PhD Student, Warsaw University of Technology
Influence of specific accelerations and other properties of RR time intervals in nighttime recording
Heart rate variability (HRV) is the physiological phenomenon of variation in the time interval between heartbeats. It is measured by the variation in the beat-to-beat interval. The dynamics of HRV is modulated mainly by the branches of autonomic nervous system (AUN) - the part of nervous system which is not directly controlled by organism. However, there are also some repeated modulations which are not an oscillatory character but rather have additional events form. I focus on kind of that events as laminar declines - approximately 20-40 seconds long – of RR interval in the nighttime recordings observed in group of the 84 healthy adults. The shape of acceleration is very repetitive between the subjects and characterizing by relatively high amplitude of the local minimum, laminar and persistent dynamics on the slopes and greater number of intervals on the left (descendent) slope than on the right (ascendant) slope. Although, these events are only approximately 5% of whole night-time signal, it seems that the occurrence of them have a crucial role in the values of parameters described and widely used of HRV dynamics. Comparison analysis between the signals with and without these accelerations showed significant differences in many linear and nonlinear properties (either in time, frequency domain, thus the differences between signals are complex) of RR time interval series. These specific events were not simulated in the current models of HRV so far (except of my model published in Chaos Journal in 2016). Exploration of this subject could bring a completely new view in interpretation of HRV dynamics, especially in the case of diagnosis of the sleep diseases, but either the analysis of AUN by itself. This valuable knowledge could be used in many practical aspects collected with noninvasive monitoring of people's health and lifestyle. The origins of this phenomenon are still not clear. Possibly explanation could be reaction to exercise episodes. However, its puzzling that the U-shape accelerations occur mainly at night and very rare during the day. Maybe the night exercise episodes are not marked by the other activity of AUN present during day. The other proposal of explain the occurring U-shape accelerations is reaction to hormonal expression, i.e. epinephrine. Later studies based on analysis of multimodal data (especially EEG, hipnograms, hormonal trends and EMG signals) should be consider.
Abstract: Decreases in heart rate variability, a marker of autonomic nervous system function, are associated with increased cardiovascular mortality. Heart rate variability increases in non-rapid eye movement sleep, peaking in slow-wave sleep. Therefore, decreasing the amount of deep sleep, for example, by introducing patients to a sleep laboratory environment, could decrease heart rate variability, increasing cardiovascular risk. We studied four groups of women with no previous sleep laboratory experience: young [n = 11, 23.1 (0.5) years]; perimenopausal [n = 15, 48.0 (0.4) years]; postmenopausal without hormone therapy [n = 22, 63.4 (0.8) years]; and postmenopausal on hormone therapy [n = 16, 63.1 (0.9) years], using a cross-sectional design. Polysomnography including electrocardiogram was performed over two consecutive nights. Heart rate variability was assessed overnight, and the first-night effect on heart rate variability was analysed. Furthermore, correlations between heart rate variability and sleep variables were analysed. Using combined groups, only minor changes were observed in non-linear heart rate variability, indicating increased parasympathetic tone from the first to the second night. No group differences in first-night effect were seen. Heart rate variability and sleep variables were not significantly correlated. Heart rate variability decreased with increasing age, and it was lowest in the postmenopausal women on hormone therapy. We conclude that a first night in a sleep laboratory elicits only minimal changes in overnight vagally mediated non-linear heart rate variability in women irrespective of reproductive state. This finding warrants further analyses in different sleep stages, but suggests that changes in sleep architecture per se do not predict the autonomic strain of a poor night.
Pub.: 27 May '17, Pinned: 31 Jul '17
Abstract: Insulin resistance is strongly associated with metabolic syndrome (MetS), but it is not known how this association is influenced by the autonomic nervous system, which controls insulin secretion.Methods and Results:The subjects were 2,016 individuals aged 30-79 years enrolled between 2009 and 2012. MetS was determined using the harmonized MetS definition, which includes waist circumference, blood pressure, triglycerides, high-density lipoprotein cholesterol, and fasting glucose. The homeostasis model assessment index for insulin resistance (HOMA-IR) and Gutt's insulin sensitivity index (ISI) were calculated based on fasting and 2 h-post-load glucose and insulin concentrations in a 75-g oral glucose tolerance test. The 5-min heart rate variability (HRV) was evaluated using time-domain indices of standard deviations of NN intervals (SDNN) and root mean square of successive differences (RMSSD). Power spectral analysis yielded frequency-domain measures for HRV: high-frequency (HF) power, low-frequency (LF) power and LF/HF. Multivariable adjusted logistic models showed that the highest quartiles for SDNN, RMSSD, LF, and HF vs. the lowest quartiles had a significant association with MetS. RMSSD, HF, and LF/HF remained significantly associated with MetS after adjustment for HOMA-IR (or ISI). Additive interactions between the levels of high LF/HF and high HOMA-IR (or low ISI) were significantly positive.Sympathovagal imbalance as evidenced by low HF and high LF/HF modified the association of insulin resistance or low insulin sensitivity with MetS.
