老年急性心肌梗塞心率变异时域分析

目的分析急性心肌梗塞（ＡＭＩ）后老年患者心率变异（ＨＲＶ）时域指标，了解ＡＭＩ后ＨＲＶ变化。方法以多单位协作方式对１５７例ＡＭＩ后２周的老年患者行动态心电图检测ＨＲＶ时域法５项指标，并与健康老年组对比分析。数据经ＥｐｉＩｎｆｏ（６．０）统计软件处理。结果①ＡＭＩ患者的正常Ｒ－Ｒ间期标准差（ＳＤＮＮ）、平均值的标准差（ＳＤＡＮＮ）和标准差的平均值（ＳＤＮＮＩｎｄｅｘ）低于对照组（Ｐ＜０．０１），而相邻正常Ｒ－Ｒ间期差值的均方根（ＲＭＳＳＤ）和相邻正常Ｒ－Ｒ差值大于５０ｍｓ记数占总Ｒ－Ｒ间期数的百分比（ＰＮＮ５０）虽低于对照组，但无显著差异（Ｐ＞０．０５）。②ＡＭＩ后ＨＲＶ时域５项指标男、女性别间无显著性差异（Ｐ＞０．０５）。③ＳＤＮＮ、ＳＤＡＮＮ和ＳＤＮＮＩｎ－ｄｅｘ在心肌梗塞各部位间无显著差异（Ｐ＞０．０５），ＲＭＳＳＤ和ＰＮＮ５０前间壁低于下壁心肌梗塞（Ｐ＜０．０５）。结论老年人ＡＭＩ后ＨＲＶ降低。反映交感神经活性的ＳＤＮＮ、ＳＤＡＮＮ和ＳＤＮＮＩｎｄｅｘ和反映迷走神经活性的ＲＭＳＳＤ和ＰＮＮ５０２组指标变化不相同。     

Cigarette Smoking and Heart Rate Variability: Dynamic Influence of Parasympathetic and Sympathetic Maneuvers

Background: Cigarette smoking has been associated with increased activity of the sympathetic nervous system. In this study, we investigated cardiac autonomic function in heavy smokers and nonsmoker controls by analysis of heart rate variability (HRV). Method: Twenty‐four long‐term heavy smokers (men) and twenty‐two nonsmoker subjects (hospital staff) were included to study. Time domain [mean R‐R interval (RR), the standard deviation of R‐R interval index (SDNN), and the root mean square of successive R‐R interval differences (RMSSD)] and frequency domain [high frequency (HF) low frequency (LF), and LF/HF ratio] parameters of HRV were obtained from all participants after 15 minutes resting period in supine position (S), during controlled respiration (CR), and handgrip exercise (HGE) over 5‐minute periods. Results: Baseline SDNN and RMSSD values were found to be lower in smokers than in nonsmokers. (64 ± 10 vs 78 ± 22, P < 0.05 and 35 ± 12 vs 54 ± 30 ms, P < 0.05). Baseline LF/HF ratio was also found to be higher in smokers than in nonsmokers (1.3 ± 0.6 vs 0.9 ± 0.5 ms, P < 0.05). The other HRV parameters including R‐R interval, LF, and HF were not significantly different. During CR, expected increase in RR, SDNN, and RMSSD did not occur in smokers, while it did occur in nonsmokers. Most HRV indices were significantly affected by HGE in both groups. In addition, the duration of smoking was found to be inversely correlated with RMSSD and HF and positively correlated with LF/HF ratio. Conclusion: Vagal modulation of the heart is blunted in heavy smokers, particularly during a parasympathetic maneuver. Blunted autonomic control of the heart may partly be associated with adverse event attributed to cigarette smoking.     

