Showing papers on "Heart rate variability published in 1997"
TL;DR: In this article, the authors examined the physiological origins and mechanisms of heart rate variability, considered quantitative approaches to measurement, and highlighted important caveats in the interpretation of heart rates variability, and outlined guidelines for research in this area.
Abstract: Components of heart rate variability have attracted considerable attention in psychology and medicine and have become important dependent measures in psychophysiology and behavioral medicine. Quantification and interpretation of heart rate variability, however, remain complex issues and are fraught with pitfalls. The present report (a) examines the physiological origins and mechanisms of heart rate variability, (b) considers quantitative approaches to measurement, and (c) highlights important caveats in the interpretation of heart rate variability. Summary guidelines for research in this area are outlined, and suggestions and prospects for future developments are considered.
3,273 citations
TL;DR: It is demonstrated that HRV analysis of ambulatory ECG recordings based on fully automated methods can have prognostic value in a population-based study and that nonlinear HRV indices may contribute prognosticvalue to complement traditional HRV measures.
Abstract: BACKGROUND: Despite much recent interest in quantification of heart rate variability (HRV), the prognostic value of conventional measures of HRV and of newer indices based on nonlinear dynamics is not universally accepted. METHODS AND RESULTS: We have designed algorithms for analyzing ambulatory ECG recordings and measuring HRV without human intervention, using robust methods for obtaining time-domain measures (mean and SD of heart rate), frequency-domain measures (power in the bands of 0.001 to 0.01 Hz [VLF], 0.01 to 0.15 Hz [LF], and 0.15 to 0.5 Hz [HF] and total spectral power [TP] over all three of these bands), and measures based on nonlinear dynamics (approximate entropy [ApEn], a measure of complexity, and detrended fluctuation analysis [DFA], a measure of long-term correlations). The study population consisted of chronic congestive heart failure (CHF) case patients and sex- and age-matched control subjects in the Framingham Heart Study. After exclusion of technically inadequate studies and those with atrial fibrillation, we used these algorithms to study HRV in 2-hour ambulatory ECG recordings of 69 participants (mean age, 71.7+/-8.1 years). By use of separate Cox proportional-hazards models, the conventional measures SD (P .3), were not. In multivariable models, DFA was of borderline predictive significance (P=.06) after adjustment for the diagnosis of CHF and SD. CONCLUSIONS: These results demonstrate that HRV analysis of ambulatory ECG recordings based on fully automated methods can have prognostic value in a population-based study and that nonlinear HRV indices may contribute prognostic value to complement traditional HRV measures.
516 citations
TL;DR: In middle-aged men and probably in elderly men, low heart rate variability is predictive of mortality from all causes, which suggests that low heart rates variability is an indicator of compromised health in the general population.
Abstract: Low heart rate variability is associated with high risk of sudden death in myocardial infarction patients. This has been attributed to unfavorable autonomic cardiac control. In the present study, the predictive value of heart rate variability for sudden death, mortality from coronary heart disease, and from all causes was investigated in the general population, using brief electrocardiographic recordings. From 1960 to 1985, 878 middle-aged Dutch men, aged 40-60 years, were followed and repeatedly examined as part of the Zutphen Study. In 1985 the remaining cohort was extended to 885 elderly men, aged 65-85 years, and followed until 1990. Heart rate variability (standard deviation of duration of normal RR intervals) was determined from the resting 12-lead electrocardiogram. The 5-year age-adjusted relative rate of total mortality of men with heart rate variability of < 20 milliseconds (msec) compared with men with heart rate variability of 20-39 msec was 2.1 (95 percent confidence interval 1.4-3.0) in middle-aged men and 1.4 (95% confidence interval 0.9-2.2) in elderly men. Death from noncoronary causes, especially cancer, contributed significantly to this elevated risk. The association of low heart rate variability with sudden death or coronary heart disease mortality was less consistent. In conclusion, in middle-aged men and probably in elderly men, low heart rate variability is predictive of mortality from all causes. This suggests that low heart rate variability is an indicator of compromised health in the general population.
489 citations
TL;DR: Investigation of HRV parameters in 102 consecutive patients with moderate to severe CHF concluded that depressed HRV on 24-hour ambulatory electrocardiography monitoring is an independent risk factor for a poor prognosis in patients with CHF.
