Dynamic response of temporal and spatial ventricular repolarization dispersion indices during abrupt heart rate changes

Abstract

Ventricular repolarization dispersion (VRD) has been shown to constitute a substrate for arrhythmias. We analyzed the evolution of different electrocardiogram indices of VRD responding to changes in heart rate (HR) induced by a Tilt-test in healthy subjects. We studied temporal indices of VRD (T-VRD), based on ECG-intervals, and spatial indices of VRD (S-VRD), based on spatial correlation matrix eigenvalues of the electrocardiogram. In T-VRD analysis, the T-wave onset-to-peak ITOP index showed significant decrease during abrupt RR decreases with respect to supine position. Regarding S-VRD, we observed a significant increase of the first eigenvalue of the ascending T-wave limb ILamda1A for abrupt RR decreases with respect to supine position. Conversely, we found non-significant changes in the T-wave peak to- end ITPE and in the first eigenvalue of the descending T-wave limb ILamda1D . Results indicate that under HR increases the first portion of T-wave, ITOP and ILamda1A, has changed significantly with respect to supine position. Moreover, considering that VRD between two site either at epicardium and endocardium, or other apicobasal sites defines the peak of the T-wave, we can concluded that the global action potential duration distance responsible for ITOP respond to abrupt increases of HR, whereas ITPE and ILamda1D, are not significantly altered.