Autonomic nervous function after evening bright light therapy: spectral analysis of heart rate variability

In order to investigate the effects of 5000 lx evening bright light on autonomic nervous function, a spectral analysis was used to assess heart rate variability in consecutive 5-min epochs just after 60 min of bright light therapy was given to 12 young women (range: 20-21 years of age). The study revealed that a low frequency band (LF) increased in bright light conditions (BL) in comparison with controlled conditions (CL). High frequency band (HF), LF:HF ratio and the coefficient of variance (CV R-R) were not significantly different between the two conditions. These results indicate that 5000 lx evening bright light may affect sympathetic nervous system activity in healthy women.     

偏头痛患者的自主神经功能及其定量测定

用心率变异频谱分析定量测定６５例偏头痛患者和５０例健康人仰卧位和站立位自主神经系统功能。结果发现，偏头痛患者站立位中频段积分较对照组显著降低（Ｐ〈０．００１），表明其交感神经功能低下，且随着疼痛程度的增加及病程的延长，其交感神经功能低下的程度迹越重，本文还初步探讨了其机理及临床应用意义。     

A comparison of cardiovascular reflex tests and spectral analysis of heart rate variability in healthy subjects

Determination of whether results of cardiovascular reflex tests and spectral analysis of heart rate variability are age dependent and whether there is correlation between results of both, cardiovascular reflex tests (the Valsalva manoeuvre, deep breathing test, handgrip test, cold face stimulus test, orthostatic test) and spectral analysis of heart rate variability were performed on 83 healthy volunteers of both genders, aged 21 to 70 years. We found that results of all heart rate based tests and results of spectral analysis decreased with aging, while results of blood pressure based tests did not. Parasympathetic activity predominated in younger subjects, while in older subjects sympathetic activity was dominant. Valsalva, deep breathing, and orthostatic ratios correlated with integrals of amplitude spectra in the standing posture and deep breathing and cold face stimulus ratios with integrals of amplitude spectra in the supine posture, whereas blood pressure changes during handgrip and orthostatic test did not correlate with integrals of the amplitude spectra. These findings suggest that tests based on heart rate may be more sensitive than tests based on blood pressure changes. This study supports the use of spectral analysis as an additional clinical test of autonomic nervous system function and stresses the importance of age in the evaluation of the results of autonomic nervous system function testing.     

心率变异光谱分析定量测定偏头痛患者自主神经功能及其意义初探

心率变异光谱分析定量测定６５例偏头痛患者和５０例健康人仰卧位和站立位自主神经系统（ＡＮＳ）功能。结果发现，偏头痛患者站立位中频段积分较对照组显著降低（Ｐ＜０．００１），表明其交感功能低下，且随着疼痛程度的增加及病程的延长，其交感功能低下的程度亦越重。本文还初步探讨了其机理及临床应用意义。     

Sevoflurane anesthesia decreases cardiac vagal activity and heart rate variability

We evaluated cardiac vagal activity during sevoflurane anesthesia in neurosurgical patients. Heart rate variability was determined by power spectral analysis and entropy with the patient awake and during sevoflurane anesthesia. High frequency power (0.15–0.50 Hz) and heart rate entropy decreased during sevoflurane and these effects were significantly correlated (r = 0.71 ± 0.12, P < 0.05). The results confirm that cardiac vagal activity was the primary determinant of heart rate variability, which was attenuated by sevoflurane.     

Heart rate variability in type 2 spinocerebellar ataxia

Montes‐Brown J, Sánchez‐Cruz G, García AM, Báez ME, Velázquez‐Pérez L. Heart rate variability in type 2 spinocerebellar ataxia.
Acta Neurol Scand: 2010: 122: 329–335.
© 2010 The Authors Journal compilation © 2010 Blackwell Munksgaard. Objectives – To explore cardiovascular autonomic regulation in Spinocerebellar ataxia type 2 (SCA2) patients, using heart rate variability (HRV) analysis and neurophysiologic autonomic reflex tests, and determine relations and causal related factors of dysautonomia in SCA2. Materials and methods – Heart rate variability indices for 5 min series of RR intervals were analyzed in 97 SCA2 patients, assessed quantitatively for somatic and autonomic nervous system complaints applying the International Cooperative Ataxia Rating Scale and Scales for Outcomes in Parkinson’s disease (SCOPA‐AUT), respectively. Autonomic testing included: resting control, standing, Valsalva maneuver and deep breathing. Results – Mean RR, long‐ and short‐term variability indices and spectral density power (LF, HF) indices were lower in the patients group, whereas LF/HF ratio and LF (nu) were higher. Highly differences between groups were observed for seven diagnostic autonomic test indices. Significant correlations were found between different clinical and demographic indices and between clinical indices and some HRV indices. Conclusions – We confirm the presence of cardiovascular autonomic dysfunction in a large group of SCA2 patients.     

