Pathophysiology of Thrombosis & Embolism

Question 1

What is Laminar blood flow?

Answer 1

It is the normal condition for blood flow throughout most of the circulatory system.
- It is characterized by concentric layers of blood moving in parallel down the length of a blood vessel.

Question 2

What is blood stasis?

Answer 2

The slowing or pooling of blood

Question 3

What occurs when blood flow becomes turbulent?

Answer 3

• Blood does not flow linearly and smoothly in adjacent layers, but instead the flow can be described as being chaotic.

Question 4

Defects in blood flow

Answer 4

• Thromboembolism common
  Other causes:
• Atheroma
• Hyperviscosity, spasm, external compression, vasculitis, vascular steal

Question 5

The 3 features of Virchow’s Triad

Answer 5

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

Question 6

What is Virchow’s triad (meaning)?

Answer 6

Factors causing thrombosis

Question 7

What is the difference between a blood clot and a thrombus?

Answer 7

Blood clots are clumps that occur when blood hardens from a liquid to a solid.

• A blood clot that forms inside one of your veins or arteries is called a thrombus.
• A thrombus may also form in your heart.

-A thrombus that breaks loose and travels from one location in the body to another is called an embolus.

Question 8

Features of pathogenesis of Thrombosis

Answer 8

• Atheromatous coronary artery
• Turbulent blood flow (fibrin deposition, platelet clumping)
• Loss of intimal cells, denuded plaque
• Collagen exposed, platelets adhere
• Fibrin meshwork, RBCs trapped
• Alternating bands: lines of Zahn
• Further turbulence and platelet deposition
• Propagation
• Consequences

Question 9

What do the consequences of Thrombosis depend on?

Answer 9

• Site
• Extent
• Collateral circulation

Question 10

What does propagation of thrombosis lead to?

Answer 10

Embolism

Question 11

What is an embolism?

Answer 11

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

Question 12

Features of an embolus

Answer 12

• Detached intravascular solid, liquid or gaseous mass
• Most emboli are dislodged thrombi (thromboembolism)
• Factors causing embolism depend on type of embolus

Question 13

Types of embolus

Answer 13

• Systemic/Arterial thromboembolus
• Venous thromboembolus
• Fat
• Gas
• Air embolus
• Tumour
• Trophoblast
• Septic material
• Amniotic material
• Bone marrow
• Foreign bodies

Question 14

Features of Rheumatic fever

Answer 14

• Disease of disordered immunity
• Inflammatory changes in the heart and joints, sometimes neurological symptoms.
• Commonly affects children 5-15 years, boys > girls
• Pancarditis (inflammation affecting endocardium, myocardium, pericardium) in the acute phase; heart murmurs are common

Question 15

What are presenting features of rheumatic fever?

Answer 15

-Presenting feature: “flitting” (painful) polyarthritis of large joints (wrists, elbows, knees, ankles) plus skin rashes and fever.

Question 16

Why do most patients have a recent sore throat in rheumatic fever?

Answer 16

Usually due to group A beta-haemolytic streptococcal infection

Question 17

What is damage to heart tissue in rheumatic fever caused by?

Answer 17

May be caused by combination of antibody-mediated and T cell-mediated reactions

Question 18

What are Aschoff bodies?

Answer 18

Nodules found in the heart of individuals with acute rheumatic fever.

• Focus of chronic inflammatory cells, necrosis and activated macrophages (Anitschkow cells)
• They result from inflammation in the heart muscle.

Question 19

What is Valvular heart disease?

Answer 19

It is any disease process involving one or more of the four valves of the heart
- (the aortic and bicuspid on the left side of the heart and the pulmonary and tricuspid valves on the right side of the heart)

Question 20

What are pathological problems that cause valvular heart disease?

Answer 20

• Valvular stenosis: valve thickened/calcified and obstructs normal blood flow into chamber/vessel.
• Valvular incompetence/regurgitation/incompetency: valve loses normal function and fails to prevent reflux of blood after contraction of cardiac chamber.
• Vegetations: infective or thrombotic nodules develop on valve leaflets impairing normal valve mobility; may embolise.

Question 21

What can Pancarditis in acute rheumatic fever progress to?

Answer 21

It can progress over time to chronic rheumatic heart disease, mainly manifesting as valvular abnormalities.

Question 22

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

Answer 22

It results in fibrinoid necrosis of the valve cusps/chordae tendinae, over which (and along line of closure) form small vegetations.

Question 23

What is rheumatic heart disease mainly characterised by?

Answer 23

It is characterised principally by deforming fibrotic valvular disease, particularly involving the mitral valve: typically leaflet thickening, commissural fusion and shortening, thickening and fusion of chordae tendinae.

Question 24

What can Rheumatic heart disease cause?

Answer 24

• Virtually the only cause of mitral stenosis
• Can cause mitral regurgitation but now most comonly due to ischaemic heart disease.
• Now only rarely causes aortic stenosis: most due to calcific aortic valve disease.
• Potntially still causes aortic regurgitation /incompetence.
• Tricuspid valve involvement infrequent: pulmonary valve involvement rare.

Question 25

What is the typical thing seen in rheumatic heart disease?

Answer 25

Mitral stenosis