1,720,980 research outputs found
Heart Rate Variability in Noltisalis Database: Twenty-Four-Hour Fractal Dimension Analysis
No full textNonlinear analysis of HRV has recently been recognized to provide valuable information in the
prognostic classification of cardiac patients. Among the numerous non-linear parameters related to the fractal
behaviour of the HRV signal, two classes have gained wide interest in the last years: that based on the 1/flike
relationship, starting from the spectral power, and that based on fractal features. We present results
obtained from the analysis of 50 heart rate variability series which have been extracted from Holter
recordings in the 24-hours in normal subjects and pathological patients. Data have been collected inside a
multicentric research program, which aimed at the nonlinear analysis of heart rate variability series.
Differently from methods usually used in literature to evaluate the fractal dimension, the parameter used in
this work has been extracted directly from the HRV sequences in the time domain, by means of the Higuchi's
algorithm. Results show that this fractal dimension can be used to separate normal subjects from patients
suffering from cardiovascular diseases and to evaluate the presence of circadianity in the HRV over the
whole twenty four hours
Twenty-four-hour fractal dimension analysis of heart rate variability in NOLTISALIS database
No full textAssessment of cardiovascular regulation through irreversibility analysis of heart period variability : a 24 hours Holter study in healthy and chronic heart failure populations
No full textWe propose an approach based on time reversibility analysis to characterize the cardiovascular regulation and its nonlinearities as derived from 24 hours Holter recordings of heart period variability in a healthy population (n=12, age: median=43 years, range=34-55 years) and in a pathological group of age-matched chronic heart failure (CHF) patients (n=13, primarily in NYHA class II, age: median=37 years, range=33-56 years, ejection fraction: median=25%, range=13-30%). Two indices capable of detecting nonlinear irreversible dynamics according to different strategies of phase-space reconstruction (i.e. a fixed two-dimensional phase-space reconstruction and an optimal selection of the embedding dimension, respectively) are tested and compared with a more traditional nonlinear index based on local nonlinear prediction. Results showed that nonlinear dynamics owing to time irreversibility at short time scales are significantly present during daytime in healthy subjects, more frequently present in the CHF population and less frequently during night-time in both groups, thus suggesting their link with a dominant sympathetic regulation and/or with a vagal withdrawal. On the contrary, nonlinear dynamics owing to time irreversibility at longer, dominant time scales were insignificantly present in both groups. During daytime in the healthy population, irreversibility was mostly due to the presence of asymmetric patterns characterized by bradycardic runs shorter than tachycardic ones. Nonlinear dynamics produced by mechanisms different from those inducing temporal irreversibility were significantly detectable in both groups and more frequently during night-time. The present study proposes a method to distinguish different types of nonlinearities and assess their contribution over different temporal scales. Results confirm the usefulness of this method even when applied in uncontrolled experimental conditions such as those during 24 hours Holter recording
Reproducibility of the heart rate variability regularity index in chronic heart failure patients
No full textAmong non linear analysis of HRV, information domain analysis has recently gained wide interest, allowing to evaluate regularity, defined as the degree of recurrence of a pattern in a signal. The reproducibility of this method, however, is not known and in this study we addressed this issue in the population of chronic heart failure (CHF) patients. We analyzed three 24-hour ECG Holter recordings in 25 clinically stable CHF patients by a regularity index, based on the evaluation of the conditional entropy. We studied the mean values over 24 hours and, separately, during the nighttime and daytime periods to assess the regularity index reproducibility by the standard error of within-patient variability. Results suggest the need of an appropriate signal detrending to fulfill stationarity criteria and to obtain a better reproducible regularity indexes in long-term recordings
Correlations between heart rate turbulence indexes and pre-ectopic heart rate in chronic heart failure patients
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Accelerometric and optical mechanomyogram in spectral and information domain: isometric load and fatigue
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