Thrombosis Flashcards
What are the 2 forms of thrombosis?
Arterial
Venous
How does arterial thrombosis present?
A result of a high pressure system.
Leads to atherosclerosis, these are platelet-rich areas with a tendency to thrombose.
How is arterial thrombus managed?
Aspirin/Other antiplatelets.
What are causative factors of venous thrombosis?
Valve deterioration
Stasis
What are the 3 components of Virchow’s triad?
Stasis
Endothelial injury
Hypercoaguability
Are venous thromboses full of platelets?
No, they are fibrin-rich.
How are venous thromboses treated?
Heparin/Warfarin
DOACs
How will DVT present?
A hot, tender calf.
Will be swollen.
What is thrombophilia?
An inherited condition conveying an increased risk of blood clots.
Due to a lack of natural anticoagulants. Individual will be predisposed to thrombosis.
What is factor V leiden disorder?
A disorder in which clotting factor V is not switched off correctly, increasing the risk of thrombosis.
When should hereditary thrombophilia be screened for?
under 45s with an unprovoked VT
Recurrent VT
Unusual VT location
Family history
How are hereditary haemophilias managed?
Give prophylaxis at times of reduced mobility/increased risk.
Avoid risk factors.
Only give long-term anticoagulation in those with repeated thrombotic events.
What condition is an example of an acquired cause of thrombophilia?
Antiphospholipid antibody syndrome
This predisposes to both arterial and venous thrombosis.
How can antiphospholipid antibody syndrome manifest?
Recurrent miscarriage
Atherosclerotic disease in young patients.
Which part of haemostasis is affected in arterial thrombosis?
Primary haemostasis
There are also vessel wall abnormalities.
Which part of haemostasis is affected in venous thrombosis?
Secondary haemostasis
How does antiphospholipid antibody syndrome affect APTT?
Will be prolonged.
Looks like anticoagulation is given, despite patient having a raised thrombotic risk.
How is antiphospholipid antibody syndrome treated?
Give aspirin (for arterial thrombosis) AND warfarin (for venous thrombosis).
How does warfarin work?
Affects coagulation factor synthesis.
Specifically those made by vitamin K - II, VII, IX and X.
How does heparin work?
Acts to potentiate the body’s natural anticoagulant defences.
What is the main complication associated with heparin/warfarin therapy?
Bleeding
What is the target of anticoagulants?
Fibrin clot production.
What is the difference between arterial and venous thrombosis?
Arterial thrombosis occurs in a high pressure system, whereas venous thrombosis occurs in a low pressure system.
What natural anticoagulant is potentiated by heparin?
Antithrombin
This acts to maximise the effectiveness of this.
What can activate factor Xa?
Antithrombin
What is the difference between unfractionated heparin and LMWH?
Unfractionated heparin acts on antithrombin.
LMWH acts on factor V/Xa.
Is monitoring necessary on LMWH?
No, can use Xa assay if needed.
Is monitoring needed when on unfractionated heparin?
Yes, monitor APTT.
What is the heparin antidote?
Protamine sulphate
This completely reverses unfractionated heparin, with only a partial effect on LMWH.
Why is heparin not used long-term?
As it is given IV/SC - oral preparations are best long-term.
What is required for vitamin K absorption?
Bile salts
How does warfarin therapy affect protein C and protein S?
These have a short half-life, and are reduced in early warfarin therapy - this increases clotting risk during early therapy.
This is why heparin is always given alongside warfarin at the point of initiation for 5-7 days.
Where are the clotting factors formed?
The liver
What is used to measure clotting when taking warfarin?
INR
This is a standardised form of the PT.
What can be given to reverse warfarin?
Vitamin K
Given orally - takes 6 hours to work.
It is indicated if INR > 8.
What can be given in those with life-threatening bleeds?
Clotting factor concentrates.
Only indicated in an emergency.
What do DOACs do?
They inhibit factor Xa.
Some inhibit thrombin.
What is an example of a DOAC which acts on thrombin?
Dabigatran
What are examples of DOACs which act on factor Xa?
Edoxaban, rivaroxaban and apixaban.
What are antiplatelet drugs used to treat?
Arterial thrombosis.
These are platelet-rich clots.
What is an example of a widely used antiplatelet?
Aspirin
What is atherosclerosis?
Damage of arterial endothelium, with the recruitment of foamy macrophages.
Results in plaque formation.
What causes platelets to adhere to ruptured plaques?
Von Willebrand factor
How does aspirin work?
Inhibits cyclooxygenase, preventing the release of thromboxane A2, meaning none of this is released when the platelet is activated.
This prevents effective platelet aggregation.
How do clopidogrel and prasugrel work?
Block ADP.
how long before surgery should antiplatelet agents be stopped?
7 days.
This is due to the drug affecting platelets for their full lifespan.
In severe bleeding, what can be given?
Platelet transfusion