Abstract: After acute myocardial infarction, depressed heart rate variability (HRV) has been proven to be a powerful independent predictor of a poor outcome Although patients with chronic congestive heart failure (CHF) have also markedly impaired HRV, the prognostic value of HRV analysis in these patients remains unknown The aim of this study was to investigate whether HRV parameters could predict survival in 102 consecutive patients with moderate to severe CHF (90 men, mean age 58 years, New York Heart Association [NYHA] class II to IV, CHF due to idiopathic dilated cardiomyopathy in 24 patients and ischemic heart disease in 78 patients, ejection fraction [EF], 26%; peak oxygen consumption, 169 ml/kg/min) after exclusion of patients in atrial fibrilation with diabetes or with chronic renal failure In the prognostic analysis (Cox proportional-hazards model, Kaplan-Meier survival analysis), the following factors were investigated: age, CHF etiology, NYHA class, EF, peak oxygen consumption, presence of ventricular tachycardia on Holter monitoring, and HRV measures derived from 24-hour electrocardiography monitoring, calculated in the time (standard deviation of all normal RR intervals [SDNN], standard deviation of 5-minute RR intervals [SDANN], mean of all 5-minute standard deviations of RR intervals [SD], root-mean-square of difference of successive RR intervals [rMSSD], and percentage of adjacent RR intervals >50 ms different [pNN50]) and frequency domain (total power [TP], power within low-frequency band [LF], and power within high-frequency band [HF]) During follow-up of 584 ± 405 days (365 days in all who survived), 19 patients (19%) died (mean time to death: 307 ± 315 days, range 3 to 989) Cox's univariate analysis identified the following factors to be predictors of death: NYHA (p = 0003), peak oxygen consumption (p = 001), EF (p = 002), ventricular tachycardia on Holter monitoring (p = 005), and among HRV measures: SDNN (p = 0004), SDANN (p = 0003), SD (p = 002), and LF (p = 0003) In multivariate analysis, HRV parameters (SDNN, SDANN, LF) were found to predict survival independently of NYHA functional class, EF, peak oxygen consumption, and ventricular tachycardia on Holter monitoring The Kaplan-Meier survival curves revealed SDNN 100 ms (p = 0008) The coexistence of SDNN In 102 consecutive patients with stable chronic congestive heart failure and sinus rhythm, several heart rate variability measures derived from 24-hour electrocardiographic recording were significant prognostic risk markers, independent of clinical variables (New York Heart Association class, peak oxygen consumption, left ventricular ejection fraction) The coexistence of the standard deviation of all normal RR intervals
486 citations
TL;DR: The arousal data along with Stage 2 sleep transition data support the contention that increases in central nervous system sympathetic activity precede and possibly play a role in the initiation of REM sleep and arousals during sleep.
413 citations
TL;DR: These are the first human data to show that use of the aldosterone antagonist, spironolactone, can positively improve time-domain heart rate variability and reduce myocardial collagen turnover, as reflected by further reductions in serum procollagen peptide, despite concurrent ACE inhibitor treatment.
Abstract: Background: Experimental data suggest that aldosterone has harmful effects promoting myocardial fibrosis and disturbing autonomic balance. There has been no evidence of these potential effects in intact man. Methods and Results: We report the findings in 31 patients with stable chronic heart failure (CHF) who were treated with spironolactone (50–100 mg/day) or placebo in addition to diuretics and angiotensin converting enzyme (ACE) inhibition. In a controlled randomised double-blind study, we found that spironolactone treatment reduced circulating levels of procollagen type III N-terminal amino peptide, a marker of vascular collagen turnover, and in addition increased time-domain parameters of heart rate variability ( n = 24). These latter parameters suggest a parasympathomimetic effect for additional spironolactone. Spironolactone significantly reduced heart rate (prolonged RR interval) particularly during the dawn hours (06.00–09.00 h). In this unbalanced study it was not possible to provide a detailed diurnal assessment of the impact of spironolactone on heart rate variability, but the preliminary data suggest that there may be an interaction with the autonomic nervous system which varies in time. Conclusions: These are the first human data to show that use of the aldosterone antagonist, spironolactone, can positively improve time-domain heart rate variability and reduce myocardial collagen turnover, as reflected by further reductions in serum procollagen peptide, despite concurrent ACE inhibitor treatment. Residual aldosterone after ACE inhibitor treatment may therefore have a role promoting arrhythmia and cardiac death by two mechanisms. Effects of additional spironolactone on slowing heart rate (and potentially the detrimental effect of aldosterone) were most prominent between 6 a.m. and 10 a.m. when cardiac death is also known to be most prominent.
350 citations
TL;DR: The findings from this population-based, prospective study suggest that altered cardiac autonomic activity, especially lower parasympathetic activity, is associated with the risk of developing CHD.
