Complexity Of Heart Rate Variability Research Articles

Objective measures of disordered sleep in fibromyalgia.

Patients with fibromyalgia syndrome (FM) complain of inadequate sleep, which could contribute to common symptoms including sleepiness, fatigue, or pain. However, measures that consistently and objectively distinguish FM patients remain elusive. Fifteen women with FM and 15 age- and gender-matched controls underwent 3 nights of polysomnography; Multiple Sleep Latency Tests to assess sleepiness; testing of auditory arousal thresholds during non-REM stage 2 and stage 4 sleep; overnight assessment of urinary free cortisol; and analysis of 24-hour heart rate variability. On the second night of polysomnography, women with FM in comparison to controls showed more stage shifts (p = 0.04) but did not differ significantly on any other standard polysomnographic measure or on the Multiple Sleep Latency Tests. Alpha EEG power during deep non-REM sleep, alone or as a proportion of alpha power during remaining sleep stages, also failed to distinguish the groups, as did auditory arousal thresholds. Urinary free cortisol did not differ between FM and control subjects in a consistent manner. However, decreased short-term heart rate variability (HRV) and especially ratio-based HRV among FM subjects suggested diminished parasympathetic and increased sympathetic activity, respectively. Other HRV measures suggested decreased complexity of HRV among the FM subjects. Standard measures of sleep, a gold-standard measure of sleepiness, quantified alpha-delta EEG power, auditory arousal thresholds, and urinary free cortisol largely failed to distinguish FM and control subjects. However, HRV analyses showed more promise, as they suggested both increased sympathetic activity and decreased complexity of autonomic nervous system function in FM.

Heart Rate Variability And Complexity During Static Exercise In Active Individuals With Spinal Cord Injury

Spinal cord injury (SCI) adversely affects autonomic control of heart rate (HR) at rest and during dynamic exercise. This finding may be evidenced through differences in frequency domain measures of heart rate variability (HRV) and measures that quantify complexity. Many activities of daily living in persons with SCI require static contractions. Whether persons with SCI have cardiac autonomic dysfunction in response to static exercise is not well documented. PURPOSE: To examine whether cardiac autonomic modulation as measured by HRV and HR complexity at rest and during static handgrip exercise differs between active individuals with low-level SCI and active individuals without SCI. METHODS: HRV and HR complexity were examined in 20 active individuals with SCI below T6 (11 men, 9 women; 22 + 3 yrs) and 20 active individuals without SCI (12 men, 8 women; 26 + 4 yrs) during 3 minutes of rest and 2 minutes of static handgrip exercise at 30% of maximum isometric strength. Spectral decomposition of HRV was used to obtain total power, power in low frequency (LF) and high frequency (HF) ranges, and the LF/HF ratio. HF and LF/HF were taken as measures of vagal modulation and sympatho-vagal balance, respectively. HR complexity was quantified with sample entropy, a measure of signal irregularity. Between-group differences in all variables were evaluated using 2 × 2 factorial ANOVAs. RESULTS: HR at rest and during exercise was higher in participants with SCI than participants without SCI (P < 0.05), but it increased similarly in response to handgrip exercise for both groups. In response to exercise, total power and HF decreased (P < 0.05), LF/HF increased (P < 0.05), and sample entropy did not change. All of those variables did not differ between the groups, except for sample entropy which was lower (P < 0.05) at rest and during exercise in participants with SCI. CONCLUSION: The chronotropic response to handgrip exercise is similar between active individuals with and without SCI. For both groups, HR augmentation is due to vagal withdrawal and sympathoexcitation as evidenced by reductions in HF and increases in LF/HF. Frequency domain measures of HRV suggest similar autonomic control of HR at rest and during static handgrip exercise in active individuals with and without SCI. However, individuals with SCI show evidence of lower HR complexity.

