Magnetically Suspended Centrifugal Pump as an Implantable Ventricular Assist System

Summary

We have been developing a magnetically suspended centrifugal pump (MSCP) for long-term use. The pump eliminates the need for a shaft seal. The shaft seal limits the life of conventional centrifugal pumps due to blood leakage and thrombus formation around the shaft. An in vitro hemolysis test revealed that the MSCP was less harmful than the Biopump with respect to destruction of blood components. In an ongoing series of animal experiments, pumps have been placed extracorporeally in sheep for extended times. So far, seven sheep have under gone implantation of the MSCP, for up to 46 days. The pump flow rate was 2.5–5.01/min under a pressure head of 100–140 mmHg. In parallel with the animal experiments, we have started to develop an implantable version for long-term use. The size and weight was markedly reduced (82 mm in total diameter, 50.5 mm in width, and 420g in weight). A sensorless system which eliminates the flow meter and/or pressure sensors has also been investigated and showed good correlation to direct measurement in vivo. The power required was 15W (9W for magnetic suspension and control system, 6W for driving motor), and this will be reduced to 12.5 W in the future. The implantable version of the MSCP is a promising device for long-term clinical use.