Thrombosis Flashcards
how does DVT cause the sx and a PE
Blood clot in leg – blood cant get back = painful swollen leg
can move into R side of heart – block pul circ – R heart cant cope with strain = pt death
why is DVT important
DVT and PE are common and preventable causes of death
difficult to reverse - need to get rid of clot and restore circulation
may be indication of underlying cancer
consequence of DVT
death
recurrence common
thrombophlebetic pain - recurrent pain, swelling and ulcers (ie still have impaired circ)
pulmonary HTN if clot in lung not cleared – circ pressure in lungs changes
what are the contributory factors to thrombosis
virchow’s triad:
* blood
* vessel wall
* blood flow - coagulation factors accumulate more easily
factors in the blood that lead to thrombosis
Viscosity
* Haematocrit - myeloproloferative, polycythaemia
* Protein/paraprotein
Platelet count high – important in coagulation = thrombosis risk
Coagulation system - Net excess of procoagulant activity
coagulation cascade
what are the procoagulant factors
V
VIII
XI
IX
X
II
Fibrinogen
Platelets
what are the anticoagulant factors
TFPI
Protein C
Protein S
Thrombomodulin
EPCR
Antithrombin
Fibrinolysis
how do deficiencies in different factors (or having factor 5 liden) alter liklihood of thrombosis freee survival
All these patients ahd family members with thrombophilic traits
Antithrombin def is the highest risk of thrombosis
Curves show for people with these conditions – steep decline – increased tendency to thrombosis
Even curve with no defect falls steeper than general pop – so probably other things involved in these families
Factor V leiden – procoag effect
Half pf thrombosis tend to be precipitated by another factor eg surgery/COCP
how is the vessel wall usually antithrombotic
Expresses anticoagulant molecules
* Thrombomodulin - change thrombin from procoag
* Endothelial protein C receptor
* Tissue factor pathway inhibitor
* Heparans
Does not express tissue factor (procoag)
Secretes antiplatelet factors
* Prostacyclin
* NO
collagen and TF are kept outsied of the blood vessel (they are procoag)
eg of stimuli that make the vessel wall prothrombotic
Infection – including COVID-19
Malignancy
Vasculitis
Trauma
prothrombotic changes to the vessel wall
Anticoagulant molecules (eg TM) are down regulated
TF may be expressed
Prostacyclin production decreased
Adhesion molecules upregulated
Von Willebrand factor release
* Platelet and neutrophil capture
* Neutrophil extracellular traps (NETS) form
Capture Neutrophils which undergo NETosis And spill out DNA – prothrombotic surface
Blood cells on endothelial surface stim clotting, capture plts and activate them and capture vWF
mechanism of how stasis -> thrombosis
Accumulation of activated factors
Promotes platelet adhesion
Promotes leukocyte adhesion (NET) and transmigration
Hypoxia produces inflammatory effect on endothelium
-> Adhesion, release of VWF
ie make it easy for neutrophils and plts to stick to surface
causes of stasis
Immobility -> Surgery, Paraparesis, Travel
Compression -> Tumour, pregnancy
Viscosity -> Polycythaemia, Paraprotein
Congenital -> Vascular abnormalities
how does risk of PE change with flight distance
as distance increases, so does risk of PE
can thrombotic risks interact
yes
Circumstantial – reason got it on that particular day – cross thrombotic threshold
Circumstance is something that you can remove
compare the anticoagulants
how to determine whether long term anti-coagulants are needed
does the risk of thrombosis outweigh the risk of bleeding
can use lower dose of DOAC than warfarin, and they have less risk of serious bleed
how do you identify risk of recurrence
Risk depends on what caused the first thrombosis
if DVT after surgery - risk of recurrance is low
Need to target the idiopathic people – it is just them and no external causes
When in the middle difficult – how much risk are you taking away by stopping the pill etc – need to do other tests
To determine whether will benefit from ling term anti coag – depends on circumstance of prev thrombosis
distal (below knee) low risk of recurrence, prox = high risk
