Reduced continuous-flow left ventricular assist device speed does not decrease von Willebrand factor degradation

Abstract

Reduced LVAD speed (within the clinical operational range) did not significantly decrease vWF degradation in a mock circulatory loop with human blood. During bleeding events, reduced LVAD speed, itself, may not diminish vWF degradation.

Clinical and In Vitro Evidence That Subclinical Hemolysis Contributes to LVAD Thrombosis

“…To reproduce blood trauma from a continuous-flow LVAD, we previously developed a tightly controlled ex vivo LVAD model that generates continuous-flow LVAD-like supraphysiologic shear stress. The model produces the same profile of vWF degradation [5,12,13] and platelet activation [14] as patients with a continuousflow LVAD. Briefly, plasma was exposed to a continuous cyclone spin in a laboratory vortexer (Vortex Genie-2, Scientific Industries, Bohemia, NY) at a shear stress of approximately 175 dyne/cm 2 .…”

“…High-molecular-weight plasma vWF multimers and fragments were evaluated with standard agarose and polyacrylamide electrophoresis, respectively, as previously described in detail [5,[12][13][14][15]. Proteins were transferred to polyvinylidine difluoride membranes, blocked, and incubated with rabbit antihuman vWF primary antibody (1:500, Dako, Carpinteria, CA) and goat antirabbit immunoglobulin G horseradish peroxidase (HRP)-conjugated secondary antibody (1:3,000, Cell Signaling, Danvers, MA).…”

“…ImageJ software version 1.5 (National Institutes of Health, Bethesda, MD) was used to measure the chemiluminescent intensity of immunoblots from control, shear, and shear þ pfHgb samples. Images, which contained serial samples from the same subject, underwent differential contrast enhancement to highlight biological changes [12].…”

Decreased RPM reduces von Willebrand factor degradation with the EVAHEART LVAS: implications for device‐specific LVAD management

“…High‐molecular‐weight VWF multimers were quantified as previously described 7,14,16‐21 . Plasma was combined 1:20 in loading buffer (10 mM Tris‐HCl, 2% sodium dodecyl sulfate [SDS], 8M urea, 1 mM ethylenediaminetetraacetic acid, bromophenol blue, pH 8.0) and heated to 60°C for 20 minutes.…”

“…VWF degradation fragments were quantified as previously described 7,14,16‐21 . Plasma was combined 1:40 with NuPAGE LDS Sample Buffer (Thermo Fisher Scientific) and incubated (10 minutes, 70°C).…”