Standardized tests of heart rate variability: normal ranges obtained from 309 healthy humans, and effects of age, gender, and heart rate

[Sympatho-vagal balance and cardiac response to mental challenge]

BACKGROUND

Based on functional relations between the central autonomic network and cortical areas involved in motivational, attentional, affective, and executive function, autonomic regulation can mediate cognitive performance as well as cardiovascular and psychosomatic diseases. Our objective was to test the predictive value of resting heart rate variability (HRV), a measure of sympatho-vagal balance, with regard to the type and intensity of cardiovascular responses to mental challenge.

MATERIALS AND METHODS

A total of 248 healthy subjects (85 females, aged 47.3+/-7.6 years; 163 males, aged 47.5+/-6.7 years) were included in the study. All participants underwent standardized psychometric testing (e.g., Stroop's color-word-conflict test).

RESULTS

First, we found significant increases of heart rate and sympatho-vagal balance (low frequency/high frequency) and significant decreases of absolute LF- and HF-power in response to mental tasks. Second, there were significant differences in cardiovascular response to mental challenge when clustering our population on the basis of sympatho-vagal balance at rest.

CONCLUSIONS

We conclude that short-term recordings of HRV can provide health-related information of cardio-vascular response to mental challenge. However, there is no association between sympatho-vagal balance at rest and classical cardiovascular risk factors.

The association of gender, age, body mass index, and vital signs in healthy plateletapheresis donors

In order to determine the association between gender, age, body mass index and vital signs among healthy plateletapheresis donors, the mean and median values from the most recent donations of 236 plateletapheresis donors were calculated for age, body mass index (BMI), oral temperature, blood pressure (BP), and pulse. Values of these parameters were compared after stratification by gender, age, and BMI and multiple regression analysis between parameters performed. Gender, age, and BMI were associated with significant differences in vital signs of healthy plateletapheresis donors.

The influence of age on heart rate variability during morning wakefulness

OBJECTIVE

Early morning wakefulness is associated with a peak in cardiac events. The influence of ageing on cardiac regulation during this time is unknown. This cross-sectional study of healthy men and women (n = 40, 20-30 and >60 years) investigated the effect of age on heart rate variability (HRV) during morning versus evening wakefulness and sleep.

METHODS

Stable electrocardiogram data during each wake period and sleep stage was analysed using power spectral analysis. HRV measurements were assessed using two (young, older) by two (male, female) ANOVAs with repeated measures on wake/sleep stage.

RESULTS

Young adults experienced increased low-frequency power and low-frequency/high-frequency ratios during morning wakefulness versus slow wave sleep (p < 0.01). Older adults did not show any variation in any HRV variables across wake and sleep stages. All effects were independent of gender.

INTERPRETATION

Older adults did not experience increased sympathetic dominance during morning wakefulness; thus in the older population, fluctuations in autonomic control, indicated by HRV measurements, are unlikely to account for increased occurrence of cardiac events at this time.

Heart rate variability: an objective measure of autonomic activity and bladder sensations during urodynamics

AIMS

There are still controversies regarding the reproducibility of cystometric data and no objective measurement of bladder sensations is currently available. Additionally, very little information exists about autonomic activity during standard filling cystometry (FC). The aim of this study was to evaluate the use of heart rate variability (HRV) analysis as a reliable monitor of the autonomic nervous system and objective measure for bladder sensations during FC.

METHODS

In a volunteer sample of healthy female subjects a standard FC at 25 ml/min was performed, using an 8 Fr microtip catheter with integrated pressure transducers. During FC, subjects had to indicate first sensation of filling (FSF), first desire to void (FDV) and strong desire to void (SDV). A 3-lead electrocardiogram was continuously recorded. After 5 h all measurements were repeated. Power spectrum analysis was used to analyse HRV, to obtain low frequency (LF) and high frequency (HF) parameters, from which the LF/HF ratio was derived.

RESULTS

12 subjects with a mean age of 23.3 +/- 2.3 years could be included. 11 of 12 subjects completed both measurement sessions. One subjects had to be excluded, due to irritating urethral discomfort following catheterisation. The LF/HF ratio showed a reproducible activation pattern in the healthy subjects with a stable sympathovagal balance until FDV. Before SDV was indicated, the sympathovagal balance started to shift towards sympathetic activation and caused a significant increase in LF/HF.

CONCLUSION

HRV analysis seems to be a useful indicator for the general activation pattern of the sympathovagal balance during FC, correlating the intensity of the bladder filling sensation to stress and sympathetic activation.

Association between anxiety disorders and heart rate variability in The Netherlands Study of Depression and Anxiety (NESDA)

OBJECTIVE

To determine whether patients with different types of anxiety disorder (panic disorder, social phobia, generalized anxiety disorder) have higher heart rate and lower heart rate variability compared with healthy controls in a sample that was sufficiently powered to examine the confounding effects of lifestyle and antidepressants.

METHODS

The standard deviation of the normal-to-normal intervals (SDNN), heart rate (HR), and respiratory sinus arrhythmia (RSA) were measured in 2059 subjects (mean age = 41.7 years, 66.8% female) participating in The Netherlands Study of Depression and Anxiety (NESDA). Based on the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition (DSM-IV) and Composite International Diagnostic Interview (CIDI), NESDA participants were classified as healthy controls (n = 616), subjects with an anxiety diagnosis earlier in life (n = 420), and subjects with current anxiety diagnosis (n = 1059).

RESULTS

Current anxious subjects had a significantly lower SDNN and RSA compared with controls. RSA was also significantly lower in remitted anxious subjects compared with controls. These associations were similar across the three different types of anxiety disorders. Adjustment for lifestyle had little impact. However, additional adjustment for antidepressant use reduced all significant associations between anxiety and HRV to nonsignificant. Anxious subjects who used a tricyclic antidepressant, a selective serotonin reuptake inhibitor, or another antidepressant showed significantly lower mean SDNN and RSA compared with controls (effect sizes = 0.20-0.80 for SDNN and 0.42-0.79 for RSA). Nonmedicated anxious subjects did not differ from controls in mean SDNN and RSA.

CONCLUSION

This study shows that anxiety disorders are associated with significantly lower HR variability, but the association seems to be driven by the effects of antidepressants.

Influence of acute epinephrine infusion on endotoxin-induced parameters of heart rate variability: a randomized controlled trial

OBJECTIVE

To determine whether the acute anti-inflammatory influence of epinephrine (EPI) extends to changes in heart rate variability (HRV) induced by the prototypical inflammatory stimulus, endotoxin (lipopolysaccharide [LPS]).

SUMMARY BACKGROUND DATA

HRV reflects fluctuating cardiac autonomic inputs and is acutely reduced during the systemic inflammation induced by LPS as well as during severe critical illnesses such as sepsis and traumatic injury. While EPI may diminish proinflammatory cytokine release, it is unknown whether this net anti-inflammatory activity extends to HRV.

