Long-term predictive power of heart rate variability on all-cause mortality in the diabetic population

To examine the long-term predictive power of heart rate variability (HRV) on all-cause mortality in randomly selected diabetic individuals. A total of 240 diabetic persons were randomly selected from the diabetic population. A 24-h ECG was obtained for each person included and analysed on the Pathfinder 700. In the RR Tools Program time (SDNN, SDANN, SDNN index, RMSSD, NN50, Triangular index) and frequency domain parameters (total power, VLF, LF, LFnorm, HF, HFnorm, HF/LF) were computed. After 15½ years vital statistics were obtained. The analysis included 165 persons with acceptable ECG recordings. 81 individuals (49%) died during follow-up. Correcting for age and gender we found that in time domain, only the SDNN index was a significant mortality predictor but in the frequency domain, all parameters were significantly associated with death. In multivariate analysis only the power in the low frequency band was an independent predictor. During the period following the first 5 years, the baseline LF continued to be a significant predictor of mortality. This long-term follow-up study indicates that the LF power is the strongest HRV predictor with regard to mortality. A reduced HRV at baseline still holds prognostic information after 5 years.     

Is Baseline Autonomic Tone Associated with New Onset Atrial Fibrillation?: Insights from the Framingham Heart Study

Background: Recent reports have indicated that autonomic tone fluctuations measured by heart rate variability (HRV) precede episodes of paroxysmal atrial fibrillation (AF). Little is known about the impact of baseline autonomic tone and the development of new onset AF in a population‐based cohort. The purpose of this study was to assess the role of HRV as a predictor of new onset AF. Method: Ambulatory ECG recordings obtained from the Framingham Heart Study subjects attending a routine examination were processed for HRV. The HRV variables analyzed included standard deviation of normal R‐R intervals (SDNN), low frequency power (LF), high frequency power (HF), and LF/HF ratio. There were 1434 women and 1142 men (54 ± 14.1 years) eligible for the study. Results: In 12 years of follow‐up, 65 women and 67 men had new onset AF. The study had 80% power to detect a hazard ratio (HR) of 1.3 per standard deviation (SD) decrement in HRV. A one SD decrement in log LF/HF was associated with increased risk of developing AF (HR = 1.23; 95% confidence intervals (CI) = 1.06–1.44) in age‐ and sex‐adjusted models; the association was no longer significant (HR = 1.15; 95% CI = 0.98–1.35) after adjusting for potential confounders. Conclusion: Autonomic dysregulation at baseline, as reflected by an altered HRV is associated with risk of AF; however, this association does not persist after adjusting for potential confounders. Much of the apparent association between HRV and AF is mediated by traditional risk factors.     

Comparison of various methods of assessment of heart rate variability including simple cardiovascular reflex tests as predictors of sudden cardiac death after myocardial infarction.

Long term heart rate variability is used for prediction of sudden cardiac death (SD). There are simpler methods of assessment of autonomic cardiac control - registration of heart rate response to reflex tests and determination of heart rate variability (HRV) on short ECG recordins. Comparative value for prognosis of SD after myocardial infarction (MI) of these 3 techniques has not been studied yet. METHODS: Valsalva maneuver with calculation of Valsalva ratio (VR) and deep breath test with calculation of difference between average maximal and minimal HR during first minute of test (HR difference - HRD) were performed in 188 patients on days 4-11 of MI (68.1% men, age 34-75 years, 93.6% on beta-blockers, without heart failure NYHA IV on the day of tests). Time and frequency domain HRV measures were assessed during 15 min at bed rest and at Holter monitoring for median 24 h on the same day as reflex tests. RESULTS: During follow up for 2.1+/-0.8 years there were 9 sudden and 13 non-sudden cardiac deaths. ROC analysis was used to determine cut-off values of VR, HRD and HRV measures for dichotomization of patients into those with low- and high-risk of SD and these values were used in logistic regression analysis. The following parameters were univariate predictors of SD: obtained at reflex tests - VR <1.13 (OR 7.8, 95% CI 1.6-39.0; p=0.012), HRD <3.36 (OR 4.3, 95% CI 1.1-16.9; p=0.034); HRV parameters from 15 min ECG recordings - total frequency power <739 ms(2), VLF power <294 ms(2), LF power <197 ms(2) and LF/HF <1.5; HRV parameters from long term ECG recording - LF power <491 ms(2), LF/HF <1.4. At multivariate analysis only LF power for 15 min <197 ms(2) among HRV parameters remained independent predictor of SD (OR 24.2, 95% CI 2.4-245.5; p=0.007). Other predictors were clinical - VF during acute phase of MI (OR 94.7, 95% CI 4.2-2115.2; p=0.004) and history of MI (OR 8.4, 95% CI 1.4-48.5; p=0.017). CONCLUSION: In this population of patients without severe heart failure low LF power on 15 min resting ECG recordings on days 4-11 of MI was more powerful predictor of sudden cardiac death during subsequent 2 years than other HRV parameters including heart rate response to Valsalva maneuver and deep breath test.     

