Thrombosis Embolism and Infarction

Question 1

define thrombus

Answer 1

a solidification of blood contents that forms within the vascular system during life.

Question 2

define thrombosis

Answer 2

this is a pathological process that denotes the formation of a thrombus within the noninterupted vascular system

Question 3

what is the first aspect which contributes to the pathogenesis of thrombosis

Answer 3

endothelial injury - important in thrombi formation in the heart and arteries

Question 4

what are the other potential bases for endothelial injury

Answer 4

radiation injury 
chemical agents: exogenous and endogenous 
bacterial toxins and endotoxins 
immunologic injuries 
neoplastic involvement

Question 5

what are the roles of platelets in thrombosis

Answer 5

after injury to a vessel, platelets undergo three important reactions:
- adhesion
- secretion (release reaction)
- aggregation
all these processes are collectively known as PLATELET ACTIVATION

Question 6

What happens to blood vessels during the first steps after the initial injury
VASOCONSTRICTION
PRIMARY HEMOSTASIS

Answer 6

constriction of BVs
platelets then adhere to the exposed collagen and undergo a change in shape and become square.
they then release their granules into the lumen which in turn recruits more platelets
this results in the formation of a homeostatic plug

Question 7

what granules do platelets secrete

Answer 7

ADP = adenosine diphosphate 
TXA2 = thromboxane A2
Pf4 = platelet factor 4

Question 8

how do the platelets adhere to the collagen and how do they adhere to each other

Answer 8

they adhere to the surface via von williebrand factor and Glycoprotein Ib and adhere to eachother via fibrinogen and Glycoprotein IIb-IIIa

Question 9

what is a definceicny in GpIIb-IIIa complex called

Answer 9

glanzmanns thrombasthenia

Question 10

what is a deficiency in GpIb called

Answer 10

Bernard-soulier syndrome

Question 11

SECONDARY HEMOSTASIS

Answer 11

When several layers have been formed tissue factor is released

• phospholipid complex expression which leads to the activation of thrombin
• this in turn causes fibrin polymerisation which acts as a strong glue

Question 12

THROMBUS AND ANTITHROMBOTIC EVENTS

Answer 12

This newly formed mass could grow to occlude the vessel but the release of:
t-pa (fibrinolysis)
thrombomodulin - acts by blocking the coagulation cascade so there is no more build up
PREVENTS THIS

Question 13

What are the two types of alterations in blood flow

Answer 13

turbulence = arterial and cardiac thrombi 
stasis = venous thrombi

Question 14

what is the role of the alterations in blood flow towards thrombosis pathogenesis

Answer 14

• disrupt laminar flow
• prevent dilution of the coagulation factors
• retard the inflow of inhibitors of clothing factor
• promote endothelial cell activation

Question 15

what is hypercoagulability

Answer 15

an alteration of the blood coagulation mechanism that In some what predisposes thrombosis.
Primary = genetic 
Protein C and S deficiency 
Secondary = acquired 
Bed rest, tissue damage, MI, Carcinoma

Question 16

Mural thrombi

Answer 16

applied to one wall of underlying structure, occur in the capacious lumina of the heart chambers and aorta

Question 17

arterial thrombi

Answer 17

usually occlusive
may be mural
frequent in coronary, cerebral, femoral
appears grey-white and are friable (easily broken)

Question 18

when looking at histology how can you tell its a thrombus

Answer 18

lines of Zahn
pale band = fibrin and platelets
red band = RBC trapped between the fibrin

Question 19

venous thrombosis

Answer 19

invariably occlusive and appear dark red , they mostly effect veins of the lower extremities

• deep calf
• popliteal
• iliac veins

Question 20

thrombophlebitis

Answer 20

inflamed and then becomes thrombosed

Question 21

arterial thrombosis

Answer 21

• loss of pulses distal to the thrombus
• THE 5 P’S area becoming perishing cold, pale, painful, paraesthesia
• eventually tissue dies and gangrene results

