Autonomic Imbalance Assessed by Heart Rate Variability Analysis in Vasovagal Syncope

In this prospective study, the autonomic modulation of the sinus node of 12 patients (mean age 28 ± 7 years) suffering from vasovagal syncope (VVS) was compared to that of 11 sex and age matched control patients (mean age 32 ± 4 years) by analysis of heart rate variability. Spectral indices (low frequency power [Plf], high frequency power [Phf], total power [Pt], sympathovagal balance [LF/HF]) and temporal indices, the mean of all coupling intervals between normal beats (mRR), the standard deviation about the mean (sdRR), the percentage of adjacent R to R intervals differing by more than 50 msec (pNN50), and the root mean square of variations in successive R to R intervals (rMSSD) were compared at baseline and during head-up tilt between and within groups. Baseline results were similar in both groups. During tilt testing, comparison of results between groups revealed only significantly higher sdRR and rMSSD and lower LF/HF ratio in VVS patients. Within WS patients, comparison of temporal and spectral analysis between baseline and tilt showed a significant increase of most indices (Plf, Phf, Pt, sdRR, and rMSSD) but a comparable LF/HF ratio; in contrast, control patients exhibited only a significant increase of LF/ HF ratio. In conclusion. VVS patients who developed vasovagal syncope during head-up tilt demonstrated a nonreciprocal modulation of the sinus node by the autonomic nervous system indicative of a pronounced physiological sympathetic surge along with a paradoxical vagal input to the cardiovascular system.     

Power spectral analysis of heart rate variability in HIV-infected and AIDS patients

Background: In HIV‐infected patients the risks for cardiovascular disease are multifactorial. Autonomic dysfunction has been detected in the early phase of HIV infection as well as in AIDS patients with advanced cardiomyopathy. Methods: Forty AIDS patients receiving highly active antiretroviral therapy (HAART), 40 HIV+ naïve of HAART, and 40 control subjects were studied. Computerized analysis of heart rate variability was performed using an analog to digital converter. R‐R intervals were obtained from a standard ECG, recorded in DII lead in supine rest and after the cold‐face and tilt tests. The series of R‐R intervals were assessed in time and frequency domains using an autoregressive algorithm. Results: There was no difference regarding to mean values of R‐R intervals and variance in baseline. The normalized power of the low‐frequency (LF) component and the low‐frequency/high‐frequency (HF) ratio (LF/HF) was significantly decreased in the HIV group. Responses of normalized HF and LF/HF ratio during the cold‐face test were significantly decreased in the HIV group, as compared to the control. During the tilt test, a higher augmentation of normalized LF and the LF/HF ratio was observed in the HIV group compared with the control. The AIDS group was similar to the control in baseline and after cold‐face and tilt tests. Conclusion: The HIV group presented in baseline conditions, a shift of cardiac sympathovagal balance, an exacerbated response of the LF component during the tilt test, and an ineffective cardiac vagal response to the cold‐face test suggesting sympathetic and parasympathetic dysfunction. AIDS patients receiving HAART did not present these autonomic alterations.     

罗哌卡因与布比卡因腰麻对心率变异性的影响

目的 评估罗哌卡因腰麻对心率变异性的影响及其安全性。方法 80例患者随机分为2组：罗哌卡因组（R）和布比卡因组（B）,每组40例。在分别予0．5％的罗哌卡因和布比卡因蛛网膜下腔给药后,监测并记录注药前、注药后5min、10min、20min时MAP、HR、LF、HF、LF／HF、TF数值。结果 罗哌卡因组LF、TF、LF／HF均呈下降趋势,10min和20min数值与基础值比较具有显著性（P〈0.05）;布比卡因组MAP、LF、TF、LF／HF下降明显,给药后5min数据与基础值比较具有显著性（P〈0．05）,10min、20min数值与基础值比较具有非常显著性（P〈0．01）;组间比较,布比卡因组MAP、TF、5min LF、LF,／HF与同时段罗哌卡因组比较有显著性差异（P〈0．05）,10min和20min LF、LF／HF差异具有非常显著性（P〈0．01）;两组患者HR和HF虽也呈下降趋势,但与基础值比较并不具有显著性（P〉0．05）。结论 0．5％的罗哌卡因腰麻对心率变异性的影响要显著小于同浓度的布比卡因,该浓度的罗哌卡因腰麻安全性要高于布比卡因。     

