10 - Atheroma, Thrombosis and Embolism

What is an atheroma?

A lesion of the intima that protrudes into the vessel wall, consisting of a raised lesion with a soft core of lipids and is covered by a fibrous collagen cap

In what layer of the vessel wall does an atheroma arise?

Intima

What liquids are mainly found in the soft core of an atheroma?

Cholestrol

Give 6 components of the fibrous cap found in the atheroma:

1) smooth muscle cells

2) macrophages

3) foam cells

4) lymphocytes

5) collagen

6) elastin

What are foam cells?

Lipid-filled macrophages

Where do the smooth muscles in the fibrous cap of an atheroma come from?

Media layer

What type of blood vessels are commonly affected by atheroma?

Bifurcating vessels

Give 5 examples of arteries that bifurcate:

1) abdominal aorta

2) coronary arteries

3) popliteal arteries

4) carotid arteries

5) circle of Willis

Why is it that bifurcating vessels are more risk of atheroma?

They are the sites of turbulent flow

Give 4 non-modifiable risk factors for atheroma:

1) increasing age

2) male gender

3) family history

4) genetic abnormalities

Give 5 modifiable risk factors for atheroma:

1) hyperlipidaemia

2) hypertension

3) cigarette smoking

4) diabetes

5) C-reactive proteins

How does atheroma begin?

Damage or injury to the endothelium by factors such as high blood pressure, high cholesterol, an irritant such as nicotine and certain diseases such as diabetes

How does atherosclerosis begin to develop?

Develops as a chronic inflammatory response of the arterial wall to endothelial injury

What is the foundation structure of arthrosclerosis called?

Fatty streak

How do fatty streaks form vessels?

Multiple tiny flat yellow spots coalesce into streaks

How does an atherosclerotic plaque form?

Due to intimal thickening and lipid accumulation

Give 4 common consequences of atherosclerosis:

1) rupture exposes blood to thrombogenic substances which induces thrombosis and occlusion

2) haemorrhage into plaque, occluding the lumen

3) atheroembolism

4) aneurysm formation (weakened vessel)

What is a thrombus?

Blood clot formed within the vascular system

What is the most common site of arterial thrombus formation?

On top of an atheroma

What is the most common reason for a venous thrombosis?

Stasis

What are the 3 factors in Virchow's Triad which contribute to thrombus formation?

1) Abnormal blood flow (stasis or turbulence)

2) Endothelial injury

3) Hypercoagulability

What are common diseases caused by arterial thrombosis?

1) Myocardial infarction

2) Ischaemic stroke

What is the composition of arterial thrombosis?

Mainly platelets

What is the treatment for arterial thrombosis?

Anti-platelet agents (clopidogrel)

What are common diseases caused by venous thrombosis?

1) DVT

2) Pulmonary embolism

What is the composition of venous thrombosis?

Mainly fibrin

What is the treatment for venous thrombosis?

Anticoagulants (heparin, warfarin)

Give 4 examples of endothelial injury factors that contribute to thrombus formation damage:

1) smoking

2) hypertension

3) surgery

4) trauma

Give 2 examples of abnormal blood flow factors that contribute to thrombus formation:

1) immobility

2) polycythaemia

Give 7 examples of hypercoagulability factors that contribute to thrombus formation:

1) factor V Leiden

2) protein C and S deficiency

3) prothrombin overactivity

4) cancer and chemotherapy

5) HIT

6) pregnancy

7) obesity

What regions of the body does arterial thrombosis commonly affect?

1) left hand circulation

2) left heart chambers

What is the difference between a clot and a thrombus?

- Clot: Platelets not involved, outside vessel or inside, red, gelatinous, not attached to vessel wall

- Thrombus: Platelets involves, only inside vessel, red (V) or pale (A), firm, attached to vessel wall

What is an embolus?

A mass of material in the vascular system able to become lodged in the vessel and block its lumen

What is the most common cause of emboli formation?

From thrombus

What is the most common embolus?

Pulmonary embolus derived from deep vein thrombosis

Give 7 types of embolus:

1) thrombus derived

2) atheromatous plaque material

3) vegetation of heart valves (infective endocarditis)

4) fragments of tumour (metastasis)

5) amniotic fluid

6) gas

7) fat

Why does atrial fibrillation increase the risk of thrombosis?

As blood no longer has its normal lamina direction of flow

Give 3 examples of diseases caused by systemic emboli:

1) TIAs

2) gangrene

3) bowel necrosis