Analysis of Ventricular Late Potentials in High Resolution Ecg Records by Time-frequency Representations

This study proposes the application of different linear and quadratic Time-Frequency Representations (TFR) for the analysis of Ventricular Late Potentials (VLP) in High-Resolution Electrocardiographic (HRECG) records. The TFR used here were Short-Time Fourier Transform (STFT), Wigner-Ville (WV) and Choi-Williams (CW) distributions. These techniques were used to evaluate the risk of Ventricular Tachycardia (VT) in postinfarction patients. For comparison, the same analysis was made on HRECG records of subjects presenting Low Arrhythmia Risk (LAR). For all TFR and both populations, two indexes on the TimeFrequency (T-F) plane were considered: a) Energy of VLP normalized with respect to the total energy of the beat (ENTOTAL) and b) Energy of VLP normalized with respect to the energy of QRS complex (ENQRS). The results indicate that the two T-F indexes of the LAR group show higher mean values than those of the VT group, for all TFR used. In addition, the ENQRS index for the WV distribution obtained the best valuation as a diagnostic test, showing the highest sensitivity and specificity values. It can be concluded that T-F analysis of HRECG is a promissory technique of diagnosis to identify postinfarct patients with high risk of VT. KeywordsVentricular Late Potentials, HighResolution ECG, Time-Frequency Representations.