Venous thrombosis (use cardio deck) Flashcards
What are the key points to remember with regards to the venous system?
- It is a low pressure system
- Thin smooth muscle component in the wall compared to the high pressure arterial system
- Relies a lot on the calf muscles contraction and relaxation to aid in venous return (as doesnt have a lot of muscle in its vessel wall like the arterial to do it on its own) (this is why immobility is a massive risk factor)
- Also contains valves to prevent backflow
What are the 2 main types of venous thromboses ?
- DVT
- PE
Define what DVT, PE and VTE is
- DVT = Deep Venous Thrombosis. A thrombus (clot) formed in the deep venous circulation (usually legs) but can be anywhere
- PE = Pulmonary Embolism. A thrombus (clot) that has embolised (travelled) and lodged in the pulmonary circulation
VTE = Venous Thromboembolic Disease. Covers both DVT and PE.
What is the difference between a proximal and a distal DVT ?
- Distal vein thrombosis refers to DVT of the calves
- Proximal vein thrombosis refers to DVT of the popliteal vein or the femoral vein. These thromboses are termed ‘proximal’ because they are closer to the heart
What type of clot forms in venous thrombosis ?
Fibrin rich clot - platelets are NOT activated in these types of clots
What triad of factors typically causes venous thromboses ?
Virchows traid:
- Stasis
- Endothelial (vessel wall) damage
- Hypercoagulability
What happens to the risk of VTE as you get older ?
The risk dramatically increases:
- Young adults 1/10 000 per annum
- Elderly 1/100 per annum
What are the causes of stasis which result in increased risk of VTE ?
- Age
- Marked obesity
- Pregnancy
- Previous VTE/PE
- Trauma/surgery
- Malignancy
- Paralysis e.g. stroke
What are the main causes of vessel wall damage causing increased risk of thrombosis ?
- Age
- Previous DVT/PE
What are the factors which cause hypercoagulability resulting in increased venous thrombosis ?
- Age
- Pregnancy & Peurperium
- Oestrogen therapy
- Trauma/surgery
- Malignancy
- Infection
- Thrombophilia
- IBD
What are the signs and symptoms of DVT
- Calf warmth, tenderness, swelling and erythema
- usually presents unilaterally
What are the signs and symptoms of PE ?
- Sudden SOB
- Sudden, sharp chest pain that may become worse with deep breathing or coughing. (pleuritic chest pain)
- Tachypnoea & Hypoxia
- Tachycardia
- Haemoptysis
- Collapse
- DVT
How is a DVT diagnosed ?
Initially do a WELLS score
If WELLS score greater than 2 then DVT likely and do:
- 1st line = Venous doppler US if neg do D-dimer
- 2nd line = If D-dimer pos then repeat US, if neg then rule out DVT
- If cant do doppler within 4hrs do d-dimer and give LMWH heparin whilst waiting
If WELLS score 1 or less DVT is unlikely so do:
- 1st line = D-dimer if pos then do a Venous doppler US of the leg
- If you cant do doppler within 4hrs give LMWH
How is a PE diagnosed ?
If a patient presents with signs or symptoms of PE do a CXR initially to rule out other causes and potentially diagnose a PE (note >50% CXR’s in PE are normal)
Do a PE WELLS score
If PE likely (score >4):
- CTPA if neg consider doppler leg US
If unlikely (score ≤4):
- Do D-dimer if pos then do a CTPA
Note if there is any delay in getting CTPA then give patient LMWH
When should V/Q scan be used over CTPA in PE diagnosis ?
If the patient has an allergy to contrast media or renal impairment
What ECG abnormalities are associated with PE ?
- A large S wave in lead I, a large Q wave in lead III and an inverted T wave in lead III - ‘S1Q3T3’.
- RBBB and right axis deviation are also associated with PE
- sinus tachycardia may also be seen
In pregnancy which should be used CTPA or V/Q for PE diagnosis ?
The decision to perform a V/Q or CTPA should be taken at a local level after discussion with the patient and radiologist:
- CTPA increases maternal risk of breast cancer
- V/Q increases the risk of childhood cancer
What is the treatment for venous thrombosis i.e DVT and PE ?
- 1st line = Rivaroxiban (NOAG) (or apixaban)
- 2nd line = LMWH or fondaparinux + warfarin for the long-term treatment
Continue LMWH heparin or fondaparinux for roughly 5 days or when INR is >2 and then continue with just warfarin
Tx usually for 3-6months
1st line - If pregnant or have active cancer then do not move onto the warfarin use LMWH for the full 6months of prophylactic treatment
If patient is haemodynamically unstable (systolic<90) with a PE then consider using thrombolytic therapy using unfractionated heparin (dalteparin), otherwise normal anti-coag treatment
What is post-thrombotic syndrome ?
