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Von Willebrand Disease (VWD)
Part 1: NHLBI Diagnosis Guidelines

Introduction & Clinical Assessment Recommendations



VWF and Normal Hemostasis1

Slide 4

May 2011

This cartoon about VWF and normal hemostasis illustrates some of the VWF biology we just reviewed, and demonstrates key roles for VWF in hemostasis and vascular biology.

In the upper panel, showing blood flowing in a small arteriole lined by endothelium, VWF multimers bind factor VIII molecules; however, the blood platelets do not interact with VWF — because the platelet-binding domains in VWF are hidden internally in the globular VWF polymer.

In the middle left panel, blood vessel damage allows exposure of the sub-endothelial tissues — that contain collagen and other adhesive proteins — then VWF adheres via its collagen-binding domains. In the middle right panel, high blood flow shear stress in the microvasculature uncoils and stretches VWF multimers, exposing binding sites for platelets that become activated during this process. The larger the VWF multimer, the more attractive it is for capturing platelets from the flowing blood to form a primary (1°) hemostatic plug.

In the bottom left panel, adherent activated platelets expose negatively-charged phospholipids such as phosphatidylserine which, in turn, binds and coordinates interactions of plasma coagulation factors (including factor VIII) to accelerate thrombin generation. In the bottom right panel, secondary hemostasis strengthens the hemostatic plug by creating a fibrin meshwork around platelets. Subsequently, fibrinolysis is activated and the processes of blood vessel repair and healing evolve, leading to restoration of blood flow.

VWF and Normal Hemostasis1

 


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