LF To HF Research Articles

1P1-G05 手術支援システムの評価方法の検討 : 唾液と加速度脈波によるストレスの客観的な評価(手術支援ロボティクス・メカトロニクス)

We propose a method for using surgeon's biological information to evaluate the surgeon's stress in his/her using a surgical assistant system. We focused on saliva and acceleration plethysmogram as the surgeon's biological information. The stress was measured by analyzing cortisol, alpha-amylase, and total protein in saliva, and we analyzed the acceleration plethysmogram variability as the indexes of autonomic nervous activity, those were coefficient of variance of the a-a interval and low-frequency band [0.02-0.15Hz] power spectrum (LF), high-frequency band[0.15-0.5Hz] power spectrum (HF), the ratio of LF to HF (LF/HF). To validate the effectiveness of the proposed method, we conducted a laparoscopic cholecystectomy simulation. In conclusion, we confirmed our method had an ability to objectively evaluate the surgeon's stress during surgery.

Psychological and physiological responses to the rustling sounds of Korean traditional silk fabrics

The objectives of this study were to investigate physiological and psychological responses to the rustling sound of Korean traditional silk fabrics and to figure out objective measurements such as sound parameters and mechanical properties determining the human responses. Five different traditional silk fabrics were selected by cluster analysis and their sound characteristics were observed in terms of FFT spectra and some calculated sound parameters including level pressure of total sound (LPT), Zwicker’s psychoacoustic parameters — loudness(Z), sharpness(Z), roughness(Z), and fluctuation strength(Z), and sound color factors such as ΔL and Δf. As physiological signals, the ratio of low frequency to high frequency (LF/HF) from the power spectrum of heart rate variability, pulse volume (PV), heart rate (HR), and skin conductance level (SCL) evoked by the fabric sounds were measured from thirty participants. Also, seven aspects of psychological state including softness, loudness, sharpness, roughness, clearness, highness, and pleasantness were evaluated when each sound was presented. The traditional silk fabric sounds were likely to be felt as soft and pleasant rather than clear and high, which seemed to evoke less change of both LF/HF and SCL indicating a negative sensation than other fabrics previously reported. As fluctuation strength(Z) were higher and bending rigidity (B) values lower, the fabrics tended to be perceived as sounding softer, which resulted in increase of PV changes. The higher LPT was concerned with higher rating for subjective loudness so that HR was more increased. Also, compression linearity (LC) affected subjective pleasantness positively, which caused less changes of HR. Therefore, we concluded that such objective measurements as LPT, fluctuation strength(Z), bending rigidity (B), and compression linearity (LC) were significant factors affecting physiological and psychological responses to the sounds of Korean traditional silk fabrics.

Cardiac Autonomic Dysregulation in Patients with Acute Hepatitis

Autonomic dysfunction is common in patients with chronic liver disease, but it is still unclear whether acute hepatitis coincides with alterations in autonomic functions. We evaluated the heart rate variability (HRV) of 10 patients with acute hepatitis (6 males, 4 females; mean age, 44.0 y; range, 20-69 y). Frequency-domain analysis of short-term and stationary R-R intervals was performed on the first day of admission to detect low-frequency power (LF; 0.04-0.15 Hz), high-frequency power (HF, 0.15-0.40 Hz), the ratio of LF to HF (LF/HF), and LF in normalized units (LF%). The same measurement was repeated on the 7th day of admission. We found that there was a significant increase of HF as well as variance of the R-R interval on the 7th day after admission (P < 0.05). There was a significant negative correlation between HF and the change of total bilirubin (P < 0.05). The study demonstrates a change in cardiac vagal tone associated with acute hepatitis by analysis of HRV, and such alteration is less pronounced later during the clinical course of acute hepatitis.

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.

