Pathophysiology of Thrombosis and Embolism

Question 1

What effects the normal blood flow?

Answer 1

Pressure gradient, resistance, viscosity of blood, velocity and compliance

Question 2

What is normal blood flow described as?

Answer 2

Laminar

Question 3

What are the 2 types of abnormal blood flow?

Answer 3

Stasis - stagnation of flow
Turbulence - forceful and unpredictable flow

Question 4

What can cause defects in blood flow?

Answer 4

Thromboembolism
Atheroma
Hyper-viscosity, spasm, external compression, vasculitis and vascular steal

Question 5

What is Virchow’s Triad?

Answer 5

Changes in blood vessel wall
Changes in blood constituents
Changes in the pattern of blood flow
These are factors that cause thrombosis

Question 6

What is thrombosis?

Answer 6

Formation of solid mass from the constituents in blood within the vascular system
Due to Virchow’s triad

Question 7

What is an example of a change in vessel wall?

Answer 7

Atheromatous coronary artery

Question 8

What is the pathogenesis of thrombosis?

Answer 8

Endothelial injury
Stasis or turbulent blood flow
Hypercoagulability of the blood

Question 9

How does an atheroma lead to thrombosis?

Answer 9

Turbulent blood flow, loss of intimal cells and denuded plaque, collagen is exposed and platelets adhere, fibrin meshwork, RBCs trapped (lines of Zahn)
Further turbulence and platelet deposition - propagation

Question 10

How does hypercholesterolaemia cause thrombosis?

Answer 10

Change in blood constituents

Question 11

How does propagation of thrombus happen?

Answer 11

Thrombus causes more turbulent flow so causes more platelet deposition and fibrin

Question 12

What is an example of a change in the vessel wall causing thrombosis?

Answer 12

LV wall is thin so if MI can cause dilatation of ventricle
Neural thrombosis

Question 13

What are some examples in changes in the blood constituents?

Answer 13

Hyper-viscosity, post-traumatic hypercoagulability
Stasis - post op, economy class syndrome
Turbulence - atheromatous plaque and aortic aneurysm

Question 14

What do the consequences of a thrombus depend on?

Answer 14

Site
Extent
Collateral circulation

Question 15

What are some common clinical scenarios of thrombosis?

Answer 15

DVT, ischaemic limb and MI

Question 16

What are the outcomes for thrombosis?

Answer 16

Resolution
Organisation/ recanalisation (thrombolysis)
Death
Propagation and possible embolism

Question 17

Describe an embolism

Answer 17

Movement of abnormal material in the bloodstream and its impaction in a vessel which blocks its lumen

Question 18

What is an embolus?

Answer 18

Detached intravascular solid, liquid or gaseous mass

Question 19

What could be the sources for systemic/arterial thromboembolism?

Answer 19

Mural thrombus - MI, LA dilatation or atrial fibrillation
Aortic aneurysm, atheroma, valvular vegetations

Question 20

What is a paradoxical emboli?

Answer 20

Happens due to venous thrombi
If cardiac defect

Question 21

Explain systemic thromboembolism

Answer 21

Travel to wide variety of sites - lower limbs most common, brain..
Consequences depend on the vulnerability of tissues to ischaemia, occluded vessels and collateral circulation - usually infarction

Question 22

Explain venous thromboembolism

Answer 22

Originated from deep venous thromboses (lower limbs)
Most common form
Travels to pulmonary arterial circulation
Often multiple

Question 23

What happens if there is a big venous thromboembolism?

Answer 23

Can occlude main pulmonary artery and bifurcation -saddle embolus

Question 24

What are some consequences of venous thromboembolism?

Answer 24

Silent, pulmonary haemorrhage, infarction, right heart failure and sudden death

Question 25

What happens if there are multiple PE over time?

Answer 25

Pulmonary hypertension Right ventricular failure

Question 26

What are the risk factors for DVT and pulmonary thromboembolism?

