What initial laboratory tests are recommended for patients presenting with chest pain?

Initial Laboratory Tests for Patients Presenting with Chest Pain

For patients presenting with chest pain, initial laboratory tests should include serial cardiac troponin measurements (preferably high-sensitivity troponin) and a 12-lead ECG within 10 minutes of presentation, supplemented by a chest radiograph to evaluate for alternative causes of symptoms. 1

Core Initial Testing

Electrocardiogram (ECG)

• Obtain within 10 minutes of presentation 2
• Look for:
  • ST-segment elevation or depression
  • T-wave inversions
  • New left bundle branch block
  • Consider supplemental leads V7-V9 if posterior MI is suspected 2
• Serial ECGs should be performed if initial ECG is non-diagnostic, especially when clinical suspicion remains high 2

Cardiac Biomarkers

• High-sensitivity cardiac troponin (hs-cTn) is preferred over conventional troponin 2, 1
• Initial sample at presentation (time zero) with serial measurements:
  • High-sensitivity troponin: Repeat at 1-3 hours
  • Conventional troponin: Repeat at 3-6 hours 2, 1
• For patients with chest pain, normal ECG, and symptoms beginning ≥3 hours before arrival, a single hs-cTn below the limit of detection may reasonably exclude myocardial injury 2

Chest Radiograph

• Useful to evaluate for alternative cardiac, pulmonary, and thoracic causes of symptoms 2, 1
• Can help identify conditions such as pneumonia, pneumothorax, or aortic pathology

Risk Stratification Approach

The 2021 AHA/ACC guidelines recommend categorizing patients into risk strata to guide further testing and management 2:

Low-Risk Patients (<1% 30-day risk of death or MACE)

• May be discharged without admission or urgent cardiac testing if:
  • Normal ECG
  • Negative troponin values
  • No concerning features on history/examination 2

Intermediate-Risk Patients

• Transthoracic echocardiography is recommended to:
  • Establish baseline ventricular and valvular function
  • Evaluate for wall motion abnormalities
  • Assess for pericardial effusion 2
• Management in an observation unit is reasonable to shorten length of stay 2

High-Risk Patients

• Consider invasive coronary angiography 2

Additional Testing Considerations

• D-dimer testing may be considered if pulmonary embolism is suspected 1
• Previous cardiac testing results should be incorporated into clinical decision pathways when available 2

Common Pitfalls to Avoid

• Relying solely on a single troponin measurement instead of serial measurements 1
• Using outdated biomarkers such as CK-MB and myoglobin when troponin is available 1
• Misinterpreting troponin elevations, which can occur in numerous cardiac and non-cardiac conditions 1
• Delaying ECG acquisition beyond the recommended 10-minute window 2, 1
• For patients initially evaluated in office settings, delayed transfer to the ED for troponin or other diagnostic testing should be avoided 2

By following this evidence-based approach to laboratory testing for chest pain, clinicians can effectively risk-stratify patients and determine the appropriate level of care, ultimately improving morbidity and mortality outcomes.