心率变异和RT变异频域分析的方法学研究

心率变异作为检测自主神经系统功能平衡状态的无创性指标，日益受到重视，已成为心电信号处理中的研究热点之一。ＱＴ是心室肌复极化时间，从另一方面来反映自主神经系统的平衡状态。ＱＴ变异分析在临床应用上与心率变异分析是否有互补作用，目前这方面研究工作开展得不多。由于ＱＴ间期检测困难，一般以ＲＴ间期代替ＱＴ间期。建立了心率变异和ＱＴ变异测定方法。在采集２４ｈ心电信号后，首先要完成标志点的检测。较好地实现了心电Ｒ波标志点的检测和异位心跳的剔除，并采用以相关系数为条件的模板匹配方法检测出Ｔ波标志点。频域分析方法分别通过快速傅里叶变换法（ＦＦＴ）和自回归谱估计法（ＡＲ）实现了２４ｈ三维频谱显示图以及２４ｈＨＦ／ＬＦ和高频能量变化趋势图。以不同的频率控制受试者的呼吸，采集其心电数据，从ＲＲ间期和ＲＴ间期谱分析的结果可以看到，高频峰受到呼吸频率的调制，高频峰可能与迷走神经活动有关。这一过程也检验了心电信号采集、检测和谱分析方法的可靠性。建立的方法为今后进一步深入研究打下了基础。随着心率变异和ＱＴ变异的检测和分析技术的日趋成熟，一定会在一些疾病的早期诊断、监护及预后评估等方面发挥更大的作用     

时频分析在心率变异性研究中的应用

心率变异(HRV)包含着心血管神经体液调节的大量信息,由于信号提取的无创性,心率变异性分析是近年生理信号分析研究的热点。鉴于动态变化或病理状态下心电信号的非平稳特性,传统的时域和频域HRV分析有一定的局限性,而时频分析法在这方面显示出其明显的优越性。目前较常用的时频分析法有短时傅里叶变换(STFT)、Wigner-Ville分布(WVD)、小波变换等。本研究系统阐述了这3种时频分析方法在HRV分析中的应用,并提出了今后的研究方向和发展前景。     

儿童焦虑症的心率变异性频谱分析

目的:通过对焦虑症患儿与正常儿童心率变异性(HRV)的比较,探索焦虑症患儿心脏自主神经功能的特点。方法:选择34例焦虑症患儿与30名正常儿童,使用汉密顿焦虑量表(HAMA)进行评估,应用24小时动态心电图记录仪测定HRV并进行比较。结果:焦虑症患儿SDNN、SDANN、RMSSD与PNN50均低于正常对照组(P0.05);焦虑症患儿LF/HF高于正常对照(P0.05),焦虑症患儿HAMA总分与SDNN呈负相关(r=-0.31,P0.05),躯体性焦虑因子分与LF呈正相关(r=0.35,P0.05),精神性焦虑因子分与PNN50呈负相关。结论:儿童焦虑症患者在静息状态下交感神经功能亢进,迷走神经水平降低,以及交感神经与迷走神经功能均衡性失调,并与焦虑症状相关。     

基于多分辨率分析的心率变异性分析

目的：心率变异性蕴藏了大量有关心血管调节的信息,可作为定量反映自主神经功能及其对心血管的调控作用和反映心脏活动正常与否的重要指标之一。因此,主要研究了几种常用的心率变异性分析方法。方法：本论文应用多分辨率分析方法对HRV信号进行6尺度分解,计算小波系数的能量及其在各频段的分布,对cd3-cd6频段的能量进行分析比较。结果：充血性心衰患者各频段能量均值比正常人都要低,能量分别主要集中在高频段和低频段的偏低频部分,且两组的能量差异更为明显,与频域分析结果相比更为精确。结论：要得到带有普遍规律的实验结果,需要对不同的分析方法进行不断地改进和优化,并进行大量的研究工作。     

The Effects of Different Noise Types on Heart Rate Variability in Men

Purpose

To determine the impact of noise on heart rate variability (HRV) in men, with a focus on the noise type rather than on noise intensity.

