Significant Changes In Heart Rate Variability Research Articles

Controlled Exposure to Combined Particles and Ozone Decreases Heart Rate Variability

This experiment was designed to test if controlled exposure to particles and ozone would result in decreased heart rate variability (HRV). Five asthmatic adults were exposed for 4 hours to; filtered-air, carbon and ammonium nitrate particles, and particles and ozone. Twenty-minute electrocardiograms were obtained before and after each exposure. Standard deviation of all normal-to-normal beat intervals (SDNN) decreased significantly across particles and ozone exposure compared with across filtered-air exposure (P = 0.01). Changes in SDNN-I (P = 0.04) and normalized low and high frequency (P = 0.02) were also seen across particles and ozone exposure; although these changes may best be characterized as trends given the small sample size. No significant changes in HRV were seen across the filtered-air or particles-only exposures. The results of this study suggest that combined particle and ozone exposure may decrease HRV in asthmatics. Further investigation is needed to confirm this finding.

The Relationship Between Heart Rate Variability and Epileptiform Activity Among Children—A Controlled Study

Autonomic symptoms frequently occur during epileptic seizures. Attention has been mainly devoted to cardiovascular changes. We studied the relationship between heart rate variability (HRV) and epileptiform activity in children with epilepsy.Simultaneous electroencephalograms and electrocardiograms were recorded in 36 children diagnosed with epilepsy and in 36 children with unrelated conditions who served as a comparison group. Heart rate variability was evaluated by time-domain analysis, before, after, and during an epileptiform event, a benign abnormal event and baseline activity.An age-related change in the HRV associated with an epileptiform event was noted in the study group but not in the comparison group. No other significant differences in HRV were noted between the two groups or between true and benign abnormal events.Age seems to be a significant covariate in the analysis of HRV in children with epilepsy. Epileptiform activity is not associated with a significant change in HRV in children.

Veränderungen der Herzratenvariabilität (HRV) während Low Level Lasernadelakupunktur: Placebokontrollierte Studie an 19 herzgesunden Probanden

Background Experimental and clinical studies postulate a neurobiological mechanism of acupuncture by modulating central pain systems, neurohormones and -transmitters. It seems to be quite likely that the autonomic nervous system (ANS) plays an important mediating role in this neuromodulation. Aim In measuring heart rate variability (HRV), as a non-invasive approach to the ANS-function, the object of this study was to monitor probable acupuncture-induced changes of autonomic balance. The innovative technology of laser-needle acupuncture offers for the first time a stimulation method which fulfils the demands on a placebo-controlled acupuncture trial not requiring controversial sham acupuncture. Method 19 healthy voluntary subjects underwent 3 treatments in randomized sequence, consisting of placebo-, 1-point- (PC 6) and simultaneous 3-point- (PC 6, LR 3, SI 3) laser-needle-stimulation over 20 minutes. Before, during and after placebo-/verum laser-needle acupuncture, HRV-data for normalized HF(high frequency)- and LF(low frequency)-Power (nHF, nLF) and their quotient nLF/nHF obtained by power spectrum analysis (FFT), were measured and analyzed statistically at 5 different time points (ANOVA repeated measures, p < 0,05). Results During both verum applications, the 1-point- (PC 6) as well as the simultaneous 3-point- (PC 6, LR 3, SI 3) laser-needle stimulation, significant changes of the ANS-activity were found in comparison to the placebo application. The most significant modification of HRV was an increase of nHF (p < 0,05 (PC 6), p < 0,0001 (PC 6, LR 3, SI 3)) as an expression of growing vagal activity during acupuncture. Conclusion Laser-needle acupuncture causes in 1-point-stimulation (PC 6) as well as in simultaneous 3-point-stimulation (PC 6, LR 3, SI 3) significant changes in HRV in comparison to placebo application. HRV-monitoring seems to be a suitable approach in exploration of acupuncture-induced changes of ANS and could possibly be established in combination with laser needle acupuncture as a standard for further scientific and clinical acupuncture investigations which are greatly needed.

