Sympathovagal Balance Prior to Onset of Repetitive Monomorphic Idiopathic Ventricular Tachycardia

Repetitive monomorphic idiopathic (RMI) ventricular tachycardia (VT) occurs typically in patients without structural heart disease, originates in most cases from the right ventricular outflow tract, and can often be induced by exercise or isoproterenol. This study analyzed the dynamic changes in autonomic tone immediately before the spontaneous onset of RMIVT using frequency-domain heart rate variability (HRV) indices. We analyzed the ambulatory electrocardiographic recordings from 6 men and 8 women (mean age: 43 ± 18 years; mean number of VT runs per day: 134 ± 213; mean VT rate: 194 ± 40 bpm; median VT run length: 4 cycles) with RMIVT. A total of 36 clusters of nonsustained episodes of RMIVT preceded by ≥1 hour of sinus rhythm without VT were analyzed (25 minutes before the onset of RMIVT divided into five 5-minute periods; 8 minutes before onset of RIMVT divided into eight 1-minute periods). During 25 minutes preceding the onset of VT, the mean RR interval decreased from 767 ± 118 to 723 ± 105 ms (P = 0.015) and the low-frequency (LF)/high-frequency (HF) ratio increased from 2.24 ± 0.79 to 2.49 ± 1.0 (P = 0.03). During the 8 minutes before VT onset, the mean RR interval decreased from 745 ± 118 to 718 ± 102 ms (P = 0.001) and the LF components increased from 205 ± 72 to 253 ± 113 ms (P = 0.014). No change in HF components was observed during the 25 or 8 minutes periods preceding the RMIVT onset. The changes in HRV indices suggest a strong time-dependent primary activation of sympathetic tone prior to the occurrence of RMIVT. Withdrawal of vagal tone does not appear essential to the initiation of RMIVT clusters.     

Heart Rate Variability in Patients with Familial Amyloid Polyneuropathy

The purpose of this study was to evaluate heart rate variability (HRV) in patients with familial amyloid polyneuropathy (FAP) using the time- and frequency-domain analysis. The study population consisted of 19 patients with FAP, and 19 age and sex matched normal volunteers. The 24-hour Holter recordings of all subjects in sinus rhythm and off medication were analyzed. Five time-domain indices of HRV were computed. The frequency component of HRV was calculated by fast Fourier transform analysis of the RR intervals. The power spectrum of the low frequency (LF) between 0.04–0.15 Hz and high frequency (HF) between 0.15–0.40 Hz and the LF/HF ratio was calculated. Global measures of HRV including the standard deviation of the mean of RR intervals (SDNN) and the standard deviation of 5-minute mean RR intervals (SDANN) were decreased in patients with FAP. Specific vagal influences on HRV including the proportion of RR intervals more than 50 milliseconds different (pNN50) and the HF power on spectral analysis were less in patients with FAP. LF power and LF/HF ratio were more decreased in patients with FAP at the advanced stage than at the early stage. In conclusion, HRV was significantly decreased in patients with FAP at the early stage, and sympathetic activity was more decreased in patients at the advanced stage. These findings suggest that the decrease of the HRV is an indicator of this disease and the power spectral analysis of the HRV is beneficial in assessing the severity of the autonomic dysfunction.     

The efficiency of 10-second resting heart rate for the evaluation of short-term heart rate variability indices