Inflammatory markers and heart rate variability in women with coronary heart disease

PURPOSE: Both heart rate variability (HRV) and inflammatory markers are carrying prognostic information in coronary heart disease (CHD), however, we know of no studies examining their relation in CHD. The aim of this study, therefore, was to assess the association between HRV and inflammatory activity, as reflected by the levels of interleukin-6 (IL-6), IL-1 receptor antagonist (IL-1ra) and C-reactive protein (CRP). SUBJECTS AND METHODS: Consecutive women patients who survived hospitalization for acute myocardial infarction, and/or underwent a percutaneous transluminal coronary angioplasty or a coronary artery bypass grafting were included and evaluated in a stable condition 1 year after the index events. An ambulatory 24-h ECG was recorded during normal activities. SDNN index (mean of the standard deviations of all normal to normal intervals for all 5-min segments of the entire recording) and the following frequency domain parameters were assessed: total power, high frequency (HF) power, low frequency (LF) power and very low frequency (VLF) power. Levels of high-sensitivity CRP were measured by nephelometry, IL-6 and IL-1ra concentrations were determined by enzyme immunoassay. RESULTS: Levels of IL-6 showed an inverse relation with HRV measures even after controlling for potential confounding factors. The P-values were 0.02, 0.04, 0.01, 0.03, 0.18 for the multivariate association with SDDN index, total power, VLF power, LF power and HF power respectively. In contrast, the inverse relationship between HRV measures and CRP or IL-1ra levels were weak and nonsignificant. Correlation coefficients for the relationship between IL-6 and HRV measures were both uni- and multivariately higher than for the relationship between HRV measures and any other factors evaluated in this study. CONCLUSION: Concentration of IL-6 showed a negative, independent association with HRV in women with CHD. Thus, increased inflammatory activity, as reflected by IL-6 levels, may represent a new auxiliary mechanism linking decreased HRV to poor prognosis in CHD.     

Sometimes higher heart rate variability is not better heart rate variability: results of graphical and nonlinear analyses

OBJECTIVE: To determine the prevalence and effect on traditional heart rate variability (HRV) indices of abnormal HRV patterns in the elderly. METHODS: Hourly Poincaré plots and plots of spectral HRV from normal-to-normal interbeat intervals and hourly nonlinear HRV values were examined in a subset of 290 consecutive participants in the Cardiovascular Health Study. Only subjects in normal sinus rhythm with > or = 18 hours of usable data were included. Eligible subjects were 71 +/- 5 years. During 7 years of follow-up, 21.7% had died. Hours were scored as normal (0), borderline (0.5), or abnormal (1) from a combination of plot appearance and HRV. Summed scores were normalized to 100% to create an abnormality score (ABN). Short-term HRV versus each 5th percentile of ABN was plotted and a cutpoint for markedly increased HRV identified. The t-tests compared HRV for subjects above and below this cutpoint. Cox regression evaluated the association of ABN and mortality. RESULTS: Of 5,815 eligible hourly plots, 64.4% were normal, 14.5% borderline, and 21.1% abnormal. HR, SDNN, SDNNIDX, ln VLF and LF power, and power law slope did not differ by the cutpoint for increased short-term HRV, while SDANN and ln ULF power were significantly lower for those above the cutpoint. However, many HRV indices including LF/HF ratio and normalized LF and HF power were significantly different between groups (P < 0.001). Increased ABN was significantly associated with mortality (P = 0.019). Despite similar values for many HRV indices, being in the group above the cutpoint was significantly associated with mortality (P = 0.04). CONCLUSIONS: Abnormal HR patterns that elevate many HRV indices are prevalent among the elderly and associated with higher risk of mortality. Consideration of abnormal HRV may improve HRV-based risk stratification.     

