Contour shuttle works intermittently1/23/2024 ![]() Įxtant studies on the hemolysis and cleavage of the VWF associated with increasing shear flow were based on in vitro tests that used Couette-type blood shearing devices to determine empirical constants, including the thresholds of blood trauma activation. Previously, empirically estimated hemolysis or VWF degradation models were developed to predict the concentration and accumulation of shear flows in MCSs through their development processes. Large multimers with high-molecular-weight VWF are extended by the fluid forces in a shear flow and are cleaved by ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) under high shear stress flow conditions in the cardiovascular system. The shear stresses induced by the designs of the MCSs or cannulations are anticipated to be a critical cause of nonsurgical and nonphysiological lysis of blood and degradation of the von Willebrand factor (VWF). The plasma-free hemoglobin levels showed a logarithmic increase corresponding to the number of cycles, and the dissipation of large VWF multimers occurred within a few seconds under high shear stress flow conditions.Ĭhronic blood trauma caused by shear stresses generated by mechanical circulatory support (MCS) systems is one of the major concerns to be considered during the development of ventricular assist devices. The influence of exposure time, in terms of the number of stress cycles, on hemolysis and VWF degradation was confirmed using fresh goat blood, and the differences in the rates of dissipation of the multimers were established. The device consisted of a pair of cylinders facing the test section of a small-sized pipe both the cylinders were connected to composite mechanical heads with a sliding-sleeve structure for axial separation during the withdrawing motion. In this study, the shear stress (~ 600 Pa) and exposure time related to hemolysis and VWF degradation were investigated using a newly designed mechanical shuttle shear flow tester. Since the mechanical revolving motions in artificial MCSs induce cleavage in large VWF multimers, nonsurgical bleeding associated with the MCS is likely to occur after mechanical hemodynamic support. Large multimers with high-molecular-weight von Willebrand factor (VWF) are extended by the fluid forces in a shear flow and are cleaved by ADAMTS13. Chronic blood trauma caused by the shear stresses generated by mechanical circulatory support (MCS) systems is one of the major concerns to be considered during the development of ventricular assist devices.
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