DEVELOPMENT OF A TOTALL IMPLANTABLE, MOTOR DRIVEN ARTIFICIAL HEART SYSTEM

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In this project, in collaboration with Prof. H Reul's group of Helmholtz Institute of Biomedical Engineering, TechnicalUniversity Aachen, Aachen, Germany, the main objective was to develop a totally implantable, ultracompact electromechanical total artificial heart (TAH) and ventricular assist device (VAD). Both TAH and VAD Systems are based on transmitting the electrical energy through skin using a transcutaneous energy transmission (TET) system to power the implanted blood pump. The implanted components include thes pumping unit, compliance chamber, internal battery, and the controller. The TAH pumping unit is an one-piece design sandwiching an electromechanical actuator between the left and right pumps. The VAD was made using the same actuator as TAH's and covering the right side of the TAH with a backplate. The diameter and thickness of the TAH are 90mm and 70mm, respectively, and its volume is 400cc with the weight being 450g. Those of the VAD are 90mm and 56mm, respectively, yiel … More ding the volume of 275cc and weight of 460g. Although downsized, the maximum floy of 8L/min was obtained at the pumping rate of 160BPM. The power required for TAH ranged from 10 to 15 watts, while that of VAD from 5 to 8 watts. The maximum electrical to hydraulic efficiency of the TAH was 13.5% and that for VAD was 23%.As a volume compensator, 55cc air-filled chamber was designed for TAH, while for VAD 75cc chamber. The flexing membrane was made of polyurethane with its thickness being around 0.2mm. The secondary rechargeable batteries such as NiMH and Li-ion were tested for their performance with the TAH and VAD. With the terminal voltage of 16V, both batteries were able to power the artificial heart for over a duration of 2 hours.In vivo studies with VAD and TAH have just started to evaluate their durability and biocompatibility. When long term durability and biocompatibility were demonstrated, we will move into clinical trials.In addition to pulsatile systems, we also started to design and evaluate the centrifugal blood pump. The centrifugal blood pump is a tri-pod mechanism supporting the impeller. The basic performance in terms of head pressure-flow was obtained. The results indicated that the prototype pump meet the requirements as the left ventricular assist device. However, because of high friction wear at the tri-pod and polyethylene groove interface, we changed the pump design to a single pivot bearing mechanism. With improvement in impeller stability, this pump may meet requirements for clinical ventricular assist device. Further study will follow in future.As a monitoring system of the artificial heart implanted patient, an optical reflectance sensor to measure blood hemoglobin level and oxygen saturation was developed. Its accuracy in terms of hemoglobin level and oxygen saturation was evaluated using bovine blood. The results indicated feasibility of the sensor for continuous patient monitoring, provided its long term performance has been proven in animals.Through collaboration with Helmohotz Institute, we were fortunate to exchange not only the staff members, but also students. We received three master's students who worked on the optical sensor project. One of our students spent six months in Aachen learning computation fluid dynamic approach to analyze blood flow pattern inside the continuous flow devices. Also, we organized two Japan-Germany artificial heart symposiums, one in 1998 and the other in 2000. Through these exchange programs, we were fortunate to learn valuable information to help better design and analyze blood pump data. I think exchange program provided valuable experience to the students as well as staff members. Less