METHODS

Healthy volunteers (n = 17) were randomized to either saline + LPS (2 ng/kg) or LPS + antecedent EPI infusion (30 ng/kg/min) from -3 to 6 hours relative to LPS. HRV and blood samples were obtained before EPI and LPS as well as hourly afterward. Plasma cytokines were measured by ELISA. Statistical analysis was by repeated measures analysis of variance. This study was registered at Clinicaltrials.gov and is listed under the following ID number: NCT00753402.

RESULTS

LPS acutely influenced all measured parameters of HRV including standard deviation of the average beat to beat intervals over a 5-minute period, percentage of interval differences of successive interbeat intervals greater than 50 milliseconds and square root of the mean squared differences, high frequency (HF), low frequency, low frequency/HF, and very low frequency (all P < 0.01). EPI infusion reduced the inflammatory cytokine response to LPS as measured by decreased TNFalpha, IL-6, and IL-8 (P < 0.01). Relative to the saline + LPS group, antecedent EPI infusion was associated with further reductions in parameters of HRV measuring vagal/parasympathetic activity including, percentage of interval differences of successive interbeat intervals greater than 50 milliseconds, square root of the mean squared differences, and HF (P < 0.05).

CONCLUSION

Prior EPI exposure exerts anti-inflammatory influences but also may reduce vagus nerve activity. Hence, acute EPI administration may be protective against early inflammatory challenges but diminish vagal nerve responsiveness to subsequent stimuli.

Acute effects of sildenafil on flow mediated dilatation and cardiovascular autonomic nerve function in type 2 diabetic patients

BACKGROUND

Sildenafil, frequently used as on demand medication for the treatment of erectile dysfunction (ED), has been suggested to improve endothelial function but also to alter blood pressure (BP) and induce sympathetic activation. In people with type 2 diabetes mellitus (T2DM), a high-risk population, the safety profile and the effects on endothelial function of a maximal sildenafil dose (100 mg) have not been investigated and therefore constituted the aim of our study.

METHODS

A double-blind, placebo-controlled, cross-over trial using a single dose of 100 mg sildenafil or placebo has been conducted in 40 subjects with T2DM without known CVD. Haemodynamic parameters, flow mediated dilatation (FMD) in brachial artery, cardiovascular autonomic function tests and spontaneous baroreflex sensitivity (BRS) were measured.

RESULTS

Sixty minutes after administration of sildenafil but not placebo, a fall of supine systolic blood pressure (SBP) (-5.41 +/- 1.87 vs. + 0.54 +/- 1.71 mmHg) and diastolic blood pressure (DBP) (-4.46 +/- 1.13 vs. + 0.89 +/- 0.94 mmHg), as well as orthostatic SBP (-7.41 +/- 2.35 vs. + 0.94 +/- 2.06 mmHg) and DBP (-5.65 +/- 1.45 vs. + 1.76 +/- 1.00 mmHg) during standing occurred, accompanied by an increase in heart rate (+1.98 +/- 0.69 vs. - 2.42 +/- 0.59 beats/min) (all p < 0.01 vs. placebo). Changes in BP to standing up, FMD, time domain and frequency domain indices of heart rate variability (HRV) and BRS were comparable between sildenafil and placebo.

CONCLUSIONS

Sildenafil administered at a maximum single dose to T2DM men results in a mild increase in heart rate and decrease in BP, but it induces neither an acute improvement of FMD nor any adverse effects on orthostatic BP regulation, HRV and BRS.

Cardiac and autonomic nerve function after reduced-intensity stem cell transplantation for hematologic malignancy in patients with pre-transplant cardiac dysfunction

Recent reports have shown that cardiomyopathy caused by hemochromatosis in severe aplastic anemia is reversible after reduced-intensity allogeneic stem-cell transplantation (RIST). We comprehensively evaluated cardiac and autonomic nerve function to determine whether cardiac dysfunction due to causes other than hemochromatosis is attenuated after RIST. In five patients with cardiac dysfunction before transplant, we analyzed the changes in cardiac and autonomic nerve function after transplant, using electrocardiography (ECG), echocardiography, radionuclide angiography (RNA), serum markers, and heart rate variability (HRV), before and up to 100 days after transplant. There was no significant improvement in cardiac function in any patient and no significant alteration in ECG, echocardiogram, RNA, or serum markers. However, on time-domain analysis of HRV, the SD of normal-to-normal RR intervals (SDNN) and the coefficient of variation of the RR interval (CVRR) decreased significantly 30 and 60 days after transplant (P = 0.04 and 0.01, respectively). Similarly, on frequency-domain analysis of HRV, low and high frequency power (LF and HF) significantly and temporarily decreased (P = 0.003 and 0.03, respectively). Notably, in one patient who had acute heart failure after transplantation, the values of SDNN, CVRR, r-MSSD, LF, and HF at 30 and 60 days after transplantation were the lowest of all the patients. In conclusion, this study suggests that (a) RIST is well-tolerated in patients with cardiac dysfunction, but we cannot expect improvement in cardiac dysfunction due to causes other than hemochromatosis; and (b) monitoring HRV may be useful in predicting cardiac events after RIST.

Short-term heart rate variability in healthy young adults: the Cardiovascular Risk in Young Finns Study

Reduced short-term heart rate variability (HRV) is a risk factor for cardiovascular morbidity and total mortality. The reference values of short-term HRV indices in healthy young adults are unknown. To investigate age and sex differences in HRV and to generate reference values of short-term recordings, we examined 1780 healthy subjects aged 24 to 39 years. Both frequency and time domain HRV indices were computed. Indices included; low frequency (LF), high frequency (HF) and total components of spectral-HRV, the square root of mean squared differences of R-R-intervals and SD of normal R-R-intervals. Deep breathing test was performed and the mean ratio of R-R-intervals and the mean difference in instantaneous heart rate during breathing cycle were analyzed. Reproducibility of these indices was studied in 43 subjects. Aging and higher heart rate were inversely associated with all HRV indices (all p values <0.0001). Women had higher HF and lower LF compared to men (both p<0.0001). Women had higher resting heart rate (70 vs. 65 bpm, p<0.0001). The reproducibility of HRV indices and deep breathing test were good (CV 5.3-13.9%). We conclude that age, sex and heart rate needs to be considered when evaluating HRV indices and when generating reference values. Because of good reproducibility the short-term indices of HRV and deep breathing test can be used in clinical work.

Cardiac autonomic diabetic neuropathy

Cardiovascular autonomic diabetic neuropathy (CADN) is one of the most common diabetes-associated complications. Disturbed heart rate variability (HRV) is very often the earliest symptom, even in clinically asymptomatic patients. The following article offers a topical overview for those working or interested in the fields of diabetology and cardiology.

Heart rate variability in depressed elderly

OBJECTIVE

The present study examines a measure of cardiac autonomic function, the heart rate variability (HRV), in a group of depressed elderly. Cardiac autonomic abnormalities have been implicated as a potential mediator of cardiovascular events and sudden death in depression. Because aging is associated with decreased cardiac vagal activity, it is possible that autonomic abnormalities are even more pronounced in the older depressed patients.

DESIGN

Cross-sectional comparison between those with or without depression. The groups were compared using the Wilcoxon matched-pair sign-rank test.

