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PubMed2004

Short- and long-term reproducibility of autonomic measures in supine and standing positions.

Autonomic nervous tests and heart rate variability (HRV) have been used to assess cardiac autonomic function and to evaluate long-term prognosis. The aim of this study was to evaluate the short- and long-term reproducibility of HRV parameters and autonomic nervous tests according to body position (supine or standing). The study group consisted of 26 healthy subjects. Autonomic nervous tests and HRV were performed twice during the day and the results were averaged. The protocol was then repeated 3 days after each examination and also after 6 and 24 months. Autonomic nervous tests included deep breathing, Valsalva manoeuvre and isometric muscle exercise (handgrip), as well as blood pressure and heart rate in response to standing. ECG recordings were taken for 10 min during spontaneous breathing for HRV analysis. We found that the reproducibility of some parameters of the autonomic nervous test were independent of body position [E/I ratio (heart rate response to deep breathing)], whereas other parameters were dependent on body position (Valsalva manoeuvre and blood pressure response to sustained handgrip). In addition, within-day measurements of those parameters varied from non-reproducible (Valsalva ratio, handgrip and blood pressure response to standing) to moderately reproducible [E/I ratio and 30/15 ratio (heart rate response to standing)]. Among the HRV parameters, we found that total power (TP), low (LF)- and high (HF)-frequency were reproducible not only for measurements made within the same day, but also during short- and long-term observations, and only the LF/HF ratio was dependent on body position. We conclude that only a few autonomic nervous tests are reproducible in the short- and long-term. Because HRV parameters obtained during spontaneous respiration showed high reproducibility for measurements made within the same day as well as in the short- and long-term, they should be used instead of autonomic nervous tests when long-term observations are carried out in a healthy population.

Adult↗
PubMed2001

Heart rate dynamics and cardiorespiratory coordination in diabetic and breast cancer patients.

Objective of this study was to evaluate cardiac autonomic function in female breast cancer patients on the basis of linear and non-linear heart rate variability (HRV) as well as on musical heart rate rhythmicity. The latter method has been recently developed and enables particularly the quantification of cardiorespiratory coordination solely on the basis of ECG recordings. To provide a broad basis of comparability, 37 breast cancer patients were compared with 37 age-matched healthy women and 40 age-matched female diabetic patients who serve as pathological controls. During night sleep, all parameters showed a tendency towards lower variability, complexity or rhythmicity of HRV in cancer patients. The most prominent alterations were found for the binary pattern predominance (PP) and for the ratio of heart rate and respiration. In particular, when comparing metastasized and non-metastasized cancer patients, the discriminatory power of binary heart rate rhythmicity emerges: the histograms of 1-h intervals during night sleep with a predominance of cyclically recurrent phase locking patterns unveiled a clear transition from higher to lower cardiorespiratory coordination ratios and to a loss of coordination capability in metastasized patients.

Adult↗
PubMed2002

Heart rate variability during sleep in children with partial epilepsy.

Alterations in autonomic control of cardiac activity in epileptic patients have been reported by several studies in the past, and both ictal and interictal modifications of heart rate regulation have been described. Alterations of autonomic control of cardiac activity can play an important role in sudden unexplained death in patients with epilepsy (SUDEP). However, the presence of specific changes in heart rate variability (HRV) during sleep, not correlated with seizures, has not been assessed in children with epilepsy; for this reason, we evaluated features of cardiac autonomic function during sleep without ictal epileptiform electroencephalogram (EEG) activity in a group of children with partial epilepsy. Eleven patients (five males and six females; mean age 11.5 years, SD: 3.65 years) affected by partial epilepsy were admitted to this study; 11 normal subjects (five males and six females; mean age 12.9 years, SD: 2.72 years) served as a control group. All subjects slept in the laboratory for two consecutive nights. The data were analyzed during the second night. Sleep was polygraphically recorded [including one electrocardiography (ECG) channel] and signals were digitally stored. A series of 5-min ECG epochs were chosen from each sleep stage, during periods without evident ictal epileptiform activity in the EEG. Electrocardiography signals were analyzed for automatic detection of R-waves and, subsequently, a series of time- and frequency-domain measures were calculated. Epileptic subjects tended to show an overall lower HRV in both time- and frequency-domain parameters, principally during rapid eye movement (REM) sleep and, to a lesser extent, during sleep stage 2. Among the different bands, this decrease was most evident for the high-frequency band (HF) absolute power. For this reason, the ratio between the low-frequency band (LF) and HF was always higher in epileptic patients than in normal controls and the difference was statistically significant during sleep stages 3 and/or 4 and REM sleep. Our results indicate that during sleep, a particular condition of basal modification in autonomic characteristics occurs (mostly during REM sleep) in partial epilepsy patients. This finding might represent an important factor contributing to the complex mechanism of SUDEP which takes place most often during sleep and supports the need of studying HRV specifically during this state in subjects with seizures.

