9 - Thrombosis and Embolism Flashcards
What is the definition of a thrombosis?
Solid mass of blood within vessels or the heart (circulatory system)
What is Virchow’s triad?
- Thrombosis depends on three things: changes in vascular wall, blood flow and changes in blood
- Only need two of three for thrombosis
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Why are you at risk of thrombosis in pregnancy?
- Hypercoagulable blood and stasis due to pressure on large veins of pelvis by uterus
Give some examples of endothelial damage and how they can cause a thrombus?
- Hypertension, scarred heart valves all are causing endothelial damage and if blood flow is slow not swift, thrombus will form
- This is due to vWF being exposed
Why does slow or turbulent flow lead to thrombosis?
- Gives platelets better chance to stick to endothelium and for clotting factors to accumulate
- Can damage endothelium leading to two of three of Virchow’s triad
- More likely to occur in veins and blood flow is slower
What are some conditions that lead to hypercoagulability of the blood?
- Smoking
- Pregnancy
- Post-op
- OC pill
- Inherited disorders
How would you describe this thrombus and where is it most commonly found?
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- Platelets aggregate at the endothelium as they are small so carried along outside
- Lines of Zahn: white layer of platelets crosslinking by fibrin with red layer of red blood cells
- More obvious in arterial thrombi as blood flows over surface
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What do thrombi look like post mortem?
- Not laminated
- Rubbery and shiny and not attached to intima
- Need to be able to distinguish if cause of death or not
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What is thrombophlebitis?
Painful superficial thrombi in veins that have inflammation in the wall of the vein
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What are the two classification of thrombi?
- Parietal: attached to wall of vessels and restrict lumen
- Occlusive: fill and completely obstruct lumen. mainly occurs over atheroscelrotic plaque
What is a thrombus on a heart valve called and what is the complications with it?
- Vegetation
- Easily embolises
- Can become infected, particularly in IV drug users due to microtrauma
- Mainly form on left heart valve because higher pressures and more microtrauma
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What are the different outcomes of thrombi?
- Resolution: dissolved by lysis
- Propagation: thrombus grows
- Organisation: thrombus undergoes fibrous repair and forms scar on vessel wall
- Recanalisation: new channels run through occluding thrombus to restore blood flow but less blood than original can flow through
- Embolism: particularly in large veins of lower limb are dangerous when part of thrombus breaks off, thrombo-emoblism
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Why do thrombi propagate as they move through veins?
- Veins get larger as you move upwards towards the heart
- Stagnation in the blood above the clot and when tributaries join they join abnormal flow so contribute to clot
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What are the effects of thrombosis?
- Ischaemia and infarct due to occlusion
- Embolisation
- Congestion and oedema leading to pain and skin ulceration
- Repeated miscarriages due to thrombosis in uteroplacental often seen in inherited thrombophilias
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What is an embolism?
Blockage of a blood vessel by solid, liquid or gas at a site distant from its origin due to blood current
e.g air, amniotic fluid, nitrogen, thromboemboli, body fat, medical equipment
![](https://s3.amazonaws.com/brainscape-prod/system/cm/379/746/676/a_image_thumb.png?1550256509)
Why can’t embolism occur in veins?
- Blood flows from smaller to larger vessels, therefore they will go to right heart and embolise in pulmonary arteries