Blood: 4.4: Thrombosis Flashcards
What is the most common location of a thrombus?
DVT (below the knee)
Where can intravascular blood clots occur abnormally?
any artery or vein
A thrombus is characterized by _____ and _____, as opposed to a postmortem clot.
lines of Zahn; attachment to vessel wall
What is a lines of Zahn?
RBC and fibrin streaks in an alternating pattern
What are the 3 major risk factors for thrombosis?
- disruption of blood flow2. endothelial cell damage3. hypercoagulable state** Virchow’s triad
How does disrupted blood flow contribute to thrombi?
stasis or turbulence change normal laminar flow, allowing clots to occur
Name 3 examples of disrupted blood flow.
- immobilization2. cardiac wall dysfunction (A-fib, MIs)3. aneurysm
How does endothelial damage cause thrombi?
endothelium normally protects against coagulation (produces PGI2, NO, heparin-like molecules, TPA, thrombomodulin), but damaged endothelium starts clotting cascade (hides subendothelial collagen and TF)
What does thrombomodulin do?
it alters thrombin so that it can activate protein C*protein C then inactiavates factors V and VIII (5 and 8)
What can cause endothelial damage?
- athrosclerosis2. vasculitis3. high levels of homocystein
Why does serum homocystine increase?
- vitamin B12 or folate deficiency 2. cystathionine beta synthase (CBS) deficiency
What is cystathionine beta synthase (CBS) deficiency?
a genetic deficiency of the enzyme that converts homocystine into cystathionine, characterized by homocystinuria, vessel thrombosis, mental retardation, lens discolorations, and long, slender fingers
What causes hypercoagulable states?
- excessive procoagulants2. defective anticoagulant proteins* can be inherited or acquired
What is the classic presentation of a hypercoagulable pt?
recurrent DVTs or DVTs in young age (can also be in the hepatic and cerebral veins)
_____ and ____ inactivate factors V and VIII.
Protein C and Protein S
Which drug’s administration b itself should be avoided in Protein C and Protein S deficient pts?
Coumadin/warfarin
Coumadin/warfarin blocks the enzyme _____ in the liver.
epoxide reductase
What is warfarin skin necrosis?
thrombi in the skin, causing infarcts and necrosis
Which vitamin K dependent factors have the shortest half-lives and will be degraded first?
Protein C and Protein S
What is Factor V Leiden?
genetic mutation of factor V that makes it impossible to be deactivated by protein C and protein S–> excessive factor V activity* the most common INHERITED cause of a hypercoagulable state
What is Prothrombin 20210A?
a genetic mutation of prothrombin that causes its increased gene expression and promotes thrombus formation
What does thrombin do?
converts fibrinogen into fibrin for clot formation
What does ATIII stand for?
Antithrombin III
What is ATIII deficiency?
lack of molecule that the heparin-like molecules (HLM) can bind to, so there’s increased risk of clot formation
