Spectral Analysis Of Heart Rate Variability Research Articles

Outcome of heart rate variability and ventricular late potentials after liver transplantation for familial amyloidotic polyneuropathy

Reduced heart rate variability (HRV) is common in familial amyloidotic polyneuropathy (FAP), as well as cardiac arrhythmias. We examined the effects of liver transplantation (LTx) on 24-h HRV and ventricular late potentials. Twenty-one liver-transplanted FAP patients underwent Holter-ECG recordings and signal average electrocardiography recordings (SAECG) before and after LTx. Mean follow-up time after LTx was 21.7 months. Three patients had marked increased HRV after LTx, but this was in all cases caused by the development of subtle atrial arrhythmia and did not reflect an improvement in the cardiac autonomic control. In total, ten patients were excluded from analysis of HRV because of arrhythmia. Spectral analysis of HRV showed no significant differences before and after LTx in the remaining 11 patients. Positive late potentials were found in 33% of patients before LTx and this proportion was unchanged after LTx. Reduced HRV and positive late potentials are common in Swedish FAP patients, and remain stable, at least within the short term after transplantation. If an increase of HRV after transplantation is observed, it should raise the suspicion that the patient has developed subtle atrial arrhythmia.

Can Analysis of Heart Rate Variability Predict Arrhythmia in Children with Fontan Circulation?

The aim of this study was to examine whether changes in heart rate variability (HRV) can predict arrhythmias in children who have undergone the Fontan procedure. The study included 15 children with total cavopulmonary connection. All examinations included echocardiography and 24-h ambulatory electrocardiogram with power spectral analysis of HRV and Poincaré plots (plots of each R-R interval as a function of the previous R-R interval). Six patients developed supraventricular tachycardia (four or more consecutive supraventricular beats). One patient was excluded from the study due to the development of bradycardia, necessitating placement of a pacemaker. Compared to the arrhythmia group, the patients without arrhythmias (n = 8) exhibited a significant difference in the standard deviation of instantaneous beat-to-beat R-R interval variability (p = 0.02). Poincaré plots of patients without arrhythmias showed a typical torpedo- or comet-shaped pattern, whereas the arrhythmia group showed a more complex pattern. Although this study examined only a few subjects, needing confirmation by larger studies, it does indicate that patients who develop arrhythmias after receiving the Fontan procedure show a different Poincaré pattern compared to the nonarrhythmic group-even before the arrhythmia can be detected using the conventional Holter procedure. Routine follow-up using the Holter procedure and Poincaré plot analysis could help detect early arrhythmias.

The influence of respiratory pattern on heart rate variability analysis in heart failure

Autonomic dysfunction is present early in the course of heart failure, and has a direct role on deterioration of cardiac function and prognosis. Heart rate variability (HRV) estimates sympathovagal control of heart frequency. The influence of respiratory pattern on HRV is clinically important. Breathing disorders are common in heart failure and highly affect HRV and autonomic evaluation. It was previously shown that slow and deep breathing increased parasympathetic tone, but effects of this respiratory pattern on HRV were not evaluated. The aim of the study was to estimate effects of slow and deep breathing (SDB) on HRV in heart failure patients. In 55 patients with heart failure (78% male, mean age 57.18 +/- 10.8 yrs, mean EF = 34.12 +/- 10.01%) and 14 healthy controls (57.1% male, mean age 53.1 +/- 8.2 yrs), short term HRV spectral analysis was performed (Cardiovit AT 60, Schiller). VLF, LF, HF and LF/HF were determined during spontaneous and deep and slow breathing at 0.1 Hz (SDB). LF, HF and LF/HF significantly increased during SDB compared with spontaneous breathing both in controls (LF 50.71 +/- 61.55 vs. 551.14 +/- 698.01 ms2, p < 0.001; HF 31.42 +/- 29.98 vs. 188.78 +/- 142.74 ms2, p < 0.001 and LF/HF 1.46 +/- 0.61 vs. 4.21 +/- 3.23, p = 0.025) and heart failure patients (LF 27.37 +/- 36.04 vs. 94.50 +/- 96.13 ms2, p < 0.001; HF 12.13 +/- 19.75 vs. 41.58 +/- 64.02 ms2, p < 0.001 and LF/HF 3.77 +/- 3.79 vs. 6.38 +/- 5.98, p = 0.031). Increments of LF and HF induced by SDB were significantly lower in patients than healthy controls. Heart failure patients had lower HRV compared to healthy controls both during spontaneous breathing and SDB. During spontaneous breathing, only HF was significantly lower between healthy controls and patients (p = 0.002). During SDB VLF (p = 0.022), LF (p < 0.001) and HF (p < 0.001) were significantly lower in heart failure patients compared to controls. These data suggest that SDB increases HRV both in healthy and heart failure patients; the highest increment is in LF range. Differences in spectral profile of HRV between healthy controls and heart failure patients become more profound during SDB. Controlled respiration during HRV analysis might increase sensitivity and reliability in detection of autonomic dysfunction in heart failure patients.

