NONINVASIVE ELECTROCARDIOGRAPHIC IMAGING - RECONSTRUCTION OF EPICARDIAL POTENTIALS, ELECTROGRAMS, AND ISOCHRONES AND LOCALIZATION OF SINGLEAND MULTIPLE ELECTROCARDIAC EVENTS

Background The goal of noninvasive electrocardiographic imaging (ECGI) is to determine electric activity of the heart by reconstructing maps of epicardial potentials, excitation times (isochrones), and electrog rams from data measured on the body surface. Methods and Results Local electrocardiac events were initiated by pacing a dog heart in a human torso-shaped tank. Body surface potential measurements (384 electrode s) were used to compute epicardial potentials noninvasively. The accur acy of reconstructed epicardial potentials was evaluated by direct com parison to measured ones (134 electrodes). Protocols included pacing f rom single sites and simultaneously from two sites with various inters ite distances. Body surface potentials showed a single minimum for bot h single- and double-site pacing (intersite distances of 52, 35, and 1 7 mm). Noninvasively reconstructed epicardial electrograms, potentials , and isochrones closely approximated the measured ones. Single pacing sites were reconstructed to within less than or equal to 10 mm of the ir measured positions. Dual sites were located accurately and resolved for the above intersite distances. Regions of sparse and crowded isoc hrones, indicating spatial nonuniformities of epicardial activation sp read, were also reconstructed. Conclusions The study demonstrates that ECGI can reconstruct epicardial potentials, electrograms, and isochro nes over the entire epicardial surface during the cardiac cycle. It ca n provide detailed information on local activation of the heart noninv asively. Its uses could include localization of cardiac electric event s (eg, ectopic foci), characterization of nonuniformities of conductio n, characterization of repolarization properties (eg, dispersion), and mapping of dynamically changing arrhythmias (eg, polymorphic VT) on a beat-by-beat basis.