Pathophysiology of thrombosis and embolism Flashcards
What is normal blood flow ?
Laminar
What is stasis ?
Stagnation of flow
What is turbulence ?
Forceful, unpredictable flow
What are the causes of common defects in blood flow ?
Thromboembolism Atheroma Hyperviscocity Spasm External compression Vasculitis vascular steal
What is Virchow’s triad ?
Changes in the blood vessel wall
Changes in blood constituents
Changes in patterns of blood flow
What does Virchow’s triad influence ?
Factors causing thrombosis
What is the basic pathogenesis of thrombosis ?
Endothelial injury
Stasis or turbulent blood flow
Hypercoagubility of the blood
What are lines of Zahn on a thrombus ?
Represent bands of fibrin (lighter) with entrapped white blood cells and red blood cells (darker)
What causes the adherence of platelets ?
Loss of intimal cells and the exposure of collagen
What traps red blood cells in a blood clot ?
Fibrin meshwork
What is responsible for the propagation of thrombosis ?
Further turbulence and platelet deposition
What is the relationship between atheroma and thrombosis ?
Arterial thrombosis most commonly superimposed on atheroma; Virchow’s triad
What is an example of changes in blood vessel wall ?
Atheromatous coronary artery
What is an example of changes in blood constituents ?
Hyperviscocity, post-traumatic hypercoagulability
What is an example of changes in patterns of blood flow ?
Stasis: economy class syndrome, post-op Turbulence: atheromatous plaque, aortic aneurysm
What do the consequences of thrombosis depend on ?
Site
Extend
Collateral circulation
What are common clinical scenarios of thrombosis ?
DVT
Ischaemic limb disease
What is the outcome of thrombosis ?
Resolution
Organisation/recanalization
Death
Propagation-> embolism
What is an embolism ?
Movement of abnormal material in the bloodstream and its impaction in a vessel, blocking its lumen
What is an embolus ?
Detached intravascular solid, liquid or gaseous mass
What is the most common type of emboli ?
Thromboembolism- dislodged thrombi
What is a systemic/arterial thromboembolism ?
Mural thrombus Aortic aneurysms atheromatous plaques Valvar vegetations Venous thrombi - paradoxical emboli
What are mural thrombi associated with ?
Myocardial infarction or left atrial dilation and atrial fibrillation
Where can a systemic thrombus travel to ?
Wide variety of sites: lower limbs most common, brain and other organs
What is the usual result of a systemic thromboembolism ?
Usually infarction
Consequences depend on vulnerability of affected tissues to ischaemia, calibre of occluded vessel, collateral circulation
What is a venous thromboembolism ?
Originate from deep venous thromboses (lower limbs)
Most common form of thromboembolic disease
Where do venous thromboembolism usually travel and occlude ?
Travel to the pulmonary arterial circulation, may occlude the main pulmonary artery, bifurcation or smaller arteries
What are the possible consequences of thromboembolism ?
Depend on size of embolus: silent, pulmonary haemorrhage/infarction, right heart failure, sudden death
Multiple PE over time: pulmonary hypertension and right ventricular failure
What are other types of embolism ?
Fat: - After major fractures - Syndrome of fat embolism: brain, kidneys, skin affected Gas: - Decompression sickness - N2 forms as bubbles which lodge in capillaries Air embolus: - Head and neck wounds, surgery, CV lines Tumour: - Spread of tumour Trophoblast: - Pregnant women- lungs Septic material: - E.g. Infective endocarditis Amniotic fluid: - Cause of collapse (+/- death) in childbirth Bone marrow: - Fractures; CPR Foreign bodies: Intravascular cannula tips, sutures, etc
What are risk factors for deep vein thrombosis and pulmonary embolism ?
Cardiac failure Severe trauma Burns Post op Post partum (following childbirth) Nephrotic syndrome disseminated malignancy Oral contraceptive Increased age Bed rest/immobilisation Obesity Past medical history of deep vein thrombosis
