What is the initial workup and lab testing for a patient presenting with atypical chest pain in an outpatient primary care office?

Initial Workup and Lab Testing for Atypical Chest Pain in Primary Care

For patients presenting with atypical chest pain in an outpatient primary care setting, a 12-lead ECG should be performed within 10 minutes of presentation, cardiac troponin should be measured (preferably using high-sensitivity assays), and a chest radiograph should be obtained to evaluate for cardiac and non-cardiac causes. 1, 2

Immediate Assessment

History and Physical Examination Focus

• Characterize the pain:

  • Onset, location, radiation, quality, duration, aggravating/alleviating factors
  • Red flags: diaphoresis, radiation to arm/jaw, associated dyspnea, nausea/vomiting
  • Risk factors for coronary artery disease

• Physical examination targets:

  • Vital signs (tachycardia, hypotension, tachypnea)
  • Cardiovascular exam: murmurs, S3, crackles, pulse differentials
  • Chest wall tenderness (suggests musculoskeletal cause)
  • Respiratory examination: decreased breath sounds, wheezing, rales

Initial Diagnostic Testing

1. 12-lead ECG - Must be performed within 10 minutes of presentation 1, 2

   • Look for: ST-segment changes, T-wave inversions, Q waves, new LBBB
   • Compare with previous ECGs if available
   • Consider serial ECGs if initial is non-diagnostic but suspicion remains high

2. Cardiac Biomarkers 1, 2

   • High-sensitivity cardiac troponin (hs-cTn) preferred
   • If initial troponin is non-diagnostic:
     • Repeat in 1-2 hours if using hs-cTn
     • Repeat in 3-6 hours if using conventional troponin

3. Chest Radiography 2

   • Should be performed within 30 minutes of arrival
   • Evaluates for alternative cardiac, pulmonary, and thoracic causes

Risk Stratification

Clinical Decision Tools

• HEART Score components: 2

  • History (suspicious vs. non-suspicious)
  • ECG abnormalities
  • Age
  • Risk factors
  • Troponin level

• TIMI Risk Score for unstable angina/NSTEMI 1, 2

Risk-Based Management Algorithm

High-Risk Features (Require Immediate Hospital Referral):

• Abnormal ECG (ST changes, new LBBB, T-wave inversions)
• Elevated troponin
• Hemodynamic instability
• Recurrent or ongoing pain despite initial treatment
• High-risk score on validated risk tool

Intermediate-Risk Features:

• Normal ECG but concerning symptoms
• Multiple risk factors for CAD
• Age >65 years
• Prior history of CAD

Low-Risk Features:

• Non-exertional pain
• Pain reproducible with palpation
• Brief duration of symptoms
• Normal vital signs, ECG, and biomarkers
• Low risk score on validated tool

Initial Treatment in Primary Care

1. Aspirin - 160-325 mg (chewed) unless contraindicated 2
2. Sublingual nitroglycerin - For ongoing pain
3. Oxygen - Only if oxygen saturation <90% or respiratory distress 2
4. IV access - Establish in patients with concerning symptoms

Common Pitfalls to Avoid

1. Relying solely on ECG - Up to 6% of ACS patients may have normal ECGs 2
2. Inappropriate troponin testing - Should not delay referral if ACS is suspected 3
3. Overlooking non-cardiac causes - Consider pulmonary embolism, pneumothorax, aortic dissection
4. Dismissing atypical presentations - Especially in elderly, women, and diabetic patients
5. Failing to use risk stratification tools - These improve diagnostic accuracy

Disposition Decision-Making

• High-risk patients: Immediate emergency department referral
• Intermediate-risk patients: Consider observation or referral based on clinical judgment
• Low-risk patients: May consider outpatient follow-up with scheduled stress testing

The 2025 ACC/AHA/ACEP/NAEMSP/SCAI guidelines emphasize that rapid assessment and diagnosis are critical for improving outcomes in patients with suspected ACS 1. While most patients with atypical chest pain will not have ACS, missing this diagnosis has significant implications for morbidity and mortality.

For patients determined to be at low risk after initial evaluation, further outpatient testing may include exercise stress testing, coronary CT angiography, or cardiac MRI based on the specific clinical scenario 4.

Remember that in the primary care setting, the focus should be on rapid assessment, risk stratification, and appropriate referral rather than definitive diagnosis of ACS.