Abstract Background Precise identification of premature ventricular contractions (PVC) origins poses a significant challenge in electroanatomic mapping. Electrocardiographic Imaging (ECGI) allows instantaneous and global activation time mapping, providing a fast way to locate the origin of ectopic contractions. However, the standard methodology to estimate local activation times (LAT) in invasive electrograms is not directly transferable to ECGI signals. Objective In this study, a new methodology to calculate LAT maps with ECGI is presented and compared to the standard method in both, mathematical simulations and patients. Method We conducted computer simulations of five distinct PVCs to generate ECGI signals. Two techniques were applied to estimate LATs: the conventional -dV/dt method, which identifies the steepest negative deflection, and our novel Bayesian approach. The error in the location of the origin of the electrical activation and the similarity of the LAT maps were calculated with respect to the reference computer model. Additionally, we tested both algorithms in four patients with PVCs originated in different locations (three in the output tract of the right ventricle and one in the ventricular base, close the coronary sinus). Results The results indicated a substantial improvement in identifying the earliest activation site using our Bayesian algorithm, with a reduced localization error (1.5 ± 2.5 cm to 0.6 ± 1.5 cm). The root mean squared error (RMSE) was also significantly lower when comparing our Bayesian LAT maps to the reference LATs obtained in the simulations (19.0 ± 5.3 vs. 10.8 ± 4.5 ms). Patient data revealed smoother and more physiologically consistent propagations in the Bayesian maps, aligning with the PVC origins identified via electroanatomical navigation systems. Conclusion This study demonstrates that ECGI signals, when processed with advanced Bayesian techniques, significantly enhance LAT estimation. The proposed methodology improves the localization accuracy of ectopic beats and has practical implications for optimizing PVC treatment protocols.