基于复杂度的心率变异性分析研究进展

心率变异性（HRV）是当前心电图分析的一个前沿热点,它反映了交感神经和副交感神经对心血管系统的综合调节作用,是评价心血管系统功能的重要指标。随着非线性动力学和复杂性科学的发展,HRV信号被普遍认为是混沌或含有混沌成分的信号。复杂度是用来表征一个心率非线性动力学系统复杂程度的量度,以其简单快速的优点引起了众多研究者的兴趣,并广泛应用于心率变异性分析。本文综述了国内外复杂度算法的研究进展及基于复杂度的心率变异性分析的临床应用及前景。     

Analysis of Heart Rate Variability in Masked Hypertension

To investigate heart rate variability (HRV) in patients with masked hypertension (MH), participants were classified based on clinic and 24-h ambulatory blood-pressure monitoring: essential hypertension (EH, n = 40; MH, n = 36) and normotension (NT, n = 48). The HRV parameters were observed using a 24-h Holter monitor. Compared with NT controls, the parameters of HRV (SDNN, SDANN, SDNN Index, RMSSD, HF) and parameters in EH and MH patients had significantly decreased. No statistically significant difference in the HRV parameters was found between the EH and MH groups. The changes in HRV parameters show cardiac autonomic nerve dysfunction in patients with MH.     

Analysis of Heart Rate Variability in Space Medicine

Space medicine was one of the first fields of science and practice to use the analysis of the heart rate variability (HRV) for obtaining new scientific information and solving the tasks of exercising medical control over humans working under extreme conditions. The theoretical basis of HRV analysis and different approaches to the assessment of the data obtained are presented in the work. The technique for HRV analysis with regard to the specifics of space studies is described. The results of investigations at different stages of the space flight, including the use of Holter monitoring, are presented. Special attention is given to the results of the investigations in a long-term 14-month space flight. The adaptation to long-term weightlessness was shown to be of a multistep character with the gradual involvement of additional regulatory mechanisms.     

Assessment of Heart Autonomic Control on the Basis of Spectral Analysis of Heart Rate Variability

An orthostatic test with frequency-controlled breathing (with a respiration period of 10 s) or spontaneous breathing was used to analyze frequency estimates of the heart rate variability (HRV) in the low-frequency (LF) and high-frequency (HF) ranges in young men and women. It was demonstrated that the spectral components of HRV bear no signs of sex differentiation, suggesting a uniform structural organization of the system of autonomic nervous control of the heart (SANCH) in humans. The LF component of the HRV spectrum is a marker of the functional state of the SANCH; it should be studied under conditions of controlled breathing at a frequency of 0.1 Hz. The HF and LF components of the HRV characterize the state of the SANCH at a given moment and do not reflect directly its adaptation reserve. The HF component of the HRV is interesting as a parameter that may be used for estimating the changes in the adaptation reserve of heart autonomic control. It is preferable to analyze this component in the absence of external disturbances in the LF range of the spectrum.     

不稳定型心绞痛心率变异性特点及美托洛尔对其的影响

目的:了解心率变异性(heart rate variability,HRV)在不稳定型心绞痛(unstable angina pectoris,UAP)发病中的作用及其用于病情严重程度判断的价值;了解美托洛尔对UAP患者HRV的影响。方法:选择年龄、性别相匹配的UAP患者、SAP患者和健康人各60例做动态心电图检查,经Holter软件分析进行HRV时域指标的比较。UAP组动态心电图检查后加用美托洛尔25-50 mg/d(分两次口服),20天后重复动态心电图检查。结果:1UAP组与正常组比较各项指标均降低(P0.01)。2正常人HRV具有昼夜节律变化的特点,UAP组HRV昼夜节律变化性降低。3UAP病人服用美托洛尔后,心肌缺血、心律失常得到改善。结论:1.UAP患者心脏自主神经活性主要是副交感神经活性受损,交感神经活性相对占优势。2.无合并症的UAP病人HRV呈昼夜节律性降低。3.美托洛尔可改善UAP患者HRV。     