SETTING

Advanced Center for Interventions and Services Research for Late-Life Mood Disorders at University of Pittsburgh Medical Center.

PARTICIPANTS

Fifty-three patients with major depression (mean age: 73.3; SD: 7.4; range: 60-93) and an equal number of age and gender-matched subjects as a comparison group.

INTERVENTION

None.

MEASUREMENTS

Time domain and frequency domain measures of HRV.

RESULTS

The groups did not differ in any of the time domain or frequency domain measures of HRV. As expected, subjects without depression displayed decreasing cardiac vagal function with aging (Spearman correlation coefficient r(s) = -0.33, p = 0.02). However, there was no significant change in vagal function with age in the depressed (r = 0.12, p= 0.38). Post-hoc analysis using Fisher's z(r) transformation revealed that the relationship between age and cardiac vagal function was significantly different between the groups (z = 2.32, p = 0.02).

CONCLUSIONS

Our findings suggest that age has differential influence on vagal function in individuals with and without depression, a difference with implications for cardiovascular disease risk in depression. Prospective studies of cardiac vagal activity in depressed patients with or without preexisting cardiac disease in different age groups are needed to replicate and extend these findings.

Increased vagal modulation in atopic dermatitis

BACKGROUND

Atopic dermatitis has been shown to be associated with neurogenic and psychosocial factors. In related atopic diseases such as rhinitis or asthma, a shift in autonomic balance towards a parasympathetic modulation has been described. On the other hand, the psychiatric symptoms known for atopic dermatitis are often associated with decreased vagal modulation. Furthermore, an increased parasympathetic activity has been shown to exhibit anti-inflammatory effects, thus rather alleviating dermatitis symptoms.

OBJECTIVE

In order to address these intriguing discrepancies, we aimed to assess the autonomic state in patients suffering from atopic dermatitis.

METHODS

Heart rate variability assessment was performed in 30 patients and data were compared to those obtained from matched controls. Furthermore, questionnaires for disease activity and psychosocial stressors were employed.

RESULTS

Patients showed higher values for parasympathetic modulation than controls. This was mainly reflected by an increase in the root mean square of successive differences (RMSSD). This parameter further correlated with dermatological symptoms and the time since the last severe exacerbation of the disease. In addition, subgroups of patients with dyshidrosis or photophobia showed significant differences in autonomic modulation under deep respiration. Moreover, cardiac autonomic modulation was hardly altered upon postural change, indicating that autonomic reactivity is only mildly influenced in these patients.

CONCLUSION

Patients with atopic dermatitis showed an autonomic dysbalance which is comparable to other diseases related to atopy or allergy. Our findings point to the question whether these alterations are disease-inherent or counter-regulatory, which should be addressed in future studies.

Cardiovagal modulation upon postural change is altered in Huntington's disease

BACKGROUND

Cardiac autonomic nervous system (ANS) dysfunction in Huntington's disease (HD) might affect both the sympathetic and parasympathetic branch of the ANS.

RESULTS AND CONCLUSIONS

The pattern of linear heart rate variability we found in mid stage HD patients points towards a predominately reduced cardiovagal modulation compared with healthy subjects, which might influence HD patients' susceptibility for cardiovascular complications such as syncopes and cardiac arrhythmias.

Upper abdominal symptoms in patients with Type 1 diabetes: unrelated to impairment in gastric emptying caused by autonomic neuropathy

AIMS

Diabetic gastroparesis is a common condition occurring in some 30-50% of patients with long-term diabetes. Some studies have found a relationship between autonomic neuropathy and diabetic gastroparesis. In addition to autonomic neuropathy, acute changes in plasma glucose concentration can also affect gastric emptying. The objective was to examine the relationship between autonomic nerve function, glucose concentration, gastric emptying, and upper abdominal symptoms in Type 1 diabetic patients.

METHODS

Gastric emptying of solids and liquids was measured with scintigraphy in 27 patients with longstanding Type 1 diabetes with upper abdominal symptoms. Autonomic nerve function was examined by standardized cardiovascular tests, and plasma glucose concentrations were measured during scintigraphy. Severity of abdominal symptoms and quality of life were explored by validated questionnaires.

RESULTS

Seven patients (26%) had delayed gastric emptying of solids and three (11%) of liquids. Mean gastric half-emptying time of solids was 128 +/- 116 min and of liquids 42 +/- 30 min. Of the 26 patients undergoing tests, 16 (62%) had autonomic nerve dysfunction. Autonomic neuropathy score (1.6 +/- 1.7) correlated positively with the gastric emptying rate of solids (P = 0.006), a rate unrelated to symptom scores or plasma glucose concentrations during scintigraphy. Quality of life in patients with abdominal symptoms was lower than in the normal Finnish population.

CONCLUSIONS

Impaired gastric emptying of solids in patients with Type 1 diabetes is related to autonomic neuropathy, but not to actual glycaemic control. The upper abdominal symptoms observed in these patients cannot be explained, however, by impaired gastric emptying.

Relationship between cardiovagal modulation and psychotic state in patients with paranoid schizophrenia

Disturbed autonomic nervous system (ANS) function in schizophrenia might contribute to increased cardiovascular mortality. We obtained heart rate variability indices from 40 unmedicated schizophrenic patients and 58 matched controls. Mainly we found that patients displaying stronger psychotic symptoms as assessed by the Brief Psychiatric Rating Scale exhibit more severe cardiac ANS disturbances compared with controls.

Heart rate variability and pain: associations of two interrelated homeostatic processes

Between-person variability in pain sensitivity remains poorly understood. Given a conceptualization of pain as a homeostatic emotion, we hypothesized inverse associations between measures of resting heart rate variability (HRV), an index of autonomic regulation of heart rate that has been linked to emotionality, and sensitivity to subsequently administered thermal pain. Resting electrocardiography was collected, and frequency-domain measures of HRV were derived through spectral analysis. Fifty-nine right-handed participants provided ratings of pain intensity and unpleasantness following exposure to 4 degrees C thermal pain stimulation, and indicated their thresholds for barely noticeable and moderate pain during three exposures to decreasing temperature. Greater low-frequency HRV was associated with lower ratings of 4 degrees C pain unpleasantness and higher thresholds for barely noticeable and moderate pain. High-frequency HRV was unrelated to measures of pain sensitivity. Findings suggest pain sensitivity is influenced by characteristics of a central homeostatic system also involved in emotion.

