Thrombosis Flashcards
What kind of clot do you get in venous thrombosis?
fibrin rich (secondary haemostasis)
What is Virchow’s triad?
vessel wall damage (valve damage)
hypercoaguability
stasis
Give 2 examples of venous thromboses.
DVT
PE
What are risk factors for venous thrombosis?
age obesity pregnancy, oestrogen therapy, puerperium thrombophilia paralysis, immobility after surgery infection, malignancy previous DVT/PE
What are thrombophilias?
usually hereditary disorders
predisposing to thrombosis
What are the mechanisms of thrombophilias?
decreased natural anticoagulant activity
decreased fibrinolytic activity
increased coagulation activity
What are the naturally occurring anticoagulants?
protein C and S
antithrombin III
without these, you don’t switch off clotting as efficiently
What is an example of a thrombophilia that results in decreased anticoagulant activity?
Factor V Leiden
What is Factor V Leiden?
polymorphism meaning that protein C and S can’t switch off clotting as well as usual
When do you screen for hereditary thrombophilias?
VT <45 years
recurrent VT
unusual VT
family history of recurrent VT or thrombophilia
What is the management of thrombophilias?
advice on avoiding risk e.g. OCP
short term prophylaxis in period of known risk e.g. pregnancy
long term anticoagulation - if recurrent VT (have to balance risk of recurrent VT with haemorrhage)
What is an example of an acquired thrombophilia?
antiphospholipid antibody syndrome
What are the features of antiphospholipid syndrome?
recurrent thromboses
recurrent fetal loss
What is the treatment of antiphosphlipid syndrome?
aspirin (anti platelet) and warfarin (anticoagulation)
both as primary and secondary haemostasis is effected
In what type of thrombosis do you give anticoagulation?
venous
What are some examples of anticoagulant drugs?
warfarin
heparin
rivaroxiban, dabigitran
What type of clot do you get in arterial thromboses?
platelet rich
What is the treatment of arterial thromboses?
anti platelet drugs e.g. aspirin, clopidogrel
modify lifestyle
How do arterial thromboses form?
1 - damage to endothelium, recruitment of ‘foamy’ macrophages rich in cholesterol
2 - cholesterol rich plaque formed
3 - plaques can rupture (more likely in high pressure arteries), platelets recruited causing thrombosis
Give some examples of arterial thromboses.
MI, stroke
What are some risk factors for developing arterial thromboses?
hypertension
smoking
high cholesterol
diabetes
How can you prevent arterial thromboses?
smoking cessation treat hypertension treate diabetes lower cholesterol anti platelet drugs
What is the mechanism of action of aspirin?
inhibits cyclooxygenase (COX) necessary to produce thromboxane A2 (which further stimulates platelet activation)
What is the mechanism of action of clopidogrel?
ADP receptor antagonist
ADP, thromboxane A2, thrombin further stimulate platelet activation via ADP receptors
When should you stop anti platelet therapy before an operation?
7 days
How does heparin work?
potentiates antithrombin
immediate effect
How does warfarin work?
inhibits vitamin K epoxide reductase
blocks ability of vit K to carboxylate vit K dependent clotting factors
so inhibits factors 2,7,9,10
What has to be monitored with warfarin therapy\?
INR
What can reverse the effects of warfarin?
vit K
What are the pros and cons of newer anticoagulants?
don’t require monitoring
decreased drug interactions
no antidote for reversal
What is the mechanism of action of rivaroxiban?
direct factor Xa inhibitor (so is apixiban)
What is the mechanism of action of dabigatran?
direct thrombin inhibitor
What is the mechanism of action of dipyramidole?
decreased cAMP
How do you monitor LMWH?
anti Xa assay
How do you monitor unfractionated heparin?
APTT
How can you reverse heparin?
protamine sulphate
