Frequency Power Of Heart Rate Variability Research Articles

EEG study on implicit beliefs regarding sexuality: Psychophysiological measures in relation to self-report measures.

In this exploratory, correlational study, several psychophysiological measures were assessed and the relation between these measures and an experimental self-report questionnaire to measure the seven implicit beliefs of sexual offenders (the Questionnaire for Implicit Theories of Sexual Offenders (QITSO)) was established in a sample of Dutch participants recruited from the healthy population (N = 28) using correlational analyses. After analyzing task performance, electroencephalogram (EEG) data and electrocardiogram (ECG) data, the psychophysiological variables were correlated with the experimental QITSO subscales. The subscale “children as sexual beings” correlated positively with the P300 amplitude at electrode Pz. The subscale “women are unknowable” correlated positively with resting-state beta activity during eyes closed and eyes open, and with alpha activity during eyes open. Additionally, the subscale “entitlement’ correlated positively with low frequency heart rate variability power during eyes closed and eyes open, and with high frequency power during eyes closed. This study is a first exploratory step towards establishing a psychophysiological profile underlying the self-report questionnaire QITSO.

Markers of Cardiac Autonomic Function During Consecutive Day Peak Exercise Tests in People With Myalgic Encephalomyelitis/Chronic Fatigue Syndrome.

Patients with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) have been shown to exhibit altered ventilatory characteristics on the second of two progressive maximal cardiopulmonary exercise tests (CPET) performed on consecutive days. However, maximal exercise can exacerbate symptoms for ME/CFS patients and cause significant post-exertional malaise. Assessment of heart rate (HR) parameters known to track post-exertional fatigue may represent more effective physiological markers of the condition and could potentially negate the need for maximal exercise testing. Sixteen ME/CFS patients and 10 healthy controls underwent a sub-maximal warm-up followed by CPET on two consecutive days. Ventilation, ratings of perceived exertion, work rate (WR) and HR parameters were assessed throughout on both days. During sub-maximal warm-up, a time effect was identified for the ratio of low frequency to high frequency power of HR variability (p=0.02) during sub-maximal warm-up, and for HR at ventilatory threshold (p=0.03), with both being higher on Day Two of testing. A significant group (p<0.01) effect was identified for a lower post-exercise HR recovery (HRR) in ME/CFS patients. Receiver operator characteristic curve analysis of HRR revealed an area under the curve of 74.8% (p=0.02) on Day One of testing, with a HRR of 34.5bpm maximising sensitivity (63%) and specificity (40%) suggesting while HRR values are altered in ME/CFS patients, low sensitivity and specificity limit its potential usefulness as a biomarker of the condition.

Early sinusoidal heart rate patterns and heart rate variability to assess hypoxia-ischaemia in near-term fetal sheep.

•Therapeutic hypothermia needs to be started as early as possible in the first 6h after acute injury caused by hypoxia-ischaemia (HI), but the severity and timing of HI are often unclear. In this study we evaluated whether measures of heart rate variability (HRV) might provide early biomarkers of HI. •The duration but not magnitude of suppression of HRV power and conversely increased sample entropy of the heart rate were associated with severity of HI, such that changes in the first 3h did not discriminate between groups. •Relative changes in HRV power bands showed different patterns between groups and therefore may have the potential to evaluate the severity of HI. •Aberrant fetal heart rate patterns and increased arginine vasopressin levels in the first hour after moderate and severe HI were correlated with loss of EEG power after 3days' recovery, suggesting potential utility as early biomarkers of outcome. Therapeutic hypothermia is partially neuroprotective after acute injury caused by hypoxia-ischaemia (HI), likely because the timing and severity of HI are often unclear, making timely recruitment for treatment challenging. We evaluated the utility of changes in heart rate variability (HRV) after HI as biomarkers of the timing and severity of acute HI. Chronically instrumented fetal sheep at 0.85 gestational age were exposed to different durations of umbilical cord occlusion to produce mild (n=6), moderate (n=8) or severe HI (n=8) or to sham occlusion (n=5). Heart rate (HR) and HRV indices were assessed until 72h after HI. All HI groups showed suppressed very low frequency HRV power and elevated sample entropy for the first 3h; more prolonged changes were associated with greater severity of HI. Analysis of relative changes in spectral power showed that the moderate and severe groups showed a shift towards higher HRV frequencies, which was most marked after severe HI. This shift was associated with abnormal rhythmic HR patterns including sinusoidal patterns in the first hour after HI, and with elevated plasma levels of arginine vasopressin, which were correlated with subsequent loss of EEG power by day3. In conclusion, absolute changes in HRV power in the first 3h after acute HI were not significantly related to the severity of HI. The intriguing relative shift in spectral power towards higher frequencies likely reflects greater autonomic dysfunction after severe HI. However, sinusoidal HR patterns and elevated vasopressin levels may have utility as biomarkers of severe HI.