Finding groups using model-based cluster analysis: Heterogeneous emotional self-regulatory processes and heavy alcohol use risk.

Model-based cluster analysis is a new clustering procedure to investigate population heterogeneity utilizing finite mixture multivariate normal densities. It is an inferentially based, statistically principled procedure that allows comparison of nonnested models using the Bayesian information criterion to compare multiple models and identify the optimum number of clusters. The current study clustered 36 young men and women on the basis of their baseline heart rate and heart rate variability (HRV), chronic alcohol use, and reasons for drinking. Two cluster groups were identified and labeled the high alcohol risk and normative groups. Compared to the normative group, individuals in the high alcohol risk group had higher levels of alcohol use and more strongly endorsed disinhibition and suppression reasons for use. The high alcohol risk group showed significant HRV changes in response to positive and negative emotional and appetitive picture cues, compared to neutral cues. In contrast, the normative group showed a significant HRV change only to negative cues. Findings suggest that individuals with autonomic self-regulatory difficulties may be more susceptible to heavy alcohol use and use of alcohol for emotional regulation.

Evaluation of the Effects of a Training Programme for Patients with Prolonged Fatigue on Physiological Parameters and Fatigue Complaints

Complaints of prolonged fatigue are considered as a major health problem, as it can affect daily functioning and may lead to work disability. To increase knowledge about the effectiveness of interventions focussing on fatigued patients, a study was designed to evaluate an established training programme for patients with prolonged fatigue. Eighteen patients who reported fatigue to be one of their major health complaints and who were suffering from functional impairments attended a training programme of six weeks, three times a week. The training consisted mainly of physical endurance training, relaxation therapy and breathing exercises in rest. At baseline, time- and frequency-domain measures of heart rate variability (HRV) and respiration rate measurements were recorded during rest and during recovery after bicycle exercise. Furthermore, fatigue complaints were assessed with the Checklist Individual Strength (CIS). These measurements were repeated at three weeks and six weeks from baseline. After three weeks, HRV increased significantly in rest--SDNN, i.e. standard deviation of normal beat-to-beat intervals (p = 0.02), very low frequency (p = 0.04) and low frequency (p = 0.04)--and showed a positive trend in the remaining HRV components. No significant HRV changes during recovery were found. Respiration rate decreased significantly after six weeks during rest (from 11.8, SD = 4.65 to 8.1, SD = 2.57 b x min-1) and during recovery (from 15.1, SD = 4.90 to 10.4, SD = 2.97 b x min-1). In all patients, CIS scores decreased after six weeks training (from 106, SD = 13.3 to 78, SD = 21.8, p = 0.001). The results suggest that a six-week training programme has a beneficial effect on physiological and subjective parameters in patients with severe complaints of fatigue.

Altitude, Heart Rate Variability and Aerobic Capacities

We analyzed the relationship between aerobic capacities and changes in heart rate variability (HRV) in Nordic-skiers during living high-training low (Hi-Lo). Eleven skiers trained for 18 days at 1200 m, sleeping at 1200 m (LL, n = 5) or in hypoxic rooms (HL, n = 6, 3 x 6 days at altitudes of 2500 - 3000 - 3500 m, 11 h . day (-1)). Measurements were performed before, during and two weeks after Hi-Lo. VO(2max), peak power output were not improved in HL nor in LL, whereas VO(2) and power at the respiratory compensation point (VO(2RCP) and PRCP) increased by 7.5 % and 5.0 % only in HL. Significant changes in HRV occurred only in LL, in the standing position, including a 30 % (p < 0.05) increase in resting heart rate (HR), a 50 % (p < 0.05) decrease in total spectral power (TP) and a 77 % (p < 0.05) decrease in high frequency activity (HF). When all the subjects were pooled, the changes in HRV in the supine position were correlated to the changes in aerobic capacities, i.e., HF, LF and TP were correlated to VO(2RCP) and HR, HF and TP were correlated to PRCP. This study confirms the relationship between HRV and changes in aerobic capacity, therefore highlighting the potential value of HRV for monitoring altitude training adaptations.

