Key result
Multisite interstitial stimulation in two-dimensional models allowed microimpedance measurements within 25% of prescribed values in isotropic and anisotropic models.
Why the study?
Can multisite interstitial stimulation be used to accurately measure cardiac microimpedances in multidimensional preparations?
Can multisite interstitial stimulation be used to accurately measure cardiac microimpedances in multidimensional preparations?
Multisite interstitial stimulation can accurately measure cardiac microimpedances in 2D models, suggesting potential for future microfabricated devices in electrophysiological studies.
Supports feasibility in 2D models; leaves open validation in multidimensional cardiac preparations.
We analyzed central interstitial potential differences during multisite stimulation to assess the feasibility of using those recordings to measure cardiac microimpedances in multidimensional preparations. Because interstitial current injected and removed using electrodes with different proximities allows modulation of the portion of current crossing the membrane, we hypothesized that multisite interstitial stimulation would give rise to central interstitial potential differences that depend on intracellular and interstitial microimpedances, allowing measurement of those microimpedances. Simulations of multisite stimulation with fine and wide spacing in two-dimensional models that included dynamic membrane equations for guinea pig ventricular myocytes were performed to generate test data ( partial differentialphio). Isotropic interstitial and intracellular microimpedances were prescribed for one set of simulations, and anisotropic microimpedances with unequal ratios (intracellular to interstitial) along and across fibers were prescribed for another set of simulations. Microimpedance measurements were then obtained by making statistical comparisons between partial differentialphio values and interstitial potential differences from passive bidomain simulations (Deltaphio) in which a wide range of possible microimpedances were considered. Possible microimpedances were selected at 25% increments. After demonstrating the effectiveness of the overall method with microimpedance measurements using one-dimensional test data, we showed microimpedance measurements within 25% of prescribed values in isotropic and anisotropic models. Our findings suggest that development of microfabricated devices to implement the procedure would facilitate routine measurement as a component of cardiac electrophysiological study.
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Pollard et al. (2005) studied this question. Multisite interstitial stimulation was evaluated on Measurement of cardiac microimpedances. Multisite interstitial stimulation in two-dimensional models allowed microimpedance measurements within 25% of prescribed values in isotropic and anisotropic models.