Effects of acupuncture on heart rate variability in normal subjects under fatigue and non-fatigue state

The objective of this study was to assess the effects of acupuncture applied at Hegu (LI 4) points and Neiguan (PC6) points on heart rate variability (HRV) in normal subjects under fatigue and non-fatigue states using power spectral analysis. Twenty-nine normal male subjects were randomly divided into three groups. Subjects in Group A and Group B performed a simulated driving task for 3 h and acupuncture needles were then inserted perpendicularly into the LI 4 points in the middle of the dorsal thenar muscle and PC 6 points situated between the tendons of the palmaris longus and carpi radialis muscles for 15 min for Group A but inserted subcutaneously to the acupuncture points for Group B as a control. Acupuncture needles were directly inserted perpendicularly into the LI 4 points and PC 6 points for 15 min for Group C. Stimulations of the acupuncture points induced a significant decrease in heart rate (HR), HRV total power (TP), low frequency (LF) power and ratio of low frequency to high frequency (LF/HF), and a significant increase in the HF power in normalized units (NU) during the post stimulation period in fatigue state (P<0.05). Stimulation of acupuncture points resulted in a significant increase both in the LF power and HF power in absolute units (AU) (P<0.05) but no significant change in NU was found during the post stimulation period in non-fatigue state. It was concluded that the modulating effect of acupuncture on heart rate variability not only depended on the points of stimulation such as acupuncture or non-acupuncture points but also on the functional state of the subject, namely whether the subjects are in a state of fatigue or not.

Effect Of Arm Powered Passive Leg Cycling On Heart Rate Variability In Spinal Cord Injured

Heart rate variability (HRV) has emerged as a reproducible, non-invasive technique to assess autonomic influences on the heart. Studies have shown that exercise in ablebodied individuals decreases high frequency (HF) and low frequency (LF) components of HRV. The effect of arm powered passive leg exercise on HRV in spinal cord injured (SCI) individuals is not known. PURPOSE The purpose of this investigation was to determine the effects of an acute bout of exercise on cardiac autonomic function in SCI as indicated by time and frequency-domain measures of HRV. METHODS HRV values were obtained (Welch Allyn CardioPerfectTM, Skareateles Falls, NY) during 300 sec recordings from three paraplegic and two tetraplegic SCI subjects (mean age: 33.4 ± 20.1 yrs, range 21–69 yrs) at rest (W0) and immediately following an acute bout of passive exercise on the PsycleTM (Intellifit, Inc., Wichita Falls, TX) at a target heart rate of 65% of age-adjusted maximum (W1). Frequency domain measures were calculated by Fast Fourier Transform including high frequency (HF, 0.15–0.4 Hz), low frequency (LF, .04−.15 Hz), and the ratio of LF to HF (LF/HF). A 2X2 ANOVA was used to identify changes in LF, HF, LF/HF and the raw time domain data obtained from R-R intervals from W0 to W1. RESULTS No significant difference (P >.05) was determined between paraplegic and tetraplegic individuals on criterion measures from W0 to W1. Arm powered passive leg cycling was accomplished for 35 min at 35±17.5 rpm, for 1227±663 total revolutions, at 9.7±6.8 W, and at heart rates of 122±22 bpm. Mean HF values (ms2) were reduced from 423±427 to 30±30 [F 1,6) = 12.1, p< 0.05] for W0 and W1, respectively. Mean LF values (ms2) were 692±841 and 104±142 [F(1,6) = 2.3, P>.05), respectively for W0 and W1. Mean LF/HF values were 1.8±1.3 and 2.7±1.3 [F (1,6) = 2.4, P>.05) for W0 and W1, respectively. Mean R-R intervals were reduced from 810±60 to 655±109 ms [F (1,6) = 7.8, p<.05] for W0 and W1, respectively. Although LF did not reach statistical significance, the tendencies of reduced HF and LF values with exercise is consistent with reported responses from able-bodied subjects. CONCLUSION These data suggest that arm powered passive leg cycling produces a shift in autonomic influences on the heart of spinal cord injured.

