Haemodynamic approach to reducing thrombosis and haemolysis in an impeller pump

In the experimental and clinical support of the failing heart, the impeller-type centrifugal pumps continue to be of interest because of their inherent advantages; however, the blood compatibility of these pumps still remains to be improved. From the viewpoint of haemodynamics, thrombosis and haemolysis could be reduced by eliminating the stagnation and turbulence of blood flow within the pump, which frequently takes place near the blood contracting surfaces of the pump, when the impeller contours do not coincide with the stream surfaces of the blood. It is suggested that it could be advantageous to design impeller contours according to the stream surfaces, by solving the partial differential equations of continuity, motion and energy. An impeller shroud and vane based on this approach would be fully rinsed by non-turbulent flow and there would then be neither stagnation nor turbulence within the pump, with the result that thrombosis and haemolysis could be reduced. A new impeller pump, developed according to this method, was evaluated as a left ventricular device in four dogs. The bypass flow was controlled at 40-50% of the total flow, each test lasting 6 h. All of the haematological parameters, measured every 2 h, remained within normal range. There was no thrombosis, and coagulation in the pump was avoided by a small dose of heparin to maintain the activated coagulation time (ACT) under 200" in the experiments.