What is the initial treatment for a patient presenting with Acute Coronary Syndrome (ACS)?

Initial Treatment for Acute Coronary Syndrome (ACS)

Immediately obtain a 12-lead ECG within 10 minutes of presentation to distinguish STEMI from NSTE-ACS, and simultaneously initiate aspirin 150-300 mg loading dose along with cardiac monitoring—these are the most critical first steps that directly impact mortality. 1

Immediate Diagnostic Assessment (First 10 Minutes)

• Obtain 12-lead ECG within 10 minutes of first medical contact to differentiate STEMI (requiring immediate reperfusion) from NSTE-ACS 1
• Draw blood for high-sensitivity cardiac troponin at presentation (time 0), with repeat measurement at 1-2 hours for hs-cTn or 3-6 hours for conventional troponin 1
• Establish continuous cardiac rhythm monitoring to detect life-threatening arrhythmias 1
• Assess hemodynamic status including blood pressure, heart rate, signs of cardiogenic shock (hypotension, altered mental status, cool extremities), and Killip classification for heart failure 1

Immediate Pharmacological Management

Antiplatelet Therapy (Administer Immediately)

• Aspirin 150-300 mg loading dose should be given immediately to all patients without contraindications, even before troponin results return 1, 2, 3
• Add a P2Y12 inhibitor in addition to aspirin for dual antiplatelet therapy 1
  • Ticagrelor is preferred (180 mg loading dose, then 90 mg twice daily) for moderate-to-high risk patients, including those with elevated troponins 1, 2, 3
  • Prasugrel (60 mg loading dose, then 10 mg daily) is recommended for patients proceeding to PCI without contraindications 1
  • Clopidogrel (300-600 mg loading dose, then 75 mg daily) is reserved for patients who cannot receive ticagrelor or prasugrel, though note that CYP2C19 poor metabolizers have reduced effectiveness 1, 4

Anticoagulation

• Initiate parenteral anticoagulation immediately with either low molecular weight heparin or unfractionated heparin 1, 2
• Continue anticoagulation until revascularization or hospital discharge 2

Symptom Management

• Administer sublingual or intravenous nitrates for ongoing chest pain 1, 2
• Initiate beta-blockers unless contraindicated by hypotension, bradycardia, or acute heart failure 2, 3
• Consider calcium channel blockers only if beta-blockers are contraindicated 2

Additional Immediate Therapy

• Start high-intensity statin therapy as early as possible 2, 3

Risk Stratification and Timing of Invasive Strategy

The 2025 ACC/AHA guidelines and ESC guidelines provide clear time-based algorithms based on risk:

Very High-Risk: Immediate Invasive Strategy (<2 hours) 1, 2, 3

• Hemodynamic instability or cardiogenic shock
• Recurrent or refractory chest pain despite medical treatment
• Life-threatening arrhythmias or cardiac arrest
• Mechanical complications of MI
• Acute heart failure with refractory angina or ST deviation
• Recurrent dynamic ST- or T-wave changes, particularly with intermittent ST elevation

High-Risk: Early Invasive Strategy (<24 hours) 1, 2, 3

• Rise or fall in cardiac troponin compatible with MI
• Dynamic ST- or T-wave changes (symptomatic or silent)
• GRACE score >140

Intermediate-Risk: Invasive Strategy (<72 hours) 1, 2, 3

• 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 risk score 109-140

STEMI-Specific Management

• Primary PCI within 120 minutes of presentation is the preferred reperfusion strategy and reduces mortality from 9% to 7% 5
• If PCI cannot be achieved within 120 minutes, administer fibrinolytic therapy (alteplase, reteplase, or tenecteplase at full dose for patients <75 years; half dose for ≥75 years), followed by transfer for PCI within 24 hours 5

Special Considerations

• Urgent echocardiography is indicated for patients with cardiogenic shock, hemodynamic instability, or suspected mechanical complications 1
• For ongoing myocardial ischemia or hemodynamic compromise with regional wall motion abnormality on echo, proceed to immediate coronary angiography regardless of ECG or biomarker findings 1
• In case of ongoing ischemia, place defibrillator patches until urgent revascularization is performed 1

Critical Pitfalls to Avoid

• Do not delay ECG beyond 10 minutes—this is the single most important time-sensitive diagnostic test 1, 2
• Do not wait for troponin results before starting aspirin and antiplatelet therapy in high-risk patients—the benefits far outweigh risks 2
• Do not miss atypical presentations, particularly in women (48% present without chest pain), elderly, and diabetic patients who may present with dyspnea, nausea, or fatigue alone 5
• Avoid concomitant use of clopidogrel with omeprazole or esomeprazole, as these significantly reduce clopidogrel's antiplatelet activity 4
• Do not delay reperfusion therapy for additional diagnostic testing in STEMI patients unless it would immediately change management 1