Background: High values of resting heart rate were found to be correlated with adverse outcomes in various patient groups. Heart rate variability (HRV) is a reliable technique in determining autonomic nervous system function. Our aim was to evaluate whether a 10‐second resting heart rate obtained from a resting electrocardiogram (ECG), could be used as a reliable evaluation of short‐term HRV. Methods: Seventy‐nine healthy volunteers were included in the study. All participants underwent a 10‐second ECG, and 5‐minute HRV measurement under strict criteria. Results: A significantly negative correlation was found between resting heart rate and 5‐minute max‐RR, min‐RR, standard deviation of normal RR intervals (SDNN), root mean square of successive differences of RR intervals (RMSSD), HRV triangular index, number of intervals differing by 50 milliseconds from the preceding interval (NN50), pNN50, standard deviation of the points perpendicular to the line of identity (SD1), standard deviation along the line of identity (SD2), and high frequency spectral component (HF). A significant positive correlation was found between resting heart rate and a 5‐minute low frequency spectral component (LF) and LF/HF ratio. Specifically, max‐RR and min‐RR were found to have the best correlation with resting heart rate. Conclusions: Resting heart rate obtained from a 10‐second ECG can be used for crude estimation of all HRV results in healthy individuals who do not take medications, with variable efficacy depending on the measured parameter. Resting heart rate was especially efficient in predicting max‐RR and min‐RR. Further research should focus on assessing the reliability of a resting heart rate for HRV evaluation, in patients with autonomic dysfunction and high‐risk cardiac patients. (PACE 2011; 34:1498–1502)     

Relation of heart rate variability to serum levels of C-reactive protein,interleukin 6, and 10 in patients with sepsis and septic shock

Purpose

The aim of the study was to investigate possible associations between different heart rate variability (HRV) indices and various biomarkers of inflammation in 45 septic patients.

Materials and Methods

We daily assessed HRV in the time domain (SD of RR intervals [SDNN]), frequency domain (low [LF], high frequency [HF], LF/HF as an indicator of sympathovagal balance); the 2 values of SD (SD1, SD2) from the Poincaré plot; and measured C-reactive protein, interleukin 6, and interleukin 10 serum levels in patients with sepsis and mean Sequential Organ Failure Assessment score (SOFA) 10 or lower (n = 25) and septic shock (SOFA > 10, n = 20) for 6 days.

Results

C-reactive protein exhibited significant negative correlations with LF (r = −0.78), LF/HF (r = −0.61), and SDNN (r = −0.79) and positive correlations with HF (r = 0.80) and SD1/SD2 (r = 0.66), whereas interleukin 10 was positively correlated with HF (r = 0.71) and negatively with LF (r = −0.89) and LF/HF (r = −0.66) in septic shock patients (P < .05 for all comparisons). Standard deviation of RR intervals and HF proved to be independent predictors of the severity of disease (β slope [B] = −1.091; P = .013; 95% confidence interval [CI], −1.43 to −0.74, and B = 0.78; P = .022; 95% CI, 0.21-1.35, respectively).

Conclusions

Our data suggest that low HRV and sympathovagal balance during septic shock are associated with both an increased hyperinflammatory and antiinflammatory response.     

Correlations between frequency-domain HRV indices and lagged Poincaré plot width in healthy and diabetic subjects

The conventional Poincaré plot for heart rate variability (HRV) analysis is a scatterplot of successive (lag 1) pairs of RR intervals (intervals between heartbeats), and its width (SD1) is considered a measure of short-term variability. It has been shown that SD1 correlates better with HF than with LF (high- and low-frequency bands of the spectrum, respectively). Our aim was to assess how these correlations were affected when SD1 was obtained for longer lags. 10 min ECGs were used to construct Poincaré plots with lags of 1-10 heartbeats in two groups of subjects, one with normal HRV and the other with impaired HRV (control and diabetic groups respectively, N = 15 each). SD1 was quantified for these subjects and HRV spectral indices were estimated. The diabetic group had lower LF, HF and SD1 than the control group (p < 0.05). In both groups, SD1 tended to increase as the lag increased. In the control group, SD1 for lags 1 and 2 was highly correlated with HF (r(s) > 0.9), while SD1 for lags 4 correlated better with LF (r(s) 0.9) than with HF (0.65 相似文献   

Association between Cardiac Autonomic Function and Coping Style in Healthy Subjects

