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 μm, or which would only lead to small potential changes hidden within the signal noise