Shift Work and Heart Rate Variability Coherence: Pilot Study Among Nurses

This study used ambient heart rate monitoring among health care workers to determine whether a novel measure of heart rate variability (HRV), as well as sleep disturbances, fatigue, or cognitive performance differed among non-rotating night shift nurses relative to those working permanent day shifts. Continuous ambulatory HRV monitoring was performed among night nurses (n = 11), and a comparison group of permanent day nurses (n = 7), over a 36-h period coinciding with the last two 12-h shifts of each participant’s work week. Symptoms and psychomotor vigilance were assessed at the end of the ambient HRV monitoring period, and no differences between shifts were observed. Day nurses exhibited an increase in hourly mean HRV coherence ratios during their sleep period, suggesting a circadian pattern of cardiorespiratory phase coupling, whereas night nurses had no increase in HRV coherence ratios during their sleep period. The HRV coherence patterns were similar to high frequency HRV power among nurses on the same shift. To the authors knowledge, this study was the first to quantify patterns of the HRV coherence ratio among shiftworkers in a non-experimental (work/home) setting. The results suggest a pattern of autonomic dysregulation among night workers during their sleep period relative to those working day shifts. The HRV coherence ratio may serve as a novel indicator of HRV dysregulation among shift workers.

The Physiological Response to Drawing and Its Relation to Attention and Relaxation

The main purpose of this study was to analyze the physiological response of participants during a creative activity and compare the results to their physiological response during states of high attention and relaxation. Our interest was not only about the relationship between creativity and attention, but also about the role of valence and arousal. We used heart rate variability (HRV) as our physiological measure. We asked twenty-two participants to undertake three activities: a stroop test; a relaxation activity; and a drawing activity. After each activity, the participants were asked to reflect on their levels of attention, relaxation and enjoyment. The results showed significant physiological differences between the three activities: mean heart rate, F(2, 42) = 8.96, p = 0.001; log-transformed low frequency HRV power, F(1.43, 30.07) = 18.12, p < 0.001; and log-transformed high frequency HRV power, F(2, 42) = 6.25, p = 0.004. Overall, the results suggested that participants had high levels of attention during the drawing activity, with positive valence. The results also suggested that participants’ levels of arousal differed between the three activities. The implications of these results are described in the discussion.

The Physiological Response during Divergent Thinking

Our research studied the physiological response of participants during a creative task to investigate if a person’s psychophysiological state was correlated with divergent thinking performance. We used heart rate variability as our physiological measure. We asked 50 participants to perform a cognitive task that assessed their divergent thinking skills and recorded their heart rate and heart rate variability (HRV) before and during the task. Frequency domain analysis was performed on the HRV. The results showed that there was a significant negative correlation between log-transformed low frequency HRV power and the number of “divergent thinking” words generated. Our results suggest that a person’s psychophysiological state is correlated with their divergent thinking performance, and that attention and motivation may be important factors, however this needs further research. Our findings also suggest that being in a relaxed state before the start of a creative task is not a predictor of creative performance.

Orthostatic Stress Induced Changes in Heart Rate Variability, Pulse Transit Time and QRS Duration

Studies have shown the application of non-invasive cardiovascular parameters like heart rate variability (HRV), pulse transit time (PTT) and QRS duration. However no information is available about effects of orthostatic stress on these parameters. Our objective was to study the changes in HRV, PTT and QRS duration caused by orthostatic stress. Electrocardiogram (ECG) and photoplethysmogram (PPG) data was collected from 22 subjects in supine and upright positions. Comparison of parameters in supine and upright positions revealed that every parameter was effected by orthostatic stress. High frequency power of HRV showed the largest response (75%), while QRS duration had the smallest response of (7%). We found that gender played a significant role in PTT, R-R interval and QRS duration values, with male subjects showing higher values of all three parameters. Subject height also played a distinguishing role, with taller subjects showing higher values of R-R interval and PTT. The results allow us to better understand the interaction between various parameters and how they reflect the hemodynamic changes caused by orthostatic stress.

