Thrombosis and Embolism

Question 1

Define laminar, stasis and turbulence.

Answer 1

L - normal blood flow.
S - stagnation of flow.
T - forceful and unpredictable flow.

Question 2

What causes defects in blood flow?

Answer 2

Thromboembolism - common.
Atheroma, hyperviscosity, spasm, external compression, vasculitis, vascular steal.

Question 3

What is Virchow’s Triad?

Answer 3

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

Question 4

What is thrombosis?

Answer 4

A solid mass from the constituents of blood within the vascular system.
Caused by changes in Virchow’s Triad.

Question 5

What is the pathogenesis of thrombosis?

Answer 5

An atheromatous artery causes turbulent blood flow, which causes fibrin deposition and platelet clumping.
The plaque becomes denuded and collagen is exposed, which platelets adhere to.

Question 6

How do platelets cause thrombus propagation?

Answer 6

A fibrin meshwork is laid down and traps RBCs (forms lines of Zahn).
Further turbulence and platelet deposition occur, leading to thrombus propagation and clinical consequences.

Question 7

What is the relationship between atheroma and thrombosis?

Answer 7

Hypercholesterolaemia is a risk factor for atheroma and a part of Virchow’s Triad.
Arterial thrombosis is most commonly superimposed on atheroma.

Question 8

How is thrombosis linked to Virchow’s Triad?

Answer 8

Hyperviscosity or hypercoagulability.
Stasis of blood flow.
Turbulence (plaque, aortic aneurysm).

Question 9

What are the consequences of thrombosis?

Answer 9

Depends on site, extent and collateral circulation. Common clinical scenarios include DVT, ischaemic limbs, and MI.

Question 10

What is the progression of thrombosis?

Answer 10

Resolution.
Organisation and recanalisation.
Death.
Propagation - leads to embolism.

Question 11

What is embolism?

Answer 11

Movement of abnormal material in the blood and its impaction in a vessel, blocking its lumen. A detached intravascular mass. Most emboli are dislodged thrombi (thromboembolism).

Question 12

What causes systemic thromboembolism?

Answer 12

Mural thrombus (associated with MI, or left atrial dilatation and AF).
Aortic aneurysms.
Atheromatous plaques.
Valvular vegetation.
Venous thrombi.

Question 13

What are the movement and consequences of systemic thromboembolism?

Answer 13

Travels to the lower limbs (most common), brain, and other organs.
Consequences depend on the vulnerability of affected tissues to ischaemia; the calibre of occluded vessel; and collateral circulation. Usually infarction occurs.

Question 14

What is venous thromboembolism?

Answer 14

From deep venous thromboses (lower limbs).
Travels to the pulmonary arterial circulation.
May occlude main pulmonary arteries, bifurcations (saddle emboli), or smaller arteries - depends on size. Often multiple.

Question 15

What are the consequences of venous thromboembolism?

Answer 15

Silent, pulmonary haemorrhage/infarction, right heart failure, or sudden death - depends on size.
Multiple pulmonary emboli cause pulmonary hypertension and right ventricular failure.

Question 16

What are the risk factors for DVT and PTE?

Answer 16

Cardiac failure.
Severe trauma and burns.
Post-operation / post-partum.
Nephrotic syndrome.
Disseminated malignancy.
Oral contraceptive.
Age.
Bed rest / immobilisation.
Obesity.
PMH of DVT.

Question 17

What are the different types of embolus?

Answer 17

Fat - affects the brain, kidneys and skin.
Gas - N2 forms as bubbles in capillaries.
Air - from head and neck wounds, surgery.
Tumour.
Trophoblast - pregnant women.
Septic material - infective endocarditis.
Amniotic fluid - cause of collapse in childbirth.
Bone marrow - fractures and CPR.
Foreign bodies - cannulae tips, sutures.

Question 18

What is rheumatoid fever?

Answer 18

A disease of disordered immunity.
Inflammatory changes in the heart and joints (sometimes neurological symptoms).
Commonly affects 5-15yr olds, M>F.

Question 19

What are the symptoms of rheumatoid fever?

Answer 19

Flitting polyarthritis of large joints, skin rashes, fever.
Sore throat (Group A beta-haemolytic streptococcal infection).
Strong antibody reaction to strep, may cross-react with antigens in CT.

Question 20

What are the signs of rheumatoid fever?

Answer 20

Pancarditis (inflammation of the -cardium) in the acute phase, heart murmurs.
Damage to heart tissue may be caused by a combination of T Cell mediated and antibody-mediated reactions.

Question 21

What is an Aschoff Body?

Answer 21

Seen in the heart in acute rheumatic fever.
Focus of chronic inflammatory cells, necrosis and activated macrophages.

Question 22

What causes valvular heart disease?

Answer 22

Valvular stenosis - valve thickening or calcifying.
Valvular incompetence - valve loses normal function.
Vegetations - infective or thrombotic nodules develop on valve leaflets, impairing normal valve mobility. Can embolise.

Question 23

What is rheumatic heart disease?

Answer 23

Pancarditis in acute rheumatic fever can progress to chronic rheumatic heart disease, mainly manifesting as valvular abnormalities.

Question 24

How are the valves affected in rheumatic heart disease?

Answer 24

Inflammation of the endocardium and left sided valves - fibrinoid necrosis of the valve cusps or chordae tendineae.
Small vegetations form over them.

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

Question 25

What specific valves are affected in rheumatic heart disease?

Answer 25

Virtually the only cause of mitral stenosis.
Can cause aortic/mitral regurgitation.
Rarely causes aortic stenosis.
Tricuspid valve involvement is infrequent.
Pulmonary valve involvement is rare.