Gastrointestinal bleeding occurs in 20–30% of patients receiving ventricular assist devices (VADs) due, in part, to acquired von Willebrand syndrome. We examined factors to optimize a benchtop method to quantify changes in von Willebrand Factor (VWF) multimer distribution and function in VADs, then applied them to evaluate commercially available devices. Human plasma was circulated through flow loops with VADs. Several experimental conditions were examined, including temperature, viscosity, and enzyme inhibition. Samples were analyzed for VWF collagen-binding activity (VWF:CB) and VWF antigen level. von Willebrand Factor multimer profiles were quantified using gel electrophoresis, near-infrared in-gel visualization, and densitometric analysis. The VWF:CB/antigen ratio in the HeartMate II, CentriMag, and HVAD exhibited average decreases of 46%, 44%, and 36% from baseline after 360 minutes of operation. High molecular weight (hVWF) multimer loss occurred within 30 minutes, although the Levacor and control loop profiles were unchanged. Varying temperature and viscosity altered hVWF degradation rate, but not the final results. Inhibition of a disintegrin and metalloprotease with thrombospondin type 1 repeats, member 13 (ADAMTS13) can potentially distinguish mechanoenzymatic cleavage of VWF from mechanical degradation. We developed a repeatable benchtop method to evaluate VWF compatibility of VADs similar to hemolysis testing that can be adopted for preclinical VAD evaluation.
From the *VADovations, Inc., Oklahoma City, OK
†INTEGRIS Advanced Cardiac Care, INTEGRIS Baptist Medical Center, Oklahoma City, OK.
Submitted for consideration August 2016; accepted for publication in revised form May 2018.
Disclosure: Phillip Coghill, Suren Kanchi, Zheila J. Azartash-Namin, and Trevor Snyder are employees of VADovations.
This work was supported in part by NIH grants R44HL114246, R44HL118907, and R21HL115601.
Correspondence: Trevor A. Snyder, 1333 Cornell Pkwy, Oklahoma City, OK 73108. Email: firstname.lastname@example.org.