基于互信息和自相关函数的睡眠期间心率变异性研究

目的：研究互信息和自相关函数在睡眠各阶段心率变异性（heart rate variability,HRV）分析中的应用。方法：采用网络公开数据库SleepHeart Rateand Stroke VolumeDataBarhk,将RR序列分为30S一段,并以每30S数据为中心截取5minRR序列作为待分析对象。提取5minRR序列的互信息特征BDM、PDM和自相关函数特征BDC、PDC,然后用统计方法分析各特征在觉醒瓜EM／浅睡／深睡四种睡眠状态下的差异。结果：浅睡和深睡期间,BDM、PDM显著高于觉醒和REM睡眠（P〈0．001）。而BDC显著低于觉醒和REM睡眠（P〈0．001）,PDC无显著差异（P〉0．05）。结论：①BDM、PDM和BDC从不同角度反映了不同睡眠阶段下RR序列的特征,它们或许与HRV不同的调节机制有关。@BDM、PDM和BDC可作为辅助HRV睡眠分期的新指标。     

Effect of Lower Body Negative Pressure on the Heart Rate Variability

The R-R intervals were measured in 25 female volunteers aged 21–34 years after exposure to lower body negative pressure (LBNP). A number of advantages of information entropy (h) as an index of cardiovascular performance were revealed. With h used as a controlled variable, it was possible to ensure individual targeted changes in the functional state (FS) during LBNP. It was found that an individual exposure to LBNP caused regular changes in h and FS. Equations for targeted changes in human FS were derived.__________Translated from Fiziologiya Cheloveka, Vol. 31, No. 4, 2005, pp. 61–64.Original Russian Text Copyright © 2005 by Gerasimov, Ignatov.     

Nonstationary Heart Rate Variability in Respiratory Tests

A new method was proposed for processing a nonstationary heart rate by using frequency-modulated signals rather than amplitude-modulated signals equally spaced over several points of time as in the conventional method. A frequency-modulated signal is a set of identical Gaussian peaks that coincide with the true time points of heart beats. A continuous wavelet transform was used to quantitatively describe the heart rhythm signal. A test with controlled breathing was performed as an example and included three consecutive stages: rest, rhythmic breathing at a specified frequency, and exhalation. Tachograms recorded during the breath test was found to be a nonstationary signal with the alternation of peaks of different spectral ranges. A system of quantitative parameters was developed to describe the dynamics of changes in the spectral properties of the tachogram in transitional areas. A static clustering by the effect of the respiratory test and a dynamic clustering in order to identify the time points when the autonomic nervous system is stressed were performed for all subjects. The article discusses the prospects of using the method as a means to analyze the transient effects in various functional tests and as biofeedback that would help to change the heart rhythm.     

Comparative Evaluation of Heart Rate Variability Based on the Data of ECG and Blood Pressure Measurements

The development of new approaches to the assessment of heart rate variability (HRV) is an important problem, since HRV reflects the functioning of cardiovascular control and is affected by various diseases. The purpose of this study was to evaluate the informative value of statistical and spectral HRV parameters calculated from pulse interval (PI) data of blood pressure as compared with those calculated from RR-interval data of electrocardiograms (ECG). We recorded ECG in conscious rats using skin adhesive electrodes simultaneously with blood pressure signal obtained through a catheter in the femoral artery. It has been found that the PI sequence can be used to calculate the statistical HRV indices that describe the HRV at time intervals about 1 min or longer, but statistical indices of the PI and RR intervals may differ in the analysis of beat-tobeat variations. The power spectra of the RR intervals and PI coincide in the low-frequency region, including the band of baroreflex cardiac rhythm oscillation. However, they can differ in the high-frequency region (at respiration frequency and above).     