Effect Of Arm Powered Passive Leg Cycling On Heart Rate Variability In Spinal Cord Injured

Heart rate variability (HRV) has emerged as a reproducible, non-invasive technique to assess autonomic influences on the heart. Studies have shown that exercise in ablebodied individuals decreases high frequency (HF) and low frequency (LF) components of HRV. The effect of arm powered passive leg exercise on HRV in spinal cord injured (SCI) individuals is not known. PURPOSE The purpose of this investigation was to determine the effects of an acute bout of exercise on cardiac autonomic function in SCI as indicated by time and frequency-domain measures of HRV. METHODS HRV values were obtained (Welch Allyn CardioPerfectTM, Skareateles Falls, NY) during 300 sec recordings from three paraplegic and two tetraplegic SCI subjects (mean age: 33.4 ± 20.1 yrs, range 21–69 yrs) at rest (W0) and immediately following an acute bout of passive exercise on the PsycleTM (Intellifit, Inc., Wichita Falls, TX) at a target heart rate of 65% of age-adjusted maximum (W1). Frequency domain measures were calculated by Fast Fourier Transform including high frequency (HF, 0.15–0.4 Hz), low frequency (LF, .04−.15 Hz), and the ratio of LF to HF (LF/HF). A 2X2 ANOVA was used to identify changes in LF, HF, LF/HF and the raw time domain data obtained from R-R intervals from W0 to W1. RESULTS No significant difference (P >.05) was determined between paraplegic and tetraplegic individuals on criterion measures from W0 to W1. Arm powered passive leg cycling was accomplished for 35 min at 35±17.5 rpm, for 1227±663 total revolutions, at 9.7±6.8 W, and at heart rates of 122±22 bpm. Mean HF values (ms2) were reduced from 423±427 to 30±30 [F 1,6) = 12.1, p< 0.05] for W0 and W1, respectively. Mean LF values (ms2) were 692±841 and 104±142 [F(1,6) = 2.3, P>.05), respectively for W0 and W1. Mean LF/HF values were 1.8±1.3 and 2.7±1.3 [F (1,6) = 2.4, P>.05) for W0 and W1, respectively. Mean R-R intervals were reduced from 810±60 to 655±109 ms [F (1,6) = 7.8, p<.05] for W0 and W1, respectively. Although LF did not reach statistical significance, the tendencies of reduced HF and LF values with exercise is consistent with reported responses from able-bodied subjects. CONCLUSION These data suggest that arm powered passive leg cycling produces a shift in autonomic influences on the heart of spinal cord injured.

Physiological and Subjective Evaluation of the Rustling Sounds of Polyester Warp Knitted Fabrics

This study evaluates the rustling sounds of polyester warp knitted fabrics using a psychophysiological technique. We generate and record the rustling sounds of three structural types—reverse locknit, double denbigh, and sharkskin—of warp knitted fabrics, all made from 75D polyester filament yarn at the same density. To obtain quantitative information about rustling sounds, Zwicker’s psychoacoustic parameters—loudness( z), sharpness( z), roughness( z), and fluctuation strength( z)—are calculated from sound spectra obtained by FFT analysis. We acquire physiological signals—electroencephalogram, the ratio of low frequency to high frequency (LF/HF) from the power spectrum of heart rate variability, respiration rate (RESP), heart rate (HR)—from fourteen female participants when each sound is presented to them, and they rate seven sensations—softness, pleasantness, comfort, noisiness, annoyance, clearness, and highness—by free modulus magnitude estimation. Loudness( z), roughness( z), and fluctuation strength( z) are highest for the sharkskin and lowest for the reverse locknit. The rustling sound of double denbigh appears to be related to a positive sensation, with the highest softness, pleasantness, and comfort, and the lowest beta wave and LF/HF. On the other hand, the sharkskin sound appears to evoke negative sensations, with the highest annoyance and noisiness and most increasing beta wave, RESP, HR, and LF/HF. Therefore, we conclude that psychoacoustic parameters such as loudness( z), roughness( z), and fluctuation strength( z) affect psychological and physiological responses evoking negative sensations for warp knitted fabric sounds.

Effects of estrogen on gender-related autonomic differences in humans.

