Estimating oxygen consumption from heart rate and heart rate variability without individual calibration

Heart rate (HR) as an estimator of oxygen consumption (VO(2) ) usually requires HR to be individually calibrated in a separate test. This study examined the validity of a new HR - and HR variability-based method (Firstbeat PRO heartbeat analysis software) in the estimation of VO(2) in real-life tasks. The method takes into account the respiration rate determined from HR variability and the differences in the on/off dynamics of HR and VO(2) , and no calibration tests are needed. Ten men and nine women performed 25 tasks representing different types of daily activities. Portable devices were used to measure R-to-R intervals (ECG), VO(2) and respiration rate. In pooled regression analysis, the estimated VO(2) accounted for 87% of the variability in the actual VO(2) , SEE 3·5 ml min(-1) kg(-1) (1 MET). At group level, the method underestimated slightly the measured VO(2) (mean difference - 1·5 ml min(-1) kg(-1) or - 0·4 METs). Some of the values at low exercise intensities were markedly underestimated, but the agreement was better during light and heavy activities. The limits of agreement for the data were from -8·4 to 5·4 ml min(-1) kg(-1) or from -2·4 to 1·5 METs. At individual level, the average deviations of the predicted VO(2) ranged from -1·0 to 0·6 METs and R(2) from 0·77 to 0·94, respectively. The present data indicate that the prediction method may be considered sufficiently accurate to determine the average VO(2) in field use, but it does not allow precise estimation of VO(2) .     

Taichiquan acutely increases heart rate variability

A group of 15 elderly men and 14 young male students of physical education made twice a series of Taichiquan (TCQ) practices. Their electrocardiograms were recorded on tape-recorder and heart rates and heart rate variability (HRV) were calculated from digitized data. Here we report the results of recordings in supine positions before and after the first and second series of TCQ. Intervals between heart beats (RRIs) and their standard deviation (SDNN) increased in older men from recordings before the exercise to postexercise. In young subjects the SDNN and total variance (TV) of RRIs increased. HRV increases immediately after TCQ-exercise in young and old male healthy subjects. Whether these practices have permanent effects and effects in patients need controlled and prospective studies.     

心肌梗塞患者24小时和短期节段性心率变异分析

目的：探讨心肌梗塞（ＭＩ）后心率变异（ＨＲＶ）的特点，昼夜节律变化的规律及其临床意义。方法：采用动态心电图（ＡＥＣＧ）技术连续观察了２８例急性心肌梗塞（ＡＭＩ）患者（平均１１天）、３２例陈旧性心肌梗塞（ＯＭＩ）患者（平均８１天）及３６例正常人的ＨＲＶ多项时域指标。结果：ＨＲＶ在ＡＭＩ患者明显缩小，在ＯＭＩ患者已基本恢复，但仍低于正常人。如以ＨＲＶ＜５０ｍｓ为异常，ＡＭＩ、ＯＭＩ及正常人３组的阳性率分别为４２．９％、６．２％和０。与未发生严重心律失常者比较，ＯＭＩ组发生严重心律失常者ＨＲＶ减小。ＡＭＩ患者ＨＲＶ昼夜节律被破坏。结论：对于预测心肌梗塞患者的预后，２４小时ＨＲＶ分析较之短期节段性ＨＲＶ分析具有更大价值。     

Heart rate turbulence and heart rate variability in patients with atrial synchronous ventricular pacing

Background: Heart rate turbulence (HRT) and heart rate variability (HRV) have been shown to be independent and powerful predictors of mortality in a specific group of cardiac patients. Pacing has unfavorable effects on autonomic function. Our aim is to investigate autonomic responses to atrial synchronous ventricular pacing (VDD) by evaluating HRT and HRV parameters.
Methods and Results: The study groups comprised 12 control and 12 patients without organic heart disease and with normal sinus function who were implanted with a permanent VDD pacing system for high-degree atrioventricular block. The HRV and HRT analysis were assessed from a 24-hour Holter recording. There was no statistically significant difference between the two groups for HRV parameters. When HRT parameters were compared, turbulence onset was significantly higher in the cardiac paced group than the controls group (2.729 ± 8.818 vs –1.565 ± 8.301, P = 0.006), but no statistically significant difference was found between the two groups for turbulence slope (11.166 ± 10.034 vs 31.675 ± 28.107, P = 0.68). The number of patients who had abnormal HRT onset was significantly higher in the paced group than controls (9 vs 2, P = 0.004).
Conclusion: Atrial synchronous pacing has unfavorable effects on autonomic function. Altered ventricular depolarization sequence may lead to changes in autonomic response. Although we found no difference in HRV parameters between the control and VDD patient groups, the HRT onset and number of patients with abnormal HRT onset was significantly higher in VDD patients. HRT onset can be a better way of noninvasive autonomic response predictor in VDD patients.     