Pub.: 02 Jun '17, Pinned: 31 Jul '17
Abstract: Neonatal, short-lasting, local, nociceptive insult by carrageenan can cause long-term alterations in somatosensory and neurohumoral systems. We previously revealed hyporesponsiveness of the autonomic nervous system (ANS) after painful stimulation of adult rats in a neonatal carrageenan-induced pain model. Sleep disturbance has been highly correlated with pain and ANS activity. In the present study, adult rats that had received an intraplantar injection of carrageenan on postnatal day 1 were investigated to determine if there were alterations in their sleep architecture upon the stimulation of pain. Polysomnographic and heart rate variability recordings were carried out, with a wireless transmission of data, for 24 h under baseline conditions and after an intraplantar injection of complete Freund's adjuvant to induce sustained nociception. Increased active awake (AW) and decreased quiet sleep (QS) and paradoxical sleep (PS) times were noted in the control animals. In the carrageenan-treated rats, the AW time increased but with decreased alertness, as revealed by decreases in beta and increases in theta power. The QS time did not decrease. The PS time decreased during the first 12 h, then increased during the following 12 h, suggesting an early rebound of formerly deprived PS time. Sympathetic activation under sustained pain was not apparent in any stage of sleep in carrageenan-treated rats and was even suppressed in AW time. An impaired sympathetic reaction to pain may have contributed to the atypical changes in sleep architecture in these rats. In conclusion, pain in early life has a long-term effect on the cardiovascular-autonomic-electroencephalographic responses to pain later in life. The physiological relevance of these results remains undetermined.
Pub.: 08 Jun '17, Pinned: 31 Jul '17
Abstract: Quantitative measurement of the dynamic changes in autonomic nervous system (ANS) during and after exercise has great significance in clinical, sports training and other fields. A consecutive ultra-short-term (30 s, UST) heart rate variability (HRV) method was proposed to track the exercise-induced autonomic control of heart rate (HR).Twenty-three healthy young men participated in the study. The first four stages of the Modified Bruce Protocol (S0-S3) were performed. Six HRV indices, i.e. HF (power of high frequency ranged from 0.15 to 0.4 Hz), LF (power of low frequency ranged from 0.04 to 0.15 Hz), LF/HF, SD1 and SD2 of Poincaré plot, and SD2/SD1, over 30 s were calculated every 5 s over 3 min RR time series during, as well as after, exercise.The results showed that during exercise, SD1, SD2, HF and LF dropped down quickly and tended to stabilize. Particularly, SD1 and HF showed a slight upward trend in the lower three stages while the declining time of SD2 in S3 lasted longer than the other stages. SD2/SD1 increased rapidly first and then decreased slowly. The values of SD2/SD1 in S3 remained higher than those in the other stages. After exercise, SD1, SD2, HF and LF kept increasing first and then declined slowly or fluctuated with decaying amplitudes. SD2/SD1 increased initially, then decreased and fluctuated slightly.Compared with the indices in frequency domain, the Poincaré indices were more sensitive and accurate in UST measurement of ANS during exercise. The results demonstrated that the UST method could characterize the dynamic changing tendency of ANS during and after exercise and quantify the differences of changes in ANS induced by exercise with different intensities. In particular, the vagal branch functioned dominantly in controlling HR in S0 but the effect of the sympathetic branch on HR enhanced with the increase of exercise intensity. In addition, the transient changes of ANS related with the sudden onset of exercise could also be reflected, despite perhaps being limited by the computation window width to some extent. Thus, the consecutive UST Poincaré indices could provide a feasible and simple method to measure quantitatively the exercise-induced dynamic changes in ANS.