It is a common complication seen in patients who have had a DVT, it is a clinical syndrome which can result in the following manifestations:
- painful, heavy calves
- pruritus
- swelling/oedema
- varicose veins
- venous ulceration
- eczema
What is the treatment of post-thrombotic syndrome ?
- Compression stockings
- Leg elevation
What is meant by thrombophilias ?
Familial or acquired disorders of the haemostatic mechanism which are likely to predispose to thrombosis, usually DVT or PE (VTE’s)
What are the inherited causes of thrombophilia and explain them ?
- Factor V Leiden - usually due to a single point mutation in factor V which makes this factor resistant to being broken down by Protein C and S
- Prothrombin 20210 mutation - causes high levels of prothrombin and increased risk of thrombosis
- Anti-thrombin deficiency - this is a cofactor of heparin and inhibits coagulation so without it, it results in lack of inhibition of coagulation
- Protein C & deficiency - these proteins act to deactivate factors V and VIII, so def. will result in lack of coagulation inhibition
When should you suspect someone to have hereditary thrombophilia ?
- Venous thrombosis <45 years old
- Recurrent venous thrombosis
- Unusual venous thrombosis e.g. cerebral veins or upper limb
- Family history of venous thrombosis
- Family history of thrombophilia
What should you do when suspecting someone of a hereditary thrombophilia? also what is the catch with this ?
You should consider screening for these hereditary deficiencies
But note in about 50% there wont be a cause identified as there is likely to be other genetic abnormalities to predispose to thrombosis which haven’t been identified yet
What are the symptoms of thrombophilias ?
None - only results in symptoms if a thrombosis have developed i.e. DVT or PE
Why do some people with thrombophilias never develop thrombosis ?
Shows patient X who has a thrombophilia e.g. factor V ledien as its the most common and essentially people with thrombophilias have an increased risk of thrombosis but people need to usually have multiple Risk Factors for Thrombotic events to occur e.g. breaking leg and having a period of immobility also with having a thrombophilia
What is the management of hereditary thrombophilias ?
Advice on avoiding risk factors e.g. combined pill and HRT treatment also advice about other risk factors such as immobility etc
Treatment of thrombotic events (usually treat for 6 months):
- 1st line = NOAG e.g. rivaroxiban
- 2nd line = LMWH or fondaparinux for short period with warfarin for the longer term (need to give the heparin whilst starting warfarin)
Long term anticoagulation - if recurrent thrombotic events:
- 1st line = NOAG
- 2nd line = long-term warfarin (LMWH heparin always needed for the first few days when starting)
Short term prophylaxis - to prevent thrombotic events during periods of known risk
What is the main acquired thrombophilia ?
Anti-phospholipid antibody syndrome (this carries a greater thrombosis risk than hereditary thrombophilias)
What are the main features suggestive of anti-phospholipid antibody syndrome ?
Recurrent thromboses:
- Arterial - including TIA’s
- Venous - DVT and PE
Recurrent fetal loss - investigate for this if have had 3 or more consecutive pregnancy losses
Mild thrombocytopenia
Describe the pathogenesis of anti-phospholipid syndrome
Antibodies lead to a conformational change in β2 glycoprotein 1 which leads to activation of both primary and secondary haemostasis
What are the antibodies associated with anti-phospholipid syndrome ?
- Lupus anticoagulant
- Anti cardiolipin antibodies
- Anti-B2 glycoprotein antibodies
What happens to the APTT which can be confusing in anti-phospholipid syndrome ?
It can be prolonged but these patients dont have a tendancy to bleed
What conditions may pre-dispose someone to developing anti-phospholipid syndrome ?
- Lymphoproliferative Disorders
- Viral Infections
- Drugs
But note it is usually a primary disorder i.e. arises without an underlying cause
What is a common autoimmune condition associated with anti-phospholipid syndrome ?
SLE
What is the treatment of anti-phospholipid syndrome ?
Thrombolysis for serve-life threatening thrombosis
- Aspirin for arterial thrombosis
- Heparin and then warfarin for venous thrombosis
Describe the prophylaxis for patients at risk of developing VTE
- Ensure adequate hydration
- Early mobilisation
- TED stockings or intermittent pneumatic compression devices
Use intermittent pneumatic compression devices following stroke, otherwise go for TED stockings
When should you not give someone TED stockings ?
- Suspected or proven peripheral arterial disease
- Peripheral arterial bypass grafting
- Peripheral neuropathy or other causes of sensory impairment
