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
Embolism
Transference of abnormal material that impacts material in distal vessel Thrombus and cancer Different effects depends on where it originates from
Thrombus in artery or left side of heart embolism
Brain arteries- stroke Lower limb arteries- gangrene of legs Mesenteric arteries- bowel necrosis Renal arteries- kidney infarction Splenic artery- splenic infarction
Thrombus in systemic vein leads to
PE Small: small peripheral lung infarct Large: sudden death
Venous thrombosis embolism risk assessment
Active cancer/ treatment Age >60 Dehydration Known thrombophilias Obesity One or more sig. medical comorbidities (heart disease, infectious disease, inflammatory, metabolic/ respiratory/ endocrine pathology) Personal/ 1st degree relative with history of VTE Use of hormone replacement therapy Use of oestrogen containing contraceptive Varicose veins with phlebitis Pregnancy/ 6 week post partum reduces flow to body due to flow to amniotic sac
Fat embolism
After trauma- fat in bone marrow goes to bloodstream After joint replacement surgery
Nitrogen embolism
Increase pressure, gas increases in blood, more nitrogen so gas particles come on out blood and block arteries
Air embolism
IV Mouse syringe Air in veins causes vessels in lungs to constrict increasing pressure in right side
Amniotic embolism
Misuse syringe during abortions Amniotic fluid enters mothers bloodstream and effects clotting mechanism