Materials and Methods

Forty college-going male volunteers were enrolled in this study and were randomly divided into four groups according to the type of noise they were exposed to: background, traffic, speech, or mixed (traffic and speech) noise. All groups except the background group (35 dB) were exposed to 45 dB sound pressure levels. We collected data on age, smoking status, alcohol consumption, and disease status from responses to self-reported questionnaires and medical examinations. We also measured HRV parameters and blood pressure levels before and after exposure to noise. The HRV parameters were evaluated while patients remained seated for 5 minutes, and frequency and time domain analyses were then performed.

Results

After noise exposure, only the speech noise group showed a reduced low frequency (LF) value, reflecting the activity of both the sympathetic and parasympathetic nervous systems. The low-to-high frequency (LF/HF) ratio, which reflected the activity of the autonomic nervous system (ANS), became more stable, decreasing from 5.21 to 1.37; however, this change was not statistically significant.

Conclusion

These results indicate that 45 dB(A) of noise, 10 dB(A) higher than background noise, affects the ANS. Additionally, the impact on HRV activity might differ according to the noise quality. Further studies will be required to ascertain the role of noise type.     

基于小波变换的心率变异性动态分析

心率变异性（Heart rate variability，HRV）分析已成为无创检测心脏自主神经调节功能的一种手段。传统的频域分析，主要是计算HRV信号各频段功率，以及识别各频段的峰值频率，无论是采用经典谱估计还是AR模型都是以假设HRV信号近似平稳为前提的。这种假设在短程分析中可以基本满足，但在长程分析中，HRV信号的非平稳性便凸现出来。提出了一种基于小波变换的心率变异性动态分析方法，它不但可以获得传统的频域指标，而且可以获得它们随时间变化的动态值，称为短时功率，短时LF／HF比，特别是后者，可以动态评估自主神经活动的平衡情况。最后将这种分析方法应用到阿托品药物实验中，跟踪分析了阿托品对自主神经的影响情况。     

基于遥测技术的大鼠24小时心率变异性分析

本研究应用遥测技术连续记录大鼠在无束缚条件下24h心电信号，并通过心率变异性（Heart rate variability，HRV）频谱分析的方法研究大鼠24h自主神经活动。大鼠24hHRV分析结果表明：自主神经活动具有明显昼夜节律，在睡眠期迷走神经活动较活跃，而在清醒期以交感神经活动为主；HRV频谱中低频和高频成分的比值（LF／HF）随着睡眠深度的变化而波动。24hHRV分析可以获得自主神经系统活动的丰富信息，并有助于研究自主神经系统在生理和病理过程中的调控作用。     

心率变异性分析方法的现状与展望

心率变异(HRV)蕴涵着心血管神经及体液调节的大量信息，心率变异性分析是近年来心电信号处理领域的研究热点，它对于相关疾病的无创检测具有重要的临床意义。本文系统阐述了HRV经典分析方法及其最新研究进展，并提出了今后的研究方向。     

不同海拔健康青年男性心率变异性对比分析

应用短程心率变异性（HRV）时域、频域和非线性分析法，对比进入三个不同海拔高度自主神经系统（ANS）调节功能的特点。发现：与进入海拔1856m相比．海拔2800m平均正常RR间期的标准差（SDNN）、相邻RR间期差的均方根（rMSSD）、相差〉50ms的相邻RR间期占RR间期总数的百分比（PNNS0）、低频成分（LF）、高频成分（HF）以及总功率（TP）均有轻度升高，但无统计学差异；与进入海拔1856m和海拔2800m相比．海拔3040mSDNN、rMSSD、LF和HF显著降低。这表明进入海拔3040m副交感神经活动显著减弱、自主神经系统调节功能显著受抑。自主神经的这种变化有助于进一步阐明进入高海拔机体发生的病理生理学改变。     

