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 lags τ = 0, 3, and 4, while a strong counter-monotonic behavior occurs at time lags τ = 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.

Voronoi Decomposition of Cardiovascular Dependency Structures in Different Ambient Conditions: An Entropy Study

“…It was shown [ 49 ] that the delay of 0, 1, and 2 beats is the most appropriate for humans, while the delays of 3, 4 and 5 beats are appropriate for rats [ 29 ] and mice [ 47 ]. In [ 50 ], it was shown that, in laboratory rats, the highest level of comonotonic behavior of pulse interval and systolic blood pressure is observed at time lags 0, 3, and 4 beats, while a strong counter-monotonic behavior occurs at time lags of 1 and 2 beats.…”

Sequences and antisequences in hypertensive patients under therapyPlatform

“…A survey of Verapamil in literature includes the effect considering cardiac arrhythmias [17], atrial fibrillation [18] and mortality after myocardial infarction [19], but without the assessment of SBP and RRI linear and non-linear relationship using cross-entropy and copula in connection to the baroreflex sensitivity.…”

Artifacts in dependency structures of Portapres® signals

“…Numerous copula families exist, but pharmacological validation has shown that Frank copula is the most suitable choice for the cardiovascular signals [31]: it is unbounded and symmetric, it is equal to zero if the signals are statistically independent, it is more sensitive for SBP-PI signal changes than the other families of explicit and implicit copulas, and in SBP-PI case it models both the comonotonic and the countermonotonic dependence. Application examples of Frank copula in a context of SBP-PI relationship are shown in [32].…”