• Pulmonary embolism (PE) is a major cause of morbidity and mortality worldwide and requires timely diagnosis and treatment.
  • In Canada, the incidence rate of PE is 0.38 per 1000 person years
  • Higher risk patients include those with active cancer, age >80, pregnancy, trauma, recent surgery, immobility, genetic predisposition or past VTE
  • Up to 50% are unprovoked²
• The clinical starting point for the diagnosis of PE in suspected patients is to estimate the likelihood based on clinical features. Presentations are variable so keeping suspicion initially high is important.
• The most common presenting complaints of patients with PE are dyspnea and pleuritic chest pain. Other clinical findings may include: cough, substernal chest pain, fever, hemoptysis, syncope, signs of DVT.⁴
• Diagnostic test findings that may suggest PE:
  • ECG – sinus tach, signs of right heart strain (S1Q3T3, T wave inversions V1-3, RBBB)
  • CXR – Westermark sign (focal area of translucency due to oligemia) or Hampton’s hump (wedge-shaped opacity with a rounded convex apex toward the hilum)
  • Point-of-Care Ultrasound – RV strain (RV dilation, septal flattening). McConnell sign is said to be specific but not sensitive (Video: Right Heart Strain)
  • Lab – elevated Troponin and/or BNP
• These findings are often not found in stable patients with small to moderate sized PE.

• Choosing Wisely Canada guidelines recommend risk stratification using a clinical decision rule prior to ordering a CT Pulmonary Angiogram (CTPA) or Ventilation/Perfusion (VQ) scan in patients with suspected PE. In general, if a pretest probability (PTP) is <2.5% for a disease, there is likely to be more harm than benefit for diagnostic imaging tests.
• The first step in selecting a diagnostic approach is to develop a PTP for PE.
• Patients with a lower PTP (<15%) stratified by the application of the Well’s criteria for PE, should be further risk stratified using the Pulmonary Embolus Rule Out Criteria (PERC) rule or with the use of a D-dimer test.⁵
• A negative PERC score means that the likelihood of PE is < 2%.

STEP 1: Apply the Well’s Score for PE  (MDCalc to calculate Wells score)

**Wells Total Score: >4.5 PE is likely. Arrange for imaging. Anticoagulate if no contraindications and delay more than 4 hours.

**Wells Total Score: <4.5 PE is unlikely (< 15%). Apply PERC rule.

STEP 2: Apply PERC Rule (MDCalc to calculate PERC rule)

• If PERC negative (Score=0): STOP. Chance of PE is < 2%.
• If ANY PERC point is positive, PE cannot be excluded.

STEP 3: Order a D-dimer

• If D-dimer negative: STOP.
  • apply age-adjusted D-dimer criteria for those age > 50yrs¹¹
  • Formula: age (in years) x 10 mcg/L
    • For example, if your patient is 70 years of age, their cutoff D-dimer score will be 700 mcg/L (70 x 10 mcg/L).

*Note: be sure to check the units of your hospitals D-dimer assay

• If D-dimer positive: Arrange for imaging. Anticoagulate if no contraindications and imaging is delayed more than 4 hours.

• CTPA – this is the imaging modality of choice in most patients.
• VQ scan – for patients with renal insufficiency contrast allergy, young patients and pregnant women.
• Consult radiology if there is any question about the optimal imaging modality. Risk of worsening renal failure is not as high as once thought.

• Determine the cause for shock (Clinical Summary coming soon to BC EMN) and manage accordingly.
• If there is a high probability for PE based on clinical features then start empiric treatment urgently and order confirmatory testing.

1. Thrombosis Canada. Clinical Guides 2018. From: http://thrombosiscanada.ca/wp-content/uploads/2018/04/Pulmonary-Embolism-Diagnosis-2018Apr03.pdf

   
   

2. Konstantinides SV, Torbicki A, Agnelli G, Danchin N, Fitzmaurice D, Galiè N, Gibbs JS, Huisman MV, Humbert M, Kucher N. 2014 ESC Guidelines on the diagnosis and management of acute pulmonary embolism: The Task Force for the Diagnosis and Management of Acute Pulmonary Embolism of the European Society of Cardiology (ESC) Endorsed by the European Respiratory Society (ERS). European heart journal. 2014 Aug 29;35(43):3033-73

   
   

3. Choosing Wisely Canada Recommendations 2018. Retrieved September 2018 from: https://choosingwiselycanada.org/emergency-medicine/

   
   

4. Wells PS, Anderson DR, Rodger M, Stiell I, Dreyer JF, Barnes D, Forgie M, Kovacs G, Ward J, Kovacs MJ. Excluding pulmonary embolism at the bedside without diagnostic imaging: management of patients with suspected pulmonary embolism presenting to the emergency department by using a simple clinical model and d-dimer. Annals of internal medicine. 2001 Jul 17;135(2):98-107.

   
   

5. Kline JA, Courtney DM, Kabrhel C, Moore CL, Smithline HA, Plewa MC, Richman PB, O’neil BJ, Nordenholz K. Prospective multicenter evaluation of the pulmonary embolism rule‐out criteria. Journal of Thrombosis and Haemostasis. 2008 May;6(5):772-80.

   
   

6. Singh B, Parsaik AK, Agarwal D, Surana A, Mascarenhas SS, Chandra S. Diagnostic accuracy of pulmonary embolism rule-out criteria: a systematic review and meta-analysis. Annals of emergency medicine. 2012 Jun 1;59(6):517-20.

   
   

7. Righini M, Van Es J, Den Exter PL, Roy PM, Verschuren F, Ghuysen A, Rutschmann OT, Sanchez O, Jaffrelot M, Trinh-Duc A, Le Gall C. Age-adjusted D-dimer cutoff levels to rule out pulmonary embolism: the ADJUST-PE study. Jama. 2014 Mar 19;311(11):1117-24.

   
   

8. Pulmonary Embolism. Susan R. Kahn,M.D., and Kerstin de Wit, M.B., Ch.B.,M.D.