Pathophysiology of Thrombosis and Embolism Flashcards
What is an atheroma that has ruptured and formed a clot known as?
- Complicated atheroma
What is normal blood flow said to be?
Laminar
What does laminar blood flow mean?
- Blood cells travel through the middle of the vessel - Plasma travels along the sides - All constituents of the fluid travel at the same speed
What is stasis blood flow?
An abnormal flow where the blood becomes stagnant
What is turbulent blood flow?
- Loss of laminar flow causing “whirpooling” - Forceful and unpredictable
What is Virchow’s triad?
If one of them change then vascular disease can occur
What are the three aspects of Virchow’s triad?
- Changes in blood vessel wall - Changes in the blood constituents - Changes in the pattern of blood flow
What can arise from Virchow’s triad being altered?
- Thrombosis
What is the difference between thrombosis and clot?
- Thrombosis occurs in the body during life - Clot occurs either outside the body or during death
Give an example of changes in the blood vessel wall that can lead to thrombosis
Atheromatous coronary artery
What are the constituents of the normal arterial wall?
- Tunica intima - Tunica media - Tunica adventitia
What is the pathogenesis of thrombosis?
- Endothelial injury - Stasis or turbulent blood flow - Hypercoagulability of the blood These three are virchow’s triad
Study the atheroma pathology diagram
What is the order of pathology of a thrombus?
- Atheromatous coronary artery
- Causes turbulent blood flow leading to fibrin deposition and platelet clumping
- Intimal cells lost
- Collagen below intima is exposed, platelets activated and adhere
- Further turbelence and more platelet deposition
- Propegation occurs and thrombus breaks off becoming an embolus
How does hypercholesterolaemia follow Virchow’s triad in leaving to a thrombus
- Thrombus usually superimposed on atheroma after blood vessel wall is altered
Histologically, how are thrombi laid down?
- Lines of Zhan
- Platelets below fibrin below RBCs etc
What are examples of changes in the blood constituents that may lead to thrombus?
- Hyperviscosity
- Post traumatic hypercoagulability
When can stasis of blood flow occur?
- On long haul flights without movement
- Post operative
What conditions can lead to turbulent flow?
- Atheromatous plaque
- Aortic aneurysm
What are the depending factors on the consequences of a thrombosis?
- Site
- Extent
- Collateral circulation
What are the outcomes of a thrombosis?
- Resolution
- Complication
- Death
What is meant by the resolution of a thrombus?
- Orginisation/recanalisation of the vessel occurs
What typically causes death from a thrombus?
- If it becomes an embolism and moves to a vital organ
What is the definition of an embolism?
- Movement of abnormal material in the bloodstream and its impaction in a vessel, blocking its lumen
What can cause an embolus?
- Any intravascular solid liquid or gas
What are emboli from thrombi known as?
Thromboembolism
What are the common sources of ARTERIAL thromboembolus?
- Mural thrombus
- Aortic aneurysm
- Atheromatous plaques
- Valvular vegetations
What is associated with a mural thrombus
- MI
- Left atrial dilatation
- AF
What are the common areas of spread of a thromboembolus?
- Lower limbs
- Brain
- Other organs with high blood demand
What do consequences of an embolus depend on?
- Vulnerability of tissue it’s lodged in to ichaemia
- Size of occluded vessel and how high up it is (collateral circulation)
What usually occurs as a result of a lodged thromoembolus?
Infarction
Where do venous thromboemboli originate from
DVT’s
Where do venous thromboemboli travel to?
- Pulmonary arterial circulation
- May occlude pulmonary artery
What type of embolus occludes the bifurcation of the pulmonary artery
Saddle embolus
What do the consequences of a PE rely on?
Size of embolus
What types of PE’s are there?
- Silent (asymptomatic)
- Pulmonary haemorrhage/infarction
- right heart failure
- Sudden death
What occurs from multiple PE’s over time?
- Pulmonary hypertension
- RV failure
What are the risk factors for a venous thromboembolism?
- Cardiac failure
- Severe trauma
- Post op
- Nephrotic syndrome
- Contraceptive pill
- Old age
- Bed rest
- Obesity
- PMH of DVT
When do fat emboli occur most commonly?
After major fractures
What is an example of a gas emboli causing condition?
Decompression sickness
- N2 forms as bubbles which lodge in capillaries
When do air emboli most commonly occur?
- Head and neck wounds
- Surgery
- CV lines
What type of emboli can be a result of pregnancy?
- Trophoblast embolus
During what condition can septic material act as an embolus?
- Infective endocarditis
What other types of rare embolus are there?
- Amniotic fluid
- Bone marrow
- Foreign bodies
- Tumour
