Thrombosis Flashcards
normal haemostasis
Well-regulated process that maintains blood in a fluid, clot free state in normal vessels and induces the rapid formation of a localised haemostatic plug at the site of vascular injury
Haemostasis and thrombosis are dependent on what three components
- Vessel wall
- Platelets
- Coagulation cascade
thrombosis
the inappropriate activation of blood clotting in an uninjured vessel/minimally injured vessel leading to the formation of a blood clot (thrombus) within the vascular system, which can obstruct the flow of blood
thrombus
an aggregate of coagulated blood containing platelets, fibrin and entrapped cellular elements.
virchows triad
change in surface - endothelial injury
change in flow - stasis and turbulence
change its constituents - hypercoagulability
where in the endothelial surface does thrombosis commonly occur and why
atheromatous plaques
Injury occurs due to HTN(Hypertension), turbulent
flow, radiation
results from -exposure of stroma, increased platelet adhesion
how does turbulent blood flow cause or influence thrombosis
Disrupted flow brings platelets into contact with
the endothelium
Prevent dilution of activated clotting factors by flowing blood
hypercoagulability
alteration of the coagulation pathways
-> predisposes to thrombosis
heritable hypercoagulability
Factor V leiden, protein c/protein s deficiencies,
prothrombin mutations
examples of Acquired Hypercoagulability
Oral contraceptives, pregnancy, malignancy,
nephrotic syndrome
sites of venous thrombus formation
– most commonly due to stasis in capillaries and heart
sites of arterial thrombus formation
most commonly superimposed on atheroma
capillaries and heart
causes of arterial thrombosis
Atheromatous plaque
Smokers
High cholesterol
causes of venous thrombosis
Blood pressure lower – atheroma does not occur
Most begin at valves – turbulence, stasis, occlusion
Venous return from the legs relies on calf muscle
contraction and relaxation
Any fall in blood pressure (e.g. during surgery) can
precipitate development
risk factors for venous thrombosis
Immobility Smoking Cancer Pregnancy Oestrogen therapy
Clinical effects of a arterial thrombus
Loss of pulse
Pale, cold
Painful
Death & gangrene of the affected limb/site
Clinical effects of a venous thrombus
- 95% occur in leg veins
- Tender
- Swollen
- Reddened
fate of a thrombus
Lysis and resolution Organisation - scar tissue Recanalization Propagation Embolization
Recanalization
– ingrowth of new vessel which eventually
join up to restore blood flow, at least partially
Propagation
enlarges leading to vessel obstruction
Embolization
dislodges, travelling to a different site
embolism
An embolus is a detached intravascular physical mass,
which is carried in the circulation until it reaches a vessel
too small to permit its further passage when occlusion
occurs
embolism that arise from a thrombus
thromboembolism
types of embolism
Fat Air or gas Thrombus Bacteria emboli Amniotic fluid Tumour fragments
