L13- Atheroma, Thrombosis & Embolism

Question 1

What is Atherosclerosis ?

Answer 1

Degeneration of arterial walls characterised by fibrosis, lipid deposition and inflammation which limits blood circulation and predisposes to thrombosis

Question 2

What are the Commonly affected vessels where atherosclerosis takes place?

Answer 2

Bifurcations (sites of turbulent flow)

Abdominal aorta

Coronary arteries

Popliteal arteries

Carotid vessels

Circle of Willis

Question 3

What are the common risk factors for atherosclerosis?

Answer 3

Nonmodifiable: Age, gender, FH, genetics

Modifiable: Hyperlipidaemia, hypertension, diabetes, smoking

Question 4

Pathophysiology of atherosclerosis

Answer 4

Arises due to chronic injury and repair of the endothelium

1) endothelial injury –> lipid will accumulate in the inner most part of the vessel (the “intima”)
2) Monocytes migrate into intima and ingest lipid becoming FOAM CELLS (fatty streak)
3) Foam cells secrete chemokines —> atherosclerotic plaque develops as a result of cell proliferation
4) This mixture of fat, extracellular material and leukocytes and smooth muscle form the atherosclerotic plaque

Question 5

Potential consequences of atherosclerosis?

Answer 5

Occlusion
-Ischaemia

Weakening of vessel walls
-Aneurysm formation

Erosion
-Thrombosis formation

Question 6

What is Thrombosis ?

Answer 6

Solidification of blood contents formed in the vessel during life

Question 7

Clot vs Thrombus…

Answer 7

Clot: Stagnant blood, enzymatic process, elastic, adopts shape of vessel, stagnant blood

Thrombus: Dependent on platelets, firm, within the body during life

Question 8

What are Platelets ?

Answer 8

Fragments of megakaryocytes in the bone marrow

Circulate in the blood stream

Bind to collagen exposed by endothelial damage and become activated

Secrete

• Alpha granules: fibrinogen, fibronectin, PDGF
• Dense granules: chemotactic chemicals

Question 9

Name the three parts of Virchow’s triad

Answer 9

Changes in :

• The intimal surface of the vessel
• The pattern of blood flow
• Blood constituents

Question 10

Virchow’s triad example of arterial thrombus…Name the changes happening:

Answer 10

Plaque rupture- turbulent flow and intimal change

Hyperlipidaemia – change in blood constituents

Platelets bind and fibrin is produced entrapping RBC

Question 11

Where would Lines of Zahn be found?

Answer 11

Where thrombosis has occurred

Presence implies thrombosis at a site of rapid blood flow

E.g Aorta

Question 12

Virchow’s triad example of Venous Thrombosis…Name the changes happening:

Answer 12

Intimal change: valves

Change in blood flow: Immobile

Change in blood constituents:

• Inflammatory mediators (infection, malignancy)
• factor V leiden
• Oestrogen

Question 13

What is Cardiac Thrombosis

Answer 13

Thrombi in the heart are known as mural thrombi and occur over areas of endomyocardial injury:

• M.I
• Myocarditis

Can also occur with arrhythmias and cardiomyopathy

Question 14

Potential Consequences of Thrombosis

Answer 14

Occlusion of vessel

Resolution

Incorporation into vessel wall

Recanalisation (provides capillary-sized channels through the thrombus for continuity of blood flow)

Embolisation (thrombus breaks free from the vascular wall and becomes mobile)

Question 15

What is an Embolus

Answer 15

A mass of material in the vascular system able to lodge in a vessel and block it

Question 16

Most common emboli

Answer 16

Pulmonary emboli

Question 17

Clinical effects of Pulmonary Emboli

Answer 17

Small: initially asymptomatic, if multiple may result in pulmonary hypertension

Medium: Cause acute respiratory and cardiac failure (V/Q mismatch, RV strain)

Large: Death “saddle emboli”
(It lodges at the main pulmonary arterial trunk at its bifurcation)

Question 18

What do you call an infected aneurysm

Answer 18

Mycotic Aneurysm

Question 19

What is an Infective embolism

Answer 19

Usually from the vegetations on infected heart valves

Effects compounded by the infective nature – may lead to mycotic aneurysm formation

Question 20

What is a Tumour embolism

Answer 20

Bits may break off as tumours penetrate vessels

Do not usually cause immediate physical problems

Major route of dissemination

Question 21

What is a Gas embolism

Answer 21

Air:(vessel opened into the air)
-Obstetric procedures / chest wall injury
>100ml to cause clinical effects

Nitrogen:

• Decompression sickness (“the bends”)
• Divers, tunnel workers
• Nitrogen bubbles enter bones, joints and lungs

Question 22

What is an Amniotic fluid embolism

Answer 22

Increased uterine pressure during labour may force AF into maternal uterine veins

Lodge in lungs —> respiratory distress

Question 23

What is a Fat embolism

Answer 23

Microscopic fat emboli

Sudden onset of respiratory distress

Question 24

What is a Foreign body embolism

Answer 24

Particles injected intravenously

E.g. talc in IVDU’s

Leads to a granulomatous reaction