Heart rate variability and heart rate in healthy volunteers. Is the female autonomic nervous system cardioprotective?

Aims Heart rate variability has been proposed as an indicator ofcardiovascular health. Since women have a lower cardiovascularrisk, we hypothesized that there are gender differences in autonomicmodulation. Methods and Results In 276 healthy subjects (135 women, 141 men) between 18 and71 years of age, 24h heart rate and heart rate variability weredetermined. All heart rate variability parameters, except forpNN50 and high frequency power, were higher in men. After adjustmentfor heart rate, we obtained gender differences for: the standarddeviation (P=0·049), the standard deviation of the 5minaverage (P=0·047), low frequency power (absolute values,P=0·002;normalized units,P<0·001) and ratio low frequency/highfrequency (P<0·001). There were no significant genderdifferences in heart rate variability parameters denoting vagalmodulation. Gender differences were confined to age categoriesof less than 40 years of age. The majority of heart rate variabilityparameters decreased with age. Only in men, was a higher bodymass index associated with a higher heart rate and with lowerheart rate variability parameters (P<0·001). Conclusion Cardiac autonomic modulation as determined by heart rate variability,is significantly lower in healthy women compared to healthymen. We hypothesize that this apparently paradoxical findingmay be explained by lower sympathetic activity (low frequencypower) in women. This may provide protection against arrhythmiasand against the development of coronary heart disease.     

Circadian rhythm of spectral indices of heart rate variability in healthy subjects

Circadian pattern of heart rate variability spectral indices, including hourly, 24-hour, night, day, morning, and sex-adjusted measures of low frequency (LF), high frequency (HF), and LF/HF, was evaluated in healthy persons in 24-hour 3-lead electrocardiogram. HF showed circadian pattern with the greatest night values and LF/HF with the smallest night values. Peaks of hourly LF were found between 5 and 9 am and between 4 and 6 pm. The smallest LF was between 11 pm and 3 am. Hourly HF peaked between 11 pm and 5 am. The smallest HF was observed between midday and 2 pm. LF/HF peaked between 6 and 9 am as well as between 4 and 6 pm with the smallest values between midnight and 5 am. Sex adjustment was of no significance. In healthy subjects, HF and LF/HF have circadian pattern. Evaluation of all 5-minute intervals of 24-hour period seems to be a precise method of heart rate variability analysis.     

Effects of gender and aging on differential autonomic responses to orthostatic maneuvers

Background: There are gender differences in heart rate and blood pressure response to postural change. Also, normal aging is often associated with diminished cardiac autonomic modulation during postural change from supine to upright position. Nevertheless, the exact mechanisms of these physiological alterations are not entirely understood. Methods: A total of 362 volunteers (206 females, age range: 10–88 years) underwent continuous, noninvasive, beat‐to‐beat blood pressure and ECG recordings in supine and upright position. To calculate spontaneous baroreflex sensitivity (BRS), blood pressure and RR interval fluctuations were reconstructed using the time‐domain sequential technique. Furthermore, mean systolic and diastolic blood pressure, mean heart rate, and frequency‐domain parameters of heart rate variability (low‐frequency power [LF], low‐frequency power in normalized units [LFn] high‐frequency power [HF], high‐frequency power in normalized units [HFn], low‐/high‐frequency ratio [LF/HF], and total power [TP]) were analyzed in both supine and standing positions. To investigate age‐related differences, subjects were divided into four equally sized groups (quartile l: 10–33 years; ll: 34–42 years; III: 43–57 years; and lV: 58–88 years), as well as decades (l: 10–19 years; ll: 20–29 years; lll: 30–39 years; lV: 40–49 years; V: 50–59 years; Vl: 60–69 years; Vll: ≥ 70 years). Results: A continuous decline in BRS, LF, HF, and TP was observed with increasing age in both male and female subjects, regardless of posture. Gender comparison showed significantly higher values of LF (supine P < 0.001; upright P < 0.05), LFn (supine P < 0.001; upright P < 0.01), and TP (supine P < 0.05; upright P < 0.05) in men than women in supine and standing positions. HF revealed no gender difference and HFn (supine P < 0.001; upright P < 0.05) was larger in women. Log BRS correlated well with log LF and log HF in both supine and standing positions. Conclusions: There are significant differences in postural cardiac autonomic modulation between men and women, and the degree of autonomic response to orthostatic maneuvers varies with normal aging. These results may explain gender‐ and age‐related differences in orthostatic tolerance.     

