Venous Thromboembolism

General Information

  • Venous Thromboembolism is a common and potentially fatal condition
  • “Deep Vein Thrombosis” is the diagnosis of having a blood clot develop in your venous circulation
  • Blood clots develop due to stagnation of blood and hypercoagulable states
  • Blood clots can mobilise (become emboli) from the deep veins and travel through the right side of the heart and into the lungs (becoming pulmonary embolisms)
  • If the patient has a hole in their heart (i.e. a ventricular septal defect) the blood clot can pass through to the left side of the heart and get sent to the systemic circulation – typically causing a large stroke (this is a common exam question)

N.B. See Respiratory Section for Pulmonary Embolism notes


Risk factors

  • Immobility
  • Recent surgery
  • Long haul flights
  • Pregnancy
  • Hormone therapy with oestrogen (combined oral contraceptive pill and hormone replacement therapy for postmenopausal women)
  • Malignancy
  • Polycythaemia
  • Systemic lupus erythematosus


Wells Score

  • Predicts risk of DVT and pulmonary embolism
  • Use online calculators to calculate score



  • Unilateral
  • Calf/leg swelling (measure circumference of the calf 10cm below the tibial tuberosity, >3cm difference is significant)
  • Dilated superficial veins
  • Tenderness to the calf (particularly over the site of the deep veins)
  • Oedema
  • Colour changes to the leg

N.B. Always ask questions and examine with the suspicion of a potential P.E. as well



  • D-Dimer is sensitive (95%), but not specific (it will go up if there is a DVT, but if it is raised, it could be due to other factors like a pneumonia, DVT, malignancy, rheumatoid arthritis etc)
    • If a D-Dimer is positive and Doppler negative, repeat the doppler after 6-8 days
  • Confirm the diagnosis with a ultrasound Doppler of the leg
    • Patients should have this within 4 hours or receive LMWH whilst waiting
  • Both should be negative to exclude a DVT in patients with a high Wells score



  • Analgesia.
  • Treatment dose LMWH (i.e. enoxaparin 1.5mg/kg) for >5 days (or until INR 2-3 if on warfarin).
  • Long term anticoaguation with a NOAC (first line), warfarin (second line) or LMWH(third line)
  • Target INR for warfarin is 2-3.
  • NOAC options include apixaban, dabigatran and rivaroxaban.
  • Continue anticoagulation for:
    • 3 months if obvious reversible cause
    • Indefinitely if cause unclear / underlying irreversible cause (e.g. cancer) / recurrent VTE



  • Every admission to hospital should be assessed for venous thromboembolism (VTE) risk.
  • If at increased risk of VTE they should receive prophylaxis
  • If no contraindications, this should be 40mg of enoxaparin
  • If eGFR <30, 20mg enoxaparin
  • If risk of bleeding, then use compression stockings
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