Pulmonary Embolism Low Probability Evaluation

1. See Also
   1. Pulmonary Embolism
   2. Pulmonary Embolism Diagnosis
   3. Pulmonary Embolism Moderate Probability Evaluation
   4. Pulmonary Embolism High Probability Evaluation
2. Technique
   1. Based on PE Probability (See PE Diagnosis)
   2. Consider Alternative Diagnosis
      1. See Chest Pain Causes
      2. See Dyspnea Causes
      3. See Leg Pain Causes
3. 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 Doppler Ultrasound Positive for DVT
         1. Treat with Pulmonary Embolism Management
      2. Lower Extremity Doppler Ultrasound Negative for DVT
         1. Move to step 2 below
4. Step 2: Obtain D-Dimer (or consider jumping to step 3)
   1. D-Dimer suggestive for PE (Positive >400)
      1. 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
      3. No further evaluation needed
      4. Evaluate for alternative diagnosis
5. Step 3: Imaging Study
   1. Ventilation Perfusion Scan (V/Q Scan)
      1. Normal Probability V/Q Scan
         1. No further evaluation needed
         2. Evaluate for alternative diagnosis
      2. Low or Intermediate Probability VQ Scan
         1. Jump to Step 4 below
      3. High Probability V/Q Scan
         1. Jump to Step 5 below
   2. CT Pulmonary Angiogram (Spiral or helical chest CT)
      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
6. 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
7. 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
8. References
   1. Ramzi (2004) Am Fam Physician 69:2829-36
   2. Wells (1998) Ann Intern Med 129(12): 997-1005