心力衰竭患者的心率变异分析研究

目的探讨慢性心力衰竭(CHF)患者心率变异性(HRV)的变化,研究了HRV各指标与心功能程度(NYHA分级)、原发病、心衰类型的关系。方法选取CHF患者76例与正常对照组24例进行回顾性分析。结果正常对照组比较,CHF试验组SDNN,SDANN降低,差异有统计学意义。结论CHF患者HRV部分指标变化可作为判定CHF严重程度的参考指标。各项HRV指标变化大小可能与CHF患者的原发病无关,但部分似与心衰类型有关。     

Role of endothelin in modulation of heart rate variability in patients with decompensated heart failure

Endothelin-1 (ET-1) can modulate central and peripheral sympathetic outflow. However, if increased ET-1 levels contribute to autonomic perturbations in the setting of congestive heart failure (CHF) is not known. The purpose of this study was to determine if increased ET-1 levels contribute to the depressed HRV in patients with CHF. Sixty-four patients were admitted to the hospital for treatment of decompensated CHF (mean age 59+/-12 years, NYHA Classes III [72%] and IV [28%]). Time- and frequency-domain HRV measures were obtained from 24-hour Holter recordings. Neurohormonal activation was assessed by measuring plasma renin activity (PRA), aldosterone, norepinephrine, and ET-1 levels. Among the time-domain HRV indices, ET-1 correlated negatively with the standard deviation of RR intervals (SDNN) (r = - 0.38, P = 0.002) and standard deviation of all 5-minute mean RR intervals (SDANN5) (r = - 0.48, P < 0.0001), but not with time-domain indices indicative of parasympathetic modulation. Among the frequency-domain HRV indices, ET-1 correlated negatively with the total power (r = - 0.32, P = 0.01) and ultralow frequency power (ULF) (r = - 0.43, P = 0.0004), but not with indices of parasympathetic (high frequency) or sympathovagal (low frequency) modulation. Using multiple linear regression, adjusting for clinical parameters, drug therapies, and other neurohormones, the strong negative relationship between ET-1 and SDNN (P = 0.027), SDANN5 (P = 0.002), and ULF power (P = 0.017) persisted. In conclusion, ET-1 may play an important role in the autonomic dysfunction characteristic of CHF. The correlation between ET-1 levels and prognostically important indices of overall HRV suggests that these HRV measures are better markers of neurohormonal activation in CHF, which may partially account for their greater discriminatory power for risk stratification.     

Heart rate variability following neonatal heart surgery for complex congenital heart disease

BACKGROUND: Altered cardiac autonomic control may play a role in the morbidity and mortality suffered by neonates who undergo surgery for complex congenital heart disease (CHD). The purpose of this study was to evaluate cardiac autonomic activity, as measured by spectral indices of heart rate variability (HRV), prior to and early after infant surgery for CHD and attempt to correlate HRV indices with clinical outcome. In addition, we assessed the hypothesis that single-ventricle physiology and surgical interruption of the great arteries negatively affects HRV. METHODS: Sixty neonates prospectively wore 24-hour Holter monitors at three time points: before and early after CHD surgery, and at 3- to 6-month follow-up. Standard spectral indices of HRV were measured. RESULTS: In the early postoperative time point, patients with single-ventricle physiology had lower low-frequency power (LF) compared to patients with two ventricles (P=0.040). Surgical interruption of the great arteries did not affect HRV in this cohort. For the entire cohort, LF (P=0.004) and high-frequency power (HF) (P<0.001) increased over the three time points, while LF/HF (P=0.119) did not significantly change. In the multivariable linear regression model, significant predictors of longer postoperative hospital stay included longer total support time (P=or<0.001), longer duration of inotrope support (P=0.012), elevated mean heart rate at postoperative time point (P=0.002), and lower LF/HF ratio at the postoperative time point (P=0.014). CONCLUSION: Patients with single-ventricle physiology have a significant physiologic reduction in LF in the early postoperative period compared to patients with two ventricles. Diminished cardiac autonomic control is associated with longer hospitalization following neonatal cardiac surgery.     

