thrombotic disorders Flashcards
what are the 3 elements of haemostasis
1y haemostasis
blood coagulation
fibrinolysis
3 parts of 1y haemostasis
vasoconstriction - at the site of endothelial insult
platelet adhesion - to exposed sub-endothelial collagen through GP Ia
platelet aggregation - through release of thromboxane and subsequently ADP
what triggers 1y haemostasis
tissue damage
2 main parts of coagulation
insoluble fibrin formation
fibrin cross linking
what is a thrombus
clot that arises in the wrong place
what is thromboembolism
movement of clot along a vessel
virchow’s triad
stasis
hypercoagulability
vessel damage
–> thrombosis
examples when components of virchow’s triad may be upset
stasis - bed rest, travel
hypercoagulability - pregnancy, trauma
vessel damage - atherosclerosis
3 main types of thrombosis
arterial
venous
microvascular
what is an arterial clot
‘white clot’ - platelets and fibrin
results in ischaemia and infarction
2y to atherosclerosis
examples of arterial thromboembolism
coronary thrombosis - MI, unstable angina
cerebrovascular TE - stroke, TIA
peripheral embolism - acute limb ischaemia
risk factors for arterial thrombosis
age smoking sedentary lifestyle HT DM obesity hypercholesterolaemia
FHx
management of arterial thrombosis
1y prevention - lifestyle modification, treatment of vascular risk factors
acute presentation - thrombolysis, anti-platelet/anticoagulant drugs
2y prevention - treatment of identified risk factors
what is a venous thrmobus
‘red thrombus’ - fibrin and red cells
results in back pressure
principally due to stasis and hypercoagulability
examples of venous thromboembolism
limb DVT PE visceral venous thrombosis intracranial venous thrombosis superficial thrombophlebitis - superficial veins
risk factors for venous thrombosis
stasis/hypercoagulability: increasing age pregnancy Hormonal therapy - HRT/COCP tissue trauma immobility surgery obesity systemic disease FHx
systemic disease linked to venous thrombosis
cancer myeloproliferative neoplasm (MPNs) AI disease: - IBD - connective tissue disease e.g. SLE - antiphospholipid syndrome: arterial and venous thrombosis
diagnosis of venous thrombosis
pretest probability scoring: Wells score, Geneva score
lab testing if pretest probability low - D dimer
imaging if low pretest probability but +ve D dimer; pts w/ high pretest probability go straight to imaging
imaging for venous thrombosis
doppler US for upper and lower limb veins
long images and suspected PE: V/Q scan, CT pulmonary angiogram - gold standard for PE
why is CT pulmonary angio gold standard for imaging PE
gives you detail on the clot pattern as well as whether there is evidence of right heart strain and anatomical detail
aims of management for venous thrombosis
prevent clot extension
prevent clot embolisation
prevent clot recurrence in long term treatment
drug treatment for venous thromboembolism
anticoagulants - LMWH, coumarins (warfarin), DOACs (prevent clot extending but don’t break down the clot)
thrombolysis only in selected cases e.g. massive PE (streptokinase, tenecteplase, alteplase)
heritable thrombophilia
common:
factor V Leiden
prothrombin G20210A
rare:
antithrombin deficiency - highest thrombogenicity
protein C deficiency
protein S deficiency
factor V Leiden and pathway
in the presence of thrombin, protein C is activated (promoted by thrombomodulin)
activated protein C w/ protein S subsequently inhibits activated factor VIII and V