Ethnic differences and heritability of heart rate variability in African- and European American youth

This study investigated whether heart rate variability (HRV) in young African-Americans differed from that in young European Americans. It further examined the genetic and/or environmental sources of HRV variance and to what extent they depend on ethnicity or gender in young twins. Subjects were available from 1 data set including 166 subjects (mean age 16 +/- 2 years; 63 African-Americans) and another including 219 twins (11 singletons [4 African-Americans] and 104 pairs [42 African-Americans]; mean age 15 +/- 2 years). HRV was measured over 256 RR intervals in a supine position. Two time-domain variables, the SD of normal RR intervals (SDNN) and the root-mean-square of successive differences (RMSSD) of normal RR intervals, and 3 frequency-domain variables, high-frequency (HF) power, low-frequency (LF) power, and the LF power/HF power ratio, were used. African-Americans had higher RMSSDs (p <0.01) and HF power (p = 0.047) and lower LF power/HF power ratios (p <0.01) than European Americans. These differences remained significant after adjusting for covariates. All HRV parameters were heritable; estimated heritability ranged from 32% to 71%. Model fitting showed no ethnic or gender differences for any measure. SDNN, RMSSD, and HF power were strongly correlated (r values >0.8). One factor explaining >90% of the variance for all 3 measures was identified. The heritability of this combined HRV score was 70%. In conclusion, this study suggests that ethnic differences in HRV already exist in youth, with African-Americans having greater HRV than European Americans. High heritability estimates for HRV measures were observed, and no differences in HRV heritability estimates were noted for ethnicity or gender.     

Heart rate variability measures during sinus rhythm predict cycle length entropy during atrial fibrillation

Introduction: Several noninvasive measures of cardiac risk such as heart rate variability (HRV) cannot be used in patients with atrial fibrillation (AF). One promising exception is the measure of ventricular cycle length entropy (VCLE) where initial data suggest that a reduction in VCLE portends an increased risk of cardiac death in patients with chronic AF. In this study, we hypothesized that measures of short‐term HRV during sinus rhythm would correlate with measures of cycle length entropy during paroxysms of AF. Methods: We tested 25 Holter recordings of paroxysmal AF from the Physionet AF Prediction Database. We calculated HRV parameters including standard deviation of all NN intervals (SDNN), the root mean square root of the differences between adjacent NN intervals (RMSSD), standard deviation of 5‐minute averages of NN intervals (SDANN), percentage of adjacent NN interval differences >50 ms (pNN50), and interbeat correlation coefficient (ICC) from 30 minutes of normal sinus rhythm, and entropy measures (the Shannon Informational Entropy [ShEn] and Average of Approximate Entropy [ApEn]) from 5 minutes of AF that occurred during the same 24‐hour monitor. Pairwise correlations were used to assess associations, as regression residuals were normally distributed. Results: The mean entropy measures during AF were: ShEn: 4.78 ± 0.82, ApEn: 0.198 ± 0.21. When assessed during the 30 minutes immediately preceding AF onset, ICC showed a significant negative correlation with both ShEn (r =–0.65, P < 0.001) and ApEn (r =–0.60, P < 0.01). RMSSD also correlated with both ShEn (r = 0.41, P = 0.04) and ApEn (r = 0.39, P = 0.05), but other HRV measures showed no correlation with VCLE during AF. Conclusion: Reductions in RMSSD or increases in ICC, two short‐term HRV measures that are known to reflect parasympathetic function in sinus rhythm, are correlated with reductions in the entropy of ventricular response intervals during AF. Our findings suggest that entropy during AF may be modulated, in part, by vagal innervation.     

Evaluating reliability of ultra-short ECG indices of heart rate variability in diabetes mellitus patients

Our aim was to investigate the reliability of ultra-short HRV in patients with DM. A good correlation was found between the 1 minute and 5 minute parameters for maximal-RR, minimal-RR, average-RR, SDNN, RMSSD, pNN50, and total power. Also, a good correlation between 10 second and 5 minute parameters was found for maximal-RR, minimal-RR, average-RR, and RMSSD. We suggest that certain ultra-short HRV parameters can be used efficiently in DM patients for autonomic evaluation.     

The sensitivity of 38 heart rate variability measures to the addition of artifact in human and artificial 24‐hr cardiac recordings

Background

Artifact is common in cardiac RR interval data derived from 24‐hr recordings and has a significant impact on heart rate variability (HRV) measures. However, the relative impact of progressively added artifact on a large group of commonly used HRV measures has not been assessed. This study compared the relative sensitivity of 38 commonly used HRV measures to artifact to determine which measures show the most change with increasing increments of artifact. A secondary aim was to ascertain whether short‐term and long‐term HRV measures, as groups, share similarities in their sensitivity to artifact.

