Cardiovascular Pathology Flashcards
What is haemostasis?
- Occurs when there is damage to a blood vessel
– it involves the formation of a solid plug from the constituents of blood – it stops loss of blood from the circulation at the site of injury
– it is physiological (ie. it’s a good thing)
What factors determine haemostasis?
close interactions between the
- vessel wall
- platelets
- coagulation cascade
How does endothelial damage result in haemostasis?
- injury
- adhesion
- platelet aggregation
- formation of loose platelet plug
- Tissue factor expo
- intrinsic clotting cascade
- insoluble fibrin forms
- stable platelet plug (due to fibrin)
What is fibrinolysis?
activated by the same injury that initiates haemostasis
plasminogen -> plasmin
plasmin degrades insoluble fibrin into soluble products
ensures that haemostasis is very tightly isolated to the site of injury
(if this didn’t happen, then you would get DIC)
When does thrombosis occur?
following inappropriate activation of haemostasis
How does thrombosis occur?
- platelets and coagulation system interact with vessel wall
- thrombus forms
- process overwhelms the regulation on coagulation system (e.g. fibrinolysis etc)
What is a thrombus made up of?
same components as a haemostat plug
- platelets
- fibrin
- RBCs
However, it is PATHOLOGICAL
How does a clot differ from a thrombus?
Thrombus contains PLATELETS but a clot does not
technically, a clot is formed from stationary blood or outside the CVS e.g. post-mortem or in a test tube
What is Virchow’s triad?
[3 main predisposing factors to thrombus formation]
- endothelial injury
- abnormal flow (turbulent or static flow)
- hypercoagulability
What is the most important RF in ARTERIAL thrombosis?
atherosclerosis
What are the most important RFs in VENOUS thrombosis?
- stasis
- hypercoagulability
What are the 3 main outcomes of thrombi formation?
- PARTIAL occlusion at site of thrombosis
- COMPLETE occlusion at site of thrombosis
- EMBOLISM to a distant site and occlusion of that vessel
What is an embolism?
- occlusion of a vessel by undissolved material
- transported via the blood stream
What can partial or complete vessel occlusion by a thrombus cause?
ischaemia of the tissue supplied by that vessel
What is ischaemia?
- tissue dysfunction
- interference with blood flow
- reversible
What can occur if a vessel occlusion is not reversed?
ischaemia can progress to infarction
What is infarction?
- tissue death (necrosis)
- interference with blood flow to a tissue
- irreversible
What are the clinical effects of a vessel occlusion?
dependent on
- which vessel is occluded
- type of tissue supplied
What will thromboemoli originating in the VENOUS system go on to occlude?
a pulmonary artery
What will thromboemoli originating in the ARTERIAL system or LHS of heart go on to occlude?
a systemic artery
e.g. renal arteries
What initiates atherosclerosis?
- chronic inflammatory process
- initiated by endothelial injury
What are the established RFs for endothelial injury?
- smoking
- HTN
- DM
- dyslipidaemia
What are atherosclerotic plaques composed of?
core: lipid debris and foam cells and lymphocytes
roof: fibrous cap
By what mechanisms does atherosclerosis cause clinical disease?
- Gradual enlargement of a STABLE plaque -> luminal stenosis
- Sudden disruption of a VULNERABLE plaque + thrombosis in lumen
- > occlusion at that site
- > embolism at another site - Aneurysm formation
- > rupture
- > thromboembolism
