Spatial Accuracy of a Clinically Established Noninvasive Electrocardiographic Imaging System for the Detection of Focal Activation in an Intact Porcine Model

Background: Noninvasive electrocardiographic imaging (ECGi) is used clinically to map arrhythmias before ablation. Despite its clinical use, validation data regarding the accuracy of the system for the identification of arrhythmia foci is limited. Methods: Nine pigs underwent closed-chest placement of endocardial fiducial markers, computed tomography, and pacing in all cardiac chambers with ECGi acquisition. Pacing location was reconstructed from biplane fluoroscopy and registered to the computed tomography using the fiducials. A blinded investigator predicted the pacing location from the ECGi data, and the distance to the true pacing catheter tip location was calculated. Results: A total of 109 endocardial and 9 epicardial locations were paced in 9 pigs. ECGi predicted the correct chamber of origin in 85% of atrial and 92% of ventricular sites. Lateral locations were predicted in the correct chamber more often than septal locations (97% versus 79%, P =0.01). Absolute distances in space between the true and predicted pacing locations were 20.7 (13.8–25.6) mm (median and first–third quartile). Distances were not significantly different across cardiac chambers. Conclusions: The ECGi system is able to correctly identify the chamber of origin for focal activation in the vast majority of cases. Determination of the true site of origin is possible with sufficient accuracy with consideration of these error estimates.