左西孟旦对高血压患者心率变异性的影响

目的探讨左西孟旦对高血压患者心率变异性（H RV ）的影响。方法选取本院治疗的57例高血压患者作为研究对象,所有患者均给予左西孟旦静脉滴注,患者治疗前2周及治疗6周后接受 Holter记录,分析治疗前后患者HRV变化情况。结果治疗后患者正常R-R间期标准差（SDNN）、相邻R-R间期标准差（RMSSD）以及相邻R-R间期大于50 ms的百分比（PNN50）均明显高于治疗前,与治疗前相比差异有统计学意义（P＜0．05）;高频（HF）较治疗前显著上升（P＜0．05）,而LF/HF较治疗前明显下降（P＜0．05）。结论左西孟旦能有效地改善高血压患者HRV ,临床上治疗高血压可以使患者更多的收益。     

Effect of intensive training on heart rate variability in prepubertal swimmers

BACKGROUND: In children, there is very limited evidence focusing on the beneficial effect of exercise training on heart rate variability (HRV) during childhood. Despite the fact that more and more children are engaged in intensive training programs, the question arises if such intensive training involves deleterious effects on the cardiac autonomic nervous system during childhood. Thus the aim of the present study was to compare HRV parameters in highly trained swimmer boys and untrained counterparts. METHODS: Twenty prepubertal boys, aged 11-12 years old, took part in the study. The children were divided into 11 highly trained prepubertal swimmers (training sessions of 8-10 h weekly for at least 4 years) and 9 age-matched active boys. HRV analysis was performed on diurnal recordings in the frequency (short-term recordings 6 min the most 'vagal') and time (long-term recordings 4 h centred on the 6 min most 'vagal') domains. RESULTS: No significant differences were obtained between groups for all frequency variables whatever the mode of expression (absolute in ms2, relative in Ln or %). All time-domain components were not significantly different in swimmers and untrained boys. CONCLUSIONS: The results of the present study demonstrate that participating intensively in swimming training does not induce in children changes in HRV indices. Neither time nor domain HRV variables were significantly different between untrained and highly trained prepubertal boys. Thus, intensive training in healthy children does not involve deleterious effects on HRV.     

Effects of whole‐body vibration on heart rate variability: acute responses and training adaptations

Heart rate variability (HRV) is a noninvasive and practical measure of cardiac autonomic nervous system function, mainly the sympathetic and parasympathetic modulations of heart rate. A low HRV has been shown to be indicative of compromised cardiovascular health. Interventions that enhance HRV are therefore beneficial to cardiovascular health. Whole‐body vibration (WBV) training has been proposed as an alternative time‐efficient exercise intervention for the improvement of cardiovascular health. In this review, we discuss the effect of WBV both acute and after training on HRV. WBV training appears to be a useful therapeutic intervention to improve cardiac autonomic function in different populations, mainly through decreases in sympathovagal balance. Although the mechanisms by which WBV training improves symphathovagal balance are not yet well understood; enhancement of baroreflex sensitivity, nitric oxide bioavailability and angiotensin II levels seem to play an important role.     