Abstract: Cardiac autonomic activity, as assessed by heart rate variability, has been found to be associated with postmyocardial infarction mortality, sudden death, and all-cause mortality. However, the association of heart rate variability and the incidence of coronary heart disease (CHD) is not well described. The authors report on the association of baseline cardiac autonomic activity (1987-1989) with incident CHD after 3 years (1990-1992) of follow-up of the Atherosclerosis Risk in Communities Study cohort selected from four study centers in the United States by using a case-cohort design. The authors examined 137 incident cases of CHD and a stratified random sample of 2,252 examinees free of CHD at baseline. Baseline, supine, resting beat-to-beat heart rate data were collected. High- (0.16-0.35 Hz) and low- (0.025-0.15 Hz) frequency spectral powers and high-/low-frequency power ratio, estimated from spectral analysis, and standard deviation of all normal R-R intervals, calculated from time domain analysis, were used as the conventional indices of cardiac parasympathetic, sympatho-parasympathetic, and their balance, respectively. Incident CHD was defined as hospitalized myocardial infarction, fatal CHD, or cardiac revascularization procedures during 3 years of follow-up. The age, race, gender, and other CHD risk factor-adjusted relative risks (and 95% confidence intervals) of incident CHD comparing the lowest quartile with the upper three quartiles of high-frequency power, low-frequency power, high-/low-frequency power ratio, and standard deviation of R-R intervals were 1.72 (95% confidence interval (CI) 1.17-2.51), 1.09 (95% CI 0.72-1.64), 1.25 (95% CI 0.84-1.86), and 1.39 (95% CI 0.94-2.04), respectively. The findings from this population-based, prospective study suggest that altered cardiac autonomic activity, especially lower parasympathetic activity, is associated with the risk of developing CHD.
304 citations
TL;DR: A link between increased peripheral chemosensitivity and impaired autonomic control, including baroreflex inhibition, is demonstrated and the clinical importance of this phenomenon warrants further investigation.
Abstract: Background The precise mechanisms responsible for the sympathetic overactivity and blunted baroreflex control in chronic heart failure (CHF) remain obscure. Augmented peripheral chemosensitivity has recently been demonstrated in CHF. We evaluated the relation between peripheral chemoreflex sensitivity and autonomic activity in patients with CHF.
Methods and Results We studied in 26 stable patients with CHF the peripheral chemosensitivity (ventilatory response to hypoxia using transient inhalations of pure nitrogen), autonomic balance (spectral analysis of heart rate variability [HRV]), and baroreflex sensitivity (bolus phenylephrine method and α index). To determine whether transient inactivation of peripheral chemoreceptors might influence autonomic balance, 12 patients underwent a second study during which they breathed 100% O2. Peripheral chemosensitivity correlated inversely with HRV power within the low-frequency band (0.04 to 0.15 Hz) ( r =−.52, P =.006) and inversely with baroreflex sensitivity ( r =−.60, P =.005). When the patients were divided into two groups according to the chemosensitivity of age-matched normal controls (above and below mean+2 SDs of chemosensitivity of control subjects), those above the normal range revealed more impaired autonomic balance, ie, lower baroreflex sensitivity (1.4±1.3 versus 5.0±1.5 ms/mm Hg, P <.0001) and depressed values of low-frequency power (2.5±1.8 versus 4.1±0.8 ln ms2, P <.005) compared with those with normal chemosensitivity. Transient hyperoxia did not alter heart rate or systolic pressure but resulted in an increase in HRV and an improvement in baroreflex sensitivity.
Conclusions A link between increased peripheral chemosensitivity and impaired autonomic control, including baroreflex inhibition, is demonstrated. The clinical importance of this phenomenon warrants further investigation.
278 citations
TL;DR: Those with higher depression scores had lower heart rate variability during daily life in comparison to the lower depression score group, and these findings may be related to the reported relationship between depression and survival risk in patients with coronary artery disease.
Abstract: OBJECTIVE This study tested the hypothesis that coronary artery disease patients with higher depression scores have lower heart rate variability during daily life. METHOD Thirty-three men and nine women, ranging in age from 46 to 79, with coronary artery disease and exercise-induced ischemia were studied. The standard deviation of normal R-R intervals (SDNN) and average heart rate were obtained from 24-hour ambulatory electrocardiographic monitoring. Patients were grouped by a median split of the Minnesota Multiphasic Personality Inventory (MMPI-D) score. RESULTS SDNN was lower (p = .009) and average heart rate was higher (p = .003) in patients with higher depression scores. These relationships remained substantially unaltered after statistically adjusting for the only demographic/clinical factor that varied between the groups: gender. CONCLUSIONS In comparison to the lower depression score group, those with higher depression scores had lower heart rate variability during daily life. These findings may be related to the reported relationship between depression and survival risk in patients with coronary artery disease.
