Interaction between Heart Rate and Heart Rate Variability

Heart rate variability (HRV) is significantly associated with average heart rate (HR), therefore, HRV actually provides information on two quantities, that is, on HR and its variability. It is difficult to conclude which of these two plays a principal role in the HRV clinical value, or in other words, what is the HR contribution to the clinical significance of HRV. Moreover, the association between HRV and HR is both a physiological phenomenon and a mathematical one. The physiological HRV dependence on HR is determined by the autonomic nervous system activity, but the mathematical one is caused by the nonlinear relationship between RR interval and HR. By employing modification methods of the HRV and HR relationship, it is possible to investigate the HR contribution to the HRV clinical value. Recent studies have shown that the removal of the HR impact on HRV makes HRV more predictive for noncardiac death, however, the enhancement of this impact causes HRV to be a better predictor of cardiovascular mortality. Thus, HR seems to constitute a cardiovascular factor of the HRV predictive ability. HR also influences the reproducibility of HRV, therefore, HR changes should be considered when one compares HRV measurements in a given patient. This review summarizes methodological aspects of investigations of the HRV and HR interaction as well as latest observations concerning its clinical utility. The issues discussed in this article should also refer to any other heart rate dynamics analysis which indices are significantly associated with HR.     

Heart Rate and Heart Rate Variability in Normal Young Adults

Heart Rate and Heart Rate Variability. Introduction: The relationships between heart rate (HR) and HR variability (HRV) are not simple. Because both depend on the autonomic nervous system (ANS), they are not independent variables. Technically, the quantification of HRV is influenced by the duration of the cardiac cycles. The complexity of these relationships does not justify ignoring HK when studying HRV, as frequently occurs. Methods and Results: Using spectral and nonspectral methods, the HR and various normalized and non-normalized indices of HRV were studied in 24-hour recordings of a homogeneous cohort of seventeen 20-year-old healthy males. The HR-HRV relationships were appraised by analyzing the same data in two different ways. The 24 mean hourly values provide consistent information on the circadian behavior of the indices, while the average 24-hour individual data show a wide spectrum of normality. Combined approaches allow assessment of the direct impact of RR interval on HRV evaluation. The correlations between HR and normalized indices of HRV arc weaker in 24-hour individual data than in pooled hourly data of the same individuals. These correlations are close to 1 in the latter case, which does not mean that measuring HRV is simply another method of evaluating HR, but that normal physiology supposes a harmonious behavior of the various indices. When considered individually without normalization, the specific indices of vagal modulation (high-frequency band of the spectrum, short-term HR oscillations of the nonspectral analysis) consistently increase at night and diminish during the day. However, the low-frequency power, which supposedly reflects sympathetic influences, also increases at night, whereas more logically the longer HR oscillations would predominate during the day. Moreover, the selective analysis of HR oscillations during HR acceleration or decrease indicates that their behavior differs accordingly. Conclusion: We recommend that closer attention be paid to the complex relationships between HR and HRV. The strong correlations found in healthy subjects may reflect either the physiological harmony of ANS functions or simple redundancy. Their tendency to deteriorate in diseased hearts suggests that redundancy is not the cause and that abnormalities of ANS functions are not demonstrated by HRV analysis alone.     

心率和心率变异性与心力衰竭及预后的相关性

目的　探讨心率及心率变异性与心力衰竭及预后的相关性。方法　入选2010年10月至2012年6月期间就诊宁夏医科大学总医院心内科的慢性充血性心力衰竭患者245例,根据住院期间平均静息心率水平分为3组：A组：50～70次/分;B组：71～90次/分;C组：＞90次/分;共随访1年,完成随访共230例。其中共有97例行动态心电图检查,按患者心功能分级分为Ⅱ级组、Ⅲ级组、Ⅳ级组,同时选择26例正常健康人为对照组。收集上述研究对象的心率变异性时域指标进行对比分析,包括正常RR间期标准差（SDNN）、5　min均值标准差（SDANN）、相邻RR间期相差＞50　ms的个数占总心跳数的百分比（PNN50）、全程相邻RR间期之差的平方根（RMSSD）。结果随着心率水平增加,随访终点射血分数明显降低,再住院率及病死率明显增加（P＜0.01）。不同心率水平心力衰竭患者Cox生存分析显示心率越快,生存率越低。心力衰竭组与对照组相比SDNN、SDANN、PNN50、RMSSD降低（P＜0.01或P＜0.05）,随着心力衰竭程度的加重,SDNN、SDANN、PNN50、RMSSD下降越明显（P＜0.01）。结论　心率越快,心力衰竭预后越差;心力衰竭患者存在心率变异性降低,心率变异性越低,心功能越差。     

