Pranav Bhagirath

177 A priori model independent inverse potential mapping: the impact of electrode positioning 62 electrodes surrounding the thorax The 62 electrodes surrounding the thorax did not provide clinical sufficient information (video 5). Only ventricular epicardial activation could be reconstructed using this configuration. Regions with no or low signal variance were observed as gaps in the reconstructed epicardial potentials. 62 electrodes concentrated (30mm inter-electrode distance) Concentrated positioning of the 62 available electrodes, directly above the heart, improved the overall resolution (video 6). Although reduced in size and number, areas of low signal were still present when using this electrode configuration. 62 electrodes super-concentrated (20mm inter-electrode distance) Higher concentration of the electrode configuration (20 mm inter-electrode distance) resulted in a substantial increase of image resolution (video 7). Atrial and ventricular activation could be clearly distinguished and spatially localised in the reconstructed epicardial activation sequence. Figure 6 shows epicardial potential maps for six instants of time during the QRST interval. In all three volunteers, similar results were obtained. Reconstruction of pacing sites None of the patients reported any complaints during or after the MRI examination. Pacing thresholds and leads impedances remained unaffected by the MRI scan in all patients. For all patients, the site of earliest ventricular depolarisation could be identified. In two patients, depolarisation started in the superior part of the right ventricular septum. In remaining patients, the site of earliest depolarisation was located in the apical region of the right ventricle. In vivo evaluation of localisation error and amount of detail A mean localisation error of 5.3 mm was found. The mean size of the smallest visible detail during pacing, determined by a threshold test, was 7 mm. Individual values are listed in table 2 .