title: Assessing nonlinear properties of heart rate variability from short-term recordings: are these measurements reliable?
abstract: Several parameters assessing nonlinear properties of heart rate variability (HRV) from short-term (<10 min) laboratory recordings have been proposed so far, but their reliability is unknown. In this study, we addressed this issue analysing a comprehensive set of these indices. In 42 healthy subjects (mean age (min-max): 38 (26-56) years, 21 men) we recorded 5 min of supine ECG in two consecutive days. From RR intervals we computed 11 nonlinear HRV indices, representative of symbolic dynamics, entropy, fractality, predictability, empirical mode decomposition and Poincaré plot families. Absolute reliability was assessed by the 95% limits of random variation and relative reliability was assessed computing the intraclass correlation coefficient (ICC). We found marked differences in the reliability of short-term nonlinear indices of HRV. In the majority of indices, changes in test-retest measurements ranged between about -30% and +50%, indicating good absolute reliability while in the others the change was <-60% and >140%. Relative reliability was substantial (0.6 < ICC < 0.8) in half of the indices, moderate in one and poor in the remaining. Compared to classical linear indices, nonlinear HRV parameters seem more suitable for individual test-retest evaluations but, due to a reduced ICC, they need increased sample size in comparative studies involving two groups of subjects.
authors.affiliation: Dipartimento di Bioingegneria, Fondazione S Maugeri, IRCCS, 27040 Montescano, Italy. rmaestri@fsm.it
authors.forename: Roberto
authors.initials: R
authors.lastname: Maestri
authors.forename: Gian Domenico
authors.initials: GD
authors.lastname: Pinna
authors.forename: Alberto
authors.initials: A
authors.lastname: Porta
authors.forename: Rita
authors.initials: R
authors.lastname: Balocchi
authors.forename: Roberto
authors.initials: R
authors.lastname: Sassi
authors.forename: Maria Gabriella
authors.initials: MG
authors.lastname: Signorini
authors.forename: Maria
authors.initials: M
authors.lastname: Dudziak
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Raczak
mesh_terms: D000328:Adult; D003198:Computer Simulation; D003627:Data Interpretation, Statistical; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D015233:Models, Statistical; D017711:Nonlinear Dynamics; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013997:Time Factors