The link between personality and cardiac function is insufficiently characterized. We postulated that in a healthy population, cardiac autonomic function is linked to coping style. In 276 healthy volunteers, between the ages of 18 and 71, the Utrecht Coping List was used to evaluate different coping strategies. Trait anxiety was scored by the Spielberger State Trait Anxiety Inventory. A 24-hour Holter recording was used to calculate heart rate variability (HRV). For HRV parameters and coping mechanisms this study demonstrated gender-specific differences and correlations with age. In men (n = 141) higher active coping was associated with less global autonomic activity or SDANN (r_s=−0.27, P < 0.001). This relationship was most prevalent in young (18–30 years) men (r_s=−0.45, P < 0.005). Higher expression of negative emotions or anger was related to both higher vagal (r_s= 0.23 for rMSSD, P < 0.01) tone and higher LF power (r_s= 0.23, P < 0.01). In young men expression of negative emotions or anger was associated with LF power (r_s= 0.37, P < 0.01) and in middle-aged (31–50 years) men with vagal tone (r_s= 0.43 for rMSSD, P < 0.005) and heart rate (r_s=−0.41, P < 0.005). Higher comforting ideas was related to higher LF power (r_s= 0.23 for LF power, P < 0.005), and this especially in middle-aged men (r_s= 0.37, P < 0.01). In women (n = 135), no significant correlations between coping style and HRV indices were found. We conclude that in normal individuals, at least in men, our findings suggest a relationship between coping style and cardiac autonomic function.     

Continuous Heart Rate Variability Monitoring Through Complex Demodulation Implemented with the Fast Fourier Transform and Its Inverse

A new method for the analysis of 24-hour heart rate variability (HBV) using complex demodulation (CDM) implemented with the fast Fourier transform (FFT) and its inverse is described. In a control group with palpitations and dizzy spells (n = 30, 47.2 ± 16.7years) the relationship between HRV parameters and subject age was investigated, CDM was used to obtain the amplitude and frequency of the low frequency (LF) and high frequency (HF) oscillations for 8 diurnal hours and 4 nocturnal hours. Differences between the two periods were seen in the LF/HF ratio (2.2 ± 0.6 vs 1.5 ± 0.6; P <0.0001), HF amplitudes (12 ± 6 vs 17 ± 7 normalized units, P < 0.05). and in the mean frequency of the LF oscillations (0.078 ± 0.008 vs 0.073 ± 0.007 Hz, P < 0.01). During the daytime, age was inversely correlated to HF amplitude (r =−0.60), directly correlated to HF mean central frequency (r = 0.40), inversely correlated to LF amplitude (r =−0.55), and likewise inversely correlated to LF mean central frequency (r=−0.74, P < 0.001). At night, age was only inversely correlated to HF amplitude andtoLF mean central frequency.Conclusions: Continuous HRV monitoring through COM implemented with the FFT and its inverse differentiates the periods of diurnal activity and nocturnal rest as an expression of two different activity states of the autonomic nervous system. It allows nonstationary analysis, and separately provides mean and instantaneous oscillation amplitude and frequency. Subject age is not equally related to mean amplitude and frequency of a given oscillation.     

Role of Sympathovagal Balance in the Initiation of Idiopathic Ventricular Tachycardia Originating from Right Ventricular Outflow Tract

VT originating from the right ventricular outflow tract (RVOT) is prone to occur when sympathetic nervous activity is increased. β-Blockade is, therefore, effective in suppressing this VT. The purpose of this study was to determine the role of sympathovagal balance assessed by heart rate variability (HRV) in the spontaneous initiation of repetitive premature ventricular contractions (PVCs) and VT (five or more consecutive PVCs) arising from RVOT in seven patients without structural heart diseases. Frequency-domain measures of HRV were determined by analyzing 24-hour Holter electrocardiographic recording with the maximum entropy method over α 1,280-second period immediately before the onset of 35 single PVCs, 26 episodes of 2-4 consecutive PVCs, and 21 episodes of VT. High frequency component (HF: 0.15–0.40 Hz) was used as an index of parasympathetic activity, and the ratio of low frequency component (LF: 0.04–0.15 Hz) to HF (LF/HF ratio), as an index of sympathovagal balance. NN50(%), a time-domain variable of parasympathetic activity, was also determined. Mean RR interval and any measures of HRV did not change significantly before single PVCs. Mean RR interval shortened and HF decreased prior to repetitive PVCs and VT. The LF/HF ratio, however, increased only before the onset of VT. NN50(%) tended to decrease before repetitive PVCs and decreased significantly before VT. With propranolol (30–60 mg/day), frequency of repetitive PVCs was suppressed from 2,048 ± 1,201 to 746 ± 658/day and VT was totally abolished, but frequency of single PVCs did not change significantly. In conclusion, sympathetic predominance plays an important role in the initiation of repetitive PVCs and VT originating from RVOT in patients without structural heart diseases.     

