Development of the NEDO implantable ventricular assist device with Gyro centrifugal pump

The Gyro centrifugal pump, PI (permanently implantable) series, is being de veloped as a totally implantable artificial heart. Our final goal is to est ablish a "functional TAH," a totally implantable biventricular assist syste m (BiVAS) with centrifugal pumps. A plastic prototype pump, Gyro PI 601, wa s evaluated through in vitro and in vivo studies as a single ventricular as sist device (VAD). Based upon these results, the pump head material was con verted to a titanium alloy, and the actuator was modified. These titanium G yro pumps, PI 700 series, also were subjected to in vitro and in vivo studi es. The Gyro PI 601 and PI 700 series have the same inner dimensions and ch aracteristics, such as the eccentric inlet port, double pivot bearing syste m, secondary vane, and magnet coupling system; however, the material of the PI 700 is different from the PI 601. The Gyro PI series is driven by the V ienna DC brushless motor actuator. The inlet cannula of the right ventricul ar assist system (RVAS) specially made for this system consists of 2 parts: a hat-shaped silicone tip biolized with gelatin and an angled wire reinfor ced tube made of polyvinylchloride. The pump-actuator package was implanted into 8 calves in the preperitoneal space, bypassing from the left ventricl e apex to the descending aorta for the left ventricular assist system (LVAS ) and bypassing the right ventricle to the main pulmonary artery for the RV AS. According to the PI 601 feasibility protocol, 2 LVAS cases were termina ted after 2 weeks, and 1 LVAS case and 1 RVAS were terminated after 1 month . The PI 700 series was implanted into 4 cases: 3 LVAS cases survived for a long term, 2 of them over 200 days (72-283 days), and 1 RVAS case survived for 1 month and was terminated according to the protocol for a short-term antithrombogenic screening and system feasibility study. Regarding power co nsumption, the plastic pump cases demonstrated from 6.2 to 12.1 W as LVAS a nd 7.3 W as RVAS, the titanium pump cases showed from 10.4 to 14.2 W as LVA S and 15.8 W as RVAS. All cases exhibited low hemolysis. The renal function and the liver function were maintained normally in all cases throughout th ese experimental periods. In the 2 RVAS cases, pulmonary function was norma lly maintained. No calves demonstrated thromboembolic signs or symptoms thr oughout the experiments except Case 1 with the plastic pump. However, in th e plastic pump cases, bilateral renal infarction was suspected in 2 cases d uring necropsy whereas no abnormal findings were revealed in the titanium p ump cases. There were also no blood clots inside the PI 700 series. As for the 601, the explanted pumps demonstrated slight thrombus formations at the top and bottom pivots except in 1 case. The Gyro PI series, especially the PI 700 series, demonstrated superior performance, biocompatibility, antith rombogenicity and low hemolysis. Also, the durability of the actuator was d emonstrated. Based on these results, this titanium centrifugal pump is suit able as an implantable LVAS and RVAS. It is likely that the Gyro PI series is a feasible component of the BiVAS functional TAH.