Our previous studies demonstrated that premenopausal women have dominant vagal and subordinate sympathetic activity compared with age-matched men. This study was designed to investigate the role of estrogen in gender-related autonomic differences. We evaluated the heart rate variability of four healthy groups: age-matched postmenopausal women without hormone replacement therapy (PM), postmenopausal women on conjugated estrogen replacement therapy (PME), men, and non-age-matched premenopausal women (PreM). Frequency-domain analysis of short-term and stationary R-R intervals was performed to evaluate low-frequency power (LF; 0.04-0.15 Hz), high-frequency power (HF; 0.15-0.40 Hz), the ratio of LF to HF (LF/HF), and LF in normalized units (LF%). No gender-related autonomic differences existed between the PM and men groups, but they did exist between the PME and men group. Compared with the PreM group, the PM group had a lower HF and higher LF% and LF/HF. Compared with the PM group, the PME group had a higher HF but lower LF% and LF/HF. These results suggest that conjugated estrogen replacement therapy may facilitate vagal and attenuate sympathetic regulation of heart rate in postmenopausal women. In addition, estrogen may play an important role in gender-related autonomic differences.

Spectral analyses of electroencephalography and heart rate variability during sleep in normal subjects

We investigated the relationship between electroencephalogram (EEG) activity and autonomic nervous system function using spectral analyses of EEG and heart rate variability (HRV) in healthy subjects during sleep. Eleven subjects were enrolled in this study. From EEG, the spectral edge frequencies (SEFs including SEF50, SEF90 and SEF95) were calculated. From electrocardiogram (ECG), the spectral powers of low-frequency band (LF: 0.04–0.15 Hz), high-frequency band (HF: 0.15–0.4 Hz) and the ratio of LF to HF (LF/HF) were calculated. During sleep, each set of data was obtained as the average of a 5-min measurement. We found that SEFs and LF/HF or LF decreased simultaneously and periodically, suggesting simultaneous depression of EEG activity and relative sympathetic activity, and SEFs significantly correlated with LF/HF and LF in all subjects during sleep, but not with HF. The existence of a clear correlation of SEFs with LF or LF/HF may offer a simple approach to estimate the relationship between EEG activity and autonomic nervous system function during sleep.

Liver Fibrosis: What's the Beginning of Autonomic Deficit?

Histologic diagnoses were made using standard criteria and two independent observers scored all samples using the Scheuer staging system (3). We distinguished between patients affected by moderate e brosis (scores 2 and 3) and those affected by severe e brosis, corresponding to cirrhosis (score 4). Cardiac index was determined using pulsed-wave Doppler echocardiography (Hewlett-Packard Sonos 2000, Andover, Mass., USA). Peripheral vascular resistance (PVR) was calculated as the mean arterialpressure/cardiacoutput £80.Heartratevariabilitywas evaluated in the frequency domain using appropriate software (Rozinn Electronics H4W 3.6F, Glendale, N.Y., USA). A series of consecutive 5-min intervals was calculated from the Holter ECG as a function of beat numbers. Power spectral analysis of the intervals between adjacent R waves of the electrocardiogram (RR) was performed using the fast Fourier transform mathematical function (5). Low frequency (LF; 0.04‐0.15 Hz) and high frequency (HF; 0.15‐0.40 Hz) spectral powers and the ratio of LF to HF (LF/HF) were calculated and expressed in normalized units (nU). The recordings were obtained with 5 min in the supine position and 5 min in passive head-up tilt (70°). Statistical analysis was performed using an appropriate t test. P values lower than 0.05 were regarded as statistically signie cant. None of the patients included in this study, with either chronic viral hepatitis or with cirrhosis, showed evidence of hyperdynamic circulation. Cardiac index and peripheral vascular resistances were not signie cantly different from those of healthy subjects. Moreover, our results showed no differences between patients and controls in mean systolic and diastolic arterial pressures, either in the supine or in the tilt position. The power spectral analysis showed the occurrence of a

Physiological Responses Evoked by Fabric Sounds and Related Mechanical and Acoustical Properties

This study is performed to determine the characteristics of fabric sounds and the mechanical properties to predict their auditory comfort. In order to obtain quantitative information about emotional changes evoked by fabric sounds, physiological signals are acquired and analyzed when each fabric sound is presented to participants. Physiological parameters employed in this study are electroencephalogram and autonomic nervous system activities, including photoplethysmogram (PPG), skin conductance level (SCL), and the ratio of low frequency to high frequency (LF/HF) from the power spectrum of heart rate variability. As sound parameters, the pressure level of total sound (LPT), loudness(z), and sharpness(z) are calculated. Mechanical properties of the fabrics are measured with the KES-FB system. Bending hysteresis and weight. reflect negative sensations, influencing slow alpha, LF/HF, and SCL. Among sound parameters, LPT, loudness(z), and sharpness(z) influence negative sensations, causing the increment of SCL and LF/HF with the decrement of slow alpha and PPG.