232 citations
TL;DR: Anxiety and antisocial behavior showed distinct relationships to heart rate, and to the autonomically mediated components of heart rate variability from postural and respiratory sources, suggesting utility for future research in this area.
Abstract: We explored relationships between anxiety and antisocial behavior and autonomic heart rate regulation in a homogenous sample (N = 175) of 15-year-old males. Measures of anxiety and antisocial behavior were obtained at yearly intervals over a period of 4-6 years. Components of heart rate variability associated with postural (sympathetic) and respiratory (vagal) change and transfer of respiratory to heart rate variability were estimated at age 15 using spectral analytic techniques. Anxiety and antisocial behavior were predictably related to enhanced and diminished levels of mean heart rate, respectively. Anxiety was also predictably related to enhanced sympathetic mediation of phasic postural effects on heart rate. Antisocial behavior was unexpectedly related to disruption of vagally mediated, phasic respiratory effects on heart rate. Anxiety and antisocial behavior showed distinct relationships to heart rate, and to the autonomically mediated components of heart rate variability from postural and respiratory sources. Spectral analytic techniques helped elucidate these unique regulatory patterns, suggesting utility for future research in this area.
231 citations
TL;DR: It is demonstrated that the power of cardiovascular oscillations in the VLF band in awake patients with mild to severe chronic heart failure is greatly increased by the common occurrence of unrecognized irregularity of breathing, which may confound the use of heart rate variability measures as indexes of autonomic tone or prognosis.
Abstract: Background Reduced heart rate variability, particularly in the very-low-frequency (VLF) spectral band, has been found to be a marker for poor prognosis in patients after myocardial infarction, but ...
TL;DR: The results show that age, and to a lesser degree gender, are important determinants of heart rate variability in healthy subjects, and the physiological effects of ageing, with diminishing heart rates variability in older age groups, must also be taken into account.
Abstract: The effects of age and gender on heart rate variability as measured by spectral and time domain analysis of 24 h ECG recordings were evaluated in 101 healthy subjects, 49 men and 52 women (20-69 years of age). In the frequency domain, total power, very low-frequency power, low-frequency power and high-frequency power were negatively correlated to age (P < 0.001 for all variables). Total power decreased by 30% between 20-29 and 60-69 years of age. In the time domain, SDNN-index, the mean of the standard deviations of all normal R-R intervals for all 5 min segments of a 24 h ECG recording, was negatively correlated to age (P < 0.001). Total power, very low-frequency power, low-frequency power and the low-frequency/high-frequency ratio were lower in women (P < 0.05, P < 0.05, P < 0.01 and P < 0.01), although the absolute differences were much smaller than for age. There was a pronounced circadian variation; at night total power increased in all age groups (P < 0.01). The results show that age, and to a lesser degree gender, are important determinants of heart rate variability in healthy subjects. Heart rate variability is a valuable tool for risk stratification in cardiovascular disease, but the physiological effects of ageing, with diminishing heart rate variability in older age groups, must also be taken into account.
TL;DR: HRV is comparable in older men and women, however, HRV is differently affected by age, as in men, for whom initial levels of HRV are significantly higher.
Abstract: Gender and age are both known to affect heart rate variability (HRV). Their interaction is not known. HRV, determined from 24-hour Holter recordings, was compared between gender-matched older (15 men and 15 women, aged 67 +/- 3 years, range 64 to 76) and younger (15 men and 15 women, aged 33 +/- 4 years, range 26 to 42) subjects selected for an age difference of approximately 35 years. HRV for older and younger subjects was compared separately by gender. HRV was also compared by gender within groups. Heart rates were significantly higher, and all time and frequency domain indexes of HRV were significantly lower among the older than among the younger men. Among the women only the shorter term indexes of HRV were significantly lower in the older group. When HRV was compared by gender within age groups, there were no significant differences between men and women in the older group. In the younger group, men had lower heart rates, and all 24-hour time domain indexes of HRV, except those that reflect vagal modulation of heart rate, were significantly higher than those in women. We conclude that HRV is comparable in older men and women. However, HRV is differently affected by age. In men, for whom initial levels of HRV are significantly higher, older age is associated with a global reduction in HRV, reflecting reductions in both sympathetic and parasympathetic modulation and a loss of circadian variability. In women, older age is associated mainly with a decline in shorter term indexes of HRV without significant changes in circadian variability.
