Decreased active von Willebrand factor level owing to shear stress in aortic stenosis patients

Background: Aortic stenosis patients often show bleeding complications. Previously, a prolonged platelet function analyzer (PFA-100) closure time was observed with plasma of severe aortic stenosis patients. To elucidate a possible role of circulating preactivated von Willebrand factor (VWF), we determined the level of VWF in its active, platelet-binding conformation in plasma of patients with aortic stenosis. Patients/methods: Sixty-two aortic stenosis patients were included in this study. VWF and related parameters were measured, and the results were related to severity of aortic stenosis. Results: VWF activation factor, indicating the proportion of circulating VWF able to bind to platelets, correlated negatively with peak transvalvular gradient and PFA-100 closure time. No correlation was observed between ADAM-TS13 activity and peak transvalvular gradient or PFA-100 closure time. Both VWF antigen and VWF propeptide levels were significantly higher in patients with mild and moderate aortic stenosis, but not in those with severe stenosis. Conclusions: Our data demonstrate that the aortic pressure gradient is inversely associated with VWF activation factor, but not with VWF antigen or VWF multimerization in patients with aortic stenosis. These findings might have implications for the bleeding observed in patients with aortic stenosis.