Heart rate variability analysis in revascularized individuals submitted to an anaerobic potency test

The objective of this study was to analyze the behavior of autonomic modulation before, during and after the Modified Wingate Test (WanMT), through the analysis of Heart Rate Variability (HRV). Six volunteers between the ages of 40 and 70, post-revascularization procedures (angioplasty and/or surgery, mean duration 10 months), were submitted to supervised training for at least 10 to 14 months. The following protocol, divided into 5 phases, was used: 1) Rest Phase (RP): 180 seconds; 2) Submaximum Phase (SP): 30 seconds; 3) Maximum Phase (MP): 30 seconds; 4) Active Recuperation Phase (ARP); 120 seconds and; 5) Passive Recuperation Phase (PRP): 180 seconds. For the WanMT Test, we selected the load of 3.75% of corporal weight for all volunteers. To analyze the HRV, we used the following parameters: the interval RRr, MNN, SDNN, RMSSD and PNN50. We only observed results for the group according to RMSSD parameters during the rest phase of the test protocol in which the group remained in vagal presence and during all other phases in vagal depression. However, when we analyzed the PNN50, we observed that the group was in medium vagal presence during all of the phases of the test though there was no statistically significant difference (p> 0.05) between the phases. Therefore, we can say that all of the individuals had a similar profile in the autonomic response to the WanMT, confirmed by the parameters studied in the analysis of the HRV in the time domain.     

Self-regulation of autonomic homeostasis in emotional stress

Emotional stress is considered to be one of the basic pathogenetic factors causing diseases of the cardiovascular system [1]. Its particular example is the examination stress, which develops in some students expecting an examination. In this case the reactions of the autonomic system in some persons can be oppositely directed and reach a magnitude that puts an organism on the borderline between norm and pathology [2]. There-fore, the qualitative and quantitative estimation of the character of the reaction of the autonomic system to stress in students and the development of the methods of its correction are relevant.     

Heart rate patterns under stress in three species of macaques

Cardiac responses during one hour exposures to three stressful experimental conditions were compared among juvenile females of three species of the genus Macaca (M. mulatta, M. radiata, and M. fascicularis). M. fascicularis showed the highest overall heart rate, and M. mulatta the lowest, in all three conditions. The principal difference between species was in the pattern of change in heart rate over the test sessions. Heart rate declined during the hour for all three species in the first two conditions (home cage novel environment), and the change was most rapid in M. mulatta and slowest in M. fascicularis. In the third and most stressful condition (physical restraint), each species showed a distinct temporal pattern. Heart rate increased over the hour in M. fascicularis, declined in M. radiata, and increased rapidly then declined gradually in M. mulatta. Individual differences in heart rate tended to be consistent within and across conditions. Correlations between behavioral measures of somatic activity and heart rate were generally modest. The results are in accord with other behavioral and physiological differences obtained for the same subjects, and suggest that responses to environmental stimuli reflect fundamental aspects of temperament that may vary substantially even among closely related species. © 1994 Wiley-Liss, Inc.     

Heart rate and heart rate variability in pregnant warmblood and Shetland mares as well as their fetuses

Heart rate (HR) is an important parameter of fetal well-being. In horses, HR and heart rate variability (HRV) can be determined by fetomaternal electrocardiography (ECG) from mid-pregnancy to foaling. Normal values for physiological parameters in larger breeds are often used as reference values in ponies. However, HR increases with decreasing size of the animal and in ponies is higher than in warmblood horses. It is not known if fetal HR is affected by breed and if values obtained in larger breeds can be used to assess Shetland fetuses. We have determined fetomaternal beat-to-beat (RR) interval (inversely correlated to HR) and HRV in warmblood (n=6) and Shetland pregnancies (n=7) at days 280 and 300 of gestation by ECG. Maternal RR interval was lower in pony than in warmblood mares (day 280: Shetland: 958±110, warmblood: 1489±126ms, p<0.01) The SDRR (standard deviation of RR interval) and the RMSSD (root mean square of successive RR differences) did not differ between breeds at any time. Also RR interval as well as HRV did not differ between warmblood and pony fetuses (RR interval day 280: Shetland: 606±39, warmblood: 589±38ms). In conclusion, although maternal RR interval is clearly higher in Shetland than in warmblood mares, fetal RR interval in the two breeds is on the same level.     

