What is the recommended emergency evaluation and initial management for a patient with suspected acute coronary syndrome?

Emergency Evaluation and Initial Management of Acute Coronary Syndrome

For patients with suspected ACS, immediately obtain a 12-lead ECG within 10 minutes of first medical contact, administer chewed aspirin 160-325 mg (unless contraindicated), and activate emergency transport to a PCI-capable facility—these three actions form the cornerstone of initial management and directly impact mortality. 1, 2

Immediate Prehospital Actions (First 10 Minutes)

ECG Acquisition and Interpretation

• Obtain and interpret a 12-lead ECG within 10 minutes of first medical contact to differentiate STEMI from non-ST-elevation ACS, as this determines the entire treatment pathway 1, 2
• Paramedics and nurses can independently identify STEMI on ECG when trained with mandatory ongoing oversight—this speeds diagnosis without compromising accuracy 1
• Transmit the ECG to the receiving hospital for advance notification if STEMI is identified, which reduces time to reperfusion 1, 2

Aspirin Administration

• Administer non-enteric aspirin 160-325 mg immediately (chewed, not swallowed) unless the patient has known aspirin allergy or active gastrointestinal bleeding 1
• EMS dispatchers should instruct patients to chew aspirin while awaiting EMS arrival—early aspirin reduces mortality regardless of final diagnosis 1, 2
• Do not delay aspirin administration while waiting for troponin results or physician evaluation 2

Oxygen Therapy (Selective Use Only)

• Administer oxygen only if oxygen saturation <94%, signs of heart failure, shock, or breathlessness are present—routine oxygen in uncomplicated ACS lacks evidence of benefit 1
• Use noninvasive pulse oximetry monitoring to guide oxygen therapy decisions 1

Initial Assessment Components

History and Physical Examination

• Focus on chest pain characteristics: duration >20 minutes at rest is high-risk and mandates emergency evaluation 3
• Assess for valvular heart disease (aortic stenosis), hypertrophic cardiomyopathy, heart failure, and pulmonary disease as alternative diagnoses 1
• Obtain vital signs including blood pressure in both arms to evaluate for aortic dissection 2
• Critical pitfall: Women and elderly patients frequently present with atypical symptoms (dyspnea, nausea, fatigue) without chest pain—maintain high suspicion 2, 3

ECG Interpretation for Risk Stratification

• ST-segment elevation ≥1 mm in ≥2 contiguous leads = STEMI requiring immediate reperfusion within 90 minutes of first medical contact 2
• New or presumed new left bundle branch block with consistent clinical presentation = STEMI equivalent 2
• ST-segment depression, T-wave inversions, or normal ECG = non-ST-elevation ACS requiring further risk stratification 1
• Repeat ECG if patient experiences recurrent chest pain during observation 1

Laboratory Assessment

• Draw cardiac troponin (preferably high-sensitivity troponin) on arrival and repeat at 6-12 hours 1
• Elevated troponin (particularly >0.01 ng/mL) identifies high-risk patients requiring early invasive strategy 2
• Check hemoglobin to detect anemia as a precipitating factor 1

Pharmacologic Management

Antiplatelet Therapy

• Aspirin 162-325 mg loading dose, then 75-100 mg daily indefinitely for all ACS patients 2, 4
• Add P2Y12 inhibitor (clopidogrel, ticagrelor, or prasugrel) at time of diagnosis for high-risk patients 2, 4
• For STEMI patients going to PCI, prasugrel 60 mg oral loading dose may substitute for clopidogrel 1

Anticoagulation

• Initiate parenteral anticoagulation with unfractionated heparin (60 units/kg IV bolus, maximum 4000 units, then 12 units/kg/hour infusion adjusted to aPTT 1.5-2.5 times control) 2, 4
• Alternative options include low-molecular-weight heparin, bivalirudin, or fondaparinux 4

Nitroglycerin for Symptom Relief

• Administer up to 3 doses of sublingual or aerosol nitroglycerin at 3-5 minute intervals for ongoing chest discomfort 1
• Absolute contraindications: systolic blood pressure <90 mmHg or ≥30 mmHg below baseline, right ventricular infarction, use of PDE-5 inhibitors within 24 hours (48 hours for tadalafil) 1
• Exercise extreme caution in inferior wall STEMI—obtain right-sided ECG to evaluate for RV involvement before giving nitrates 1

Analgesia

• Morphine is indicated when chest discomfort is unresponsive to nitrates in STEMI (2-4 mg IV, may repeat) 1
• Use morphine with caution in unstable angina/NSTEMI due to association with increased mortality in registry data 1

Risk Stratification for Non-ST-Elevation ACS

High-Risk Features Requiring Early Invasive Strategy (Angiography Within 24-48 Hours)

• Recurrent ischemia (chest pain or dynamic ST-segment changes) despite medical therapy 1
• Elevated cardiac troponin levels 1, 2
• Hemodynamic instability or signs of heart failure 1
• Sustained ventricular tachycardia or ventricular fibrillation 1
• Early post-infarction unstable angina 1

Low-Risk Patients

• Normal troponin measured twice (at presentation and 6-12 hours later) with non-ischemic ECG may undergo noninvasive testing (stress test, CT angiography, cardiac MRI, or myocardial perfusion imaging) 1
• These patients can potentially be safely discharged from the ED after negative testing 1

STEMI-Specific Reperfusion Strategy

Primary PCI (Preferred Method)

• Transport directly to PCI-capable hospital with system goal of first medical contact-to-device time ≤90 minutes 2
• Activate catheterization laboratory immediately upon STEMI diagnosis—advance notification reduces door-to-balloon time 1, 2
• Primary PCI reduces mortality from 9% to 7% compared to no reperfusion 2

Fibrinolytic Therapy (When PCI Delayed)

• Administer fibrinolytic therapy if PCI will be delayed >120 minutes from first medical contact 4
• Fibrinolytic therapy is typically not recommended for non-ST-elevation ACS 4

Critical Pitfalls to Avoid

• Never administer NSAIDs—they are associated with increased mortality, reinfarction, hypertension, heart failure, and myocardial rupture in ACS patients 1, 2
• Do not use inpatient-derived risk scoring systems to identify patients safe for ED discharge—they are useful for prognosis but not for discharge decisions 1
• Avoid consultation delays that postpone reperfusion therapy—these delays increase mortality 3
• Do not withhold treatment based on atypical presentations—half of ACS deaths occur before hospital arrival, often in patients with non-classic symptoms 1
• Balance bleeding risk against antithrombotic benefit, particularly in elderly patients or those with renal impairment 3

Monitoring and Observation Period

• Establish continuous cardiac monitoring and be prepared for CPR/defibrillation 1
• Multi-lead ECG ischemia monitoring is recommended during the observation period 1
• Repeat troponin measurement after 6-12 hours if initial value is normal 1
• Obtain echocardiogram to assess left ventricular function and eliminate other cardiovascular causes of chest pain 1