Flashcards in Pathophysiology of Thrombosis and Embolism Deck (33)
What defects in blood flow can result in thrombosis and embolism?
Vascular steal syndrome
What is normal blood flow?
Laminar - smooth and ordered
What is the vascular system affected by?
Compliance of the vessel
What features of blood flow are abnormal?
What is stasis of blood flow?
Stagnation of blood flow e.g. in cardiac failure where there is not enough force to push the blood
What is turbulence of blood flow?
Forceful, unpredictable flow e.g. due to something protruding into the lumen such as an atheromatous plaque
Noisy on auscultation
What are the components of Virchow's triad?
Changes in blood vessel wall
Changes in blood constituents
Changes in pattern of blood flow
What is the most important risk factor for thrombus formation?
What is thrombosis?
Formation of a solid mass from the constituents of blood within the vascular system during life
What steps are involved in the pathogenesis of thrombosis?
Stasis or turbulent flow
Hypercoagulability of the blood
What effect does an atheromatous plaque have on blood flow when it starts to protrude from the lumen?
Starts to cause turbulent flow
What does turbulent blood flow cause?
Damage to the endothelial surface - loss of intimal cells and denuded plaque
What happens when the endothelial surface is lost due to turbulent flow?
Collagen in the fatty core of the plaque is exposed to the blood, platelets in the blood then stick to the collagen and form a fibrin meshwork which traps the RBCs
What do alternating bands of fibrin and RBCs form?
Lines of Zahn
What do the consequences of thrombosis depend on?
What are common consequences of thrombosis?
What are possible outcomes of thrombosis?
May relieve itself but often medical intervention is needed to break down the platelets and restore blood flow
What will organisation/recanalisation cause?
Restoration of blood flow, but tissue damage may still occur as thrombus is stabilised, endothelial surface grows and fibrosis and granulation can occur along with the formation of new blood vessels
What is embolism?
Movement of abnormal material in the blood stream and its impaction in a vessel, blocking its lumen
What substances can form an embolus?
Detached intravascular solid, liquid or gaseous mass
What are most emboli formed from?
What are some causes of thromboembolism?
What are the features of a systemic thromboembolism?
Travels to a wide variety of sites - lower limbs most common but brain and other organs also affected
Usually infarction occurs
What do the consequences of a systemic thromboembolism depend on?
Vulnerability of the affected tissues to ischaemia
Calibre of occluded vessel
Where do most venous thromboembolisms originate from?
Deep venous thromboses in the lower limbs
What is the most common form of thromboembolic disease?
Where do venous thromboembolisms travel to? What can this cause?
Pulmonary arterial circulation
May occlude the main pulmonary artery, bifurcation or small arteries
What do the consequences of a venous thromboembolism depend on?
Size of the embolus
What are the potential consequences of venous thromboembolism?
May be silent
Right heart failure