TL;DR: Dynamics analysis of RR interval behavior and traditional measures of heart rate variability were compared between postinfarction patients with and without vulnerability to ventricular tachyarrhythmias in a case-control study.
Abstract: Dynamics analysis of RR interval behavior and traditional measures of heart rate variability were compared between postinfarction patients with and without vulnerability to ventricular tachyarrhythmias in a case-control study. Short-term fractal correlation of heart rate dynamics was better than traditional measures of heart rate variability in differentiating patients with and without life-threatening arrhythmias.
TL;DR: These data in a healthy pediatric population confirm a progressive maturation of the autonomic nervous system during childhood and may be utilized to examine the effects of underlying disease processes or therapeutic interventions on cardiac autonomic tone during infancy and childhood.
Abstract: Heart rate variability is a noninvasive index of the neural activity of the heart. The present study examined heart rate variability indices in 210 infants and children aged 3 days to 14 years to obtain normal ranges for all age classes. Heart rate variability was measured by calculating mean RR interval over the length of the analysis, mean RR interval during quiet sleep, 5 time-domain (SDNN, SDNN-i, SDANN-i, r-MSSD, pNN50), and 4 frequency-domain (VLF, LF, HF, LF/HF ratio) indices. Our data show a significant positive correlation between all indices and the mean RR interval over the length of the analysis, except for the LF/HF ratio for which the correlation was binomial. A positive power correlation was also found between all parameters and age. The multiple correlation analysis confirmed the independent effect of age and mean RR interval on the heart rate variability. These data in a healthy pediatric population confirm a progressive maturation of the autonomic nervous system during childhood and may be utilized to examine the effects of underlying disease processes or therapeutic interventions on cardiac autonomic tone during infancy and childhood.
Patent•
31 Mar 1997TL;DR: In this article, a home-based wearable self-contained system was used to determine sleep state and respiratory pattern of a patient based on the frequency of eyelid movements, the frequency and strength of head movements, and heart rate variability of the patient.
Abstract: A method for determining the sleep state of a patient includes monitoring heart rate variability of the patient and determining sleep state based on the heart rate variability. The method also may include monitoring the frequency of eyelid movements and making the sleep state determination based also on the frequency of eyelid movements. A method for determining respiratory pattern includes monitoring heart rate variability by receiving heart beat signals and determining respiratory pattern from the strength of the signals. A home-based, wearable, self-contained system determines sleep-state and respiratory pattern, and assesses cardiorespiratory risk, of a patient based on the frequency of eyelid movements, the frequency of head movements, and heart rate variability of the patient.
TL;DR: Findings suggest that there is a cerebral lateralization in cardiac autonomic control and that the right cerebral hemisphere predominantly modulates sympathetic activity in patients with intracarotid amobarbital disease.
Abstract: Objective: To identify cerebral hemispheric lateralization in cardiac autonomic control. Patients: Eight patients undergoing an intracarotid amobarbital sodium test as a presurgical evaluation of temporal lobe epilepsy. Design: Power spectral analysis of heart rate variability before and after intracarotid amobarbital injection. Setting: University hospital and research center. Main Outcome Measure: The changes in the ratio of low-frequency (LF) (sympathetic) to high-frequency (HF) (parasympathetic) power (LF/HF ratio), a measure of sympathovagal balance, after hemispheric inactivation. Results: The LF/HF ratio changed as follows: right preinactivation=3.81±0.96, postinactivation=3.40±1.23; left preinactivation=2.74±0.49, postinactivation=4.34±0.59 (mean±SEM). The test of interaction between laterality and inactivation using a 2-way repeated-measures analysis of variance was statistically significant ( P =.001). The increased ratio on the left side (1.61±0.70) was statistically significant ( P =.03), but the decrease on the right side (−0.40±0.46) was not ( P ≤.70). Conclusions: These findings suggest that there is a cerebral lateralization in cardiac autonomic control and that the right cerebral hemisphere predominantly modulates sympathetic activity. This study may help identify subgroups of patients with intracranial disease at high risk of cardiac complications.
TL;DR: A significant positive correlation was observed between the n-3 fatty acid docosahexaenoic acid and heart rate variability and a possible antiarrhythmic effect of long-chained n- 3 polyunsaturated fatty acids was elucidated.
Abstract: To elucidate a possible antiarrhythmic effect of long-chained n-3 polyunsaturated fatty acids, heart rate variability was assessed in 52 patients with a previous myocardial infarction and left ventricular dysfunction The content of n-3 polyunsaturated fatty acids in platelets was closely associated with the patient's fish-consuming habits, and a significant positive correlation was observed between the n-3 fatty acid docosahexaenoic acid and heart rate variability
TL;DR: Investigation of HRV in patients with idiopathic dilated cardiomyopathy can identify patients with IDC who have an increased risk of cardiac death or heart transplantation and is related to left ventricular dysfunction and not to ventricular arrhythmias.
