In vivo performance evaluation of a transcutaneous energy and information transmission system for the total artificial heart

Mok Ahn Jae Mok Ahn, Woo Kang Dong Woo Kang, Chan Kim Hee Chan Kim, Goo Min Byoung Goo Min

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Abstract

As part of an electromechanical total artificial heart (TAH) program, an integrated transcutaneous energy and information transmission (TEIT) system has been developed. In vivo performance of the developed system was evaluated through a simplified animal model without implant of a TAH. The design features include the small size of the implanted part, and dual coil structure of the external part. In the transcutaneous energy transmission (TET) system based on magnetic induction, the external primary and implanted secondary coils have the shape of a truncated cone, 7.0 and 3.8 cm in diameter, and 23 and 12 turns of Litz wire, respectively. The external coil is driven by a 350 to 410 kHz tuned class E amplifier that has a minimum switching loss of power transistor. In vitro test results using 1 cm thick dog's skin showed a flat total efficiency (DC to DC) of 75% for 20 to 30 W of delivered mean power. In order to achieve bidirectional communication between implanted and external components, a small circuit board containing four light emitting diodes and a photodiode was incorporated in each TET coil facing each other across the skin. Unmodulated optical pulse transmitted digital data (9600 baud, RS-232 protocol) in error free condition through an up to 15 mm thick dog's skin patch accommodated 18° of misalignment. Three subacute in vivo studies were conducted in dogs to evaluate performance of the developed system. The secondary set was implanted in the mid flank region of the dog, and the output was percutaneously connected to the control system to drive the external TAH on the mock circulatory system. No significant difference between in vivo and in vitro performance was found. The temperature rise around the implanted coil was kept below 2° C, and accordingly no tissue injury was observed. The developed system showed good in vivo performance and should be successfully used with an implanted TAH system. The simplified animal model provided an easy method for in vivo performance evaluation of the TEIT system.

Original languageEnglish
JournalASAIO Journal
Volume39
Issue number3
DOIs
StatePublished - 29 Oct 1993

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