Sensor spacing affects the tissue impedance spectra of rabbit ventricular epicardium.

Published

Journal Article

This study was designed to test the hypothesis that a complex composite impedance spectra develops when stimulation and recording of cardiac muscle with sufficiently fine spatial resolution in a four-electrode configuration is used. With traditional (millimeter scale) separations, the ratio between the recorded interstitial central potential difference and total supplied interstitial current is constant at all frequencies. This occurs because the fraction of supplied current that redistributes to the intracellular compartment depends on effective membrane resistance between electrodes, which is low, to a much greater extent than effective membrane capacitance. The spectra should therefore change with finer separations at which effective membrane resistance increases, as supplied current will remain primarily interstitial at lower frequencies and redistribute between compartments at higher frequencies. To test this hypothesis, we built arrays with sensors separated (d) by 804 μm, 452 μm, and 252 μm; positioned those arrays across myocyte axes on rabbit ventricular epicardium; and resolved spectra in terms of resistivity (ρt) and reactivity (χt) over the 10 Hz to 4,000 Hz range. With all separations, we measured comparable spectra with predictions from passive membrane simulations that used a three-dimensional structural framework in which intracellular, interstitial, and membrane properties were prescribed based on the limited data available from the literature. At the finest separation, we found mean ρt at 100 Hz and 4,000 Hz that lowered from 395 Ω-cm to 236 Ω-cm, respectively, with maximal mean χt of 160 Ω-cm. This experimental confirmation of spectra development in whole heart experiments is important because such development is central to achieve measurements of intracellular and interstitial passive electrical properties in cardiac electrophysiological experiments using only interstitial access.

Full Text

Duke Authors

Cited Authors

  • Waits, CMK; Barr, RC; Pollard, AE

Published Date

  • June 2014

Published In

Volume / Issue

  • 306 / 12

Start / End Page

  • H1660 - H1668

PubMed ID

  • 24778170

Pubmed Central ID

  • 24778170

Electronic International Standard Serial Number (EISSN)

  • 1522-1539

International Standard Serial Number (ISSN)

  • 0363-6135

Digital Object Identifier (DOI)

  • 10.1152/ajpheart.00661.2013

Language

  • eng