Optical micromapping reveals potential distributions on cardiomyocytes during field stimulation

Cells which are exposed to electrical fields show a spatial dependent distribution of the membrane potential: parts closer to the anode are hyperpolarized and parts closer to the cathode are depolarized. High resolution optical potential mapping allows, after a normalization procedure based on the common action potential amplitude, a detailed description of this distribution. Our first results, obtained from rod-shaped single ventricular cardiomyocytes showed, that the membrane potential distribution smoothly followed the applied homogenous electrical field. There was no hint for a cell shape dependent nonuniform potential distribution, which, if present, would be restricted to very small areas significantly below our spatial resolution of 15 /spl mu/m, or which would only lead to small potential changes hidden within the signal noise.