Pathophysiology of Thrombosis and Embolism Flashcards
What word is used to describe normal blood flow?
Laminar.
What are the two abnormal blood flows?
Stagnation - there is stagnation of flow.
Turbulence - forceful, unpredictable flow.
What are the some common defects in blood flow?
Thromboembolism is common, other causes incl:
Atheroma, hyper viscosity, spasm, external compression vasculitis, vascular steal.
What are the three points in Virchow’s Triad?
Changes in blood vessel wall
Changes in the blood constituents
Changes in the pattern of blood flow
What is Virchow’s Triad?
Factors causing thrombosis.
How does a thrombus differ from a clot?
A thrombus is the formation of a solid mass from the constituents of blood within the vascular system during life, a clot isn’t in the vascular system.
Give an example of a change in the vessel wall that may lead to thrombus formation.
Atheromatous coronary artery.
Describe what the histology of a thrombus looks like.
Fibrous cap and lipid core, some may have calcification within the plaque, or something obviously wrong with the vessel wall.
Describe the aetiologies of thrombosis.
Endothelial injury, stasis or turbulent blood flow, hyper coagulability of the blood.
Describe the pathogenesis of thrombosis.
Atheromatous coronary artery, turbulent blood flow (fibrin deposition, platelet clumping), loss of intimal cells, platelets adhere, fibrin meshwork, RBCs trapped, alternating bands - lines of Zahn .
Further turbulence and platelet deposition, propagation –> consequences.
When will thrombosis most commonly occur?
Arterial thrombosis most commonly superimposed on atheroma.
What is meant by the propagation of a thrombus?
It gets bigger after it is formed. It keeps getting bigger in the direction of flow.
Give examples of changes in the blood constituents that can lead to thrombosis.
Hyperviscosity, post-traumatic hyper-coagulability.
Give examples of changes in the blood flow that could lead to thrombosis.
Stasis - economy class syndrome, post op. Turbulence - atheromatous plaque, aortic aneurysm.
What do the consequences of thrombosis depend on?
Site, extent (partial or complete occlusion) and collateral circulation (can other vessels compensate?).
Common clinical scenarios - DVT, ischaemic limb, MI.
What are the two best outcomes of thrombosis?
1 - resolution, either thrombosis goes away itself, or fibrinolysis and RBCs broken down by fibrinolytic drugs.
2 - organisation/recanalisation - can get some blood flow restored. Thrombus controlled, smooth muscle deposition and fibrosis (granulation tissue laid down), can start to form lumina in the vessels).
What are the two worst outcomes of thrombosis?
Death
Propagation leading to embolism.
Define embolism.
Movement of abnormal material in the bloodstream and its impaction in a vessel, blocking its lumen.
What is an embolus?
A detached intravascular solid, liquid or gaseous mass.
What are the most emboli?
Dislodged thrombi (thromboembolism).
What may be sources of a systemic or arterial thromboembolism?
Mural thrombus, aortic aneurysms, atheromatous plaques, valvular vegetations.
What is a mural thrombus?
A thrombus formed on the endocardial layer of a heart chamber (associated with MI or left atrial dilation and AF)
What is a paradoxical embolus?
An embolus carried from the venous system to the arterial system.
Where do systemic thromboemboli commonly travel to?
Lower limbs most common, brain and other organs.
What usually results from thromboemboli?
Infarction.
What is the most common form of thromboembolic disease?
Venous thromboembolus.
Where do venous thromboemboli originate?
Deep venous thromboses in the lower limbs.
What do venous thromboemboli commonly do and what are the consequences of this?
Travel to pulmonary arterial circulation, and depending n size may occlude main pulmonary artery, bifurcation, smaller arteries.
Consequences depend on size of thromboembolism - silent, pulmonary haemorrhage/infarction, right heart failure, sudden death.
What do multiple pulmonary embolisms over time lead to?
Pulmonary hypertension and right ventricular failure.
What are the risk factors for DVT and pulmonary thromboembolism?
Cardiac failure, severe trauma/burns, post-op/post-partum, nephrotic syndrome, disseminated malignancy, OCP, increased age, bed rest/imbolisation, obesity, PMH of DVT.
What is used for surgical patients at risk of DVT and PE?
TEDS, s/c heparin
What are TEDS?
Thromboembolism deterrent stockings
What does heparin do?
Blood thinner so reduces clotting and likelihood of thrombosis.
When would you get a fat embolism?
After major fractures, syndrome of fat embolism - brain (confusion), kidneys, skin affected.
When might you get a gas embolus?
In decompression sickness, as seen in scuba divers.
Nitrogen forms as bubbles which lodge in capillaries.
When might you get an air embolus?
Head and neck wounds, surgery, CV lines.
What are three other types of embolus?
Tumour - spread of tumour?
Trophoblast in pregnant womans - can lodge in lungs.
Septic material, e.g. infective endocarditis.
Amniotic fluid (cause of collapse and/or death in childbirth, v rare 1 in 8-80 thousand. Causes allergic reaction and cardiomyopathy.
Bone marrow - fractures, CPR.
Foreign bodies - intravascular cannulae tips, sutures etc.
