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Cardio > Pathophysiology of thrombosis & embolism > Flashcards

Pathophysiology of thrombosis & embolism Flashcards

1
Q

Normal blood flow is Laminar

What does this mean?

A

When a fluid flows in parallel layers, with no disruption between the layers

The central layer of fluid moves fastest, with the peripheral layer flowing slowest

With blood in larger vessels, the inner layer is where the cells mainly are, and plasma is on the outside

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2
Q

What determines the velocity of flow of blood?

A

Pressure gradient
Resistance
Viscosity
Compliance

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3
Q

What are the two big types of abnormal flow?

A

Stasis - stagnation of blood flow

Turbulence - forceful, unpredictable flow

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4
Q

What medical conditions/things cause abnormal flow?

A 
Thromboembolism 
Atheroma 
Hyperviscosity 
Spasm 
External compression
Vasculitis 
Vascular steal
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5
Q

What is Virchow’s triad?

A

3 factors that contribute to thrombosis:

  • Changes in vessel walls
  • Changes in blood constituents
  • Changes in the pattern of blood flow
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6
Q

What actually is thrombosis?

A

Formation of a solid mass from the constituents of blood within the vascular system during life

Not a clot

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7
Q

Give an example of ‘changes of the vessel wall’

A

Atheroma

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8
Q

Give examples of ‘changes in the blood constituents’

A

Hypercholesterolaemia

Thrombophilia or post operative hypercoagulability

Hyperviscosity

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9
Q

Give an example of ‘changes in the blood flow’

A

Turbulence:

  • Atheroma
  • Stenosis
  • Aortic aneurism

Stasis:

  • Post-op
  • Being stationary for ages

(overlap between vessel wall changes and blood flow changes)

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10
Q

How would a ruptured plaque cause thrombosis?

A

Ruptured plaque ∴ exposed collagen & tissue factors

Tissue factors = thrombin formation
Thrombin = fibrin formation

Fibrin meshwork created ∴ platelets adhere to fibrin and thrombus forms

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11
Q

A thrombus has alternating light and dark bands

What are these and what causes them to form?

A

Lines of Zahn

When thrombus forms:

  • Platelets adhere to fibrin creating ‘platelet plaque’
  • Platelet plaque traps RBC’s
  • Stagnant RBC’s ∴ another plaque forms behind it
  • RBC’s trapped behind second plaque
  • So on & so on…

Light bands = fibrin & platelet mixture
Dark bands = RBC’s

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12
Q

What determines the consequences of a thrombosis?

A

Site
Extent
Effects on collateral circulation

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13
Q

What are the main clinical presentations of thrombosis?

A

Deep vein thrombosis - DVT
Ischaemic limb
Myocardial infarction

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14
Q

What is the worst thing that a thrombus can do…

A

Embolise

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15
Q

What is embolism?

A

Movement of abnormal material in the bloodstream and it’s impaction in a vessel, blocking it’s lumen

An embolus is a intravascular detached solid, liquid or gaseous mass

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16
Q

What are the types of embolus?

A 
Systemic/arterial thromboembolus 
Venous thromboembolus 
Fat embolism 
Gas embolism 
Air embolism 
Tumour embolism 
Trophoblast embolism 
Septic material embolism 
Amniotic fluid 
Bone marrow 
Foreign bodies
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17
Q

What are the sources of a systemic/arterial thromboembolism?

A

mural thrombus (associated with MI or left atrial dilatation + AF):

  • aortic aneurysms
  • atheromatous plaques
  • valvular vegetations

Mural = endocardial lining or lining of a large BV

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18
Q

What generally happens when a arterial/systemic thrombus embolises?

A

Travels to wide variety of sites:
Lower limbs, brain, other organs most common

Consequences depend on site & size of thrombus but usually, infarction of the tissue occurs

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19
Q

What is a venous thromboembolus?

A

Most common form of thromboembolus

Originates in deep veins of the lower limbs - DVT

Usually embolises to pulmonary circulation and may occlude pulmonary artery, the bifurcation or smaller arteries depending on size

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20
Q

What are the possible effects of a venous thromboembolism?

A

Pulmonary haemorrhage/infarction
Right heart failure
Sudden death
May be silent

Multiple PE over time:

  • Pulmonary hypertension
  • Right ventricular failure
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21
Q

What medical procedures or conditions increase risk of DVT & pulmonary thromboembolism?

