Stability over time of short-term heart rate variability

Abstract Heart rate variability (HRV) is a widely used method to assess cardiac autonomic control. However, the reproducibility of especially short-term HRV has not been properly evaluated. Therefore, we assessed the stability of short-term HRV over a three to four month period. We had seven consecutive electrocardiographic (ECG) recordings from 89 subjects with stable coronary artery disease obtained during a large multicenter study. The HRV assessments were performed from these 40-minute ECG-recordings simulating normal daily activities, i. e., recordings consisting of 5 to 10 minute periods of rest, paced breathing, standing, submaximal exercise and recovery. Both time and frequency domain HRV analyses were conducted from the whole 40-minute recordings and from the 5-minute periods of rest and paced breathing. The coefficient of variation (CV) varied between 5.1–16.7% for the 40-minute and 6.0–37.1% for the 5-minute time domain and 4.4–11.0 % for the 40-minute and 7.2–16.5 % for the 5-minute frequency domain measurements. The mean of the RR intervals and the total power showed the highest stability over time. The most unstable measure was the standard deviation of all NN intervals (SDNN). In conclusion, most short-term HRV measures were highly stable over time indicating low physiological variation. However, the SDNN showed large variability in consecutive recordings. Sources of support: EU Environment and Climate Research Program, contract NV4-CT97–0568.     

高血压合并急性脑血管病的心率变异分析

目的：探讨急性脑组织损害对原发性高血压（EH）患者心率变异（HRV）的影响。方法：对26例EH并急性脑血管病（ACVD）患者进行24h动态心电图HRV测定,并与20例EH元ACVD患者进行对比。结果:EH并ACVD组最小心率及平均心率明显高于无ACVD组（P＜0．01;P＜0．01）;24h相邻R-R间期之差的均方根（rMSSD)、相邻R-R间期之差大于50ms的心搏数占心搏总数的百分比（PNN50）较无ACVD组明显减低（P＜0．01;P＜0．001）。结论：EH合并ACVD患者HRV低于EH无ACVD患者,与其自主神经中枢损害有关。     

Twenty-four-hour heart rate variability to assess autonomic function in Parkinson's disease

OBJECTIVES: To evaluate the autonomic dysfunction in Parkinson's disease patients by means of a 24-h heart rate variability (HRV) method. MATERIAL AND METHODS: Thirteen patients with a diagnosis of Parkinson's disease were compared with 13 age-matched healthy persons (control group). The 13 patients had a mean age of 70.5 years, and mean disease duration of 10.9 years. The autonomic function was evaluated by HRV analysis using a continuous 24-h ECG. The parameters of SDNN (standard deviation of the normal-to-normal intervals between adjacent QRS complexes), of LF (power in low frequency) and of HF (power in high frequency) were studied during the following 3 periods: 24 h, night and day. RESULTS: The data show a statistically significant difference between groups for SDNN and LF in all the periods, while for HF parameters the difference is statistically significant only in the night period. CONCLUSION: The use of the 24-h HRV method can provide more accurate and reproducible data than other conventional cardiovascular tests.     

Impaired heart rate variability in euthymic bipolar patients

Background:  Power spectral analysis of heart rate variability (HRV) has recently been shown to be a reliable non-invasive test for quantitative assessment of the central sympathovagal interaction that modulates cardiovascular autonomic function.
Methods:  We studied 39 euthymic bipolar patients and 39 controls, matched for age and sex. A high-resolution electrocardiogram was obtained during complete rest. Spectral analysis of R–R intervals was performed by the fast Fourier transform algorithm.
Results:  Euthymic bipolar patients at rest are characterized by markedly low HRV, independent of specific drug treatments.
Conclusion:  While these results of autonomic stability in euthymic bipolar patients are counter-intuitive, the findings may be important in understanding pathophysiology of bipolar affective illness.     

Orthostatic heart rate variability analysis in idiopathic Parkinson's disease

Objectives –  We evaluated time and spectral analyses of 24-h heart rate variability (HRV) and the heart rate responses to passive tilt in patients with idiopathic Parkinson's disease (IPD) in order to investigate cardiovascular autonomic functions.
Material and methods –  Twenty-three subjects with IPD without autonomic symptoms and 15 age-matched healthy controls were enrolled. Frequency- and time-domain HRV parameters were studied during resting and passive head-up tilt (HUT) test.
Results –  All time-domain parameters were found to be low in patients with IPD. In patients with IPD, both low frequency (LF) and high frequency (HF) decreased during HUT period and no significant change in LF to HF ratio was noted. Both time- and frequency-domain HRV indices showed no correlation with age, disease severity and duration, and with l -dopa medication.
Conclusion –  The results indicate that impairment of autonomic nervous system function in IPD without autonomic symptoms is frequent, and does not show clear association with clinical stage and the age of the patients.     