Novel spectral indexes of heart rate variability as predictors of sudden and non‐sudden cardiac death after an acute myocardial infarction

Background. Various indexes of 24‐hour heart rate variability (HRV) have been able to predict all‐cause mortality after an acute myocardial infarction (AMI), but their value in predicting specific modes of cardiac death has been limited.Aim. The aim of this study was to assess the role of two novel spectral indexes of HRV as predictors of either sudden (SCD) or non‐sudden cardiac death after an AMI.Method. We used two novel methods of spectral analysis of HRV: 1) the high‐frequency (HF) spectral component, Vindex, calculated as an average HF power from the most linear portion of HF power versus the R‐R interval regression curve, and 2) the prevalent low‐frequency oscillation of heart rate (PLF). Vindex, conventional HRV measures, and PLF were analyzed from 24‐hour Holter recordings of 590 patients with a recent AMI.Results. During the mean follow‐up of 39±14 months, SCD occurred in 3% (n = 17) and non‐sudden cardiac death in 5% (n = 28) of the patients. In univariate analysis, Vindex was the most potent predictor of SCD (RR: 6.0, 95% CI: 1.7–20.7, P<0.01), also remaining the most powerful predictor of SCD after adjustment for clinical variables and ejection fraction (RR: 4.2, 95% CI: 1.2–15.2, P<0.05). PLF was a potent predictor of non‐sudden cardiac death (RR: 13.9, 95% CI: 5.9–32.5, P<0.001), but it did not predict SCD.Conclusions. Novel spectral HRV analysis methods, Vindex and PLF, provide significant information of the risk of the specific mode of death after an AMI.

Tilt table testing in childhood: improved sensitivity by non-invasive haemodynamic monitoring devices?

Objective — Tilt table testing represents a valuable diagnostic method in suspected neurally mediated syncope. As sympathovagal imbalance and impaired baroreceptor sensitivity (BRS) have been observed in these patients, both methods were used in this study to investigate whether a combination of these parameters would improve sensitivity and whether specific patterns of neurally mediated syncopes would correspond to characteristic trends in heart rate variability (HRV) and BRS.Methods and results — Fifty-one pts. (29female, mean age 14.5±3.9 y) with unexplained syncope and 15 control subjects (9female, mean age 14.8±3.0 y) were tested following a standard tilt table test protocol. Power spectral analysis (PSA) of HRV and BRS calculation were used additionally to beat-to-beat blood pressure and ECG-monitoring.Twenty-three out of 51 pts. (45%) experienced a syncope after 18±10.2min of tilting. In 2/23 patients (8.6%) a postural tachycardia syndrome (POTS), in 14/23 (60.8%) a neurally mediated syncope of mixed type, in 2/23 (8.6%) a vasodepressor syncope and in 5/23 (21.7%) a cardioinhibitory syncope with asystole were observed. PSA of HRV and BRS revealed a specificity, sensitivity, and positive and negative predictive values of the cut-off points in combination (LF/HF ≥ 2.7 and BRS ≤ 8) of 93.3%, 65.2%, 93% and 39%, respectively.Conclusion — In this study population, BRS and PSA of HRV were able to improve sensitivity of tilt testing after unexplained syncope. Specific BRS or HRV patterns in different mechanisms of neurally mediated syncope could not be identified possibly due to the small sample size.