Variations of HRV and skin conductance reveal the influence of CV4 and Rib Raising techniques on autonomic balance: A randomized controlled clinical trial

IntroductionThe aim of the present study was to evaluate whether Fourth Ventricle Compression Technique (CV4) and Rib Raising (RR) osteopathic techniques influence Autonomic Nervous System (ANS) activity, as measured by Heart Rate Variability (HRV) and Skin Conductance (SC).MethodA randomized-controlled clinical trial has been performed from June 2010 to January 2011. 32 healthy adults (33.9 ± 14 years, and 72% female) were selected. Subjects were randomized in three groups: CV4 group, RR group and Placebo group. Each subject of each group underwent respective technique only once. HRV and SC were continuously recorded during the session. All data analysis was performed using SPSS statistical software (version 21.0) and the significance level was considered at p ≤ 0.05.ResultsRR technique intra-group subject analysis showed a significant decrease in LF/HF ratio (F = 25.18; p < 0.001), a statistically significant decrease of LF (F = 27.09; p < 0.001), and increase of HF, both at the end of treatment (F = 27.09; p < 0.001). CV4 technique intra-group subject analysis showed a significant reduction of the LF/HF ratio (F = 81.15; p < 0.001), a significant decrease in LF (F = 38.29; p < 0.001) and a significant increase of HF, at the end of treatment (F = 38.28; p < 0.001). Between-group analysis showed only a significant difference in LF/HF ratio between CV4 and PL groups (F = 3.44; p = 0.042).DiscussionOur results suggest that the application of CV4 and RR techniques favors a shift in the autonomic balance towards a parasympathetic predominant state. Thus, their use within OMT protocol, as holistic approach, might improve the outcome of the treatment of clinical neuro-vegetative conditions.     

Frequency-domain analysis of heart rate variability during positive and negative head-up tilt test: importance of age

The study of autonomic behavior during a head-up tilt test (HUT) has been deemed important to understand the loss of consciousness mechanism. Though HRV in patients with HUT(+) and HUT(-) has been compared, few trials emphasized the importance of age. HRV in frequency domain was analyzed based on 5-minute samples in the supine position, and between 5 and 10 minutes during early tilt test (R1) in 102 patients with one or more episodes of syncope (mean age 44.3 +/- 20.8, range 15-85 years, 55 women). Two subgroups were selected afterwards: (1) young patients between 15 and 35 years of age (41 patients) and (2) elderly patients aged 60 or more (36 patients). The following parameters were taken into account: the sum of low (LF) and high frequency (HF) (LF and HF in absolute values and in normalized units), the LF/HF ratio (L/H ratio), and the percentage of change between baseline and R1 values. The HRV behavior in young and elderly patients with positive and negative HUT was established. We then analyzed the correlation between HRV and age and HUT outcome. A multiple regression analysis encompassing age, HUT outcome, gender, and number of syncope episodes was performed. In young patients, the LF and HF areas and the L/H ratio changed significantly between baseline and R1. The L/H ratio increases from baseline to R1. Conversely, these differences were not significant in the elderly. No differences between HUT(+) and HUT(-) within the same age group were observed. Age related significantly to practically all HRV parameters analyzed, whereas the tilt test outcome correlates poorly with HF normalized units and LF normalized units during R1, and the L/H ratio changes between baseline and R1. By means of a multivariate analysis, only age shows a significant correlation with the HRV values. Despite an all age triggering of vasovagal syncope during HUT, the young and elderly patients' autonomic behavior differs. The young considerably increase their sympathovagal balance during HUT, whereas the elderly have a mitigated autonomic response. No significant differences were observed during the first minutes of the test between those with a HUT(+) and those with a HUT(-) within the same age group. Age, and not the HUT response, is the major determinant of the autonomic behavior during early HUT.     

