Beat-to-beat ventricular repolarization variability evaluated during acute myocardial ischemia

Beat-to-beat electrocardiographic analysis of ventricular repolarization variability in patients after myocardial infarction

“…After that, if the cross-correlation coefficient between QRS complexes and each QRS template was greater than 98%, a new jitter-corrected QRS complex is obtained, otherwise the complex was rejected. Taken 80 ms from fiducially jitter-corrected QRS endpoint, a T-wave window of 250 ms duration was defined in order to construct an aligned T-waves matrix [13]. This determined the input matrix containing arranged T-waves for the 2D-FFT process.…”

“…We computed the TSV index using the algorithm described in [12], which was modified by Valverde et al in [13]. Briefly, a one-dimensional FFT (1D-FFT) is applied to each T-wave of the T-waves matrix, and the frequency contents were determined.…”

“…Also, we have evaluated the noise/T-wave amplitude ratio (NTR) between the spectral energy from noise bandwidth (50-100 Hz) respect to the spectral energy of the T-wave (0-50 Hz), both greater than 0 cpb [13].…”

“…On the other hand, it has shown that modifications in the morphology of the T-wave are associated with an increase of repolarization heterogeneity [8,9]. There is evidence that low level beat-to-beat variations in ventricular repolarization can be measured by using the T-wave spectral variance (TSV) index method, based on the two-dimensional Fourier transform (2D-FFT), which allows to detect dynamic changes in the repolarization pattern independently of the exact definition of the end point of the T-wave [10][11][12][13]. Steinbigler et al showed that TSV index revealed an increased heterogeneity of the ventricular repolarization in patients prone to ventricular tachycardia (VT) and ventricular fibrillation (VF) after MI in two standarized Holter orthogonal leads, while the corrected QT interval showed no significant differences [10].…”

“…Also, Valverde et al studied the temporal evolution of TSV index in a single ECG lead using a model of chronic infarcted animals [11]. Later, in another work, Valverde et al found that there was a preferential ECG lead to analyze the TSV index depending on the occlusion site during a percutaneous coronary intervention procedure [13].…”