TL;DR: It is concluded that OSAS alters beat-to-beat variation in characteristic fashions in children, that the variability changes occur at all heart rates but are most significant at slow heart rates, and that these heart rate patterns could assist in screening of suspected cases of OSAS.
Abstract: Adults with obstructive sleep apnea syndrome (OSAS) display substantial heart rate changes associated with obstructive events, and recent reports suggest similar heart rate changes in children with OSAS. These rate changes could assist screening of young patients for OSAS. Six-hour polysomnographic recordings were obtained from seven children with OSAS (mean age: 4.5 years; apnea index: 19.5 +/- 5.1) and from seven primary snorers without OSAS who served as controls (mean age: 4.7; apnea index: 0). Scatterplots of each cardiac R-R interval against the preceding interval (Poincare plots) were used to assess beat-to-beat cardiac variability at different heart rates. Beat-to-beat variation at slow rates was significantly increased in children with OSAS relative to controls, while variation at fast and intermediate heart rates was significantly reduced in these children. We conclude that OSAS alters beat-to-beat variation in characteristic fashions in children, that the variability changes occur at all heart rates but are most significant at slow heart rates, and that these heart rate patterns could assist in screening of suspected cases of OSAS.
Journal Article•
TL;DR: In FM, there is a deranged sympathetic response to orthostatic stress, which may have implications regarding the pathogenesis of FM.
Abstract: Objective. To assess the sympathetic-parasympathetic balance in individuals with fibromyalgia (FM), and its response to orthostatic stress, by power spectral analysis of heart rate variability. Methods. We studied 19 women with FM and 19 age matched controls. A high resolution electrocardiogram was obtained in supine and standing postures after achieving a stable heart rate. Spectral analysis of R-R intervals was done by the fast Fourier transform algorithm. Results. Analyses of the different frequency components revealed significant differences between the 2 groups in the low frequency (0.050-0.150 Hz) band, which reflects modulation of the sympathetic nervous system. Controls displayed an increased power spectral density upon standing (+0.081 ± 0.217 Hz); individuals with FM had a discordant response (-0.057 ± 0.097 Hz) (p = 0.018). Conclusion. In FM, there is a deranged sympathetic response to orthostatic stress. This abnormality may have implications regarding the pathogenesis of FM.
TL;DR: Sleep ULF power is not significantly affected by age, whereas VLF, LF and HF powers and fractal dimensions of heart rate significantly decrease with age during awake as well as sleep periods.
Abstract: Objective: Previous studies on short-term time series of heart rate suggest an inverse relationship between age and spectral powers of heart rate variability in various frequency bands. In this study, we examined the relationship between age (6–61 years) and long-term heart rate variability. Methods: We obtained 24-h Holter ECG in 33 healthy human subjects (11 children and 22 adults). The heart rate data were analyzed by using spectral analysis and fractal dimensions of the time series. Results: We found a significant negative correlation between age and very low frequency (VLF, 0.0033–0.04 Hz), low frequency (LF, 0.04–0.15 Hz) and high frequency (HF, 0.15–0.5 Hz) powers and fractal dimensions during awake as well as sleep periods, and a positive correlation between age and LF/HF ratios. Age and ultra-low frequency (ULF, <0.0033 Hz) were modestly and negatively correlated only during the awake period. Conclusions: Sleep ULF power is not significantly affected by age, whereas VLF, LF and HF powers and fractal dimensions of heart rate significantly decrease with age during awake as well as sleep periods.
TL;DR: Besides low left ventricular ejection fraction, HR variability parameters reflecting impaired vagal tone (SDNN, pNN50) were found to predict an increased risk of cardiac death and death due to progressive pump failure.
Abstract: To study the prognostic value of heart rate (HR) variability in heart failure, risk assessment of clinical and HR variability parameters was performed in 159 patients with stable chronic heart failure. Besides low left ventricular ejection fraction, HR variability parameters reflecting impaired vagal tone (SDNN, pNN50) were found to predict an increased risk of cardiac death and death due to progressive pump failure.
TL;DR: Baroreflex regulation of autonomic functions induced by changing positions is modified during the menstrual cycle, suggesting that parasympathetic nerve activity is predominant in the follicular phase, resulting in an impairment of baroreflex caused by posture changes.