Consistency of multicenter measurements of heart rate variability in survivors of acute myocardial infarction

Heart rate variability (HRV) analysis from 24-hour ambulatory ECG has been widely used in risk stratification of patients after myocardial infarction (MI). The accuracy of HRV assessment is known to potentially vary when different commercial systems are used. However, the consistency of HRV measurements has never been fully investigated. Twenty-six post-MI patients (mean age 59 +/- 8 years, 22 men) were studied, of whom 13 succumbed to sudden cardiac death (SCD) within 1 year and 13 remained alive for at least 3 years (MI survivors). Each patient had a 24-hour Holter ECG recorded before hospital discharge. HRV analysis was performed four times from the same recordings using three different Holter tape analysis systems (Marquette, Reynolds, and CardioData) by four independent operators (CardioData system was used twice, once in the United Kingdom and once in the United States). Mean normal-to-normal RR intervals (mNN) and 3 HRV parameters (SDNN, RMSSD, and HRV triangular index [HRVi]) were derived from each recording. The consistency of mNN and HRV measurements was evaluated by coefficient of variance (CV) and by the Bland-Altman method. The results demonstrated that (1) all indices measured by different systems were statistically similar (P = NS) except the measurement of RMSSD (P = 0.01), (2) the measurements of mNN were highly reproducible with a maximum mean difference of 1.8 +/- 13.8 ms and maximum limits of agreement from -14.6 to +15.6 ms. The maximum mean differences were--1.8 +/- 1.4 unit and 4.4 +/- 9.6 ms for HRVi and SDNN, respectively, and RMSSD was less reproducible with a maximum mean difference of--11.1 +/- 11.5 ms, and limits of agreement from -16.2 to +9.6 ms; and (3) the consistency of mNN (CV 0.9% +/- 0.9%) was significantly higher than that of HRVi, SDNN, and RMSSD (P < 0.0001). The consistency of HRVi was similar to that of SDNN (4.8% +/- 2.1% vs 5.7% +/- 4.8%, P = 0.4), and the consistency of RMSSD (26.6% +/- 13.3%) was significantly lower than that of the other measurements (P < 0.00001). In conclusion, the measurements of mNN by different analytical systems are the most consistent among the parameters studied. The global 24-hour measurements of HRV (SDNN and HRVi) are highly reproducible, whereas the measurement of short-term HRV components (RMSSD) is significantly less reproducible.     

腹腔镜手术对小儿心率变异性的影响

目的观察腹腔镜手术下小儿心率变异性（Heart rate variability，HRV）的变化，为小儿术中及术后心血管的康复提供依据。方法选择ASAⅠ或Ⅱ级择期行腹腔镜手术的患儿20例，全部采用静吸复合全麻，气管内插管，呼吸机行间歇正压通气。分别于麻醉前、气腹前、气腹5min、气腹20min、气腹30min和放气腹5min观察心率变异性指标总功率（TP）、高频功率（HF）、低频功率（LF）、低频标准化值（LFNU）、高频标准化值（HFNU）和低频高频功率比（LF／HF）的变化。结果与气腹前比较，TP、LF、LFNU和LF／HF显著升高（P〈0．01），Hk，无明显变化（P〉0．05）。结论腹腔镜手术气腹后小儿交感神经占优势。HRV可作为麻醉循环监测的敏感指标，动态反映小儿自主神经的变化。     

冠心病患者心率变异性分析

目的了解冠心病（CHD）患者的心率变异性（HRV）特点,探讨CHD患者自主神经变化的临床意义。方法测定93例CHD患者和49例健康对照者24h心率变异性的时域指标,并进行比较分析。结果CHD组24hHRV指标水平明显低于健康对照组（P〈0．01）,差异有统计学意义。结论CHD患者HRV降低提示心血管自主神经系统功能受损害。     

早期糖尿病肾病心率变异性的临床分析

目的探讨早期糖尿病肾病患者心率变异的特点。方法对30例早期2型糖尿病肾病患者和30例无并发症2型糖尿病对照者,进行24h动态心电图监测,对心率变异性参数进行分析比较。结果早期2型糖尿病肾病组的心率变异性参数均显著低于无并发症2型糖尿病对照组(P<0.05)。结论早期糖尿病肾病较无并发症糖尿病患者的自主神经功能损伤更加严重。     

Linear and non-linear heart rate variability measures in chronic and acute phase of anorexia nervosa

Previous results on heart rate variability (HRV) analysis in anorexia nervosa (AN) include some apparently conflicting data. In order to find out the reason for different results and to improve understanding of autonomic control in AN we compare HRV in acute and chronic AN. Spectral powers, fractal scaling exponent and sample entropy were computed from 24 h RR series derived from Holter ECG recordings in 17 anorexic patients, nine chronic and eight healthy women. We found that all linear and non-linear HRV measures change in different direction in acute and chronic AN. Acute AN is characterized by decreased HR and increased HRV. In chronic AN, HR is increased, HRV reduced and the difference between awake and sleeping values is high. HRV measures are associated with body mass index only in chronic AN. As HRV measures are significantly different between acute and chronic AN, we propose that HRV analysis might provide additional data in clinical practice.     