Heart rate variability in diabetes patients

Diabetes mellitus can cause cardiovascular autonomic neuropathy and is associated with increased cardiovascular deaths. We investigated cardiovascular autonomic neuropathy in diabetics and healthy controls by analysis of heart rate variability. Thirty-one diabetics and 30 age- and sex-matched controls were included. In the time domain we measured the mean R - R interval (NN), the standard deviation of the R - R interval index (SDNN), the standard deviation of the 5-min R - R interval mean (SDANN), the root mean square of successive R - R interval differences (RMSSD) and the percentage of beats with a consecutive R - R interval difference > 50 ms (pNN50). In the frequency domain we measured high-frequency power (HF), low-frequency power (LF) and the LF/HF ratio. Diabetes patients had lower values for time-domain and frequency-domain parameters than controls. Most heart rate variability parameters were lower in diabetes patients with chronic complications than in those without chronic complications.     

Autonomic Nervous System Changes in Vasovagal Syncope:

Spectral analysis of heart rate variability was used to compare the changes in autonomic function during tilting in young and older patients with vasovagal syncope. Twenty-four young (age 28 +/- 8 years) and 31 older (56 +/- 5 years) patients with unexplained syncope and a positive tilt test and 25 controls (age 48 +/- 12 years) were included in the study. Frequency-domain measurements of the low (LF) (0.06-0.15 Hz) and high (HF) (0.15-0.40 Hz) frequency bands and the ratio of LF to HF were computed from Holter recordings for 4-minute intervals before and immediately after tilting and just before the end in all groups. Syncopal patients showed a different pattern of response to tilting from controls in all spectral indexes. Young and older patients showed the same pattern of changes in all measurements, even though certain differences were observed. The LF after tilting reduced more in the older (-20 +/- 7% vs -14 +/- 5%, P < 0.001), while HF reduced more in young patients (-17 +/- 8% vs -8 +/- 3%, P < 0.001). Young patients showed mainly a cardioinhibitory type (71%) of response whereas a vasodepressor type response predominated (68%) in the older patients. The autonomic nervous system appears to play an important role in the pathophysiological mechanism of vasovagal syncope. This role is similar in young and in older patients and this should be taken into account in the therapeutic approach to the condition. Specific differences between age groups may be related to the type of vasovagal syncope.     

Autonomic Effects of Dipyridamole Stress Testing on Frequency Distribution of RR and QT Interval Variability

Transient myocardial ischemia and associated changes in the autonomic nervous system may influence heart rate and ventricular repolarization to variable degrees. This study evaluated the effect of dipyridamole (DIP) induced ischemia on the autonomic balance by spectral analysis of RR and QT intervals variability. Patients with coronary artery disease undergoing DIP stress echocardiography were studied. From high resolution ECG recordings, RR and QT interval measurements were performed by a dynamic template-matching algorithm. A time-variant analysis was used to estimate power in the LF (0.05–0,15 Hz) and in the HF (0.15–0.4 Hz) band of RR and QT interval spectra. Patients were grouped in ischemic and nonischemic subgroups based on the echocardiographic detection of wall-motion abnormalities. In patients without ischemia (n = 28), DIP caused a decrease in LF power and an increase in HF power of the RR and QT interval variability, indicating concordant changes of both intervals. In contrast, patients with inducible ischemia (n = 11) showed a decrease in HF power of the RR interval spectra and an increase of HF power of QT interval spectra. Furthermore, LF power was increased for RR but decreased for QT interval spectra. Our study suggests that DIP induced ischemia causes a loss of autonomic coupling between heart rate and ventricular repolarization for sympathetic and parasympathetic activities. This lability in ventricular repolarization may constitute an arrhythmogenic substrate during acute ischemia in patients with coronary artery disease.     