Cardiovascular and sympathetic responses to dental surgery with local anesthesia.

We investigated changes in blood pressure and blood variables, including plasma catecholamines, serum glucose and insulin concentrations, during dental surgery. The study included 11 normotensive patients (age, 22.5+/-0.7 years) who underwent tooth extraction at Kyushu Dental College Hospital. Three to 7 days prior to dental surgery, blood pressure, pulse rate, and heart rate variability were measured every 30 min over 24 h. The low frequency (LF: 0.05 to 0.15 Hz) and high frequency (HF: 0.15 to 0.40 Hz) powers were calculated, and the ratio of LF to HF (LF/HF) and HF were used as indexes of sympathetic and parasympathetic activities, respectively. Lidocaine, 2% with epinephrine (1:80,000), was used as the local anesthetic for all patients. Systolic blood pressures significantly increased during dental surgery (+10.8+/-3.5 mmHg); however, this increase failed to correlate not only with baseline systolic blood pressure but with 24-h averaged blood pressures, LF/HF or HF. On the other hand, plasma epinephrine and norepinephrine concentrations increased during dental surgery, and peak values of these variables were obtained after local anesthesia and during tooth extraction, respectively. Serum glucose level increased after local anesthesia (control vs. local anesthesia: 5.16+/-0.11 vs. 5.62+/-0.10 mmol/l; p<0.01); however, plasma insulin concentrations did not change significantly. These results suggest that 1) ambulatory measurements of blood pressure and heart rate variability over 24 h cannot predict the responses of blood pressure during dental surgery, and that 2) administration of local anesthetic and tooth extraction activate sympathoadrenal outflow, resulting in an increase in serum glucose level in normotensive subjects.

Heart rate variability of children with mitral valve prolapse

Studies have indicated that adult patients with mitral valve prolapse (MVP) may have autonomic dysfunction. The purpose of this study was to evaluate heart rate variability (HRV) in children with MVP. Sixty-seven children with MVP (ages 6 to 18 years; 30 boys and 37 girls) were consecutively studied and subdivided into those with or without symptoms. Thirty-seven normal age-matched children (17 boys and 20 girls) were studied as controls. The patients were further divided into 4 age subgroups. HRV was measured using a 24-hour Holter electrocardiogram (ECG) system (Laser SXP Holter Analysis System, Marquette Electronics, Milwaukee, WI). The ECGs were analyzed in both time domain and frequency domain (spectral analysis). Symptomatic and asymptomatic children with MVP were combined for analysis because they were not significantly different in terms of their HRV. All time-domain indices, with the exception of SDANN (SD of the mean of RR intervals in all 5-minute segments of the 24-hour ECG), were significantly lower in children with MVP than in controls. Children with MVP showed significantly lower spectral power of the high frequency (HF) and low frequency (LF) components when compared with controls. The ratio of LF to HF (LF/HF) was significantly higher in children with MVP. Similar differences were observed in the 4 age subgroups. Sex differences in HRV were observed when girls had lower HRV compared with boys. Lower time-domain and frequency-domain indices of HRV in children with MVP are suggestive of decreased parasympathetic activity and a shift in sympathovagal balance. Various factors including differences in heart rate may contribute to sex differences in HRV.

Preeclamptic pregnancy is associated with increased sympathetic and decreased parasympathetic control of HR.