Autonomic nervous functions in fetal type Minamata disease patients: assessment of heart rate variability

In order to assess the cardiovascular autonomic nervous functions in patients with fetal type Minamata disease (FMD), we investigated blood pressure (BP), and conducted time and frequency domain analysis of heart rate variability (HRV). Subjects were 9 patients in Meisuien recognized as FMD, and 13 healthy age matched control subjects. HRV and BP were assessed after subjects rested in a supine position for 10 minutes. Electrocardiographic (ECG) data were collected for 3 minutes during natural breathing. Time domain analysis (the average of R-R intervals [Mean RR], standard deviation of R-R intervals [SD RR], coefficient of variation [CV]), and frequency domain analysis by fast Fourier transformation (FFT) (power of low frequency [LF] and high frequency [HF] component, expressed in normalized units[nu]) were then conducted. In the time domain analysis, the mean RR of the FMD group was significantly lower than that of the control group. Neither SD RR nor CV showed significant differences between the two groups, but both tended to be lower in the FMD group. In the frequency domain analysis, the HF component of the FMD group was significantly lower than that of the control group. Pulse pressure (PP) was significantly lower in the FMD subjects. These findings suggest that parasympathetic nervous dysfunction might exist in FMD patients, who were exposed to high doses of methylmercury (MeHg) during the prenatal period. Decrease of PP might be due to degenerative changes of blood vessels driven by exposure to high doses of MeHg.     

Heart Rate Variability in Emergency Department Patients with Sepsis

OBJECTIVE: To test the hypothesis that heart rate variability (HRV) can provide an early indication of illness severity among patients presenting to the emergency department (ED) with sepsis. METHODS: The authors enrolled a convenience sample of 15 ED patients meeting the American College of Chest Physicians/Society of Critical Care Medicine criteria for sepsis. Each patient had continuous Holter monitoring performed in the ED. Acute Physiology and Chronic Health II (APACHE II) and Sequential Organ Failure (SOFA) scores were calculated for the day of presentation. Holter tapes obtained in the ED were analyzed off-line to calculate HRV variables for the 5-minute segment with the least artifact and non-sinus beats. These variables were correlated with APACHE II and SOFA scores. RESULTS: LFnu (normalized low-frequency power), an assessment of the relative sympathetic contribution to overall HRV, was correlated with increased illness severity as calculated using APACHE II (r = -0.67, r(2) = 0.43) and SOFA (r = -0.80, r(2) = 0.64) scores. LF/HF ratio (low-frequency/high-frequency ratio), a measure of sympathovagal balance, was correlated with the SOFA score [r = -0.54 (95% CI = -0.83 to -0.01), r(2) = 0.29]. All five patients who required critical care monitoring or ventilatory support or who died during the first 5 days of their hospitalization had LFnu values below 0.5 and LF/HF ratios less than 1.0. None of the patients with measurements greater than these threshold values died or required these interventions during the five days following admission. CONCLUSIONS: A single variable, LFnu, which reflects sympathetic modulation of heart rate, accounted for 40-60% of the variance in illness severity scores among patients presenting to the ED with sepsis. HRV, as reflected in LFnu and the LF/HF ratio and measured with a single brief (5-minute) period of monitoring while in the ED, may provide the emergency physician with a readily available, noninvasive, early marker of illness severity. The threshold effect of LFnu and LF/HF in the prediction of early clinical deterioration was an unexpected finding and should be regarded as hypothesis-generating, pending further study.     