The efficacy and prognostic value of heart rate variability in 24-hour and short time recordings for determining cardiac autonomic dysfunction in congestive heart failure]

OBJECTIVE: The heart rate variability (HRV) has been used in patients with heart failure as a non-invasive method and provided neuro-cardiovascular evaluation. This study was planned to determine the efficacy and prognostic value of 24-hour and short time HRV in autonomic dysfunction in patients with congestive heart failure. METHODS: Forty-six patients with symptomatic or asymptomatic left ventricular dysfunction (ejection fraction <40%) were included to the study. In the study group, 16 patients were in NYHA class I (35%), 19 - were in NYHA class II (41%) and 11 - were in NYHA class III (24%). In the first day, HRV was evaluated from the 24-hour Holter recordings. Following day; we assessed the HRV during: (1) 10 min of supine resting, (2) 10 min of regular breathing at a frequency of 20 acts/min, and (3) 10 min of passive orthostatism after tilting 80 degrees with tilt table. RESULTS: Twenty-four hour and short time recordings of HRV showed significant decrease in long-term LF/HF24 (LF- low frequency, HF- high frequency), and short-term LF/HFsupine, LF/HFbreathing and LF/HFtilt ratios in patients with NYHA class III when compared with the patients in NYHA class I-II (p=0.0001, p=0.01, p=0.03, p=0.0001, respectively). During 446+/-186 days of follow-up, cardiovascular end-points occurred in 20 patients. In Cox multivariate analysis, significant predictors of cardiac mortality and morbidity were, reduced LF/HF ratio (HR=0.4, 95% CI 0.31-0.73, p=0.001) in the 24-hour recordings and low left ventricular ejection fraction (HR=0.9, 95% CI 0.83-0.99, p=0.03). CONCLUSION: Our study demonstrated that both of the methods were useful for assessment of cardiac autonomic dysfunction and only 24-hour recordings of HRV had a prognostic value.     

Higher levels of inflammation factors and greater insulin resistance are independently associated with higher heart rate and lower heart rate variability in normoglycemic older individuals: the Cardiovascular Health Study

OBJECTIVES: To explore the relationship between (1) insulin resistance and inflammation factors with (2) higher heart rate (HR) and lower heart rate variability (HRV) in normoglycemic older adults.
DESIGN: Cross-sectional population-based study.
PARTICIPANTS: Five hundred forty-five adults aged 65 and older with normoglycemia (fasting glucose <100 mg/dL) who participated in the Cardiovascular Health Study.
MEASUREMENTS: Serum levels of three inflammation proteins (C-reactive protein (CRP), interleukin 6 (IL-6), and fibrinogen); insulin resistance, quantified according to the homeostasis assessment model (HOMA-IR); HR; and four representative measures of HRV (the standard deviation of normal beat to beat intervals (SDNN), the root mean square of successive differences (rMSSD), very low frequency power (VLF), and the low- to high-frequency power ratio (LF/HF)) derived from 24-hour Holter recordings.
RESULTS: High CRP and IL-6 levels were associated with higher HR and lower SDNN and VLF after adjustment for multiple covariates, including HOMA-IR and clinical cardiovascular disease. High IL-6 was also associated with lower LF/HF. Significant univariate inverse relationships between HOMA-IR and HR and HRV were also found, but the strengths of these relationships were attenuated after adjustment for inflammation factors.
CONCLUSION: Increased levels of inflammation markers and HOMA-IR are associated with higher HR and lower HRV. These findings suggest that inflammation may contribute to the pathogenesis of cardiovascular autonomic decline in older adults.     

