Haemostasis 4 Flashcards
(68 cards)
What is the gene coding for von Willebrand Factor (vWF) located?
Chromosome 12
The gene responsible for vWF production plays a crucial role in haemostasis.
Where is von Willebrand Factor synthesized?
Megakaryocytes and endothelial cells
These cells are responsible for the production of vWF and its release into the bloodstream.
What stabilizes Factor VIII (FVIII) when bound?
von Willebrand Factor (vWF)
Binding to vWF significantly increases the half-life of FVIII.
What is the role of ADAMTS13?
It cleaves large vWF multimers
This action prevents excessive clotting by regulating vWF size.
What occurs to von Willebrand Factor under shear forces of blood flow?
It uncoils
This uncoiling allows vWF to bind to platelets and collagen.
List the effects of reduced plasma vWF levels.
- Reduced platelet adhesion
- Reduced platelet aggregation
- Prolonged bleeding
- Increased bruising
These effects are characteristic of von Willebrand Disease.
What is the frequency of von Willebrand Disease (VWD) in the population?
1:500 – 1:1000
This indicates that about 1% of the population is affected by VWD.
What are the inheritance patterns of von Willebrand Disease?
- Autosomal Dominant (AD)
- Autosomal Recessive (AR)
The inheritance pattern varies depending on the type of VWD.
What are the clinical signs of Von Willebrand Disease?
- Mucosal bleeding
- Frequent nosebleeds
- Heavy menstruation
- Easy bruising
- Prolonged bleeding from cuts
These symptoms result from impaired platelet function.
What are the standard tests for diagnosing von Willebrand Disease?
- CBC
- APTT
- PT
- Fibrinogen
- vWF:Ag
- vWF:Activity
- FVIII:C
These tests help assess the levels and functionality of vWF and FVIII.
What is the defect in Type 1 von Willebrand Disease?
Partial quantitative deficiency of vWF
This type is characterized by a lower than normal amount of vWF in the blood.
What is a common treatment for von Willebrand Disease?
- Desmopressin (DDAVP)
- Blood product: FVIII-vWF
- Tranexamic acid
These treatments aim to increase vWF/FVIII levels or inhibit fibrinolysis.
What does tranexamic acid do?
Blocks the activation of plasmin
This action helps stabilize clots and is used in various bleeding scenarios.
How does heparin function as an anticoagulant?
Binds to antithrombin and increases its activity
This enhances the inhibition of thrombin and other coagulation factors.
What is the half-life of heparin?
Approximately 50 minutes
This short half-life necessitates careful monitoring during therapy.
What type of bleeding is associated with vascular bleeding?
- Senile purpura
- Prolonged steroid medication
- Scurvy
- Hereditary hemorrhagic telangiectasia
- Angiodysplasia
- Vasculitis
These conditions can lead to fragile blood vessels and bleeding.
What is a key difference between Haemophilia and von Willebrand Disease?
Haemophilia is X-linked, while VWD is autosomal dominant
This distinction affects inheritance patterns and prevalence.
What is the role of thrombin in coagulation?
Activates platelets via thrombin receptors
Thrombin is a central enzyme in the coagulation pathway.
What tests are useful to diagnose bleeding conditions?
- Platelet count
- Coagulation screen (PT, APTT)
- PFA-100/200
These tests help identify abnormalities in blood coagulation and platelet function.
What is the normal reference interval for platelet count?
150-400 x10^9/L
What is the normal reference interval for fibrinogen levels?
1.8-4.0 g/L
What is the normal reference interval for APTT?
22-36 s
What is the normal reference interval for PT?
9-13 s
What is the condition of the patient in Case 1?
Severe thrombocytopenia
