Pathophysiology of Thrombosis and Embolism Flashcards
What is the characteristic of normal blood flow?
Laminar
What contributes to bloods laminar flow?
- Pressure gradient
- Resistance
- Viscosity of blood
- Velocity
- Compliance
Stasis
Stagnation of flow
Turbulence
Forceful, unpredictable flow
Defects in blood flow
- Thromboembolism
- Atheroma
- Hyperviscocity
- Spasm
- External compression
- Vasculitis
- Vascular steal
What are the 3 components of Virchow’s triad?
- Changes in the blood vessel wall
- Changes in the blood constituents
- Changes in the pattern of blood flow
What is Virchow’s triad?
Factors causing thrombosis
Thrombus
- Formation of a solid mass from the constituents of blood within the vascular system during life
- Caused by Virchow’s triad
Give an example of a change in a vessel wall.
Atheromatous coronary artery
How does Virchow’s triad influence the pathogenesis of thrombosis?
- Endothelial injury
- Stasi or turbulent blood flow
- Hypercoagulability of the blood
Pathogenesis of thrombosis
- Atheromatous coronary artery
- Turbulent blood flow
- Loss of intimal cells, denuded plaque
- Collagen exposed, platelets adhere
- Fibrin meshwork, RBCs trapped
- Alternating bands: lines of Zahn
- Further turbulence an platelet deposition
- Propagation
- Consequences
What is the relationship between atheroma and thrombosis?
Arterial thrombosis most commonly superimposed on atheroma
How is hypercholesterolemia related to Virchow’s triad?
Change in blood constituents
How does flow vary across the thrombus?
Turbulent flow is greatest at the end of the thrombus
Give 2 examples of changes to blood constituents.
- Hyperviscosity
- Post traumatic hypercoagulability
What can cause stasis?
- Post-op
- Economy class syndrome
What can cause turbulence?
- Atheromatous plaque
- Aortic aneurysm
What do consequences of thrombosis depends on?
- Site
- Extent
- Collateral circulation
What are common clinical scenarios related to thrombosis?
- DVT
- Ischaemic limb
- MI
What are the possible outcomes of thrombosis?
- Resolution
- Organisation/ recanalization
- Death
- Propagation leading to embolism
Embolism
Movement of abnormal material in the bloodstream and its impaction in a vessel , blocking its lumen
Embolus
Detached intravascular solid, liquid or gaseous mass
What are most emboli?
Dislodged thrombi
What do factors causing embolism depend on?
Type of embolus
What are the possible sources of a systemic/arterial thromboembolus?
- Mural thrombus
- Aortic aneurysms
- Atheromatous plaques
- Valvular vegetations
What are mural thrombi associated with?
- MI
- Left atrial dilatation and AF
Where do thromboembolism travel to?
Travel to wide variety of sites:
- Lower limbs most common
- Brain
- Other organs
What do consequences to systemic thromboembolism depend on?
- Vulnerability of affected tissues
- Ischaemia calibre of occluded vessels
- Collateral circulation
- Usually infarction occurs
Where do venous thromboembolus originate from?
Deep venous thrombosis (lower limbs)
What is the most common form of thromboembolic disease?
DVT
Where does DVT travel to?
Pulmonary arterial cicrulation
What may DVT occlude?
Dependent on size:
- Main pulmonary artery
- Bifurcation
- Smaller arteries
What are the possible consequences of DVT?
- Silent
- Pulmonary haemorrhage/infarction
- Right heart failure
- Sudden death
What do multiple PEs over time lead to?
- Pulmonary hypertension
- Right ventricular failure
What are consequences of thromboembolism dependent on/
Size of embolus
What are the risk factors for DVT and pulmonary thromboembolism?
- Cardiac failure
- Severe trauma/burns
- Post-op/post-partum
- Nephrotic syndrome
- Disseminated malignancy
- Oral contraceptive
- Increased age
- Bed rest/ immobilisation
- Obesity
- PMH of DVT
What is the prophylaxis for surgical patients at risk?
- TEDS
- s/c heparin
When do fat embolus occur?
After major fractures
What is affected by fat embolisms?
- Brain
- Kidneys
- Skin
What can gas embolisms cause?
Decompression sickness
How do gas embolisms occur?
N2 forms as bubbles which lodge in capillaries
How can air embolisms enter the body?
- Head and neck wounds
- Surgery
- CV lines
How can tumours cause embolisms?
Spread of the tumour
Who do trophoblast tumours affect?
Pregnant women
What is affected by trophoblast embolisms?
Lungs
Give an example of a condition which can result in septic material forming an embolism?
Infective endocarditis
What are amniotic fluid embolism the cause of?
Collapse +/- death in childbirth
How are bone marrow embolisms formed?
- Fractures
- CPR
How are foreign body embolisms formed?
- Intravascualr cannulae tips
- Sutures
Types of embolisms
- Amniotic fluid
- Bone marrow
- Foreign bodies
- Tumour
- Trophoblast
- Septic material
- Gas
- Air embolus
- Fat
- Venous thromboembolism
- Systemic/ arterial thromboembolism