Methods

Up to 10% of artifact was added to 20 artificial RR (ARR) files and 20 human cardiac recordings, which had been assessed for artifact by a cardiac technician. The added artifact simulated deletion of RR intervals and insertion of individual short RR intervals. Thirty‐eight HRV measures were calculated for each file. Regression analysis was used to rank the HRV measures according to their sensitivity to artifact as determined by the magnitude of slope.

Results

RMSSD, SDANN, SDNN, RR triangular index and TINN, normalized power and relative power linear measures, and most nonlinear methods examined are most robust to artifact.

Conclusion

Short‐term time domain HRV measures are more sensitive to added artifact than long‐term measures. Absolute power frequency domain measures across all frequency bands are more sensitive than normalized and relative frequency domain measures. Most nonlinear HRV measures assessed were relatively robust to added artifact, with Poincare plot SD1 being most sensitive.

     

Effects of cigarette smoking on the circadian rhythm of heart rate variability

BACKGROUND: The effects of cigarette smoking on the circadian rhythm of heart rate variability (HRV) are not known. METHODS: We studied the effects of cigarette smoking on the circadian rhythm of HRV in 24 smoking and 21 non-smoking healthy subjects. Twenty-four hour ambulatory electrocardiograms were recorded and time domain parameters of HRV (SDNN [standard deviation of all R-R intervals], SDANN [standard deviation of the averages of R-R intervals in all 5-minute segments of the entire recording], RMSSD [the square root of the mean of the sum of the squares of differences between adjacent R-R intervals]) were determined for the entire 24-hour period and for each 3-hour period. RESULTS: In total, SDNN and SDANN were significantly lower in smokers than non-smokers (116 +/- 26 vs 136 +/- 27, p < 0.05 for SDNN, 109 +/- 25 vs 121 +/- 24, p < 0.05 for SDANN). However, there were no statistical differences between smokers and non-smokers in heart rate (81 +/- 9 vs 76 +/- 10, p > 0.05) and RMSSD (32 +/- 12 vs 37 +/- 18, p > 0.05). These HRV parameters showed a circadian variation: they increased at night and decreased during the day in both groups. The parameters were lower in smokers than non-smokers during daytime (especially, between 8-14 hours). However, no differences were detected during night-time. CONCLUSIONS: Time domain parameters of HRV (SDNN, SDANN and RMSSD) in both smoking and non-smoking healthy subjects have a circadian rhythm. SDNN and SDANN were lower in smokers than non-smokers during daytime.     

Comparison of heart rate variability and treadmill exercise score in patients with stable coronary artery disease

Depressed heart rate variability (HRV) is associated with increased mortality and morbidity with various forms of heart disease, and the Duke treadmill score (DTS) provides diagnostic and prognostic information for the evaluation of patients with coronary artery disease (CAD). Our study was aimed at assessing any possible correlation between HRV and DTS in stable CAD. We evaluated the correlation between the HRV assessed by using 24 hour ambulatory ECG monitoring, and treadmill exercise score in 37 patients with angiographically proven and clinically stable CAD. In univariate analysis, DTS showed a significant negative correlation with age (r=–0.89, p<0.01) and a significant positive correlation with the square root of the mean of the sum of the squares of differences between adjacent R-R intervals (RMSSD) (r=0.67, P<0.05), percent difference between adjacent normal R-R intervals >50 ms (PNN50) (r=0.69, P<0.05), and mean of the standard deviation of all R-R intervals in all the 5-minute intervals (HRVM) (r=0.63, P<0.05). There is no significant correlation between DTS and standard deviation of all R-R intervals (SDNN), standard deviation of the averages of R-R intervals in all 5-minute segments of the entire recordings (SDANN) and standard deviation of the SDNN in all the 5-minute intervals (HRVSD). In multiple regression analysis, age was the only independent significant predictor of DTS (p<0.01). DTS decreased with advancing age. SDNN, SDANN, RMSSD, HRVM and HRVSD were not apparent predictors for detecting of DTS. Age was an independent predictor of DTS. Although DTS was correlated with RMSSD, PNN50 and HRVM in patients with stable CAD, time domain parameters of HRV were not appearent predictor for DTS.     

