In Vitro and Preliminary In Vivo Assessment of a New Centrifugal Pump: the Magnetically Suspended Centrifugal Pump

To overcome problems derived from the shaft within conventional centrifugal pumps, we have developed a new centrifugal pump, namely, the magnetically suspended centrifugal pump (MSCP), which has no shaft and operates as a noncontacting and bearingless pump. This impeller is suspended magnetically between the magnetic bearing and the driving motor. Hemolysis tests were performed and results were compaired with those for the Biopump (BP-80; Medtronic Bio-Medicus, Eden Prairie, MN, USA). The test conditions were: 51/min of pumping flow rate, and 150 mmHg pressure. The index of hemolysis was significantly lower for the MSCP than for the Biopump, despite the higher rotation rate of the MSCP. Moreover, in the MSCP, platelets were significantly preserved, and the change in the temperature of the test circuit was significantly lower, indicating the superior pumping efficiency of the MSCP compared to the Biopump. In addition, hemolysis tests were performed by changing the gap between the impeller and the pump housing in the MSCP from 0.15 mm to 0.25 mm to determine the optimal gap. The smaller gap resulted in lower hemolysis and lower destruction of platelets. In studies in dogs, an MSCP with a non-coated impeller developed a layer of white thrombus adherent to the impeller surface of polycarbonate, which impaired the pumping efficiency. However, the MSCP with an impeller coated with silicone to a thickness of 100 Å did not show aggregations of platelets or fibrin on the impeller in continuous pumping of 24 h. In conclusion, the MSCP has a more gentle influence on blood cells compared to the Biopump and may be one of the most promising centrifugal pumps for long-term cardiac assist.