Autonomic function in narcolepsy: power spectrum analysis of heart rate variability

Ten narcoleptic patients that had never been treated previously and ten healthy volunteers of comparable age underwent 48-h polygraphic recording to assess the effects of wakefulness and sleep on beat-to-beat heart rate variability by means of power spectrum analysis. The study revealed decreased power in the low frequencies (LF) during sleep (whereby an increase of the power in this band is associated with sympathetic activation) compared with wakefulness, with minimal values during stage 3–4 non-REM sleep and higher levels during REM sleep, both in patients and controls. Significantly reduced power in high frequencies (HF; mainly expression of parasympathetic control) and a significantly increased LF/HF ratio during wakefulness before sleep in narcoleptics compared with controls were found. Our study excludes a primary disturbance of cardiac autonomic nervous system in narcoleptics but suggests an altered circadian autonomic function in these patients. Received: 23 May 1996 Received in revised form: 3 December 1996 Accepted: 17 January 1997     

Threat-induced autonomic dysregulation in panic disorder evidenced by heart rate variability measures

Objective

The objective was to compare autonomic response to threatening stimuli between patients with panic disorder (PD) and healthy volunteers by using 5-min recordings of heart rate variability (HRV).

Methods

Twenty-seven patients with PD and 20 healthy controls were recruited. The first 5-min measurement of HRV was conducted at resting state. HRV measurement during threatening stimuli was conducted while participants were viewing 15 threatening pictures. Spectral analyses measures included high-frequency (HF; 0.15–0.4 HZ) component, low-frequency (LF; 0.04–0.15 Hz) component and LF/HF ratio.

Results

There was no significant HRV difference between the two groups at the resting state. During threatening stimuli, the PD group had significantly higher LF power and LF/HF ratio and significantly lower HF power than the healthy controls (for all, P< .01). A two-way analysis of variance was employed to determine the effect of group (patient and control) and condition (threatening and resting) on all three HRV measures. The analysis showed a significant main effect of group (F= 12.21; P< .01), condition (F= 14.21; P< .001) and interaction effect between group and condition (F= 4.83; P< .05) on LF/HF ratio.

Conclusions

The findings from the present study suggest that patients with PD exhibit a sympathetic predominance when faced with threatening stimuli compared with normal control subjects.     

Decreased chaos of heart rate time series in children of patients with panic disorder

This study examined the differences of heart rate variability measures between children of parents with panic disorder and children of healthy controls using linear as well as nonlinear techniques. Supine and standing heart rate variability indices were measured in all children using power spectral analysis and a measure of chaos, the largest Lyapunov exponent (LLE) of heart rate time series. No significant differences emerged between the children of panic disorder parents and children of normal controls on any of the spectral heart rate variability measures. However, children of patients with panic disorder had significantly lower LLE of heart rate time series in supine posture, suggesting a relative decrease of cardiac vagal function in this group of children. This suggests a possible heritable effect of certain measures of heart rate variability, as previous studies showed decreased heart rate variability in patients with panic disorder using spectral as well as nonlinear techniques. Recent evidence also suggests that some of these nonlinear measures are superior or of additional value to the traditional time and frequency domain measures of heart rate variability to predict serious ventricular arrhythmias and sudden death.     