钉螺密度与繁殖率研究

目的通过定量研究影响血吸虫中间宿主-钉螺种群动力学与繁殖的内在(种群密度负反馈)因素和外界(环境)因素,从而探索钉螺种群控制阀值以指导控制钉螺。方法在四川省蒲江县大塘镇选择一无螺环境放置14个钉螺框,2次随机抽取100个有螺环境,分别采集2 820和2 826只钉螺,按不同密度组2、4、6、8、10、20、40、80、100、150、200、400、800和1 000只/框放入钉螺,低密度组(≤40只)中保证雌雄比例1∶1,高密度组(≥80只)随机放入不同数量的钉螺。实验分2次。实验结束后分别将2次实验的14框钉螺全部拣出,观察新螺繁殖率,记录新老螺死亡率。结果第1次实验低密度组新螺繁殖率平均值为80.07%,新螺死亡率平均值为16.86%,老螺死亡率平均值为2.73%;高密度组新螺繁殖率平均值为37.06%,新螺死亡率平均值为19.83%,老螺死亡率平均值为35.51%。第2次实验低密度组新螺繁殖率平均值为80.40%,新螺死亡率平均值为4.65%,老螺死亡率平均值为11.46%;高密度组新螺繁殖率平均值为22.81%,新螺死亡率平均值为4.77%,老螺死亡率平均值为68.06%。高低密度组之间新螺繁殖率、新螺死亡率、老螺死亡率经χ2检验,差异有统计学意义(P<0.05)。结论定量研究证明,种群密度影响钉螺繁殖率,种群密度越低,则繁殖率越高,反之亦然。     

新疆阿克苏地区维吾尔族35岁以上人群血脂异常患病率、知晓率、治疗率及控制率的调查研究

目的调查分析新疆阿克苏地区维吾尔族35岁以上人群血脂异常患病率、知晓率、治疗率及控制率。方法本研究于2012年4月至2014年6月采用分层整群随机抽样的方法,对阿克苏地区8县1市35岁以上成年维吾尔族人群进行现场调查。结果新疆阿克苏地区维吾尔族35岁以上成年人总血脂异常患病率为53.6%,性别与年龄分组组间患病率无明显差异。女性亚组中,55岁以上组血脂异常患病率明显高于35~54岁组(53.1%比51.5%,P=0.024)。血脂异常的人群中知晓率为34.5%,治疗率为28.0%,控制率为16.8%。总人群和35~54岁组女性血脂异常治疗率显著高于男性(总人群为30.3%比24.9%,P=0.004;35~54岁组为29.7%比24.2%,P=0.028)。总人群女性血脂异常的控制率显著高于男性(18.1%比15.0%,P=0.047)。结论新疆阿克苏地区35岁以上维吾尔族是血脂异常高发的人群,其血脂异常知晓率、治疗率及控制率较低。男性血脂异常治疗率和控制率显著低于女性,尤其应重视男性血脂异常的防治。     

原发性高血压患者窦性心率震荡与心率变异性

目的 检测单纯原发性高血压(EH)患者窦性心率震荡(HRT)及心率变异性(HRV).方法 EH患者60例和健康人50例分别为高血压组和对照组,亚组研究分析降压治疗 倍他洛克组和降压治疗组的HRT与HRV.根据24 h动态心电图记录资料,分别计算各组HRT的两个参数震荡初始值(TO)和震荡斜率值(TS)以及HRV的全部NN间期的标准差(SDNN)、全部相邻NN间期之差的均方根值(RMSSD)和低频/高频(LF/HF).结果 1)高血压组TO、TS、TO TS、SDNN、RMSSD及LF/HF分别为:52、48、46、42、41、38例;对照组分别为:2、3、0、5、1、3例;高血压组上述6种指标的阳性检出率均高于对照组(P<0.01);2)降压治疗 倍他洛克组及降压治疗组TO、TS、TO TS阳性检出率差异无统计学意义,降压治疗 倍他洛克组的SDNN、RMSSD及LF/HF分别为:12、13、9例;降压治疗组分别为:30、28、29例,降压治疗 倍他洛克组SDNN、RMSSD及LF/HF的阳性检出率明显低于降压治疗组(P<0.01).结论 单纯EH患者有显著的HRT减弱及HRV的异常,HRT现象不受β受体阻滞剂的影响.     

