Ex vivo experimental thrombosis in variants of von Willebrand disease

In order to compare quantitative and qualitative abnormalities of von Willebrand factor (vWF) in mediating platelet adhesion and thrombus formation, we performed ex vivo perfusion studies with native blood from patients with various types of von Willebrand disease (vWD). We studied twenty-seven patients having either a quantitative (types I, III) or a qualitative (type II) abnormality of vWF. At high shear rate (2600 s-1) we found that the defect in platelet collagen interactions in type I vWD was at the level of thrombus formation whereas platelet adhesion was normal. In the patients with a qualitative abnormality of vWF (type II), platelet adhesion and thrombus formation were markedly decreased at high shear conditions, indicating that the interaction of normal vWF with the platelet glycoprotein Ib is an essential initial step in platelet collagen interaction

The role of platelet von Willebrand factor in platelet adhesion and thrombus formation : a study of 34 patients with various subtypes of type I von Willebrand disease

In order to investigate the respective role of plasma and platelet von Willebrand factor (vWF) in mediating platelet adhesion and thrombus formation, we performed ex vivo perfusion studies with native blood from patients with various subtypes of type I von Willebrand disease (vWD). We studied 34 patients with type I vWD (19 'platelet normal', five 'platelet low', two 'platelet discordant', eight 'Vicenza'). Parallel studies were carried out on nine patients with severe vWD (type III). At high shear rate (2600 s-1) we found that the defect in platelet-vessel wall interactions in patients having a normal platelet vWF content ('platelet normal' and 'Vicenza') involved thrombus formation, whereas platelet adhesion was normal. At this high shear rate, platelet adhesion and thrombus volume were significantly decreased in patients with subtypes 'platelet low' and 'platelet discordant', i.e. when platelet vWF is either low or dysfunctional. These results indicate that platelet vWF may substitute for plasma vWF to promote platelet adhesion, emphasizing the important role of platelet vWF. They also confirm the role of vWF in thrombus formation at high shear rate because an abnormal thrombus volume was observed in all patients, even when platelet adhesion was normal