Question 22

Symptoms of a superficial venous thrombosis (saphenous system)

Answer 22

congestion, swelling, tenderness (these rarely embolise)

Question 23

symptoms of a deep venous thrombosis

Answer 23

foot and ankle oedema, humans sign (dorsiflexion of the foot and pain in the calf as a result)
could be auto symptomatic and recognised only when they have embolised

Question 24

what are some treatment options for thrombosis

Answer 24

stockings as a prevention

anticoagulant drugs which aim to prevent the clot growing any larger and to prevent or stop embolism

Question 25

what are the two anticoagulant drugs most commonly used

Answer 25

heparin (intravenously or subcutaneously

warfarin (orally) only starts to work after one day so start on heparin first

Question 26

definition of an embolism

Answer 26

a detached intravascular solid, liquid or gaseous mass that is carried by the blood to a site distant from its point of origin

Question 27

what are some other causes of an emobolism

Answer 27

bits of tumour
foreign bodies
bubbles of air or nitrogen

Question 28

pulmonary embolism

Answer 28

occlusion of a large or medium sized pulmonary artery is embolic in origin until proven otherwise
most occur in the large deep veins of the lower leg

Question 29

what is a saddle embolus

Answer 29

large emboli that lodge in the bifurcation

Question 30

what are the two pathophysiologic consequences of emboli

Answer 30

respiratory compromise
haemodynamic compromise
a large PE is one of the few causes of virtually instant death (pulseless electrical activity PEA)

Question 31

what are some signs of a small pulmonary embolism

Answer 31

occlusion can put some strain on the heart which can be evident on an ECG
chest X-ray may disclose a pulmonary infarct as a wedge shaped infiltrate

Question 32

systemic embolism

Answer 32

refers to emboli that travel through the arterial circulation, these almost always cause infarction

• lower extremities
• the brain
• viscera
• upper limbs

Question 33

air embolism

Answer 33

the pressure of air or gas within the circulation obstruct vascular flow and damage tissues 
BAROTRAUMA 
can happen during delivery or abortion 
caisson disease (scuba divers treated in recompression chamber) or decompression sickness

Question 34

fat embolism

Answer 34

minute globules of fat can often be demonstrated in the circulation following
- fractures of the shafts of long bones
- soft tissue traumas and burns
- fat embolism syndrome
mechanical obstruction and chemical obstruction (free fatty acids released from fat globules result in toxic injury to the vascular endothelium)
for histology used frozen sections and fat stains
characterised by:
- pulmonary insufficiency
- neurologic symptoms
- anaemia and thrombocytopenia
symptoms appear after the latent 24-72 hour period and there is a sudden onset of tachypnoea, dyspnoea, and tachycardia, irritability and restlessness

Question 35

amniotic fluid emobolsism

Answer 35

infusion of amniotic fluid into the lateral circulation
pulmonary circulation POST MORTUM would contain epithelial squares from foetal skin and other things
- profound respray difficulty (Depp cyanosis and cardiovascular shock
- followed by convulsions and profound coma

Question 36

infarct

Answer 36

an area of ischaemic necrosis cause by the occlusion of arterial supply or venous drainage in a particular tissue
two causes:
thrombosis and embolism
twisting of vessels and vasospasm

Question 37

factors which influence development of an infarct

Answer 37

nature of the vascular supply
rate of development of the occlusion
vulnerability to hypoxia
oxygen content of blood

Question 38

what are the two types of infarcts

Answer 38

red (haemorrhagic):
- venous occlusions 
- in loose tissues 
- in tissues with dual circulation 
white (anaemic)
- arterial occlusions 
- solid organs 
septic or bland 
- bacteria collection

Question 39

histology of an infarction

Answer 39

ischaemic coagulative necrosis but liquefactive necrosis in the CNS
inflammatory response (hours - 7 days)
reparative response (1-2 weeks)
scaring (2weeks - 2 months)