冠心病患者窦性心率震荡及T波电交替与心率变异性的相关性分析

目的探讨冠心病患者窦性心率震荡(HRT),心率变异性(HRV)及T波电交替(TWA)变化及相关性。方法冠状动脉造影诊断为冠心病患者(冠心病组)137例,其中陈旧性心肌梗死组50例,稳定性心绞痛组87例;选择同期健康体检者101例为对照组。24h动态心电图检测各组HRT、HRV和TWA参数,进行相关性分析。结果冠心病组与对照组比较,TO值显著增高,TS值显著下降,HRV指标(SDANN,ASDNN,VLF,LF,TP,LF/HF)值显著下降,差异有统计学意义(均P<0.01);最大TWA值增大,在MV5,MV1导联差异有统计学意义(均P<0.01)。陈旧性心肌梗死组与稳定性心绞痛组比较,TS值显著下降,HRV指标(SDANN,ASDNN,VLF、LF、HF、TP)值显著降低,差异有统计学意义(均P<0.05)。TO与SDNN、ASDNN、VLF呈负相关(r=-0.18~-0.19,P<0.05),TS与VLF、LF、HF、TP、SDANN、ASDNN、rMSSD、PNN50呈正相关(r=0.22~0.46,均P<0.01)。结论同时对HRT、HRV及TWA参数比对评估,可提高对冠心病患者危险性评估的准确性和可靠性。     

750例健康儿童心率变异性分析

目的对750例健康儿童心率变异性（heart rate variability,HRV）进行分析,观察正常值范围及HRV与年龄的关系。方法对750例来我院体格检查的正常健康儿童分为以下6个年龄组：新生儿组（〈1个月）、婴儿组（1个月一1岁）、幼儿组（1～3岁）、学龄前组（3～6岁）、学龄组（6—11岁）和青春期组（11—16岁）,进行24h动态心电图检测,分析HRV时域（SDNN、SDANN、PNNSO、rMSSD）及频域（TF、VLF、LF、HF、LF／HF）结果。结果（1）各年龄组HRV时域分析SDNN、SDANN、rMSSD差异有统计学意义（P〈0．05或P〈0．01）,随年龄增长,HRV有增大趋势。（2）HRV频域分析TF、VLF、LF、HF差异有统计学意义（P〈0．01）,数值随年龄增大而增大。结论不同年龄段HRV时域及频域结果不同,HRV随年龄增加而增大,可对临床研究异常HRV提供参考依据。     

Very low frequency power of heart rate variability is a powerful predictor of clinical prognosis in patients with congestive heart failure.

BACKGROUND: The present study examined whether the very low frequency (VLF) power of heart rate variability (HRV) is predictive of clinical prognosis in patients with congestive heart failure (CHF). METHOD AND RESULTS: The study recruited 54 consecutive CHF patients with emergency admission because of exacerbation of pulmonary congestion. Holter monitoring was performed after improvement of pulmonary congestion. The frequency components of HRV were calculated in the frequency domain (VLF, low frequency (LF), high frequency (HF), total power (TP) and the ratio of LF to HF power). The left ventricular ejection fraction was calculated, and plasma brain natriuretic peptide (BNP) and norepinephrine were also measured at discharge. Within a mean follow-up period of 19.8 +/- 11.7 months, 18 patients experienced cardiovascular events; 7 patients died and 11 patients required rehospitalization because of worsening of CHF. In univariate analysis, diabetes mellitus (DM), BNP and New York Heart Association (NYHA) functional class were significant as risk factors for cardiac events. VLF power, LF power and TP were the strong predictors for cardiac events in HRV. In multivariate analysis, VLF power predicted cardiac events independently of LF power, TP, DM, BNP and NYHA functional class (chi-square=6.24, p=0.01). CONCLUSIONS: VLF power is an independent risk predictor in patients with CHF.     

