The effect of the instantaneous RR interval on the dynamic properties of the heart rate and the ventricular repolarization duration variability

instantaneous RR interval on HRV and VRD variability. High resolution ECG signals of 20 normal adults were analyzed, respectively, by the normal RR interval series and by detecting the distance between the peaks of R- and T-waves (RTm). HRV and VRD variability were assessed by the mean (M), the standard deviation (SD) and root-mean-squared difference (RMS) of consecutive normal RR and RTm intervals, stratified according to RR interval histogram. Results indicate that HRV reduces as mean RR interval shortens while the VRD variability paradoxically increases.