Atheroma, thrombosis, embolism and infarction

Question 1

What is an atheroma?

Answer 1

Fibro-fatty plaques
(porridge-like tumour)
Refers to plaques found particularly in elastic and medium-to-large muscular arteries

Question 2

What is atherosclerosis?

Answer 2

Porridge-like hardness

The consequence of atheroma

Question 3

What is arteriosclerosis?

Answer 3

Hardening of the arteries
Atheroma is one cause
Other causes include age-related sclerosis an calcification

Question 4

Risk factors of atheroma

Answer 4

Age
Male sex
Genetics
Hyperlipidaemia
Hypertension
Smoking
Diabetes mellitus

Question 5

Describe the pathogenesis of atheroma

Answer 5

Chronic endothelial injury/dysfunction
Accumulation of intimal lipid and foamy macrophages
Smooth muscle proliferation
Fibrosis forming a fibro-lipid plaque
Plaque injury- thrombosis and haemorrhage

Question 6

What is the difference between a complicated and uncomplicated plaque?

Answer 6

Uncomplicated= thin fibrous cap
Complicated= superimposed thrombi due to ulceration of thin cap= haemorrhage

Question 7

Where do atheroma’s occur?

Answer 7

Elastic and medium-to-large muscular arteries

• Abdominal aorta
• Coronary arteries
• Popliteal arteries
• Descending thoracic aorta
• Internal carotid arteries
• Vessels of the circle of Willis (base of the brain)

Question 8

What are the complications of atheroma?

Answer 8

Calcification
Ulceration
Plaque rupture
Haemorrhage
Thrombosis
Aneurysmal dilation

Question 9

What do the complications of atheroma lead to?

Answer 9

Vessel obstruction and downstream ischaemia

External vessel rupture may also occur, particularly with abdominal aortic aneurysms

Question 10

What are the clinical implications of atheroma?

Answer 10

Cerebral infarction
Emboli in carotid arteries= TIA/ cerebral infarction
Myocardial infarction, cardiac failure
Aneurysm rupture causes sudden death
Peripheral vascular disease with intermittent claudication- thigh (impairment of walking)
Gangrene

Question 11

What is a thrombus?

Answer 11

Solidification of blood constituents that forms within the vascular system during life

Question 12

What is the difference between thrombus and blood clot?

Answer 12

Pathological process- denotes formation of thrombus within uninterrupted vascular system
Solidification of blood constituents outside the vascular system or after death is termed blood clot or haematoma (particularly if formed within tissues)

Question 13

What are the risk factors for thrombosis?

Answer 13

Endothelial injury
Abnormal blood flow
Hypercoagulability
(Virchow’s Triad)

Question 14

Describe endothelial injury

Answer 14

Ulcerated atheromatous plaques (aorta, carotid arteries, iliac and femoral arteries, coronary arteries)
Left ventricular endocardium after myocardial infarction
Abnormal cardiac valves (rheumatic fever, infective endocarditis, prosthetic valves)

Question 15

Describe abnormal blood flow

Answer 15

Disrupts laminar flow
Prevents dilution of clotting factors
Retards the inflow of inhibitors of clotting factors
Promotes endothelial cell activation

Question 16

What is turbulence?

Answer 16

Contributes to the development of arterial and cardiac thrombi

Question 17

What is stasis?

Answer 17

Important in the formation of venous thrombi

Question 18

Describe hypercoagulability

Answer 18

Alteration of the blood coagulation mechanism (particularly platelets and the clotting cascade) that in some way predisposes to thrombosis
May be a genetic predisposition (protein S/C deficiency)
May be acquired (after surgical procedures)

Question 19

What are the types of thrombi?

Answer 19

Mural
Arterial
Venous

Question 20

Describe a mural thrombi

Answer 20

Applied to one wall of the underlying structure

Occur in the capacious cavities of the cardiac chambers and the aorta

Question 21

Describe arterial thrombi

Answer 21

Usually occlusive
May be mural
Frequent in coronary, carotid, cerebral and femoral arteries

Question 22

Describe venous thrombosis

Answer 22

Also termed phlebothrombosis (not to be confused with thrombophlebitis)
Occurs typically in pelvic and leg veins in association with stasis

Question 23

Describe the morphology of thrombi

Answer 23

Histological appearance typically shows alternating pale (band of fibrin and platelets) and dark (red band of red blood cells) ‘lines of Zahn’

Question 24

What direct complications occur due to thrombosis in artery or vein?

Answer 24

Occlusion
Embolism- arterial= distal, venous= proximal
Arterial occlusion

Question 25

What is arterial occlusion?