正常人心率减速力与心率变异性的关系

目的 观察健康人心率减速力(DC)和心率加速力(AC)的昼夜变化规律及其与心率变异性(HRV)之间的关系.方法 80例健康人接受24h动态心电图检查,按其时间段不同而划分为昼间(15:00～20:00)和夜间(00:00～05:00)两个时间段.计算机自动测定其昼夜24h的DC、AC值及心率变异性时域指标(SDNN,R...     

Distinctive impaired cardiac autonomic modulation of heart rate variability in chronic Chagas' indeterminate and heart diseases

Introduction

Cardiac autonomic dysfunction occurs in Chagas' indeterminate and heart disease, but comparison of this disturbance between both forms was not yet performed.

Methods

Time- and frequency-domain 5-minute heart rate variability in supine and standing positions were evaluated in 17 subjects with Chagas' disease with the indeterminate form, 13 with heart disease and 15 controls. Trend of variability indices across the groups was also tested.

Results

In the supine position, reduced time-domain and absolute frequency-domain indices reflecting overall autonomic modulation were observed in both Chagas' disease groups. In the standing position, the coefficient of variation and those frequency-domain indices were also reduced, and the other time-domain indices were reduced only in the cardiac group. Heart rate variability indices hypothesized to reflect relative sympathetic and parasympathetic activity showed no alteration. A significant graded reduction was observed in the altered indices in both postures, from the control to the Chagas' indeterminate and heart disease groups.

Conclusion

Cardiac autonomic dysfunction, with preserved putative measures of sympathetic and parasympathetic modulation in relative terms, was less severe or absent in the indeterminate and pronounced in cardiac form of Chagas' disease.     

高血压合并睡眠呼吸暂停综合征患者血压节律及心率变异

目的研究阻塞性睡眠呼吸暂停（OSAS）对高血压病患者血压昼夜节律及心率变异（HRV）的影响。方法选取2007年4月至2010年4月中国人民解放军总参谋部警卫局保健处和北京军区总医院心血管内科住院的91例患者,根据患者是否患有高血压病及OSAS分为对照组、单纯高血压组和高血压病合并OSAS组。比较3组之间非勺型昼夜血压曲线的比例、HRV时域指标与频域指标、夜间平均血氧水平以及呼吸紊乱指数（AHI）的差异。结果高血压病合并OSAS组患者呈非勺型昼夜血压曲线的比例以及HRV时域指标值与频域指标值较其他两组明显增加（P〈0．01）,并且夜间平均血氧水平显著低于其他两组,而AHI则明显高于其他两组（P〈0．01）。结论OSAS导致高血压病患者血压昼夜节律呈非勺型、HRV增强、夜间平均血氧水平下降、AHI明显增加,是高血压病患者心血管事件增加的重要危险因素。     

心率和心率变异性用于评定颈部手法刺激对自主神经系统的影响

目的应用心率和心率变异性分析,评定颈部手法刺激对自主神经系统的影响。方法选择正常青年男性志愿者,对受试者进行颈部手法刺激,刺激前和刺激后各记录5min动态心电图,以心率和心率变异性作为观测指标,判断颈部手法刺激对自主神经系统的影响。结果对30名正常青年男性志愿者观察发现,颈部手法刺激后,心率显著降低(RR间期延长);时域分析中SDNN有显著性增加,频域分析中VLF和总功力谱有显著性增加。结论心率和心率变异性是一项评定颈部手法刺激对自主神经系统效应的有用指标。     

不同年龄和性别短程心率变异性对比分析

目的观察年龄和性别对短程心率变异性的影响。方法对接受RR间期标准差（SDNN）及变异系数（CU）两项短程心率变异性（HnV）指标检查的467名正常人按年龄分为老年人（t〉60岁）组、中年人（40-59岁）组和青年人（≤39岁）组，进行组间心率变异性指标的对比；按性别分为两组，进行心率变异性指标的比较；按性别与年龄段进行分组，观察相同性别，不同年龄段及相同年龄段不同性别对心率变异性的影响。结果在老年、中年及青年三组之间进行组间对比，SDNN及CV两项指标均有显著差异，年龄与心率变异性呈负相关；不同性别问SDNN与CV两项指标均无显著差异，但在不同年龄段，性别对心率变异性有不同影响。结论正常人短程心率变异性与年龄呈负相关；在不同年龄段，性别对心率变异性产生不同影响，在小于30岁的人群中男性高于女性，在30-39岁的人群中，女性显著高于男性，表明心率变异性的生理变化不仅与年龄或性别单一因素有关，也与年龄和性别的综合因素有关。     