冠心病合并脑梗死患者心率变异性及心律失常的变化分析

目的：研究冠心病合并脑梗死患者的心率变异性情况,和心律失常的发生率,分析它们的变化规律,为患者疾病的治疗及预后提供更好的治疗指导。方法：研究对象为2012年2月~2012年12月我院心内科及神经内科的患者,其中Ⅰ组：冠心病合并脑梗死患者40例、Ⅱ组：单纯冠心病患者40例、Ⅲ组：单纯脑梗死患者40例、以及Ⅳ组：健康成人50例,统计全部患24 h心率变异性及心律失常发生情况,并进行对比分析。结果：Ⅰ组患者的心率变异性和心律失常发生明显高于其它组患者,差异均具有统计学意义（P〈0.05）。且心率变异性时域参数下降,心律失常发生率升高。结论：冠心病合并脑梗死患者的心率变异性和心律失常发生率增高,为避免冠心病合并脑梗死的患者突然心律失常及猝死,应积极改变治疗措施。     

Automatic Prediction of Cardiovascular and Cerebrovascular Events Using Heart Rate Variability Analysis

Background

There is consensus that Heart Rate Variability is associated with the risk of vascular events. However, Heart Rate Variability predictive value for vascular events is not completely clear. The aim of this study is to develop novel predictive models based on data-mining algorithms to provide an automatic risk stratification tool for hypertensive patients.

Methods

A database of 139 Holter recordings with clinical data of hypertensive patients followed up for at least 12 months were collected ad hoc. Subjects who experienced a vascular event (i.e., myocardial infarction, stroke, syncopal event) were considered as high-risk subjects. Several data-mining algorithms (such as support vector machine, tree-based classifier, artificial neural network) were used to develop automatic classifiers and their accuracy was tested by assessing the receiver-operator characteristics curve. Moreover, we tested the echographic parameters, which have been showed as powerful predictors of future vascular events.

Results

The best predictive model was based on random forest and enabled to identify high-risk hypertensive patients with sensitivity and specificity rates of 71.4% and 87.8%, respectively. The Heart Rate Variability based classifier showed higher predictive values than the conventional echographic parameters, which are considered as significant cardiovascular risk factors.

Conclusions

Combination of Heart Rate Variability measures, analyzed with data-mining algorithm, could be a reliable tool for identifying hypertensive patients at high risk to develop future vascular events.     

Continuous Multi-Parameter Heart Rate Variability Analysis Heralds Onset of Sepsis in Adults

Background

Early diagnosis of sepsis enables timely resuscitation and antibiotics and prevents subsequent morbidity and mortality. Clinical approaches relying on point-in-time analysis of vital signs or lab values are often insensitive, non-specific and late diagnostic markers of sepsis. Exploring otherwise hidden information within intervals-in-time, heart rate variability (HRV) has been documented to be both altered in the presence of sepsis, and correlated with its severity. We hypothesized that by continuously tracking individual patient HRV over time in patients as they develop sepsis, we would demonstrate reduced HRV in association with the onset of sepsis.

Methodology/Principal Findings

We monitored heart rate continuously in adult bone marrow transplant (BMT) patients (n = 21) beginning a day before their BMT and continuing until recovery or withdrawal (12±4 days). We characterized HRV continuously over time with a panel of time, frequency, complexity, and scale-invariant domain techniques. We defined baseline HRV as mean variability for the first 24 h of monitoring and studied individual and population average percentage change (from baseline) over time in diverse HRV metrics, in comparison with the time of clinical diagnosis and treatment of sepsis (defined as systemic inflammatory response syndrome along with clinically suspected infection requiring treatment). Of the 21 patients enrolled, 4 patients withdrew, leaving 17 patients who completed the study. Fourteen patients developed sepsis requiring antibiotic therapy, whereas 3 did not. On average, for 12 out of 14 infected patients, a significant (25%) reduction prior to the clinical diagnosis and treatment of sepsis was observed in standard deviation, root mean square successive difference, sample and multiscale entropy, fast Fourier transform, detrended fluctuation analysis, and wavelet variability metrics. For infected patients (n = 14), wavelet HRV demonstrated a 25% drop from baseline 35 h prior to sepsis on average. For 3 out of 3 non-infected patients, all measures, except root mean square successive difference and entropy, showed no significant reduction. Significant correlation was present amongst these HRV metrics for the entire population.

