Problem and Solution on Clinical Application of Magnetically Suspended Centrifugal Blood Pump as Implanted Assist Heart

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1) Study 1This study was designed to investigate how the inflow cannulation site of the left ventricular assist system (LVAS) with centrifugal pump would influence cardiac function on failing heart models. In 10 sheep, LVAS was instituted by two inflow cannulae in the left atrium (LA) and the left ventricle (LV), and connecting those cannulae to a magnetically suspended centrifugal pump. The pump flow with LV cannulation increased during the systolic phase and decreased during the diastolic phase, while it was constant with LA cannulation. Ejection fraction with LA cannulation decreased as the assist rate increased, while that with LV cannulation was maintained up to 75% assist. The external work with LA cannulation decreased gradually as the assist rate increased, while the EW with LV cannulation did not decrease until the assist rate reached 75%. The myocardial oxygen consumption of both cannulation decreased proportionally as the assist rate increased, and were significantly less wi … More th LV cannulation at the 100% assist rate than with LA cannulation. The LV cannulation during LVAS maintains EF, and provides effective reduction in oxygen consumption.2) Study 2Control system of centrifugal pump in response to necessary demanding of body was devised. An inflection point was set on P-Q curve (Relationship between pressure head and flow). We set two modes of pump control: one is the disease mode with steep slope where the pump flow is less than the inflection point, and the other is the healthy mode with mild slope where the pump flow is more than the inflection point. The disease mode was well operated to keep the minimal pump flow rate. However, the healthy mode did not work well.3) Study 3Estimation of the heart recovering from failing was assessed by only pump parameters. The LV pressure and electricity current were recorded simultaneously. The pump flow increased as the LV pressure increased with some delay. The change between electricity-current and pump flow had phase difference. Therefore, we needed correction formula to estimate LV pressure. Less