Influence of cardiac‐resynchronization therapy on heart rate and blood pressure variability: 1‐year follow‐up

Several studies have shown that cardiac-resynchronization therapy (CRT) improves haemodynamic function, cardiac symptoms, and heart rate variability (HRV) and reduces the risk of mortality and sudden death in subjects with chronic heart failure (CHF). In subjects with CHF, power spectral values for the low-frequency (LF) component of RR variability < or =13 ms2, are associated with an increased risk of sudden death. To assess whether spectral indexes obtained by power spectral analysis of HRV and systolic blood pressure (SBP) variability could predict malignant ventricular arrhythmias in patients with severe CHF treated with an implantable cardioverter-defibrillator (ICD) alone or with ICD+CRT. In addition, changes in non-invasive spectral indices using short-term power spectral analysis of HRV and SBP variability during controlled breathing in 15 patients with CHF treated with an ICD alone and 16 patients receiving ICD+CRT, were assessed pre-treatment and at 1 year. Arrhythmias necessitating an appropriate ICD shock were more frequent in subjects who had low LF power. CRT improved all spectral components, including LF power. Low LF power values predict an increased risk of malignant ventricular arrhythmias; after 1 year of CRT most non-spectral and spectral data, including LF power, improved. Whether these improvements lead to better long-term survival in patients with CHF remains unclear.

Spectral and Time-Domain Analyses of Heart-Rate Variability During Head-Upright Tilt-Table Testing in Children with Neurally Mediated Syncope

Neurocardiac syncope (NS) is a common cause of syncope in children. The mechanism, though related to abnormalities in autonomic function, has not been fully elucidated, particularly in pediatric patients. This study assessed the heart-rate variability (HRV) response to head-upright tilt-table test (HUT) in children with NS and normal volunteers. Spectral and time-domain analysis of HRV was used to assess changes in autonomic function in 27 children (9 male, mean age 12.3 +/- 1.6 years) with a history of at least one episode of syncope and positive passive HUT and 27 age-matched normal volunteers with negative passive HUT before and during postural tilt and to attempt to relate such changes to specific types of hemodynamic response to tilt. Frequency-domain measurements of the high-(HF) and low-(LF) frequency bands and the ratio LF/HF were derived from Holter recordings and computed by fast Fourier analysis for 5-min intervals. Time-domain measurements of the SDNN, SDNNI, SDANN, RMSSD, and triangular index were derived from 24-h Holter recordings. There were no significant differences between clinical characteristics, time-domain, and basal frequency domain parameters of the groups. Mean values of LF and LF/HF ratio was increased and HF was decreased significantly in response to tilt in both patient and control groups. Mean values of LF and LF/HF ratio were higher and HF was lower compared to controls immediately after tilt. LF and LF/HF ratio showed a statistically significant decrease and a significant increase in HF during syncope in patients. The three subgroups of patients had similar patterns of changes in autonomic activity. The results of this study show that although the basal autonomic function was similar to that of the control group, patients with NS have a different pattern of response to the HUT. In our study, patients with NS demonstrated an exaggerated response to the HUT. This exaggerated response may be the factor that activates the pathological reflexes of NS. The pathological mechanism leading to NS appears to be independent of the specific type of hemodynamic response to HUT.

Modelling long-term heart rate variability: an ARFIMA approach

Long-term heart rate variability (HRV) series can be described by time-variant autoregressive modelling. HRV recordings show dependence between distant observations that is not negligible, suggesting the existence of long-range correlations. In this work, selective adaptive segmentation combined with fractionally integrated autoregressive moving-average models is used to capture long memory in HRV recordings. This approach leads to an improved description of the low- and high-frequency components in HRV spectral analysis. Moreover, it is found that in the 24-h recording of a case report, the long-memory parameter presents a circadian variation, with different regimes for day and night periods.

Heart Rate Variability in Young Women with Polycystic Ovary Syndrome

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. 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. 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. 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.

