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This Article Full Text Full Text (PDF) All Versions of this Article: 289/3/H1137    most recent 00064.2005v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Knisley, S. B. Articles by Pollard, A. E. Search for Related Content PubMed PubMed Citation Articles by Knisley, S. B. Articles by Pollard, A. E.

Use of translucent indium tin oxide to measure stimulatory effects of a passive conductor during field stimulation of rabbit hearts

¹Department of Biomedical Engineering, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill; ²College of Engineering, North Carolina State University, Raleigh, North Carolina; and ³Cardiac Rhythm Management Laboratory, Department of Biomedical Engineering, School of Engineering, University of Alabama at Birmingham, Birmingham, Alabama

Submitted 24 January 2005 ; accepted in final form 8 May 2005

Biomathematical models and experiments have indicated that passive extracellular conductors influence field stimulation. Because metallic conductors prevent optical mapping under the conductor, we have evaluated a passive translucent indium tin oxide (ITO) thin-film conductor to allow mapping of transmembrane potential (V_m) and stimulatory current under the conductor. A 1-cm ITO disk was patterned photolithographically and positioned between 0.3-cm² mesh shock electrodes on the ventricular epicardium of isolated perfused rabbit hearts stained with 4-{2-[6-(dibutylamino)-2-naphthylenal]ethenyl}-1-(3-sulfopropyl)-, hydroxide, inner salt (di-4-ANEPPS). For a 1-A, 10-ms shock during the action potential plateau, optical maps from fluorescence collected using emission ratiometry (excitation at 488 nm and emissions at 510–570 and >590 nm) indicated that the disk altered V_m by as much as the height of an action potential. V_m became more positive near the edge of the disk, where the ITO conductance gradient was parallel to applied current, and more negative near the opposite edge, where the gradient was not parallel to current. For diastolic shocks, the disk expedited membrane excitation at the sites of positive V_m in the heart and in a cardiac model with realistic ITO disk surface and interfacial conductances. Optical maps of ITO transmittance and the model indicated that the disk introduced anodal and cathodal stimulatory current at opposite edges of the disk. Thus ITO allows study of the stimulatory effects of a passive conductor in an electric field.

ratiometric optical mapping; transmembrane potential; transmittance

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