充血性心力衰竭病人昼夜心脏自主神经功能与平均心率的研究

目的:了解充血性心力衰竭病人心脏自主神经活性和平均心率的昼夜改变.方法:对59例充血性心力衰竭病人(心力衰竭组)和40例健康者(对照组)经Holter记录进行24 h长程心功率谱分析和平均心率计算.结果:心力衰竭组清醒期或睡眠期LFnu均明显升高而HFnu明显降低(P＜0.01或P＜0.05),LF/HF均大于对照组(P＜0.05),同时心力衰竭组夜间平均心率明显高于对照组(P＜0.01).结论:心力衰竭病人昼夜交感神经活性均升高,同时伴迷走神经活性减退,这种改变与心力衰竭病人夜间平均心率明显高于对照组可能有内在联系.     

Circadian changes in heart rate turbulence parameters

Heart rate turbulence is a novel method to identify patients at risk of cardiac death, and to date, there are no data concerning its circadian changes. In 46 coronary patients (mean age 63 +/- 8 years) with at least 100 ventricular premature beats in 24-hour Holter monitoring, turbulence onset, turbulence slope, and heart rate variability parameters were calculated in 3 equal 4-hour periods during morning, afternoon, and night. No circadian changes in turbulence onset values were found, while TS displayed significantly lower values during afternoon than during morning or night hours (5.08, vs. 7.08 and 7.99 ms/RR, respectively). Some heart rate variability parameters also showed lower values in the afternoon, not in the morning hours. In conclusion, in hospitalized patients with stable coronary artery disease, turbulence slope shows circadian pattern with lowest values observed in the afternoon when compared to morning and night hours.     

Short and long term effects of exercise training on the tonic autonomic modulation of heart rate variability after myocardial infarction

We studied the effects of cardiac rehabilitation on the sympathovagalcontrol of heart rate variability in 30 patients after a first,uncomplicated myocardial infarction. Twenty-two patients completed8 weeks of endurance training (trained), while eight decidednot to engage in the rehabilitation programme for logisticalreasons, and were taken as untrained controls. Age, site ofinfarction, ejection fraction, ventricular diameter and stresstest duration were similar in the two groups at baseline. Heartrate variability was evaluated 4 weeks after infarction beforestarting rehabilitation, and repeated 8 weeks and one year laterin both trained and untrained patients. Measures of heart ratevariability, obtained from both time- and frequency- domainanalysis of a 15 min ECG recording in resting conditions, wereas follows: mean RR interval and its standard deviation (RRSD),the mean square successive differences (MSSD), the percent ofRR intervals differing >50 ms from the preceding RR (pNTN50),the low and high frequency components of the autoregressivepower spectrum of the RR intervals and their ratio (LF/HF).At baseline, heart rate variability was similar in trained anduntrained patients. In the short term (8 weeks after infarction),training increased RRSD by 25% (P<0·01), MSSD by 69%(P<0·01), pNN50 by 120% (P<0·01), and reducedLF/HF ratio by 30% (P<0·01). The effects persistedafter one year in trained patients. In untrained patients, theautonomic control of heart rate variability did not change 8weeks after myocardial infarction and was only slightly modifiedby time. Thus, exercise training, performed for 8 weeks aftera myocardial infarction, modifies the sympathovagal controlof heart rate variability toward a persistent increase in parasympathetictone, known to be associated with a better prognosis. This maypartly account for the favourable outcome of patients who undergorehabilitation.     

索他洛尔对正常人和心律失常病人心率变异性的影响

分析１０例健康志愿者和２０例室性早搏病人应用索他洛尔前后的心率变异性，旨在了解索他洛尔对ＨＲＶ的影响。结果；索他洛尔增加健康志愿者和室早病人反映迷走神经活性的ＨＲＶ时域指标，且心率变异性的改变与室早抑制无相关关系，用荭前后ＨＲＶ时域指标间相关关系无明显改变。     

Circadian rhythmic fractal scaling of heart rate variability in health and coronary artery disease