Effects of caffeine on heart rate and QT variability during sleep

Administration of caffeine in the evening produces poor sleep. Patients with insomnia have characteristic electrocardiogram (ECG) changes, including increased heart rate (HR), increased sympathetic activity, and decreased parasympathetic activity. Fifteen young adult normal subjects slept in the laboratory for several nights prior to randomization into a caffeine protocol where subjects received caffeine 400 mg 30 min prior to one night of sleep and placebo randomly prior to another night. ECG was sampled at a rate of 500 Hz and recorded onto a PC. Data samples of 256-s periods of the ECG trace were taken from wake (before sleep), stage II, and REM for placebo and caffeine conditions. A peak detection algorithm was used to identify the R-R intervals (in milliseconds) from the ECG. A common QT variability algorithm was used to find the QT interval for each beat using the time-stretch model. The powers for HR and QT series were integrated in the bands of LF (low frequency: 0.04-0.15 Hz) and HF (high frequency: 0.15-0.5 Hz) bands. There was a significant caffeine by sleep stage interaction for LF/HF ratios (F = 4.0; df = 2, 18; P = .04). LF/HF ratios were significantly higher during REM following caffeine administration. There was also a significant caffeine by sleep stage interaction for QTvi (QT variability normalized for mean QT interval divided by HR variability normalized for mean HR; F = 5.6; df = 2, 12; P = .02). QTvi was also significantly higher during REM following caffeine administration. The higher LF/HF ratios and QTvi during REM are most likely due to the sympathetic effects of caffeine. These findings suggest that excessive caffeine intake may result in adverse cardiovascular events in vulnerable subjects.     

躯体化症状为主的抑郁症心率变异性对照研究

目的：探讨躯体化症状为主的抑郁症患者自主神经系统的特点及抑郁症躯体化表现的发生机制。方法：对30例躯体化症状为主的患者（A组）和30例情绪症状为主的患者（B组）及30例健康正常者（C组）分别进行汉密尔顿抑郁量表（HAMD）和汉密尔顿焦虑量表（HAMA）评定及短时（10min）心率变异性（HRV）分析。结果：A、B、C3组HRV分析指标RR间期标准差（SDNN）分别为（50.84±19.92）ms、（94.93±28.80）ms、（105.77±22.05）ms,A组显著低于C组（t=5.68,P〈0.01）,较B组低（t=3.73,P〈0.05）;3组LF/HF分别为（6.26±2.11）ms、（3.51±2.44）ms、（1.80±1.07）ms,A组显著高于C组（t=6.35,P〈0.01）,较B组高（t=2.50,P〈0.05）;A组HAMD评分（28.30±6.26）分高于B组（24.35±6.69）分,二者差异有显著性（t=3.14,P〈0.05）;A组HAMA评分（22.70±4.92）分显著高于B组（13.05±4.71）分,二者差异有显著性（t=6.17,P〈0.01）;HAMD焦虑/躯体化因子分与HRV指标SDNN、LF、HF、VLF和LF/HF均呈中度相关（r分别为0.49、0.61、0.58、0.50、0.63）（P〈0.05或P〈0.01）。结论：躯体化症状表现为主的抑郁症患者多伴有焦虑,自主神经功能紊乱。     

癫癎患者发作间期心血管自主神经功能与心率变异性

目的　探讨癫　患者发作间期心血管自主神经功能与心率变异性（ＨＲＶ）的变化。方法　５１例癫　患者根据标准心血管自主神经功能试验结果分为阳性（ＡＮＦＴ＋）组及阴性（ＡＮＦＴ－）组,与正常对照组３６例对比,进行ＨＲＶ分析。结果　癫　患者发作间期心血管自主神经功能异常率为４５．１％,且病程越长异常率越高。癫　患者在ＨＲＶ时域分析及非线性定量分析指标上均较对照组降低,且以　ＡＮＦＴ＋组患者最明显。ＨＲＶ直方图、散点图亦有特征性改变,以ＡＮＦＴ＋组患者最为显著。结论　癫　患者发作间期心血管自主神经功能存在紊乱现象,这种现象可能与癫　患者的猝死发生有关,ＨＲＶ是测定这一变化的敏感方法。     

