Validation of the V-index through finite element 2D simulations

A physiological spatial heterogeneity of ventricular repolarization (SHVR) is responsible for the T-wave on the ECG. However, an increased SHVR might favor the development of ventricular arrhythmias. The V-index is a metric introduced with the aim of assessing SHVR from ECG. In this work, the V-index was validated by means of 2D computer simulations, using a modified version of the ten Tusscher-Panfilov (TP06) model that accounts for repolarization variability. Synthetic ECG were simulated at 12 different positions at the external surface with two different strategies. Also, a theoretical extension of the V-index definition was derived, to address situations where fluctuations in repolarization times are correlated across nodes. At tissue level, theoretical values of V-index were in agreement with SHVR with a constant pacing (maximum error: 3.4 ms). However, with a variable RR, a selection of stationary beats was necessary to overcome the stronger temporal correlation across nodes (maximum error: 3.2 ms). On the other hand, values of V-index numerically estimated from the ECG were always in agreement with their theoretical values (average error in the estimates: 15 perpendicular to 9%). The results confirmed that the V-index indeed provides an approximate and reliable measure of SHVR.