Heart rate variability during sleep and sleep apnoea in a population based study of 387 women

Increased sympathetic activity during sleep has been suggested as a link between obstructive sleep apnoea syndrome and cardiovascular disease. Heart rate variability (HRV) is a measure of autonomic effect on the heart. Different parameters have been associated with sympathetic and parasympathetic activity. We have studied HRV in different sleep stages and related the HRV‐pattern to sleep apnoea in a population‐based sample of 387 women. We investigated the HRV‐parameters standard deviation of all R‐R intervals (SDNN), root of the averaged square of successive differences (RMSSD), low frequency component (LF), high frequency component (HF), ratio of low frequency component to high frequency component LF/HF and VSAI [variation in sympathetic activity between rapid eye movement (REM) and slow wave sleep, defined as LF_REM?LF_SWS]. The HRV‐parameters were compared with the results of a full‐night polysomnography. Hourly incidence of obstructive episodes was used for classifying the subjects into four apnoea‐hypopnoea index (AHI)‐groups (<5, ≥5 and <15, 15–30 and >30 events). Individual sleep stages were analysed by pooling all recordings. Women with high AHI had higher heart rate and LF/HF ratio. In subjects with AHI >30, LF/HF ratio however dropped to same level as with AHI <5. Subjects with high AHI had low VSAI. Levels of SDNN, LF and LF/HF ratio during REM and light sleep were similar to wakefulness. In slow wave sleep the parameters decreased. In conclusion, moderately increased prevalence of obstructive apnoeas was associated with signs of higher sympathetic activity. High AHI was however associated with a HRV‐pattern suggestive of depressed sympathetic drive and lowered ability to increase it during REM.     

Autonomic involvement in idiopathic premature ventricular contractions

Objective

To investigate autonomic involvement in different types of idiopathic premature ventricular contractions (PVCs) grouped by heart rate (HR) dependency.

Methods

One hundred and sixty PVC patients and 31 controls were enrolled. Holter ECG was used to evaluate PVC occurrence, and spectral analysis of heart rate variability (HRV) was calculated to represent cardiac autonomic control. PVCs were divided into fast rate-dependent (F-PVC), slow rate-dependent (S-PVC), and HR-independent PVC (I-PVC) based on the relationship between hourly PVC density and hourly HR. HRV among different types of PVCs were compared, and the association between PVC density with HR and HRV were analyzed. Furthermore, autonomic changes assessed by consecutive 5-min HRV in 30 min before PVC episodes were investigated.

Results

In 160 subjects, there were 73 F-PVC, 56 S-PVC, and 31 I-PVC. Hourly PVC density was positively associated with sympathetic indice (LF/HF) and negatively related to vagal indices (HF and HFnu) in F-PVC, and this trend was reversed in S-PVC. During 30 min before PVC onset, RR interval and HFnu decreased significantly with LF/HF showing an increasing trend in F-PVC, while in S-PVC both RR interval and HF increased significantly. It was noted that those changes were most evident during the last 5 min before PVC onset. In addition, PVC density in F-PVC was significantly decreased by β-blocker treatment.

Conclusions

HR dependency reflected autonomic modulation of idiopathic PVCs. F-PVC and S-PVC might be facilitated by sympathetic activation and vagal activation, respectively. HR dependency and the related autonomic mechanisms should be considered when treating idiopathic PVCs.     