Anticonvulsants↗
PubMed2001

Low prevalence of cardiac autonomic neuropathy in Type 1 diabetic patients without nephropathy.

AIM: To assess the prevalence of cardiac autonomic neuropathy (CAN) in Type 1 diabetic patients with and without nephropathy. METHODS: Sixty-six consecutive patients without nephropathy (n = 24), with incipient (n = 26) or overt nephropathy (n = 16) and a diabetes duration between 21 and 31 years were examined. Heart rate variability (HRV) as measure for CAN was investigated with short-term spectral analysis in the low-frequency (LF) band (0.06-0.15 Hz), reflecting sympathetic and vagal activity, and high-frequency (HF) band (0.15-0.50 Hz), reflecting vagal activity. HRV was expressed as spectral power (ms2, log-transformed). Normal, age-corresponding reference values were established in 184 controls. QTc intervals and dispersion were measured. RESULTS: After adjustment for age, there was no significant difference between healthy controls and patients without nephropathy. After further adjustment for diabetes duration, HbA1c, hypertension and treatment with beta-blockers, HRV in both frequency bands decreased with evidence of nephropathy. LF band (supine): patients without nephropathy 5.56 (4.89-6.21) (least squares means and 95% confidence interval (CI)), incipient nephropathy 5.72 (5.15-6.29) and overt nephropathy 4.11 (3.27-4.96). HF band (supine): without nephropathy 5.93 (5.26-6.60), incipient nephropathy 5.99 (5.41-6.57) and overt nephropathy 4.84 (4.00-5.68). Significant differences were found for patients without and with incipient nephropathy compared with those with overt nephropathy in the LF band and between patients with incipient nephropathy compared with those with overt nephropathy in the HF band. QTc intervals and QTc dispersion increased significantly with increasing nephropathy. CONCLUSIONS: Long-term Type 1 diabetes without nephropathy was not associated with impaired cardiac autonomic function in our study. However, in those with nephropathy, a loss of both vagal and sympathetic activity was present, and the severity of CAN correlated positively with more advanced nephropathy.

Adult↗
PubMedDate not supplied

Sampling frequency of the RR interval time series for spectral analysis of heart rate variability.

Spectral analysis of heart rate variability (HRV) is an accepted method for assessment of cardiac autonomic function and its relationship to numerous disorders and diseases. Various non-parametric methods for HRV estimation have been developed and extensive literature on their respective properties is available. The RR interval time series can be seen as a series of non-uniformly spaced samples. To analyse the power spectra of this series using the discrete Fourier transform (DFT), we need to interpolate the series for obtaining uniformly spaced intervals. The selection of sampling period plays a critical role in obtaining the power spectra in terms of computational efficiency and accuracy. In this paper, we shall analyse the RR interval time series from selected subjects for different sampling frequencies to compare the error introduced in selected frequency-domain measures of HRV at a constant frequency resolution for a specific duration of electrocardiogram (ECG) data. It should be pointed out that, although many other error causes are possible in the frequency-domain measures, our attention will be confined only to the performance comparison due to the different sampling frequencies. While the choice of RR interval sampling frequency (f(s)) is arbitrary, the sampling rate of RR interval series must be selected with due consideration to mean and minimum RR interval; f(s = )4 Hz was proposed for a majority of cases. This is an appropriate sampling rate for the study of autonomic regulation, since it enables us to compute reliable spectral estimates between dc and 1 Hz, which represents the frequency band within which the autonomic nervous system has significant response. Furthermore, resampled RR intervals are evenly spaced in time and are synchronized with the samples of the other physiologic signals, enabling cross-spectral estimates with these signals.

Algorithms↗
PubMedDate not supplied

An improved windowing technique for heart rate variability power spectrum estimation.