Reproducibility and Gender‐Related Differences of Heart Rate Variability during All‐Day Activity in Young Men and Women

Background : Only few data are available on reproducibility over time in healthy young men and women and the corresponding gender‐related changes of heart rate variability (HRV) measurements. Methods : We studied temporal and spectral HRV indices obtained from 24‐hour Holter recordings in 32 healthy volunteers (14 men and 18 women, mean age 29 ± 3 years) during 2 days of their usual all‐day activity. Results : Time‐domain measures and the spectral low‐frequency (LF) and high‐frequency (HF) components as well as the LF/HF ratio were comparable on both test days. Significantly higher values on test day 2 were observed only for the spectral very‐low‐frequency (VLF) component and for the resulting total power. Compared to men, women had higher day‐ and nighttime vagus‐associated HRV indices, including root mean square of successive differences (RMSSD), pNN50 (NN50 count divided by the total number of all NN intervals), and HF power, and lower day‐ and nighttime VLF and LF power with lower LF/HF ratio and total power. Conclusions : Temporal indices and the LF and HF spectral HRV measures are reproducible over usual all‐day activity in young healthy subjects. Young women have higher day‐and nighttime vagal tone than men with similar age range.     

Do collaterals affect heart rate variability in patients with acute myocardial infarction?

BACKGROUND: The protective effects and the prognostic importance of collaterals during and after acute myocardial infarction (MI) are under debate and heart rate variability (HRV) is a strong predictor of risk of mortality and arrhythmic events after acute MI. We aimed to examine the effects of collateral circulation on HRV in the early period after acute MI. METHODS: Sixty-four patients admitted to our clinics who were diagnosed with acute anterior MI and underwent thrombolytic therapy were enrolled in this study. We applied 24 h Holter monitoring for HRV analysis to all patients and compared the patients with and without collaterals to the infarct-related artery. RESULTS: Mean heart rate, low frequency (LF) (day, night and 24 h) and LF/high frequency (HF) (day, night and 24 h) were higher, SD of all NN intervals (SDNN), root mean square of successive differences (RMSSD), number of NN intervals that differed by more than 50 ms from the adjacent interval divided by the total number of all NN intervals (PNN50) and HF night values were lower in patients without collaterals than in those with collaterals. SDNN was negatively correlated with left anterior descending coronary artery (LAD) stenosis, ventricle score indices and left ventricular ejection fraction (LVEF); LF/HF ratio was positively correlated with ventricle score indices and negatively correlated with LVEF and Thrombolysis in Myocardial Infarction flow grade. Linear regression analysis showed that ventricle score index and coronary collaterals affect HRV and LAD stenosis, ventricle score, LVEF and coronary collaterals affect LF/HF ratio. A SDNN <80 ms increased the development of ventricular arrhythmias in the early period by 4.7 fold, a LF/HF ratio >2.7 increased it by 9.8 fold and a LVEF <35% increased it by 12.8 fold, whereas the presence of well-developed collaterals decreased the arrhythmia development by 2.5 fold. CONCLUSIONS: The collaterals to the infarct-related artery have great impact on HRV, autonomic nervous system activity and the development of ventricular arrhythmias in patients with acute anterior MI. Our results suggest a protective role of collaterals on myocardial electrophysiology in the early period after acute MI.     

Evaluation of Effects of Intra aortic Balloon Counterpulsation on Autonomic Nervous System Functions by Heart Rate Variability Analysis

