Title :
A characterization of HRV´s nonlinear hidden dynamics by means of Markov models
Author :
Silipo, Rosaria ; Deco, Gustavo ; Vergassola, Rossano ; Gremigni, Celio
Author_Institution :
Int. Comput. Sci. Inst., Berkeley, CA, USA
Abstract :
A study of the 24-h heart rate variability´s (HRV) hidden dynamic is performed hour by hour, in order to investigate the evolution of the nonlinear structure of the underlying nervous system. A hierarchy of null hypotheses of nonlinear Markov models with increasing order n is tested against the hidden dynamic of the HRV time series. The minimum accepted Markov order supplies information about the nonlinearity of the HRV´s hidden dynamic and consequently of the underlying nervous system. The Markov model with minimum order is detected for each hour of the RR time series extracted from seven 24-h electrocardiogram records of patients in different patho-physiological conditions, some including ventricular tachycardia episodes. Heart rate, pNN30, and LF/HF index plots are reported to serve as a reference for the description of the patient´s cardiovascular frame during each examined hour. The minimum Markov order shows to be a promising index for quantifying the average nonlinearity of the autonomic nervous system´s activity.
Keywords :
Markov processes; cardiovascular system; electrocardiography; higher order statistics; neurophysiology; nonlinear dynamical systems; physiological models; spectral analysis; time series; 24 hour; HRV time series; LF/HF index plots; RR time series; average nonlinearity; cardiovascular frame; circadian rhythm; cumulants; electrocardiogram records; heart rate variability; minimum accepted Markov order; nervous system nonlinear structure; nonlinear Markov models; nonlinear hidden dynamics; null hypothesis; spectral analysis; ventricular tachycardia episodes; Cardiology; Chaos; Data mining; Heart rate; Heart rate variability; Information analysis; Nervous system; Nonlinear dynamical systems; Spectral analysis; Testing; Aged; Algorithms; Angina Pectoris; Circadian Rhythm; Data Interpretation, Statistical; Electrocardiography; Electrocardiography, Ambulatory; Exercise Test; Female; Fourier Analysis; Heart Rate; Humans; Male; Markov Chains; Middle Aged; Models, Cardiovascular; Myocardial Ischemia; Nonlinear Dynamics; Risk Factors; Tachycardia, Ventricular; Time Factors;
Journal_Title :
Biomedical Engineering, IEEE Transactions on