Autonomic function testing in children and adolescents with diabetes mellitus

Cardiac autonomic neuropathy (CAN) is a common complication in type 1 diabetes mellitus (T1DM) and associated with an increased mortality. Early detection of CAN would be desirable for a better individual risk stratification. The aim of this study was to determine whether autonomic dysfunction can be diagnosed in young patients with a recent history of T1DM. Autonomic function was assessed in 20 pediatric patients with T1DM, aged 10-19 yr, and a control group of 136 non-diabetic patients using four cardiorespiratory reflexes: heart rate and blood pressure response in standing position, deep breathing, and Valsalva maneuver. Furthermore, power spectral analyses of the low- and high-frequency band of heart rate variability (HRV) and baroreflex sensitivity (BRS) were tested with the non-invasive Task force monitor (CNSystems, Graz, Austria). Cardiorespiratory reflexes were pathologic for at least one item in 75% of the diabetic and 60% in the healthy control group. A reduced BRS was always combined with abnormal HRV. We found this pattern in 30% of diabetic patients and never in the control group. In patients with impaired BRS, mean hemoglobin A1c (HbA1c) was 7.7% and duration of diabetes 6.5 yr. This did not differ from the overall value of the diabetic group: HbA1c level 8.4% and diabetes duration 7.3 yr. In conclusion, signs of autonomic dysfunction are not uncommon in an early stage of diabetes in young patients. Classical cardiorespiratory reflexes seem to be less specific than HRV and BRS as testing methods.

Heart rate variability: impact of differences in outlier identification and management strategies on common measures in three clinical populations

Heart rate variability (HRV) is reported increasingly in pediatric research, but different strategies used to identify and manage potential outlier beats impact HRV parameter values in adults and animals. Do they in pediatrics? To compare the impact of different strategies to identifying and managing outliers, we used interbeat interval (IBI) data from three different populations: 10 stable premature infants, 33 stable pediatric oncology patients, and 15 healthy adults. Five commonly reported HRV parameters were compared using three identification and two management strategies to filter potential outliers. The three populations had different resting heart rates: 155 +/- 9 beats per minute (bpm) in infants, 105 +/- 17 bpm in children, and 87 +/- 12 bpm in adults. All three identification strategies flagged fewer than 2% of IBIs; the threshold identification strategy, excluding IBIs denoting heart rates <30 or >300 bpm, identified significantly fewer outliers than the other two strategies and generated higher HRV parameters in all populations (p < 0.001). There were no significant differences in HRV parameters calculated by managing identified outliers by "tossing" them versus "interpolating" values. Different strategies for identifying potential outliers are associated with significant differences in HRV parameters. Pediatric researchers who report HRV should detail their outlier filtering strategies.

Role of genetic and environmental influences on heart rate variability in middle-aged men

Our aim was to estimate causal relationships of genetic factors and different specific environmental factors in determination of the level of cardiac autonomic modulation, i.e., heart rate variability (HRV), in healthy male twins and male twins with chronic diseases. The subjects were 208 monozygotic (MZ, 104 healthy) and 296 dizygotic (DZ, 173 healthy) male twins. A structured interview was used to obtain data on lifetime exposures of occupational loading, regularly performed leisure-time sport activities, coffee consumption, smoking history, and chronic diseases from 12 yr of age through the present. A 5-min ECG at supine rest was recorded for the HRV analyses. In univariate statistical analyses based on genetic models with additive genetic, dominance genetic, and unique environmental effects, genetic effects accounted for 31–57% of HRV variance. In multivariate statistical analysis, body mass index, percent body fat, coffee consumption, smoking, medication, and chronic diseases were associated with different HRV variables, accounting for 1–11% of their variance. Occupational physical loading and leisure-time sport activities did not account for variation in any HRV variable. However, in the subgroup analysis of healthy and diseased twins, occupational loading explained 4% of the variability in heart periods. Otherwise, the interaction between health status and genetic effects was significant for only two HRV variables. In conclusion, genetic factors accounted for a major portion of the interindividual differences in HRV, with no remarkable effect of health status. No single behavioral determinant appeared to have a major influence on HRV. The effects of medication and diseases may mask the minimal effect of occupational loading on HRV.

Acute effects on heart rate variability when exposed to hand transmitted vibration and noise

OBJECTIVES

This study investigates possible acute effects on heart rate variability (HRV) when people are exposed to hand transmitted vibration and noise individually and simultaneously.

METHODS

Ten male and 10 female subjects were recruited by advertisement. Subjects completed a questionnaire concerning their work environment, general health, medication, hearing, and physical activity level. The test started with the subject resting for 15 min while sitting down. After resting, they were exposed to one of four exposure conditions: (1) only vibration; (2) only noise; (3) both noise and vibration; or (4) a control condition of exposure to the static load only. All four exposures lasted 15 min and the resting time between the exposures was 30 min. A continuous electrocardiogram (ECG) signal was recorded and the following HRV parameters were calculated: total spectral power (P(TOT)); the spectral power of the very low frequency component (P(VLF)); the low frequency component (P(LF)); the high frequency component (P(HF)); and the ratio LF/HF.

RESULTS

Exposure to only vibration resulted in a lower P(TOT) compared to static load, whereas exposure to only noise resulted in a higher P(TOT). The mean values of P(TOT), P(VLF), P(LF), and P(HF) were lowest during exposure to vibration and simultaneous exposure to vibration and noise.

CONCLUSIONS

Exposure to vibration and/or noise acutely affects HRV compared to standing without these exposures. Being exposed to vibration only and being exposed to noise only seem to generate opposite effects. Compared to no exposure, P(TOT) was reduced during vibration exposure and increased during noise exposure.

Size at birth and autonomic function during psychological stress

Small size at birth is associated with exaggerated blood pressure responses to psychological stressors, which increase the risk of developing sustained hypertension in adult life. Explanatory mechanisms for this association are not well characterized. We investigated the hypothesis that an adverse fetal environment, reflected by small size at birth, persistently alters autonomic nervous system and baroreflex control of cardiovascular function, resulting in exaggerated blood pressure and heart rate responses to stressors. Men and women from an Australian prospective cohort study underwent a series of 3 psychological stressors (Stroop, mirror-tracing, and speech) while their blood pressure was recorded continuously using a Portapres. Indices of autonomic function were derived using spectrum analysis (wavelet packet transform), and baroreflex function was estimated using an adaptive autoregressive model. We found that women who were small at birth demonstrated increased levels of low-frequency blood pressure variability at rest (r=-0.28; P<0.05) and during stress (r=-0.42; P<0.001), reduced levels of high-frequency heart period variability (r=0.22; P<0.05), and reduced baroreflex sensitivity (r=0.34; P<0.01). These findings were not present in the men. This study provides evidence that markers of impaired fetal growth are related to autonomic cardiovascular control involving modulation of both sympathetic and parasympathetic function but in a sex-specific manner. We also provide the first human evidence of a relationship between size at birth and baroreflex function.