Spectral analysis of heart rate variability (HRV) is an accepted method for assessment of cardiac autonomic function and its relationship to numerous disorders and diseases. Discrete Fourier transform (DFT) based methods are widely used for their easy applicability, computational speed and the possibility for direct interpretation of results. This study assesses the limitation of windowing of the RR interval series of power spectrum estimation using DFT for heart rate variability studies. The mean value of the RR interval series should be subtracted before windowing. This may leave a small residual DC component after windowing, but the RR interval series is properly tapered to zero at the beginning and end of the window. However, if the windowed RR interval series has a non-zero mean then subtracting this mean will create an abrupt transition between the first and last data points, and the padded zeros. This is equivalent to superimposing upon the RR interval series a rectangular pulse of the same length as the window, with a height equal to the subtracted mean value. In the present paper an approach to overcome the above effects of the window in reducing the signal energy and introducing the low frequency component into spectrum has been suggested and incorporated. Result have been compared for DC biasing of windowed data spectrum, bias of windowed data removed by substraction of mean data, and data processed to remove windowed mean level and to maintain mean power. Thus the preprocessing of RR interval series with this method improves the accuracy of HRV analysis methods. The study was carried out by smoothing the complete RR interval series by single Hann window and by 50% overlapping the data segments of 256 data points followed by the DFT. Overlapping the data segments provides equal weight to all values in the RR interval series and smoothed spectral estimate with clearly dominant peaks in low- and high-frequency regions.

Algorithms↗
PubMed2006

Heart rate turbulence and heart rate variability in patients with mitral valve prolapse.

AIMS: Heart rate turbulence (HRT) and heart rate variability (HRV) have been shown to be independent and powerful predictors of mortality in a specific group of cardiac patients. However, the predictive values of HRV alone is modest and information on HRV in patients with mitral valve prolapse (MVP) has so far been conflicting. In addition, no studies have previously evaluated HRT in patients with MVP. To define better the effects of MVP on cardiac autonomic function, we assessed HRT and time-domain parameters of HRV in patients with MVP. METHODS AND RESULTS: Fifty patients with MVP and 70 controls without MVP were investigated. The diagnosis of MVP was confirmed by cross-sectional echocardiography in the parasternal long-axis view and apical 4-chamber view. The HRV and turbulence analysis were assessed from a 24-hour Holter recording. When HRT parameters were compared, the values of the HRT onset and slope were significantly lower in MVP patients than in the controls group (-0.109+/-0.207 vs. -0.289+/-0.170%, P=0.001 and 8.6+/-7.2 vs. 11.5+/-7.4 ms/RRI, P=0.043, respectively) and the number of patients who had abnormal HRT onset was significantly higher in the MVP group than in controls (15 vs. 8, P=0.011). In addition, HRV parameters were not statistically different between the two groups. CONCLUSION: Although we found that the decrease in HRV parameters was not significantly different between MVP patients and controls, HRT variables (especially HRT onset) were significantly lower in MVP patients. Therefore, in our opinion, HRT is an attractive, easily applicable, and better way of non-invasive risk prediction compared with another non-invasive risk predictor, HRV.

Adult↗
PubMed2005

Cardiomyopathy in dystrophin-deficient hearts is prevented by expression of a neuronal nitric oxide synthase transgene in the myocardium.

Null mutation of dystrophin causes the lethal pathology of Duchenne muscular dystrophy (DMD) in which there is progressive pathology of skeletal and cardiac muscles. A large proportion of DMD patient deaths are attributable to cardiac dysfunction associated with ventricular fibrosis, arrhythmias and conduction abnormalities, although the relationships between the dystrophin mutation and the cardiac defects are unknown. Here, we tested whether cardiac pathology in dystrophin-deficient mdx mice can be corrected by the elevated production of nitric oxide (NO) by the myocardium. Dystrophin-deficient mdx mice were produced in which there was myocardial expression of a neuronal nitric oxide synthase (nNOS) transgene. Expression of the transgene prevented the progressive ventricular fibrosis of mdx mice and greatly reduced myocarditis. Electrocardiographs (ECG) attained by radiotelemetry of freely ambulatory mice showed that mdx mice displayed cardiac abnormalities that are characteristic of DMD patients, including deep Q-waves, diminished S:R ratios, polyphasic R-waves and frequent premature ventricular contractions. All of these ECG abnormalities in mdx mice were improved or corrected by nNOS transgene expression. In addition, defects in mdx cardiac autonomic function, which were reflected by decreased heart rate variability, were significantly reduced by nNOS transgene expression. These findings indicate that increasing NO production by dystrophic hearts may have therapeutic value.