Early occurrence of anti-muscarinic autoantibodies and abnormal vagal modulation in Chagas disease

Background Autoimmunity and dysautonomia are established features of Chagas disease (ChD) that could be related to its pathogenesis. Our objective was to assess heart rate variability (HRV) and levels of anti-M 2 receptors autoantibodies in ChD patients with and without left ventricular (LV) dysfunction, in order to establish if these abnormalities occur early and concomitantly in the course of the illness. Methods ChD patients ( n = 75) and healthy controls ( n = 14) underwent a standardized protocol including Doppler echocardiogram, Holter monitoring, HRV analysis, and measurement of anti-M 2 receptors autoantibodies (ELISA). ChD patients were divided accordingly by the absence (group 1, n = 45) or presence (group 2, n = 30) of LV dysfunction, defined as reduced LV ejection fraction (< 55%) or regional wall motion abnormalities (including ventricular aneurysm). Results Both ChD groups displayed increased optical density values of anti-M 2 cholinergic autoantibodies (Median (IQR): control = 1.98(0.51); ChD 1 = 2.76(0.97); ChD 2 = 2.72(1.34), p < .001) and reduced HF power of spectral analysis of HRV when compared to controls (Median (IQR) in ms 2: control = 1087(2284); ChD 1 = 286(763); ChD 2 = 285(763), p < .001). M 2 levels were significantly correlated with HF power values ( r = − 0.32, p = 0.023), but not with LV ejection fraction. Conclusions Anti-muscarinic autoantibodies and abnormal vagal modulation occur early in ChD patients, independently of the presence of LV dysfunction. Levels of antibodies against M 2 muscarinic receptors were significantly and negatively correlated with HRV index HF power, suggesting an inhibitory effect of autoantibodies in vagal function.

SINGLE DOSE OF TIOTROPIUM DOES NOT EFFECT HEART RATE VARIABILITY

Aim: Anticholinergic drugs may alter cardiac autonomic modulation. The aim of this study was to investigate the effects of inhaled tiotropium on heart rate variability (HRV). Methods: A randomized, double-blind, crossover design study was conducted on 11 healthy volunteers. Tiotropium or placebo was administered in two different testing sessions. Time domain parameters; mean R-R interval (mean-RR), the standard deviation of R-R interval (SDNN) and the root mean square of successive R-R interval differences (RMSSD) and power spectral analysis of HRV were assessed in the supine position, during handgrip exercise and controlled breathing before and after drug administration. Results: There were no statistically significant difference in baseline HRV parameters obtained before each drug administration (p >0.05). HRV parameters obtained after each drug administration were found not to be different during supine position, controlled breathing and handgrip exercise. Conclusion: Administration of single dose tiotropium did not effect cardiac autonomic modulations in healthy volunteers.

Circadian change of cardiac autonomic function in correlation with intra‐esophageal pH

Although autonomic alterations are observed in patients with gastroesophageal reflux disease (GERD), the influence of visceral receptor responses on the dynamics of autonomic function remains unknown. The aim of this study was to investigate the autonomic functional changes in association with intra-esophageal pH under ambulation. Thirty patients referred for 48 h ambulatory pH monitoring underwent simultaneous 24 h cardiac monitoring for heart rate variability (HRV). We used linear mixed-effects models to estimate the relationship between esophageal acid exposure and power spectral analysis of HRV, including low-frequency power (0.04 < LF < 0.15 Hz), high-frequency power (0.15 < or = HF < 0.4 Hz), and LF/HF power ratio. Over the 24-h period, patients with pathological reflux had lower average LF and HF powers than patients with functional heartburn, but the LF/HF power ratios were similar for the two patient groups. As we stratified the data according to waking and sleeping times, a significantly higher HF power but lower LF/HF power ratio was found during sleeping time regardless of diagnosis. In the regression analysis, esophageal pH was positively associated with change (not basal tone) of both LF and HF powers during waking, but only with change of HF power during sleeping time. The significant associations between pH values and changes in HRV decreased gradually with time. The LF/HF power ratio did not alter significantly with pH. Esophageal acid exposure is generally associated with decreases in autonomic tone. A predominant parasympathetic fluctuation during sleeping and a superimposed sympathetic interaction during waking dictate diurnal characteristics of autonomic regulation.