Skinfold thickness is related to cardiovascular autonomic control as assessed by heart rate variability and heart rate recovery

The purpose of this study was to determine if heart rate recovery (HRR) and heart rate variability (HRV) are related to maximal aerobic fitness and selected body composition measurements. Fifty men (age = 21.9 ± 3.0 years, height = 180.8 ± 7.2 cm, weight = 80.4 ± 9.1 kg, volunteered to participate in this study. For each subject, body mass index (BMI), waist circumference (WC), and the sum of skinfolds across the chest, abdomen, and thigh regions (SUMSF) were recorded. Heart rate variability (HRV) was assessed during a 5-minute period while the subjects rested in a supine position. The following frequency domain parameters of HRV were recorded: normalized high-frequency power (HFnu), and low-frequency to high-frequency power ratio (LF:HF). To determine maximal aerobic fitness (i.e., VO2max), each subject performed a maximal graded exercise test on a treadmill. Heart rate recovery was recorded 1 (HRR1) and 2 (HRR2) minutes during a cool-down period. Mean VO2max and BMI for all the subjects were 49.5 ± 7.5 ml·kg(-1)·min(-1) and 24.7 ± 2.2 kg·m(-2), respectively. Although VO2max, WC, and SUMSF was each significantly correlated to HRR and HRV, only SUMSF had a significant independent correlation to HRR1, HRR2, HFnu, LF:HF (p < 0.01). The results of the regression procedure showed that SUMSF accounted for the greatest variance in HRR1, HRR2, HFnu, and LF:HF (p < 0.01). The results of this study suggest that cardiovascular autonomic modulation is significantly related to maximal aerobic fitness and body composition. However, SUMSF appears to have the strongest independent relationship with HRR and HRV, compared to other body composition parameters and VO2max.     

Enhanced heart rate variability and baroreflex index after stress and cholinesterase inhibition in mice

Experiments tested the effect of stress coupled with cholinesterase inhibition on blood pressure, heart rate, baroreflex index, and variability in time and frequency domain in conscious mice. The objective was to determine whether cholinergic systems interact with stress to alter cardiovascular responses. Male C57BL/6J mice with arterial catheters were exposed to 3-day treatments: 1) intermittent shaker stress, 2) pyridostigmine (10 mg.kg(-1).day(-1)); or 3) combined pyridostigmine and stress. Pyridostigmine reduced blood cholinesterase (-33%) with no added effects of stress. Twenty-four-hour blood pressure recordings showed that there were no differences in blood pressure and heart rate with the treatments. Pulse interval standard deviation was greatly increased in the pyridostigmine/stress group compared with stress or pyridostigmine groups (11.0 +/- 1.4, 5.0 +/- 0.9, and 7.5 +/- 0.9 ms, respectively). Spectral analysis showed two distinct components for pulse interval variability (low and high frequency). Variability in the low-frequency range was greatly enhanced in the pyridostigmine/stress group, seen as a doubling of the power (9.5 +/- 1.7, 3.3 +/- 0.9, and 5.0 +/- 0.6 ms for pyridostigmine/stress, stress and pyridostigmine groups, respectively). Baroreflex sensitivity was also increased in the pyridostigmine/stress group (3.6 +/- 0.5 compared with 1.8 +/- 0.3 and 1.7 +/- 0.5 ms/mmHg in the stress and pyridostigmine groups, respectively). There was no difference in blood pressure variability or its spectral components. Results demonstrate that there are potent interactions between a mild stressor and cholinesterase inhibition seen as an accentuation of low-frequency variability in pulse interval time series, probably associated with baroreflex input and autonomic drive.     