Abstract: This study was designed to determine whether autonomic regulation induced by posture changes varies during the menstrual cycle. Heart rate variability (HRV) was analyzed in women with normal menstrual cycles (n = 10, age range 20-37 years) during 3 min periods of controlled frequency breathing (15 breaths/min) in supine followed by sitting positions. In a supine or sitting position, high frequency (HF) components of HRV, which reflects only parasympathetic activity, were significantly high in the follicular phase compared with those in the menstrual phase, suggesting that parasympathetic nerve activity increases in this phase. Following the change of position to sitting from supine, the HF component decreased significantly in the menstrual, ovulatory and luteal phases, but not the follicular or premenstrual phase. After changing the position to sitting, the low to high frequency component ratio, which reflects the balance of autonomic nerve activities, was increased significantly in the menstrual, luteal and premenstrual phases, indicating that sympathetic nerve activities in these phases became predominant by the sitting position. These results suggest that parasympathetic nerve activity is predominant in the follicular phase, resulting in an impairment of baroreflex caused by posture changes. Moreover, baroreflex control of the sympathetic component, not the parasympathetic component, increases in the premenstrual phase, while the reflex response of the sympathetic component is less in the ovulatory phase compared with the menstrual or luteal phase. We concluded that baroreflex regulation of autonomic functions induced by changing positions is modified during the menstrual cycle. A difference of a balance of ovarian hormones may be responsible for these changes of autonomic functions during the menstrual cycle.
TL;DR: This study evaluated cardiac function in patients with temporal lobe epilepsy and found no evidence that changes in autonomic neural control of the heart could be involved in the pathogenesis of sudden unexplained death in Patients with epilepsy.
Abstract: Purpose: Because several reports have described the relation between epilepsy and cardiac arrhythmias and suggest that changes in autonomic neural control of the heart could be involved in the pathogenesis of sudden unexplained death in patients with epilepsy, the aim of this study was to evaluate cardiac function in patients with temporal lobe epilepsy. Methods: Sixty-five patients with epilepsy were evaluated by simultaneous ambulatory 24-h EEG-ECG monitoring, and in 30 of these, power spectral analysis of relative-risk (RR) variability also was carried out, both in the supine position and in a passive tilt position at 60°. The power spectrum of RR variability, the two major spectral components detectable at low frequency (LF) and at high frequency (HF), respectively, and the LF/lIF ratio were calculated. Results: By EEG-ECG monitoring, we recorded six partial seizures, and in four cases, discharges were associated with sinus tachycardia. However, interictally the occurrence of ventricular and supraventricular arrhythmias was not different from that in normal subjects. The spectral analysis of RR variability, on the other hand, demonstrated in patients with epilepsy a significant decrease in the total RR variability and in both of its components (LF and HF) in the supine position, and of the LF/HF ratio in orthostatic position. Conclusions: These findings suggest that the spectral analysis of RR variability may detect disorders of autonomic cardiac control in patients with epilepsy, even in the absence of abnormal findings during ECG monitoring. This alteration, which is more severe in cases with right EEG focus, could play a role in the pathogenesis of cardiac arrhythmias.
TL;DR: In this paper, the authors measured arrhythmia occurrence, R-R interval variability, and plasma catecholamine elevations in male wild-type rats exposed to either a social stressor (defeat) or a nonsocial challenge (restraint).
Abstract: Psychological stressors of different natures can induce different shifts of autonomic control on cardiac electrical activity, with either a sympathetic or a parasympathetic prevalence. Arrhythmia occurrence, R-R interval variability, and plasma catecholamine elevations were measured in male wild-type rats exposed to either a social stressor (defeat) or a nonsocial challenge (restraint). Electrocardiograms were telemetrically recorded, and blood samples were withdrawn through jugular vein catheters from normal, freely moving animals. Defeat produced a much higher incidence of arrhythmias (mostly ventricular premature beats), which were mainly observed in the 60-s time periods after attacks. The social challenge also induced a much stronger reduction of average R-R interval, a lower R-R interval variability (as estimated by the time-domain parameters standard deviation of mean R-R interval duration, coefficient of variance, and root mean square of successive differences in R-R interval duration), and higher elevations of venous plasma catecholamines compared with restraint. These autonomic and/or neuroendocrine data indicate that a social stressor such as defeat is characterized by both a higher sympathetic activation and a lower parasympathetic antagonism compared with a nonsocial restraint challenge, which results in a higher risk for ventricular arrhythmias.
TL;DR: Assessment of HRV in patients with severe head injury found it is a noninvasive method that can be widely used and may improve outcome by allowing earlier detection and treatment of intracranial pathology.
