Pathophysiology of Thrombosis and Embolism Flashcards by Lucy Jefford

What is blood flow?

The amount of blood moved per unit of time

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What is normal blood flow described as being?

Laminar

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What can affect blood flow?

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

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RECAP- what affects resistace?

Diameter of a blood vessel

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Name the two types of abnormal blood flow.

Stasis
Turbulence

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What is meant by a stasis blood flow?

Stagnation of the blood flow

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What is meant by a turbulent blood flow?

Forceful, unpredictable flow

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What can cause defects in blood flow?

Thromboembolism- most common
Atheroma
Hyperviscosity
Spasm
External compression
Vasculitis
Vascular steal

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What is meant by hyperviscocity?

Blood is too thick

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What is vasculitis?

Inflammation of the vessel wall

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What is meant by vascular steal?

When a vascular system steals blood from another system

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RECAP- what is Virchow’s Triad?

Changes in the blood vessel wall

Changes in the blood constituents

Changes in the pattern of blood flow

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What can Virchow’s triad cause?

Thrombosis

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What is meant by thrombosis?

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

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What is the difference between a clot and a thrombus?

A clot is solidified blood
A thrombus is a mass within the system

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Give an example of a condition when there is a change in the blood vessel wall.

Atheromatous coronary artery

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Describe how you can develop a thrombosis regarding Virchow’s triad.

Endothelial injury

Stasis or turbulent blood flow

Hypercoagulability of the blood

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Describe how a thrombin can be formed.

-Cell has atheromatous plaque where the endothelial surface is still in tact
-Turbulent blood flow damages endothelial surface
–Exposes collagen of plaque to the blood
-Elements, like platelets, fibrin and RBC’s get stuck to the collagen, hence forming an thrombus

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Give an example of a condition where there is a change in the blood’s constituents.

Hyperviscosity
Post-traumatic hypercoagulability

Give two examples of changes of blood flow which would cause stasis.

Long haul flights
Post-surgery patients who are lying in bed

Give two examples of changes of blood flow which could cause turbulence.

Atheromatous plaque
Aortic aneurysm

What do the consequences of thrombosis depends on?

Site
Extent- partial or complete occlusion?
Collateral circulation

List some common clinical conditions involving thrombosis.

DVT (deep vein thrombosis)
Ischaemic limb
MI

What are the outcomes of thrombosis?

Resolution
Organisation/recanalisation
Death
Propagation leading to embolism

What is embolism?

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

What is an embolus?

Detached intravascular solid, liquid or gaseous mass

What are most emboli formed from?

Dislodged thrombi aka thromboembolism

What are some possible sources for Systemic/Arterial Thromboembolus?

Mural thrombus (associated with MI or left atrial dilatation + AF) Aortic aneurysms Atheromatous plaques Valvular vegetations

Where may a systemic thrombus travel to?

Travel to wide variety of sites- lower limbs most common, brain, other organs

What does the consequence of systemic thrombus depend on?

Vulnerability of affected tissues to ischaemia Calibre of occluded vessel Collateral circulation ... but usually infarction occurs

Where does venous thromboembolus originate from?

Deep venous thromboses

What is the most common thromboembolic disease?

Deep venous thrombus

Where do venous thromboembolus' travel to?

Pulmonary arterial circulation

Where can venous thromboembolus' occlude?

Depending on size, may occlude main pulmonary artery, bifurcation (saddle embolus), smaller arteries

What are the potential outcomes of pulmonary thromboembolism?

Pulmonary haemorrhage/infarction Right heart failure Sudden death

What can several pulmonary thromboembolisms over time lead to?

Pulmonary hypertension and right ventricular failure

What are some of the risk factors for DVT and pulmonary thromboembolism?

Cardiac failure Severe trauma/burns Post-op/post-partum Nephrotic syndrome Disseminated malignancy Oral contraceptive Increased age Bed rest/immobilisation Obesity Past medical history of DVT

What can you do to patients at a higher risk of DVT/PT?

Give prophylaxis before any surgery Thromboembolic disease stockings Anticoagulants

When may a fat embolus occur?

After major fractures- little bits of fat get in the circulation

When might you get gas embolus?

Decompression sickness

What happens in air embolus?

Nitrogen forms as bubbles which lodge in capillaries

When might you get an air embolus?

Head and neck wounds Surgery CV lines (central venous catheter)

Who might be affected by a trophoblast embolus?

Pregnant women

Where in the body will a trophoblast embolus affect a pregnant woman?

Lungs

What can amniotic fluid embolus cause?

Cause of collapse and sometimes death in childbirth

Bone marrow can embolise as a result of what?

Fractures

Give some examples of foreign bodies which could end up embolising.

Intravascular cannulae tips, sutures, etc