Autonomic dysfunction in presymptomatic spinocerebellar ataxia type-2

Montes‐Brown J, Machado A, Estévez M, Carricarte C, Velázquez‐Pérez L. Autonomic dysfunction in presymptomatic spinocerebellar ataxia type‐2.
Acta Neurol Scand: 2012: 125: 24–29.
© 2011 John Wiley & Sons A/S. Objectives – To explore and quantify possible abnormalities in the autonomic cardiovascular regulation in presymptomatic stage of type 2 spinocerebellar ataxia (PS‐SCA2). Materials & methods – Heart rate variability (HRV) for 5‐min series of RR intervals was analyzed in 48 PS‐SCA2. Autonomic testing included resting recording, standing, Valsalva maneuver, and deep breathing. The results were compared with a group of sex‐ and age‐matched controls. Results – Time‐and‐frequency domain HRV indices were significantly different between PS‐SCA2 and control groups. Using two standard diagnostic procedures were identified 4 (8.33%) subjects with severe and 8 (16.66%) subjects with early cardiac autonomic neuropathy in PS‐SCA2. CAG index significantly correlated with age (?0.35) and HR (0.31). Conclusions – Our results confirm the presence of cardiovascular autonomic dysfunction in PS‐SCA2 subjects.     

Decreased heart rate variability in amyotrophic lateral sclerosis

Autoregressive spectral analysis of heart rate variability (HRV) was performed in 29 patients with amyotrophic lateral sclerosis (ALS) and 33 age-matched healthy subjects to evaluate the involvement of the autonomic nervous system. HRV analysis provides a means to recognize low (LF) and high (HF) frequency components, respectively mediated by sympathetic and parasympathetic heart control. An increase in the mean heart rate at rest (P < 0.001), a decrease in standard deviation of R-R interval as well as in PNN50 (P < 0.001), and an increase in the LF/HF component ratio (P < 0.01) were found in the ALS patients, indicating a vagal–sympathetic imbalance. These alterations were not related to the clinical features and to the duration of the disease. Our results suggest a subclinical involvement of the autonomic nervous system in ALS, particularly affecting parasympathetic cardiovascular control. © John Wiley & Sons, Inc.     

Dysfunctional baroreflex regulation of sympathetic nerve activity in remitted patients with panic disorder

Background Many researchers have studied the abnormalities of autonomic nervous system (ANS) such as decreased heart rate variability, which is a risk factor for sudden cardiac death, in patients with panic disorder (PD). However, no consistent abnormality has been uncovered to date. One of the reasons for this controversy may be due to the fact that most of these conventional studies have analyzed each physiological variable independent of other indices. We examined the ANS in PD patients using a new method which can more directly investigate the function of the baroreflex by examining the relation between the blood pressure (BP) and heart rate (HR). Methods During rest and audiovisual stimulation (AS) as mental stress such as being exposed to video imaginary of experiences such as driving motor vehicles, cardiovascular parameters, HR and BP were consecutively measured in 13 remitted PD patients and twenty aged and gender–matched normal controls (NC). In this study, to assess the cardiovascular ANS function (baroreflex) in PD we used the power spectrum analysis as usual and the mean of lag time (τ) between the Mayer wave components, which was closely related to sympathetic nerve activity of vasomotor, of HR and BP variability as a new trial. Results The PD patients and NC did not differ with regard to the power spectrum analysis of the heart rate. We found that τ in the PD group was significantly shorter than that in the NC both before and after AS, especially before. Conclusions These findings suggest that remitted PD patients may have a dysfunctional baroreflex regulation of sympathetic nerve activity.     

Autonomic control of heart rate variability in vasovagal syncope: A study of the nighttime period in 24-hour recordings

Patients experiencing vasovagal syncope have been claimed to show reduced vagal tone over 24-hour electrocardiography recordings. Assessment of sympathovagal balance in the absence of external stimuli,ie, nighttime electrocardiography monitoring, might help to clarify if increased sympathetic activity is present in these patients. Heart rate variability was examined at nighttime in 40 patients with recurrent episodes of vasovagal syncope within the last 2 years (22 men; mean age, 37 years) and 20 comparable healthy volunteers. Time domain parameters (pNN50 [proportion of successive RR intervals difference > 50 ms in %] and rMSSD [root-mean-square successive difference of RR intervals in ms]), indexes of vagal tone, and frequency domain parameters, expressing the overall heart rate variability, vagal (high frequency [HF]) and sympathetic (low frequency [LF]) activity, and autonomic balance (LF/HF ratio) were compared between groups by Mann-Whitney test. Significant (p<0.05) reduction of heart rate variability and vagal tone (pNN50 and rMSSD) were found for patients with vasovagal syncope, together with increased sympathetic activity (increased LF/HF ratio). These findings could open new insights in the pathogenesis of vasovagal syncope because of the shift of the autonomic balance toward sympathetic activation near the syncopal episode.     

