What is the initial management for a patient presenting with acute coronary syndrome (ACS)?

Initial Management of Acute Coronary Syndrome

All patients presenting with suspected ACS require immediate ECG within 10 minutes, aspirin 150-325 mg loading dose, and high-sensitivity cardiac troponin measurement, followed by risk-stratified invasive strategy and dual antiplatelet therapy. 1, 2

Immediate Assessment (First 10 Minutes)

Diagnostic Workup

• Obtain 12-lead ECG within 10 minutes of presentation to differentiate STEMI from NSTE-ACS 1, 2
• Draw high-sensitivity cardiac troponin at presentation (0 hours) with results available within 60 minutes 1, 2
• Repeat troponin at 1-2 hours for high-sensitivity assays or 3-6 hours for conventional assays 1
• Initiate continuous cardiac rhythm monitoring to detect arrhythmias and dynamic ST-segment changes 1, 2
• Assess vital signs focusing on hemodynamic stability (blood pressure, heart rate), signs of heart failure (Killip classification), and cardiopulmonary auscultation 1, 2
• Obtain blood work including serum creatinine, hemoglobin, hematocrit, platelet count, blood glucose, and INR if on anticoagulation 1

Immediate Pharmacological Therapy

• Administer aspirin 150-325 mg loading dose (chewed for faster absorption) immediately unless contraindicated 1, 2, 3
• Give sublingual or intravenous nitroglycerin for ongoing chest pain 1, 2, 3
• Administer morphine 4-8 mg IV if pain persists despite nitroglycerin, with additional 2 mg doses every 5-15 minutes as needed 3
• Provide supplemental oxygen only if oxygen saturation is <90% or respiratory distress is present 3
• Initiate parenteral anticoagulation with low molecular weight heparin or unfractionated heparin 1, 2

Risk Stratification and Invasive Strategy Timing

The timing of coronary angiography is critical and directly impacts mortality. The 2025 ACC/AHA guidelines and 2015 ESC guidelines provide clear risk-based algorithms 1:

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

Proceed immediately to catheterization if ANY of the following are present 1, 2:

• Hemodynamic instability or cardiogenic shock
• Recurrent or 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- or T-wave changes, particularly with intermittent ST elevation

High-Risk: Early Invasive Strategy (<24 hours)

Proceed to catheterization within 24 hours if ANY of the following are present 1, 2:

• 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)

Proceed to catheterization within 72 hours if ANY of the following are present 1:

• 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 and <140, or recurrent symptoms

Dual Antiplatelet Therapy

A P2Y12 inhibitor must be added to aspirin for 12 months unless excessive bleeding risk exists. 1, 2

P2Y12 Inhibitor Selection (in order of preference):

Ticagrelor is the preferred agent for moderate to high-risk patients 1:

• Loading dose: 180 mg
• Maintenance: 90 mg twice daily
• Recommended for all patients with elevated cardiac troponins regardless of initial treatment strategy 1
• Can be given to patients pretreated with clopidogrel (discontinue clopidogrel when starting ticagrelor) 1

Prasugrel is recommended for patients proceeding to PCI without contraindications 1, 4:

• Loading dose: 60 mg
• Maintenance: 10 mg daily
• Critical timing consideration: In NSTE-ACS, do not administer loading dose until coronary anatomy is established to avoid excessive bleeding if urgent CABG is needed 4
• Reduce maintenance dose to 5 mg daily in patients <60 kg 4
• Contraindicated in patients with prior TIA or stroke due to increased ICH risk (6.5% vs 1.2% with clopidogrel) 4
• Generally not recommended in patients ≥75 years except in high-risk situations (diabetes or prior MI) 4

Clopidogrel is reserved for patients who cannot receive ticagrelor or prasugrel 1:

• Loading dose: 300-600 mg
• Maintenance: 75 mg daily
• Use in patients requiring oral anticoagulation 1

Additional Medical Therapy

• Initiate beta-blockers orally or IV unless contraindicated (hypotension, bradycardia, acute heart failure) 2, 3
• Consider calcium channel blockers for patients with contraindications to beta-blockers 2
• Start high-intensity statin therapy as early as possible 2
• Continue anticoagulation until revascularization or hospital discharge 2

Adjunctive Diagnostic Testing

• Perform echocardiography to evaluate regional and global left ventricular function and exclude differential diagnoses 1, 2
• Urgent echocardiography (including point-of-care ultrasound) is indicated for cardiogenic shock, hemodynamic instability, or suspected mechanical complications 1
• Place defibrillator patches in patients with ongoing ischemia until urgent revascularization is performed 1

Critical Pitfalls to Avoid

ECG timing: Delaying ECG beyond 10 minutes leads to missed diagnosis and delayed treatment, particularly in STEMI where every minute to reperfusion affects mortality 1, 2, 3

Troponin interpretation: Do not wait for troponin results before initiating antiplatelet therapy in high-risk patients with dynamic ECG changes or clinical deterioration 2, 3

Atypical presentations: Women, elderly, and diabetic patients frequently present without chest pain (up to 48% of women), instead presenting with dyspnea, nausea, or fatigue alone 5, 6

Baseline ECG abnormalities: Patients with baseline ST depression require comparison to prior tracings to detect dynamic changes; stable vitals can be falsely reassuring as up to 6% of evolving ACS patients present with normal initial findings 3

Prasugrel timing in NSTE-ACS: Administering prasugrel before coronary anatomy is known substantially increases bleeding risk if urgent CABG is required; wait until anatomy is established 4

Premature discontinuation: Stopping P2Y12 inhibitors, particularly in the first few weeks after ACS, significantly increases the risk of subsequent cardiovascular events 4