Animals↗
PubMed1995

Autonomic balance in patients with angina and a normal coronary angiogram.

The pathophysiology of angina pectoris in patients with a normal coronary angiogram is not clear. Furthermore, the pathophysiological impact of ST changes in syndrome X is controversial. The purpose of this study was to investigate cardiac autonomic function, by measuring 24 h heart rate variability, in patients with and without electrocardiographic evidence of ischaemia during exercise. Thirty-two patients with angina pectoris, a normal coronary angiogram, echocardiogram, hyperventilation test and gastro-oesophageal investigation were studied. Fourteen healthy subjects served as controls. Fifteen patients had significant ST segment depression during stress testing, whereas 17 had no electrocardiographic signs of ischaemia. Heart rate variability was calculated as (1) mean RR = mean of all normal RR intervals, (2) the difference in mean RR level between when awake and when asleep (mean RR wake-sleep)-a tentative index of sympathetic activation, (3) the standard deviation (SD)-a broad band measure of autonomic balance, and (4) a percentage of successive RR interval differences > or = 6% (pNN6%)-an index of vagal modulation. The coronary vascular resistance was measured at rest and during pacing. Mean RR and autonomic indexes did not differ between patients with a positive exercise test and controls (831/884 ms; 24 h SD 125/134 ms; pNN6% 6.715.4%, respectively). Patients with a normal exercise test had shorter mean RR (758 ms vs 844 ms; P < 0.05) and significantly reduced 24-h SD (103 ms vs 134 ms; P < 0.05) than controls, whereas values for vagal index (6.5% vs 5.4%) did not differ from healthy controls. Mean RR wake-sleep also tended to be lower in patients with a normal exercise test (-125 ms vs -173 ms) compared to controls (P < 0.1). Patients with a positive exercise test had a significantly attenuated reduction in coronary vascular resistance during pacing in comparison to patients with a normal exercise test (-0.131 -0.26 mmHg x min. ml-1; P < 0.05). The findings suggest the occurrence of general elevated sympathetic activation in angina patients with a normal exercise test. Patients with a positive exercise test exhibited no signs of autonomic dysfunction although these patients had altered coronary vascular resistance indicating microvascular angina. This supports the suggestion that patients with a normal exercise test constitute an independent pathophysiological entity.

Adult↗
PubMed1996

Alterations in spectral characteristics of heart rate variability as a correlate of cardiac autonomic dysfunction after esophagectomy or pulmonary resection.

BACKGROUND: Both esophagectomy and pulmonary resection are associated with postoperative cardiac complications, partly because of autonomic perturbations involving the heart. This study was undertaken to determine whether heart rate variability (HRV), employed as an index of cardiac autonomic function, changes in patients undergoing esophagectomy or pulmonary resection. METHODS: Electrocardiographic RR intervals were measured in 20 esophagectomized patients, 10 undergoing right and 10 undergoing left pulmonary resection on the preoperative day as baseline data and on postoperative days 1, 3, 5, 7, 14, and 30. Instantaneous heart rate was calculated every 250 ms from 416-s data of RR intervals. Power spectra of HRV for 128 s were computed using a fast Fourier transform and normalized by squared mean heart rate. The average ten sets of normalized HRV power were obtained by integrating the following power spectral bands: the low-, (0.06-0.10 Hz), high- (0.15-0.40 Hz), and total-frequency regions (0.01-0.40 Hz). RESULTS: In the esophagectomy group, mean low-, high-, and total-frequency HRV power decreased after surgery to 17%, 6%, and 15% of their preoperative values, respectively, and these indexes remained suppressed for up to 30 days. After right pulmonary resection, low- and total-frequency HRV power decreased through 30 and 7 postoperative days, respectively. In the left pulmonary resection group, HRV remained unchanged. In the esophagectomy group, mean (+/- SEM) heart rate increased from 78 (+/- 3) bpm to more than 90 bpm throughout the study, and body temperature from 36.5 (+/- 0.1) degrees C to more than 37.0 degrees C through 14 postoperative days. Heart rate and body temperature remained increased for 3 days after pulmonary surgery. Mean arterial pressure remained unchanged in the three surgical groups. CONCLUSIONS: Reductions indicate HRV after esophagectomy or right pulmonary resection indicate a substantial and prolonged surgical injury to the autonomic nervous control of pulse rate.