麻醉期心率变异性的复杂性研究

采用近似熵、复杂度指标分析 38例受试者麻醉期心率变异性信号的复杂性。结果表明 :麻醉期心搏周期有显著性的复杂性变化 ,麻醉状态下心率变异性的复杂度 Kc、C1 、近似熵 (P<0 .0 5 )均显著低于清醒状态。进一步将麻醉期心率变异性信号分解为 1/f部分和非 1/f部分 ,并分析这两部分的复杂性。结果表明将心率变异性信号分解可显著提高复杂性分析指标的灵敏度。     

多分辨分析提取心率变异性中的睡眠结构信息

本文从工程分析的角度探索通过分析心率变异性推知健康人夜间睡眠结构的可行性、针对心率变化在睡眠过程中的特点,对心动间期信号作基于小波变换的多分辨率分析,深入考察了不同睡眠时相中的RRV(R-R interval variability)多分辨率信号,尤其在睡眠时相转换时的变化特点.建立了关于健康人睡眠规律和睡眠RR规律的规则库.综合分析RRV在多分辨率下的信息,用模糊逻辑推理系统对某时间段不同睡眠时相的隶属度进行推理.经对26例健康人睡眠RRV分析,与脑电人工分析结果比较,睡眠基本结构的平均符合率达到85%,醒觉和睡眠状态的平均符合率达到93%,证明用本方法进行睡眠结构分析是可行的.     

Heart rate variability in acute psychosis

Heart rate variability (HRV) provides reliable tools to assess the integrity and reactivity of autonomic nervous function. Our aim was to examine HRV in the resting condition and during different mental loads in acute psychosis compared to healthy controls. HRV was measured in 17 first-episode drug-naive patients with psychosis and 21 healthy controls during oddball tasks and while performing the Wisconsin Card Sorting Test. A discrete event series was constructed by an adaptive QRS detector algorithm and power spectrum estimation was carried out. The RMSSD (representing interval differences of successive heartbeats) and the amount of high frequency (HF) power were significantly reduced in patients. Moreover, the patients' HRV remained unaltered during the tasks, whereas in controls the HRV diminished with increasing mental load of the task. Patients with psychosis displayed less short-term HR reactivity than healthy controls. They also failed to adapt HRV according to the task-connected strain. Acute psychosis is characterized by a limited capacity to respond to external demands at the level of autonomic nervous system.     

Heart Rate Variability During Attention Phases in Young Infants

Heart rate variability during visual attention was studied in infants who were tested cross-sectionally at 14, 20, or 26 weeks of age. They were presented with a recording of a Sesame Street program on a TV screen. After heart rate had decelerated below the prestimulus level and then returned to prestimulus level, a computer-generated pattern replaced the Sesame Street display. Heart rate variability changed throughout attention. The change consisted of a decrease in variability during attention and a return to prestimulus levels approximately five seconds following attention termination. The heart rate and variability responses are consistent with a model of parasympathetic vagal influence on the heart in which vagal firing is increased during sustained attention and is inhibited during attention termination.     

Effect of low-dose endurance training on heart rate variability at rest and during an incremental maximal exercise test

We evaluated the effects of low-dose endurance training on autonomic HR control. We assessed the heart rate variability (HRV) of 11 untrained male subjects (36.8 +/- 7.2 years) at rest and during an incremental maximal aerobic exercise test prior to a 7-week preparatory period and prior to and following a 14-week endurance training period, including a low to high intensity exercise session twice a week. Total (0.04-1.2 Hz), low (0.04-0.15 Hz) and high (0.15-1.2 Hz) frequency power of HRV were computed by short-time Fourier transform. The preparatory period induced no change in aerobic power or HRV. The endurance training period increased peak aerobic power by 12% (P < 0.001), decreased the HR (P < 0.01) and increased all HRV indices (P < 0.05-0.01) at absolute submaximal exercise intensities, but not at rest. In conclusion, low-dose endurance training enhanced vagal control during exercise, but did not alter resting vagal HR control.     