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.     

Assessing heart rate variability from real-world Holter reports

Real world clinical Holter reports are often difficult to interpret from a heart rate variability(HRV) perspective. In many cases HRV software is absent. Step-by-step HRV assessment from clinicalHolter reports includes: making sure that there is enough usable data, assessing maximum and minimum heart rates,assessing circadian HRV from hourly average heart rates, and assessing HRV from the histogram of R-R intervals andfrom the plot of R-R intervals or heart rate vs. time. If HRV data are available, time domain HRV is easiest tounderstand and less sensitive to scanning errors. SDNN (the standard deviation of all N-N intervals inms) and SDANN (the standard deviation of the 5-min average of N-N intervals in ms) are easilyinterpreted. SDNN < 70 ms post-MI is a cut point for increased mortality risk. Two times ln SDANN is a goodsurrogate for ln ultra low frequency power and can be compared with published cut points. SDNNIDX (theaverage of the standard deviations of N-N intervals for each 5-min in ms) < 30 ms is associated withincreased risk in patients with congestive heart failure. RMSSD (the root mean square of successive N-Ninterval difference in ms) < 17.5 ms has also been associated with increased risk post-myocardialinfarction. Frequency domain HRV values are often not comparable to published data. However, graphical powerspectral plots can provide additional information about whether the HRV pattern is normal and can also identifysome patients with obstructive sleep apnea.     

Exercise training improves heart rate variability in older patients with heart failure: a randomized, controlled, single-blinded trial

Reduced heart rate variability (HRV) in older patients with heart failure (HF) is common and indicates poor prognosis. Exercise training (ET) has been shown to improve HRV in younger patients with HF. However, the effect of ET on HRV in older patients with HF is not known. Sixty-six participants (36% men), aged 69±5 years, with HF and both preserved ejection fraction (HFPEF) and reduced ejection fraction (HFREF), were randomly assigned to 16 weeks of supervised ET (ET group) vs attention-control (AC group). Two HRV parameters (the standard deviation of all normal RR intervals [SDNN] and the root mean square of successive differences in normal RR intervals [RMSSD]) were measured at baseline and after completion of the study. When compared with the AC group, the ET group had a significantly greater increase in both SDNN (15.46±5.02 ms in ET vs 2.37±2.13 ms in AC, P=.016) and RMSSD (17.53±7.83 ms in ET vs 1.69±2.63 ms in AC, P=.003). This increase was seen in both sexes and HF categories. ET improved HRV in older patients with both HFREF and HFPEF.     

Sympathetic Overactivity in Patients with Pulmonary Stenosis and Improvement after Percutaneous Balloon Valvuloplasty

Objective : Percutaneous balloon valvulotomy (PBV) is the procedure of choice for the treatment of valvular pulmonary stenosis (PS) with similar results comparable to surgical valvotomy but less invasive. . Methods and Results : Twenty‐seven consecutive patients with PS being evaluated for PBV were enrolled in the study. Peak instantaneous transvalvular gradient, right ventricle (RV) diameter, mean atrial pressures, RV systolic pressure (RVSP), pro‐brain natriuretic peptide (proBNP) levels significantly decreased immediately after PBV. Regarding heart rate variability (HRV) parameters, mean HR (heart rate), LF (low frequency) day and night, LF/HF day and night significantly decreased and standard deviation of all NN intervals (SDNN), root mean square of successive differences (RMSSD), P number of NN intervals that differed by more than 50 ms from adjacent interval divided by the total number of all NN intervals (PNN50), HF (High frequency) day and night significantly increased 1 day after PBV and these changes were shown to be preserved at the first month. The increase in SDNN was correlated with the decrease in right atrial pressure (RAP) (r =?0.5, P = 0.04); the increase in standard deviation of the 5‐minute mean RR intervals (SDANN) was correlated with the decrease in proBNP (r =?0.4, P = 0.03). Conclusions : Sympathetic overactivity and increased proBNP levels were associated with the symptomatic status of patients with PS. Associated with a decrease in atrial pressures and proBNP levels, PBV yielded a decrease in adrenergic overactivity in the patients with PS.     