Aged↗
PubMed2002

The association between personal measurements of environmental exposure to particulates and heart rate variability.

BACKGROUND: Epidemiologic evidence indicates that airborne particulates are associated with mortality risk, predominately from heart disease. This may occur through changes in the cardiac autonomic nervous system, witnessed by changes in heart rate variability. METHODS: This short-term longitudinal study used continuous personal particulate matter measurements to examine the effects of exposure to particulate matter less than 2.5 microm in diameter (PM2.5) on heart rate and rate variability in 20 relatively young, healthy male workers. Continuous exposure and cardiac monitoring were performed on each subject on a nonwork day. The 5-minute standard deviation of the normal-to-normal interval was used as the main measure of heart rate variability. RESULTS: Mixed-effects regression models estimate an average 1.4% (95% confidence limits = -2.1, -0.6) decrease in the 5-minute standard deviation of the normal-to-normal interval for each 100 microg/m3 increase in the 3-hour PM2.5 moving average, and small increases in heart rate, after adjustment for potential confounding factors. Predicted effects of exposure were greatest using the 3-hour averaging interval for PM2.5 and decreased in magnitude using shorter and longer intervals. CONCLUSIONS: These results reveal an association between cardiac autonomic function and environmental PM2.5 exposure. These observed associations may result from decreased vagal or increased sympathetic tone.

Adult↗
PubMed2003

Weight loss and weight maintenance, ambulatory blood pressure and cardiac autonomic tone in obese persons with the metabolic syndrome.

BACKGROUND: Cardiac autonomic function may play a role in obesity-associated hypertension. Most studies on the effects of weight loss on blood pressure and autonomic function do not distinguish between acute or continuing weight loss and steady-state weight maintenance after weight loss. OBJECTIVES: We sought to clarify the changes in ambulatory blood pressure, heart rate and heart rate variability as assessed by spectral analysis during rapid weight loss and extended weight maintenance. PARTICIPANTS: Abdominally obese (body mass index 35.2 +/- 2.1 kg/m2, waist 114.3 +/- 9.0 cm) men and women (n = 41) with the metabolic syndrome. METHODS AND RESULTS: The 34 men and women completing the 1-year weight maintenance period lost 14.6 +/- 3.5 kg during the 9-week very-low-calorie diet and maintained a 12.5 +/- 7.5 kg weight loss to the end of the trial. Ambulatory 24-h blood pressure decreased dramatically during the diet (-9.0 +/- 8.0/-4.6 +/- 4.9 mmHg), but had risen to near baseline levels by the end of weight maintenance (-2.2 +/- 8.2 /-1.2 +/- 6.1 mmHg). Night-time heart rate decreased (-5.5 +/- 9.6 beats/min, P = 0.012), and heart rate variability total and low-frequency power measured during 5 min of controlled breathing increased by 46-56% (P = 0.003-0.09) during rapid weight loss. These changes gradually attenuated during weight maintenance, and only the change in night-time heart rate was still of borderline significance after 1 year of weight maintenance (-3.6 +/- 8.6 beats/min, P = 0.063). Heart rate variability high-frequency power tended to increase during weight loss and weight maintenance. CONCLUSION: Despite successful weight maintenance, the decrease in ambulatory blood pressure after rapid weight loss was largely transient. The increase in parasympathetic tone was more sustained, but also gradually attenuated during 1 year of weight maintenance.

Baroreflex↗
PubMed2004

Mental stress inhibits pain perception and heart rate variability but not a nociceptive withdrawal reflex.

AIM: Do distraction from- or attention to sural nerve stimulation affect pain, heart rate variability, and a spinal withdrawal reflex? MATERIAL AND METHODS: In 26 male volunteers, electrical stimulation at the distal cutaneous receptive field of the sural nerve elicited pain and a nociceptive withdrawal reflex. Intensity of pain was rated on a numeric rating scale. Electromyographic reflex responses were measured from biceps femoris muscle. Cardiac autonomic function was estimated by heart rate variability measures and was expressed in the time domain as mean of RR-intervals for normal heart beats (mean-RR) and standard deviation of all normal RR-intervals (SD-NN) and, in the frequency domain, where pure vagal activity was assessed by high frequency power (0.15-0.4 Hz). Low frequency power (0.04-0.15 Hz) reflects both parasympathetic and sympathetic control. Effect parameters were recorded before and during random distraction and attention. Distraction from sural nerve stimulation was induced by a mental arithmetic test, paced auditory serial addition task (PASAT), while attention was induced by concentrating on painful foot stimulation. RESULTS: Paced auditory serial addition task decreased mean-RR and SD-NN, frequency domain parameters, as well as pain (P<0.001). In contrast, PASAT did not change the spinal withdrawal reflex. Attention did not affect any effect parameter. CONCLUSION: Distraction by PASAT altered autonomic activity and inhibited pain but failed to affect withdrawal reflex responses, while attention had no effect on either parameter. Psychological distraction and attention may have different effects on noxious evoked pain perception and autonomic activity. Pain relief during PASAT probably involves supraspinal mechanisms.

