Thrombosis Flashcards
What is a clot?
General term for mass of coagulated blood (can occur outside the body or after death)
What is a Thrombus?
Blood clot formed in situ in a blood vessel or heart chamber during life
What is an Embolus?
Detached intravascular material that is carried from origin to distant site (not just thrombotic material)
What are the 5 types of embolus?
Thrombus (DVT)
Fat embolus
Air embolus
Amniotic fluid embolus
Foreign material
What is Virchow’s triad?
A model that describes and categorises the risks of thrombosis (has 3 main components that contribute to the risk)
What are the 3 main components of Virchow’s triad?
Stasis
Vessel wall injury
Hypercoagulability
What is stasis?
Anything that stops your blood from flowing
What are risk factors for Vessel wall injury?
Endothelial dysfunction
- Smoking
- Hypertension
Endothelial damage
- Surgery
- Catheter (PICC lines)
- Trauma
What are hereditary risk factors for hypercoagulability?
- Factor V Leiden
- Prothrombin G20210A
- Protein C and S deficiency
What are acquired risk factors for hypercoagulability?
- Cancer
- Chemotherapy
- OCR/HRT
- Pregnancy
- Obesity
- HIT
What are clinical risk factors for stasis?
Immobility
Polycythemia
What is factor V Leiden?
-FVL= inherited thrombophilia
-Autosomal dominant (incomplete penetrance)
-3-5% white european pop. are heterozygous
- Often need acquired risk to produce symptoms
What is heterozygous risk for FVL?
5-10x risk
What is homozygous risk for FVL?
16-18x
What is the mutant form of Factor V?
Lack Arg506 cleavage site
What does a mutant form of Factor V cause?
Resistant to degradation by activated protein C, this results in hypercoagulable state
Can lead to unprovoked VTE & recurrent pregnancy loss
What is anti- phospholipid syndrome?
- Acquired thrombophilia
- Autoimmune condition
- 3-5% of general population
- Common in SLE (LUPUS) but most don’t have SLE
What autoantibodies are involved in Anti-phospholipid syndrome?
B2glycoprotein 1
Anti- cardiolipin
Lupus anticoagulant
What type of thrombosis risk is increased in anti- phospholipid syndrome?
Increased risk of arterial or venous thrombosis
How is anti- phospholipid antibody syndrome diagnosed?
- Positive test on 2 occasions
- 6-12 weeks apart
- Venous or arterial thrombosis, thrombocytopaenia or recurrent fetal loss
- Most need to take aspirin daily
- Catastrophic form= large volume of antibodies produced, can lead to organ failure
What causes an arterial thromboses?
- Usually due to endothelial injury/ atherosclerosis
- High pressure & shear stress
What is an arterial thrombus?
- “White” platelet- rich thrombus
- Adherent to vessel wall
Where to Arterial thromboses usually occur?
Coronaries
Carotids
Cerebral vessels
Lower limb arteries
What causes Venous thromboses?
- Usually in non-injured veins and due to stasis
- Low pressure and low flow
- Red blood cell rich thrombus
- Loosly attached and friable
Where do Venous thromboses usually occur?
- Lower limb veins (DVT)
- Pulmonary veins (PE)
- Cerebral venous sinus
What is DVT?
Deep vein thrombosis
Formation of a blood clot (thrombus) in a deep vein
Where does DVT most commonly affect?
Leg veins (femoral or popliteal vein)
OR
the deep veins of the pelvis
How many people get DVT in their lifetime?
1/20
What is VTE?
Venous thromboembolism is a common disease that is often asymptomatic
How many people do clinical symptoms present in of VTE?
1-2 per 1000 people every year
Approx 2/3 of all cases are DVT & 1/3 PE
What is the incidence of DVT during pregnancy?
Approx 1 in 1000 live births
What is the incidence of DVT in critically ill people?
37.2%
What is the DVT wells score?
scoring system based on risk factor
What is the D- dimer test?
Test has 93-95% sensitivity
Negative test= virtually rules out VTE
What are false negatives of the D- dimer test?
False negatives- rare, sample delayed or too early, patient on anticoagulation
What are false positives of the D- dimer test?
Liver disease, inflammation malignancy, trauma, pregnancy, recent surgery, advanced cancer
What is a pulmonary embolus?
Blockage of an artery in the lungs by a substance that has moved from elsewhere in the body or bloodstream
What are the 8 presenting symptoms of PE?
- Dyspnoea
- Tachynoea
- Pleuritic chest pain
- Cough
- Haemoptysis
- Haemodynamic instability
- Collapse/ syncope
- Sudden death
What is the PE wells score?
More than 4 points (PE likely)
Less than 4 points (PE unlikely)
What is CVA?
Cerebrovascular accident
What is a stroke?
A rapidly developing loss of brain function due to a disturbance in the blood supply to the brain
What are the two types of stroke?
Ischaemic (80%)
Haemorrhagic (20)
What are the 3 types of Ischaemic stroke?
Thrombotic- occlusion of small or large vessels in situ
Embolic- occlusion due to embolus; often from heart or blood vessels
Hypoperfusion
What are the two types of Haemorrhagic stroke?
Intra- cerebral haemorrhage (ICH)
Subarachnoid haemorrhage (SAH)
What does treatment of thrombosis depend on?
The type of thrombosis & what risk factors are present (length of risk factors)
What do antiplatelets treat?
Arterial thrombosis
(Aspirin, clopidogrel, dipyridamole)
What do thrombolysis treat?
drugs which rapidly destroy clots, given straight after stroke
What does thromboectomy treat?
break up clot (caution as can make the clot migrate somewhere else)
What do anticoagulants treat?
work against different steps in the clotting cascade, manage underlying risk factors
What is the natural history of a thrombus if it is not treated?
Organisation
1. Acute inflammatory reaction (neutrophils)
2. Chronic inflammatory reaction (lymphocytes)
3. Capillary revascularisation
4. Fibroblasts from granulation tissue and scar
5. Phagocytosis (macrophages)
6. Recanalisation
What is the organisation of a clot?
Break it apart/ prevent clot thrombolysing
What does organisation and recanalisation do?
Make small channels so blood can still flow
