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Finite difference and lead field methods in designing implantable ECG monitor

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Abstract

To minimize time-consuming and expensive in vitro and in vivo testing, information regarding the effects of implantation and the implants on measurements should be available during the designing of active implantable devices measuring bioelectric signals such as electrocardiograms (ECG). Modeling offers a fairly inexpensive and effective means of studying and demonstrating the effects of implantation on ECG measurements prior to any in vivo tests, and can thus provide the designer with valuable information. Finite difference model (FDM) and lead field approaches offer straightforward and effective modeling methods supporting the designing of active implantable ECG devices. The present study demonstrates such methods in developing and studying ECG implants. They were applied in demonstrating the effects of implant dimensions and of electrode implantation on the measurement sensitivity of the ECG device. The results of the simulations indicated that the interelectrode distance is the factor of the implant design determining the lead sensitivity. Other parameters related implant dimensions and shape have minor effect on the morphology of the ECG or on the average sensitivity of the measurement. This is shown for example when the interelectrode distance was reduced to 1/3 of original the average lead sensitivity decreased by 69.1% while larger relative changes in other dimensions produced clearly smaller changes. It was also observed here that implanting the electrodes deeper under the skin has major effects on the local sensitivities in heart muscle and thus affect to the morphology of the ECG. The study indicated also that non-conducting medium (i.e. implant insulated body) between the electrodes increases the sensitivity on heart muscle compared to cases where only electrodes are implanted.

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Acknowledgements

We would like to thank PhD Noriyuki Takano for providing the finite different method software. We would also like to thank MSc Tuukka Arola for providing the visualization tools. This work has been part of WIRELESS-project (5205437) funded by the Academy of Finland. The work has been supported also by the grants from the Finnish Cultural Foundation and the Ragnar Granit Foundation.

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Authors and Affiliations

  1. Ragnar Granit Institute, Tampere University of Technology, P.O. Box 692, 33101, Tampere, Finland

    Juho Väisänen, Jari Hyttinen & Jaakko Malmivuo

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  1. Juho Väisänen
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  2. Jari Hyttinen
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  3. Jaakko Malmivuo
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Correspondence to Juho Väisänen.

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Väisänen, J., Hyttinen, J. & Malmivuo, J. Finite difference and lead field methods in designing implantable ECG monitor. Med Bio Eng Comput 44, 857–864 (2006). https://doi.org/10.1007/s11517-006-0092-7

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  • DOI: https://doi.org/10.1007/s11517-006-0092-7

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