Preliminary study of a new type of energy transmission system for artificial hearts.

A transcutaneous energy transmission (TET) system is the most common way to power artificial hearts and ventricular assist devices. However, an external battery used with a TET system poses several problems, such as its heavy mass, small charge capacity, and long recharging time. The battery is indispensable when patients want to be ambulatory. This article proposes a new type of TET system that does not require an external battery because electrical energy is supplied remotely by using electromagnetic waves. For this system to operate, multiple transmitting antennas have to be mounted in a room or facility that has been shielded from electromagnetic waves, and a receiving antenna is attached to the patient. Electromagnetic waves transmit electrical power from the transmitting antennas to the receiving antenna. The received electrical power is sent to an implanted device through the TET system. The total power efficiency was plotted against the transmitter-receiver distance by measuring the power that was input to the transmitting antennas, and the final direct current (DC) power that was received by the receiving antenna. A 430-MHz frequency was applied in the experiments. The obtained efficiency was around 10% within a transmitter-receiver distance of 1 m when Yagi-Uda antennas were used for the transmitting antennas and two other types of antenna were used for the receiving antennas: a folded dipole with a reflector and a single loop with a reflector. The results suggested that the proposed system is worth considering. The proposed system would go a long way toward enhancing the patient's quality of life compared with the currently used conventional TET system.

Functions for detecting malposition of transcutaneous energy transmission coils.

A transcutaneous energy transmission system (TETS) for artificial hearts and ventricular assist devices uses electrical coupling of power between external and implanted coils. If the position of coils changes relative to each other, the TETS cannot feed the required power of the implanted device. During activity or sleep, the coils may move accidentally. TETS users and the people around them have to pay attention to this because the range of the position where the required power can be fed efficiently is not wide. Therefore, we added functions for the position changes of the coils to the TETS. Regular, cautious, and irregular positions were introduced, and the ranges of them were decided upon in our experiments. The cautious position was determined by the area where the change of the relative position of the coils was relatively small. When the coils were in the cautious position, the circuit was tuned by way of changing the resonant point. This modulation could give good power efficiency in the cautious position. When the coils were in the irregular position, an alarm switch was turned on. These functions ease the restriction of the coil position and give better quality of life (QOL) than do the conventional TETS.