Thrombosis, Embolism and Infarction Flashcards
(40 cards)
What is a thrombus?
A solidification of blood contents that forms within the vascular system during life.
What three factors contribute towards thrombosis?
- Endothelial injury
- Abnormal blood flow
- Hypercoagulability
After injury to a vessel, what three important reactions do platelets undergo?
- Adhesion
- Secretion
- Aggregation
Explain the pathogenesis of thrombosis in terms of endothelial injury.
- endothelium is damaged. Matrix of injured vessel causes vasoconstriction to make the gap smaller.
- Platelets adhere to exposed collagen and in doing so, change their shape to a brick-like structure allowing them to accumulate and release granules.
- Granules released into the lumen causing further platelet recruitment.
- Fibrin acts as a glue between platelets and RBCs and WBCs get trapped in the fibrin mesh.
- If this is continued, it could be detrimental and so plasminogen is released to dissolve the clot.
What are the two types of blood flow?
- Turbulence (blood flows in all directions causing the alteration of blood flow. This can happen in arteries and also in the lumen of he heart. It contributes towards the development of arterial and cardiac thrombi.)
- Stasis (instead of laminar blood flow through the vessel, blood is very slow and this is a particular cause of DVT.)
What is hypercoagulability?
An alteration of the blood coagulation mechanism that, in some way, predisposes thrombosis.
What are primary (genetic) risk factors for hypercoagulability?
- mutation in factor V gene (Lieden mutation)
- antithrombin II deficiency
- protein C and S deficiency
What are secondary (acquired) high risk factors for hypercoagulability?
- bed rest
- MI
- tissue damage
- prosthetic valve
- DIC
etc.
What are the secondary (acquired) low risk factors for hypercogulability?
- oral contraceptive
- smoking
- sickle cell anaemia
- cardiomyopathy
etc.
What is the function of Von Willebrand’s factor?
Adheres platelets to exposed collagen in damaged endothelial wall
What is the function of GPIIB and GPIIIA?
Attach platelets to each other
What is the function of GPIB?
Attaches platelets to VW factor
What is the name of being deficient in GPIIIA/GPIIB?
Glanzmann’s thrombasthenia
What is the name of being deficient in GPIB?
Bernard Soulier syndrome
What is the result of Von Willebrand’s disease, Glanzmann’s thrombasthenia and bernard soulier syndrome?
Lack of blood clotting
What are the clinical features of arterial thrombosis?
loss of pulses distal to thrombus, area becomes perishing (cold, pale, painful) and eventually tissue dies and gangrene results. Gangrene can lead to autoimmune amputation.
What are the clinical features of saphenous venous thrombosis?
congestion, swelling, pain, tenderness (rarely embolise).
What are the clinical features of deep venous thrombosis?
foot and ankle oedema, Homan’s sign, could be asymptomatic and only realise once embolised.
What is the treatment for venous thrombosis?
Stocking are used as prevention as they push venous flow towards the heart.
Anticoagulant drugs aim to prevent growth of clot or embolism.
Heparin and Warfarin are commonly used anticoagulant drugs. Heparin is always used first as it is IV whereas warfarin is oral and therefore the effects of heparin are immediate.
What are the three types of thrombi in the CV system?
- Mural
- Arterial
- Venous
Describe the morphology of mural thrombi.
in chambers of the heart and aorta and are applied to one wall of underlying structure, occur in capacious lumina of chambers and aorta.
Describe the morphology of arterial thrombi.
in arteries usually occlusive and may be mural. Frequently in coronary, cerebral and femoral arteries. They are grey-white and friable.
Describe the morphology of venous thrombi.
in veins, invariably occlusive and dark red, affects veins and lower extremities (90%). Thrombophlebitis = inflamed and thrombosed.
What is the histological appearance of thrombi?
dark bands = RBCs
pale bands = fibrin and platelets
There are laminations called the lines of Zahn (red and white lines)