Identifying diabetic patients with cardiac autonomic neuropathy by heart rate complexity analysis

BackgroundCardiac autonomic neuropathy (CAN) in diabetes has been called a "silent killer", because so few patients realize that they suffer from it, and yet its effect can be lethal. Early sub clinical detection of CAN and intervention are of prime importance for risk stratification in preventing sudden death due to silent myocardial infarction. This study presents the usefulness of heart rate variability (HRV) and complexity analyses from short term ECG recordings as a screening tool for CAN.MethodsA total of 17 sets of ECG recordings during supine rest were acquired from diabetic subjects with CAN (CAN+) and without CAN (CAN-) and analyzed. Poincaré plot indexes as well as traditional time and frequency, and the sample entropy (SampEn) measure were used for analyzing variability (short and long term) and complexity of HRV respectively.ResultsReduced (p > 0.05)_Poincaré plot patterns and lower (p < 0.05) SampEn values were found in CAN+ group, which could be a practical diagnostic and prognostic marker. Classification Trees methodology generated a simple decision tree for CAN+ prediction including SampEn and Poincaré plot indexes with a sensitivity reaching 100% and a specificity of 75% (percentage of agreement 88.24%).ConclusionOur results demonstrate the potential utility of SampEn (a complexity based estimator) of HRV in identifying asymptomatic CAN.

Short-term heart rate complexity is reduced in patients with type 1 diabetes mellitus

Objective The aim of this study was to test whether new heart rate variability (HRV) complexity measures provide diagnostic information regarding early subclinical autonomic dysfunction in diabetes mellitus (DM). Methods HRV in DM type 1 patients ( n = 17, 10f, 7m) aged 12.9–31.5 years (duration of DM 12.4 ± 1.2 years) was compared to a control group of 17 healthy matched probands. The length of R–R intervals was measured over 1 h using a telemetric ECG system. In addition to linear measures, we assessed HRV complexity measures, including multiscale entropy (MSE), compression entropy and various symbolic dynamic measures (Shannon and Renyi entropies, normalized complexity index (NCI), and pattern classification). Results HRV magnitude was significantly reduced in patients with DM. Several HRV complexity parameters (MSE at scales 2–4, Renyi entropy, NCI) were also significantly reduced in diabetics. MSE indices and compression entropy did not correlate with linear measures. Conclusions The magnitude and complexity of HRV are reduced in young patients with DM, indicating vagal dysfunction. Significance The quantification of HRV complexity in combination with its magnitude may provide an improved diagnostic tool for cardiovascular autonomic neuropathy in DM.

Characteristics of heart rate variability entropy and blood pressure during hemodialysis in patients with end‐stage renal disease

Entropy (ENT) is a newly developed measure of the complexity of heart rate variability (HRV). The aim of this study was to characterize the complexity of HRV in patients with end-stage renal disease (ESRD) and to find a possible clinical utility. Healthy subjects and patients with ESRD undergoing hemodialysis (HD) were recruited. The HD population consisted of patients with and without diabetes mellitus (DM). An electrocardiogram was recorded before HD, and blood pressure was measured during HD. The coefficients of variation of R-R intervals, high- and low-frequency components, and ratio of the low- to high-frequency components were measured as variables of HRV. The ENT was used to describe the complexity of HRV. Forty-six healthy subjects and 27 HD patients participated in this study. The ENT negatively correlated with the duration of DM (p = 0.001), systolic blood pressure (p = 0.003), and mean blood pressure (p = 0.004) before a HD session. ENT in HD patients was lower than that in healthy subjects (p < 0.01). ENT in HD patients with DM was lower than that in HD patients without DM (p < 0.01). The change in systolic blood pressure (DeltaSBP) during a HD session showed high correlations to ENT and ultrafiltration rate (UFR) of the dialyzer. The following equation was obtained: DeltaSBP = 2.25 x ENT - 2.28 x UFR - 21.27 (R2 = 0.805; p < 0.0001). ENT decreased with uremic and diabetic status. ENT also represents a possible prediction of hypotension during a HD session.