Abstract: Background Analysis of heart-rate variability (HRV) is a promising new technique for noninvasive quantification of autonomic function. We measured HRV in patients with severe head injury to assess its potential as a monitoring tool.Methods Analysis of HRV was prospectively done on all intensive care
TL;DR: In diabetic patients with no or early CAN, regularly performed endurance training increased heart rate variability due to improved sympathetic and parasympathetic supply, whereas in subjects with definite/severe CAN no effect on heart rate Variability could be demonstrated after this kind of training.
Abstract: Objective: To investigate the effects of regularly performed endurance training on heart rate variability in diabetic patients with different degrees of cardiovascular autonomic neuropathy (CAN). Methods: Bicycle ergometer training (12 weeks, 2×30 min/week, with 65% of maximal performance) was performed by 22 insulin-requiring diabetic patients (age 49.5±8.7 years; diabetes duration 18.6±10.6 years; BMI 25.1±3.4 kg/m2): i.e., by 8 subjects with no CAN, 8 with early CAN and by 6 patients with definite/severe CAN. A standard battery of cardiovascular reflex tests was used for grading of CAN, a short-term spectral analysis of heart rate variability for follow-up monitoring of training-induced effects. Results: While the training-free interval induced no changes in spectral indices, the 12-week training period increased the cumulative spectral power of the total frequency band ( P =0.04) but to a different extent ( P =0.039) in different degrees of neuropathy. In patients with no CAN the spectral power in the high-frequency (HF) band (0.15–0.50 Hz) increased from 6.2±0.3 to 6.6±0.4 ln [ms2]; P =0.016, and in the low-frequency (LF) band (0.06–0.15 Hz) from 7.1±0.1 to 7.6±0.3 ln [ms2]; P =0.08, which resulted in an increase of total spectral power (0.06–0.50 Hz) from 7.5±0.1 to 8.0±0.3 ln [ms2] ( P =0.05). Patients with the early form of CAN showed an increase of spectral power in HF (5.1±0.2 to 5.8±0.1 ln [ms2], P =0.05) and LF bands (5.6±0.1 to 6.3±0.1 ln [ms2], P =0.008), resulting in an increase of total power from 6.1±0.1 to 6.6±0.1 ln [ms2] (P =0.04), whereas those with definite/severe CAN showed no changes after the training period. Training improved fitness in the whole patient cohort. The increased autonomic tone as assessed by spectral indices disappeared after a training withdrawal period of 6 weeks. Conclusions: In diabetic patients with no or early CAN, regularly performed endurance training increased heart rate variability due to improved sympathetic and parasympathetic supply, whereas in subjects with definite/severe CAN no effect on heart rate variability could be demonstrated after this kind of training.
TL;DR: It is suggested that quinapril significantly increases parasympathetic activity in patients with DAN 3 months after treatment initiation and sustains this effect until the 6th month, which might contribute to the reduction of the risk for malignant ventricular arrhythmias in these patients.
Abstract: OBJECTIVE Heart rate variability (HRV) time and frequency domain indexes are strong predictors of malignant arrhythmias and sudden cardiac death. Patients with diabetic autonomic neuropathy (DAN) have an increased cardiovascular mortality rate compared with diabetic patients without DAN. RESEARCH DESIGN AND METHODS The present double-blind, randomized, and placebo-controlled study analyzed the effect of quinapril, an ACE inhibitor, on HRV time and frequency domain variables in patients with DAN. Forty patients (17 men and 23 women) of a mean age of 51 (range 19–68) years, free of coronary artery disease and arterial hypertension, were randomized into a quinapril or placebo group. HRV was recorded at months 0, 3, and 6. The parameters measured were 1) time domain indexes: SD of all 24-h R-R intervals (intervals between consecutive electrocardiogram R waves), or SDNN/24-h; mean of SD of R-R intervals of all 5-min segements (SDNN/5-min); root-mean-square of the differences of successive R-R intervals (RMSSD); and percentage of the R-R intervals differing more than 50 ms (pNN50); and 2) frequency domain indexes: total power (TP), high-frequency power (HFP), low-frequency power (LFP), and very-low-frequency power (VLFP). HRV level of the 40 patients were compared with one of 20 matched diabetic patients, of analogous glycemic control without DAN, and 20 healthy control subjects. RESULTS Quinapril, compared with placebo, increased total HRV: SDNN/24-h ( P P P P P P CONCLUSIONS Our findings suggest that quinapril significantly increases parasympathetic activity in patients with DAN 3 months after treatment initiation and sustains this effect until the 6th month. This might contribute to the reduction of the risk for malignant ventricular arrhythmias in these patients.