Characterization of the temporal evolution of the ECG indices under abrupt heart rate changes in healthy subjects

Abstract

Abnormal alterations in ventricular repolarization dispersion (VRD) have been shown to constitute a substrate for arrhythmias. In this work, we have induced abrupt heart rate (HR) changes to 17 healthy subjects through a Tilttest and have analyzed the evolution of a set of ECG indices: Temporal ones (T-VRD), based on classic ECG intervals, and morphological ones (M-VRD), extracted features from an absolute T-wave. The quantification has been done by computing the alterations in index value and calculating their response time. In T-VRD indices, results have shown statistically significant decreases in T-wave onset-to-peak (TOP). Furthermore, these changes are responsible about the alterations in the T-wave width and in the QT interval. T-wave peak-to-end (TPE) has not shown statistical significance. Regarding M-VRD indices, we have observed that the shape of the T-wave undergoes to a fast initial reduction in amplitude and a posterior slow shifting toward the QRS-complex. The area of the both halves of the T-wave have shown statistically significant decreases, but relationship between themselves has remained practically constant. Finally, several ECG indices have reached the steady state before the RR interval. This study provides the normal range of VRD values in healthy young subjects during HR changes.