Influence of aerobic training on neurohormonal and hemodynamic responses to head-up tilt test and on autonomic nervous activity at rest and after exercise in patients after bypass surgery

Little is known about the influence of aerobic training on the neurohormonal and hemodynamic responses to head-up tilt (HUT) and on autonomic balance at rest and after exercise in optimally treated, low risk post-coronary artery bypass grafting (CABG) patients. One hundred male patients, mean age 56 ± 6 years, 3 months after CABG, were randomized to either 6-week training on cycloergometer, 3 times a week, at 70-80% of max tolerated heart rate (HR) (training group, n = 50) or to a control group (n = 50). At baseline and at the end of the study, all patients underwent: (1) cardiopulmonary exercise test with HR recovery (HRR) assessment; (2) 60% HUT during which HR, blood pressure (BP), stroke volume (SV by impedance cardiography) were monitored and blood samples were taken for determination of plasma catecholamines and ANP levels, and plasma renin activity; (3) assessment of HR variability (HRV) in the time and frequency domains at rest. During the final tests, HUT-induced changes in HR, BP, SV, cardiac output, total peripheral resistance, and noradrenaline were significantly lower in training group than in controls. In addition, after training faster post-exercise HRR, increased SDNN and a tendency towards an increase in the high frequency HRV power spectrum were found. Aerobic training improved neurohormonal and hemodynamic responses to head-up tilt test and favorably modified sympatho-vagal balance in low risk post-CABG patients.

Fetal autonomic response to severe acidaemia during labour

Spectral analysis of heart-rate variability is used to monitor autonomic nervous system fluctuations. The low-frequency component is associated with sympathetic and parasympathetic modulation and the high-frequency component is associated with parasympathetic modulation. The objective was to study whether changes in low-frequency or high-frequency power of heart-rate variability occur in case of fetal distress. Case-control study. Obstetric unit of a tertiary-care teaching hospital. Twenty healthy human fetuses during labour at term of which ten had an umbilical artery pH < 7.05 (cases), and ten had an arterial pH > 7.20 (controls) after birth. Spectral information about fetal beat-to-beat heart rate, calculated from direct fetal electrocardiogram registrations, was obtained by using a short-time Fourier transform. Absolute power and normalised power in the low-frequency and high-frequency bands. No differences were found between fetuses with and without acidaemia in absolute low or high frequency power (P = 0.2 and P = 0.3, respectively). During the last 30 minutes of labour, acidaemic fetuses had significantly increased normalised low-frequency power (P = 0.01) and decreased normalised high-frequency power (P = 0.03) compared with non-acidaemic fetuses. These differences were not observed from 3 to 2 hours before birth (P = 0.7 and P = 0.9, respectively). The autonomic nervous system of human fetuses at term responds adequately to severe stress during labour. Normalised low and high frequency power of heart-rate variability might be able to discriminate between normal and abnormal fetal condition.

Effect of low-dose endurance training on heart rate variability at rest and during an incremental maximal exercise test

We evaluated the effects of low-dose endurance training on autonomic HR control. We assessed the heart rate variability (HRV) of 11 untrained male subjects (36.8 +/- 7.2 years) at rest and during an incremental maximal aerobic exercise test prior to a 7-week preparatory period and prior to and following a 14-week endurance training period, including a low to high intensity exercise session twice a week. Total (0.04-1.2 Hz), low (0.04-0.15 Hz) and high (0.15-1.2 Hz) frequency power of HRV were computed by short-time Fourier transform. The preparatory period induced no change in aerobic power or HRV. The endurance training period increased peak aerobic power by 12% (P < 0.001), decreased the HR (P < 0.01) and increased all HRV indices (P < 0.05-0.01) at absolute submaximal exercise intensities, but not at rest. In conclusion, low-dose endurance training enhanced vagal control during exercise, but did not alter resting vagal HR control.

