Comparative analysis of short-term variability of RR and QT intervals for the assessment of autonomic nerve activity

The purpose of this study is to investigate the behavior of autonomic nervous system (ANS), reflected by short-term variability (STV), in the hemodialysis patients with high risk for cardiac arrhythmias and sudden cardiac death. Comparison was performed with normal people. The data were provided by THEW (database ESRD and Normal). STV of RR intervals (STV
_RR
) and QT intervals (STV
_QT
) as well as the ratio of them (STV
_QT/RR
) were calculated using 30 consecutive beats. Two resting episodes lasting 1 h were selected in each Holter record, one by day, the other at night. For each 1 h interval series, a sliding window with width of 30 beats was implemented and indexes of each sliding window within the episode were averaged as the feature indexes (MSTV
_RR
, MSTV
_QT
and MSTV
_QT/RR
) of this episode. Results showed that MSTVRR in ESRD was much lower than that in Normal. Though the level of MSTV
_QT/RR
by day was comparable in these two groups, there existed significantly increased MSTV
_QT/RR
at night in ESRD. The decreased heart rate variability (HRV) and increased MSTV
_QT/RR
at night suggest the sympathetic overactivity in ESRD. Comparative analysis of HRV and QT variability using Holter data might be a potential approach to get information of ANS modulation.