Toward chronocardiologic and chronomic insights: dynamics of heart rate associated with head-up tilting

As a step towards investigating the chronome (i.e. the inferential endpoints of chaos, trends and rhythms) of heart rate (HR) variability (HRV), we investigated whether the fractality or complexity of HRV is affected by a head-up tilting (HUT) test in the morning after an overnight fast. Spectral and non-linear analyses of HR were performed on data gathered during an 80° passive HUT test in 15 men and 28 women 32.8 ± 11.5 years of age. The non-linear endpoints included the scaling exponents α 1 (<11 beats) and α 2 (>11 beats), which indicate fractal properties, calculated with detrended fluctuation analysis, and the approximate entropy (ApEn), a measure of overall complexity. Passive HUT increased α 1 (from 0.986 ± 0.217 to 1.370 ± 0.185; P = 0.0001), but did not alter α 2 (from 0.925 ± 0.110 to 0.958 ± 0.130; P = 0.19). A slight but statistically significant decrease in ApEn was seen during HUT (from 1.114 ± 0.131 to 1.013 ± 0.197; P = 0.002). In the tilt-up position, there was a statistically significant negative correlation between α 1 and ApEn ( r = –0.490; P < 0.05). In both the supine and the tilt-up position, α 1 was correlated weakly with HF ( r = –0.343 and r = –0.322, respectively), and strongly with LF/HF ( r = 0.557 and r = 0.795), respectively. There was also a negative correlation between ApEn and LF/HF ( r = –0.406 and r = –0.357, respectively). α 2 did not correlate with any spectral or non-linear measures of HRV. Short-term fractal properties and complexity of HR were lowered with orthostatic stress. Alterations of the autonomic activities could be partly responsible for these changes and await extension of such studies to assess the broad spectral element of HRV, that includes, with components of ~3.6 and ~10.5 s, cycles with very much lower frequencies, along the scales of hours and even years, that critically modulate the mislabeled (only relatively high- and low-frequency) components in the range of seconds or minutes.

Heart rate dynamics and cardiorespiratory coordination in diabetic and breast cancer patients

Objective of this study was to evaluate cardiac autonomic function in female breast cancer patients on the basis of linear and non-linear heart rate variability (HRV) as well as on musical heart rate rhythmicity. The latter method has been recently developed and enables particularly the quantification of cardiorespiratory coordination solely on the basis of ECG recordings. To provide a broad basis of comparability, 37 breast cancer patients were compared with 37 age-matched healthy women and 40 age-matched female diabetic patients who serve as pathological controls. During night sleep, all parameters showed a tendency towards lower variability, complexity or rhythmicity of HRV in cancer patients. The most prominent alterations were found for the binary pattern predominance (PP) and for the ratio of heart rate and respiration. In particular, when comparing metastasized and non-metastasized cancer patients, the discriminatory power of binary heart rate rhythmicity emerges: the histograms of 1-h intervals during night sleep with a predominance of cyclically recurrent phase locking patterns unveiled a clear transition from higher to lower cardiorespiratory coordination ratios and to a loss of coordination capability in metastasized patients.

Assessment of the primary effect of aging on heart rate variability in humans

Beat-to-beat heart rate variability (HRV), reflecting cardiac autonomic control mechanisms, is known to change with age. However, the degree to which this change is mediated by aging per se or by physiologic changes characteristic of normative aging is still unclear. This study was designed to examine the association of aerobic fitness, body habitus or obesity, and blood pressure with age-related changes in HRV. Resting HRV data was recorded from 373 healthy subjects (124 men, 249 women; age range, 16-69 y) and analyzed by coarse-graining spectral analysis to decompose the total spectral power into its harmonic and fractal components. The low- and high-frequency (LF, 0.0-0.15 Hz; HF, >0.15 Hz) harmonic components were calculated from the former, whereas the latter was used to calculate the integrated power (FR) and the spectral exponent , beta, which were, in turn, used to evaluate the overall complexity of HRV. Factor analysis was performed to test whether potentially age-related changes in the components of HRV might be observed secondarily through other variables affecting HRV. Significant (p <0.05) age-related changes in the harmonic (HF and LF) and fractal (FR and beta) components of HRV were generally consistent with those described in the literature. In addition, factor analysis showed that there was a unique common factor that primarily explained correlations among age, HF, and beta (p <0.05) without the contributions from LF, FR, aerobic fitness, body habitus or obesity, and blood pressure. It was concluded that, in this population-based sample, age-related changes in HF and beta, both of which reflect vagal modulation of heart rate, were primarily mediated by aging per se and not by physiologic changes characteristic of normative aging.

