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

Initial Treatment for Acute Coronary Syndrome

All patients with suspected ACS should immediately receive aspirin 150-325 mg (non-enteric, chewable preferred), a P2Y12 inhibitor (ticagrelor 180 mg loading dose preferred, or clopidogrel 300 mg if ticagrelor unavailable), and parenteral anticoagulation, with a 12-lead ECG obtained within 10 minutes to guide the reperfusion strategy. 1, 2, 3

Immediate Assessment (Within 10 Minutes)

• Obtain a 12-lead ECG immediately to distinguish STEMI from non-ST-elevation ACS (NSTE-ACS), as this determines the reperfusion pathway 1, 2, 3
• Initiate continuous multi-lead ECG monitoring for arrhythmias and ongoing ischemia 1
• Assess hemodynamic stability including blood pressure, heart rate, signs of heart failure (S3 gallop, pulmonary rales), and peripheral perfusion 1, 2
• Draw blood for high-sensitivity cardiac troponin (results available within 60 minutes), with repeat measurement at 1-3 hours if high-sensitivity assay is used 1, 2
• Additional laboratory tests should include hemoglobin, creatinine, platelet count, and blood glucose 1

Antiplatelet Therapy

• Aspirin 162-325 mg loading dose (chewable formulation for faster absorption) should be given immediately unless true aspirin allergy exists 1, 2, 3
• Add a P2Y12 inhibitor for dual antiplatelet therapy (DAPT): ticagrelor 180 mg loading dose followed by 90 mg twice daily is preferred for moderate-to-high risk patients 1, 3
• If ticagrelor is unavailable or contraindicated, clopidogrel 300 mg loading dose followed by 75 mg daily is an acceptable alternative 1, 4, 5
• For patients with aspirin allergy, clopidogrel should be given as monotherapy 1, 6

Anticoagulation

Parenteral anticoagulation must be initiated immediately with one of the following options 1, 2, 3:

• Enoxaparin 1 mg/kg subcutaneously every 12 hours (preferred for NSTE-ACS not undergoing immediate invasive strategy) 1, 3
• Unfractionated heparin: 60 units/kg bolus (maximum 4000 units) followed by 12 units/kg/hour infusion targeting aPTT 1.5-2.0 times control 1, 3
• Fondaparinux 2.5 mg subcutaneously daily is an alternative for NSTE-ACS patients not undergoing immediate PCI, but should not be used to support PCI due to catheter thrombosis risk 1
• Bivalirudin may be used as an alternative to unfractionated heparin in STEMI patients undergoing PCI to reduce mortality and bleeding 1

Symptom Management

• Nitroglycerin for chest pain relief: sublingual 0.4 mg every 3-5 minutes (up to 3 doses), followed by IV nitroglycerin if pain persists 1, 2, 3
• Avoid nitroglycerin if systolic blood pressure is <90 mmHg 1
• Morphine 2-4 mg IV should be used for persistent severe chest pain unresponsive to nitrates, particularly in STEMI 3
• Oxygen therapy should only be administered if oxygen saturation is <90% or if respiratory distress is present; routine oxygen in normoxic patients is not recommended 1, 3

Beta-Blocker Therapy

• Beta-blockers should be initiated early in hemodynamically stable patients without contraindications 1, 3
• For STEMI patients, metoprolol can be given as three 5 mg IV boluses at 2-minute intervals, followed by oral metoprolol 50 mg every 6 hours starting 15 minutes after the last IV dose 7
• Contraindications include signs of heart failure, hypotension, bradycardia, or heart block 1, 7

Reperfusion Strategy Based on ECG Findings

For STEMI (Persistent ST-Segment Elevation):

• Primary PCI within 120 minutes is the preferred reperfusion strategy and reduces mortality from 9% to 7% 1, 8
• If PCI cannot be achieved within 120 minutes, fibrinolytic therapy (alteplase, reteplase, or tenecteplase) should be administered, followed by transfer for PCI within 24 hours 1, 8
• Parenteral anticoagulation should be continued for the duration of hospitalization (maximum 8 days) or until revascularization 1

For NSTE-ACS (No Persistent ST-Elevation):

Very high-risk patients (hemodynamic instability, cardiogenic shock, refractory chest pain, life-threatening arrhythmias, or mechanical complications) require immediate invasive strategy within 2 hours 1, 3

High-risk patients (elevated troponin, dynamic ST-segment changes, GRACE score >140) should undergo early invasive strategy within 24 hours, which reduces mortality from 6.5% to 4.9% 1, 2, 8

High-risk criteria include 1:

• Elevated troponin levels
• Recurrent or ongoing chest pain despite medical therapy
• Dynamic ST-segment depression or transient ST-segment elevation
• Hemodynamic instability developing during observation
• Major arrhythmias (ventricular tachycardia, ventricular fibrillation)

Additional Therapies

• High-intensity statin therapy should be initiated immediately, regardless of baseline lipid levels 3
• ACE inhibitors should be started in patients with LVEF ≤40%, heart failure, hypertension, or diabetes 3
• Calcium channel blockers may be used as an alternative to beta-blockers in patients with contraindications 1

Common Pitfalls

• Delaying P2Y12 inhibitor administration: While older guidelines suggested waiting for coronary anatomy definition before starting clopidogrel, current evidence supports immediate dual antiplatelet therapy in most patients 1, 2, 3
• Using fondaparinux to support PCI: This increases catheter thrombosis risk and is contraindicated 1
• Routine oxygen administration: Oxygen should only be given to hypoxemic patients, not routinely to all ACS patients 1, 3
• Administering nitroglycerin in hypotensive patients: This can worsen hemodynamic compromise 1
• Failing to adjust anticoagulation doses: Renal function and age must be considered when dosing antithrombotic agents 1