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This Article Full Text Full Text (PDF) All Versions of this Article: 295/4/H1626    most recent 00706.2008v1 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 Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Maleckar, M. M. Articles by Trayanova, N. A. Search for Related Content PubMed PubMed Citation Articles by Maleckar, M. M. Articles by Trayanova, N. A.

Polarity reversal lowers activation time during diastolic field stimulation of the rabbit ventricles: insights into mechanisms

¹Department of Biomedical Engineering and Institute for Computational Medicine, Johns Hopkins University, Baltimore, Maryland; and ²Department of Biomedical Engineering, ³Vanderbilt Institute for Integrative Biosystems Research and Education, ⁴Department of Physics and Astronomy, and ⁵Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee

Submitted 9 July 2008 ; accepted in final form 11 August 2008

To fully characterize the mechanisms of defibrillation, it is necessary to understand the response, within the three-dimensional (3D) volume of the ventricles, to shocks given in diastole. Studies that have examined diastolic responses conducted measurements on the epicardium or on a transmural surface of the left ventricular (LV) wall only. The goal of this study was to use optical imaging experiments and 3D bidomain simulations, including a model of optical mapping, to ascertain the shock-induced virtual electrode and activation patterns throughout the rabbit ventricles following diastolic shocks. We tested the hypothesis that the locations of shock-induced regions of hyperpolarization govern the different diastolic activation patterns for shocks of reversed polarity. In model and experiment, uniform-field monophasic shocks of reversed polarities (cathode over the right ventricle is RV–, reverse polarity is LV–) were applied to the ventricles in diastole. Experiments and simulations revealed that RV– shocks resulted in longer activation times compared with LV– shocks of the same strength. 3D simulations demonstrated that RV– shocks induced a greater volume of hyperpolarization at shock end compared with LV– shocks; most of these hyperpolarized regions were located in the LV. The results of this study indicate that ventricular geometry plays an important role in both the location and size of the shock-induced virtual anodes that determine activation delay during the shock and subsequently affect shock-induced propagation. If regions of hyperpolarization that develop during the shock are sufficiently large, activation delay may persist until shock end.

virtual electrodes; optical mapping; electric shocks; defibrillation