Quantification of spatial repolarization heterogeneity: Testing the robustness of a new technique

The V-index is a recently-proposed metric related to repolarization heterogeneity (RH) across the myocardium, a key quantity for the development of arrhythmias. The metric is derived from multi-leads ECG recordings and this paper investigates two of its properties: i) the dependency on the lead system (Frank´s orthogonal vs. 12 standard leads); ii) the influence of errors in the location of the T-end position. The first investigation was performed by simulations, using a forward ECG model (ECGSIM). In the lead system of interest, the V-index was computed varying the standard deviation of RH (s_v). The results showed that the average bias in the estimate of RH (at σ_φ = 1 ms) ranged from -20.4±4.0% (s_v = 20.6 ms) to -26.3±4.0% (s_v = 70.9 ms) for the standard system and from -7.0 ± 4.2% to - 19.0 ± 4.2% for the Frank´s one. While the bias diminished, the vulnerability to noise slightly increased. Secondarily, 68 ECGs from the E-OTH-12-0068-010 THEW database were analyzed. To simulate mislocation, the T-end point was consistently moved (±20 ms) around its correct position and the V-index computed. The average differences in the V-index estimates across the population were always smaller than 1%. This is a desirable property, given the discrepancies across methods in locating T-end positions.