Respiratory effects on the reproducibility of cardiovascular autonomic parameters

The aim of this study was to assess the influence of breathing pattern on the reproducibility of the most commonly used heart rate and blood pressure variability parameters and baroreflex indices. 5-5 min ECG and blood pressure recordings were made and repeated for 10 healthy volunteers in supine rest on 10 consecutive days during spontaneous and 6 min(-1) patterned breathing. We investigated the following parameters: mean RR interval (RRI); the standard deviation of RR intervals (SDRR); the root mean square of successive differences in RRI (RMSSD); the percentage of RRIs which differed by 50% from the proceeding RRI (PNN50); mean systolic arterial pressure (SAP); the standard deviation of SAP (SAP SD); mean mean arterial pressure (MAP); mean diastolic blood pressure (DAP) and baroreflex indices from spontaneous sequence method (upBRS and downBRS) and from cross spectral analysis (LF alpha, HF alpha). To assess reproducibility for each parameter within- and between-subject variability values were calculated and the ratio of within- and between-subject variability was assessed. In addition, we calculated intraclass correlation coefficient (ICC). Compared to spontaneous respiration during 6 min(-1) patterned breathing the heart rate and blood pressure variability increased; upBRS, LF alpha and HF alpha increased, downBRS did not change. However, ICC showed good reproducibility for most parameters, which did not improve further with controlled breathing. In conclusion, respiration had a strong influence on the most widely used cardiovascular autonomic parameters. The controlling of breathing did not result in consistent improvement in their reproducibility.     

Frequency-domain analysis of heart rate variability during positive and negative head-up tilt test: importance of age

The study of autonomic behavior during a head-up tilt test (HUT) has been deemed important to understand the loss of consciousness mechanism. Though HRV in patients with HUT(+) and HUT(-) has been compared, few trials emphasized the importance of age. HRV in frequency domain was analyzed based on 5-minute samples in the supine position, and between 5 and 10 minutes during early tilt test (R1) in 102 patients with one or more episodes of syncope (mean age 44.3 +/- 20.8, range 15-85 years, 55 women). Two subgroups were selected afterwards: (1) young patients between 15 and 35 years of age (41 patients) and (2) elderly patients aged 60 or more (36 patients). The following parameters were taken into account: the sum of low (LF) and high frequency (HF) (LF and HF in absolute values and in normalized units), the LF/HF ratio (L/H ratio), and the percentage of change between baseline and R1 values. The HRV behavior in young and elderly patients with positive and negative HUT was established. We then analyzed the correlation between HRV and age and HUT outcome. A multiple regression analysis encompassing age, HUT outcome, gender, and number of syncope episodes was performed. In young patients, the LF and HF areas and the L/H ratio changed significantly between baseline and R1. The L/H ratio increases from baseline to R1. Conversely, these differences were not significant in the elderly. No differences between HUT(+) and HUT(-) within the same age group were observed. Age related significantly to practically all HRV parameters analyzed, whereas the tilt test outcome correlates poorly with HF normalized units and LF normalized units during R1, and the L/H ratio changes between baseline and R1. By means of a multivariate analysis, only age shows a significant correlation with the HRV values. Despite an all age triggering of vasovagal syncope during HUT, the young and elderly patients' autonomic behavior differs. The young considerably increase their sympathovagal balance during HUT, whereas the elderly have a mitigated autonomic response. No significant differences were observed during the first minutes of the test between those with a HUT(+) and those with a HUT(-) within the same age group. Age, and not the HUT response, is the major determinant of the autonomic behavior during early HUT.     

Autonomic Nervous System Activity During Tilt Testing in Syncopal Patients, Estimated by Power Spectral Analysis of Heart Rate Variability

Spectral analysis of heart rate variability (HRV) was used to assess changes in autonomic function before and during postural tilt in 28 syncopal patients: 14 (group A) with positive and 14 (group B) with negative tilting test, and 14 normal controls (group C). Frequency-domain measurements of the high (HF) and low (LF) frequency bands and the ratio LF/HF were derived from Holter recordings, computed by Fast Fourier analysis for 4-minute intervals immediately before tilt testing, immediately after tilting, and just before the end of the test. In group A, the mean values of LF and HF decreased slightly in response to tilting while the LF/HF ratio increased, though these changes were not statistically significant. All parameters showed a statistically significant increase just before the onset of syncope. In group B, there were no significant changes in the parameters measured throughout the test. In group C. there was an increase in the LF and LF/HF ratio and a decrease in the HF immediately after tilting. There were no further significant changes in any of the parameters during the test. Syncopal patients have a different pattern of response to the orthostatic stimulus, in that they do not show the increase in sympathetic tone observed in normal individuals immediately after tilting. In the patients with a positive tilt test, there is a shift in the balance of ANS activity towards the sympathetic system shortly before the onset of syncope. (PACE 1997; 20[Pt. I]:1332-1341)     