Heart Rate Variability as a Predictor of Negative Mood Symptoms Induced by Exercise Withdrawal

Negative mood symptoms occur frequently in sedentary populations, but individual vulnerability factors for developing these complaints have not been systematically evaluated. This investigation examined whether the autonomic nervous system (ANS) serves a role in the development of negative mood after controlled exercise withdrawal. Forty participants (mean age of 31.3 +/- 7.5 yr, 55% women) who exercised regularly (>or= 30 min of continuous aerobic exercise at least three times a week during the past 6 months) were randomized either to withdrawal from regular aerobic exercise (N=20) or to continue regular aerobic exercise (N=20) for 2 wk. Measurements were taken before exercise withdrawal and at 2-wk follow-up. Various dimensions of negative mood were measured with the multidimensional fatigue inventory, profile of mood states, and Beck depression inventory-II. ANS activity was assessed by heart rate variability (HRV) analyses, examining low-frequency (0.04-0.15 Hz: lf) and high-frequency (hf) domains (0.15-0.40 Hz). The lf/hf ratio was used as index of sympathovagal balance. Protocol adherence was documented by ambulatory activity monitoring. Exercise withdrawal resulted in significantly higher negative mood scores at follow-up compared with control (P<0.05). Baseline lf/hf ratios correlated with the increases in symptoms (r>0.4; P<0.05) in the exercise-withdrawal group independently of gender, age, weight, baseline fitness level, and baseline symptom status. The exercise-withdrawal and control groups displayed no significant change in hf HRV, lf HRV, or lf/hf HRV during the 2 wk. Reduced parasympathetic ANS activity as measured by HRV is predictive of the development of negative mood after deprivation of usual exercise activities. No significant changes in HRV were observed during the 2-wk exercise deprivation period. These findings are relevant to the understanding of mood changes in response to short-term exercise withdrawal, such as sports injuries and recovery from medical procedures.

Heart rate variability in young patients with diabetes mellitus and healthy subjects explored by Poincaré and sequence plots

Autonomic neuropathy is a common complication of the diabetes mellitus (DM). The significance of its early diagnosis is very high because the mortality of the patients with this complication is elevated. Considering the effort to apply new mathematical methods to cardiac dysregulation diagnosis, the major aim of the study was to ascertain which of the new heart rate variability (HRV) parameters are different in young patients with DM type 1 compared with control group. The next aim was to assess the HRV changes during prolonged (40 min) supine rest. The heart rate was continuously recorded during supine rest in 17 young patients with DM type 1 (10 women, 7 men) aged 22.4 +/- 1.0 years (mean +/- SEM). The control group consisted of 17 healthy matched probands. The HRV (time/frequency domains, Poincare and sequence plots, sample entropy) was analysed in two intervals - T1 starting at fifth minute and T2 starting at 30th minute of supine rest. The major results of our study are: the reduced Poincare plot pattern measures in the young DM group; the lower percentage of points in the third quadrant of sequence plot (this parameter was not correlated with the mean heart rate) and significant changes in HRV during supine rest in DM group (in contrast to control subjects). In conclusion, HRV parameters based on nonlinear dynamics were able to distinguish cardiac dysregulation in young patients with DM from the control group. The percentage of points in the third quadrant of sequence plot provides information that is not dependent on mean heart rate. Poincare and sequence plots, together with the rate of HRV changes during supine rest, can provide clinically relevant information usable in diagnosis of the cardiac dysregulation.

