title: Dependency Structures in Differentially Coded Cardiovascular Time Series.
abstract: Objectives. This paper analyses temporal dependency in the time series recorded from aging rats, the healthy ones and those with early developed hypertension. The aim is to explore effects of age and hypertension on mutual sample relationship along the time axis.Methods. A copula method is applied to raw and to differentially coded signals. The latter ones were additionally binary encoded for a joint conditional entropy application. The signals were recorded from freely moving male Wistar rats and from spontaneous hypertensive rats, aged 3 months and 12 months.Results. The highest level of comonotonic behavior of pulse interval with respect to systolic blood pressure is observed at time lagsτ= 0, 3, and 4, while a strong counter-monotonic behavior occurs at time lagsτ= 1 and 2.Conclusion. Dynamic range of aging rats is considerably reduced in hypertensive groups. Conditional entropy of systolic blood pressure signal, compared to unconditional, shows an increased level of discrepancy, except for a time lag 1, where the equality is preserved in spite of the memory of differential coder. The antiparallel streams play an important role at single beat time lag.
authors.affiliation: School of Medicine, Laboratory for Cardiovascular Pharmacology, University of Belgrade, Dr. Subotica 1, 11000 Belgrade, Serbia.
authors.forename: Tatjana
authors.initials: T
authors.lastname: Tasic
authors.affiliation: Telecom Serbia, Network and Services Planning and Development Function, Bulevar Umetnosti 16a, 11070 Novi Beograd, Serbia.
authors.forename: Sladjana
authors.initials: S
authors.lastname: Jovanovic
authors.affiliation: Faculty of Technical Sciences, Center of Excellence CEVAS, University of Novi Sad, Trg Dositeja Obradovica 6, 21000 Novi Sad, Serbia.
authors.forename: Omer
authors.initials: O
authors.lastname: Mohamoud
authors.affiliation: Faculty of Technical Sciences, Center of Excellence CEVAS, University of Novi Sad, Trg Dositeja Obradovica 6, 21000 Novi Sad, Serbia.
authors.forename: Tamara
authors.initials: T
authors.lastname: Skoric
authors.affiliation: School of Medicine, Laboratory for Cardiovascular Pharmacology, University of Belgrade, Dr. Subotica 1, 11000 Belgrade, Serbia.
authors.forename: Nina
authors.initials: N
authors.lastname: Japundzic-Zigon
authors.affiliation: Faculty of Technical Sciences, Center of Excellence CEVAS, University of Novi Sad, Trg Dositeja Obradovica 6, 21000 Novi Sad, Serbia.
authors.forename: Dragana
authors.identifier: 0000-0002-4662-7939
authors.initials: D
authors.lastname: Bajic
mesh_terms: D000818:Animals; D001794:Blood Pressure; D002309:Cardiology / Q000295:instrumentation / Q000379:methods*; D002318:Cardiovascular Diseases / Q000503:physiopathology*; D002319:Cardiovascular System; D004195:Disease Models, Animal; D006339:Heart Rate; D006973:Hypertension / Q000503:physiopathology*; D008297:Male; D008490:Medical Informatics; D051381:Rats; D017208:Rats, Wistar; D012815:Signal Processing, Computer-Assisted; D013599:Systole; D013997:Time Factors