Pulmonary Embolism Low Probability Evaluation

Aka: Pulmonary Embolism Low Probability Evaluation, PE Low Probability Evaluation, Low PE Probability, Low Clinical Suspicion for Pulmonary Embolism

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II. Indications

  1. Low Clinical Suspicion for Pulmonary Embolism or
  2. Wells Clinical Prediction Rule for PE Score 4 or less

III. Technique

  1. Based on PE Probability (See PE Diagnosis)
    1. See Pulmonary Embolism Pretest Probability
    2. See Pulmonary Embolism Rule-Out Criteria (PERC Rule)
  2. Consider Alternative Diagnosis
    1. See Chest Pain Causes
    2. See Dyspnea Causes
    3. See Leg Pain Causes
    4. See Tachypnea
    5. See Hypoxia
    6. See Sinus Tachycardia

IV. Approach: Shared Decision Making

  1. Indications
    1. Dyspnea or Chest Pain as presenting complaint AND
    2. Pulmonary Embolism Low Probability Evaluation AND
    3. D-Dimer 0.5 to 1.0 mg/ml
  2. Rationale
    1. Risk of deferred CT pulmonary angiogram (CTPA)
      1. Missed Pulmonary Embolism: 0.8% risk
      2. Other missed diagnosis which would otherwise be identified on CT
    2. Risk of CT pulmonary angiogram (CTPA)
      1. Acute Kidney Injury: 10% risk
        1. See Intravenous Contrast Related Acute Renal Failure
      2. Future malignancy: 0.03%
        1. See Cancer Risk due to Diagnostic Radiology
  3. Protocol
    1. Risks and benefits of CTPA discussed
    2. Patient decides whether to pursue CTPA
  4. References
    1. Arora and Menchine in Herbert (2014) EM:Rap 14(7): 8
    2. Gever (2014) Am J Emerg Med 32(3): 233-6 [PubMed]

V. Evaluation: Step 0- Determine if Pulmonary Embolism should be considered

  1. Three starting questions - Dyspnea? Tachypnea? Pleuritic Chest Pain?
    1. All three symptoms absent nearly excludes Pulmonary Embolism
  2. Pulmonary Embolism Pretest Probability (Wells Clinical Prediction Rule for PE)
    1. Indicated if Dyspnea, Tachypnea or Pleuritic Chest Pain is present
    2. Quantifies pretest probability of Pulmonary Embolism
    3. Moderate or High probability (>10% likelihood) requires diagnostic testing (typically CT angiogram)
    4. Low pretest probability may be evaluated with PERC Rule
  3. Pulmonary Embolism Rule-Out Criteria (PERC Rule)
    1. Indicated if low probability for Pulmonary Embolism (up to 10% likelihood)
    2. Strong Negative Predictive Value (if all criteria are negative)
    3. Low probability for PE with a negative PERC Rule nearly excludes Pulmonary Embolism
    4. Low probability for PE with any PERC Rule criteria positive should be pursued with additional testing (e.g. D-Dimer)

VI. Evaluation: Step 1 - Determine if Deep Vein Thrombosis Present

  1. No Signs and Symptoms of DVT
    1. Jump to step 2 below
  2. Signs and Symptoms of DVT
    1. Lower Extremity DopplerUltrasound Positive for DVT
      1. Treat with Pulmonary Embolism Management
    2. Lower Extremity DopplerUltrasound Negative for DVT
      1. Move to step 2 below

VII. Evaluation: Step 2 - Obtain D-Dimer (or jump to step 3 if Intermediate PE Probability)

  1. D-Dimer suggestive for PE (Positive >0.5)
    1. Considering increasing D-Dimer threshold to double of discriminatory value (e.g. 1.0)
    2. Jump to Step 3 below
  2. D-Dimer not suggestive for PE (Negative)
    1. Negative Predictive Value 99.5% if Low PE Probability
    2. Reference
      1. Wells (2001) Ann Intern Med 135:98-107 [PubMed]
    3. No further evaluation needed
    4. Evaluate for alternative diagnosis

VIII. Evaluation: Step 3 - Imaging Study

  1. CT Pulmonary Angiogram (Spiral or helical chest CT, preferred)
    1. Spiral Chest CT suggestive for PE (Positive)
      1. Treat with Pulmonary Embolism Management
    2. Spiral Chest CT not suggestive for PE (Negative)
      1. Jump to step 4 below
  2. Ventilation Perfusion Scan (V/Q Scan)
    1. Indicated when CT angiography not available or contraindicated
    2. Normal Probability V/Q Scan
      1. No further evaluation needed
      2. Evaluate for alternative diagnosis
    3. Low or Intermediate Probability VQ Scan
      1. Jump to Step 4 below
    4. High Probability V/Q Scan (despite Low PE Probability)
      1. Jump to Step 5 below

IX. Evaluation: Step 4 - Obtain Lower Extremity Compression Ultrasound

  1. Negative Compression Ultrasound
    1. Evaluate for alternative diagnosis
  2. Positive Compression Ultrasound
    1. Treat with Pulmonary Embolism Management

X. Evaluation: Step 5 - Obtain pulmonary angiogram

  1. Pulmonary angiogram suggestive for PE (Positive)
    1. Treat with Pulmonary Embolism Management
  2. Pulmonary angiogram not suggestive for PE (Negative)
    1. No further evaluation needed
    2. Evaluate for alternative diagnosis

XI. References

  1. Tabas in Majoewsky (2013) EM:Rap 13(6):8-10
  2. Ramzi (2004) Am Fam Physician 69:2829-36 [PubMed]
  3. Wells (1998) Ann Intern Med 129(12): 997-1005 [PubMed]
  4. Wilbur (2012) Am Fam Physician 86(10):913-9 [PubMed]

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