title: An estimate of the dispersion of repolarization times based on a biophysical model of the ECG.
abstract: Temporal heterogeneity of ventricular repolarization is a key quantity for the development of ventricular reentrant arrhythmia. In this paper, we introduce the V-index, a novel ECG-based estimator of the standard deviation of ventricular myocytes' repolarization times s(ϑ). Differently from other ECG metrics of repolarization heterogeneity, the V-index was derived from the analysis of a biophysical model of the ECG, where repolarization is described by the dominant T-wave (DTW) paradigm. The model explains the shape of T-waves in each lead as a projection of a main waveform (the DTW) and its derivatives weighted by scalars, the lead factors. A mathematical formula is derived to link the heterogeneity of ventricular repolarization s(ϑ) and the V-index. The formula was verified using synthetic 12-lead ECGs generated with a direct electrophysiological model for increasing values of s(ϑ) (in the range 20-70 ms). A linear relationship between the V-index and s(ϑ) was observed, V ≈ 0.675 s(ϑ) + 1.8 ms (R(2) = 0.9992). Finally, 68 ECGs from the E-OTH-12-0068-010 database of the Telemetric and Holter ECG Warehouse were analyzed. The V-index coherently increased after sotalol administration, a drug known to have QT-prolonging potential (p << 0.001).
authors: Dipartimento di Tecnologie dell’Informazione, Università degli Studi di Milano, Crema 26013, Italy. roberto.sassi@unimi.it
authors: Roberto
authors: R
authors: Sassi
authors: Luca T
authors: LT
authors: Mainardi
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D004562:Electrocardiography / Q000379:methods*; D006329:Heart Conduction System / Q000502:physiology; D006801:Humans; D008297:Male; D008564:Membrane Potentials / Q000502:physiology*; D008955:Models, Cardiovascular; D015233:Models, Statistical; D032383:Myocytes, Cardiac / Q000502:physiology; D015203:Reproducibility of Results; D016276:Ventricular Function / Q000502:physiology*