Pulmonary Embolism


Pulmonary embolism (PE) is caused when a deep venous thrombosis from somewhere else in the body “embolizes” and becomes lodged in the pulmonary arteries

Can cause pulmonary infarction (which mimics pneumonia on chest x-ray)

Basic Approach to the Diagnosis of PE

  • Step 1: Consider PE in any patient with signs or symptoms consistent with the disease
    • Common signs/symptoms
      • Shortness of breath
      • Chest pain
      • Syncope
      • Tachycardia
      • Hypoxemia
      • Hypotension
  • Step 2: Do not do additional testing for PE in patients with a CLEAR alternative diagnosis
    • Common alternative diagnoses
      • COPD exacerbation
      • Acute coronary syndrome
      • Pneumonia
    • Keep in mind that these diagnoses are also the most frequent misdiagnoses in cases of missed PE!!! Be careful.
  • Step 3: Calculate Wells Score and PERC criteria
  • Step 4: Get a D-Dimer
    • IF…
    • Low risk Wells but fails PERC criteria
    • Medium risk Wells score
  • Step 5: Get a CTA
    • IF…
    • Wells score is high
    • Elevated d-dimer
      • (Update: it is now established that you can safely use AGE ADJUSTED D-DIMER)
        • ACEP’s clinical policy supporting this can be found HERE

Final Thoughts

  • Bilateral lower extremity ultrasounds not sensitive enough to rule out PE
  • The classic EKG finding is S1Q3T3

Additional Reading


  1. Otari Beldishevski-Shotadze

    Hi Zac, what do you do if the patient is pregnant and cant have CTPA or V/Q scan or if the patient cant have a CTPA and V/Q scan is inconclusive? also what is the evidence for placing IVC filters?

    • Zack

      Unsure about evidence for IVC filters. Generally speaking Ofer CTA as first line and VQ as second line. If VQ is inconclusive then you make judgement call on risk of PE vs risk of anticoagulation but that situation is rare

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