Physiological measurement
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Physiological measurement · Jun 2007
Clinical TrialSample entropy of electrocardiographic RR and QT time-series data during rest and exercise.
Sample entropy (SampEn) is a measure of the complexity of data. Few studies have compared the SampEn of electrocardiographic cardiac interval (RR) data (SampEn-RR) during differing physiological states, and none have examined SampEn for the corresponding QT interval (SampEn-QT). The aim of this study was to quantify SampEn-RR and SampEn-QT during rest and for a range of exercise workloads. ⋯ SampEn-RR was also negatively correlated with normalized LF and LF/HF parameters. We interpret changes in SampEn for RR and QT data in terms of the altered autonomic nervous system (ANS) control of either the atrial or the ventricular myocardium (or both) during discrete physiological states. We speculate that greater complexity in QT data might be explained by a direct ANS influence on the ventricular myocardium.