Inter- and Intra-Individual Variations of Heart Rate Variability in Japanese Males

Spectral components of heart rate variability (HRV) were repeatedly measured (4-8 measurements; mean: 6 measurements) in 75 healthy Japanese male subjects (age range: 20-61) under two postural conditions (standing and supine). Low-frequency (LF) and high-frequency (HF) components and mean heart rate (HR) were analyzed with special reference to individual variations, which were classified into two types: inter- (interV) and intra-individual variations (intraV). The percent contributions and coefficients of variations were calculated for both interV and intraV. Percent contributions of intraV (intraV%) of HR with standing and supine postures were 15.8 and 12.9%, respectively. The intraV% of HF and LF on standing were 31.5 and 26.5%, while those in the supine posture were 27.8 and 35.5%, respectively. The coefficients of interV (interCV) and intraV (intraCV) were also calculated. The interCVs of HR, HF, and LF on standing were 14.9, 41.4, and 48.4%, while those in the supine posture registered 16.2, 42.9, and 44.2%, respectively. The intraCVs of HR, HF, and LF on standing were 5.0, 19.7, and 21.2%, while those in the supine posture indicated 4.7, 20.1, and 23.0%, respectively. We also calculated the interV and intraV of logarithmic-transformed HRV indexes. The log-transformation remarkably diminished both variables: interCV and intraCV registered 14-16 and 6-7%, respectively. Although interV variations were considerably large, intraV variations of HRV were negligibly small. The HRV indexes decreased with age, although HR remained unchanged. The coefficients of determination (r2) were 14-34%. In the case of log-transformed HRV indexes, the coefficients of determination registered 9-15%, suggesting that 14-34% (raw) or 9-15% (log) of the observed interV may be due to variations in age.

Cardiac autonomic function in chagasic elderly patients in an endemic area: A time and frequency domain analysis approach

Chagas' disease is a common cause of cardiac autonomic impairment. In an endemic area there is a predominance of the indeterminate form and the number of elderly individuals committed by the disease is increasing. This study aimed to investigate the profile of heart rate variability (HRV) in elderly chagasic patients. 28 aged chagasic (CH), 28 non-chagasic (NC) aged individuals and 28 adults between 20 and 40 years old (YG) were studied. R-R intervals were assessed in time and frequency domains applying an autoregressive algorithm. There was no difference regarding temporal and spectral indices among the elderly groups in baseline. The values of the variance in CH, NC and YG individuals were 891.80, 283.60, 2557.00, showing a reduction of the total HRV in the aged groups when compared to the young control (p < 0.001). During the cold face test, the pNN50 response was significantly different only in the young group (p < 0.001). The temporal and spectral indices were not different among the elderly groups. The percentile changes of the R-R intervals induced by the tilt test in CH, NC and YG were respectively -7.04%, -9.35%, -15.81%, being significantly higher in the young individuals (p < 0.001). There was no difference regarding the percentile changes of the temporal and spectral indices between CH and NC elderly patients. The cardiac autonomic function assessed by HRV parameters presented no differences among the elderly individuals (CH and NC) living in an endemic area.

Heart rate variability biofeedback: effects of age on heart rate variability, baroreflex gain, and asthma

OBJECTIVES

To present additional analysis of data from a previously published study showing that biofeedback training to increase heart rate variability (HRV) can be an effective component in asthma treatment. HRV and intervention-related changes in HRV are negatively correlated with age. Here we assess the effects of age on biofeedback effects for asthma.

DESIGN

Ten sessions of HRV biofeedback were administered to 45 adults with asthma. Medication was prescribed by blinded physicians according to National Heart, Lung, and Blood Institute criteria. Medication needs were reassessed biweekly.

RESULTS

Decreases in need for controller medication were independent of age. There were larger acute decreases in forced oscillation frequency dependence in the older group but larger increases in HRV variables in the younger group. Differences between age groups were smaller among subjects trained in pursed-lips abdominal breathing as well as biofeedback, than among those receiving only biofeedback.

CONCLUSIONS

Age-related attenuation of biofeedback effects on cardiovascular variability does not diminish the usefulness of the method for treating asthma among older patients. Additional training in pursed-lips abdominal breathing obliterates the effects of age on HRV changes during biofeedback.

Preliminary evidence of parasympathetic influence on basal heart rate in posttraumatic stress disorder

OBJECTIVE

Evidence of elevated basal heart rate (HR) in posttraumatic stress disorder (PTSD) has been interpreted in terms of elevated sympathetic cardiac activity, as have possible increased cardiovascular disease risks and outcomes associated with elevated HR. Yet it is well-established that the parasympathetic branch of the autonomic nervous system not only influences HR independently of the sympathetic branch, but makes a greater contribution to HR, including resting HR. Additionally, abnormally low tonic parasympathetic activity on the heart has been implicated in cardiovascular disease and hypertension. This study addressed a potential parasympathetic contribution to elevated basal HR in PTSD.

METHODS

We used a descriptive and subgroup differences approach to investigate relationships between parasympathetic activity and basal HR in 59 adults (50 females) with PTSD, all of whom were participants in a treatment outcome study and assessed prior to exposure to trauma-related script-driven imagery. Consistent with the well-known relationship between parasympathetic activity and HR, we hypothesized that basal respiratory sinus arrhythmia (RSA), a measure of parasympathetic cardiac activity, would be negatively correlated with basal HR. More important, we predicted that pathologically elevated HRs previously associated with PTSD would only characterize a low-RSA subgroup. Potential confounds of age, respiration rate, and aerobic fitness were addressed.

RESULTS

As predicted, mean HR was 80.5 bpm in the low-RSA tercile group, similar to mean HRs of PTSD groups in prior research and significantly higher than 69 and 65 bpm in the middle- and high-RSA groups, respectively, which are typical of non-PTSD controls.

CONCLUSION

These findings suggest that a substantial proportion of those with PTSD may not have elevated basal HRs. Furthermore, among those who do exhibit elevated HR, there may be a parasympathetic contribution that is independent of any sympathetic one. Only measuring both branches at once, ideally with autonomic blockades, can definitively address these issues.

Cardiovascular disease, risk factors and heart rate variability in the elderly general population: design and objectives of the CARdiovascular disease, Living and Ageing in Halle (CARLA) Study

Background

The increasing burden of cardiovascular diseases (CVD) in the ageing population of industrialized nations requires an intensive search for means of reducing this epidemic. In order to improve prevention, detection, therapy and prognosis of cardiovascular diseases on the population level in Eastern Germany, it is necessary to examine reasons for the East-West gradient of CVD morbidity and mortality, potential causal mechanisms and prognostic factors in the elderly.

Psychosocial and nutritional factors have previously been discussed as possible causes for the unexplained part of the East-West gradient. A reduced heart rate variability appears to be associated with cardiovascular disease as well as with psychosocial and other cardiovascular risk factors and decreases with age. Nevertheless, there is a lack of population-based data to examine the role of heart rate variability and its interaction with psychosocial and nutritional factors regarding the effect on cardiovascular disease in the ageing population. There also is a paucity of epidemiological data describing the health situation in Eastern Germany. Therefore, we conduct a population-based study to examine the distribution of CVD, heart rate variability and CVD risk factors and their associations in an elderly East German population. This paper describes the design and objectives of the CARLA Study.

Methods/design

For this study, a random sample of 45–80 year-old inhabitants of the city of Halle (Saale) in Eastern Germany was drawn from the population registry. By the end of the baseline examination (2002–2005), 1750 study participants will have been examined. A multi-step recruitment strategy aims at achieving a 70 % response rate.

Detailed information is collected on own and family medical history, socioeconomic, psychosocial, behavioural and biomedical factors. Medical examinations include anthropometric measures, blood pressure of arm and ankle, a 10-second and a 20-minute electrocardiogram, a general physical examination, an echocardiogram, and laboratory analyses of venous blood samples. On 200 participants, a 24-hour electrocardiogram is recorded. A detailed system of quality control ensures high data quality. A follow-up examination is planned.