Heart rate turbulence and left ventricular ejection fraction in Chagas disease.

AIMS: Chagas disease patients often present premature ventricular complexes (PVCs), depression of left ventricular ejection fraction (LVEF) and autonomic dysfunction, which is generally evaluated by heart rate variability (HRV) analysis. As frequent PVCs may complicate HRV computation, we measured heart rate turbulence (HRT) and evaluated the correlation between ejection fraction and HRT or HRV in Chagas disease. METHODS: We studied 30 patients (47+/-11 years, 20 men) with Chagas cardiomyopathy and left ventricular dilatation who underwent clinical evaluation, ejection fraction (EF: 45+/-14%) determination and 24-h Holter monitoring (median PVC=1781). In all patients, the standard deviation of normal RR intervals (SDNN), the square root of the mean square differences of successive RR intervals (RMSSD) and values of turbulence onset (TO) and turbulence slope (TS) were calculated. RESULTS: HRT indices were independent of mean RR interval and presented high correlation with EF: TO (-0.11+/-0.01%, r=-0.60, P<0.001) and TS (5.8+/-3.7 ms/RR-interval, r=0.73, P<0.001). Of HRV parameters, only SDNN, corrected for mean RR interval, showed a weak but not significant correlation with EF (r=0.41). The comparison of HRT/EF and HRV/EF correlation coefficients, indicated the presence of a significant difference (P=0.017). CONCLUSIONS: HRT indices appear to correlate better with EF than SDNN in Chagas disease. Thus, an analysis based on heart rate transient adaptation seems to perform better than HRV in detecting the autonomic alterations that parallel left ventricular dysfunction in Chagas disease patients. The high number of PVCs observed in these patients further support the use of HRT methodology.     

Can cardiac vagal tone be estimated from the 10-second ECG?

BACKGROUND: Heart rate variability (HRV) recorded over 5 min or 24 h is used increasingly to measure autonomic function and as a prognostic indicator in cardiology. Measuring HRV during a standard 10-s ECG would save time and cut costs. The aim of this study, therefore, was to discover whether indices of HRV calculated over 10 s could predict cardiac vagal tone (CVT) recorded over a 5-min period by the NeuroScope, a new instrument that selectively measures vagal tone. METHODS: A total of 50 subjects had ECGs taken at the beginning, middle and end of a 5-min measurement of CVT. Standard deviation of normal-to-normal RR interval (SDNN), root mean square of successive differences in RR intervals (rMSSD), and the average absolute difference (AAD) in RR intervals were calculated from RR intervals derived from the ECGs. Subjects were divided into a training set (n=40) and a test set (n=10). RESULTS: Regression equations derived from the training set predicted 5-min mean CVT in the test set with r(2) of 95.8%, 92.9% and 87.9% for AAD, rMSSD and SDNN, respectively. Indices obtained from the third ECG in each set tended to give a closer relationship with CVT than those derived from the first and second ECGs: this could be because of the greater spread of the independent variables in the third set. An underlying linear physiological phenomenon could not be excluded, however, without continuing the measurements over a longer time. CONCLUSIONS: These results demonstrate that AAD and rMSSD calculated from a 10-s ECG can accurately predict 5-min mean CVT as measured by the NeuroScope.     

T‐Wave Alternans and Heart Rate Variability: A Comparison in Patients with Myocardial Infarction with or without Diabetes Mellitus