Conclusions/Significance

Continuous HRV monitoring is feasible in ambulatory patients, demonstrates significant HRV alteration in individual patients in association with, and prior to clinical diagnosis and treatment of sepsis, and merits further investigation as a means of providing early warning of sepsis.     

Nonstationary Heart Rate Variability during the Head-Down Tilt Test

Biophysics - Abstract—A new method has been proposed for processing the nonstationary rhythmogram signal recorded in the head-down tilt test (HDT). The method is based on the continuous...     

Heart Rate Variability as a Marker of Self-Regulation

Self-regulation is central to many of the most important individual and societal problems today. We sought to determine whether the relationship between self-regulation and heart rate variability (HRV) could be replicated and extended. We hypothesized that baseline HRV would predict persistence on an anagram task, and that under conditions requiring greater self-control, HRV would increase. Two groups were given the same set of difficult and unsolvable anagrams. To induce self-regulatory fatigue, the suppression group was asked to try to not think of a white bear while the expression group was asked to try to think of a white bear. Baseline HRV predicted persistence on the unsolvable anagram. Both groups demonstrated changes in HRV relative to baseline, although we were unable to replicate findings that HRV was elevated during high self-regulatory effort. We were, however, able to replicate findings that the expression group persisted longer on the anagram task compared to the suppression group but only when accounting for physical activity scores. The present study advances our knowledge of the relationship between HRV and self-regulation, so that we can more successfully treat those with seriously impaired self-control.     

Heart Rate Variability and Autonomic Modulations in Preeclampsia

BackgroundAlthough the exact pathophysiology of preeclampsia is not well understood, autonomic nervous system imbalance is suggested as one of the main factors.AimsTo investigate heart rate variability (HRV) and autonomic modulations in Sudanese pregnant women with preeclampsia.ResultsPatients with preeclampsia achieved significantly higher LF Norm [49.80 (16.25) vs. 44.55 (19.15), P = 0.044] and LnLF/HF [0.04 (0.68) vs. -0.28 (0.91), P = 0.023] readings, but lower HF Norm [49.08 (15.29) vs. 55.87 (19.56), P = 0.012], compared with healthy pregnant women. Although all other HRV measurements were higher in the patients with preeclampsia compared with the controls, only LnVLF [4.50 (1.19) vs. 4.01 (1.06), P = 0.017] and LnLF [4.01 (1.58) vs. 3.49 (1.23), P = 0.040] reached statistical significance.ConclusionThe study adds further evidence for the dominant cardiac sympathetic modulations on patients with preeclampsia, probably secondary to parasympathetic withdrawal in this group. However, the higher LnVLF and LnLF readings achieved by preeclamptic women compared with the controls are unexpected in the view that augmented sympathetic modulations usually depresses all HRV parameters including these two measures.     

Heart Rate Variability during Performance of Various Resultive Tasks

Heart rate variability was studied in 30 subjects before and after the assembling of a single-type color mosaic. The heart rate analysis was performed by evaluating its statistical structure (variation curves, scatter plots, and standard deviation). The wave structure of a series of cardiointervals was assessed by calculating and plotting the autocorrelation function. Certain heart rate parameters in different subjects reflected to various extents their success in achieving the useful end result of the visuomotor design task.     

