What tests should be ordered for a patient presenting with chest pain, particularly if the electrocardiogram (EKG) is abnormal?

Diagnostic Approach for Patients with Chest Pain

For patients presenting with chest pain, an ECG should be performed within 10 minutes of arrival, followed by cardiac troponin measurement, with additional testing based on risk stratification and initial findings. 1

Initial Assessment (First 10 Minutes)

• ECG: Must be obtained and interpreted within 10 minutes of arrival in any setting 1

  • If unavailable in office setting, immediate transfer to ED via EMS is recommended
  • Look for:
    • ST-segment elevation (STEMI)
    • ST-segment depression
    • T-wave inversions
    • New left bundle branch block
    • Arrhythmias

• Immediate action based on ECG findings:

  • STEMI → Follow STEMI guidelines
  • ST-depression/T-wave inversions → Follow NSTE-ACS guidelines
  • Diffuse ST elevation → Consider pericarditis
  • Normal or nondiagnostic ECG → Continue evaluation (does NOT rule out ACS)

Laboratory Testing

• Cardiac biomarkers:

  • High-sensitivity cardiac troponin (preferred) 1
  • Serial measurements (0,1-2 hours for high-sensitivity assays; 0,3-6 hours for conventional assays)
  • Rising/falling pattern indicates acute myocardial injury

• Avoid outdated markers: CK-MB and myoglobin are not useful for diagnosis of acute myocardial injury 1

Imaging

• Chest radiography: Useful to evaluate for alternative cardiac, pulmonary, and thoracic causes 1
  • Can identify pneumonia, pneumothorax, pulmonary edema, widened mediastinum

Risk Stratification and Further Testing

• Low-risk patients (normal ECG, negative troponins, no concerning symptoms):

  • May be considered for outpatient evaluation 2
  • Consider stress testing if appropriate

• Intermediate-risk patients (nonspecific ECG changes, negative troponins):

  • Serial ECGs if symptoms persist or change 1
  • Consider supplemental ECG leads V7-V9 if posterior MI suspected 1
  • Consider observation unit admission

• High-risk patients (abnormal ECG with ischemic changes, positive troponins):

  • Admit for further management
  • Treat according to ACS guidelines

Important Considerations for Stress Testing

If planning a stress echo and the baseline ECG is abnormal, DO NOT perform an exercise stress test. Instead:

• Pharmacologic stress testing (adenosine or dipyridamole) should be used in patients with:

  • Left bundle branch block
  • Electronically paced ventricular rhythm
  • Baseline ECG abnormalities that interfere with interpretation of exercise-induced ST changes 1

• Exercise stress testing is contraindicated when:

  • Active ischemia is present (ST elevation/depression, ongoing chest pain)
  • Unstable hemodynamics
  • Severe aortic stenosis
  • Acute myocarditis/pericarditis

Pitfalls to Avoid

• Do not rely solely on a single normal ECG to rule out ACS - up to 6% of patients with evolving ACS are discharged with a normal ECG 1, 3

• Do not delay transfer to the hospital for determination of cardiac troponin or other diagnostic testing beyond the ECG in the office setting 1

• Do not perform exercise stress testing when the baseline ECG has abnormalities that would make interpretation difficult 1

• Do not underestimate risk in specific populations with atypical presentations:

  • Women (more likely to have nausea, shortness of breath)
  • Elderly (may present with shortness of breath, syncope, delirium)
  • Diabetics (may have minimal symptoms)

Remember that the combination of ECG and troponin is superior to either alone for risk stratification 4, and patients with chest pain and abnormal ECGs showing ischemic changes have significantly higher rates of myocardial infarction (54.2%) compared to those with normal ECGs (1.3%) 2.