冠状动脉病变与心率变异关系的评价

目的 通过冠状动脉造影和心率变异的测定评价冠状动脉病变与心率变异的关系,预测冠心病的预后。方法 对31例冠心病患者根据冠状动脉病变程度和部位进行分组,并与27例健康人比较。结果 冠状动脉病变组所有指标(时域指标SDNN、SDANN、RMSSD、SDNN Index、PNN_(50)和频域指标TP、VLF、VF、HF)均明显低于健康组(P<0.05～0.01)。冠状动脉病变组时域指标降低尤为显著。冠状动脉双支、三支病变和严重狭窄时域指标(SDNN、PNN_(50)％)和频域指标(LF、HF)均明显低于病变较轻者(P<0.05～0.01)。冠状动脉不同病变部位之间心率变异指标无明显差异。结论 心率变异指标可以反映冠心病的严重程度和预后。     

Reproducibility of abnormal heart rate variability indices: the case of hypertensive sleep apnoea syndrome

Before heart rate variability can be used as an investigational tool in the clinical setting, its reproducibility must be known. We studied heart rate variability four times during 44 weeks in 15 hypertensive patients with sleep apnoea syndrome. Time and frequency domain analytical approaches were used during the spontaneous and controlled breathing tests, orthostatic manoeuvre and the cold pressor test. Alterations in resting heart rate were taken into account using the coefficient of component variance. In general, the response of heart rate variability was abnormal and variability was reduced in the hypertensive patients with sleep apnoea syndrome compared with reference data. Time domain measures of heart rate variability demonstrated generally better reproducibility over four recordings than frequency domain measures in these hypertensive patients with sleep apnoea syndrome. On the other hand, the reproducibility of frequency domain measures depended on the specific conditions: during orthostatic manoeuvre and cold pressor test the best reproducibility was found using normalized units. In the reference data set, there were no significant differences between the two heart rate variability recordings during any of the autonomic nervous function tests. In this follow-up study we found that simple procedures such as the controlled breathing test show good reproducibility. More complex tests such as the orthostatic manoeuvre require special attention in order to obtain acceptable reproducibility of heart rate variability measurements. Quantitatively minor changes in the variability indices when the overall variability is reduced exert major effects on the results. Therefore we suggest that reproducibility data obtained in healthy volunteers are not valid for the interpretation of data in patients with damaged cardiovascular autonomic control.     

Correlation of heart rate recovery and heart rate variability with atrial fibrillation progression

ObjectiveTo examine the combination of heart rate recovery (HRR) and heart rate variability (HRV) in predicting atrial fibrillation (AF) progression.MethodsData from patients with a first detected episode of AF who underwent treadmill exercise testing and 24-h Holter electrocardiography were retrospectively analysed. Autonomic dysfunction was verified using HRR values. Sympathetic and parasympathetic modulation was analysed by HRV. AF progression was defined as transition from the first detected paroxysmal episode to persistent/permanent AF.ResultsOf 306 patients, mean LF/HF ratio and HRR did not differ significantly by AF progression regardless of age (< or ≥65 years). However, when the LF/HF ratio was divided into tertiles, in patients aged <65 years, the mid LF/HF (1.60–2.40) ratio was significantly associated with lower AF progression rates and longer maintenance of normal sinus rhythm. For patients aged <65 years, less metabolic equivalents were related to higher AF progression rates. For patients aged ≥65 years, a low HRR was associated with high AF progression rates.ConclusionIn relatively younger age, high physical capacity and balanced autonomic nervous system regulation are important predictors of AF progression. Evaluation of autonomic function assessed by age could predict AF progression.