title: Symbolic dynamics to discriminate healthy and ischaemic dilated cardiomyopathy populations: an application to the variability of heart period and QT interval.
abstract: Myocardial ischaemia is hypothesized to stimulate the cardiac sympathetic excitatory afferents and, therefore, the spontaneous changes of heart period (approximated as the RR interval), and the QT interval in ischaemic dilated cardiomyopathy (IDC) patients might reflect this sympathetic activation. Symbolic analysis is a nonlinear and powerful tool for the extraction and classification of patterns in time-series analysis, which implies a transformation of the original series into symbols and the construction of patterns with the symbols. The aim of this work was to investigate whether symbolic transformations of RR and QT cardiac series can provide a better separation between IDC patients and healthy control (HC) subjects compared with traditional linear measures. The variability of these cardiac series was studied during daytime and night-time periods and also during the complete 24 h recording over windows of short data sequences of approximately 5 min. The IDC group was characterized by an increase in the occurrence rate of patterns without variations (0 V%) and a reduction in the occurrence rate of patterns with one variation (1 V%) and two variations (2 V%). Concerning the RR variability during the daytime, the highest number of patterns had 0 V%, whereas the rates of 1 V% and 2 V% were lower. During the night, 1 V% and 2 V% increased at the expense of diminishing 0 V%. Patterns with and without variations between consecutive symbols were able to increase the separation between the IDC and HC groups, allowing accuracies higher than 80%. With regard to entropy measures, an increase in RR regularity was associated with cardiac disease described by accuracy >70% in the RR series and by accuracy >60% in the QTc series. These results could be associated with an increase in the sympathetic tone in IDC patients.
authors.affiliation: Department of Electronic Engineering, Universidad de San Buenaventura, Cali, Colombia Department of Automatic Control, Center for Biomedical Engineering Research, Universitat Politècnica de Catalunya, CIBER of Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Barcelona, Spain jfvalenc@usbcali.edu.co.
authors.forename: José Fernando
authors.initials: JF
authors.lastname: Valencia
authors.affiliation: Department of Automatic Control, Center for Biomedical Engineering Research, Universitat Politècnica de Catalunya, CIBER of Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Barcelona, Spain.
authors.forename: Montserrat
authors.initials: M
authors.lastname: Vallverdu
authors.affiliation: Department of Automatic Control, Center for Biomedical Engineering Research, Universitat Politècnica de Catalunya, CIBER of Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Barcelona, Spain.
authors.forename: Isidre
authors.initials: I
authors.lastname: Rivero
authors.affiliation: Department of Medical Engineering, University of Applied Sciences, Jena, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Voss
authors.affiliation: Catalan Institute of Cardiovascular Sciences, Barcelona, Spain.
authors.forename: Antonio Bayes
authors.initials: AB
authors.lastname: de Luna
authors.affiliation: Department of Biomedical Sciences for Health, University of Milan, Milan, Italy IRCCS Galeazzi Orthopedic Institute, Milan, Italy.
authors.forename: Alberto
authors.initials: A
authors.lastname: Porta
authors.affiliation: Department of Automatic Control, Center for Biomedical Engineering Research, Universitat Politècnica de Catalunya, CIBER of Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Barcelona, Spain.
authors.forename: Pere
authors.initials: P
authors.lastname: Caminal
mesh_terms: D000328:Adult; D002311:Cardiomyopathy, Dilated / Q000175:diagnosis* / Q000503:physiopathology; D016208:Databases, Factual; D003936:Diagnosis, Computer-Assisted; D004562:Electrocardiography; D005260:Female; D064368:Healthy Volunteers; D006321:Heart / Q000502:physiology*; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D017202:Myocardial Ischemia / Q000175:diagnosis* / Q000503:physiopathology; D016011:Normal Distribution; D012815:Signal Processing, Computer-Assisted; D013564:Sympathetic Nervous System; D013997:Time Factors
keywords: QT; complexity; heart rate variability; ischaemic dilated cardiomyopathy; symbolic dynamics