Background : The aim of this study was to investigate the differences in T‐wave alternans (TWA) and heart rate variability (HRV) among patients with myocardial infarction with or without diabetes mellitus and the relationship between TWA and HRV. Methods: The study population included 133 patients: 59 patients with myocardial infarction (MI) (group post‐MI without diabetes); 40 myocardial infarction with diabetes (group post‐MI with diabetes); and 34 controls (group control). Cardiac autonomic neuropathy assessment was made using frequency domain (low‐frequency [LF] power, high‐frequency [HF] power, LF/HF) and time domain (SDNN, standard deviation of the averaged normal sinus RR intervals for all 5‐minute segments [SDANN]) of HRV indexes. Both TWA and HRV were measured on the Holter monitor, and TWA was calculated automatically using the time‐domain modified moving average method. Results: TWA values differed significantly between controls (40 ± 16 μV) and group post‐MI with (62 ± 17 μV, P < 0.05) or without (60 ± 15 μV, P < 0.05) diabetes. In addition, group post‐MI with diabetes had lower standard deviation of all normal sinus RR intervals (SDNN), standard deviation of the averaged normal sinus RR intervals for all 5‐minute segments (SDANN), and HF, indicating depressed vagus nerve activity, and higher LF/HF ratio, indicating elevated sympathetic nerve activity, than controls and group post‐MI without diabetes (P < 0.05). TWA correlated with SDNN and SDANN (r = 0.29, 0.31; P < 0.001). Conclusions: TWA was elevated in patients following myocardial infarction, both in those with or without diabetes. Myocardial infarction patients had a lower time domain, HF, and a higher LF/HF ratio HRV, especially in those with diabetes. The analysis of modified moving agerage (MMA)‐based TWA and HRV can be a useful tool for identifying post–myocardial infarction patients at high risk of arrhythmic events. Ann Noninvasive Electrocardiol 2011;16(3):232–238     

Paper electrocardiograph strips may contain overlooked clinical information in screen-detected type 2 diabetes patients

Background

A large number of nondigitized electrocardiograph (ECG) strips are routinely collected in larger cohort studies such as the ADDITION study (Anglo-Danish-Dutch Study of Intensive Treatment in People with Screen-Detected Diabetes in Primary Care). These ECG strips are routinely read manually but may contain overlooked information revealing cardiac autonomic dysfunction. The aim of this study was to investigate whether clinical information may be lost using manual R wave to R wave (RR) interval measurements in the calculation of heart rate variability (HRV) in patients with type 2 diabetes mellitus (T2DM).

Method

From the Danish part of the ADDITION study, we randomly selected 120 T2DM patients at baseline of the ADDITION study. Analysis of the ECG strips was performed using two different methods: (1) by experienced technicians using rulers and (2) by experienced technicians using a high-resolution computer-assisted method. Calculation of heart rate and time domain HRV [standard deviation of normal-to-normal RR intervals (SDNN) and root mean square of successive differences (RMSSD)] were performed with the same software.

Results

When comparing results from the two methods, the following values of Pearson''s r are obtained: 0.98 for heart rate, 0.76 for SDNN, and 0.68 for RMSSD. These results indicate that heart rate and HRV measurements by the computer-assisted and manually based methods correlate. However, Bland-Altman plots and Pitman''s test of difference in variance revealed poor agreements (p < .01) for both HRV measurements (SDNN and RMSSD); only heart rate showed substantiated agreement (p = .54) between the two methods. Low HRV was statistically significantly associated to high heart rate, systolic blood pressure, and diastolic blood pressure in these screen-detected T2DM patients.

Conclusions

Paper ECG strips may contain overlooked clinical information on the status of autonomic function in patients with T2DM. In our study, manual measurements of RR intervals were inferior to the computer-assisted method. Based on this study, we recommend cautiousness in the clinical use and interpretation of HRV based on manual or low resolution measurements of RR intervals from ECG strips. High resolution measurements of RR intervals reveal significant associations between low HRV and high heart rate, systolic blood pressure, and diastolic blood pressure among patients with screen-detected T2DM. It is feasible to use a computer-assisted method to determine RR intervals in patients with T2DM.     

健康女性人群的心率减速力分析

目的 通过分析不同年龄女性人群心率减速力（DC）的昼夜变化,探讨年龄及昼夜节律对女性DC的影响。方法 339例健康女性按年龄分成4组:18~30岁（青年组）,31~44岁（壮年组）,45~55岁（围绝经期组）,56~70岁（老年组）。各组人群行24 h动态心电图检查,计算机自动测定受捡人群24 h以及白昼（15:00~20:00）和夜间（00:00~05:00）的DC值并进行心率变异性（HRV）分析。结果 随着年龄增长,女性24 h DC、HRV及HR均呈降低趋势;各年龄组女性夜间DC以及RMSSD值均显著高于白天;DC与HR以及SDNN、RMSSD密切相关。结论 健康女性的DC随着年龄增长而下降,且呈昼夜节律变化;DC与HRV密切相关。     

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.     

