Venous Thrombosis Flashcards
Give examples of arterial thrombotic events.
- Coronary
- Cerebral
- Peripheral
Give examples of venous thrombotic events.
- DVT
* PE
____ muscles squeeze blood up through the veins
Calf
What kind of system are arterial thrombus found?
High pressure system
What process has a role in the formation of an arterial thrombus?
Atherosclerosis
What is the thrombus formed in an arterial thrombus like?
Rich in platelets !!
How is an arterial thrombus treated?
- Aspirin and other anti-platelet drugs
* Modify risk factors for atherosclerosis
What kind of system is a venous thrombus found in?
LOW pressure system
What is the main risk factor for a venous thrombus?
Blood stasis !!
What does NOT happen in the formation of a venous thrombosis?
Platelet activation
What is the clot like in a venous thrombosis?
Rich in fibrin – due to activation of the coagulation cascade
What triad helps us to understand how a venous thrombosis occurs?
Virchow’s triad: stasis, vessel wall, hypercoagulability
What is the ‘vessel wall’ mentioned in virchows triad referring to?
Valves
(esp. if had a previous VT as valve will already be damaged, and blood will be able to fall backwards).
Why does the risk of venous thrombosis increase with age?
Valves degenerate with age
How is a venous thrombosis treated?
Anti-coagulation
(not anti-platelets as platelets aren’t the problem here)
e.g. heparin / warfarin / new oral anti-coagulants
How does a DVT present?
- Limb feels hot, swollen and tender
* Pitting oedema
What Ix do you want to do to find out where a clot is in the leg?
Doppler US
List various causes of a PE.
- Pulmonary infarction.
- Pleuritic chest pain – knife-like pain on inspiration.
- Cardiovascular collapse/death.
- Hypoxia.
- Right heart strain.
What ECG pattern is suggestive of a PE?
SI QIII TIII pattern – deep S wave in lead I, Q wave in III, inverted T wave in III.
What is the population risk of a VTE?
1/1000 per year
What is the yearly risk of a VTE in: i) young adults? Ii) elderly people?
i) 1/10,000
ii) 1/100
What is the lifetime risk of a VTE?
2.5%
What are the risk factors for a VTE?
- Age
- Obesity
- Pregnancy
- Puerperium
- Oestrogen therapy - OCP, HRT
- Previous DVT/PE
- Trauma/surgery
- Malignancy
- Paralysis
- Infection
- Thrombophilia
What is the biggest risk factor for a VTE?
A previous VTE
What are the risk factors for a VTE in terms of STASIS?
- Age
- Obesity
- Pregnancy
- Previous DVT/PE
- Trauma/surgery
- Malignancy
- Paralysis
What are the risk factors for a VTE in terms of VESSEL WAL?
- Age
* Previous DVT/PE
What are the risk factors for VTE in terms of HYPERCOAGULABILTY?
- Age
- Pregnancy
- Puerperium
- Oestrogen therapy - OCP, HRT
- Trauma/surgery
- Malignancy
- Infection
- Thrombophilia
Clotting factors are acute phase proteins, so being unwell pushes clotting factors up
T
Oestrogen-containing pill – increases factor VIII, fools body into thinking you’re pregnant, risk of VTE rises 10-fold
T
How do all the risk factors for hypercoagulability increased the risk of a VTE?
They are associated with the release of tissue factor, raised VWF and factor VIII
What is thrombophilia?
Familial or acquired disorders of the haemostatic mechanism which are likely to predispose to thrombosis.
Outline the potential mechanism for a thrombophilia.
- Increased coagulation activity
- platelet plug formation
- fibrin clot formation
- Decreased fibrinolytic activity
- Decreased anticoagulant activity
Name 2 naturally occurring anticoagulants.
- Anti-thrombin
* Protein C and Protein S
How does anti-thrombin work?
Switches off thrombin and other blood clotting factors.
How does PC and PS work?
Switch off VIII/IXa and V/Xa
What – in relation to proteins C and S – can lead to thrombophilia?
Factor V leiden
What does factor V leiden do?
Results in a single base pair change in factor V, meaning that protein C and protein S can’t switch factor V off as well as they should be able to
What are hereditary thrombophilias?
A group of genetic defects in which affected individuals have an increased tendency to develop premature, unusual and recurrent thromboses.
Give examples of inherited thrombophilias.
- Factor V Leiden.
- Prothrombin 20210 mutation.
- Antithrombin deficiency.
- Protein C deficiency.
- Protein S deficiency.
When should screening for inherited thrombophilias be considered?
- Venous thrombosis <45y/o.
- Recurrent venous thrombosis.
- Unusual venous thrombosis (e.g. upper limb, cerebral veins).
- Family history of venous thrombosis.
- Family history of thrombophilia.
What should be considered in the management of inherited thrombophilias?
- Advice on avoiding risk e.g. avoid COCP.
- Short term prophylaxis – to prevent thrombotic events during periods of known risk.
- Short term anticoagulation – to treat thrombotic events.
- Long term anticoagulation – if recurrent thrombotic events.
Why do some people with hereditary thrombophilia NEVER suffer a thrombosis?
Hereditary thrombophilias greatly increase risk of thrombosis, but from a very low baseline rate, meaning risk is still very low
What does long term anticoagulation need to achieve a balance between?
Risk of recurrent thrombosis vs Risk of serious haemorrhage
What is much more important than the results of thrombophilia screening?
History + history of previous thrombosis
What is an acquired thrombophilia?
An autoimmune condition which leads to an increased tendency to thrombosis
Give an example of an acquired thrombophilia.
Antiphospholipid antibody syndrome
What imposes a higher risk for thrombosis - acquired or hereditary thrombophilia?
ACQUIRED
What are the clinical features of APLS?
- Recurrent thromboses
- arterial, including TIA’s
- venous
- Recurrent foetal loss
- 3 consecutive miscarriages, or an unexplained late miscarriage
- Mild thrombocytopenia
What does APLS involve the activation of?
Both primary and secondary haemostasis
Explain the pathogenesis of APLS.
Antibodies lead to a conformational change in β2 glycoprotein 1 (a protein with unknown function in health) which leads to activation of both primary and secondary haemostasis and vessel wall abnormalities.
What are antiphospholipid antibodies?
Autoantibodies which have specificity for anionic phospholipids, and which prolong phospholipid dependent coagulation tests in vitro (e.g. false prolonged APTT).
What is another name for antiphospholipid antibodies?
Lupus anticoagulants
Give examples of things/conditions associated with antiphospholipid antibodies.
- Autoimmune disorders, especially SLE.
- Lymphoproliferative disorders.
- Viral infections.
- Drugs.
- Primary.
What does the treatment of APLS need to tackle?
- Activation of both primary and secondary haemostasis
* Arterial and venous thrombosis
What drugs are prescribed to patients with APLS?
Both aspirin and warfarin