Reproducibility of heart rate and blood pressure variability in patients with chronic obstructive pulmonary disease

Abstract. Wide variations in respiratory rate and hypoxic stimulation of chemoreceptors may produce unreliable autonomic results in patients with COPD. We studied the reproducibility of two consecutive measurements of heart rate variability (HRV) and blood pressure variability (BPV) by time frequency analysis in patients with COPD while controlling respiratory rate and oxygen hemoglobin saturation (SaO₂). Reproducibility was assessed by paired t-tests and correlation analyses between repeated measures. Correlation analyses of the log transformed low (LF) and high frequency (HF) HRV were 11.5 ± 1.1 in measurement A and 11.5 ± 1.0 in measurement B (r = 0.89, p < 0.0001), and 10.5 ± 1.1 in measurement A and 10.6 ± 1.1 in measurement B (r = 0.89, p < 0.0001) respectively. The log transformed LF and HF BPV were 4.9 ± 1.3 in measurement A and 5.3 ± 0.9 in measurement B (r = 0.70, p < 0.0002), and 6.4 ± 1.3 in measurement A and 6.6 ± 1.2 in measurement B (R = 0.71 p < 0.0001) respectively. In conclusion, time frequency analysis of HRV and BPV is reproducible and reliable in patients with COPD while controlling their respiratory rate and oxygen hemoglobin saturation. Reproducibility of these measurements may allow for a non-invasive evaluation of autonomic tone in response to treatments in COPD patients.     

脑中风患者心率变异的初步分析

目的：探讨中风后植物神经的变化规律及其变化机制。方法：采用反映植物神经功能折心率变异指标，对其时域指标进行分析、应用方差分析及ｔ检验，比较了健康对照组与中风组的心率变异情况。结果：（１）中风组ＳＤＮＮ及ＨＲＶＩ均明显低于健康对照组。（２）中风组随病程的处长，其心率变异逐渐增高，到半年后基本恢复到对照组的水平。     

Accentuated antagonism in the control of human heart rate

Invasive animal models indicate that the accelerative effects of the sympathetic nervous system on heart rate are highly dependent on the background level of vagal activity. A noninvasive, parasympathetic chronotropic index (respiratory sinus arrhythmia) and a sympathetic chronotropic index (left ventricular ejection time) were used to evaluate autonomic control of human heart rate. A strong interaction, previously called accentuated antagonism, was found. Sympathetic heart rate effects were substantially smaller with high levels of vagal tone than with low vagal background activity. Furthermore, vagal effects became progressively stronger with increasing sympathetic background activity, demonstrating the predominance of parasympathetic control of human heart rate. This finding implies that changes in cardiac activity resulting from changes in sympathetic control cannot be interpreted accurately unless concurrent vagal activity is taken into account, as well.     

不同类型痴呆与心率变异性关系的研究

痴呆是老年人的常见病、多发病,是老年人失能和死亡的主要原因,痴呆防治刻不容缓。心率变异性（heart rate variability,HRV）即心率的变化情况,作为一种评估心脏自主神经功能重要且新颖的工具,由于其敏感、直观、便捷等特点,已广泛应用于临床心血管疾病的预后与评估。痴呆与HRV关系密切,不同类型痴呆患者一定程度上都会出现HRV改变,同时,HRV变化可能通过多种机制影响认知障碍的发生和发展。该文总结了不同类型痴呆与HRV关系的研究,以期从预防的角度评估患者HRV的改变,减少认知障碍发生风险,为临床更精确诊断和多靶点防治提供依据。国际神经病学神经外科学杂志, 2023, 50(4): 80-84]     

The relationship between heart rate variability and measures of body habitus

There is a well-recognized relationship between autonomic nervous system function and body habitus although few studies have addressed the role of the parasympathetic nervous system. A decrease in parasympathetic nervous-system-mediated heart rate variability in obesity may in part explain the mortality and morbidity that are associated with the obese state. We used multiple linear regression techniques to explore the relationship between measures of heart rate variability and anthropometric indices in 597 male participants in the Normative Aging Study. After adjustment for age and log₁₀ heart rate, weight and body mass index were significant predictors of both the expiratory to inspiratory ratio (E/I ratio) and the difference between maximum and minimum heart rate (HR_Max-Min). The abdomen-to-hip ratio and percentage body fat were not significant predictors of measures of heart rate variability. A one standard deviation change in the anthropometric index (weight, body mass index) resulted in a decrease in the E/I ratio of 0.010–0.014 and a decrease in the HR_Max-Min of 0.486–0.715 beats/min. A change in the anthropometric index across the distribution (5–95 percentile) resulted in a decrease in the E/I ratio of 0.032–0.037 and a decrease in the HR_Max-Min of 1.56–2.39 beats/min. These results indicate that heart rate variability and overall body size are correlated. This association could in part explain the mortality and morbidity that is associated with the obese state.     