Heart rate variability during sedentary work and sleep in normal and sleep‐deprived states

The possibility of using heart rate variability (HRV) as an indicator of sleepiness was investigated by analysing heart rate (HR) activity and electroencephalography (EEG) recordings from 10 individuals who performed a monotonous attention task for 120 min in both sleep-deprived and rested states. In both conditions, measurements were collected during 60 min of sleep immediately following a 120 min of non-sleep (awake phase). Although HR decreased significantly in both the rested and the sleep-deprived states during the awake phase, HR significantly changed sooner when subjects were sleep-deprived than when they were rested. No significant changes in HRV were found during the awake phase; however, HRV correlated significantly with alpha and theta power densities when rested but not when sleep-deprived. During the sleep phase, the total HRV and very low and low frequency HRV components significantly decreased approximately 40 min after sleeping in the sleep-deprived condition. These HRV components were also significantly and negatively correlated with delta power densities. HRV does not seem to be a viable indicator of sleepiness; however, HRV may be useful for determining sleep stages.

Influence of age and moderate-intensity exercise training on heart rate variability in young and mature adults.

The purpose of this study was to examine the influence of age and moderate-intensity exercise training on heart rate variability (HRV), and to elucidate further the mechanism of training-induced bradycardia and cardioprotection. Electrocardiograms were recorded from 12 young (18-24 yrs) and 12 mature (29-43 yrs) individuals during supine rest and submaximal moderate exercise. Recordings were obtained prior to, midway, and following 16 weeks of aerobic exercise training designed to improve cardiorespiratory fitness and health. Training resulted in augmented estimated VO2max and bradycardia during rest and submaximal exercise. Total and low frequency components of HRV during exercise were significantly increased for the mature subjects following training whereas other measures of HRV were not significantly changed for either group. It was concluded that training of moderate intensity was insufficient to induce changes in the autonomic control of heart rate for young to mature subjects. The lack of significant HRV changes may suggest the existence of a vagal critical point, below which training-induced increases in vagal modulation may be forthcoming, and above which changes in vagal modulation may be negligible. Training-induced bradycardia and the cardioprotective effect of regular aerobic exercise may result from factors other than an increased vagal modulation.

Tachycardia induced electrical remodeling of the atria and the autonomic nervous system in goats.

Atrial fibrillation (AF) shortens the atrial effective refractory period (AERP). To investigate the role of the autonomic nervous system during this so-called electrical remodeling of the atria (ERA) and during recovery from ERA we analyzed heart rate variability (HRV). In 12 goats atrioventricular (300:150 beats/min) pacing was performed for 24 hours, interrupted at 4, 8, 16, and 24 hours for recording of 500 atrial (AA) intervals during sinus rhythm and measurement of the AERP(430ms) at 7.4 +/- 0.6 sites. After 24 hours, pacing was stopped and the electrophysiological study and recording of the AA intervals was repeated at 4, 8, 16, and 24 hours after cessation of pacing. Time- and frequency-domain parameters were computed from each 500 AA interval recording. After 24 hours of rapid pacing the AERP had shortened significantly (147 +/- 5.6 to 102+/- 6.4 ms, P < 0.0001). No significant changes in HRV and dispersion of refractoriness (AAERP) (47 +/- 7.1 to 44 +/- 4.2 ms) were observed. After cessation of pacing, the AERP prolonged again (102 +/-6.4 to 135+/-8.8 ms, P < 0.0001) and was paralleled by a significant increase in AAERP (44 +/- 4.2 to 63+/- 7.1 ms, P = 0.01). Furthermore, HRV increased significantly. At each time point an inverse relation between the logarithmically transformed vagal parameter HF (InHF) and AERP was observed. We calculated the mean InHF for each goat using all time points and used the median value to divide the 12 goats into high and low vagal tone groups. We compared the degree of ERA and recovery from ERA for both groups. The AERP shortened 47.4 +/- 6.5 versus 43.0+/-5.0 ms (NS) for goats with high and low vagal tone, respectively. During recovery from ERA the AERP lengthened 23.6 +/- 4.0 versus 42.5 +/- 1.7 ms (P = 0.001) for goats with high and low vagal tone, respectively. Multivariate regression analysis indicated a short AERP as the single independent determinant of the inducibility of AF during ERA and recovery from ERA (P < 0.0001). During recovery from ERA, the AERP prolonged and vagal tone and AAERP increased. A high vagal tone during recovery from ERA was associated with a short AERP and an attenuated recovery of ERA.

