Pathophysiology of thrombosis and embolism Flashcards
What is normal blood flow
and two types of abnormal blood flow
Laminar - constant streamline no turbulence
Stasis - Stagnation of flow - water is not moving as is being obstructed
Turbulence - Forceful and unpredictable flow
What are examples of conditions that cause defects in the blood
Thromboembolism common Other causes: Atheroma - Plaque obtruding into lumen Hyperviscosity - increased viscosity Vascular spasm - external compression - e.g. tumour squishing blood vasculitis - inflammation of blood vessels vascular steal
Define vascular steal
Vascular network in a vascular organ steals blood at the expense of another vascular organ
What is the three mechanisms of Virchow’s Triad
Changes in the blood vessel wall
Changes in the blood constituents
Changes in the pattern of blood flow
Define thrombosis
Formation of a solid mass from the constituents of blood within the vascular system during life
(if not within the vascular system its a clot not thrombosis)
What is the over all pathogenesis for thrombosis relating to virchows triad
Endothelial injury
Stasis or turbulent blood flow
Hypercoagulability of the blood
What is an examples of endothelia injury/change in blood vessel wall resulting in thrombosis
atheromatous coronary artery
What is the pathogenesis of atheromatous coronary artery resulting in thrombosis
Plaque forms - causes flow to become turbulent - then endothelia surface becomes lost - exposed collagen - creates fibrin network on sticky surface, platetes adhere, RBC trapped - forms thrombosis
What are the lines of zahn that appear
Fibrin networks inter dispersed with lines of RBC
What is the biggest risk factors that contributes to virtuous triad
Hypercholestoanemia - causes a change in the blood constituents, change in vessel wall, and change in blood flow
What is it called when thrombosis forms on the inner surface of the heart wall due to a
Neural thrombosis
What are example of changes in blood constituents that result in thrombosis
hyperviscosity - due to reduction in plasma volume
post-traumatic hypercoagulability
What is examples that cause stasis blood flow that can result in deep vein thrombosis
Long flights or postoperative - not using lower limbs
What is examples that cause turbulent blood flow resulting in thrombosis
atheromatous plaque
aortic aneurysm - localised dilatation in BV
What do the consequences of thrombosis/thromboembolism/embolism depend upon
Site
Extent
Collateral circulation
What are common clinical conditions occurring due to thrombosis
Deep Vein Thrombosis - follows vein thrombosis
ischaemic limb - follows arterial thrombosis
Myocardial infarction - following thrombosis of coronary artery
How is resolution of thrombosis achieved
Spontaneous
Usually need medical intervention
Thrombolytic or fibrinolytic agents -
What is the next best outcome if you cant achieve resolution, and what does this allow?
Organisation of the thrombosis
Control thombus so doesn’t get any bigger, allowing new blood cell formation, resulting in wider lumina, restoring blood blow = Recanalisation
What is the possible outcomes of thrombosis
Resolution
Organisation
Death
Propagate
What can propagation of thrombus lead to
ThromboEmbolism - traveling blood clot
Define embolism
Movement of abnormal material (detached intravascular solid, liquid or gaseous mass) in the bloodstream and its impaction in a vessel, blocking its lumen
Occurring at distant site to the origin
(doesn’t have to be a thrombus)
What is most common embolism
dislodged thrombi = thomboembolism
Factors causing embolism is dependant the type of embolus involved.
What are the different types of embolus ?
Thrombus Fat Gas Tumour Air Trophoblast septic maternal Amniotic fluid Bone marrow Foreign bodies
What are the two types of thromboembolism
- Systemic/Arterial Thromboembolus
- Venous Thromboembolus
What is the sources of Systemic/Arterial Thromboembolus
Blood vessel thrombus; MI or left atrial dilatation
aortic aneurysms,
atheromatous plaques,
Endocarditis
Where do systemic thromboembolus travel
Travel to wide variety of sites: lower limbs most common, brain, other organs
What is the usually consequence of Systemic/Arterial Thromboembolus
Ischaemia / Infarction
What is collateral circulation
rocess in which a system of small, normally closed arteries connect and start to carry blood to part of the heart when a coronary artery is blocked, or to part of the brain when a cerebral artery is blocked. These arteries can serve as alternate routes of blood supply.
Venous Thromboembolus is the most common form of thromboembolic disease, so where does it originate from
Originate from deep venous thromboses (lower limbs)
What is the pathophysiology of Venous Thromboembolus
Travel to the pulmonary arterial circulation
Depending on size, may occlude main pulmonary artery, bifurcation, smaller arteries and Often multiple
What is the consequences of Venous Thromboembolus
and what dies the consequence depend upon
silent,
pulmonary haemorrhage/infarction,
right heart failure,
sudden death
The size of the embolus
What is the result of multiple Pulmonary embolism over time
pulmonary hypertension and right ventricular failure
What increases the risk factor for pulmonary embolism and DVT
i.e. changing blood flow/vessel/constituents
Cardiac failure, severe trauma/burns, post-op/post-partum, nephrotic syndrome – kindeys not working properly, disseminated malignancy, oral contraceptive, age, bed rest/immobilisation, obesity, Past Medical History of DVT
What is given to surgical patents at risk of embolism
Prophylaxis: TEDS, s/c heparin
How does gas embolisms occur
Decompression Sickness - N2 forms as bubbles which lodge in capillaries
How does air embolism occur
Head and neck wounds,
surgery,
CV lines
introduce air bubble
How does septic material cause embolism
Can result in infective endocarditis, and break of travel in the blood stream causing mycotic aneurysms
What can Tumour embolism allow
Metastasis
How does trophoblast embolism occur
Material from the placenta traveling to the mothers lungs
How does amniotic fluid embolism occur
rare, bits if the amniotic fluid get into maternal circulation migrate to lungs and cause allergic reaction
What are examples of foreign bodies that can cause embolisms
Intravascular cannulae tips, sutures, etc
What embolism occur after fractures (or CPR,
Bone marrow embolism
Fat embolism
