Pranav Bhagirath

173 A priori model independent inverse potential mapping: the impact of electrode positioning Patients with an implanted pacemaker system Localisation error An investigator blinded to the actual ventricular lead tip position, identified the site of earliest depolarisation on the colour-coded epicardial potential map. Subsequently, the distance between this site and the position of the ventricular lead tip on the MRI images was determined. Hence, the localisation error was quantified as the distance between the true pacing location and the pacing location projected from the inverse. Amount of true detail The amount of detail was evaluated by performing a threshold-test on the epicardial potential peak induced by a pacing stimulus at a well-known electrode location. When the threshold was set too high, the potential peak would split, suggesting false detail. The minimum size of the inversely mapped potential peak induced by pacing is determined by the highest threshold value that does not cause the peak to split. The detail shown in this case is true, rather than false ( figure 4 ). The smallest visible detail was quantified as the maximum point spread cross-section in mm of the potential peak due to pacing. Computing platform All analyses were performed on a 2.4 GHz quadcore laptop running the Windows 8 OS. Solving the potential equations was delegated to an Ubuntu 12.10 virtual machine running on this laptop. Correlation coefficients were determined using Pearson’s product moment correlation coefficients as computed by the NumPy library.