VWF and acquired von willebrand syndrome: Since the pathomechanism of ECMO-induced AVWS involves the loss of HMW VWF multimers, standard testing for quantitative and qualitative VWF deficiencies (VWF activity assay (VWF:Act), VWF antigen assay (VWF:Ag), and VWF/collagen binding assay (VWF:CB)) may not be able to sufficiently reflect the impaired VWF function.