Heart Rate Variability and Blood Pressure during Dynamic and Static Exercise at Similar Heart Rate Levels

Aim was to elucidate autonomic responses to dynamic and static (isometric) exercise of the lower limbs eliciting the same moderate heart rate (HR) response. Method: 23 males performed two kinds of voluntary exercise in a supine position at similar heart rates: static exercise (SE) of the lower limbs (static leg press) and dynamic exercise (DE) of the lower limbs (cycling). Subjective effort, systolic (SBP) and diastolic blood pressure (DBP), mean arterial pressure (MAP), rate pressure product (RPP) and the time between consecutive heart beats (RR-intervals) were measured. Time-domain (SDNN, RMSSD), frequency-domain (power in the low and high frequency band (LFP, HFP)) and geometric measures (SD1, SD2) as well as non-linear measures of regularity (approximate entropy (ApEn), sample entropy (SampEn) and correlation dimension D2) were calculated. Results: Although HR was similar during both exercise conditions (88±10 bpm), subjective effort, SBP, DBP, MAP and RPP were significantly enhanced during SE. HRV indicators representing overall variability (SDNN, SD 2) and vagal modulated variability (RMSSD, HFP, SD 1) were increased. LFP, thought to be modulated by both autonomic branches, tended to be higher during SE. ApEn and SampEn were decreased whereas D₂ was enhanced during SE. It can be concluded that autonomic control processes during SE and DE were qualitatively different despite similar heart rate levels. The differences were reflected by blood pressure and HRV indices. HRV-measures indicated a stronger vagal cardiac activity during SE, while blood pressure response indicated a stronger sympathetic efferent activity to the vessels. The elevated vagal cardiac activity during SE might be a response mechanism, compensating a possible co-activation of sympathetic cardiac efferents, as HR and LF/HF was similar and LFP tended to be higher. However, this conclusion must be drawn cautiously as there is no HRV-marker reflecting “pure” sympathetic cardiac activity.     

Heart Rate Variability in Healthy Six- to Sixteen-Year-Old Children

To study the age-related features of heart rate variability in children between the age of 6 to 16 years, cardiac rhythmograms of 5400 children were analyzed. It was found that parameters of the heart rate (M, SDNN, RMSSD, TF, VLF, and HF) in these children increase with age, changing in a wavelike way from year to year. Gender differences were observed in parameter M beginning from the age of 9; in parameters TF, VLF, and LF, the differences were observed beginning from the age of 11; and in parameters SDNN, RMSSD, and HF, the differences were observed from the age of 12 years. No differences between 16-year-old boys and girls in all the parameters of heart rate variability were found. It was shown that parameter VLF derived from ECG epochs of less than 5-min is suitable for physiological and clinical assessment. The obtained values of the parameters can be used in practice as reference standard.     

Heart Rate Variability During 24 Hours in Asthmatic Children

The autonomic circadian rhythm plays an important role in asthma. In recent years it has become possible to evaluate autonomic nervous function (ANF) using analysis of heart rate variability (HRV). We analyzed the HRV in the 24h period following the state without an asthma attack in order to study the relationship between asthma and ANF. The HRV was analyzed in 94 asthmatic children (ages 5–15 years). These subjects were divided into groups according to the severity of their asthma. After recording a 24h ambulatory electrocardiograph (AECG), the HRV was analyzed by a computer. Evaluation of the HRV was carried out using time-domain and frequency-domain analyses. The ANF of asthma subjects was decreased in comparison to the normal group. The severity of asthma had a significant effect on the %RR50 (the proportion of cycles during which the difference is > 50 ms), the SD (standard deviation; mean of standard deviation of all normal RR intervals for all 5-minute periods), the low-frequency (LF) band (0.04 to 0.15 Hz), and the high-frequency (HF) band (0.15 to 0.4 Hz) (%RR50: F = 4.31, p = 0.01; SD: F=3.48, p = 0.03; LF: F=3.67, p = 0.02; HF: F=3.41, p = 0.03). These values were lowest in the severe asthma group. With regard to the therapy grouping, the index that exhibited a significant difference was the NNA (mean of normal-to-normal RR intervals over 24h) (F = 4.43, p = 0.01) In conclusion, even in the normal condition in which the patient is free of an asthma attack, the ANF of asthma sufferers differs from that of normal children. It is possible that the different ANF of asthma sufferers is related to the severity of the asthma. (Chronobiology International, 14(6), 597–606, 1997)