Background: In patients with acute myocardial infarction (AMI), intraaortic balloon counterpulsation (IABC) may improve cardiac performance, decrease the incidence of recurrent ischemia, and improve survival. Although there have been several reports concerning circulatory maintenance with the IABC, response of the autonomic nervous system to these hemodynamic changes is not clear. Heart rate variability (HRV) analysis has been extensively used to evaluate autonomic modulation of sinus node and to identify patients at risk for an increased cardiac mortality. In this study, we evaluated effects of the IABC on autonomic nervous system functions by HRV analysis. Methods: The study group was composed of 32 consecutive patients (13 female, 19 male aged 61.8 ± 8.8 years) undergoing IABC. Transthoracic echocardiography and 1‐hour Holter recordings for HRV analysis in each IAB pumping mode were obtained. Results: The IABC improved left ventricular diastolic and systolic functions as well as caused an increase in SDNN1, PNN50(1), RMSSD1, and HF1 and a decrease in LF1, LF/HF1, mean heart rate, and the number of ventricular extrasystoles. The improvements in HRV parameters were correlated with some hemodynamic changes such as the increase in MAP and CO during counterpulsation. The only independent factors affecting in‐hospital mortality were the change in LF/HF1 ratio (ΔLF/HF1) and the change in the number of ventricular extrasystole (ΔVES). The decrease in LF/HF1 ≥4.9 decreased the mortality by 1.7‐folds (RR = 0.6, P = 0.04, 95% CI: 0.1–2.3). The decrease in VES ≥27/15 minutes resulted in mortality reduction by 16‐folds (RR = 0.06, P = 0.02, 95% CI: 0.01–0.4). Conclusions: As a result, the IABC, especially in 1:1 support, causes an increase in HRV, decrease in sympathetic overactivity, and improvement in sympathovagal balance besides the favorable hemodynamic changes, and these electrophysiologic changes may explain the role of the IABC in the treatment of ventricular arrhythmias.     

Severity in Myocardial Dysfunction Contributed to Long‐term Fluctuation of Heart Rate,Rather than Short‐Term Fluctuations

Background: It is known that heart rate shows complex behavior, long‐term fluctuation of heart rate, and short‐term fluctuations in heart failure. Analyzing these properties and examining the relationship to the disease, severity may increase the understanding of the background of heart rate variability (HRV). Methods: In 61 patients (mean age 65 ± 9 years , 32 ischemic heart disease, 29 cardiomyopathy), with myocardial dysfunction, 24‐hour ambulatory electrocardiography was performed. After the construction of the time series of R‐R intervals, 15 HRV parameters were measured, including mean heart rate, standard deviation of N‐N intervals (SDNN), ratio of low frequency/high frequency power (LF/HF), HRV triangular index (TI), and ratio of length/width at the 90% level of all scattered points. Results: By using the multiple regression analysis, we tested which HRV parameter (HR, SDNN, LF/HF, TI, or length/width) independently correlated with left ventricular ejection fraction (EF) or left ventricular diastolic dimension (EDD). The results demonstrated that TI and SDNN independently correlated with EF (multiple R = 0.59). Moreover, TI and SDNN independently correlated with EDD (multiple R = 0.45). Conclusion: TI and SDNN were indicators of the disease severity in myocardial dysfunction, while LF/HF, indicators of autonomic tone, did not have such an ability. It was of interest that the disease severity contributed to long‐term fluctuations (TI, SDNN) of heart rate, rather than short‐term fluctuations (LF/HF).     

Heart rate variability in an ageing population and its association with lifestyle and cardiovascular risk factors: results of the SAPALDIA study.

AIMS: (i) To report associations between cardiovascular risk factors and heart rate variability (HRV) in a general population and (ii) to provide normal values for various HRV measurements in a healthy European general population sample aged >or=50. METHODS AND RESULTS: Twenty-four-hour electrocardiograms were recorded in 1742 randomly selected SAPALDIA (Swiss cohort study on Air Pollution and Lung Diseases in Adults) participants aged >or=50. In multivariate regression analyses, women (n=895) had a 6.1% lower standard deviation of all normal RR (NN) intervals (SDNN), a 11.4% lower total power (TP), and a 27.2% lower low-frequency (LF) power than men (n=847). Per unit increase in BMI, SDNN decreased by 0.7% and TP decreased by 1.2%. Persons with high blood pressure had a 9.2% lower LF than normotensive persons and current smokers a 15.5% lower LF than never smokers. Each hour of heavy physical exercise was associated with a 2.0% increase in SDNN, a 3.6% increase in the high frequency (HF) range power and a 4.2% increase in LF power. Higher levels of uric acid, high-sensitive C-reactive protein and non-HDL-cholesterol were associated with lower TP, HF and LF. Percentiles of TP and LF/HF as a function of age were calculated for an asymptomatic subsample of participants (n=499) free of cardioactive medications. CONCLUSION: Heart rate variability in a general population sample shows expected associations with all known cardiovascular risk factors, although not identically for all HRV domains. Together with our percentile estimates for HRV as a function of age, these findings could assist scientists in interpreting 24 h HRV values and factors influencing them in an ageing population.     