Answer 26

Cardiac failure, severe burns, post-op/partum, nephrotic syndrome, disseminated malignancy, oral contraception, age, bed rest, obesity, PMH of DVT

Question 27

What is given to patients who are at risk of Thromboembolism or DVT?

Answer 27

Prophylaxis - TEDS, heparin (anticoagulation measures)

Question 28

What is a fat embolus?

Answer 28

Can happen after major fractures - fat breaks off Syndrome of fat embolism - brain, kidneys and skin affected

Question 29

Explain gas embolus

Answer 29

Decompression sickness if rise to surface too quickly N2 forms as bubbles which lodge in capillaries

Question 30

Explain air embolus

Answer 30

Head and neck wounds, surgery, and CV lines Air is introduced to bloodstream

Question 31

What is a tumour embolus?

Answer 31

Spread of tumour Tumour can break off and go into bloodstream and possibly grow as well as occlude

Question 32

When does trophoblast embolus occur?

Answer 32

In pregnant women - lungs Is very rare

Question 33

Describe amniotic fluid embolus?

Answer 33

Skin cells or keratin from baby can break off and usually go to lungs of mother Can be very serious for mother - cause collapsing

Question 34

What are some other types of embolus?

Answer 34

Bone marrow Foreign bodies Septic material

Question 35

What is rheumatic fever?

Answer 35

Is a disease of disordered immunity Is inflammatory changes in the heart, joints and sometimes neurological symptoms

Question 36

Who does rheumatic fever usually affect?

Answer 36

Children between 5-15 years Usually boys over girls

Question 37

What is the presenting features of rheumatic fever?

Answer 37

Flitting (painful) polyarthritis of large joints (wrists, elbows, knees and ankles) plus skin rashes and fever Pancarditis in acute phase and heart murmurs are common

Question 38

What is pancarditis?

Answer 38

Inflammation affecting the endocardium, myocardium and pericardium

Question 39

What infection are patients with rheumatic fever usually exposed to?

Answer 39

Group A beta-haemolytic streptococci infection

Question 40

How does strep. infection lead to rheumatic fever?

Answer 40

Strong antibody reaction to strep. - may cross react with unknown antigens in connective tissue Damage to heart tissue may be caused by combination of antibody-mediated and T-cell mediated reactions

Question 41

Explain an Aschoff Body

Answer 41

Seen in heart of acute rheumatic fever Focus of chronic inflammatory cells, necrosis and activated macrophages (antischkow cells)

Question 42

What are some causes of valvular heart disease?

Answer 42

Valvular stenosis Valvular incompetence/regurgitation Vegetations

Question 43

What is valvular stenosis?

Answer 43

Valve thickened/calcified and obstructs normal blood flow into chamber/ vessel

Question 44

What is valvular incompetence or regurgatation?

Answer 44

Valve loses normal function and fails to prevent reflux of blood after contraction of cardiac chamber

Question 45

What is vegetations?

Answer 45

Infective or thrombotic nodules develop on valve leaflets impairing normal valve mobility - may embolise

Question 46

What does chronic rheumatic heart disease usually manifest as?

Answer 46

Valvular abnormalities

Question 47

What does inflammation of endocardium and left sided valves result in?

Answer 47

Fibrinoid necrosis of valve or cusps/ chordae tendinea, over which form small vegetations

Question 48

Explain rheumatic heart disease?

Answer 48

Characterised by deforming fibrotic valvular disease - involving the mitral valve Typically leaflet thickening, commissural fusion and shortening, thickening and fusion of chordae tendineae

Question 49

What does rheumatic heart disease cause?

Answer 49

Mitral stenosis Mitral regurgitation is rare Aortic stenosis and regurgitation is rare Pulmonary valve and tricuspid is rare

Question 50

What is the appearance of mitral valve in rheumatic heart disease?

Answer 50

Fish mouth appearance Very thin and stenosed