Previous work from our laboratory using heart rate variability (HRV) has demonstrated that women before menopause have a more dominant parasympathetic and less effective sympathetic regulations of heart rate compared with men. Because it is still not clear whether normal or preeclamptic pregnancy coincides with alternations in the autonomic functions, we evaluated the changes of HRV in 17 nonpregnant, 17 normotensive pregnant, and 11 preeclamptic women who were clinically diagnosed without history of diabetic neuropathy, cardiac arrhythmia, and other cardiovascular diseases. Frequency-domain analysis of short-term, stationary R-R intervals was performed to evaluate the total variance, low-frequency power (LF; 0.04-0.15 Hz), high-frequency power (HF; 0.15-0.40 Hz), ratio of LF to HF (LF/HF), and LF in normalized units (LF%). Natural logarithm transformation was applied to variance, LF, HF, and LF/HF for the adjustment of the skewness of distribution. We found that the normal pregnant group had a lower R-R value and HF but had a higher LF/HF and LF% compared with the nonpregnant group. The preeclamptic group had lower HF but higher LF/HF compared with either the normal pregnant or nonpregnant group. Our results suggest that normal pregnancy is associated with a facilitation of sympathetic regulation and an attenuation of parasympathetic influence of heart rate, and such alterations are enhanced in preeclamptic pregnancy.

Left Ventricular Mass Predicted by a Single Reading of Ambulatory Blood Pressure in Essential Hypertension.

The spectral power of heart rate variability has been shown to be negatively correlated with left ventricular mass (LVM), suggesting the contribution of left ventricular hypertrophy to autonomic dysfunction in essential hypertension. However, a simultaneous assessment of autonomic function and ambulatory blood pressure in relation to LVM has not been carried out. The objective of the present study was to elucidate the synergistic effects of ambulatory blood pressure and autonomic nerve activity on the heart. We enrolled 25 ambulant patients with untreated essential hypertension (9 men and 16 women; mean age 50.6 +/- 2.0 years). The ambulatory blood pressure and heart rate variability were simultaneously monitored every 30 min for 24 h. The spectral power of high-frequency (HF: 0.15 to 0.4 Hz) and low-frequency (LF: 0.05 to 0.15 Hz) bands were measured, and the ratio of LF to HF (LF/HF) was calculated. LF/HF and HF were used as indexes of sympathetic and parasympathetic activities, respectively. LVM was determined by echocardiography. Both the average daytime and nighttime systolic ambulatory blood pressures significantly correlated with the LVM index (r= 0.644, p< 0.001; and r= 0.428, p< 0.05; respectively), although there was no such correlation with the clinic blood pressures. In contrast, a single reading of ambulatory systolic blood pressure measured when LF/HF reached a maximum value was significantly correlated with the LVM index independently of age and sex (partial r= 0.484, p< 0.05). These results suggest that the ambulatory systolic blood pressure during increases in the activity of the sympathetic nervous system is able to infer LVM in essential hypertension.

Effect of aging on gender differences in neural control of heart rate.

To clarify the influence of gender on sympathetic and parasympathetic control of heart rate in middle-aged subjects and on the subsequent aging process, heart rate variability (HRV) was studied in normal populations of women (n = 598) and men (n = 472) ranging in age from 40 to 79 yr. These groups were divided into eight age strata at 5-yr intervals and were clinically diagnosed as having no hypertension, hypotension, diabetic neuropathy, or cardiac arrhythmia. Frequency-domain analysis of short-term, stationary R-R intervals was performed, which reveals very-low-frequency power (VLF; 0.003-0.04 Hz), low-frequency power (LF; 0.04-0.15 Hz), high-frequency power (HF; 0.15-0.40 Hz), the ratio of LF to HF (LF/HF), and LF and HF power in normalized units (LF% and HF%, respectively). The distribution of variance, VLF, LF, HF, and LF/HF exhibited acute skewness, which was adjusted by natural logarithmic transformation. Women had higher HF in the age strata from 40 to 49 yr, whereas men had higher LF% and LF/HF between 40 and 59 yr. No disparity in HRV measurements was found between the sexes in age strata >/=60 yr. Although absolute measurements of HRV (variance, VLF, LF, and HF) decreased linearly with age, no significant change in relative measurements (LF/HF, LF%, and HF%), especially in men, was detected until age 60 yr. We conclude that middle-aged women and men have a more dominant parasympathetic and sympathetic regulation of heart rate, respectively. The gender-related difference in parasympathetic regulation diminishes after age 50 yr, whereas a significant time delay for the disappearance of sympathetic dominance occurs in men.

Autonomic nervous system activity during infusion of L-arginine in patients with liver cirrhosis.

