Vascular Disease- Thrombosis And Embolism Flashcards
Thrombosis
Process leading to formation of thrombus
Thrombus
Solid mass composed of blood constituents which have aggregated together in flowing blood in lumen of blood vessel
Thrombosis is a…
Normal mechanism to prevent bleeding when vessel wall is bleached Limited by fibrinolysis
When does thrombosis become pathological
When it is not controlled by fibrinolysis
Normal thrombosis
Vessel wall is breached Circulating platelets aggregate plug gap Platelets release factors trigger coagulation cascade Converts fibrinogen to fibrin Bind together platelets and trap red and white cells
Normal fibrinolysis
Fibrin holds thrombus together If fibrin breaks down it dissolves Plasmin active enzyme fragments fibrin Fragments to fibrin degradation products Plasminogen to Plasmin (tissue plasminogen activator secreted by endothelial cells) When fibrin is formed- plasminogen and t-PA binds (converted to Plasmin) Controls size of thrombus
When does a pathological thrombosis occur?
When thrombus enlarges beyond vessel healing requirements and continues to grow Fibrinolytic system can not control
How would a thrombus grow
Layer upon layer Reddish brown mass produced in vessel lumen
D- dimer test
Are a breakdown product of fibrin mesh Stabilised by factor XIII Risen in other inflammatory conditions Shows degree of fibrinolysis therefore thrombosis
When can d dimers also be raised
Pneumonia or cellulitis of legs Work out if someone has DVT
What factors predispose thrombus formation?
Virchow’s triad 1. Damage to vessel wall (endothelium) 2. Stasis (slow/ turbulent blood flow) 3. Change in character of blood (increased platelets, red cell numbers and viscosity)
Where does thrombosis occur
ARTERIES: vessel wall damage VEINS: stasis HEART: ventricles, atrium, heart valves
What happens to thrombus?
Lysed by intrinsic fibrinolysis Block lumen Organisation and recanalisation Propagate Thrombo embolism
What happens when a thrombus occluded a vessel?
Artery- infarction Vein- congestion and infarction (haemorrhage)
Organisation
New vessel grow into thrombus Vascular granulation tissue develops Fibroblast invade and deposit collagen Fibrovascular granulation tissue develops Recanalisation: sometimes vessel link up