慢性肾衰患者心率变异性改变

目的　通过心率变异性 (HRV)变化测定 ,探讨慢性肾功能衰竭 (CRF)患者的自主神经活动状况。方法　用2 4小时动态心电图分析系统 ,对 2 0例健康者 ,77例CRF患者 (其中 30例氮质血症 ,4 7例尿毒症 )心率变异性的时域指标进行对比研究。结果　CRF患者心率变异性的测定结果为 :SDNN 85 .2 8± 19.96 ,SDANN 75 .5 5± 2 2 .4 7,r-MSSD19.2 2± 11.82 ,PNN50 6 .7± 14 .79,各项指标均明显低于健康者 (P <0 .0 1)。氮质血症期与尿毒症期心率变异性无明显差别。结论　通过HRV时域分析发现 ,CRF患者有自主神经调节功能紊乱。CRF氮质血症期患者已出现HRV下降 ,提示CRF患者早期就存在自主神经功能损害。     

糖尿病人心率变异的李雅普洛夫指数的计算

采用常规的李雅普洛夫指数定义的方法和长度演化法，面积演化法分别计算１０例正常人和１０例糖尿病人的李雅普洛夫指数，结果显示糖尿病人的李雅普洛夫指数明显低于正常人。它反映了植物神经功能受到损伤，同时还显示心电图数据不必大量采集便能说明问题。     

HRV非线性动力学分析的动物实验初步研究

采用非线性动力学分析方法,观察了交感,迷走神经单独作用和冠状动脉狭窄时,非线性动力学参数的改变,以探讨非线性动力学参数所反映的心脏生理功能和心脏电生理学意义。     

Changes in Heart Rate Variability during a tonic immobility test in quail

Tonic immobility (TI) is an unlearned fear response induced by a brief physical restraint and characterized by a marked autonomic nervous system involvement. This experiment aimed at studying the relative involvement of both autonomic sub-systems, the sympathetic and parasympathetic nervous systems, during TI, by analyzing Heart Rate Variability. Quail selected genetically for long (LTI) or short (STI) TI duration and quail from a control line (CTI) were used. The animals were surgically fitted with a telemetric device to record electrocardiograms before and during a TI test. Heart rate did not differ between lines at rest. The induction of TI, whether effective or not, induced an increase in HR characterized by a shift of the sympathovagal balance towards a higher sympathetic dominance. Parasympathetic activity was lower during effective than during non-effective inductions in CTI quail. During TI, the increase in sympathetic dominance was initially maintained and then declined, while relative parasympathetic activity remained low, especially in CTI and STI lines. The end of tonic immobility was characterized by a rise in overall autonomic activity in all lines and an increase in parasympathetic influence in CTI and STI quail. To conclude, the susceptibility to TI cannot be explained only by autonomic reflex changes. It is probably strongly related to the perception of the test by the quail. During TI, the differences between lines in autonomic responses probably reflect behavioural differences in the fear response.     

心动周期信号中独立成分的分离

采用一项新的统计信号处理技术——独立成分分析提取心动周期信号子成分。从 10名受试者的仰卧和站立体位分别采集 8m in心电信号 ,进而提取心动周期信号。按时间延迟把心动周期信号分成 5组 ,进行独立成分分析 ,重构出两组成分。两组成分分别经傅立叶变换 ,结果显示一组信号成分集中于低频区域 (称为 IC1) ,另一组集中于高频区域 (称为 IC2 )。从仰卧位到站位 IC1的功率显著增加 (P<0 .0 1) ,IC2的功率没有显著的变化 (P>0 .0 5 ) ,IC1的功率占总功率的比值显著增加 (P<0 .0 1)。两体位的比较研究结果表明采用独立成分分析心动周期信号得到的两组成分中 ,IC1可以表征交感神经系统的活动 ,而 IC2表征了副交感神经系统的活动。由这些成分得到的数字和图谱信息可以分别定量评价交感和副交感神经系统的功能     

利用R—R间期相关维数对心率变异的分析

本文应用混沌理论，研究了心率变异情况下Ｒ－Ｒ间期的相关维数。对正常生理状态下人清醒与睡眠阶段，及临床－２４小时ＨＯＬＴＥＲ记录的Ｒ－Ｒ间期，分段计算其相关维数，结果表明，当其中某段Ｒ－Ｒ间期发生明显改变时，相关维减小。