Modulations of human autonomic function induced by positive pressure-assisted breathing

In order to examine the acute autonomic response in humans during and immediately after positive pressure-assisted (PPA) breathing, spontaneous cardiac baroreflex (BR) sensitivity was studied through the adaptation of consecutive RR intervals in response to spontaneous systolic blood pressure fluctuations in 11 healthy subjects. The gain (alpha-index) in baroreceptor reflex was estimated using cross-spectral analysis (RR interval variability and systolic blood pressure variability) for the low frequency (LF) and high frequency (HF) bands. All measurements were made under fixed breathing rate (12 breaths per minute), and realized consecutively at baseline level (20 min), after-short inspiratory pressure support plus positive end-expiratory airway pressure (IPS + PEEP) ventilation (15 min), again under normal conditions (20 min; recovery period) and, finally, during a standard upward orthostatic challenge test (15 min; orthostatic challenge). The spontaneous BR gain in the HF band increases slightly during ventilation (+26.1 +/- 11.7%, P<0.05) and decreases significantly during recovery without any significant alteration in mean heart rate, systolic or diastolic blood pressure. The spontaneous BR gain in the LF band decreases during IPS + PEEP ventilation (8.4 +/- 4.4 versus 12.7 +/- 6.2 ms mm(-1) Hg; P<0.05) and returns to basal level during recovery. Orthostatic challenge altered significantly the BR gain in both HF and LF bands with significant heart rate acceleration. In humans, while the parasympathetic control of heart rate and blood pressure is found moderately enhanced, the sympathetic BR drive appears significantly and transitory altered under short term IPS + PEEP ventilation with a degree of alteration comparable to those observed during orthostatic challenge.     

Influence of age on heart rate variability during therapeutic hypothermia in a rat model

Objectives

To evaluate the effect of age on heart rate variability (HRV) in a rat model of therapeutic hypothermia.

Methods

Thirty-six male Sprague–Dawley rats (18 were 2 months old and 18 were 18 months old) were randomized into one of three groups: normothermia (37 °C), mild hypothermia (34 °C), and moderate hypothermia (31 °C). An electrocardiogram (ECG) was recorded at baseline and continuously for 1 h once the target core body temperature was reached. Various heart rate variability measurements were calculated.

Results

Significant effects of age were observed in respect to the ratio of standard deviation of all normal to normal R-R [NN] intervals (SDNN)/standard deviation of the differences between adjacent NN intervals (SD of delta NN) (P = 0.037), low frequency (LF) power, normalized units (nu, %) (P < 0.001), and the ratio of LF and high frequency (HF) (P < 0.001). Significant effects of temperature were found in LF power and a significant body-temperature interaction was found in HF power. HF power was significantly lower in the young rats at mild and moderate hypothermic conditions. For the LF/HF, the ratio was significantly lower in the young animals compared to the older animals at normal body temperatures and during mild hypothermia. LF/HF increased significantly at both 34 °C and 31 °C in the young rats compared to the young rats at 37 °C. In contrast, LF/HF was significantly lower in the older group of rats at 34 °C and 31 °C compared to the older group of rats maintained under normothermic conditions.

Conclusions

This study noted that autonomic regulation determined via HRV, primarily the ratio of LF to HF, was different between different age groups. Additional studies on this topic are needed to achieve a more detailed understanding of therapeutic hypothermia.     

