Daisuke Sugiyama

Simple in vitro testing method for antithrombogenic evaluation of centrifugal blood pumps.

We developed a simple in vitro antithrombogenic testing method using a mock circulation system as used in the hemolysis tests to evaluate the antithrombogenicity of centrifugal blood pumps. This method was not designed to substitute for animal experiments but was intended to be a screening test method for selecting pumps robust enough to operate properly during animal experiments. In this study, we were able to maintain an almost constant activated clotting time for test blood for 10 hours by using both trisodium citrate and calcium chloride. We carried out the in vitro antithrombogenic testing of monopivot type centrifugal blood pumps (models DD3 and DD6) and hydrodynamic bearing pumps (models HH2 and HH7), which were developed at Advanced Industrial Science and Technology. Thrombus formation was not observed in the DD3 or DD6 pumps but occurred in the HH2 and HH7 pumps. The HH2 pump generated thrombi during a 1.5-hour ex vivo test, and the test was terminated. We expect this in vitro testing method to be useful for undertaking evaluations before animal experiments.

Hemocompatibility of a hydrodynamic levitation centrifugal blood pump

A noncontact type centrifugal pump without any complicated control or sensing modules has been developed as a long-term implantable artificial heart. Centrifugal pumps with impellers levitated by original hydrodynamic bearings were designed and have been modified through numerical analyses and in vitro tests. The hemolysis level was reduced by changing the pressure distribution around the impeller and subsequently expanding the bearing gap. Thrombus formation in the bearing was examined with in vitro thrombogenesis tests and was reduced by changing the groove shapes to increase the bearing-gap flow to 3% of the external flow. Unnecessary vortices around the vanes were also eliminated by changing the number of vanes from four to six.

Measurement method comparison to quantify the shear velocity near the casing wall of the blood pump

Quantitative flow visualizations using Particle Tracking Velocimetry (PTV) and Particle Image Velocimetry (PIV) were performed to remove the origin of hemolysis to obtain the suitable design criteria. Particular attention was paid to the relationship between the high shear area and hemolysis. As a result, the shear velocities in the high hemolysis pump were higher than those in the low hemolysis pump near the casing wall by the results of both PTV and PIV. However, the shear velocities by PIV were half times as large as those by PTV in a current comparison.