南海城乡结合地区老年人高血压患病及其健康知识知晓率调查

目的了解南海城乡结合地区老年人高血压患病现状及高血压健康知识知晓情况,为本地区老年人高血压健康管理提供科学依据。方法采用分层随机抽样的方法,随机抽取本地区60岁以上老年人834人,由经过培训合格的调查员进行面对面问卷调查和体格检查。结果高血压患病率为50.36%,其中男性为51.32%,女性为49.56%。对高血压6种危险因素(肥胖、精神紧张、吃盐多、缺乏运动、吸烟、吃糖多)知晓率分别为51.32%、38.49%、37.05%、31.41%、24.22%、15.83%。高血压诊断标准知晓率为24.34%,高血压患者终生药物治疗知晓率为59.47%。结论本地区老年人高血压患病率较高,高血压相关健康知识知晓率较低,应进一步加强社区高血压知识的宣传教育工作,全面防治高血压的发生。     

原发性高血压患者窦性心率震荡与心率变异性

目的检测单纯原发性高血压(EH)患者窦性心率震荡(HRT)及心率变异性(HRV)。方法 EH 患者60例和健康人50例分别为高血压组和对照组,亚组研究分析降压治疗+倍他洛克组和降压治疗组的 HRT 与HRV。根据24 h 动态心电图记录资料,分别计算各组 HRT 的两个参数震荡初始值(TO)和震荡斜率值(TS)以及HRV 的全部 NN 间期的标准差(SDNN)、全部相邻 NN 间期之差的均方根值(RMSSD)和低频/高频(LF/HF)。结果 1)高血压组 TO、TS、TO+TS、SDNN、RMSSD 及 LF/HF 分别为:52、48、46、42、41、38例;对照组分别为:2、3、0、5、1、3例;高血压组上述6种指标的阳性检出率均高于对照组(P<0.01);2)降压治疗+倍他洛克组及降压治疗组 TO、TS、TO+TS 阳性检出率差异无统计学意义,降压治疗+倍他洛克组的 SDNN、RMSSD 及 LF/HF 分别为:12、13、9例;降压治疗组分别为:30、28、29例,降压治疗+倍他洛克组 SDNN、RMSSD 及 LF/HF 的阳性检出率明显低于降压治疗组(P<0.01)。结论单纯 EH 患者有显著的 ...     

The Relationship Between Heart Rate Recovery and Heart Rate Variability in Coronary Artery Disease

Background: Reduced heart rate recovery (HRR) in coronary artery disease (CAD) is predictive of increased cardiovascular mortality and is related to reduced parasympathetic tonus. Objective: To investigate HRR and heart rate variability (HRV) measured at steady state condition and the relationship between these two parameters in CAD. Materials and Methods: In our study, we enrolled 33 (28 males, mean age 52.4 ± 9.6 years) patients with CAD who did not have heart failure, atrial fibrillation, pacemaker, and any disease state that could affect the autonomic functions and 38 age‐matched healthy subjects (21 males, mean age 48.3 ± 7.8 years). All the patients underwent submaximal treadmill exercise testing (Bruce protocol). HRR was calculated by subtracting the heart rate values at the 1st, 2nd, and 3rd minutes of the recovery phase from the peak heart rate (HRR₁, HRR₂, HRR₃). Before exercise testing, short‐term steady state HRV analyses of all subjects were obtained with the time‐ and frequency‐domain methods and were correlated to HRR. For frequency‐domain analysis, low‐frequency HRV (LF, 0.004–0.15 Hz), high‐frequency HRV (HF, 0.15–0.5 Hz), and LF/HF ratio were measured for 5 minutes in the morning. For time‐domain analysis, standard deviation of the normal‐to‐normal NN intervals (SDNN), square root of the mean squared differences of successive N‐N intervals (RMSSD), and proportion derived by dividing the number of interval differences of successive N‐N intervals greater than 50 ms by the total number of N‐N intervals (pNN50) were obtained. Only HRR₃ was used for the correlation analysis. Results: In CAD groups, the HF, an indicator of parasympathetic activation, was significantly reduced, whereas the LF and LF/HF values, which are indicators of sympathetic activity, were increased (P = 0.0001 for each parameter). The time‐domain parameters SDNN, RMSSD, and pNN50 were significantly reduced in the patient group (P = 0.0001, P = 0.009, and P = 0.0001, respectively). Similar to the HRV parameters, the HRR₁, HRR₂, and HRR₃ values were significantly reduced in the patient group (P = 0.0001 for each parameter). We observed a significant negative correlation between HRR₃ and LF (r =?0.67, P = 0.0001) and between HRR₃ and LF/HF (r =?0.62, P < 0.0001), while there was a significant positive correlation between HRR₃ and HF, SDNN, RMSSD, and pNN50 (r = 0.69, P = 0.0001; r = 0.41, P = 0.0001; r = 0.31, P = 0.008; and r = 0.44, P = 0.0001). Conclusions: HRR and HRV are significantly reduced in CAD. The reduction in HRR is parallel to the changes in HRV parameters. HRR, which can be measured easily in the recovery phase of exercise testing, can be used to detect the depression of parasympathetic tonus and to evaluate the basal autonomic balance in this patient group.     