Evolution in functional complexity of heart rate dynamics: a measure of cardiac allograft adaptability.

The capacity of self-organized systems to adapt is embodied in the functional organization of intrinsic control mechanisms. Evolution in functional complexity of heart rate variability (HRV) was used as measure of the capacity of the transplanted heart to express newly emergent regulatory order. In a cross-sectional study of 100 patients after (0-10 yr) heart transplantation (HTX), heart rate dynamics were assessed using pointwise correlation dimension (PD2) analysis. A new observation is that, commencing with the acute event of allograft transplantation, the dynamics of rhythm formation proceed through complex phase transitions. At implantation, the donor heart manifested metronome-like chronotropic behavior (PD2 approximately 1.0). At 11-100 days, dimensional complexity of HRV reached a peak (PD2 approximately 2.0) associated with resurgence in the high-frequency component (0.15-0.5 Hz) of the power spectral density. Subsequent dimensional loss to PD2 approximately 1.0 at 20-30 mo after HTX was followed by a progressive near-linear gain in system complexity, reaching PD2 approximately 3.0 7-10 yr after HTX. The "dynamic reorganization" in the allograft rhythm-generating system, seen in the first 100 days, is a manifestation of the adaptive capacity of intrinsic control mechanisms. The loss of HRV 2 yr after HTX implies a withdrawal of intrinsic autonomic control and/or development of an entrained dynamic pattern characteristic of extrinsic sympathetic input. The subsequent long-term progressive rise in dimensional complexity of HRV can be attributed to the restoration of a functional order patterning parasympathetic control. The recognition that the decentralized heart can restitute the multidimensional state space of HR generator dynamics independent of external autonomic signaling may provide a new perspective on principles that constitute homeodynamic regulation.

The staining of proteins and lipoids after electrophoresis on filter paper.

<h3>Objective</h3> Patients with fibromyalgia syndrome (FM) complain of inadequate sleep, which could contribute to common symptoms including sleepiness, fatigue, or pain. However, measures that consistently and objectively distinguish FM patients remain elusive. <h3>Methods</h3> Fifteen women with FM and 15 age- and gender-matched controls underwent 3 nights of polysomnography; Multiple Sleep Latency Tests to assess sleepiness; testing of auditory arousal thresholds during non-REM stage 2 and stage 4 sleep; overnight assessment of urinary free cortisol; and analysis of 24-hour heart rate variability. <h3>Results</h3> On the second night of polysomnography, women with FM in comparison to controls showed more stage shifts (p = 0.04) but did not differ significantly on any other standard polysomnographic measure or on the Multiple Sleep Latency Tests. Alpha EEG power during deep non-REM sleep, alone or as a proportion of alpha power during remaining sleep stages, also failed to distin- guish the groups, as did auditory arousal thresholds. Urinary free cortisol did not differ between FM and control subjects in a consistent manner. However, decreased short-term heart rate variability (HRV) and especially ratio-based HRV among FM subjects suggested diminished parasympathetic and increased sympathetic activity, respectively. Other HRV measures suggested decreased complexity of HRV among the FM subjects. <h3>Conclusion</h3> Standard measures of sleep, a gold-standard measure of sleepiness, quantified alpha-delta EEG power, auditory arousal thresholds, and urinary free cortisol largely failed to distinguish FM and control subjects. However, HRV analyses showed more promise, as they suggested both increased sympathetic activity and decreased complexity of autonomic nervous system function in FM.