Development of a totally implantable ventricular assist device system with improved antithrombogenicity and portability

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We have been developing an ultra-compact and low-noise portable pneumatic VAD driver in order to improve patient s quality of life in terms of providing better mobility and lower noise environment. The driver utilizes an electtohydraulic actuator instead of an air compressor. Oil pressure through a hydraulic/neumatic converting chamber, generate air pressures which drive a pneumatic blood pump. These technologies realized an ultra-compact size (35 x 30 x 45 cm), a light weigh (13 kg) and low-noise (39 dB). Furthermore, the driver is carried in safety using soft wheels axis against a bumpy ground and is protected by the urethane body surface against fall-down. This driver can be actuated with only one-tenth power consumption (45 w) in comparison with conventional console type driver and can be run for 2 hours with two internal rechargeable nickel metal-hydride batteries. This driver provide fill to empty driving mode, and pump output is continuing estimated for alarm. The durability has … More been confirmed in a bench test of over 15,000 hours. In vitro testing with Toyobo pneumatic VAD demonstrated a sufficient pump performance of up to 7 L/min. In vivo evaluation for over 3 months was also carried out in a left ventricular assist model using 6 adult goats without any failure. We conclude that this driver provide better quality of life to the patients with long-term pneumatic VAD support.Electrohydraulic ventricrlar assist device(EHVAD) systems have been developed. The EHVAD system is developed by using the left blood pump and electrohydraulic actuator of EHTAH, which was packaged with a volume compensation chamber. The system weight was 1160g. The maximum flow rate was 8.8 L/min and the maximum efficiency was 14.2 %.The system was implanted in 3 calves as small as 61 kg. One of these lived for 90 days. The estimated cardiac output was 4 L/min. These results indicate that EHVAD system has the potential to be a totally implantable system.A Transcutaneous energy transfersystem(TETS), a transcutaneous optical telemetry system(TOTS), and an internal battery have been developed. The system performance was evaluated in animal experiments using Electrohydraulic total artificial heart(EHTAH) system. The system was driven by the TET during normal operation of approximately 21 W input power. The system was also driven by the internal battery everyday, as per prescribed protocol. In the case of 40 minutes of discharge, the internal battery was fully charged for 3 hours. The DC to DC transmission efficiency of the TET was maintained at nearly 85 %. Driving parameters were transmitted through the skin with the TOTS at 9600 bps.We have developed a new monitoring method of the pump diaphragm positions for optimal driving of an electrohydraulic artificial heart system. The pump unit comprises polyurethane-made diaphragm-type blood pumps and an energy converter that reciprocates and delivers hydraulic silicone oil to the alternate blood pumps. Two ultrasound crystals of 2.4 mm diameter are fixed to both sides of the pump housing on a maximum stroke axis with 50 mm length. The ultrasound propagates through the blood chamber, the diaphragm, and the oil chamber. Propagation time of the ultrasound varies according to the diaphragm position because propagation speed of blood 1540 m/s is different from that of silicone oil 908 m/s. The propagation time varied in proportion to the diaphragm position estimated from observation and driving oil pressure wave forms in an overflow type mock circulation test. The propagation time reached to the maximum value of 0.054 ms and the minimum value of 0.033 ms at full-eject and full-fill states, respectively. Linear correlation was observed between the cardiac output and product of the change of propagation time multiplied by heart rate in the range of 1 to 9 L/min. The correlation coefficient was r=0.97. These results indicate that the diaphragm position is detected by the propagation time and the cardiac output is computed by the change of propagation time without a flowmeter.We also have developed computer simulation system for anatomical fitting study of the implantable artificial organ. A three-dimensional image of the chest cavity was reconstructed from human CT scan images. After removing the ventricles, the pump unit was implanted and connected to atriums and blood vessels on the computer model to decide a suitable design and fitting.Pocket infection is a serious major problem for the patients with an implantable VAD or TAH system. For reducing the risk of this type of infection, it is a reasonable approach to coat the device outer surface with tissue-compatible soft material that can alleviate mechanical vibration of the device and stress between the rigid device and the surrounding tissue. We developed a novel porous device-coating material that imparts excellent tissue-compatibility. This material, consisting of segmented polyurethane with a 3D reticulated structure, has tissue-like flexibility and sufficient mechanical strength. The test materials were potted in a silicone tube, and implanted into subcutaneous tissue of an adult goat. After 1 year implantation, no inflammatory or necrotic foci were observed in the infiltrated tissue, thus demonstrating sufficient tissue ingrowth into the material to form tight interconnections. In conclusion, the newly developed material may be a suitable outer surface coating material for implantable artificial heart. Less