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Low hemolysis is an important factor for axial blood pumps that has been used in patients with heart failure. The structure of impellers plays a key role in the hemolytic properties of axial blood pumps. Axial blood pumps with various structure impellers exhibit different hemolytic characteristic. In the present study, we aimed to investigate the type of impellers structures in axial blood pumps that contain the best low hemolytic properties. Also, it is expensive and time-consuming to validate the axial blood pump's hemolytic property by in vivo experiments. Therefore, in the present study, the numerical method was applied to analyze the hemolytic property in a blood pump. Specifically, the hemolysis of the pump was calculated by using a forward Euler approach based on the changes in shear stress and related exposure times along the particle trace lines. The different vane structures and rotational speed that affect hemolysis were analyzed and compared. The results showed that long–short alternant vanes exhibited the best hemolytic property which could be utilized in the optimization design of axial blood pumps.

Low hemolysis and hydraulic performance are important factors for an axial blood pump, which have been transplanted in patients with heart failure (HF). The distance and clearance between impeller and diffuser play a key role in hemolytic properties and hydraulic performances of axial blood pumps that were developed by our group inspired by the design features of HeartMate II. In the present study, we aimed to investigate the appropriate distance and clearance between impellers and diffusers of axial blood pumps, which contains the best low hemolytic property and hydraulic performance using the computational fluid dynamics (CFDs) approach. Specially, the hemolysis of the pump was calculated by using two different empirical power-law hemolytic blood damage models with two sets of parameters. The two hemolytic blood damage models with two sets of parameters were analyzed and compared. Further, the different distances and clearances between impellers and diffusers that affect hemolytic and hydraulic characteristics were also analyzed. The results showed that the pump with distance of 2mm and clearance of 0.2mm between impeller and diffuser exhibited the best hemolytic property and better hydraulic performance.

Artificial prostheses create non-physiologic flow conditions with stress forces that may induce blood cell damage, particularly hemolysis. Earlier computational fluid dynamics (CFD) prediction models based on a quantified power model showed significant discrepancies with actual hemolysis experiments. These models used the premise that shear stresses act as the primary force behind hemolysis. However, additional studies have suggested that extensional stresses play a more substantial role than previously thought and should be taken into account in hemolysis models. We compared extensional and shear stress flow fields within the contraction of a short capillary with sharp versus tapered entrances. The flow field was calculated with CFD to determine stress values, and hemolysis experiments with porcine red blood cells were performed to correlate the effects of extensional and shear stress on hemolysis. Our results support extensional stress as the primary mechanical force involved in hemolysis, with a threshold value of 1000 Pa under exposure time less than 0.060 ms.