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LocaLisa: Electrical Localization of Endocardial Electrodes. Fred H. Wittkampf, Richard Derksen, Erik F. Wever, Arthur A Wilde. University Hospital, Utrecht, The Netherlands Citation: Pace Vol 20: Abstr. Suppl. April 1997, Page 1075 Abstract 104 Background: Estimation of the three dimensional (3D) position of an ablation electrode from biplane fluoroscopic images is inadequate if a systematic lesion pattern is required for complex arrhythmogenic substrates. We studied the accuracy of a new electrode localization technique (LocaLisa). Using an orthogonal lead system, a small high frequency current is delivered through the thorax, using slightly different frequencies around 30 KHz for the three orthogonal directions. The resulting high frequency signal, recorded from an endocardial electrode, is selectively filtered for the three frequencies to obtain a unique measure of the position of that electrode within the thorax. This method was applied using 2 to 3 different positions of a decapolar catheter in the right or left ventricle of 12 patients (7RV, 5LV). To determine the accuracy within one ventricle, LocaLisa data obtained from 2 to 3 catheter (20-30 electrode) positions per ventricle were analysed using calibrated biplane fluoroscopy as the golden standard. For a particular cardiac segment, data from the 10 electrodes were compared with the true inter-electrode distances for each catheter position. Results: The high frequency currents did not cause any noise on the unipolar or bipolar electrograms. The mean spatial error of the calculated electrode positions within one ventricle was 7mm for both ventricles partly due to inaccuracies of biplane fluoroscopy. When, however, data obtained from 10 catheter electrodes were compared with the true inter-electrode distances, the relationship between known and calculated inter-electrode distances was extremely linear with a mean correlation coefficient of 0.995 (RV) and 0.998 (LV). This compares to a mean standard deviation of 1.6 and 1mm respectively in a area of 5-6cm in cross section. Conclusion: The LocaLisa method is sufficiently accurate for non-fluoroscopic mapping and ablation in a single chamber or segment thereof. It does not affect electrogram recording, and can be applied to any electrode catheter. LocaLisa Abstract 2 1