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; are 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 , 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 ) 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 (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 , 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.     

Heart rate variability and autonomic function tests in HIV positive individuals in India

Supine heart rate variability (HRV) and autonomic tests were carried to determine whether autonomic activity was affected in HIV positive patients. The pressor response following handgrip and cold pressor test was blunted in HIV+ patients, and the degree of dysfunction correlated with CD4 cell counts. The extent of autonomic impairment was mild and subclinical.     

Impaired heart rate variability in euthymic bipolar patients

Background:  Power spectral analysis of heart rate variability (HRV) has recently been shown to be a reliable non-invasive test for quantitative assessment of the central sympathovagal interaction that modulates cardiovascular autonomic function.
Methods:  We studied 39 euthymic bipolar patients and 39 controls, matched for age and sex. A high-resolution electrocardiogram was obtained during complete rest. Spectral analysis of R–R intervals was performed by the fast Fourier transform algorithm.
Results:  Euthymic bipolar patients at rest are characterized by markedly low HRV, independent of specific drug treatments.
Conclusion:  While these results of autonomic stability in euthymic bipolar patients are counter-intuitive, the findings may be important in understanding pathophysiology of bipolar affective illness.     

Effect of a novel environment on resting heart rate in panic disorder

Several studies have found higher resting heart rate among patients with panic disorder compared to healthy controls, whereas others have found no differences. It has been suggested that these differences may result from anticipatory anxiety. The purpose of this study was to compare the resting heart rates of 10 patients with panic disorder, 11 patients with social phobia, and 13 healthy controls during two consecutive visits to our laboratory. There were no significant differences between groups on resting heart rate on either day. However, patients with panic disorder did have significantly higher resting heart rates on day 1 versus day 2. This suggests that patients with panic disorder may experience greater anticipatory anxiety which is manifested in a higher resting heart rate than patients with social phobia or healthy controls. Implications for previous and future reports on resting heart rate measures in patients with panic disorder are discussed. Depression and Anxiety 8:24–28, 1998. © 1998 Wiley-Liss, Inc.     

Effect of chronic epilepsy on heart rate variability: a case-control study

BACKGROUND; Dysfunction of the autonomic cardiac regulation is thought to be related to higher mortality in epileptic patients. OBJECTIVE: We tried to study changes in sympathetic and parasympathetic activities in patients with chronic epilepsy and repetitive generalized tonic-clonic (GTC) seizures. DESIGN, TIME AND SETTING: A case-control study was conducted at the Buddhist Tzu Chi General Hospital between July 2006 and May 2009.MATERIALS: The study included 15 male and 15 female patients (mean age ± S.D.: 33.40 ± 12.64 years) who had chronic epilepsy and repetitive GTC seizures and 15 male and 15 female healthy control subjects (age: 32.20 ± 9.53 years). METHODS: Lead I electrocardiograms were taken in 5 minutes during an interictal period in the daytime among the epilepsy and control gourps. Frequency-domain analysis of heart rate variability was performed with fast Fourier Transformation and the data were subsequently converted to heart rate interval, high frequency (HF; 0.15-0.45 Hz) power, low frequency (LF; 0.04-0.15 Hz) power, and LF/(HF+LF) expressed in normalized units (LF%). Differences in the data between the groups were compared using Student’s t-test.MAIN OUTCOME MEASURES: The LF component contributed from both sympathetic and parasympathetic divisions. The HF component represented vagal (parasympathetic) regulation and the LF% was considered to mirror sympathetic regulation. RESULTS: All 30 patients have idiopathic or cryptogenic epilepsy lasting 19.01  10.22 years. All patients had GTC seizures with or without other types of seizures, but 16 of them had GTC seizures only. There was no significant between-group difference in age, height, weight and body mass index. The epilepsy group had a significantly lower mean heart rate interval, a significantly higher LF%, and a significantly lower high frequency power. CONCLUSION: Patients with chronic epilepsy have faster heart rates during interictal periods and it may be attributed to higher sympathetic and lower parasympathetic activity.