Pathophysiology of Thrombosis and Embolism

Question 1

What word is used to describe normal blood flow?

Answer 1

Laminar.

Question 2

What are the two abnormal blood flows?

Answer 2

Stagnation - there is stagnation of flow.

Turbulence - forceful, unpredictable flow.

Question 3

What are the some common defects in blood flow?

Answer 3

Thromboembolism is common, other causes incl:

Atheroma, hyper viscosity, spasm, external compression vasculitis, vascular steal.

Question 4

What are the three points in Virchow’s Triad?

Answer 4

Changes in blood vessel wall
Changes in the blood constituents
Changes in the pattern of blood flow

Question 5

What is Virchow’s Triad?

Answer 5

Factors causing thrombosis.

Question 6

How does a thrombus differ from a clot?

Answer 6

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.

Question 7

Give an example of a change in the vessel wall that may lead to thrombus formation.

Answer 7

Atheromatous coronary artery.

Question 8

Describe what the histology of a thrombus looks like.

Answer 8

Fibrous cap and lipid core, some may have calcification within the plaque, or something obviously wrong with the vessel wall.

Question 9

Describe the aetiologies of thrombosis.

Answer 9

Endothelial injury, stasis or turbulent blood flow, hyper coagulability of the blood.

Question 10

Describe the pathogenesis of thrombosis.

Answer 10

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.

Question 11

When will thrombosis most commonly occur?

Answer 11

Arterial thrombosis most commonly superimposed on atheroma.

Question 12

What is meant by the propagation of a thrombus?

Answer 12

It gets bigger after it is formed. It keeps getting bigger in the direction of flow.

Question 13

Give examples of changes in the blood constituents that can lead to thrombosis.

Answer 13

Hyperviscosity, post-traumatic hyper-coagulability.

Question 14

Give examples of changes in the blood flow that could lead to thrombosis.

Answer 14

Stasis - economy class syndrome, post op. 
Turbulence - atheromatous plaque, aortic aneurysm.

Question 15

What do the consequences of thrombosis depend on?

Answer 15

Site, extent (partial or complete occlusion) and collateral circulation (can other vessels compensate?).
Common clinical scenarios - DVT, ischaemic limb, MI.

Question 16

What are the two best outcomes of thrombosis?

Answer 16

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).

Question 17

What are the two worst outcomes of thrombosis?

Answer 17

Death

Propagation leading to embolism.

Question 18

Define embolism.

Answer 18

Movement of abnormal material in the bloodstream and its impaction in a vessel, blocking its lumen.

Question 19

What is an embolus?

Answer 19

A detached intravascular solid, liquid or gaseous mass.

Question 20

What are the most emboli?

Answer 20

Dislodged thrombi (thromboembolism).

Question 21

What may be sources of a systemic or arterial thromboembolism?

Answer 21

Mural thrombus, aortic aneurysms, atheromatous plaques, valvular vegetations.

Question 22

What is a mural thrombus?

Answer 22

A thrombus formed on the endocardial layer of a heart chamber (associated with MI or left atrial dilation and AF)

Question 23

What is a paradoxical embolus?

Answer 23

An embolus carried from the venous system to the arterial system.

Question 24

Where do systemic thromboemboli commonly travel to?

Answer 24

Lower limbs most common, brain and other organs.

Question 25

What usually results from thromboemboli?

Answer 25

Infarction.

Question 26

What is the most common form of thromboembolic disease?

Answer 26

Venous thromboembolus.

Question 27

Where do venous thromboemboli originate?

Answer 27

Deep venous thromboses in the lower limbs.

Question 28

What do venous thromboemboli commonly do and what are the consequences of this?

Answer 28

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.

Question 29

What do multiple pulmonary embolisms over time lead to?

Answer 29

Pulmonary hypertension and right ventricular failure.

Question 30

What are the risk factors for DVT and pulmonary thromboembolism?

Answer 30

Cardiac failure, severe trauma/burns, post-op/post-partum, nephrotic syndrome, disseminated malignancy, OCP, increased age, bed rest/imbolisation, obesity, PMH of DVT.

Question 31

What is used for surgical patients at risk of DVT and PE?

Answer 31

TEDS, s/c heparin

Question 32

What are TEDS?

Answer 32

Thromboembolism deterrent stockings

Question 33

What does heparin do?

Answer 33

Blood thinner so reduces clotting and likelihood of thrombosis.

Question 34

When would you get a fat embolism?

Answer 34

After major fractures, syndrome of fat embolism - brain (confusion), kidneys, skin affected.

Question 35

When might you get a gas embolus?

Answer 35

In decompression sickness, as seen in scuba divers.

Nitrogen forms as bubbles which lodge in capillaries.

Question 36

When might you get an air embolus?

Answer 36

Head and neck wounds, surgery, CV lines.

Question 37

What are three other types of embolus?

Answer 37

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.