More to Learn About Acquired Von Willebrand Syndrome.

Abstract

To the Editor: We thank Dr. Mazzeffi and Dr. Tanaka for their comments regarding the role of primary hemostasis for patients receiving extracorporeal membrane oxygenation (ECMO). As they note, emerging data has highlighted the development of acquired von Willebrand syndrome (AVWS) in both adult and pediatric ECMO patients.1–4 The loss of high molecular weight multimers (HMWM) secondary to shear stress from the extracorporeal circuit may lead to impaired platelet activation and therefore increase the risk of bleeding. As the authors mentioned, we have recommended using standard coagulation laboratory testing and viscoelastic hemostatic assays (VHAs) if available to help guide transfusion management.5 While standard coagulation laboratory tests are limited, VHAs produce a comprehensive view of clot formation and fibrinolysis and do in fact measure primary and secondary hemostasis. If bleeding persists in spite of targeted transfusion and decreasing or holding anticoagulation, it may be reasonable to screen for AVWS using von Willebrand factor (VWF) HMWM analysis or functional assays, such as ristocetin cofactor activity (VWF: RCo), VWF activity (VWF: Ac), or VWF:collagen-binding capacity (VWF: CB). Although AVWS may be common in ECMO patients it should be noted that there is a paucity of data regarding the management of AVWS. Before replacing with VWF concentrates, a multidisciplinary discussion including consultation with hematology/transfusion medicine is recommended to devise a strategy tailored to the individual patient weighing the risk of thrombosis and bleeding. We agree that a prospective study is needed to demonstrate appropriate dosing, safety, and efficacy of von Willebrand concentrate for patients with AVWS.