NONCONTACT ENDOCARDIAL MAPPING - RECONSTRUCTION OF ELECTROGRAMS AND ISOCHRONES FROM INTRACAVITARY PROBE POTENTIALS

Introduction: Mapping endocardial activation and repolarization proces ses is critical to the study of arrhythmias and selection of therapeut ic procedures, Previously, we developed methodology for reconstructing endocardial potentials from potentials measured with a noncontact, in tracavitary probe, This study further develops and evaluates the abili ty of the approach to provide detailed information on the spatiotempor al characteristics of the activation process, Specifically, we reconst ructed endocardial electrograms and isochrones throughout the activati on process over the entire endocardium during a single beat. Methods a nd Results: Cavity potentials were measured with a 65-electrode probe placed inside an isolated canine left ventricle, Endocardial potential s were measured simultaneously using 52 electrodes, Potentials were ac quired during subendocardial pacing from different locations, Computed electrograms at various sites closely resemble the measured electrogr ams (correlation coefficient > 0.9 at 60% of the electrodes), Computed isochrones locate subendocardial pacing sites with 10-mm accuracy, Tw o pacing sites, 17 mm apart, were resolved, Critical regions, such as areas of isochrone crowding, were accurately reconstructed. Conclusion s: Results indicate the applicability of the approach to mapping the c ardiac excitation process on a beat-by-beat basis without occluding th e ventricle, The ability of locating electrical events (e.g., single o r multiple initiation sites) is demonstrated, Importantly, the method is shown to be capable of reconstructing electrograms over the entire endocardium and determining nonuniformities of activation spread (e.g. , areas of slow conduction), These capabilities are important to clini cal application in the electrophysiology laboratory and experimental s tudies of arrhythmias in the intact animal.