Heart rate variability in patients with stable coronary artery disease and aspirin resistance

Aspirin resistance as defined by failure to effectively inhibit thromboxane synthesis is associated with a higher risk of recurrent myocardial ischemia and cardiovascular death. Heart rate variability (HRV) analysis has been extensively used to identify patients at risk for increased cardiac mortality. The aim of this study was to evaluate the association between HRV and aspirin resistance in patients with stable coronary artery disease (CAD). Sixty-nine (69) consecutive patients with stable CAD were included in this study. Of the 69 patients, 18 (26%) were aspirin nonresponders. When the aspirin responders were compared with the nonresponders, there was no significant difference between the groups with respect to most clinical parameters, major cardiovascular risk factors, medical treatments, and aspirin dosages. However, the patients with aspirin resistance had a higher previous myocardial infarction history and lower left ventricular ejection fraction. Moreover, mean platelet volume, CT/EPI, CT/ADP values, LF and LF/HF ratio were higher while HF, SDNN, SDANN, and RMSSD were lower in the nonresponder group than the responders. Regarding HRV parameters, CT/ADP time was negatively correlated with SDNN (r = -0.5, P = 0.02) and HF (r = -0.4, P = 0.03), and positively correlated with LF (r = 0.6, P = 0.01) and LF/HF (r = 0.7, P = 0.001). Similarly, CT/EPI time was negatively correlated with SDNN (r = -0.4, P = 0.03), and positively correlated with LF (r = 0.5, P = 0.02) and the LF/HF ratio (r = 0.5, P = 0.02). Regression analysis revealed that the only parameters affecting SDNN and LF/HF ratio were left ventricle ejection fraction and aspirin resistance. The heart rate variability decreased and sympathetic activity increased in the patients with aspirin resistance and stable CAD. This may contribute to a higher risk of recurrent myocardial ischemia and cardiovascular death in patients with aspirin resistance.     

Prognostic Significance of Heart Rate Variability During the First 24 Hours of Acute Myocardial Infarction: A 5‐Year Follow‐up Study

Background: The prognostic value of heart rate variability (HRV) measured within the first 24 hours of acute myocardial infarction was assessed in 94 consecutive patients. Methods: The mean of standard deviation of normal R‐R intervals for all 5‐minute segments (SDNN index), the width of the R‐R interval histogram at 10% and 50% of the peak, and three frequency‐domain measures of HRV (low frequency [LF], high frequency [HF], and LF/HF ratio) were calculated from a continuous ECG recording taken within the first hours of admission and their prognostic value for long‐term events was studied. Results: During the follow‐up period (56.7 ± 5.9 months) 6 sudden and 7 nonsudden cardiac deaths occurred. Time‐domain measurements of HRV were lower in patients with sudden death (SDNN index: 27.0 ± 20.2 vs 47.5 ± 20.7 ms in survivors, P < 0.001). LF and HF power, but not the LF/HF ratio, were also inversely associated with sudden death. No significant differences were found between survivors and patients with nonsudden cardiac death. After adjustment for other clinical covariates, LF and HF power remained significantly associated with sudden death. Conclusion: We conclude that heart rate variability measured within the first 24 hours of myocardial infarction is a strong predictor of sudden death during subsequent follow‐up.     

阻塞性睡眠呼吸暂停综合征心率变异性的变化及其意义

目的 :研究阻塞性睡眠呼吸暂停综合征 （OSAS）患者心率变异性 （HRV ）的变化。方法 :经夜间多导睡眠图（PSG） 7h监测及动态心电图检查 ,选取重度 OSAS患者及正常受试者各 2 0例 ,采用时域法和频域法分析 HRV。结果 :OSAS组与对照组比较时域指标 SDANN ,SDNN ,r MSSD显著增高 ,SDNN- index则显著降低 ,频域指标VL F,L F,HF,L Fnrom,HFnorm及 L F/HF均较对照组显著增高。结论 :OSAS患者交感神经及副交感神经活动均增强 ,交感神经活动增强占优势     

