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

Initial Treatment Criteria for Acute Coronary Syndrome

All patients with suspected ACS must receive immediate ECG within 10 minutes of first medical contact, aspirin 150-300 mg loading dose, and be evaluated in an emergency department with continuous cardiac monitoring. 1, 2

Immediate Assessment (Within 10 Minutes)

The initial evaluation must rapidly establish a working diagnosis based on three key parameters:

• ECG findings to detect ST-segment elevation or depression, T-wave changes, or other ischemic abnormalities 1
• Chest pain characteristics including quality, duration, persistence, and associated symptoms (though 40% of men and 48% of women present with atypical symptoms like isolated dyspnea) 3
• Clinical assessment including blood pressure, heart rate, cardiopulmonary auscultation, and Killip classification to identify hemodynamic instability 1

Based on these findings, assign patients to one of four categories: STEMI, NSTE-ACS with ongoing ischemia/hemodynamic instability, NSTE-ACS without ongoing ischemia, or ACS unlikely. 1

Immediate Pharmacological Treatment

Antiplatelet Therapy (Start Immediately)

• Aspirin 150-300 mg loading dose (non-enteric formulation), followed by 75-100 mg daily maintenance 1, 2
• P2Y12 inhibitor in addition to aspirin for dual antiplatelet therapy 1, 2
  • Ticagrelor is preferred (180 mg loading dose, 90 mg twice daily) for all patients at moderate-to-high risk, regardless of initial treatment strategy 1, 2
  • Prasugrel (60 mg loading, 10 mg daily) is recommended only AFTER coronary angiography in patients proceeding to PCI, NOT before anatomy is known 1, 4
  • Clopidogrel (300-600 mg loading, 75 mg daily) only if ticagrelor or prasugrel cannot be used 1

Critical pitfall: Do not administer prasugrel before coronary anatomy is established, as it is contraindicated in patients with prior stroke/TIA and increases bleeding risk in those requiring urgent CABG. 1, 4

Anticoagulation (Start Immediately)

Select ONE of the following based on bleeding risk and planned strategy:

• Fondaparinux 2.5 mg daily subcutaneously (preferred option with favorable bleeding profile) 1, 2
• Enoxaparin 1 mg/kg twice daily subcutaneously 1, 2
• Unfractionated heparin IV bolus 60-70 IU/kg (max 5000 IU) followed by 12-15 IU/kg/h infusion (max 1000 IU/h), titrated to aPTT 1.5-2.5 × control 1, 2
• Bivalirudin only in patients with planned invasive strategy 1, 2

Additional Immediate Therapies

• Beta-blockers if tachycardic or hypertensive WITHOUT signs of heart failure 1, 2
• Nitrates (sublingual or IV) for persistent chest pain 1
• High-intensity statin therapy started as early as possible 1, 2, 5

Urgent Laboratory Testing (Results Within 60 Minutes)

• High-sensitivity cardiac troponin at 0 hours and 1 hour (or 3 hours if 0/1 hour protocol unavailable) 1, 2
• Complete blood count (hemoglobin, hematocrit, platelets) 1
• Serum creatinine and estimated GFR 1
• Blood glucose 1
• INR if on warfarin 1
• Lipid profile once NSTE-ACS diagnosis confirmed 1

Risk Stratification and Timing of Invasive Strategy

Immediate Invasive Strategy (<2 Hours)

Proceed urgently if ANY of the following very-high-risk criteria present:

• Hemodynamic instability or cardiogenic shock 1, 2
• Recurrent or ongoing chest pain refractory to medical treatment 1, 2
• Life-threatening arrhythmias or cardiac arrest 1
• Mechanical complications of MI 1, 2
• Acute heart failure with refractory angina or ST deviation 1
• Recurrent dynamic ST- or T-wave changes, particularly with intermittent ST elevation 1, 2

Early Invasive Strategy (<24 Hours)

Proceed within 24 hours if ANY high-risk criteria:

• Rise or fall in cardiac troponin compatible with MI 1, 2
• Dynamic ST- or T-wave changes (symptomatic or silent) 1, 2
• GRACE score >140 1, 2

Invasive Strategy (<72 Hours)

Proceed within 72 hours if ANY intermediate-risk criteria:

• Diabetes mellitus 1, 2
• Renal insufficiency (eGFR <60 mL/min/1.73 m²) 1, 2
• LVEF <40% or congestive heart failure 1
• Early post-infarction angina 1
• Recent PCI or prior CABG 1
• GRACE score >109 and <140 1

Additional Supportive Measures

• Continuous cardiac monitoring for arrhythmia detection 1, 2
• Echocardiography to evaluate LV function and rule out differential diagnoses 1, 2
• Oxygen therapy only if hypoxemic 6
• Morphine for pain relief if nitrates insufficient 6
• Defibrillator patches placed in patients with ongoing ischemia until revascularization 1

Key pitfall: Avoid assigning "ACS unlikely" diagnosis prematurely, especially in elderly patients and those with diabetes who may present atypically. 1