Heart rate variability measures: a fresh look at reliability

Despite its extensive use in physiological and clinical research, the analysis of HRV (heart rate variability) is still poorly supported by rigorous reliability studies. The main aim of the present study was to perform an in-depth assessment of absolute and relative reliability of standard indexes of HRV from short-term laboratory recordings. In 39 healthy subjects [mean age (min-max): 38 (26-56) years; 18 men and 21 women] we recorded 5 min of supine ECG during spontaneous and paced (15 breaths/min) breathing. The test was repeated on the next day under the same conditions. From the RR intervals we computed standard indexes of HRV: SDNN (S.D. of RR interval values), RMSSD (root-mean-square of successive RR interval differences), LF (low frequency) and HF (high frequency) power (absolute and normalized units) and LF/HF. Absolute reliability was assessed by 95% limits of random variation; relative reliability was assessed by the ICC (intraclass correlation coefficient). The sample size needed to detect a mean difference > or =30% of the between-subject S.D. was also estimated. Although there was no significant mean change between the two tests, we found that in individual subjects the second measurement was as high/low as 1.9/0.5 times (SDNN, best case) and 3.5/0.3 times (LF/HF, worst case) the first measurement, due to pure random variation. For most parameters the ICC was >0.8 (range 0.65-0.88). The estimated sample size ranged from 24-98 subjects. Reliability indexes tended to improve during paced breathing. We conclude that short-term HRV parameters are subject to large day-to-day random variations. Random error, however, represents a limited part of the between-subject variability; therefore observed differences between individuals mostly reflect differences in the subjects' error-free value rather than random error. Overall, paced breathing improves reliability.     

Postresuscitation autonomic nervous modulation after cardiac arrest resembles that of severe sepsis

Introduction

This study explored whether post-resuscitation status resembles severe sepsis in terms of autonomic nervous modulation by using heart rate variability (HRV) analysis.

Methods

Successfully resuscitated nontraumatic out-of-hospital cardiac arrest (OHCA) adult patients in an emergency department were prospectively enrolled as the study group. Age- and sex-matched patients with severe sepsis with and without mechanical ventilation were included as positive controls, while sepsis patients and healthy volunteers were included as negative controls. The HRV measures obtained from 10-minute electrocardiogram were compared among 5 groups of subjects.

Results

Sixty-four successfully resuscitated OHCA patients were studied. There were no significant differences in all HRV measures (standard deviation of R-R intervals [SD_RR], coefficient of variation of R-R intervals [CV_RR], total power [TP], very-low-frequency component [VLF], low-frequency component [LF], high-frequency component [HF], normalized LF [LF%], normalized HF [HF%], and LF/HF) among the successfully resuscitated OHCA patients and severe sepsis patients with and without mechanical ventilation. Also, no significant differences in all HRV measures were found between nonsurvivors of OHCA group and nonsurvivors of severe sepsis group. In the nonsurvivors of OHCA group and severe sepsis group, the LF% and LF/HF were significantly lower, whereas the HF and HF% were significantly higher, as compared with the survivors of these 2 groups.

Conclusions

The autonomic nervous modulation in the initial phase of OHCA patients resembles that of severe sepsis in that both groups of patients have decreased global HRV (TP, SD_RR, and CV_RR), sympathovagal balance (LF% and LF/HF), and renin-angiotensin-aldosterone modulation (VLF), as compared to healthy subjects.     

Changes in heart-rate variability of survivors of nasopharyngeal cancer during Tai Chi Qigong practice

[Purpose] To explore the changes in heart-rate variability (HRV) of survivors of nasopharyngeal cancer (NPC) before, during, and after a Tai Chi (TC) Qigong exercise. [Subjects and Methods] Eleven survivors of NPC participated voluntarily in the study. The heart rate of each participant was measured continuously for 1 minute before the TC Qigong intervention, during the 5-minute TC Qigong intervention, and for 1 minute after the intervention, using a Polar heart-rate monitor. Spectral HRV was expressed in terms of normalised low frequency (LF) power, normalised high frequency (HF) power, and the low frequency/high frequency (LF/HF) power ratio. [Results] Both the LF-power and the HF-power components had significant time effects. However, the time effect of the LF/HF power ratio was not significant. Post hoc contrast analysis revealed a significant decrease in LF power and a concomitant increase in HF power during the 4th minute and 5th minute of the TC Qigong exercise. [Conclusion] Five minutes of TC Qigong exercise was found to improve HRV by increasing HF power and decreasing LF power, but these effects were transient. TC Qigong might be an appropriate exercise for improving the ANS function and psychological and cardiac health of survivors of NPC.Key words: Autonomic nervous system, Mind-body exercise, Head-and-neck cancer     

