EFFECT OF PRESSURE-FLOW RELATIONSHIP OF CENTRIFUGAL PUMP ON IN-VIVO HEMODYNAMICS - A CONSIDERATION FOR DESIGN

We have been developing centrifugal pumps for an implantable left vent ricular assist device. We manufactured 2 prototype centrifugal pumps ( PI, PII). These two have similar designs except for the PII having a v olute casing and a large output port. To determine the differences in the hydraulic characteristics between the PI and PII, we carried out i n vitro and in vivo experiments. In vitro study showed that the PII ha d a shallower H-Q curve than that of the PI, and the PII required a pu mp speed faster than the PI for the same flow rate and pressure head. On the other hand, in vivo study showed that the PII demonstrated a fl ow pulsatility greater than that of the PI at 1,900 rpm and 8 L/min al though no significant change was observed at low pump speeds (less tha n or equal to 1,500 rpm). This greater pulsatility consisted of a larg e discharge according to the small differential pressure during the sy stolic phase and a small discharge according to the large differential pressure during the diastolic phase. In contrast, the PI, having the steeper H-Q curve, showed a small discharge in the systolic phase and a large discharge in the diastolic phase. These results showed that pu lsatility synchronized with the native heart beating depended on the s lope of the H-Q curve. As a result, the slope of the H-Q curve is impo rtant to determine the component of pulsatility synchronized with nati ve cardiac output. Regarding the slope of the H-Q curve, a pump having a volute casing and a large outlet port demonstrates a shallow slope in the H-Q curve. In conclusion, we suggest that a centrifugal pump fo r use In left ventricular aortic bypass should be designed considering the effect on the native heart pulsatility.