The use of heart rate variability measures to assess autonomic control during exercise

Heart rate variability (HRV) is a non-invasive indicator of cardiac autonomic modulation at rest. During rhythmic exercise, global HRV decreases as a function of exercise intensity. Measures reflecting sympathovagal interactions at rest do not behave as expected during exercise. This makes interpretation of HRV measures difficult, especially at higher exercise intensities. This problem is further confounded by the occurrence of non-neural oscillations in the high-frequency band due to increased respiratory effort. Alternative data treatments, such as coarse graining spectral analysis (CGSA), have demonstrated expected changes in autonomic function during exercise with some success. The separation of harmonic from fractal and/or chaotic components of HRV and study of the latter during exercise have provided further insight into cardioregulatory control. However, more research is needed. Some cross-sectional differences between HRV in athletes and controls during exercise are evident and data suggest longitudinal changes may be possible. Standard spectral HRV analysis should not be applied to exercise conditions. The use of CGSA and non-linear analyses show much promise in this area. Until further validation of these measures is carried out and clarification of the physiological meaning of such measures occurs, HRV data regarding altered autonomic control during exercise should be treated with caution.

Heart rate dynamics in iNOS knockout mice

Nitric oxide has both an inhibitory and excitatory role in the regulation of pre-ganglionic sympathetic neurons, involving the iNOS and nNOS systems respectively. The aim of the present study was to examine cardiovascular autonomic activity in iNOS knockout mice using spectral analysis of heart rate variability (HRV), and to determine the role of iNOS in altered HRV in endotoxaemia. Electrocardiograms were recorded in anaesthetised mice, and the R–R intervals digitized for spectral analysis of HRV and cardiac rhythm regularity using sample entropy analysis. The basal heart rate was higher in iNOS knockout mice compared with controls (465 ± 8 vs 415 ± 13 beat/min P < 0.05), with a significant increase in the low frequency power of HRV spectra in iNOS knockout mice compared with controls (49.4 ± 4.3 vs 33.8 ± 5.6 normalized units, P < 0.05), consistent with increased cardiac sympathetic activity. Endotoxaemia is known to decrease HRV, but the role of iNOS is unknown. LPS (20 mg/kg i.p) increased basal heart rate in both wild type and iNOS knockout mice, but caused a depression of HRV and sample entropy in both groups. Studies in isolated beating atria showed that the changes of HRV under basal or post-LPS conditions disappeared in vitro, suggesting that the autonomic system is responsible for altered HRV. We conclude that disruption of iNOS gene leads to an increase in the low frequency power of HRV consistent with increased cardiac sympathetic activity. These data also demonstrate that LPS-induced decrease of HRV is independent of iNOS.

37 Autonomic nervous system response to a solid meal in healthy children: its relation to gastric myoelectrical activity

Electrogastrogram (EGG) is a measurement of gastric electrical activity using cutaneous electrodes. Autonomic nervous function is an important modulator of gastric activity, but little is known regarding its relation with the EGG parameters. The aims of this study were to investigate the patterns of myoelectrical and autonomic activities both in the fasting and in the fed state and their correlation in healthy children.Methods: Simultaneous recordings of EGG and electrocardiogram were performed in 28 healthy children (13 M, 15 F, mean age: 12.4 years, range: 8–17) for 30 min in the fasting state and 60 min after a solid test meal. Spectral analysis was performed to compute EGG parameters and their postprandial changes. The autonomic activity was assessed based on spectral analysis of the heart rate variability (HRV) signal which was derived from the electrocardiogram. Data are presented as mean ± SE.Results: The solid meal resulted in a postprandial increase in the EGG dominant frequency (2.92 ± 0.08 cpm vs. 3.16 ± 0.07 cpm, P &lt; 0.05), dominant power (46.9 ± 0.8 dB vs. 53.7 ± 1.5 dB, P &lt; 0.05), and percentage of normal slow waves (81.9 ± 2.0% vs. 89.0 ± 2.0%, P &lt; 0.05). Spectral analysis of HRV revealed that sympathetic activity primarily associated with power in the low‐frequency band of HRV (LF) was increased in the postprandial state (0.34 ± 0.02 vs. 0.43 ± 0.03, P &lt; 0.05). The parasympathetic activity primarily associated with power in high‐frequency band of HRV (HF) was significantly higher in the fasting state (0.66 ± 0.02 vs. 0.58 ± 0.03, P &lt; 0.05). The sympathovagal balance associated with the LF‐to‐HF ratio was much higher in the postprandial state (0.56 ± 0.05 vs. 0.90 ± 0.13, P &lt; 0.05). Moreover postprandial LF was positively and HF was negatively correlated with the postprandial increase in EGG dominant power (r = 0.39; P = 0.04, respectively).Conclusions: The solid meal resulted in a significant increase in EGG dominant frequency, dominant power and percentage of normal slow waves as well as sympathovagal balance in healthy children, suggesting that both vagal and sympathetic pathways are involved in modulation of gastric myoelectrical activity.

