Pulsatile impeller heart: a viable alternative to a problematic diaphragm heart.

The impeller blood pump with its simplicity has many advantages compared with the diaphragm pump, but the nonpulsatile property has limited its applications. To make the impeller pump pulsatile, many investigations have been made in vain because of resulting haemolysis. The author has succeeded in producing a pulsatile blood flow with a centrifugal pump, by means of the streamlined design of the impeller. The vane and shroud coincide with the blood stream surface in the pump, to eliminate the turbulence and stasis of the blood flow, which are the main factors in haemolysis and thrombosis. The pulsatility of the blood pressure and flow rate is achieved by changing the rotating speed of the impeller periodically, by introducing a square wave form voltage into the motor coil. The velocity variation of the blood cells due to the changing rotating speed of the impeller is minimized by using twisted impeller vanes, thus reducing the additional Reynolds shear, which causes the additional haemolysis in the pump. In vitro testing demonstrated that the haemolysis index of the pulsatile impeller pump is slightly higher than that of the author's nonpulsatile impeller pump but clearly less than that of other pulsatile blood pumps. The in vivo evaluations indicated that no blood damage occurred and that all haematological and biochemical data kept within a normal range during left ventricular assist experiments in calves for up to 11 days. A pulsatile impeller total heart has been developed. Two pumps are located on both sides of and driven by a d.c. motor. As the motor changes its rotating speed periodically, the left and right pumps eject the blood simultaneously, and the volume equilibrium of both pumps is achieved naturally. Acute biventricular assist experiments in pig confirmed that the device caused no blood damage.