Effects of Verapamil on Indexes of Heart Rate Variability After Acute Myocardial Infarction

In patients with previous myocardial infarction (MI), depressed heart rate variability (HRV) may reflect a reduction in vagal activity and lead to cardiac electrical instability. Interventions designed to increase HRV may be of clinical interest. Data on the effects of calcium antagonists on HRV in post-MI patients are very limited. The aim of our study was to assess the effects of verapamil on HRV and on the sympathovagal balance after MI. Fifty consecutive patients with a first MI, stable sinus rhythm, and left ventricular ejection fraction >0.40 were studied. Each patient underwent two 24-hour Holter recordings, 1 at baseline and another after 4 days of treatment with verapamil retard (180 mg 2 times daily). Time and frequency domain parameters of HRV were analyzed. All time domain measurements increased significantly after verapamil: the standard deviation of all NN intervals (SDNN) from 87.1 ± 31.4 to 98.1 ± 30.3 ms (p <0.05) and the log-transformed percentage of pairs of adjacent NN intervals that differ >50 ms (pNN50) from 0.57 ± 0.42 to 0.76 ± 0.45 (p <0.01). The standard deviation of the averages of RR interevals (SDANN) (75.9 ± 30.1 vs 86.3 ± 29.4 ms, p <0.05), root-mean-square of successive differences between RR intervals (rMSSD) (23.0 ± 11.7 and 28.1 ± 13.1 ms, p <0.01), and the triangular HRV index (28.3 ± 9.6 vs 23.4 ± 8.6, p <0.001) also increased. A significant inverse correlation was found between improvement in HRV indexes induced by verapamil and baseline values. Spectral analysis showed a significant increase in high-frequency power of 58.5% without changes in low and very low components. With normalized units, significant reductions in low-frequency power and low- to high-frequency ratio were observed. Diabetic patients did not show any significant changes in HRV on administration of verapamil. These findings indicate that verapamil, administered during the subacute phase of MI, improves both global and short-period indexes of HRV and induces a shift in the sympathetic-parasympathetic interaction toward vagal predominance. This effect may contribute to an explanation of the beneficial effects of verapamil that have been reported in post-MI patients.

Transient autonomic dysfunction precedes ST-segment depression in patients with syndrome X

Increased sympathetic drive has been suggested to play a role in the pathogenesis of syndrome X (angina pectoris, positive exercise testing, and angiographically normal coronary arteries). Heart rate variability (HRV) studies have shown that patients with syndrome X have an imbalance in autonomic nervous system activity (sympathetic predominance). However, it is not known if transient ST-segment depression which occurs in syndrome X during daily activities is related to this autonomic nervous system dysfunction. This study investigates the relation between the response of the autonomic nervous system, as assessed by HRV analysis, and the occurrence of transient ST-segment depression during 24-hour ambulatory electrocardiographic monitoring in 23 patients (4 men and 19 women, mean age 55 ± 6 years) with syndrome X. The frequency-domain variables of HRV low-frequency (0.04 to 0.15 Hz) and high-frequency (0.15 to 0.40 Hz) power were measured at 6-minute intervals during the 30 minutes preceding the onset of transient ST-segment depression. Fourteen patients (61%) had ≥1 episode of ST-segment depression in the 24 hours, whereas the remaining 9 patients (39%) had no significant ST-segment change. HRV measures differed according to whether or not ST-segment depression was associated with increased heart rate. Episodes of ST-segment depression associated with increased heart rate were preceded by a reduction of high-frequency power and an increase in the low-frequency-high-frequency ratio, whereas episodes of ST-segment depression not associated with increased heart rate showed no significant HRV changes. Low-frequency power remained unchanged irrespective of heart rate. Thus, in patients with syndrome X, a sympathovagal imbalance (sympathetic predominance due to vagal tone withdrawal) precedes episodes of ST-segment depression that are associated with an increased heart rate.