Discussion

This study will help to elucidate pathways to CVD involving autonomic dysfunction and lifestyle factors which might be responsible for the CVD epidemic in some populations.

Regular physical exercise, heart rate variability and turbulence in a 6-year randomized controlled trial in middle-aged men: The DNASCO study

HRV and HRT are independent predictors of cardiovascular mortality. Aging reduces HRV, but results from the physical exercise trials are controversial. The primary aim was to study changes in heart rate variability (HRV) and heart rate turbulence (HRT) in a six-year controlled randomized trial at regular low to moderate intensity physical exercise. One hundred forty men aged 53--63 years were randomized in to an exercise or a control groups. The participants underwent a maximal bicycle ergometer exercise test with respiratory gas analyses annually for six years. At baseline and after intervention, 24-h ambulatory ECG registrations were performed to assess HRV (n=100). HRT was determined among subjects with single ventricular premature complexes (VPC) (n=73). In the exercise group, ventilatory aerobic threshold (VAT) increased by 16% indicating enhanced submaximal cardiorespiratory fitness. No significant differences were found in any of the HRV or HRT parameters between the groups. However, the observed increase in VAT correlated significantly with the improvement in HRV parameters. The change in turbulence slope (TS) correlated with the changes in most HRV variables and the change in turbulence onset (TO) correlated with the changes in three frequency domain parameters. Our results suggest that in addition to improvement in submaximal cardiorespiratory fitness, regular low to moderate intensity physical exercise seems to have beneficial effects also on cardiac autonomic nervous function, a clinically relevant predictor of cardiovascular morbidity and mortality.

Reliability of heart rate variability in healthy older women at rest and during orthostatic testing

BACKGROUND AND AIMS

In the older population, the reliability of heart rate variability (HRV) has only been evaluated in a few studies, in the supine position, and covering a broad sample of age and patients of both sexes. To document the relevance of using HRV analysis in healthy older women, the aim of this study was to evaluate the reliability of HRV indexes during three classical tests.

METHODS

33 healthy women (66.9+/-0.7 years old) performed two test sessions. Each session consisted of an ECG recorded in the supine position, first with free breathing (Test 1), then with controlled breathing (Test 2), and in the upright position (Test 3). Time and frequency HRV indexes were obtained by processing the ECG signals. Reliability was assessed between sessions using Student's paired t-test, intraclass correlation coefficient (ICC) and coefficient of variation (CV).

RESULTS

There were no differences between the sessions. ICC showed good reliability for all HRV indexes. CV was low for absolute HRV indexes, except in Test 3 for parasympathetic indexes with modest CV. The CV of HRV ratio indexes were modest to high in all three tests.

CONCLUSIONS

Time and absolute frequency HRV indexes are reliable when testing healthy older women. Our results support the use of such indexes in gerontology research, to assess the effects of clinical or pharmacological interventions on the autonomic nervous system.

Comparison of the effects of propofol and midazolam on the cardiovascular autonomic nervous system during combined spinal and epidural anesthesia

STUDY OBJECTIVE

To investigate the effect of propofol and midazolam on cardiac autonomic nervous system (CANS) activity during combined spinal-epidural anesthesia.

DESIGN

Prospective, clinical study.

SETTING

Operating room of a university hospital.

PATIENTS

Forty ASA physical status I and II patients scheduled for knee surgery.

INTERVENTION

Patients were randomized to receive sedation with either propofol or midazolam.

MEASUREMENTS

Heart rate (HR), HR variability (HRV), systolic arterial pressure (SAP), and SAP variability (SAPV) were used for the analysis. These values were measured at the preanesthetic period, after intrathecal injection for spinal anesthesia, after sedation with propofol or midazolam, and just before the end of surgery with sedation. Cross-spectral analyses of the HR and SAP data were assessed to quantify the frequency-related coherence spectra and phase spectra.

MAIN RESULTS

Spinal anesthesia itself had no effect on power spectral changes in both groups. After sedation, as for HRV, high-frequency (HF) power (HF, 0.15-0.40 Hz) did not change, whereas low-frequency (LF) power (LF, 0.04-0.15 Hz) and LF/HF, an indicator of CANS balance, significantly decreased with propofol. Further, coherence in cross-spectra presented depression in the LF band area after sedation with propofol. Before the end of surgery with sedation, LF and LF/HF in both HRV and SAPV were correlated with age in those with propofol; however, scarce relation was observed in those who received midazolam.

CONCLUSIONS

Propofol was more potent than midazolam in causing CANS activity to be sympatholytic during combined spinal and epidural anesthesia and which was correlated with age only with propofol.

Disparity of autonomic control in type 2 diabetes mellitus

AIMS/HYPOTHESIS

Acute insulinaemia activates the sympathetic drive in a nonuniform manner. The extent and nature of such activation in type 2 diabetic patients who do not have neuropathy have not yet been addressed despite evidence relating sympathetic activation to cardiovascular risk. We planned to determine the magnitude and extent of the sympathetic drive and its reflex responses in patients with type 2 diabetes and fasting hyperinsulinaemia.

METHODS

We measured resting muscle sympathetic nerve activity (MSNA) as the mean frequency of multi-unit bursts and single unit muscle sympathetic nerve activity (s-MSNA) in 17 overweight patients with type 2 diabetes and two matched normal control groups comprising 17 overweight and 16 normal-weight subjects. We also tested the MSNA and s-MSNA responses to cold pressor and isometric hand-grip tests, along with the effect of sympatho-vagal balance on heart period variability.

RESULTS

Both MSNA and s-MSNA in the group with type 2 diabetes (66+/-3.5 bursts/100 beats and 78+/-4.5 impulses/100 beats) were greater (at least p<0.0001) than in the overweight control group (42+/-2.6 bursts/100 beats and 48+/-3.4 impulses/100 beats) and normal-weight control group (43+/-6.2 bursts/100 beats and 51+/-7.1 impulses/100 beats), though the three groups had similar reflex responses, baroreflex sensitivity and sympatho-vagal balance controlling the heart period.

CONCLUSIONS/INTERPRETATION

The patients with type 2 diabetes had no evidence of impaired reflex or autonomic control of heart period variability at a time when there was central sympathetic activation to the periphery. Furthermore, being overweight itself was not associated with sympathetic activation.

Sympathetic and parasympathetic neuropathy are frequent in both type 1 and type 2 diabetic patients

OBJECTIVE

The aim of this study was to evaluate the frequency of sympathetic versus parasympathetic neuropathy among type 1 and type 2 diabetic patients.

RESEARCH DESIGN AND METHODS

There were 43 patients with type 1 and 17 with type 2 diabetes who were investigated. Sympathetic nerve function was assessed by measurement of the vasoconstriction (VAC) index by laser Doppler perfusion imaging of a locally heated finger followed by indirect cooling. Parasympathetic nerve function was assessed by R-R interval variation during deep breathing as measured by the expiration/inspiration (E/I) ratio. Results were expressed as age-corrected z scores in SD; VAC index >1.64 SD and E/I ratio <-1.64 SD were considered abnormal.