Heart rate variability during sleep and sleep apnoea in a population based study of 387 women

Increased sympathetic activity during sleep has been suggested as a link between obstructive sleep apnoea syndrome and cardiovascular disease. Heart rate variability (HRV) is a measure of autonomic effect on the heart. Different parameters have been associated with sympathetic and parasympathetic activity. We have studied HRV in different sleep stages and related the HRV‐pattern to sleep apnoea in a population‐based sample of 387 women. We investigated the HRV‐parameters standard deviation of all R‐R intervals (SDNN), root of the averaged square of successive differences (RMSSD), low frequency component (LF), high frequency component (HF), ratio of low frequency component to high frequency component LF/HF and VSAI [variation in sympathetic activity between rapid eye movement (REM) and slow wave sleep, defined as LF_REM?LF_SWS]. The HRV‐parameters were compared with the results of a full‐night polysomnography. Hourly incidence of obstructive episodes was used for classifying the subjects into four apnoea‐hypopnoea index (AHI)‐groups (<5, ≥5 and <15, 15–30 and >30 events). Individual sleep stages were analysed by pooling all recordings. Women with high AHI had higher heart rate and LF/HF ratio. In subjects with AHI >30, LF/HF ratio however dropped to same level as with AHI <5. Subjects with high AHI had low VSAI. Levels of SDNN, LF and LF/HF ratio during REM and light sleep were similar to wakefulness. In slow wave sleep the parameters decreased. In conclusion, moderately increased prevalence of obstructive apnoeas was associated with signs of higher sympathetic activity. High AHI was however associated with a HRV‐pattern suggestive of depressed sympathetic drive and lowered ability to increase it during REM.     

Evaluation of Autonomic Influences on QT Dispersion Using the Head-Up Tilt Test in Healthy Subjects

Our objective was to examine the autonomic influence on QT interval dispersion using the head-up tilt test in healthy subjects. RR and QT intervals, heart rate variability, and plasma norepinephrine concentration were measured in the supine position and tilting to 70 degrees for 20 minutes using a footboard support in 15 healthy male volunteers (mean age +/- SD: 28.0 +/- 4.5 years). The rate-corrected QT interval (QTc) was calculated using Bazett's formula, and QT and QTc dispersions were defined as the maximum minus minimum values for the QT and QTc, respectively, from the 12-lead ECG. Spectral analysis of the heart rate variability generated values for the low- and high-frequency powers (LF and HF) and their ratio (LF/HF). Compared with values obtained in the supine position, tilting significantly increased QT (P < 0.05) and QTc dispersion (P < 0.01), the LF/HF ratio (P < 0.0001), and plasma norepinephrine concentration (P < 0.0001), and significantly decreased HF (P < 0.0001). QTc dispersion was positively correlated with the LF/HF ratio and plasma norepinephrine concentration, and negatively correlated with HF. These results suggest that head-up tilt testing increases QT dispersion by increasing sympathetic tone and/or decreasing vagal tone in healthy subjects.     

Autonomic Modulation of Sinus and Atrioventricular Nodes in Premature Low-Birth-Weight Infants

Respiratory vagal activity is expressed by heart rate variability (HRV) at approximately 1 month of age in premature low-birth-weight infants (PLBWI). However, the autonomic inputs into the sinus node (SAN) and atrioventricular node (AVN) in PLBWI are unclear. We evaluated the variability in PP and PR intervals at day zero (day 0) and 1 month (1 month) after birth in 16 PLBWI (gestation 32.3 ± 1.3 weeks, birth weight 1.578 ± 257 g). The polygraph was recorded during sleep on day 0 and at 1 month. PP and PR intervals and the number of respiratory cycles were measured, and frequency analysis was performed by auto-correlation fast Fourier transforms. Power spectral density (PSD: ms²) was calculated for the low frequency domain (LF: 0.036∼0.146 Hz), high frequency domain (HF: 0.146∼0.390 Hz), total frequency (TF: 0.036∼2.000 Hz), and respiratory sinus arrhythmia (RSA: frequency bandwidth of 0.3 Hz with peak respiratory frequency as median), and the PSD ratio in the PP and PR intervals (LF/HF, RSA/TF) were compared. Compared with day 0, a decrease in the LF/HF ratio and an increase in the RSA/TF ratio in PP intervals were observed at 1 month, consistent with expression of respiratory vagal activity. For PR intervals, on the other hand, the LF/HF ratio increased, indicative of accentuated sympathetic activity. However, the respiratory vagal input was weak, and the RSA/TF ratio remained unchanged. These observations suggest that, in PLBWI at 1 month, AVN conduction was not predominatly influenced by respiratory-related vagal activity, but was controlled by autonomic regulation, independent of the SAN.     