Adult↗
PubMed2005

Heart rate variability in patients with essential hyperhidrosis: dynamic influence of sympathetic and parasympathetic maneuvers.

BACKGROUND: Essential hyperhidrosis has been associated with an increased activity of the sympathetic system. In this study, we investigated cardiac autonomic function in patients with essential hyperhidrosis and healthy controls by time and frequency domain analysis of heart rate variability (HRV). METHOD: In this study, 12 subjects with essential hyperhidrosis and 20 healthy subjects were included. Time and frequency domain parameters of HRV were obtained from all of the participants after a 15-minute resting period in supine position, during controlled respiration (CR) and handgrip exercise (HGE) in sitting position over 5-minute periods in each stage. RESULTS: Baseline values of HRV parameters including RR interval, SDNN and root mean square of successive R-R interval differences, low frequency (LF), high frequency (HF), normalized unit of high frequency (HFnu), normalized unit of low frequency (LFnu), and LF/HF ratio were identical in two groups. During CR, no difference was detected between the two groups with respect to HRV parameters. However, the expected increase in mean heart rate (mean R-R interval) did not occur in hyperhidrotic group, whereas it did occur in the control group (Friedman's P = 0.000). Handgrip exercise induced significant decrease in mean R-R interval in both groups and no difference was detected between the two groups with respect to the other HRV parameters. When repeated measurements were compared with two-way ANOVA, there was statistically significant difference only regarding mean heart rate in two groups (F = 6.5; P = 0.01). CONCLUSION: Our overall findings suggest that essential hyperhidrosis is a complex autonomic dysfunction rather than sympathetic overactivity, and parasympathetic system seems to be involved in pathogenesis of this disorder.

Analysis of Variance↗
PubMed2005

Cigarette smoking and heart rate variability: dynamic influence of parasympathetic and sympathetic maneuvers.

BACKGROUND: Cigarette smoking has been associated with increased activity of the sympathetic nervous system. In this study, we investigated cardiac autonomic function in heavy smokers and nonsmoker controls by analysis of heart rate variability (HRV). METHOD: Twenty-four long-term heavy smokers (men) and twenty-two nonsmoker subjects (hospital staff) were included to study. Time domain [mean R-R interval (RR), the standard deviation of R-R interval index (SDNN), and the root mean square of successive R-R interval differences (RMSSD)] and frequency domain [high frequency (HF) low frequency (LF), and LF/HF ratio] parameters of HRV were obtained from all participants after 15 minutes resting period in supine position (S), during controlled respiration (CR), and handgrip exercise (HGE) over 5-minute periods. RESULTS: Baseline SDNN and RMSSD values were found to be lower in smokers than in nonsmokers. (64+/-10 vs 78+/-22, P<0.05 and 35+/-12 vs 54+/-30 ms, P<0.05). Baseline LF/HF ratio was also found to be higher in smokers than in nonsmokers (1.3+/-0.6 vs 0.9+/-0.5 ms, P<0.05). The other HRV parameters including R-R interval, LF, and HF were not significantly different. During CR, expected increase in RR, SDNN, and RMSSD did not occur in smokers, while it did occur in nonsmokers. Most HRV indices were significantly affected by HGE in both groups. In addition, the duration of smoking was found to be inversely correlated with RMSSD and HF and positively correlated with LF/HF ratio. CONCLUSION: Vagal modulation of the heart is blunted in heavy smokers, particularly during a parasympathetic maneuver. Blunted autonomic control of the heart may partly be associated with adverse event attributed to cigarette smoking.

Adult↗
PubMed2006

Heart rate variability in young women with polycystic ovary syndrome.

