Background: Activation (AT) and repolarization times (RT) can be identified by morphological features in unipolar electrograms (UE). However, in the case of CARTO catheter-recorded UE, such clinical signals often exhibit distortions during the T-wave (TW) leading to erroneous RT, which make the signal unreliable. Objective: Our aim is to improve the interpretation of CARTO patient electrograms, and to identify artifact, via accurate reconstructions of the UE from AT and RT. Methods: From 7677 CARTO UE from 18 patients with structurally normal hearts, AT was approximated as the most negative slope during the QRS, and RT as the most positive slope during the TW (Wyatt method WM). Each UE was modeled by fitting an action potential (AP) template given AT and RT, and subtracting it from the mean of all APs for the patient. Pearson’s correlation coefficient (CC) was calculated between each recorded UE (rUE) and modeled UE (mUE). When a 2nd deflection was present during the T-wave, mUEs were also calculated with that RT. Artifact was defined as the difference between the rUE and best mUE. Results: The median CC between all rUE and mUE was 0.641 with quartiles Q1=0.479 & Q3=0.759 over the whole signal, 0.887 with Q1=0.74 & Q3=0.95 during the QRS, and 0.728 with Q1=0.422 & Q3=0.873 during the TW. 63% of the signals exhibited a second TW deflection; in 33% of these, the RT associated with the 2nd deflection provided a higher T-wave CC than WM. Conclusion: The model is able to produce many well correlated signals, which suggests that, despite artifacts, the associated AT and RT were accurate. Artifacts impede the performance of WM. However, by considering several maxima, RT can be found more reliably.