Deep Vein Thrombosis Flashcards
Define DVT.
The development of a blood clot in a major vein deep to the musculature → impaired venous blood flow → consequent leg swelling and pain.
Rarely life threatening on its own but can cause PE.
Explain the aetiology of DVT.
3 factors (known as Virchow’s triad) , individually or together, lead to most DVTs :
- vessel injury,
- venous stasis,
- and activation of the clotting system (hypercoagulability)
What are the types of DVT and what does this mean for management?
Risk factors have a major impact on determining the length of time that anticoagulant therapy is offered.
In order of increasing risk of recurrent VTE:
- Major transient provoked (e.g. surgery lasting >60 minutes) within last 3 months
- Minor transient provoked (e.g. COCP, hospitalisation), within last 2 months
- Unprovoked
- Persistent provoked (e.g. active cancer)
List some risk factors for DVT.
- 3 or more days of bed rest
- Major surgery in last 3 months
- Hospitalisation in last 2 months,
- Trauma or fracture → immobilisation
- Previous VTE
- Active cancer
- Old age
- Pregnancy/postnatal
- Medical illness (esp infection, inflammation, immobility)
- Mutations/FH:
- Factor V Leiden (x3-4 risk),
- Prothrombin gene G20210A mutation
- Antithrombin deficiency
- Antiphospholipid antibody syndrome
- Drugs: COCP, tamoxifen.
- Flight >4hrs
- Smoking
- Obesity
Name a genetic condition which can predispose to clots.
Factor V Leiden
How does Factor V Leiden increase risk of DVT?
- Factor V is part of the coagulation cascade (see below)
- Mutation in the F5 gene causes factor V Leiden thrombophilia
- Usually the function of FV is inactivated with Activated Protein C (APC) to stop too much clotting but in Factor V Leiden this does not occur –> clotting happens for longer than usual –> abnormal blood clots
What percentage of people with Factor V Leiden thrombophilia ever develop abnormal clotting?
Only about 10 percent of individuals with the factor V Leiden mutation ever develop abnormal clots.
Apart from DVT, name another risk associated with Factor V Leiden thrombophilia.
- Miscarriage in the second/third trimester of pregnancy (x2-3 risk)
- Pulmonary emboli
What is the inheritance pattern of Factor V Leiden?
Factor V Leiden is an autosomal dominant genetic condition that exhibits incomplete penetrance i.e. not everyone will develop the disease.
What are the clinical features of DVT?
- Unilateral calf swelling - difference of >3cm between limbs measured 10cm below the tibial tuberosity
- Localised pain long deep venous system - palpate adductor canal and popliteal fossa
- Redness and warmth
- Coolness
- Prominent superficial veins - not varicose but dilated over foot and leg
Uncommon:
- swelling of entire leg
- plhegmasia cerulea dolens
Which 2 signs can be used to confirm DVT?
- Hofman’s sign - tenderness with dorsiflexion of the foot
- Pratt’s sign - calf pain on palpation
Both poor sensitivity and specificity.
What is phlegmasia cerulea dolens?
Cyanosed and painful leg due to ischaemia - massive DVT can obstruct not only the venous outflow but also the arterial
How do you diagnose DVT?
Calculate Wells score - assess pre-test probability
Ultrasound imaging - 1st line is venous duplex ultrasound if Wells’ score of 2 or more or <2 but with elevated D-dimer.
- Alternatively CT
Quantitative D-dimer level - where Wells’ score is <2. Breakdown product of cross-linked firbin so elevated in acute clots.
Other tests:
Bedside - pregnancy test,
Bloods- FBC (suggesting malignancy e.g. anaemia/leucopenia, high Plt), INR & aPTT (required before starting warfarin and IV heparin respectively) , urea & creatinine, LFTs (?cancer, hepatic dysfunction before starting anticoagulants) , thrombophilia screen
Imaging - whole leg US,
Describe how you would assess the Wells’ score.
Assesses clinical PROBABILITY of DVT and what should be done next.
What is the treatment of confirmed DVT?
Anticoagulation for at least 3 months (up to 6 months in active cancer).
Type depends on:
-
Renal impairment
- GFR 15-50ml/min → api/rivaroxaban OR VKA +/- heparin bridging
- GFR <15ml/min → LMWH/UFH OR VKA + heparin bridging
-
Active cancer
- DOAC unless unsuitable
-
Antiphospholipid syndrome
- VKA + heparin bridging
Conservative:
Physical activity - helps reduce port-thrombotic syndrome
Gradient stockings - for patients with acute/chronic symptoms of DVT
Surgical:
IVC filter - where there is active bleeding, or post-surgical cause
In a patient with renal impairment (for example), why do you need to give both heparin and warfarin as initial treatment for DVT?
Heparin works immediately providing anticoagulation to prevent the thrombus enlarging. Warfarin takes at least 48 hours to produce a therapeutic effect and therefore should be started at the same time as the heparin. When the INR is within the therapeutic range, the heparin can be discontinued.
Must maintain INR between 2.0 and 3.0
Maintain for 3-6months
NB: aspirin has no therapeutic effect in DVT.
Which patients might benefit from an IVC filter?
Those who cannot be given anticoagulant therapy (e.g. if they have had recent surgery or bleeding diathesis). It stops PE
What is the MOA of fondaparinux? Dalteparin?
Fondaparinux binds to its binding site on antithrombin (AT), resulting in irreversible conformational changes, which enables it to inhibit Xa, which is needed to activate factor II (prothrombin) to thrombin.
Dalteparin (and other LMWH) bind to factor X and AT promoting antithrombin’s activity in blocking key reactions in the clotting cascade
What is the algorithm for DVT management depending on Wells’ score?
<2 (15% risk) → D dimer +/- US
_>_2 (40% risk) → USS +/- discuss or treat
What is shown?
Phlegmasia cerulea dolens - swelling, significant pain, and cyanosis
Tx: do not wait for Ix, immediately start Tx and refer to vascular surgery.
Compare the DVT vs PE Wells score.