The Measurement of Neurovegetative Activity During Anesthesia and Surgery in Swine: An Evaluation of Different Techniques

In this study we evaluated, in 10 sevoflurane-anesthetized pigs undergoing abdominal surgery, different techniques for measuring autonomic nervous system (ANS) activity: ANSiscope index, spectral analysis of heart-rate variability, hemodynamic variables, and plasma catecholamines and cortisol levels. Animals underwent a 120-min anesthesia during which unilateral ovariectomy was performed. Cardiovascular and respiratory responses were monitored. ANSiscope indices (ANSindex sympathetic, ANSindex parasympathetic and balANSindex) were used to monitor ANS activity. Spectral analysis was performed using an autoregressive model with a parametric method. The low frequency (LF) and high frequency (HF) components were used to interpret the power spectral density of short-term electrocardiograms (ECGs). The relationship LF/(LF+HF) reflects sympathetic activity, HF/(LF+HF) indicates parasympathetic activity, and the LF/HF ratio gives the predominance of the system. Plasma concentrations of adrenaline, noradrenaline, and cortisol were determined at different times. Correlation (P < 0.01) was found between the balANSindex and adrenaline levels and between LF/HF ratio and plasma adrenaline concentrations. Moreover, a significant (P < 0.01) correlation was found between the balANSindex and LF/HF ratio. However, no correlation was seen between the registered ANSiscope indices and hemodynamic variables. The correlation seen in this study suggests that the balANSindex could be a useful tool to monitor ANS activity during anesthesia and surgery.

Pre‐operative measurement of heart rate variability predicts hypotension during general anesthesia

Peri-operative hymodynamic instability is one of the major concerns for anesthesiologists when performing general anesthesia for individuals with autonomic dysfunction. The purpose of this study was to examine the potential usage of pre-operative measurement of heart rate variability (HRV) in identifying which individuals, with or without diabetes, may be at risk of blood pressure (BP) instability during general anesthesia. We studied 46 patients with diabetes and 87 patients without diabetes ASA class II or III undergoing elective surgery. Participants' cardiovascular autonomic function and HRV were assessed pre-operatively, and hymodynamic parameters were monitored continuously intra-operatively by an independent observer. Only 6% of the participants were classified as having cardiovascular autonomic neuropathy (CAN) based on traditional autonomic function tests whereas 15% experienced hypotension. Total power (TP, P = 0.006), low frequency (LF, P = 0.012) and high frequency (HF, P = 0.028) were significantly lower in individuals who experienced hypotension compared with those who did not. Multivariate logistic regression analysis revealed that TP [odds ratio (OR) = 0.15, 95% confidence interval (CI) = 0.05-0.47, P = 0.001] independently predicted the incidence of hypotension, indicating that each log ms2 increase in total HRV lowers the incidence of hypotension during general anesthesia by 0.15 times. After stepwise multiple linear regression analysis (R2= 11.5%), HF (beta = -11.1, SE = 2.79, P < 0.001) was the only independent determinant of the magnitude of systolic blood pressure (SBP) reduction at the 15th min after tracheal intubation. Spectral analysis of HRV is a sensitive method for detecting individuals who may be at risk of BP instability during general anesthesia but may not have apparent CAN according to traditional tests of autonomic function.