Specificity of the glucose oxidase reaction and interference with the quantitative glucose oxidase—peroxidase—0-dianisidine method

Abstract

Although ambulatory measurements of heart rate variability (HRV) are widely used, the reproducibility and seasonal variation of ambulatory sampled short-term HRV measurements in healthy participants has not been investigated before. In the present study we collected ambulatory ECGs from 19 healthy participants monthly for 12 months, and for a sub-group of 12 participants weekly for one month. Frequency-domain HRV-metrics were calculated for 5 min ECG segments during (i) a 15-min self-selected rest period (awake period), and (ii) a 30-min sleep period starting 45 min after estimated sleep onset. Total, within- and between-subject coefficient of variation (CV) and seasonal variation were estimated for ln (TP), ln (LFP), ln (HFP), ln (LF/HF), LFnu, HFnu, the mean heart period and the ECG derived respiratory frequency. The within- and between-subject CV varied considerably between different variables, from < 10% for ln (TP) and ln (LFP) to >100% for ln (LF/HF). Within- and between-subject CV of ln (HFP), LFnu and HFnu were 10-40%. A weak, but significant, seasonal variation was found for ln (TP) (p = 0.05), ln (LFP) (p<0.05) and the respiratory frequency (p<0.01), but the seasonal variation did not affect the within-subject CV. Furthermore, sample size calculations demonstrated that the reproducibility was sufficient for ambulatory HRV measurements to be used to study autonomic cardiac regulation in healthy populations.     

The effects of therapeutic ultrasound on heart rate variability: a placebo controlled trial

The effect of therapeutic ultrasound (US) on nervous system is controversial and the effect on autonomic nervous system is not clear. Therefore, the present placebo-controlled trial was planned to investigate the effects of therapeutic US application on right-side stellate ganglion, by using analysis of heart rate variability (HRV). A total 12 healthy volunteers were included in the study. RR intervals were recorded for 5 min before and after the US application, in supine and sitting positions. All procedures were repeated in all participants with sham US one week later. The heart rate (HR) was obtained by time-domain analysis and low frequency (LF) power (%), high frequency (HF) power (%) and LF/HF ratio values were obtained by frequency-domain (power spectral density) analysis. After the US application, there was a decrease in the HR (p = 0.002) and the HF power (%) component (p = 0.015) in supine position and a decrease in HR (p = 0.002) and LF/HF ratio (p = 0.028) in sitting position. There was no significant difference after the sham US application. In conclusion, we observed that therapeutic US application on stellate ganglion causes alterations on HRV parameters.     

Reflection of heart rate regulation on linear and nonlinear heart rate variability measures

The aim of this study was to examine the dependence of heart rate variability (HRV) measures on RR interval length and to find out relationships between linear and nonlinear measures. The spectral powers in very low (VLF), low (LF) and high (HF) frequency regions, short-term scaling exponent alpha(1) and sample entropy (SampEn) were determined. All spectral powers increased with increasing RR interval length until they reached a plateau. Neighbouring spectral powers were strongly correlated. The largest fraction of the spectrum consisted of VLF (from about 40 to 95%) and the smallest of HF, although HF was most sensitive to changes in RR interval length. SampEn is also increased with increasing RR interval, reaching a plateau. The dependence of alpha(1) on RR showed a deflection point at 0.5 s. Nonlinear measures can be expressed by spectral powers: alpha(1) by a linear function of ln(LF/HF) and SampEn by a quadratic function of ln HF. We concluded that during the day an increase of HR up to 120 beats min(-1) was reflected in a reduction in HF and LF and to a smaller extent in VLF and by decreased complexity and increased correlation in RR interval series. In sleep, HRV measures are at a plateau. We suggest that below intrinsic value, HR is regulated mainly by changes of parasympathetic activity, reflected in linear and nonlinear HRV measures.