RESULTS

VAC index was abnormal in 40% with type 1 and 41% with type 2 diabetes, whereas the E/I ratio was abnormal in 42% with type 1 and 65% with type 2 diabetes. There was a clear association between VAC index and E/I ratio among type 1 (rs=0.525; P=0.0002) but not among type 2 (rs=0.10) diabetic patients. Among type 2 diabetic patients, the degree of dysfunction was most severe regarding parasympathetic function (P=0.0167).

CONCLUSIONS

Sympathetic and parasympathetic neuropathy were frequent in both type 1 and type 2 diabetic patients. However, there was a difference between the two types of diabetes. Sympathetic and parasympathetic nerve functions correlated in type 1 but not in type 2 diabetic patients. The explanation for this discrepancy might be that parasympathetic nerve function was most severely affected among type 2 diabetic patients.

Physical training and heart rate and blood pressure variability: a 5-yr randomized trial

We studied the effect of regular physical activity on cardiac and vascular autonomic modulation during a 5-yr controlled randomized training intervention in a representative sample of older Finnish men. Heart rate variability (HRV) and blood pressure variability (BPV) are markers of cardiac and vascular health, reflecting cardiac and vascular autonomic modulation. One hundred and forty randomly selected 53- to 63-yr-old men were randomized into two identical groups: an intervention (EX) group and a reference (CO) group, of which 89 men remained until the final analysis (EX: n = 47; CO: n = 42). The EX group trained for 30–60 min three to five times a week with an intensity of 40–60% of maximal oxygen consumption. The mean weekly energy expenditure of the training program for the 5-yr training period was 3.80 MJ, and 71% of the EX group exceeded the mean. The EX group had a significantly ( P < 0.01) higher oxygen consumption at ventilatory aerobic threshold (V̇o2VT) than the CO group at the 5-yr time point. V̇o2VT had a tendency to increase in the EX group and decrease in the CO group (interaction P < 0.001) from the baseline to the 5-yr time point. Peak performance did not change. Low-frequency power of R-R interval variability decreased in the EX group ( P < 0.01, by 6%) from the baseline to the 5-yr time point. BPV did not change. In conclusion, low-intensity regular exercise training did not prevent HRV from decreasing or change BPV in 5 yr in older Finnish men.

Low respiratory sinus arrhythmia and prolonged psychophysiological arousal in posttraumatic stress disorder: heart rate dynamics and individual differences in arousal regulation

BACKGROUND

There is extensive evidence that the parasympathetic branch of the autonomic nervous system can modulate psychophysiological arousal. To date, no studies have investigated associations between cardiac vagal tone and the time course of arousal during exposure to trauma-related stimuli in posttraumatic stress disorder (PTSD).

METHODS

Thirty-one subjects, 29 with PTSD and 2 with partial PTSD, had electrocardiograms recorded during baseline and 2-minute traumatic and neutral script-driven imagery periods. Heart rate, respiratory sinus arrhythmia (RSA), and heart rate half-recovery to the trauma script were quantified, and subjects were divided into low and high baseline RSA groups.

RESULTS

Across all participants, heart rate significantly increased from the neutral to the trauma script and RSA significantly decreased from baseline to trauma script (p < .05). As predicted, low RSA subjects had more prolonged heart rate increases to the trauma script than high RSA subjects (p < .001), and heart rate half-recovery was negatively correlated to baseline RSA (r = -.50, p =.005).

CONCLUSIONS

This study is the first to find decreased RSA in response to a traumatic reminder and an association between low baseline RSA and sustained conditioned arousal in PTSD. Low vagal tone may account for deficient arousal and emotion regulation capacities often observed in PTSD.

Análise temporal da variabilidade da freqüência cardíaca no estado basal em idosos chagásicos na forma indeterminada em área endêmica

Com o objetivo de avaliar a função autonômica cardíaca em pacientes chagásicos residentes em área endêmica, foram avaliados, por meio da análise computadorizada da variabilidade da freqüência cardíaca, 28 pacientes idosos chagásicos na forma indeterminada, 28 pacientes idosos não-chagásicos e 28 adultos jovens. Todos os pacientes chagásicos realizaram eletrocardiograma, radiografia de tórax, estudo radiológico contrastado do esôfago e cólons e ecodopplercardiograma, sendo que os não-chagásicos deixaram de realizar apenas os exames contrastados. Não houve diferença estatisticamente significativa entre os grupos, quanto às dimensões sistólica e diastólica e função sistólica do ventrículo esquerdo. Não houve diferença estatisticamente significante entre os grupos, quanto à duração média do intervalo RR. Quanto à variância, desvio padrão, coeficiente de variação, e ao pNN50, houve diferença estatisticamente significante entre o grupo jovem e os idosos, mas não entre os grupos idosos. Concluímos que, no estado basal, os grupos idosos chagásicos e não-chagásicos não diferiram quanto à modulação autonômica cardíaca no domínio do tempo.

Dose-response relationship of the cardiovascular adaptation to endurance training in healthy adults: how much training for what benefit?

Occupational or recreational exercise reduces mortality from cardiovascular disease. The potential mechanisms for this reduction may include changes in blood pressure (BP) and autonomic control of the circulation. Therefore, we conducted the present long-term longitudinal study to quantify the dose-response relationship between the volume and intensity of exercise training, and regulation of heart rate (HR) and BP. We measured steady-state hemodynamics and analyzed dynamic cardiovascular regulation by spectral and transfer function analysis of cardiovascular variability in 11 initially sedentary subjects during 1 yr of progressive endurance training sufficient to allow them to complete a marathon. From this, we found that 1) moderate exercise training for 3 mo decreased BP, HR, and total peripheral resistance, and increased cardiovascular variability and arterial baroreflex sensitivity; 2) more prolonged and intense training did not augment these changes further; and 3) most of these changes returned to control values at 12 mo despite markedly increased training duration and intensity equivalent to that routinely observed in competitive athletes. In conclusion, increases in R-wave-R-wave interval and cardiovascular variability indexes are consistent with an augmentation of vagal modulation of HR after exercise training. It appears that moderate doses of training for 3 mo are sufficient to achieve this response as well as a modest hypotensive effect from decreasing vascular resistance. However, more prolonged and intense training does not necessarily lead to greater enhancement of circulatory control and, therefore, may not provide an added protective benefit via autonomic mechanisms against death by cardiovascular disease.

Are electrophysiological autonomic tests useful in the assessment of dysautonomia in Parkinson's disease?