Tai Chi versus brisk walking in elderly women

to compare the effects of a short style of Tai Chi versus brisk walking training programme on aerobic capacity, heart rate variability (HRV), strength, flexibility, balance, psychological status and quality of life in elderly women. nineteen community-dwelling, sedentary women (aged 71.4 +/- 4.5 years) were randomly assigned to Tai Chi Chuan (TCC; n = 11) or brisk walking group (BWG; n = 8). A separate group of elderly women was recruited from the same population to act as a sedentary comparison group (SCG; n = 8). The exercise groups met for 1 h, three days per week for 12 weeks. Outcomes measured before and after training included estimated VO2max, spectral analysis of HRV (high-frequency, low-frequency power as well as high- and low-frequency power in normalised units) as a measure of autonomic control of the heart, isometric knee extension and handgrip muscle strength, single-leg stance time, the State Trait Anxiety Inventory (STAI), Profile of Mood States (POMS) and Short Form-36 (SF-36) questionnaires. significant improvement was seen in estimated VO(2)max in the TCC group (TCC versus SCG P = 0.003, TCC versus BWG P = 0.08). The mean within-person change of high-frequency power in normalised units (HFnu) increased [8.2 (0.14-16.3)], representing increased parasympathetic activity, and low-frequency power in normalised units (LFnu) decreased [-8.7 (-16.8-0.5)], representing decreased sympathetic activity, in the TCC group only. Significant gains were also seen in the non-dominant knee extensor strength and single-leg stance time (TCC versus BWG P < 0.05). a short style of TCC was found to be an effective way to improve many fitness measures in elderly women over a 3-month period. TCC was also found to be significantly better than brisk walking in enhancing certain measures of fitness including lower extremity strength, balance and flexibility.

Hyperthyroidism is characterized by both increased sympathetic and decreased vagal modulation of heart rate: evidence from spectral analysis of heart rate variability

The clinical manifestations of hyperthyroidism resemble those of the hyperadrenergic state. This study was designed to evaluate the impact of hyperthyroidism on the autonomic nervous system (ANS) and to investigate the relationship between serum thyroid hormone concentrations and parameters of spectral heart rate variability (HRV) analysis in hyperthyroidism. Thirty-two hyperthyroid Graves' disease patients (mean age 31 years) and 32 sex-, age-, and body mass index (BMI)-matched normal control subjects were recruited to receive one-channel electrocardiogram (ECG) recording. The cardiac autonomic nervous function was evaluated by the spectral analysis of HRV, which indicates the autonomic modulation of the sinus node. The correlation coefficients between serum thyroid hormone concentrations and parameters of the spectral HRV analysis were also computed. The hyperthyroid patients revealed significant differences (P < 0.001) compared with the controls in the following HRV parameters: a decrease in total power (TP), very low frequency power (VLF), low frequency power (LF), high frequency power (HF), and HF in normalized units (HF%); and an increase in LF in normalized units (LF%) and in the ratio of LF to HF (LF/HF). After correction of hyperthyroidism in 28 patients, all of the above parameters were restored to levels comparable to those of the controls. In addition, serum thyroid hormone concentrations showed significant correlations with spectral HRV parameters. Hyperthyroidism is in a sympathovagal imbalanced state, characterized by both increased sympathetic and decreased vagal modulation of the heart rate. These autonomic dysfunctions can be detected simultaneously by spectral analysis of HRV, and the spectral HRV parameters could reflect the disease severity in hyperthyroid patients.

Unique Very Low-Frequency Heart Rate Variability During Deep Sleep in Humans

We investigate heart rate variability (HRV) in the very low-frequency (VLF) range (0.003-0.04 Hz) during deep sleep in good sleepers. Spectral analysis of HRV during deep sleep reveals consistent peaks at <0.04 Hz. By using wavelet analysis, we find both stationary and nonstationary periodic patterns in the VLF range, the presence of which has been discussed but has not been fully established to date. Although the mechanism(s) behind the unique VLF oscillations remain to be fully explored, we conjecture that there is an endogenous rhythmic component in human HRV in the VLF range. Further, our results also suggest a need for caution in the interpretation of the VLF spectral power in HRV during deep sleep.