BACKGROUND: Limited data are available related to the effects of sex hormones on cardiac autonomic function. Few studies investigated the heart rate variability (HRV) parameters during regular menstrual cycle or in postmenopausal women using hormone replacement therapy, but the results were contradictory. The aim of the study was to compare the characteristics of the autonomic innervation of the heart in polycystic ovary syndrome (PCOS) patients with regularly cycling controls. METHODS: Thirty PCOS patients and 30 healthy regularly cycling controls were included in the study. Groups were compared with respect to age and various cardiovascular risk factors. Characteristics of autonomic innervation of the heart were evaluated with HRV. Power spectral analysis of HRV was performed to calculate the low frequency peak (LF 0.04-0.15 Hz), high-frequency peak (HF 0.15-0.40 Hz), LF in normalized unit (LF nu), HF in normalized unit (HF nu) and LF/HF ratio. RESULTS: PCOS patients had adverse cardiovascular risk profile than controls. As the HRV parameters, PCOS patients had significantly higher LF nu (P = 0.005) and LF/HF ratio (P = 0.001) and significantly lower HF (P = 0.006) and HF nu (P < 0.001) compared to controls. CONCLUSION: Autonomic innervation of the heart can be affected in PCOS with increased sympathetic and decreased parasympathetic components of HRV. As a result, sympathetic to parasympathetic ratio may increase in PCOS. This finding should be confirmed with larger studies also evaluating the clinical implications of altered HRV parameters.

Adult↗
PubMed2003

Blunted cardiac autonomic responsiveness to hypoxemic stress in healthy older adults.

Supine resting cardiac dynamics and responses to steady-state hypoxemia were investigated in six healthy older (59-72 yrs) adults using coarse-graining spectral analysis of heart rate variability (HRV) and were compared to six young (22-29 yrs) adults studied previously (Lucy et al., 2000). End-tidal carbon dioxide pressure (PETCO2) was clamped at 1-2 mmHg above the usual resting value for 11 min of euoxia (PETO2 100 mmHg), followed by 22 min of hypoxia (PETO2 55 mmHg). During euoxia, vagally mediated harmonic and fractal power of HRV of older adults was minimal. Hypoxia induced an increase in ventilation, p < 0.01, and heart rate, p < 0.05. The heart rate increase (mean +/- SE) of 0.23 +/- 0.08 beats.min-1 per 1% decrease in arterial O2 saturation was 25% of that demonstrated previously by young subjects, p < 0.001. In older adults, HRV spectral power remained unchanged during hypoxia, providing further evidence of an age-related blunting of cardiac autonomic function.

Aged↗
PubMed1997

Daily exercise and gender influence postexercise cardiac autonomic responses in hypertensive rats.

The influence of daily spontaneous running (DSR) and gender on postexercise cardiac autonomic responses was examined in spontaneously hypertensive rats. Rats were weaned at 4-5 wk of age and were randomly assigned to a sedentary (7 males and 6 females) or DSR (7 males and 8 females) group. After 8 weeks of DSR or sedentary control, rats were chronically instrumented with arterial and venous catheters. After 5 days of recovery, cardiac sympathetic (ST) and parasympathetic tonus (PT) were determined (by the response of heart rate to receptor antagonists) on alternate days under two experimental conditions: no exercise and postexercise. After a single bout of dynamic treadmill exercise (12 m/min, 10% grade for 40 min) ST was reduced (P < 0.05) (male sedentary: no exercise 45 +/- 4 vs. postexercise 28 +/- 3 beats/min; female sedentary: no exercise 69 +/- 10 vs. postexercise 37 +/- 7 beats/ min). PT was also altered after exercise (male sedentary: no exercise -31 +/- 4 vs. postexercise -11 +/- 2 beats/min; female sedentary: no exercise -5 +/- 4 vs. postexercise 7 +/- 4 beats/min). After DSR, ST was reduced (male sedentary 45 +/- 4 vs. DSR 22 +/- 3 beats/min; female sedentary 69 +/- 10 vs. DSR 36 +/- 4 beats/min) (P < 0.05). Finally, male rats had a lower ST and higher PT than female rats. These results demonstrate that 1) ST was reduced after a single bout of dynamic exercise; 2) ST was reduced after DSR; 3) the autonomic response to acute exercise was attenuated after DSR; and 4) there was a gender influence on the cardiac autonomic function.

Animals↗