Answer 25

loss of pulses distal to thrombosis, area becomes cold, pale, painful, eventually tissue dies and gangrene results

Question 26

What are the types of venous thrombosis?

Answer 26

Superficial (saphenous system) | Deep

Question 27

Symptoms of superficial venous thrombosis

Answer 27

``` Congestion Swelling Pain Tenderness Rarely embolise ```

Question 28

Symptoms of deep venous thrombosis

Answer 28

Foot and ankle oedema | May be asymptomatic and recognised only when they have embolised (to the lung)

Question 29

What are the outcomes of venous thrombosis?

Answer 29

Resolution Embolization to the lungs Organised and incorporated into wall Organised and recanalized

Question 30

What is an embolus?

Answer 30

Detached intravascular solid, liquid or gaseous mass that is carried by the blood to a site distant from its point of origin 99% all emboli arise from thrombi (thromboembolism) Implied unless otherwise qualified

Question 31

What are the less common. rare forma of emboli fragments?

Answer 31

``` Bone or bone marrow Atheromatous debris Droplets of fat Tumour cells Foreign bodies (such as bullets) Bubbles of air or nitrogen ```

Question 32

What are the types of embolism?

Answer 32

``` Pulmonary Systemic Amniotic fluid Air Fat ```

Question 33

Describe pulmonary embolism

Answer 33

Embolism to pulmonary arteries Occlusion of large or medium-sized pulmonary artery is embolic in origin until proved otherwise Most arise in thrombi within the large deep veins of the lower leg The next most common origin is pelvic veins, in association with pelvic masses

Question 34

What is a 'saddle' pulmonary embolism?

Answer 34

Large emboli may impact in the main pulmonary artery or lodge at the bifurcation as a saddle embolus Associated with collapse and sudden death- circulatory obstruction

Question 35

What happens to smaller pulmonary emboli?

Answer 35

Travel out into the more periphery pulmonary arteries If of intermediate size- cause pulmonary infarction (especially with cardiac failure) If very small and recurrent- pulmonary hypertension

Question 36

What is a paradoxical embolism?

Answer 36

In the presence of an interatrial or interventricular defect, they may gain access to the systemic circulation

Question 37

Describe a pulmonary infarction

Answer 37

Typically haemorrhagic The base of the infract faces the pleural surface Patients present with haemoptysis- coughing up blood and/or pleuritic chest pain (pain on inspiration)

Question 38

What is systemic embolism?

Answer 38

Emboli that travel through the systemic arterial circulation | 80-85% arise through thrombi within the heart

Question 39

What are the less common sources of thrombi developing from in systemic embolism?

Answer 39

Ulcerated atherosclerotic plaques Aortic aneurysms Infective endocarditis Artificial heart valves and aortic grafts

Question 40

What are the major sites for systemic emboli to lodge at?

Answer 40

Lower extremities (commonest) Brain Viscera (mesenteric, renal, splenic arteries) Upper limbs (much less common)

Question 41

What is an infarct?

Answer 41

Area of ischaemic necrosis caused by occlusion of arterial supply or venous drainage in a particular tissue

Question 42

What is necrosis?

Answer 42

Refers to spectrum of morphological changes that follow cell death in living tissue largely resulting from the progressive action of enzymes on the lethally injured cells

Question 43

Causes of infarction

Answer 43

``` Thrombosis/ thromboembolism Vasospasm Expansion of atheroma Compression of a vessel Twisting of the vessels through torsion Traumatic rupture ```

Question 44

What are the factors that influence the development of an infarct?

Answer 44

- Nature of the vascular supply (single= spleen, dual= lung, small bowel) - Rate of development of occlusion (rapid more likely to cause infarction) - Vulnerability of affect tissue to hypoxia (more metabolically active tissues more vulnerable= heart) - Oxygen content of blood (hypoxia increases risk)

Question 45

What are the types of infarct?

Answer 45

- Red (haemorrhagic)= venous occlusion (torsion)/ loose tissues/ tissues with a dual circulation (lung) - White (anaemic)= arterial occlusions/ solid organs (heart/ spleen) - Septic (infected infarcts)

Question 46

Describe a haemorrhagic infarct

Answer 46

Ovarian infarct Venous occlusion as a result of torsion Dark blue and haemorrhagic

Question 47

Describe the types of anaemic infracts

Answer 47

- Splenic= wedge-shaped, white | - Renal infarct= wedge-shaped, white, rim of hyperaemia (an excess of blood in the vessels supplying an organ)

Question 48

Describe the histopathology of infarction

Answer 48

- Ischaemic coagulative necrosis (mins-days)= CNS - Inflammatory response (hrs- 7 days) - Reparative response (1-2 wees) - Scarring (2 weeks- 2 months)