Abstract
Refined multiscale entropy (RMSE) technique was introduced to evaluate complexity of a time series over multiple scale factors ‘t’. Here threshold value ‘r’ is updated as 0.15 times SD of filtered scaled time series. The use of fixed threshold value ‘r’ in RMSE sometimes assigns very close resembling entropy values to certain time series at certain temporal scale factors and is unable to distinguish different time series optimally. The present study aims to evaluate RMSE technique by varying threshold value ‘r’ from 0.05 to 0.25 times SD of filtered scaled time series and finding optimal ‘r’ values for each scale factor at which different time series can be distinguished more effectively. The proposed RMSE was used to evaluate over HRV time series of normal sinus rhythm subjects, patients suffering from sudden cardiac death, congestive heart failure, healthy adult male, healthy adult female and mid-aged female groups as well as over synthetic simulated database for different datalengths ‘N’ of 3000, 3500 and 4000. The proposed RMSE results in improved discrimination among different time series. To enhance the computational capability, empirical mathematical equations have been formulated for optimal selection of threshold values ‘r’ as a function of SD of filtered scaled time series and datalength ‘N’ for each scale factor ‘t’.
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Acknowledgement
The authors are grateful to Department of Electronics & Communication Engineering and administration of Dr. B R Ambedkar National Institute of Technology, Jalandhar (Punjab) for providing every kind of technical and administrative help for the present work. The present work has been carried out in its ‘Medical Imaging and Computational Modeling of Physiological Systems Research Laboratory’ and ‘Biomedical Signal Processing and Telemedicine Laboratory’. The authors acknowledge all technical support provided by above laboratories.
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There is no conflict of interest in respect of the research work being presented in this manuscript.
Human and Animal Studies
All procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1975, as revised in 2000 (5). Informed consent was obtained from all patients for being included in the study. No animal studies were carried out by the authors for this article.
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Associate Editor Ajit P. Yoganathan oversaw the review of this article.
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Marwaha, P., Sunkaria, R.K. Optimal Selection of Threshold Value ‘r’ for Refined Multiscale Entropy. Cardiovasc Eng Tech 6, 557–576 (2015). https://doi.org/10.1007/s13239-015-0242-x
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DOI: https://doi.org/10.1007/s13239-015-0242-x