What are the recommended laboratory tests and diagnostics for a patient presenting with chest pain?

Recommended Laboratory Tests and Diagnostics for Chest Pain

For patients presenting with chest pain, immediately obtain an ECG within 10 minutes, measure cardiac troponin (preferably high-sensitivity troponin), and obtain a chest radiograph to evaluate for life-threatening cardiac, pulmonary, and thoracic causes. 1, 2

Initial Diagnostic Workup

Electrocardiogram (ECG)

• Obtain an ECG within 10 minutes of presentation to identify ST-segment elevation myocardial infarction (STEMI), which requires immediate reperfusion therapy 1
• If the initial ECG is nondiagnostic but clinical suspicion for acute coronary syndrome (ACS) remains high, perform serial ECGs to detect evolving ischemic changes 1
• For patients with intermediate-to-high clinical suspicion and nondiagnostic initial ECG, obtain supplemental leads V7-V9 to rule out posterior myocardial infarction 1
• If the ECG shows ST-elevation, treat immediately according to STEMI guidelines without waiting for troponin results 1

Cardiac Troponin Testing

High-sensitivity cardiac troponin (hs-cTn) is the preferred biomarker as it enables more rapid detection or exclusion of myocardial injury with superior diagnostic accuracy compared to conventional assays 2

Timing Protocols for Serial Troponin Measurements:

• For high-sensitivity troponin: Repeat at 1-3 hours after initial sample 1, 2
• For conventional troponin: Repeat at 3-6 hours after initial sample 1
• Single hs-cTn below limit of detection may reasonably exclude myocardial injury if symptoms began at least 3 hours before ED arrival 1, 2

Interpretation:

• Troponin levels greater than the 99th percentile upper reference limit indicate myocardial injury consistent with ACS 2, 3
• Look for rising or falling patterns in serial measurements, which are indicative of acute myocardial injury 2
• Institutions must implement a standardized protocol based on their specific troponin assay 1, 2

Chest Radiography

A chest radiograph is recommended (Class I indication) to evaluate for alternative cardiac, pulmonary, and thoracic causes including pneumonia, pneumothorax, aortic dissection, pleural effusion, and pulmonary edema 1, 2

Risk Stratification and Subsequent Testing

Clinical Decision Pathways

Categorize patients into low-, intermediate-, and high-risk strata using clinical decision pathways that incorporate age, ECG findings, symptoms, CAD risk factors, and troponin levels 1

High-Risk Patients:

• Proceed directly to invasive coronary angiography for patients with ongoing ischemia, hemodynamic instability, or high-risk features 1

Intermediate-Risk Patients:

• Obtain transthoracic echocardiography (TTE) as a rapid bedside test to assess ventricular function, wall motion abnormalities, valvular function, and pericardial effusion 1
• Consider anatomic testing (coronary CT angiography) or functional testing (stress testing) based on patient characteristics 1
• Management in an observation unit is reasonable to shorten length of stay 1

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

• Discharge home without admission or urgent cardiac testing is reasonable after appropriate troponin evaluation 1, 2
• Optional outpatient testing may include ECG or coronary artery calcium (CAC) scan 1

Additional Laboratory Tests

What NOT to Order:

Do not order CK-MB or myoglobin as these biomarkers are not useful for diagnosis of acute myocardial injury when cardiac troponin is available 2

Additional Testing for Non-Cardiac Causes:

• Complete blood count, basic metabolic panel to assess for anemia, electrolyte abnormalities, and renal function 1
• D-dimer and CT pulmonary angiography if pulmonary embolism is suspected 1
• CT angiography of the chest if aortic dissection is suspected 1
• Arterial blood gas if respiratory compromise is present 1

Critical Pitfalls to Avoid

• Never delay transfer to the ED for troponin testing in office-based patients with suspected ACS 2
• Do not rely on a single troponin when clinical suspicion is high—serial measurements are essential 1, 2
• Be aware that 2-5% of ACS patients are inappropriately discharged from the ED, often due to atypical presentations 3
• Incorporate previous testing results when available into clinical decision-making 1, 2
• Recognize that normal ECG and initial troponin do not exclude ACS—risk stratification and serial testing are required 3