A 
Cardiac failure 
Severe trauma/burns 
Post op (+bed rest) 
Post partum 
Nephrotic syndrome 
Disseminated malignancy 
Obesity 
Old age
22
Q

What medication increases risk of DVT & PT?

A

Oral contraceptives

23
Q

A surgical patient is identified as high risk for DVT.

What is the next step?

A

Prophylaxis:

  • TEDS
  • s/c Heparin
24
Q

What would cause a fat embolism to occur?

A

Major fractures

25
Q

What is the effect of a fat embolism?

A

Syndromes affecting the brain, kidneys and/or skin

26
Q

What type of embolism are divers scared of?

A

Decompression sickness (the bends)

This occurs when Nitrogen gas forms in the blood and lodges into capillaries

27
Q

What would cause an air embolus to form?

A

Head and neck wounds
Surgery
CV lines (catheters)

28
Q

Who is at risk of trophoblast embolisms?

A

Pregnant women

- embolises to lungs

29
Q

Give an example of septic material embolism?

A

Infective endocarditis

30
Q

What is the risk caused by amniotic fluid embolism?

A

Collapse and sometimes death in childbirth

31
Q

What can cause bone marrow embolism?

A

Fractures:

CPR

32
Q

When are you most at risk of having a foreign body embolism?

A

When you’re in hospital

FB embolisms are generally intravascular cannulae tips & sutures that get stuck

33
Q

What is rheumatic fever?

A

Disease of disordered immunity caused through complications of untreated throat infection by group A strep bacteria

Characterised by inflammatory changes in the heart & joints, and sometimes neurological symptoms

34
Q

Where is rheumatic fever most common?

A

India
Middle east
Africa

Rare in Europe and N america

35
Q

How would someone with rheumatic fever typically present?

A

Boys > girls
5-15 years old

  • Flitting (painful) polyarthritis of large joints
  • Skin rashes
  • Fever

Acute phase:

  • Pancarditis:
  • Heart murmurs
36
Q

What is pancarditis?

A

Acute phase symptom of rheumatic fever:
Inflammation of endocardium, myocardium and pericardium

Causes heart murmurs

Can cause progression to chronic rheumatic heart disease

37
Q

Patients with rheumatic fever often have had a sore throat.

Why is this?
Why does it lead to the symptoms seen with rheumatic fever?

A

Group A strep infection of throat

Strong antibody reaction to strep
Antibodies produced may cross react with antigens on connective tissue

Damage to the heart may be caused by antibody and T-cell mediated damage

Hence - it is autoimmune

38
Q

What is a histological sign of acute rheumatic fever?

A

Aschoff bodies on the heart

Focus of chronic inflammatory cells, necrosis and activated macrophages (Anitschkow cells)

39
Q

What three things can lead to valvular heart disease?

A

Valvular stenosis
Valvular incompetence
Vegetations

40
Q

What is valvular stenosis?

A

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

41
Q

What is valvular incompetence?

A

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

causes regurgitation of blood

42
Q

What is vegetation?

A

infective or thrombotic nodules develop on valve leaflets impairing normal valve mobility; may embolise

43
Q

Pancarditis in acute rheumatic fever can progress over time to ___________

A

Chronic rheumatic heart disease

44
Q

Chronic rheumatic heart disease is mainly associated with problems of which part of the heart?

A

The valves

45
Q

Describe how CRHD affects the valves of the heart

A

Inflammation of the endocardium and left sided valves results in fibrinoid necrosis of the valve cusps/chordae tendineae, over which (and along line of closure) form small vegetations

46
Q

What are the overall effects of the vegetations formed chronic rheumatic heart disease?

A

typically leaflet thickening, commissural fusion and shortening, thickening and fusion of chordae tendineae

This causes deforming fibrotic valvular disease, particularly involving the mitral valve

Overall effect = mitral stenosis

47
Q

Link CRHD with mitral stenosis

A

CRHD is virtually the only cause of mitral stenosis

48
Q

Link CRHD with mitral regurgitation

A

Can sometimes cause mitral regurgitation

However, this is more commonly caused by Ischaemic heart disease

49
Q

Link CRHD with aortic stenosis and regurgitation

A

Rarely causes aortic stenosis:
This is commonly caused by calicified aortic valve disease

Potentially still causes aortic regurgitation/incompetence

50
Q

What is the involvement between CRHD and the tricuspid or pulmonary valves?

A

Rare involvement

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