• Deep vein thrombosis (DVT) is common, with over 45,000 cases diagnosed in Canada each year.
• Complications can include pulmonary embolism (PE) and post-thrombotic syndrome.
• Risk factors for development of a DVT are closely related to Virchow’s triad (venous stasis, vascular injury and hypercoagulability) including recent surgery, immobilization, malignancy, trauma, pregnancy, estrogen use, and varicose veins.
• Patients may present with calf pain or cramping, warmth, erythema and edema to a unilateral limb, primarily the lower limb.
• 4-10% of DVT’s involve upper extremity:
  • 80% of these are secondary:
    • Pacemaker or Central Venous Catheters (including peripherally inserted central catheters (PICC line).
    • Anatomical: cervical rib; hypertrophy of scalenus muscle.
    • Trauma: clavicle fracture.
  • Paget-Schroetter syndrome:
    • Venous thrombosis of the subclavian vein in thoracic inlet syndrome.
    • Typically, young athletes.
    • Sports like baseball, swimming, or tennis.
  • Cancer
    • Pancoast tumor.
• Diagnosis of DVT requires determining the pre-test probability of DVT either through clinical gestalt (depends on clinical experience) or better to use a clinical tool, such as the Well’s Score followed by D-dimer/ultrasound as indicated.

• Thrombosis Canada recommends patients presenting with suspected DVT should be risk stratified. The most commonly used tool is the Well’s Score for DVT.

• Wells Score > 2: DVT Likely
  • Perform Venous Compression Ultrasound (CUS) of the extremity
    • CUS is positive, initiate appropriate treatment for DVT.
    • CUS is negative, recommend performing a D-Dimer:
      • D-Dimer is negative, DVT can be ruled out.
      • D-Dimer is positive, repeat CUS in one week.
•  Wells Score < 2: DVT Unlikely 
  • Perform a D-Dimer:
    • D-Dimer is negative, a DVT can be ruled out.
    • D-Dimer is positive, perform a CUS.
      • If the CUS is positive, a diagnosis of DVT can be made.
      • If the CUS is negative, DVT can be ruled out.
• D-Dimer
  • D-Dimer is a marker of fibrin clot breakdown.
  • It is a highly sensitive (up to 90%) but non-specific test.
  • D-dimer can be elevated in many other conditions including:
    • Inflammatory diseases.
    • Infection.
    • Malignancy.
    • Advanced age – the use of an age-adjusted D-dimer cutoff has not been well validated for excluding DVT (unlike for PE). As such, its use for DVT diagnosis is not routinely recommended at this time by Thrombosis Canada.
    • Pregnancy.
    • Trauma.
    • Surgery.
  • In contrast to PE, there is no evidence to suggest that an age-adjusted D-dimer cutoff should be used to exclude DVT.
  • A D-dimer less than a fixed cut-off, in combination with validated clinical prediction rules (Wells score) can be used to rule out DVT in patients where DVT is deemed unlikely.

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Source: Diagnostic strategy adapted from Thrombosis Canada Deep Vein Thrombosis Diagnosis guideline.

1. Thrombosis Canada – DVT Clinical Guides, 2016.

   
   

2. Kearon C. Natural history of venous thromboembolism.Circulation 2003;107:I22-30.

   
   

3. Stone J, Hangge P, Albadawi H, Wallace A, Shamoun F, Knuttien MG, Naidu S, Oklu R. Deep vein thrombosis: pathogenesis, diagnosis, and medical management. Cardiovasc Diagn Ther. 2017 Dec;7(Suppl 3):S276-S284.

   
   

4. Mammen EF. Pathogenesis of venous thrombosis. Chest. 1992 Dec;102(6 Suppl):640S-644S.