Deep Vein Thrombosis (DVT) Flashcards
What is venous thromboembolism?
Venous thromboembolism (VTE) is a term used to describe both deep vein thrombosis (DVT) and pulmonary embolism (PE)- disorders caused by thrombus formation.
Briefly describe Virchow’s triad
The formation of a thrombus in a patient is dependent on any one of Virchow’s Triad being present:
- Abnormal blood flow-usually due to recent immobility, such as a long-distance flight or being bed-bound in hospital
- This is the most common underlying cause of a DVT
- Abnormal blood components- can be caused by multiple factors, such as smoking, sepsis, malignancy, or even inherited blood disorders (e.g. Factor V Leiden)
- Abnormal vessel wall- can be from atheroma formation, inflammatory response, or direct trauma
What are the risk factors for VTE?
The main risk factors for developing a venous thromboembolism include:
- Increasing age
- Previous VTE
- Smoking
- Pregnancy or recently post-partum
- Recent surgery (especially abdominal surgery, pelvic surgery, or hip or knee replacements)
- Prolonged immobility (> 3 days)
- Hormone replacement therapy or the combined oral contraceptive pill
- Current active malignancy
- Obesity
- Known thrombophilia disorder (e.g. antiphospholipid syndrome or Factor V Leidin)
What are thrombophilias? And give examples
Thrombophilias are conditions that predispose patients to develop blood clots. There are a large number of these:
- Antiphospholipid syndrome (this is the one to remember for your exams)
- Antithrombin deficiency
- Protein C or S deficiency
- Factor V Leiden
What is deep vein thrombosis (DVT)?
A deep vein thrombosis refers to the formation of a blood clot in the deep veins of a limb, most commonly affecting those of the legs or pelvis.
How do DVTs present?
DVTs are almost always unilateral. Bilateral DVT is rare and bilateral symptoms are more likely due to an alternative diagnosis such as chronic venous insufficiency or heart failure. DVTs can present with:
- Calf or leg swelling
- Dilated superficial veins
- Tenderness to the calf (particularly over the site of the deep veins)
- Oedema
- Colour changes to the leg
What parameters are assessed when investigating Well’s Score for DVT?
- Active cancer (treatment ongoing, within 6 months, or palliative)
- Paralysis, paresis or recent plaster immobilisation of lower extremities
- Recently bedridden for 3 days or more, or major surgery within 12 weeks requiring general or regional anaesthesia
- Localised tenderness along the
- distribution of the deep venous system
- Entire leg swollen
- Calf swelling at least 3 cm larger than asymptomatic side
- Pitting oedema confined to the symptomatic leg
- Collateral superficial veins (non-varicose)
- Previously documented DVT
- An alternative diagnosis is at least as likely as DVT
How does a Wells score dictate further investigations?
If a deep vein thrombosis is suspected in a patient, the DVT Wells’ Score should be calculated:
- Score less than or equal to 1: DVT is clinically unlikely, requires a further D-dimer test to exclude
- Score greater than 2: DVT is clinically likely and a DVT diagnosis should be confirmed via either a ultrasound scan (more common) or a contrast venography (rarely used)
What are other causes of raised D-dimers?
A D-dimer test is sensitive but not specific; a D-dimer may also be raised following recent surgery or trauma, with ongoing infection or inflammation, concurrent liver disease, or pregnancy, and indeed in any patient with a prolonged hospital stay.
Briefly describe how to measure the leg when examining a patient with a suspected DVT
To examine for leg swelling measure the circumference of the calf 10cm below the tibial tuberosity. More than 3cm difference between calves is significant.
Following a Well’s score >2, what is the imaging used to diagnose a DVT?
Ultrasound doppler of the leg is required to diagnose deep vein thrombosis. NICE recommend repeating negative ultrasound scans after 6-8 days if there is a positive D-dimer and the Wells score suggest a DVT is likely.
What imaging tests are used to diagnose DVT?
Pulmonary embolism can be diagnosed with a CT pulmonary angiogram or ventilation–perfusion (VQ) scan.
Briefly describe VTE prophylaxis
Every patient admitted to hospital should be assessed for their risk of venous thromboembolism (VTE).
If they are at increased risk of VTE they should receive prophylaxis with low molecular weight heparin such as enoxaparin unless contraindicated. Contraindications include active bleeding or existing anticoagulation with warfarin or a NOAC.
Anti-embolic compression stockings are also used unless contraindicated. The main contraindication for compression stockings is significant peripheral arterial disease.
What is the immediate treatment for DVT?
Note: no renal impairment, active cancer, antiphospholipid syndrome or haemodynamic
instability
Direct oral anticoagulants (DOACs) are now recommended as as first line treatment for DVT.
Caution is advised in those with chronic renal impairment or if taking potentially interacting medications.
Offer apixaban or rivaroxaban.
What is the mechanism of action of DOACs?
Direct factor Xa inhibitors: apixaban, rivaroxaban and edoxaban
Direct thrombin inhibitor: dabigatran
