Aims: This study aimed to assess the effect the presence of f-waves may have on the 𝒱-index, an ECG-based estimator of the standard deviation of ventricular myocytes’ repolarization times (𝑠𝜗), as a preliminary process for the study of Atrial Fibrillation (AF). Methods: 12 lead ECGs were generated using synthetic T-waves and real QRS templates extracted from clinical data. The T-waves were simulated using a re-implementation of the forward ECG model creating seven 300 T-waves bundles with increasing values of 𝑠𝜗. The 𝒱-index (t𝒱-index) was preliminarily compared to the values of 𝑠𝜗 to assess the valid-ity of the index as a measure of repolarization times. Then, the t𝒱-index was compared to the 𝒱-index calculated after 50 sets of real f-waves randomly extracted from AF patients were added to the ECGs (f𝒱-index) and after the f-waves were removed (c𝒱-index). Student’s t-test was used to ensure firstly, a significant difference (p-value ≤ 0.05) between the f𝒱-index and the c𝒱-index as well as between the f𝒱-index and the t𝒱-index and secondly, a non-significant difference (p-value > 0.05) between the c𝒱-index and the t𝒱-index. Results: A strong correlation (r = 0.99, p-value < 0.001) was shown when comparing the t𝒱-index and 𝑠𝜗, validating the 𝒱-index computation method. Regarding the comparison between the f𝒱-index, the c𝒱-index and the t𝒱-index: the f𝒱-index had highly significant differences (, p-value < 0.001) with the c𝒱-index and significant differences (, p-value < 0.05) with values of the 𝒱-index below 53.3 ms, while the c𝒱-index and the t𝒱-index had non-significant differences for the whole range of values studied. Conclusion: During AF the T-waves get corrupted by f-waves, typical of AF, making it meaningful to implement the cancellation of f-waves when applying the 𝒱-index to ECG during AF.