Heart rate variability in elite American track-and-field athletes

Prolonged training leads to changes in autonomic cardiac balance. This sympathetic and parasympathetic balance can now be studied using heart rate variability (HRV). Studies have shown that endurance athletes have an elevated level of parasympathetic tone in comparison to sedentary people. The effect of resistance training on autonomic tone is less clear. We hypothesized a significant difference in HRV indices in endurance-trained vs. power-trained track-and-field athletes. One hundred forty-five athletes (58 women) were tested prior to the 2004 U.S.A. Olympic Trials. Heart rate variability data were collected using the Omegawave Sport Technology System. Subjects were grouped according to training emphasis and gender. The mean age of the athletes was 24.8 years in each group. There were significant (p < 0.01) differences by sex in selected frequency domain variables (HFnu, LFnu, LH, LHnu) and for PNN50 (p < 0.04) for the time domain variables. Two-factor analyses of variance showed differences for only the main effect of sex and not for any other grouping method or interaction. Elite athletes have been shown to have higher parasympathetic tone than recreational athletes and nonathletes. Our data show differences by sex, but not between aerobically and power-based athletes. Whether this is due to an aerobic component of resistance training, an overall prolonged training effect, or some genetic difference remains unclear. Further study is needed to assess the impact of resistance training programs on autonomic tone and cardiovascular fitness. This information will be valuable for the practitioner to use in assessing an athlete's response to a prescribed training regimen.     

Erythrocyte function of rats under emotional stress

The effect of neurogenic stress of the conflict-of-afferent-excitations-type on the oxidizing erythrocyte properties and qualitative and quantitative red blood changes has been studied. Neurogenic stress was demonstrated to significantly affect the erythrocyte functional state in rats. Activation of free-radical oxidation of erythrocyte membrane lipids took place, provoking changes in their permiability and disorders of oxygen fixation and release. It is suggested that these changes may be the underlying mechanism of the developing tissue hypoxia and play a leading role in the pathogenesis of cardiovascular diseases.     

糖尿病植物神经病变病人心率变异的非线性定量分析

目的：研究糖尿病人植物神经病变与心率变异的关系。对象：正常对照组和根据临床有无糖尿病神经病变（ＤＡＮ）分组的糖尿病病人,方法：应用２４小时动态心电图对正常和糖尿病人进行心率变异的线性,非线性散点图和非线性定量参数分析,结果：单纯糖尿病组ＳＤＮＮ,ＳＤＡＮＮ和ＰＮＮ５０低于正常组（Ｐ〈０．０５）;糖尿病＋ＤＡＮ组各项线性时域分析指标均低于正常和单纯糖尿病组（Ｐ〈０．０１－０．００１）,散点图分析结果     

Effect of emotional stress on the cardiac rhythm variability in rats

A degree of irregularities of the heart rhythm was studied by two methods: chaos-analysis and the HRV (heart rate variability) analysis. Our study shows an individual response in 3 groups of animals: 1--animals with low initial level of chaos (correlation dimension (PD2 < 2); 2--animals with high level of chaos (PD2 > 4); and animals with middle level of chaos (2 < PD2 < 4). The first two groups proved to be more sensitive to stress than the third group. Moreover we found that the electrical stability of the heart as measured by the fibrillation threshold, was higher for the chaos third group. The animals of the first two groups had low cardiac stability and high risk of stress-induced cardiac disturbances.     

Respiratory rhythm of rats under acute emotional stress

Irregularity of the rhythm of breathing, the breathing rate, blood pressure and heart rate were studied in rats under acute emotional stress induced by non-periodic stimulation of the skin and ventromedial hypothalamus. The irregularity of the rhythm of breathing was substantially increased during stimulation of the hypothalamus up to short-term respiratory arrests in animals predisposed to emotional stress. Disturbances of the rhythm of breathing may be one of objective prognostic criteria of the animals' survival or lethality under emotional stress.