Key result
Head-up tilt significantly reduced sample entropy of RR intervals, while mental arithmetic stress significantly reduced RR-to-QT coupling in healthy subjects.
Why the study?
Are entropy measures of RR and QT interval variability suitable to detect changes in neural outflow to the heart elicited by orthostatic and mental stress in healthy subjects?
Observational (n=11)
Are entropy measures of RR and QT interval variability suitable to detect changes in neural outflow to the heart elicited by orthostatic and mental stress in healthy subjects?
Entropy analysis of RR and QT intervals can effectively detect changes in cardiac autonomic neural outflow and repolarization variability induced by different stress paradigms.
Supports entropy measures for autonomic detection in healthy subjects; leaves open validation and clinical utility in patients.
Autonomic activity affects beat-to-beat variability of heart rate and QT interval. The aim of this study was to explore whether entropy measures are suitable to detect changes in neural outflow to the heart elicited by two different stress paradigms. We recorded short-term ECG in 11 normal subjects during an experimental protocol that involved head-up tilt and mental arithmetic stress and computed sample entropy, cross-sample entropy and causal interactions based on conditional entropy from RR and QT interval time series. Head-up tilt resulted in a significant reduction in sample entropy of RR intervals and cross-sample entropy, while mental arithmetic stress resulted in a significant reduction in coupling directed from RR to QT. In conclusion, measures of entropy are suitable to detect changes in neural outflow to the heart and decoupling of repolarisation variability from heart rate variability elicited by orthostatic or mental arithmetic stress.
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Baumert et al. (2014) conducted an observational in Healthy subjects (n=11). Head-up tilt and mental arithmetic stress was evaluated on Sample entropy, cross-sample entropy and causal interactions from RR and QT interval time series. Head-up tilt significantly reduced sample entropy of RR intervals, while mental arithmetic stress significantly reduced RR-to-QT coupling in healthy subjects.
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