Background: In clinical cardiology, heart rate variability is a putative index of autonomic cardiovascular function. Signs of reduced vagal activity are not only associated with an enhanced risk of sudden cardiac death, but such impaired heart rate variability became a new predictor of sudden cardiac death and other mortality in patients with a variety of diseased states. Hypothesis: It is postulated (1) that the time structure (chronome) of heart rate variability in clinical health includes a circadian rhythm and deterministic chaos, the latter gauged by the correlation dimension of RR intervals; and (2) that this chronome is altered in patients with coronary artery disease (CAD). Methods: From 24-h Holter records of 11 healthy controls and 10 patients with CAD, 500-s sections around 02:00, 06:00, 10:00, 14:00, 18:00 and 22:00 hours were analyzed for smoothed RR intervals sampled at 4 Hz. Correlation integrals were estimated for embedding dimensions from 1 to 20 with a 1.0-s time lag, using an algorithm modified from Grassberger and Procaccia. The Wilcoxon signed-rank test compares circadian end points assessed by cosinor between the CAD patients and age-matched controls. Results: A circadian rhythm characterizes the correlation dimension of healthy subjects peaking during the night (p «0.005). Patients with CAD have a lowered correlation dimension (p « 0.05) and an altered circadian variation which requires the consideration of an approximately 12-h (circasemidian) component. Conclusion: The results demonstrate the sensitivity of circadian rhythms for the detection of disease. A partial 24- to 12-h (circadian-to-circasemidian) frequency multiplication (or partial variance transposition) in CAD of the correlation dimension, apart from being a potential clue to the etiology of the disease, adds a new feature to a chronocardiology combining, with the fractal scaling, an assessment of circadian and circasemidian components as measures of predictable variability to be tested for use in diagnosis, prognosis, and as putative guides to treatment timing.     

Evaluation of autonomic nervous function during upper gastrointestinal endoscopy using heart rate variability

To investigate autonomic nervous function during upper gastrointestinal endoscopy, we analyzed R-R interval variability from electrocardiograms obtained during endoscopy. Holter electrocardiogram recordings were made before and after premedication, and during endoscopy. Time- and frequency-domain analyses of heart rate variability were performed in 54 subjects premedicated with scopolamine butylbromide (SB group) and in 66 subjects premedicated with glucagon (G group). To determine the effect of autonomic imbalance on arrhythmia generation during endoscopy, subjects with arrhythmias (A group) were compared with subjects without arrhythmias (N group). In the SB group, high frequency spectral power (HF power; 0.15 to 0.40 Hz), which reflects parasympathetic activity, decreased significantly after premedication, and decreased further during endoscopy (P < 0.01). Moreover, HF power before premedication or during endoscopy in the A group was significantly lower than that in the N group (P < 0.01). This study suggests that the measurement of HF power prior to endoscopy can identify subjects with reduced HF power. This should allow the prevention of cardiovascular complications related to premedication and endoscope insertion. Received: June 25, 1999 / Accepted: June 23, 2000     

高血压患者心率变异性的性别差异及年龄影响

目的探讨性别和年龄对高血压患者心率变异性(HRV)的影响。方法采用24h动态心电图(Holter)评价300例高血压患者HRV的时域和频域指标,并将患者分为男性组(163例)和女性组(137例),再根据年龄分为≤65岁组(130例)和>65岁组(170例),分别比较不同性别和不同年龄组间HRV的差别,并对性别和年龄与HRV各指标间的相关性进行了分析。结果男性组极低频功率(VLF)、低频功率/高频功率(LF/HF)明显大于女性组(分别P=0.017和P=0.0002),标化HF(HFnorm)则明显低于女性组(P<0.0001),但是这种性别的差异仅发生在≤65岁组中。单变量回归分析显示男性与VLF、LF/HF相关较密切(分别r=-0.132,P=0.02和r=-0.176,P=0.002),女性与HFnorm相关较密切(r=0.215,P<0.0001),这种相关性也只出现在≤65岁组中,多变量回归分析只HFnorm与性别独立相关(r=0.215,P<0.0001)。≤65岁组总功率(TP)(P=0.011)、VLF(P=0.001)、低频功率(LF)(P=0.005)、标化低频功率(LFnorm)(P=0.0001)和LF/HF(P=0.001)明显大于>65岁组,而rMSSD(P=0.002)、PNN50(P=0.007)、HFnorm(P=0.031)则明显低于>65岁组,单变量回归分析除PNN50外,年龄与HRV各指标均具有显著的相关性,多变量回归分析年龄与LFnrom、LF、rMSSD独立相关(r=0.432,P<0.0001)。结论以上结果提示中年期女性高血压患者自主神经调节紊乱可能比男性更明显;老年高血压患者自主神经调节损害比中年患者更显著。