-risk patient - plan for invasive evaluation within 24-48 hours 1, 3

Consider Type 2 MI Mechanisms

While treating as high-risk unstable angina, actively search for supply-demand mismatch conditions that could represent Type 2 MI pathophysiology 2, 3:

• Severe hypertension or hypotension 2, 3
• Tachyarrhythmias 2, 3
• Severe anemia 2, 3
• Hypoxemia or respiratory failure 2, 3
• Metabolic derangements 3

If a precipitating condition is identified, treating the underlying cause becomes the primary focus while continuing anticoagulation and antiplatelet therapy 2, 3.