Conversion from left ventricular cylinder coordinates to radiographic projections during ECG-guided catheter ablation of cardiac arrhythmias

Electrocardiographic Body Surface Mapping can assist in procedures for catheter ablation of cardiac arrhythmias, by providing an estimate of the site of origin of an arrhythmia. The authors´ localization methods provide their results in left ventricular cylinder coordinates (LVCC). It would be preferable if localization results were presented in the radiographic views, possibly superimposed on the X-ray images. This requires computation of a position on the endocardial surface of the left ventricular wall from LVCC. Perfect translation between a position on the endocardial wall and cylinder coordinates would be possible if the geometry of the wall were perfectly known. Unfortunately, little is known about the wall geometry in practice. Therefore, the authors investigated how well one can reconstruct 3D positions from LVCC with limited means, by computing LVCC from biplane radiographic images, and reconstructing the positions from the LVCC. The authors´ model of the wall consisted of a half-ellipsoid, scaled to the individual ventricular length and diameter. The method was evaluated using 111 catheter positions obtained in 8 patients. The reconstruction error in 3D space was 9±8% of the ventricular length. The method is therefore accurate enough to be useful during a catheter ablation procedure