To assess the autonomic system in Parkinson's disease (PD), the sympathetic skin response (SSR) and the R-R interval variation (RRIV) tests were studied in 26 PD patients and in 24 healthy controls. The aim of the study was to evaluate the sympathetic and parasympathetic system function in PD, to define the pattern of autonomic abnormalities found in SSR and RRIV in parkinsonian patients as well as to analyze the usefulness of both tests in paraclinical assessment of the dysautonomia, compared with clinical symptoms and signs of the autonomic nervous system involvement. The corrrelations between both autonomic tests results were also studied. In PD patients SSR test was abnormal in about 35% and RRIV was abnormal in about 54% of patients. SSR and RRIV were both abnormal in about 27% of PD patients whereas at least one of electrophysiological autonomic tests was abnormal in about 62% of PD patients. Clinical and paraclinical signs of dysautonomia occurred in a similar proportion of patients (i.e. in about 62%). A weak correlation was found between the latency of SSR from upper limbs and the value of RRIV during deep breathing (p=0.063). Our results show that SSR and RRIV are non-invasive paraclinical electrophysiological tests that confirm clinical dysautonomia in PD and can supplement the clinical differentiation of Parkinsonian syndromes.

Relationship between major depression and heart rate variability. Clinical consequences and implications for antidepressive treatment

A high sympathetic and/or a low cardiovagal activity in patients with major depression (MD) may contribute to the higher cardiac morbidity and mortality of MD patients. Standardized tests of heart rate variability (HRV) allow a quantitative estimation of autonomic nervous system function. However, previous studies on the relationship between HRV and MD have revealed conflicting results. Our study compared time and frequency domain HRV indices (5-min resting study, deep breathing test, Valsalva test) between 32 patients with MD (DSM-III-R) and 64 non-depressed controls. The severity of depressive symptoms was assessed by the Hamilton Depression Scale (HAM-D); patients were divided into subgroups with moderate (M-HAM-D<25) or severe depressive symptoms (S-HAM-D>or=25). After controlling for age, gender and smoking, S-HAM-D patients showed a higher heart rate and a significantly lower modulation of cardiovagal activity compared to controls. Although some of the HRV indices of the M-HAM-D group did not differ significantly from controls, they were in the expected direction. There was a significantly negative correlation between the HAM-D scores and the vagal HRV indices, suggesting a direct association between the severity of depressive symptoms and the modulation of cardiovagal activity. Clinical consequences arising from these findings and possible implications for treatment are discussed.

Autonomic nervous system function in Huntington's disease

OBJECTIVE

To investigate whether Huntington's disease (HD) affects autonomic nervous system (ANS) functioning.

METHODS

Twenty patients with HD who had positive genetic test results underwent standardised ANS function tests including sympathetic skin responses (SSRs) of the hands and feet, measurements of heart rate variability (HRV), both during five minutes of resting and deep respiration, and an orthostatic blood pressure test. Patients were classified according to the motor subscale of the unified Huntington's disease rating scale (UHDRS; mean (SD) score 26.4 (13.6)) and divided into two subgroups: UHDRS <25 points (early stages, E-HD) and UHDRS > or =25 points (mid stages, M-HD). Autonomic indices were compared with those obtained for a group of well matched healthy controls (n=60).

RESULTS

Overall, patients showed lower HRV indices than controls. Multivariate analysis with the independent factor of "group" (controls, E-HD, M-HD) showed a significant group effect on both the high frequency power (F=4.32, p=0.017) and the coefficient of variation (F=4.23, p=0.018), indicating a significant reduction in vagal modulation in the M-HD group. There was a shift in autonomic neurocardiac balance towards sympathetic predominance in the M-HD group compared with controls (F=2.89, p=0.062). Moreover, we found an inverse correlation between the severity of clinical HD symptoms (assessed by the UHDRS) and the modulation of cardiovagal activity (p=0.028). Vagal dysregulation was present in two patients; one of them also showed a pathological blood pressure test and a latency prolongation in the SSRs of the hands. Two other patients had pathologically reduced SSR amplitudes. Only patients of the M-HD group were affected.

CONCLUSION

Autonomic dysfunction is present even in the middle stages of HD and affects both the sympathetic and parasympathetic branch of the ANS.

Short-term effects of intravenous benzodiazepines on autonomic neurocardiac regulation in humans: a comparison between midazolam, diazepam, and lorazepam

OBJECTIVES

To evaluate the effects of intravenously applied diazepam, lorazepam, and midazolam on autonomic neurocardiac regulation assessed by standardized measurements of heart rate variability.

DESIGN

Prospective, randomized clinical study.

SETTING

University teaching hospital.

PATIENTS

Forty-five patients, who underwent a gastroscopy, were randomly assigned to intravenous premedication with midazolam (5 mg), diazepam (10 mg), or lorazepam (4 mg). Six subjects refused an injection and served as nonpremedicated controls.

INTERVENTIONS

Serial recordings of the 5-min resting heart rate variability were obtained before and 15 and 30 mins after premedication. Seven benzodiazepine-treated patients received intravenous flumazenil (0.5 mg).

MEASUREMENTS AND MAIN RESULTS

The average doses applied were 0.07 mg/kg for midazolam, 0.13 mg/kg for diazepam, and 0.06 mg/kg for lorazepam. Fifteen minutes after intravenous benzodiazepines were administered, we found an increase in resting heart rate and a reduction of vagal tone compared with baseline in all three benzodiazepine-treated subgroups. Multivariate analysis (covariate age) of the changes in heart rate variability indices over the experimental course revealed a significant reduction in absolute high-frequency power with midazolam or diazepam compared with nonpremedicated subjects. Moreover, midazolam-treated subjects showed a significantly larger reduction in relative high-frequency power not only compared with nontreated subjects, but also compared with lorazepam- or diazepam-treated subjects. Vagal tone remained reduced compared with baseline even 30 mins after benzodiazepine application, however, the resting heart rate decreased toward baseline levels. After flumazenil administration, there was a linear correlation between an increase in high-frequency power and a corresponding decrease in resting heart rate.

CONCLUSIONS

Benzodiazepines can influence autonomic neurocardiac regulation in man, probably through their interaction with the gamma-aminobutyric acidA-receptor chloride ion channel complex. The pattern of findings suggests that intravenous midazolam, diazepam, and lorazepam influence human autonomic neurocardiac regulation in a biphasic way. First, they cause a reduction of central vagal tone, and second, they may decrease the cardiac pacemaker directly. Flumazenil completely abolished the autonomic neurocardiac regulation effects of benzodiazepines.

Effects of endurance training on heart rate and blood pressure variability

PURPOSE

To study the influences of a 1-year controlled, randomized endurance exercise training period on heart rate (HR) and blood pressure variability in a representative sample of Finnish men in their late middle age.

METHODS AND RESULTS

Subjects were 140 sedentary men aged 53-63 years. The men were randomized into two identical groups: an intervention (EX) and a reference (CO) group. One hundred and twelve of them remained in the final analysis (EX: n=59, CO: n=53). EX trained for 30-60 min three to five times a week with the intensity of 40-60% of maximal oxygen consumption. In EX, 1 year of regular exercise training increased oxygen consumption at respiratory compensation threshold by 11% (P < or = 0.001) in a maximal cardiorespiratory test. Total power and very low frequency power of R-R interval variability (ms2) tended to increase in the EX group by 26 and 42% and to decrease in the CO group by 13 and 10% (interaction P<0.05 and P<0.01), respectively. There were no significant changes in blood pressure variability.

CONCLUSION

Regular low- to moderate-intensity exercise training could retard the declining tendency in cardiac autonomic nervous function in older men during 1 year.