Pub.: 24 Jun '17, Pinned: 31 Jul '17
Abstract: Sepsis is a serious medical condition with increasing prevalence and high mortality. The role of the autonomic nervous system in pathophysiology of sepsis has been increasingly researched. The objective of this study is to evaluate the Heart rate variability (HRV) as a predictor of mortality in septic patients.This was a prospective cohort of patients diagnosed with sepsis. Patient recruitment was carried out at ICU in tertiary university hospital between March 2012 and February 2014. Clinical data and laboratory exams were collected at admission. Each patient underwent a 20-minute Holter and a 24-hour Holter on the first day of enrollment. The primary outcome was the 28-day all-cause mortality.A total of 63 patients were included. Patients were categorized into nonsurvivor group (n = 16) or survivor group (n = 47) depending on this endpoint. Survivors were younger (48.6 years vs. 63.0 years), had better renal function and lower values in severity scores (APACHE II and SOFA) compared to nonsurvivors. In the 20-minute Holter, SDNN, Total Power, VLF Power, LF Power and LF/HF of nonsurvivors were significantly lower than those of survivors (p = <0.001, p = 0.003, p = 0.002, p = 0.006, p = 0.009 respectively). ROC curve of SDNN was built, showing area under the curve of 0.772 (0.638-0.906) for mortality. The value of 17ms was chosen as best SDNN cutoff to discriminate survivors and nonsurvivors. In the Cox proportional regression, adjusted for SOFA score and for APACHE II, a SDNN ≤ 17ms was associated with a greater risk of death, with hazard ratios of 6.3 (1.4-28.0; p = 0.015) and 5.5 (1,2-24,8; p = 0.027), respectively. The addition of the dichotomized SDNN to the SOFA model reduced AIC and increased the concordance statistic and the R2, indicating that predictive power of the SDNN + SOFA model is better than predictive power of SOFA only.Several HRV parameters are reduced in nonsurviving septic patients. SDNN ≤17 is a risk factor for death in septic patients, even after adjusting for severity scores.
Pub.: 28 Jun '17, Pinned: 31 Jul '17
Abstract: Posttraumatic stress disorder (PTSD) is characterized by dysregulated arousal and altered cardiac autonomic response as evidenced by decreased high-frequency heart rate variability (HF-HRV), an indirect measure of parasympathetic modulation of the heart. Indeed, subtle threatening cues can cause autonomic dysregulation, even without explicit awareness of the triggering stimulus. Accordingly, examining the neural underpinnings associated with HF-HRV during both sub- and supraliminal exposure to trauma-related cues is critical to an enhanced understanding of autonomic nervous system dysfunction in PTSD.We compared neural activity in brain regions associated with HF-HRV in PTSD (n = 18) and healthy controls (n = 18) during exposure to sub- and supraliminal processing of personalized trauma-related words.As compared to controls, PTSD exhibited decreased HF-HRV reactivity in response to sub- and supraliminal cues. Notably, during subliminal processing of trauma-related versus neutral words, as compared to controls, PTSD showed decreased neural response associated with HF-HRV within the left dorsal anterior insula. By contrast, during supraliminal processing of trauma-related versus neutral words, decreased neural activity associated with HF-HRV within the posterior insula/superior temporal cortex, and increased neural activity associated with HF-HRV within the left centromedial amygdala was observed in PTSD as compared to controls.Impaired parasympathetic modulation of autonomic arousal in PTSD appears related to altered activation of cortical and subcortical regions involved in the central autonomic network. Interestingly, both sub- and supraliminal trauma-related cues appear to elicit dysregulated arousal and may contribute to the maintenance of hyperarousal in PTSD. Hum Brain Mapp, 2017. © 2017 Wiley Periodicals, Inc.
Pub.: 17 Jul '17, Pinned: 31 Jul '17
Abstract: Sleep is not just the absence of wakefulness but a regulated process with an important restorative function. Based on electroencephalographic recordings and characteristic patterns and waveforms we can distinguish wakefulness and five sleep stages grouped into light sleep, deep sleep, and rapid-eye-movement (REM) sleep. In order to explore the functions of sleep and sleep stages, we investigated the dynamics of sleep stages over the night and of heart-rate variability during the different sleep stages. Sleep stages and intermediate wake states have different distributions of their duration and this allows us to create a model for the temporal sequence of sleep stages and wake states. Heart rate is easily accessed with a high precision by the recording and analysis of the electrocardiogram (ECG). Heart-rate regulation is part of the autonomous nervous system and sympathetic tone is strongly influenced by the sleep stages.
Pub.: 27 Jun '03, Pinned: 31 Jul '17