Effect of autonomic stressors on rate control in pacemakers using ventricular impedance signal

The aim of this study is to evaluate the heart rate adaptation obtained by a pacemaker, based on a measure of ventricular impedance in patients undergoing autonomic challenges. The evaluation procedure was based on the analysis of the mean value (MV) and heart rate variability (HRV) of RR and systolic pressure intervals, according to a set of neurovegetative stressors (controlled respiration in supine position and during active standing; mental stress; handgrip, and noninvasive sinusoidal stimulation of carotid baroreceptors). Each test lasted 5 minutes. Fifteen chronotropic incompetent patients first implanted, were studied three months after implantation. ECG, respiration activity, and noninvasive blood pressure were monitored. HRV was evaluated by spectral analysis. Variability in the low frequency (LF) and high frequency (HF) bands was compared by computing percentage and absolute powers. We found that baseline HR was 72.2 +/- 5.5 beats/min, in mental stress was 76.8 +/- 7.8 beats/min, in handgrip was 79.2 +/- 6.3 beats/min, and in active standing was 80.9 +/- 8.6 beats/min (P < 0.01, Friedman's test). During active standing, LF component was significantly higher with respect to baseline (25.7% of total power in standing; 9.4% in baseline, P < 0.01) and it was synchronous to the LF component of the arterial pressure variability. Carotid activation/deactivation by neck suction induced synchronous changes in the paced rates. In conclusion, closed loop strategy based on ventricular contractility continuously controls heart rate by tracking the sympathetic modulation to the heart.     

慢性肺心病患者的心率变异性

目的：观察慢性肺心病患者心率变异性，了解其自主神经功能的变化。方法：对25例慢性肺心病，25例健康对照者（对照组）作前瞻性对照研究，记录24h动态心电图，作时域和频域分析，结果：与对照组比较，肺心病组相邻心搏的R－R间期之差＞50ms的心搏数占R－R间期数的百分(pNN50)，每5min正常R－R间期标准差的平均值（SDANN），频域指标的高频（HF）明显降低，低频与高频的比值（LF／HF），明显升高，差异均有非常显著意义（P均＜0．01），而频域指标的低频（LF）无明显变化（P＞0．05），经过治疗后，肺心病组处于缓解期，与治疗前比较，HF，PNN50，SDANN等指标明显增加，而LF／HF明显降低，差异均有非常显著意义（P均＜0．01），肺心病组病人治疗后HF，pNN50,SDANN等指标均低于对照组，而LF／HF明显高于对照组，差异均有非常显著意义（P均＜0．01），肺心病组治疗后LF与治疗前及对照组比较，差异不具显著意义（P＞0．05）。结论：肺心中层得不仅交感神经活动占优势，同时并存迷走神经功能受损，自主神经功能可能存在连续性障碍。     

Effects of one-lung ventilation on cardiac autonomic nervous activity as evaluated by power spectral analysis of heart rate variability

The purpose of this prospective study was to evaluate the effects ofone-lung ventilation on the activity of the cardiac autonomic nervous system.Ten adult patients who underwent thoracotomy were endotracheally intubatedwith a double-lumen tube under general anesthesia using isoflurane. Afterinduction of anesthesia, a continuous, 256-sec electrocardiogram (ECG) wasobtained during bilateral lung ventilation (control) followed by recordingsduring one-lung ventilation of each side. Using the R–R intervaltachograms obtained for the 256-sec ECGs, low frequency (LF: 0.04–0.15Hz) and high frequency (HF: 0.15–0.40 Hz) bands of the spectral densityof the heart rate variability and the HF/LF ratio were analyzed using the fastFourier transform algorithm. Log(HF), which indicates parasympatheticactivity, increased during one-lung ventilation on each side, but did notdiffer between ventilated sides. Log(LF), which represents sympathetic andparasympathetic activity, increased similarly to log(HF) on both sides.Log(HF/LF), the balance of the sympathetic and parasympathetic activity, didnot change during one-lung ventilation. We suggest that one-lung ventilationalone does not substantially affect the cardiac autonomic nervous system.     

