Deep Vein Thrombosis Flashcards
what is the definition of deep vein thrombosis?
Deep vein thrombosis (DVT) is the development of a blood clot within a vein deep to the muscular tissue planes
what is the epidemiology of deep vein thrombosis?
Deep vein thrombosis (DVT) occur in 25-50% of surgical patients and many non-surgical patients
- 65% of below-knee DVTs are asymptomatic and these rarely embolize to the lung
- Commonly occurs after periods of immobilisation but it can occur in normal individuals for no obvious reasons
what is the aetiology of deep vein thrombosis?
• Surgery, immobility, leg fracture, oral contraceptive pill, long haul flights, malignancy
• Genetic:
- Factor V Leiden (5%) - common in caucasians, increase risk of thrombus
- PT20210A (3%) - common in caucasians, increase risk of thrombus
- Rare:
• Antithrombin deficiency
• Protein C or Protein S deficiency
• Acquired:
- Anti-phospholipid syndrome
- Lupus anticoagulant
- Hyerhomocysteinaemia - high levels are reduced by taking folate
- Can occur in any vein of the leg or pelvis, but is particularly found in the veins of the calf
- Below the calf there are 6 veins, from the popliteal fossa upwards they merge into one
- A DVT in the calf below the knee is not too much of a concern
- A DVT in above the knee is potentially fatal and usually occurs in the proximal leg vein
what are the risk factors for DVT?
recently bedridden for 3 days or more major surgery within the preceding 12 weeks medical hospitalisation within the preceding 2 months active cancer Pregnancy Increased age Synthetic oestrogen Past DVT Obesity
what is the pathophysiology of DVT?
Deep venous thrombosis usually begins in venous valve cusps. Thrombi consist of thrombin, fibrin, and red blood cells with relatively few platelets (red thrombi); without treatment, thrombi may propagate proximally or travel to the lungs
Virchow’s triad
what are the key presentations of DVT?
calf swelling
localised pain along deep venous system
presence of risk factors
positive Wells score
what are the signs of DVT?
asymmetric oedema
prominent superficial veins
swelling of the entire leg
cyanosis
what are the symptoms of DVT?
Pain calf, swelling and redness
Warm calf
what are the first line investigations for DVT?
- quantitative D-dimer level:
Type of fibrinogen degradation product that is released into the circulation when a clot begins to dissolve
• D-dimer are elevated in other conditions e.g. cancer, pregnancy and post-operatively and a positive result is NOT DIAGNOSTIC of DVT and requires further imaging
• A normal result excludes DVT - venous ultrasound - Find the popliteal vein, if you can squash it shut = no DVT if you cannot = DVT (duplex ultrasound)
full blood count
urea and creatinine
what are the gold standard investigations for DVT?
CT/MRI venography
further investigation for unprovoked DVT
how is DVT managed?
- Low molecular weight Heparin e.g. SC ENOXAPARIN for a minimum of 5 days (at first)
- ORAL WARFARIN with a target INR of 2.5 (2-3) for 6 months after
- Direct acting Oral Anticoagulants (DOAC) similar to warfarin but do not need monitoring
- Compression stockings
- Inferior vena cava filters to reduce risk of pulmonary emboli
- Prevention:
• Early mobilisation post-op
• Compression stockings
• Thrombophylaxis for both low risk and high risk
what are the differential diagnoses for DVT?
Baker’s cyst, cellulitis, lymphedema, chronic venous insufficiency, superficial thrombophlebitis
how is DVT monitored?
medication reviews
what are the complications of DVT?
Pulmonary embolism - part of the clot breaks off and travels through the bloodstream to the lungs
what is the prognosis of DVT?
Many DVTs will resolve with no complications. Post-thrombotic syndrome occurs in 43% two years post-DVT (30% mild, 10% moderate, and severe in 3%). The risk of recurrence of DVT is high (up to 25%). Death occurs in approximately 6% of DVT cases and 12% of pulmonary embolism cases within one month of diagnosis.