Influence of Heavy Cigarette Smoking on Heart Rate Variability and Heart Rate Turbulence Parameters

Background: Cigarette smoking increases the risk of cardiovascular events related with several mechanisms. The most suggested mechanism is increased activity of sympathetic nervous system. Heart rate variability (HRV) and heart rate turbulence (HRT) has been shown to be independent and powerful predictors of mortality in a specific group of cardiac patients. The goal of this study was to assess the effect of heavy cigarette smoking on cardiac autonomic function using HRV and HRT analyses. Methods: Heavy cigarette smoking was defined as more than 20 cigarettes smoked per day. Heavy cigarette smokers, 69 subjects and nonsmokers 74 subjects (control group) were enrolled in this study. HRV and HRT analyses [turbulence onset (TO) and turbulence slope (TS)] were assessed from 24‐hour Holter recordings. Results: The values of TO were significantly higher in heavy cigarette smokers than control group (?1.150 ± 4.007 vs ?2.454 ± 2.796, P = 0.025, respectively), but values of TS were not statistically different between two groups (10.352 ± 7.670 vs 9.613 ± 7.245, P = 0.555, respectively). Also, the number of patients who had abnormal TO was significantly higher in heavy cigarette smokers than control group (23 vs 10, P = 0.006). TO was correlated with the number of cigarettes smoked per day (r = 0.235, P = 0.004). While LF and LF/HF ratio were significantly higher, standard deviation of all NN intervals (SDNN), standard deviation of the 5‐minute mean RR intervals (SDANN), root mean square of successive differences (RMSSD), and high‐frequency (HF) values were significantly lower in heavy smokers. While, there was significant correlation between TO and SDNN, SDANN, RMSSD, LF, and high frequency (HF), only HF was correlated with TS. Conclusion: Heavy cigarette smoking has negative effect on autonomic function. HRT is an appropriate noninvasive method to evaluate the effect of cigarette on autonomic function. Simultaneous abnormal HRT and HRV values may explain increased cardiovascular event risk in heavy cigarette smokers.     

Heart Rate and the Cardiometabolic Risk

Resting heart rate is a well recognized marker of autonomic nervous system tone, and in many population studies has been found to be a significant correlate of blood pressure, increased body mass index, and metabolic disturbances. This association is particularly striking in patients with hypertension or diabetes, and cardiovascular morbidity related to high heart rate in these conditions seems to depend mainly on the clustering of these risk factors. The prospective relationship between tachycardia and metabolic abnormalities found in longitudinal studies indicates that the adrenergic overdrive is the cause rather than the consequence of the insulin resistance state. Findings from observational studies and clinical trials have shown that heart rate measured during the follow-up provides prognostic information over and above heart rate measured at baseline, whereas the predictive value of heart rate measured out of the office is still debated. Antihypertensive drugs that decrease blood pressure and heart rate through a reduction of the sympathetic outflow may be more beneficial in clinical situations characterized by heightened sympathetic activity associated to insulin resistance.     

静息心率与心血管疾病的研究进展

静息心率与心血管疾病的关系,近年来日益受到人们的重视。随着研究的不断进展,静息心率被作为心血管疾病的危险因素逐步被人们所接受。同时,也有学者发现静息心率是心血管疾病患者死亡的预测因子,这使静息心率逐步成为人们的研究热点。现综述了静息心率与心血管疾病目前的研究进展,并初步提出了心血管疾病患者使用β受体阻滞剂与以往不同的保护机制。     

Hemodynamics of AV Synchrony and Rate

Dual-chamber pacing was developed to overcome the symptomatic and hemodynamic deficiencies of single-chamber ventricular pacing. It was later suggested that the benefit of dual-chamber pacing with activity was not because ofAV synchrony but because of the ability to increase rate. It is suggested that the benefit of dual-chamber pacing has been underestimated by lack of an appropriately programmed AV delay.     

频率适应性起搏器的研究进展

频率适应性起搏器是起搏器发展史上的重大进展。现对频率适应性起搏器作简要介绍,并对近年来频率适应性起搏器传感器(特别是双感受器传感器)、算式和适应证的研究进展进行简要综述。     

心律震荡

急性心肌梗死患者是心源性猝死的高危人群 ,寻找猝死高危人群的预测指标一直是心血管领域备受重视的课题。最近 ,国外学者研究了一个新的心电生理预测指标———心律震荡 ,认为这是一个独立于现有预测指标的新指标 ,其灵敏度和特异度都很高。本文就心律震荡这一新指标作一综述。