What is the workup for acute pulmonary embolism (PE)?

Diagnostic Workup for Acute Pulmonary Embolism

The diagnostic workup for acute pulmonary embolism (PE) should follow a structured algorithm based on clinical probability assessment, D-dimer testing, and appropriate imaging studies, with CT pulmonary angiography (CTPA) being the first-line imaging test for suspected PE in hemodynamically stable patients. 1, 2

Initial Assessment and Risk Stratification

Clinical Probability Assessment

• Use validated clinical prediction rules to classify PE probability:
  • Low, intermediate, or high probability based on clinical factors 2
  • Wells score or Geneva score can be used to standardize assessment
  • Consider PE when presenting with dyspnea (80% of cases), chest pain (52%), tachypnea, tachycardia, syncope, or hemoptysis 2

Hemodynamic Status Evaluation

• Immediately identify patients with shock or hypotension (high-risk PE):
  • Systolic BP <90 mmHg or drop ≥40 mmHg for >15 min not caused by arrhythmia, hypovolemia, or sepsis 1
  • These patients require immediate bedside echocardiography 1, 2

Diagnostic Algorithm for Suspected PE

For Hemodynamically Stable Patients (Normal BP):

1. Assess clinical probability and measure D-dimer:

   • If D-dimer negative AND clinical probability low → PE excluded 2
   • If D-dimer positive OR clinical probability moderate/high → proceed to imaging 2

2. First-line imaging:

   • CTPA (sensitivity 83%, specificity 96%) 2
   • If CTPA positive → PE confirmed
   • If CTPA negative → PE excluded

3. Alternative imaging (if CTPA contraindicated):

   • V/Q scan (especially with normal chest X-ray) 2
   • Compression ultrasound of lower limbs (sensitivity >90%, specificity ~95%) 1, 2
     • Finding proximal DVT is sufficient to warrant anticoagulation without further testing 2

For Hemodynamically Unstable Patients (Shock/Hypotension):

1. Immediate bedside transthoracic echocardiography:

   • Evidence of RV dysfunction is sufficient to prompt immediate reperfusion without further testing if clinical suspicion is high 1, 2
   • Can also help identify alternative diagnoses (tamponade, acute valvular dysfunction, aortic dissection) 1

2. If available without delay, proceed to CTPA for definitive diagnosis 1

Additional Diagnostic Tests

Laboratory Tests

• D-dimer: Essential for ruling out PE in low probability cases 2

  • Use age-adjusted cutoffs for patients >50 years (age × 10 μg/L) 2
  • Negative D-dimer safely excludes PE in appropriate clinical context

• Cardiac biomarkers: For risk stratification, not diagnosis 1

  • Troponin
  • NT-proBNP/BNP
  • H-FABP

Imaging Beyond Initial Diagnosis

• Echocardiography: To assess RV function and guide treatment decisions 1, 2

  • Not recommended as part of routine diagnostic workup in hemodynamically stable patients 1
  • Essential in suspected high-risk PE 2

• Lower limb compression ultrasound: Alternative when lung imaging unavailable 2

  • DVT is found in 30-50% of patients with PE 2

Common Pitfalls and Caveats

1. Overreliance on D-dimer in high probability cases:

   • D-dimer has high sensitivity but poor specificity
   • Proceed directly to imaging in high clinical probability regardless of D-dimer 2

2. Misinterpretation of clinical signs:

   • Most patients with PE are breathless and/or tachypneic
   • Absence of these symptoms with pleurisy or hemoptysis usually indicates another cause 2

3. Inadequate risk stratification:

   • Failure to identify high-risk patients requiring immediate intervention
   • Use of PESI or sPESI scores helps identify low-risk patients 1

4. Incidental PE findings:

   • Incidentally discovered PE should receive the same anticoagulation therapy as symptomatic PE 2
   • Assess for proximal DVT with bilateral leg ultrasound in patients with incidental PE 2

5. Pregnancy considerations:

   • Modified diagnostic approach needed
   • Measure D-dimer and use clinical prediction rules 2
   • Consider radiation exposure risks with imaging

Post-Diagnosis Assessment

After confirming PE diagnosis, perform risk stratification for early mortality:

• High risk: Shock or hypotension present 1
• Intermediate risk: RV dysfunction and/or myocardial injury markers positive 1
• Low risk: No RV dysfunction or myocardial injury markers 1

This risk stratification guides treatment decisions, including the need for thrombolysis, hospitalization vs. outpatient management, and intensity of monitoring.

By following this structured diagnostic approach, clinicians can efficiently diagnose PE while minimizing unnecessary testing and treatment delays, ultimately reducing PE-related morbidity and mortality.