Heart rate recovery after exercise is associated with resting QTc interval in young men

Heart rate recovery (HRR) after exercise and spectral decomposition of heart rate variability (HRV), measures of autonomic nervous system function, are predictors of cardiovascular morbidity/mortality. QT interval, an index of ventricular depolarization and repolarization attained from surface ECG, is also associated with morbidity/mortality and is strongly influenced by autonomic tone. The purpose of this study was to assess the association between HRR after exercise, resting HRV and resting rate corrected QT interval in young healthy men. HRR was assessed in 37 men (23.3 +/- 0.6 years) 1 minute after a graded exercise test. Resting QT interval was derived from ECG recordings and rate corrected using five formulae (Bazett, Fridericia, Hodges, Framingham, and the nomogram method of Karjalainen). Resting HRV was spectrally decomposed using an autoregressive approach. A negative correlation was detected for QTc interval and HRR for each method (r = -0.36 to -0.48, P < 0.05). There was no correlation between high frequency power of HRV (a marker of parasympathetic modulation) and QTc interval. There was a negative relationship between absolute LF power (a marker of both sympathetic and parasympathetic modulation) and QTc interval for Karjalainen, Framingham, and Bazett correction methods (r = -0.33 to -0.47, P < 0.05). Resting LF power of HRV and HRR after exercise are inversely associated with resting QTc interval in young healthy men, supporting a relationship between cardiac autonomic nervous system function and ventricular depolarization and repolarization.

La variabilité de la fréquence cardiaque et de la tension artérielle comme indicateurs du bloc sensitif lors de l’analgésie péridurale pour le travail obstétrical

To evaluate the correlation between the progression of somatosensory blockade and changes in autonomic outflow following the onset of labour epidural analgesia. Twelve labouring parturients consented to participate in the study. Baseline electrocardiogram, blood pressure (BP) and respiratory rate were recorded for ten minutes. The epidural consisted of 0.125% bupivacaine with 50 microg of fentanyl (total volume 20 mL). Measurements were repeated for ten minutes after initiation of the block. The level of sensory block was measured bilaterally with loss of sensation to ice at two-minute intervals. Wavelet transform was used to obtain heart rate (HR) and BP variability every two minutes following the loading dose of epidural medication. High frequency power of HR variability was used to assess changes in parasympathetic activity. The total power of BP variability was used to assess changes in sympathetic activity. A nonparametric repeated measures ANOVA was used for the variability data, and a Spearman rank correlation test was used to evaluate the relationship between the sensory block and HR and BP variability. The sensory block progressed to T9 at ten minutes post-epidural and was the mirror image of the decrease in total power of BP variability. High frequency power of HR variability increased to a plateau at six minutes post-epidural. A significant correlation was found between the increase in sensory block and the observed decrease in BP variability (r = -1.000, P = 0.0028). In this study of labouring parturients, BP variability correlated with the progression of both sympathetic and somatosensory block following epidural anesthesia, while HR variability was shown to be a surrogate marker of increased parasympathetic activity.

Altered Autonomic Cardiovascular Regulation After Combined Deep and Superficial Cervical Plexus Blockade for Carotid Endarterectomy

Compromised cardiac autonomic modulation can produce cardiovascular disturbances. We investigated whether combined deep and superficial cervical plexus (CP) blockade for carotid endarterectomy (CEA) produces changes in autonomic cardiovascular regulation. To estimate alterations in cardiovascular autonomic control before and after combined CP blockade in 22 patients undergoing CEA, the heart rate (HR) variability, systolic blood pressure (SBP) variability, and baroreflex sensitivity were analyzed. We found that SBP (157 +/- 28 mm Hg versus 191 +/- 38 mm Hg before and after combined CP blockade, respectively) and HR (68 +/- 10 bpm versus 84 +/- 9 bpm) increased after combined CP blockade. The high frequency power of HR variability (3.7 +/- 0.9 versus 2.2 +/- 1.2 ln/ms2) decreased (decrease in parasympathetic drive), whereas the low frequency power of SBP variability (5.5 +/- 4.7 versus 8.6 +/- 9.4 mm Hg2) increased (increase in vascular sympathetic outflow). Baroreflex sensitivity decreased, and this decrease was negatively correlated with a SBP increase (r = -0.455). The present results suggest that combined CP blockade impairs autonomic cardiovascular homeostasis and suggests an association between combined CP blockade and intraoperative or postoperative adverse cardiovascular events in high-risk cardiac patients undergoing CEA that merits further studies.