Acute Treatment of Suspected ACS
For all patients with suspected acute coronary syndrome, immediately administer aspirin 150-300 mg orally (or 75-250 mg IV if unable to swallow), obtain a 12-lead ECG within 10 minutes, and measure high-sensitivity cardiac troponin with results available within 60 minutes. 1, 2
Immediate Actions (First 10 Minutes)
ECG and Monitoring
- Obtain 12-lead ECG within 10 minutes of first medical contact and have it interpreted immediately by an experienced physician 1, 2
- Start continuous cardiac rhythm monitoring with defibrillator capacity 3
- If initial ECG is nondiagnostic but clinical suspicion remains high, obtain serial ECGs 2
- Consider additional leads (V3R, V4R, V7-V9) if standard leads are inconclusive and ongoing ischemia is suspected 1
Initial Pharmacotherapy
Aspirin (Class I):
- Loading dose: 150-300 mg orally or 75-250 mg IV if unable to swallow 1
- Maintenance: 75-100 mg daily (or 81 mg if using ticagrelor) 4, 1
Nitrates (Class IC):
- Sublingual nitroglycerin for symptom relief, followed by IV administration if chest pain persists 5, 6
- Do NOT use in patients with hypotension, right ventricular infarction, or recent phosphodiesterase inhibitor use
Morphine (Class IC):
- Indicated when symptoms are not immediately relieved with nitroglycerin or when acute pulmonary congestion/agitation is present 5
- Use cautiously as it may delay absorption of oral antiplatelet agents
Oxygen:
- Only administer if SaO2 <90% - routine oxygen is NOT recommended 3
Risk Stratification Based on ECG Findings
STEMI (ST-Elevation Present)
If ST-elevation in ≥2 contiguous leads or new LBBB:
- Activate cardiac catheterization lab immediately with goal of first medical contact-to-device time ≤90 minutes 2
- Primary PCI is the preferred reperfusion strategy 3, 2
- If PCI cannot be performed within 120 minutes, initiate fibrinolytic therapy within 30 minutes if no contraindications 3, 7
- Administer potent P2Y12 inhibitor (prasugrel 60 mg or ticagrelor 180 mg loading dose) before or at time of PCI 3
NSTE-ACS (No Persistent ST-Elevation)
Timing of invasive strategy depends on risk stratification:
Immediate invasive strategy (<2 hours) - Very High Risk: 6
- Hemodynamic instability or cardiogenic shock
- Recurrent/ongoing chest pain refractory to medical treatment
- Life-threatening arrhythmias or cardiac arrest
- Mechanical complications of MI
- Acute heart failure with refractory angina or ST deviation
- Recurrent dynamic ST/T-wave changes, particularly with intermittent ST elevation
Early invasive strategy (<24 hours) - High Risk: 6
- Rise or fall in cardiac troponin compatible with MI
- Dynamic ST or T-wave changes (symptomatic or silent)
- GRACE score >140
Invasive strategy (<72 hours) - Intermediate Risk: 6
- Diabetes mellitus
- Renal insufficiency (eGFR <60 mL/min/1.73 m²)
- LVEF <40% or congestive heart failure
- Early post-infarction angina
- Recent PCI or prior CABG
- GRACE score 109-140
Antiplatelet Therapy for NSTE-ACS
Dual antiplatelet therapy (DAPT) is mandatory for 12 months unless excessive bleeding risk: 6, 1, 6
P2Y12 Inhibitor Selection:
Ticagrelor (PREFERRED for most patients): 6, 1
- Loading dose: 180 mg
- Maintenance: 90 mg twice daily
- Recommended for all moderate-to-high risk patients regardless of invasive vs. conservative strategy
- Can be given to patients already on clopidogrel (discontinue clopidogrel when starting ticagrelor)
- Contraindications: Previous intracranial hemorrhage or ongoing bleeding
Prasugrel (for invasive strategy ONLY): 6, 1
- Loading dose: 60 mg
- Maintenance: 10 mg daily (5 mg if age ≥75 years or weight <60 kg)
- Give ONLY after coronary anatomy is known and patient is proceeding to PCI 6
- Contraindications: Previous intracranial hemorrhage, previous ischemic stroke/TIA, ongoing bleeding, generally not recommended if age ≥75 years or weight <60 kg
Clopidogrel (third-line option): 6, 1
- Loading dose: 300-600 mg
- Maintenance: 75 mg daily
- Use only when ticagrelor or prasugrel are unavailable, contraindicated, or patient requires oral anticoagulation
Anticoagulation Therapy
All patients require parenteral anticoagulation in addition to antiplatelet therapy: 4
Options (choose ONE):
Enoxaparin: 4
- 1 mg/kg SC every 12 hours
- Reduce to 1 mg/kg SC once daily if CrCl <30 mL/min
- Continue until PCI or hospital discharge
Fondaparinux: 4
- 2.5 mg SC daily
- Continue until PCI or hospital discharge
- CRITICAL: Must add UFH or bivalirudin during PCI due to catheter thrombosis risk 4
Unfractionated Heparin (UFH): 4
- Loading: 60 IU/kg IV (max 4000 IU)
- Infusion: 12 IU/kg/hour (max 1000 IU/hour)
- Adjust per aPTT per hospital protocol
- Continue for 48 hours or until PCI
Bivalirudin (for early invasive strategy only): 4
- Loading: 0.10 mg/kg
- Infusion: 0.25 mg/kg/hour
- Continue until angiography/PCI
Troponin Testing Strategy
Use high-sensitivity cardiac troponin with 0h/1h algorithm (preferred): 1
- Measure at presentation (0h) and at 1 hour
- If inconclusive and clinical suspicion persists, recheck at 3 hours 1
- Alternative: 0h/2h algorithm if validated for your specific assay 1
Additional Acute Therapies
Beta-blockers (Class IB): 5
- Initiate IV then oral beta-blockers unless contraindicated
- Avoid in acute heart failure, hemodynamic instability, or high-degree AV block
High-intensity statin: 6
- Start immediately unless contraindicated
- Continue long-term for secondary prevention
ACE inhibitors:
- Initiate early, particularly if anterior MI, heart failure, or LVEF <40%
Critical Pitfalls to Avoid
- DO NOT give fibrinolytics in NSTE-ACS - this causes harm 4
- DO NOT give prasugrel before knowing coronary anatomy 6
- DO NOT forget additional anticoagulant if using fondaparinux at PCI 4
- DO NOT use routine oxygen unless SaO2 <90% 3
- DO NOT delay aspirin - give immediately even before troponin results
- DO NOT use GP IIb/IIIa inhibitors routinely - only consider in high-risk patients during early invasive strategy 4