Pathophysiology of thrombosis and embolism

Question 1

What is normal blood flow ?

Answer 1

Laminar

Question 2

What is stasis ?

Answer 2

Stagnation of flow

Question 3

What is turbulence ?

Answer 3

Forceful, unpredictable flow

Question 4

What are the causes of common defects in blood flow ?

Answer 4

Thromboembolism
Atheroma
Hyperviscocity
Spasm
External compression
Vasculitis vascular steal

Question 5

What is Virchow’s triad ?

Answer 5

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

Question 6

What does Virchow’s triad influence ?

Answer 6

Factors causing thrombosis

Question 7

What is the basic pathogenesis of thrombosis ?

Answer 7

Endothelial injury
Stasis or turbulent blood flow
Hypercoagubility of the blood

Question 8

What are lines of Zahn on a thrombus ?

Answer 8

Represent bands of fibrin (lighter) with entrapped white blood cells and red blood cells (darker)

Question 9

What causes the adherence of platelets ?

Answer 9

Loss of intimal cells and the exposure of collagen

Question 10

What traps red blood cells in a blood clot ?

Answer 10

Fibrin meshwork

Question 11

What is responsible for the propagation of thrombosis ?

Answer 11

Further turbulence and platelet deposition

Question 12

What is the relationship between atheroma and thrombosis ?

Answer 12

Arterial thrombosis most commonly superimposed on atheroma; Virchow’s triad

Question 13

What is an example of changes in blood vessel wall ?

Answer 13

Atheromatous coronary artery

Question 14

What is an example of changes in blood constituents ?

Answer 14

Hyperviscocity, post-traumatic hypercoagulability

Question 15

What is an example of changes in patterns of blood flow ?

Answer 15

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

Question 16

What do the consequences of thrombosis depend on ?

Answer 16

Site
Extend
Collateral circulation

Question 17

What are common clinical scenarios of thrombosis ?

Answer 17

DVT

Ischaemic limb disease

Question 18

What is the outcome of thrombosis ?

Answer 18

Resolution
Organisation/recanalization
Death
Propagation-> embolism

Question 19

What is an embolism ?

Answer 19

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

Question 20

What is an embolus ?

Answer 20

Detached intravascular solid, liquid or gaseous mass

Question 21

What is the most common type of emboli ?

Answer 21

Thromboembolism- dislodged thrombi

Question 22

What is a systemic/arterial thromboembolism ?

Answer 22

Mural thrombus
Aortic aneurysms
atheromatous plaques
Valvar vegetations
Venous thrombi - paradoxical emboli

Question 23

What are mural thrombi associated with ?

Answer 23

Myocardial infarction or left atrial dilation and atrial fibrillation

Question 24

Where can a systemic thrombus travel to ?

Answer 24

Wide variety of sites: lower limbs most common, brain and other organs

Question 25

What is the usual result of a systemic thromboembolism ?

Answer 25

Usually infarction
Consequences depend on vulnerability of affected tissues to ischaemia, calibre of occluded vessel, collateral circulation

Question 26

What is a venous thromboembolism ?

Answer 26

Originate from deep venous thromboses (lower limbs)

Most common form of thromboembolic disease

Question 27

Where do venous thromboembolism usually travel and occlude ?

Answer 27

Travel to the pulmonary arterial circulation, may occlude the main pulmonary artery, bifurcation or smaller arteries

Question 28

What are the possible consequences of thromboembolism ?

Answer 28

Depend on size of embolus: silent, pulmonary haemorrhage/infarction, right heart failure, sudden death
Multiple PE over time: pulmonary hypertension and right ventricular failure

Question 29

What are other types of embolism ?

Answer 29

Fat:
	- After major fractures
	- Syndrome of fat embolism: brain, kidneys, skin affected 
Gas:
	- Decompression sickness
	- N2 forms as bubbles which lodge in capillaries
Air embolus:
	- Head and neck wounds, surgery, CV lines 
Tumour:
	- Spread of tumour
Trophoblast:
	- Pregnant women- lungs 
Septic material:
	- E.g. Infective endocarditis 
Amniotic fluid:
	- Cause of collapse (+/- death) in childbirth
Bone marrow:
	- Fractures; CPR
Foreign bodies:
Intravascular cannula tips, sutures, etc

Question 30

What are risk factors for deep vein thrombosis and pulmonary embolism ?

Answer 30

Cardiac failure
Severe trauma
Burns
Post op
Post partum (following childbirth)
Nephrotic syndrome
disseminated malignancy
Oral contraceptive
Increased age
Bed rest/immobilisation
Obesity
Past medical history of deep vein thrombosis