The purpose of this study was to demonstrate the feasibility of the use of an implantable, high-energy, and compact battery system for an undulation pump total artificial heart (UPTAH). The implantable battery system tested consists of six lithium-ion batteries in series, a charge unit, and a charge/discharge control unit. A lithium-ion battery is currently the best energy-storage device because it has more energy density, a better life cycle, and a smaller temperature rise than those of other secondary batteries. The performance of the implantable battery system was evaluated in an in vitro experiment using an electric load that simulated the UPTAH. Also, sufficiently reliable operation of a system for supplying energy to a UPTAH consisting of a transcutaneous energy transmission system (TETS) and an implantable battery system was confirmed in three experiments using goats. The results of the in vitro and in vivo experiments showed that the implantable battery system supplied sufficient current to the UPTAH for maintenance of physiological conditions in the goat with maximum rise in temperature to less than 43 degrees C.
We have been developing a remote monitoring system for patients with implanted artificial hearts. The remote monitoring system consists of two digital data links: an electromagnetic transcutaneous digital-data transmission (TDT) system between an artificial heart controller inside the body and a mobile computer outside the body, and a public high-speed data transmission service using PHS (Personal Handy-Phone System) between the mobile computer and a host computer in a hospital. The TDT system mainly consists of an ASK (Amplitude Shift Keying) circuit with carrier electromagnetic wave frequencies of 4MHz and 10MHz and corresponding demodulation circuit, thin loop coil antennas for transmission and receiving, and a one-chip microcomputer for the alarm system for indicating misalignment of antennas outside the transmittable range to ensure error-free data transmission. In our remote monitoring system, motor current and motor rotational angle data from the implanted controller are framed together by a control code for data error checking and correcting at the receiving site, and the data are sent through the PHS connected to the mobile computer. GPS (Global Positioning System) positioning data are also sent to the host computer with control codes. The host computer calculates pump outflow and arterial pressure and displays the data in real-time waveforms. The host computer also displays the patient's position on the map and the condition of the batteries. The results of this study showed that the driving condition of the artificial heart and the subject's position could be remotely monitored on the host computer. It could be concluded that this monitoring system is useful for remote monitoring of patients with an implanted drtificial heart.
Computer assisted design for the implantable left ventricular assist device (LVAD) blood pump using computational fluid dynamics (CFD) and computer-aided design and manufacturing (CAD/CAM) Abstract Thrombus formation and hemolysis are critical issues in the design of a long-term implantable LVAS (left ventricular assist system). The fluid dynamic characteristics of the blood flow are one of the main factors that cause thrombus formation and hemolysis. In this study, we optimized blood chamber geometry, port design, and fluid dynamics in our implantable LVAS to ensure minimization of shear-stress-related blood damage. A blood pump chamber (stroke volume, 65 ml) and an inflow and outflow port were designed with three-dimensional CAD (computer-aideddesign) software (Pro-Engineering version 20) and estimated by FEM (fine-element method) computational fluid dynamic (CFD) analysis (Ansys version 5.5). We adopted three-dimensional distribution of CFD results for qualitative evaluation, and we also tried to estimate the normalized index of hemolysis (NIH) and time-series change of hematocrit from the results of CFD analysis as quantitative index of optimization for geometry of the blood pump chamber. With the use of this design, the blood pump geometry was optimized as the decrease of NIH from 2.72g/1001 in the first model to 0.098g/1001 in the second model, corresponding to the decrease in shear stress. The hematocrit also improved from 0.7% in the first model to 11.5% in the second model 2 years after implantation of the pump. Areas where flow stagnation was observed in the first model were free of stagnation in the second model. The results show that computer-aided design of the blood pump contributes to optimizing a blood pump chamber for reducing thrombus formation and hemolysis, and also contributes to reducing cost and time in developing the implantable LVAS.
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