ECG Imaging (ECGI) is the process of calculating electrical cardiac activity from body surface recordings from geometry and conductivity of the torso volume. Therefore, the accuracy of ECGI may be sensitive to the geometric representation of the thorax. Cardiac surface segmentation key, yet possibly variable, part of most ECGI pipelines. We hypothesis that variation in cardiac segmentation will produce error in the computed ventricular surface potentials from ECGI. In this study, an international consortium performed multiple segmentations of the same patient to analyze the effect on the results of ECGI.
We compared ECGI results from the same body surface potentials and multiple ventricular segmentations. Through a collaborative effort within the Consortium for ECG Imaging (CEI), a patient CT scan was segmented by five research groups, from which we created ventricle and torso surface meshes. We computed epicardial and endocardial surface potentials from measured body surface potentials with Tikhonov regularization and calculated the variance of the potential at each point of the ventricular surface.
We found that using the different segmentations produced variability in the computed ventricular surface potentials. The peak computed variance was up to 50 mV^2. In general, the anterior surface showed greater variance in the computed potential than the posterior surface, and the epicardium showed greater variance than the endocardium. Not surprisingly, locations of greater variance in the computed potential correlated to locations of greater variance in the segmentations, for example near the pulmonary artery and the basal-anterior left ventricular wall.
Our result indicate that ECGI may be more sensitive to segmentation errors on the anterior epicardial surface than other areas of the heart. A hypothetical rationale for this finding is that in the anterior region, the heart and body surface are closest together so that even small distance perturbations would alter computed cardiac potentials.