Moderate exercise induces different autonomic modulations of sinus and AV node

BACKGROUND: The routine determination of heart rate variability (HRV) from surface ECGs is based on RR intervals because of the difficulty to precisely locate the P-wave fiducial point on surface ECG recordings. The aim of the study was to assess the changes of RR, PP, and PR intervals at rest and during moderate exercise. The time intervals were determined from atrial and ventricular pacemaker-mediated intracardiac electrograms. METHODS: Ten patients in sinus rhythm with intrinsic AV node conduction who had received the dual-chamber pacemaker Logos (Biotronik) were included. High-resolution atrial and ventricular intracardiac electrograms were transmitted at rest in supine position and during walking to a portable external recorder. Recording sequences of 150 successive heart cycles were used for HRV analyses after computer-assisted triggering of P and R events. The HRV-index SDNN and power spectral densities for the low (LF; 0.04-0.15 Hz) as well as high (HF; 0.15-0.40 Hz) frequency bands were determined. RESULTS: SDNN decreased from 26.0 +/- 8.1 ms at rest to 18.3 +/- 4.2 ms during exercise for the PP intervals (P < 0.05) and from 26.8 +/- 8.1 to 18.4 +/- 4.1 ms for the RR intervals (P < 0.05). The LF/HF ratio increased from 2.02 +/- 1.3 to 4.5 +/- 1.5 in the atrium (P < 0.05) and from 2.0 +/- 1.2 to 5.2 +/- 1.9 in the ventricle P < 0.05). Comparing atrial and ventricular HRV at both activity levels, no significant differences were observed for the power of LF and HF spectral components. Regarding the PR intervals SDNN, the total power and the LF/HF ratio did not significantly change during exercise. CONCLUSIONS: The described technique enabled to record intracardiac electrograms not only at rest, but also during moderate exercise and to use them for HRV evaluation. The changes of PP and RR, but not of the PR intervals, during exercise indicate that autonomic inputs to the sinus node and AV node are independent from each other. The ventricular HRV seems to derive mainly from variations of the sinus node pulse formation.     

迷走神经张力增高为主的植物神经功能失调

目的采用心率变异（ＨＲＶ）分析辅助诊断迷走神经张力增高为主的植物神经功能失调患者。方法排除器质性疾患的４０例患者，均有头晕、胸闷、气短，ＨＲＶ分析包括时域和频域分析。结果与正常人相比，患者的ＳＤＮＮ、ＨＲＶＩＮＤＥＸ、ＲＭＳＳＤ、ＰＮＮ５０、ＴＰ、ＬＦ、ＨＦ均高于正常人，而ＨＲ、ＬＦ／ＨＦ低于正常人，统计分析有显著差异（Ｐ＜０．０１）。结论４０例患者平均心率减慢，迷走神经水平增高，交感迷走神经张力之比减低，交感迷走神经平衡发生了改变。     

Heart Rate Variability in Patients with Familial Amyloid Polyneuropathy

The purpose of this study was to evaluate heart rate variability (HRV) in patients with familial amyloid polyneuropathy (FAP) using the time- and frequency-domain analysis. The study population consisted of 19 patients with FAP, and 19 age and sex matched normal volunteers. The 24-hour Holter recordings of all subjects in sinus rhythm and off medication were analyzed. Five time-domain indices of HRV were computed. The frequency component of HRV was calculated by fast Fourier transform analysis of the RR intervals. The power spectrum of the low frequency (LF) between 0.04–0.15 Hz and high frequency (HF) between 0.15–0.40 Hz and the LF/HF ratio was calculated. Global measures of HRV including the standard deviation of the mean of RR intervals (SDNN) and the standard deviation of 5-minute mean RR intervals (SDANN) were decreased in patients with FAP. Specific vagal influences on HRV including the proportion of RR intervals more than 50 milliseconds different (pNN50) and the HF power on spectral analysis were less in patients with FAP. LF power and LF/HF ratio were more decreased in patients with FAP at the advanced stage than at the early stage. In conclusion, HRV was significantly decreased in patients with FAP at the early stage, and sympathetic activity was more decreased in patients at the advanced stage. These findings suggest that the decrease of the HRV is an indicator of this disease and the power spectral analysis of the HRV is beneficial in assessing the severity of the autonomic dysfunction.