Noninvasive Imaging of the Origin of Premature Ventricular Activity

The localization and imaging of the origin of premature ventricular complex (PVC) before the electrophysiological study (EPS) can significantly shorten the time needed for the ablation procedure. In this paper, a method allowing noninvasive localization of the PVC origin by solving the inverse problem of electrocardiography and finding a dipolar source best representing the initial ectopic activity is presented. It requires measurement of body surface potential (BSP) maps and a model of the patient torso obtained from CT. To test the method, 96 ECG leads were measured in 5 patients and 128 leads in another 2 patients. BSP maps from the initial interval of several PVCs were used to solve the inverse problem using inhomogeneous (IT) or simplified homogeneous (HT) patient specific torso model. All measured ECG leads, as well as only selected 64, 48 or 32 leads of the 96 lead set were used for the inverse computations. The inversely obtained dipole locations were compared with the catheter positions during successful ablation within the EPS. In five patients the PVC origin was found in the right ventricular outflow tract (RVOT), in the remaining two patients it was in the left ventricle (LV). The noninvasive method localized the PVC origins in correct heart segments in all but one patient with localization errors of up to about 2 cm. In one patient the true origin in RVOT was localized in LV but still within 2 cm from the true position. The employment of the more detailed IT torso model did not bring significant improvement of the localization but the dispersion of solutions from different PVCs increased. The use of subsets of 48 or less ECG leads resulted in increased number of incorrect localizations. If the IT torso model was employed, there were a few incorrect localizations also when 64 ECG leads were used.