Patients with liver cirrhosis exhibit a hyperdynamic circulatory state as evidenced by tachycardia and an increase in cardiac output accompanied by an elevation of sympathetic tone. This condition is due to the excessive release of nitric oxide (NO), an endogenous vasodilator, which is in turn related to the abnormal induction of NO synthase. The present study investigated whether the intravenous infusion of L-arginine, the precursor of NO, may cause a similar hyperdynamic circulatory state. A new method, the analysis of power spectrum heart rate variability, was used to evaluate autonomic nervous activity. Twenty patients with liver cirrhosis underwent continuous Holter monitoring of the ECG during the intravenous administration of L-arginine (10 g) (Fisher's solution) infused over 60 min. Power spectral analysis was computed from 512 beats of the Holter ECG data. Low frequency (LF; 0.04-0.15 Hz) and high frequency (HF; 0.15-0.40 Hz) spectral powers and the ratio of LF to HF (LF/HF) were calculated every 10 min before and after the infusion of L-arginine. The LF power, which reflects sympathetic tone modified by vagal tone, and the LF/HF, an indicator of sympathetic tone, were both significantly increased during the infusion (p<0.05). HF power, an indicator of parasympathetic tone, showed no significant change in the early stage of the infusion but was significantly increased in the late stage (p<0.05). The administration of L-arginine thus led to an elevation of sympathetic tone. Fisher's solution, which is administered to patients with hepatic insufficiency, contains L-arginine, and may also produce a hyperdynamic circulatory state as an adverse effect related to an elevation of the plasma level of NO by L-arginine. The monitoring of such patients is thus indicated.

Disturbed Autonomic Activity Precedes Ischemic Episodes in Patients with Variant Angina

BackgroundWhile the autonomic nervous system is known to be involved in the pathogenesis of variant angina, the relationship between disturbed autonomic activity and ischemic episodes in patients with variant angina has not been determined.MethodsWe performed 24‐hour Holter monitoring and power spectral analysis of heart rate variability (HRV) in ten patients with variant angina. The low frequency (0.04–0.15 Hz [LF]) and high frequency (0.15–0.40 Hz [HF]) components of HRV were quantified. The ratio of LF to HF (LF/HF) and the coefficient of the RR interval variation (CV) were also calculated. We analyzed HRV every 10 minutes beginning 50 minutes before the onset of ischemic episodes confirmed by ST segment elevation.ResultsThe LF/HF from 40 to 30 minutes before ischemia was decreased compared with the value from 50 to 40 minutes before ischemia (0.80 ± 0.15 vs 1.63 ± 0.44, mean ± SE, P = 0.037). The LF/HF then began to increase, and the value from 20 to 10 minutes (2.91 ± 0.66) was significantly greater than that from 40 to 30 minutes (P &lt; 0.01). The CV was increased from 30 to 20 minutes before ischemia compared with the CV from 50 to 40 minutes (8.5%± 1.6% vs 5.2%± 0.8%, P = 0.033). The LF/HF and the CV remained increased until the onset of ischemia.ConclusionsData suggests that a disturbed autonomic nervous activity plays an important role in the initiation of coronary vasospasm in patients with variant angina. A.N.E. 1997;2(4):313–318

Circadian variation of QT interval dispersion: Correlation with heart rate variability

The circadian variation of QT interval dispersion and its correlation with heart rate variability (HRV) was examined in 17 normal subjects by using 24-hour recordings of three-lead electrocardiograms. Measurements of HRV, R-R intervals, and QT intervals were made for the first 6 minutes of each hour over a 24-hour period. Spectral analysis of HRV yielded low-frequency power (LF) (0.04–0.15 Hz), high-frequency power (HF) (0.15–0.40 Hz), and the ratio of LF to HF (LF/HF). A rate-corrected QT interval (QTc) was calculated by Bazett's formula, and QT and QTc dispersion was defined as the difference between the maximum and minimum values in any two leads. High-frequency power and QT interval were greater at night than during the day; conversely, LF/HF and dispersion of QT and QTc were greater during the day. The QTc interval remained virtually unchanged throughout the 24-hour period. The dispersion of QTc showed a significant negative correlation with HF and a significant positive correlation with LF/HF. The results suggest that an increased sympathetic tone or a decreased vagal tone increases QT dispersion in healthy subjects.