DEVELOPMENT OF A CENTRIFUGAL PUMP WITH IMPROVED ANTITHROMBOGENICITY AND HEMOLYTIC PROPERTY FOR CHRONIC CIRCULATORY SUPPORT

A centrifugal pump with a unique structure has been developed for chro nic support. The pump is driven by a magnetic coupling and has no rota ting shaft, no seal around the rotating part, and a balancing hole at the center of the impeller and the thrust bearing. The pump was improv ed in stepwise fashion to realize good antithrombogenicity and low hem olysis. The first pump, the National Cardiovascular Center (NCVC)-0, h ad an impeller with 4 rectangular and curved vanes; 6 triangularly sha ped curved vanes were employed in the second model, the NCVC-1, to red uce trauma to the blood. In the third design, the NCVC-2, the central hole was enlarged, and the thrust bearing shoulder was rounded so that blood washing was enhanced around the impeller; stream lines also wer e smoothed for improved antithrombogenicity. The hemolytic property of the device was evaluated in vitro with heparinized fresh goat blood; hemolysis indexes of the NCVC-0, -1, and -2 were 0.05, 0.01, and 0.006 g per 100 L, respectively. Antithrombogenicity of the pumps was exami ned in animal experiments as a left heart bypass device in goats weigh ing 52-75 kg. Six NCVC-0 pumps were driven for 14 to 33 (22.0 +/- 7.6) days in goats receiving the antiplatelet drug cilostazol orally. Four NCVC-1 pumps ran for 1 to 80 (28.5 +/- 30.6) days with the same drug regimen in 2 cases and with no anticoagulation therapy in 2 cases. Aft er 3 preliminary 1-week tests of NCVC-2 pumps in animals, the pump was installed in 3 goats; 2 pumps were still running on the 182nd and 58t h pumping day. Intracorporeal implantation also was attempted successf ully. The results indicate that this pump has promising features for c hronic support although longer term and additional evaluations are nec essary.