Heart Rate Variability: Short‐Term Studies are as Useful as Holter to Differentiate Diabetic Patients from Healthy Subjects

Background: The definitive incorporation of heart rate variability (HRV) as a clinical tool depends on the development of more confident techniques of measurement. The length of the studies is a critical issue. Whereas Holter studies allow the monitorization at different hours and activities, short‐term recordings allow the control of environmental conditions. Recording length is also strongly related to the procedure of analysis; for instance, some time‐domain indexes are strongly affected by the duration of the study. Meanwhile, spectral analyses require stationary conditions, only achieved in short‐term studies. Our main goal was to determine if HRV indexes obtained from short‐term analyses were as useful as those from Holter monitoring for diagnosis of reduced HRV in diabetes. Methods: We studied two groups: one with impaired HRV (15 diabetic patients) and another with normal HRV (15 healthy subjects). HRV indexes obtained from 24‐hour Holter recordings (SDNN, rMSSD, and the power of LF and HF bands), were correlated with analog indexes obtained from 10‐minute digital acquired studies within each group. Besides, we compared the diabetic and control groups using the indexes obtained with both methodologies. Results: The correlation was high (0.70≤r ≤ 0.85, P ≤ 0.0032 ) in the diabetic group, but was poor in the control group. HRV values were significantly lower in the diabetic group either for 24‐hour or short‐term studies (P ≤ 0.0113) . Conclusion: We conclude that short‐term studies are at least as powerful as Holter to differentiate the diabetic group (impaired HRV) from the control group.     

Prognostic value of heart rate variability after acute myocardial infarction in the era of immediate reperfusion

Introduction  The incidence and significance of impaired heart rate variability (HRV) after acute myocardial infarction (AMI) have not yet been evaluated in cohorts of patients in whom early reperfusion was systematically attempted. Therefore, HRV was evaluated in 412 unselected patients with AMI (311 men, mean age: 60±12 years, anterior AMI in 172 patients) treated with direct coronary angioplasty (PTCA) within 12 hours of symptom onset (mean 3.5±2.0 h). Standard deviation of normal RR intervals (SDNN), square root of the mean of the sum of the squares of differences between adjacent RR intervals (RMSSD) and left ventricular ejection fraction (LVEF, mean: 55±15%) were measured 11±9 days after AMI before discharge. Angiotensin-converting enzyme (ACE) inhibitors and beta-blockers were prescribed at discharge in 81.1% and 70.1% of patients, respectively. Results  Mean SDNN was 94±30 ms (range 14–155). SDNN was <50 ms in 7% of patients. Mean RMSSD was 34±32 ms (range 2–234). RMSSD was <15 ms in 21% of patients. Low SDNN (<50 ms) was unrelated to gender, age, infarct location or extension of CHD but was related to low LVEF (p<0.001, logistic regression analysis). During mean follow-up of 4.3±3 years, there were 31 deaths; 24 were cardiac. SDNN was higher in long-term survivors (102±39 ms) as compared to nonsurvivors (81±33 ms, p=0.02) but RMSSD was unrelated to the long-term vital status. Four-year survival of patients with a SDNN <50 ms vs >50 ms was 80% vs 92%, respectively (p<0.001, Kaplan Meier analysis). Low SDNN (odds ratio OR=2.0, p<0.05) but not RMSSD was an independent denominator for long-term mortality as were low LVEF (OR=1.0 decrease in LVEF, p<0.01, proportional hazards model) and age (OR=1.1, p<0.001). Only 3/31 fatalities and 1/24 cardiac deaths were predicted by a SDNN <50 ms and only 5/31 fatalities by a RMSSD <15 ms. Conclusion  The incidence of severely depressed HRV in patients after AMI is low (<10%) in the era of early reperfusion of the infarct vessel using direct PTCA. Mortality in patients with a very low HRV when assessed by SDNN is substantial but the positive predictive value of this parameter is low.