Thrombosis and Embolism Flashcards
thrombosis
Formation of a solid mass of blood within the
circulatory system.
That solid mass is then called a thrombus.
clot
mass of blood outside the vessel wall
when does a thrombus form
when there is an abnormality in the vessel wall, blood flow, and blood components
what causes damage to the wall of the vascular system
Atheroma
Inflammation
Direct injury
Damage to heart
arterial thrombus
Pale
Granular
Lower cell content
Lines of Zahn
venous thrombus
soft
gelatinous
deep red
higher cell content
intrinsic pathway
ETENTE
Factors 2 8 9 10 11
extrinsic pathway
TEFS
5 7 10
lysis
- Most likely when thrombi are small
- Complete dissolution of thrombus
- Fibrinolytic system active
- Blood flow re-established
propagation
Progressive spread of
thrombosis
Distally in arteries
Proximally in veins
organisation
• Reparative process
• Ingrowth of fibroblasts and capillaries (similar to
granulation tissue)
• Lumen remains obstructed
recanacalisation
• One or more channels form through
area of organising thrombus.
• Blood flow can be re-established but usually
incompletely.
thromboembolism
- Part of thrombus breaks off
- Travels through bloodstream
- Lodges at distant site
effects of venous thrombosis
venous system-
- congestion
- oedema
- ischaemia
- infarction
effects of arterial thrombosis
arterial system
- ischaemia
- infarction
- depends on site and collateral circulation
embolism
Embolism is the blockage of a blood vessel
by solid, liquid or gas at a site distant from its
origin.
>90% of emboli are thrombo-emboli
what does thrombosis in vein lead to
pulmonary embolism
thrombosis in heart
Due to endocardial thrombus (myocardial infarction), vegetations, atrial fibrillation.
Fragments into aorta and then lodge in cerebral arteries, renal artery, mesenteric artery, iliac/femoral
arteries leading to ischaemic stroke, renal infarcts, bowel ischaemia, limb ischaemia.
thrombosis in carotid artery
Atherosclerotic plaque with development of thrombus causing emboli which causes cerebral
ischaemia (Ischaemic Stroke)
abdominal aortic thrombosis
Atherosclerotic plaque or aneurysm with development of thrombus causing emboli which causes
acute limb ischaemia.
pre-disposing factors of DVT
- Immobility/bed rest
- Post-operative
- Pregnancy and post-partum
- Oral contraceptives
- Severe burns
- Cardiac failure
- Disseminated cancer
- Superficial thrombophlebitis (inflammation of superficial veins of the legs)
complications of pulmonary embolism
massive coiled embolus in main pulmonary artery- death
small embolus lodged in peripheral pulmonary artery- pulmonary infarct
multiple repeated small emboli- pulmonary hypertension
what does carotid artery thrombus lead to
ischaemic stroke
how do you treat a thrombus and thromboemboli
clot busters/ thrombolysis CT pulmonary angiogram low molecular weight heparin newer generation NOAC/DOAC antocoagulants oral warfarin embolectomy
what can form an embolism
-body fat
-bone marrow
-material from
-atheromatous plaques
-tumour fragments
-parasites
-bubbles of air or other gases
-debris injected intravenously
-amniotic
fluid
-medical equipment
-bits of brain or liver after trauma.
where is embolisation more likely to occur and why
In veins blood flow is from smaller to larger vessels, hence embolization
cannot occur in veins. Objects carried by the blood in veins will therefore
go through the right heart and embolise in the pulmonary arteries
where do 80% of pulmonary emboli arise from
80% of pulmonary emboli arise from thrombi in the deep
veins of the thigh and the popliteal vein
what can multiple pulmonary emboli result in
pulmonary hypertension
what are paradoxical emboli
They are thromboemboli that form in the systemic veins
but embolise to the systemic arteries. They manage to bypass the lungs
in one of two ways.
what ways can a pulmonary emboli bypass the lungs
- Small emboli are able to pass through the arterio-venous
anastomoses in the pulmonary circulation (these anastomoses
are 20-40 times the diameter of a capillary). Incidentally, this is
also the way that fat droplets pass through the lungs in fat
embolism. - Larger emboli can only enter the systemic circulation by passing
through defects in the interventricular septum or a patent
foramen ovale during coughing, lifting or straining (which
increases the pressure in the right side of the heart to greater
than that in the left, pushing the thrombus through the defect).
how can an emboli form from artherma
. It can be released into the blood when a plaque
breaks open. This can happen spontaneously and also during surgery or
catheterisation for coronary artery disease. Such emboli often affect the
intestine and present with abdominal pain.
how can a fat and bone marrow emboli form
a complication of bone fractures but fat emboli can also
occur after liposuction. When a bone is fractured the bone marrow fat
cells that are injured break up and release oil droplets. These coalesce
over a period of a few days and are then sucked into gaping venules that
have been torn by the fracture
how does aspirin treat thromboembolism disease
Aspirin is antithrombogenic. It irreversibly acetylates an enzyme of
prostaglandin synthesis (cyclooxygenase) and this means that platelets
can’t produce thromboxane A2 which is a powerful platelet aggregator.
the formation of a haemostatic plus is therefore inhibited so bleeding time is prolonged
when is aspirin used
to reduce the risk of MI and stroke
also as a phophylactic agasint DVT in patients taking long haul flights
why is heparin used
Low molecular weight heparin is used as prophylaxis against thrombosis
and also to treat thrombosis. It is given subcutaneously or intravenously.
It forms irreversible complexes with antithrombin III resulting in its
activation.
why is warfarin used
prophylaxis against thrombosis and also
to treat thrombosis. It is an oral medication which interferes with vitamin
K metabolism. The dosage required is titrated to the patients PT test
results, specifically the INR results.
whta is INR
(INR stands for international
normalised ratio which is the ratio of the patient’s PT to a normal
control).
How are filters used to treat thromboembolism disease
putting an umbrella-shaped filter into the inferior vena cava
