Data analysis techniques for measuring spatial inhomogeneity in repolarization using optical transmembrane potentials

Experimental characterization of the spatial distribution of action potential duration and repolarization times is presented. The signal processing and analysis techniques used in this characterization are described. The data used to test the dispersion of refractoriness hypothesis must meet three requirements: (1) they must be recorded simultaneously at many sites on the heart; (2) spatial resolution must be high; and (3) the data must allow a measurement of both the time of activation and repolarization at each site. The epicardial recordings used were made with an optical technique which provides a signal of the average transmembrane potential of cells in a small volume of cardiac tissue. The optical signals met all three of the above requirements: (1) data were collected from guinea pig hearts from 124 sites in a 1-cm×1-cm region of the anterior left ventricle; (2) each channel recorded activity of cells in a 0.72-mm² area; and (3) the action potential signals can be readily analyzed for depolarization and repolarization times