What is the immediate emergency evaluation and treatment for a patient with acute coronary syndrome (ACS)?

Immediate Emergency Evaluation and Treatment for Acute Coronary Syndrome

Obtain a 12-lead ECG and interpret it within 10 minutes of first medical contact to identify STEMI, and immediately administer chewed aspirin 162-325 mg unless contraindicated. 1

First 10 Minutes: Critical Actions

ECG Acquisition and Interpretation

• Acquire and interpret a 12-lead ECG within 10 minutes of patient arrival or first medical contact by EMS personnel 1, 2
• If the initial ECG is nondiagnostic but clinical suspicion remains high, perform serial ECGs to detect evolving ischemic changes 1
• Prehospital ECG transmission to the receiving hospital while en route reduces time to reperfusion 1, 3

ECG-Based Triage Decision

The ECG determines your immediate treatment pathway:

STEMI criteria (requires immediate reperfusion):

• ST-segment elevation ≥1 mm (0.1 mV) in two contiguous leads 1
• For men ≥40 years: ≥2 mm in V2-V3, ≥1 mm in other leads 1
• For men <40 years: ≥2.5 mm in V2-V3, ≥1 mm in other leads 1
• For women: ≥1.5 mm in V2-V3, ≥1 mm in other leads 1
• New or presumed new left bundle branch block with clinical presentation consistent with ACS 3

NSTE-ACS criteria (requires risk stratification):

• ST-segment depression ≥0.5 mm 1
• Dynamic T-wave inversion with pain 1
• Transient ST-segment elevation <20 minutes 1

Nondiagnostic ECG (requires serial testing):

• Normal or minimal ST/T-wave changes 1
• Does not exclude ACS—proceed with serial troponins 2

Immediate Medical Therapy (Before Diagnostic Confirmation)

Aspirin:

• Administer 162-325 mg chewed, non-enteric-coated aspirin immediately unless active GI bleeding or documented allergy 1, 2, 3
• Do not delay aspirin while awaiting troponin results 3

Oxygen:

• Only administer if oxygen saturation <90% or respiratory distress 2, 4
• Routine oxygen in uncomplicated cases provides no benefit 2, 4

Monitoring:

• Establish continuous cardiac monitoring with defibrillation capability 1
• Establish IV access 2, 3
• Obtain vital signs including blood pressure in both arms to evaluate for aortic dissection 3

Blood Work

Draw immediately for:

• High-sensitivity cardiac troponin 2
• Complete blood count, basic metabolic panel (including creatinine), glucose, coagulation studies 2

STEMI Management Pathway

Do not delay reperfusion for additional diagnostic testing unless results would immediately alter management 2

Reperfusion Strategy

Primary PCI (preferred):

• Immediate EMS transport to PCI-capable hospital with system goal of first medical contact-to-device time ≤90 minutes 1, 3
• Early advance notification and activation of cardiac catheterization team by EMS reduces time to reperfusion 1, 3
• Primary PCI within 120 minutes reduces mortality from 9% to 7% 5

Fibrinolytic therapy (if PCI delayed >120 minutes):

• Administer weight-adjusted tenecteplase (preferred), alteplase, or reteplase 4, 5
• Half-dose for patients ≥75 years 4, 5
• Must be given with mandatory anticoagulation (enoxaparin preferred) 4
• Transfer for coronary angiography within 3-24 hours after successful fibrinolysis (pharmaco-invasive strategy) 4

NSTE-ACS Management Pathway

Serial Troponin Strategy

• Repeat high-sensitivity troponin 1-2 hours after initial draw (or 3-6 hours if using conventional assay) 2
• A rise or fall with at least one value above the 99th percentile confirms NSTEMI 1, 2
• Troponin results must be available within 60 minutes of blood draw to prevent treatment delays 2

Risk Stratification and Invasive Timing

Immediate invasive strategy (<2 hours) for:

• Refractory chest pain despite medical therapy 2, 4
• Hemodynamic instability or cardiogenic shock 2, 4
• Life-threatening arrhythmias (sustained VT/VF) 2, 4
• Mechanical complications (acute mitral regurgitation, ventricular septal defect) 2

Early invasive strategy (within 24-48 hours) for:

• Elevated troponin 2, 4
• Dynamic ECG changes 2, 3
• High-risk GRACE score 2
• Diabetes mellitus 2, 4
• Renal insufficiency 2
• Reduced left ventricular function 2
• Prior revascularization 2

Antithrombotic Regimen

Antiplatelet therapy:

• Aspirin 162-325 mg loading dose, then 75-100 mg daily indefinitely 3
• Add P2Y12 inhibitor (ticagrelor or prasugrel preferred over clopidogrel) 2, 4
• Clopidogrel 300 mg loading dose if <75 years; 75 mg if ≥75 years 4

Anticoagulation:

• Enoxaparin (preferred), fondaparinux, bivalirudin, or unfractionated heparin 2, 4
• Unfractionated heparin: 60 units/kg IV bolus (max 4000 units), then 12 units/kg/hour (max 1000 units/hour) adjusted to aPTT 1.5-2.5 times control 3

Additional Medical Therapy

Beta-blocker:

• Initiate unless contraindicated (heart failure, bradycardia, hypotension, severe reactive airway disease) 2, 4
• Target heart rate <60 bpm 4

Nitroglycerin:

• 0.4 mg sublingual every 5 minutes (up to 3 doses) for ongoing chest pain 1, 4
• IV nitroglycerin for persistent pain, targeting systolic BP 100-120 mmHg 4

Morphine:

• Reserve for severe, persistent chest pain unresponsive to nitroglycerin 2
• Delays absorption of oral antiplatelet agents 2, 4

Critical Pitfalls to Avoid

Atypical presentations are common:

• Women and elderly frequently present with dyspnea, nausea, or fatigue without chest pain 3
• Approximately 40% of men and 48% of women present with nonspecific symptoms 5
• Maintain high index of suspicion in these populations 1

ECG limitations:

• A normal ECG does not exclude ACS—serial troponins are mandatory 2
• ST-segment patterns do not reliably differentiate transmural from non-transmural ischemia 6
• Complete and incomplete occlusions can both cause STE or NSTE patterns 6

Medication errors:

• Do not withhold aspirin while waiting for troponin results 3
• Avoid NSAIDs—associated with increased mortality 3
• Do not give routine oxygen to uncomplicated patients 2, 4

Pre-Discharge Long-Term Management

Mandatory medications:

• High-intensity statin (atorvastatin 80 mg or rosuvastatin 40 mg) started immediately 2, 4
• ACE inhibitor (or ARB if intolerant) for LVEF ≤40%, heart failure, hypertension, or diabetes 2
• Beta-blocker continued for LVEF ≤40% 2
• Mineralocorticoid receptor antagonist (eplerenone) for LVEF ≤35% with heart failure or diabetes, if no significant renal dysfunction or hyperkalemia 2

Lifestyle interventions:

• Smoking cessation counseling 2
• Cardiac rehabilitation enrollment 2
• Dietary modification 2
• Target diastolic BP <90 mmHg (<85 mmHg with diabetes) 2