title: Temporal asymmetries of short-term heart period variability are linked to autonomic regulation.
abstract: We exploit time reversibility analysis, checking the invariance of statistical features of a series after time reversal, to detect temporal asymmetries of short-term heart period variability series. Reversibility indexes were extracted from 22 healthy fetuses between 16th to 40th wk of gestation and from 17 healthy humans (aged 21 to 54, median=28) during graded head-up tilt with table inclination angles randomly selected inside the set {15, 30, 45, 60, 75, 90}. Irreversibility analysis showed that nonlinear dynamics observed in short-term heart period variability are mostly due to asymmetric patterns characterized by bradycardic runs shorter than tachycardic ones. These temporal asymmetries were 1) more likely over short temporal scales than over longer, dominant ones; 2) more frequent during the late period of pregnancy (from 25th to 40th week of gestation); 3) significantly present in healthy humans at rest in supine position; 4) more numerous during 75 and 90 degrees head-up tilt. Results suggest that asymmetric patterns observable in short-term heart period variability might be the result of a fully developed autonomic regulation and that an important shift of the sympathovagal balance toward sympathetic predominance (and vagal withdrawal) can increase their presence.
authors.affiliation: Università degli Studi di Milano, Dipartimento di Tecnologie per la Salute, Istituto Ortopedico Galeazzi, Laboratorio di Modellistica di Sistemi Complessi, Via R. Galeazzi 4, 20161 Milan, Italy. alberto.porta@unimi.it
authors.forename: A
authors.initials: A
authors.lastname: Porta
authors.forename: K R
authors.initials: KR
authors.lastname: Casali
authors.forename: A G
authors.initials: AG
authors.lastname: Casali
authors.forename: T
authors.initials: T
authors.lastname: Gnecchi-Ruscone
authors.forename: E
authors.initials: E
authors.lastname: Tobaldini
authors.forename: N
authors.initials: N
authors.lastname: Montano
authors.forename: S
authors.initials: S
authors.lastname: Lange
authors.forename: D
authors.initials: D
authors.lastname: Geue
authors.forename: D
authors.initials: D
authors.lastname: Cysarz
authors.forename: P
authors.initials: P
authors.lastname: Van Leeuwen
mesh_terms: D000328:Adult; D001341:Autonomic Nervous System / Q000196:embryology / Q000502:physiology*; D004562:Electrocardiography; D005260:Female; D005323:Fetal Monitoring / Q000379:methods; D005865:Gestational Age; D006321:Heart / Q000196:embryology / Q000294:innervation*; D006339:Heart Rate; D006801:Humans; D053798:Magnetocardiography; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D017711:Nonlinear Dynamics; D011187:Posture; D011247:Pregnancy; D013997:Time Factors