Heart rate variability in patients with untreated Parkinson's disease

The aim of this study was to evaluate cardiovascular responses as a marker of autonomic nervous system (ANS) disturbances in patients with untreated Parkinson's disease (PD) and to assess the relationship between them and the clinical characteristics of PD. The ANS functions were investigated in 50 patients with PD and 55 healthy subjects by measuring standard cardiovascular autonomic reflexes and heart rate variability (HRV) at rest using spectral analysis (the autoregressive model and the fast Fourier transformation), the percentage of the counts of beat-to-beat variation greater than 50 ms and the fractal dimension. Significantly attenuated HRV and deficient blood pressure reaction to tilting were found in the PD patient group. The patients with hypokinesia/rigidity as the initial symptom of PD had a more pronounced HRV deficit than those with tremor onset. Untreated PD patients suffer significant failure in cardiovascular nervous system regulation, and in patients with hypokinesia/rigidity as their initial disease manifestation the risk of this ANS dysfunction is high. However, in the early stages of PD these changes did not reach significance at individual level.     

Reproducibility of heart rate variability and blood pressure variability in individuals with spinal cord injury

Abstract Individuals with spinal cord injury (SCI) are prone to orthostatic intolerance and an increased risk of cardiovascular disease. The use of heart rate variability (HRV) and blood pressure variability (BPV) as indices of cardiovascular regulation would be valuable in this population; however, their reproducibility has yet to be tested in those with SCI. The purpose of this study was to examine the day-to-day reproducibility of resting HRV and BPV in individuals with SCI. Ten individuals (age 35.9±13.2 yrs) with chronic (5.4±7.7 years post injury) SCI (C4-T12; ASIA A-C) participated. On two occasions within a two-week period, 10-minute supine electrocardiogram and Finapres blood pressure recordings were obtained during spontaneous breathing. Computer software calculated frequency domain measures of HRV and BPV (Low frequency (LF) power, High frequency (HF) power, and LF:HF ratio). Intraclass correlations coefficients (R) were used as an index of day-to-day reproducibility, and analyses were conducted on all participants and only those with tetraplegia. For HRV, measures of heart rate, LF, and LF:HF were found to be highly reproducible (R=0.82–0.88); however, the reproducibility of HF was found to be poor (all participants: R=0.53, tetraplegia: R=0.66). Measures of blood pressure as well as systolic BPV also showed high reproducibility (R=0.72–0.93). Measures of diastolic BPV were less reproducible but still acceptable (R=0.71–0.89) with the exception of LF:HF_DBP (R=0.51). In conclusion, despite the autonomic dysfunction associated with SCI, measures of HRV and BPV may still be used as reproducible indices of autonomic cardiovascular regulation in this population.     

Stretching increases heart rate variability in healthy athletes complaining about limited muscular flexibility

Abstract. An increase in muscular flexibility, as well as a significant beneficial effect on heart rate and heart rate variability (HRV), was observed in healthy male athletes after performing a standardized 15-minute stretching-program over a period of 28 days. We believe the HRV increase to be due, at least in part, to the improved vagal and/or diminished sympathetic control. Therefore, we recommend stretching as an effective and gentle technique for health protection.     

Effects of drugs on the autonomic control of short-term heart rate variability

The autonomic nervous system links the brain and the heart. Efferent links in the neural control of the heart consist of sympathetic and parasympathetic (vagal) fibers innervating the sinus node. Because sympathetic and vagal firing alter spontaneous sinus node depolarization, cardiac rate and rhythm convey information about autonomic influences on the heart. The easy availability of ECG rendered possible the assessment of sinus rhythm as an index of autonomic outflow. The frequency-domain approach uses non-invasive recordings and appears to provide a quantitative evaluation of the autonomic modulation of cardiovascular function. Spectral profiles resulting from vagal or sympathetic blockades at the cardiac (or vascular) level might be used as references to unravel the mechanism of action of the drug under examination. A more comprehensive assessment will be obtained if spectral analysis is used as a complement to existing techniques applied for describing the neurohumoral status of patients (microneurographic recordings, norepinephrine spillover). This review also reports some pitfalls encountered in variability studies.