Association of hyperglycemia with reduced heart rate variability (The Framingham Heart Study)

This study was designed to examine the association of heart rate variability (HRV) with blood glucose levels in a large community-based population. Previous reports have shown HRV to be reduced in diabetics, suggesting the presence of abnormalities in neural regulatory mechanisms. There is scant information about HRV across the spectrum of blood glucose levels in a population-based cohort. One thousand nine hundred nineteen men and women from the Framingham Offspring Study, who underwent ambulatory electrocardiographic recordings at a routine examination, were eligible. HRV variables included the SD of normal RR intervals (SDNN), high-frequency (HF, 0.15 to 0.40 Hz) and low-frequency (LF, 0.04 to 0.15 Hz) power, and LF/HF ratio. Fasting plasma glucose levels were used to classify subjects as normal (<110 mg/dl; n = 1, 779), as having impaired fasting glucose levels (110 to 125 mg/dl; n = 56), and as having diabetes mellitus (DM >/=126 mg/dl or receiving therapy; n = 84). SDNN, LF and HF power, and LF/HF ratio were inversely related to plasma glucose levels (p <0.0001). SDNN and LF and HF powers were reduced in DM subjects (4.28 +/- 0.03, 6.03 +/- 0. 08, and 4.95 +/- 0.09) and in subjects with impaired fasting glucose levels (4.37 +/- 0.04, 6.26 +/- 0.10, and 5.06 +/- 0.11) compared with those with normal fasting glucose (4.51 +/- 0.01, 6.77 +/- 0.02, and 5.55 +/- 0.02, all p <0.005), respectively. After adjusting for covariates (age, sex, heart rate, body mass index, antihypertensive and cardiac medications, systolic and diastolic blood pressures, smoking, and alcohol and coffee consumption), LF power and LF/HF ratio were lower in DM subjects than in those with normal fasting glucose (p <0.005). HRV is inversely associated with plasma glucose levels and is reduced in diabetics as well as in subjects with impaired fasting glucose levels. Additional research is needed to determine if low HRV contributes to the increased cardiovascular morbidity and mortality described in subjects with hyperglycemia.     

Frequency domain measures of heart period variability and mortality after myocardial infarction.

BACKGROUND. We studied 715 patients 2 weeks after myocardial infarction to establish the associations between six frequency domain measures of heart period variability (HPV) and mortality during 4 years of follow-up. METHODS AND RESULTS. Each measure of HPV had a significant and at least moderately strong univariate association with all-cause mortality, cardiac death, and arrhythmic death. Power in the lower-frequency bands--ultra low frequency (ULF) and very low frequency (VLF) power--had stronger associations with all three mortality end points than power in the higher-frequency bands--low frequency (LF) and high frequency (HF) power. The 24-hour total power also had a significant and strong association with all three mortality end points. VLF power was the only variable that was more strongly associated with arrhythmic death than with cardiac death or all-cause mortality. In multivariate Cox regression models using a step-up approach to evaluate the independent associations between frequency domain measures of heart period variability and death of all causes, ULF power was selected first (i.e., was the single component with the strongest association). Adding VLF or LF power to the Cox regression model significantly improved the prediction of outcome. With both ULF and VLF power in the Cox regression model, the addition of the other two components, LF and HF power, singly or together, did not significantly improve the prediction of all-cause mortality. We explored the relation between the heart period variability measures and all-cause mortality, cardiac death, and arrhythmic death before and after adjusting for five previously established postinfarction risk predictors: age, New York Heart Association functional class, rales in the coronary care unit, left ventricular ejection fraction, and ventricular arrhythmias detected in a 24-hour Holter ECG recording. CONCLUSIONS. After adjustment for the five risk predictors, the association between mortality and total, ULF, and VLF power remained significant and strong, whereas LF and HF power were only moderately strongly associated with mortality. The tendency for VLF power to be more strongly associated with arrhythmic death than with all-cause or cardiac death was still evident after adjusting for the five covariates. Adding measures of HPV to previously known predictors of risk after myocardial infarction identifies small subgroups with a 2.5-year mortality risk of approximately 50%.