High Frequency Spectral Power Research Articles

Baroreflex sensitivity following acute upper-body exercise in the cold among stable coronary artery disease patients.

Background: A cold environment and exercise separately affect the autonomic nervous system (ANS), baroreflex sensitivity (BRS), and blood pressure variability (BPV) but their combined effects on post-exercise recovery are not known. Our cross-over trial examined these responses following upper-body static and dynamic exercise performed in a cold and neutral environment in patients with coronary artery disease (CAD). Methods: 20 patients with stable coronary artery disease performed both graded static (10%-30% of maximal voluntary contraction) and dynamic (light, moderate and high perceived intensity) upper-body exercise at -15°C and +22°C for 30min. Electrocardiogram and continuous blood pressure were measured to compute post-exercise (10 and 30min after exercise) spectral powers of heart rate (HR), blood pressure variability and BRS at low (0.04-0.15Hz) and high (0.15-0.4Hz) frequencies. Results: Static upper-body exercise performed in a cold environment increased post-exercise high frequency (HF) spectral power of heart rate (HF RR) (p < 0.001) and reduced heart rate (p = 0.001) and low-to-high frequency (LF/HF) ratio (p = 0.006) more than in a neutral environment. In addition, post-exercise mean BRS (p = 0.015) and high frequency BRS (p = 0.041) increased more following static exercise in the cold than in a neutral environment. Dynamic upper-body exercise performed in a cold environment reduced post-exercise HF BRS (p = 0.019) and systolic blood pressure (p = 0.003). Conclusion: Static upper-body exercise in the cold increased post-exercise BRS and overall vagal activity but without reduced systolic blood pressure. Dynamic upper-body exercise in the cold reduced post-exercise vagal BRS but did not affect the other parameters. The influence of cold exposure on post-exercise autonomic and cardiovascular responses following static upper-body exercise require further studies. This information helps understanding why persons with cardiovascular diseases are vulnerable to low environmental temperature. ClinicalTrials.gov: NCT02855905 (04/08/2016).

Predicting sympathovagal balance using parameters of breathing patterns in abdominal breathing

Introduction. Abdominal breathing is utilized as a non-pharmacological treatment method for various stress-related conditions and autonomic dysfunctions. The objective of the study was to determine the predictors in the modulation of sympathovagal balance, as indicated by the ratio of low frequency to high frequency power of heart rate variability, by utilizing the respiratory pattern parameters recorded during the abdominal breathing model. Material and methods. The study involved a group of 101 healthy subjects, where the breathing pattern was recorded using a respiratory induction plethysmograph. Heart activity was estimated through electrocardiography, followed by heart rate variability analysis during both resting and abdominal breathing. Eight parameters of the breathing pattern were recorded in the subjects during resting breathing and abdominal breathing, presumed to be predictors of the ratio of low frequency to high frequency power of heart rate variability. Separate predictive models were created for this ratio for both the resting and abdominal breathing types. Results. The multilinear regression analysis revealed that the primary predictor with the highest predictive power for determining the balance between sympathetic and parasympathetic cardiac influence, as indicated by the low frequency spectral power to high frequency spectral power ratio, in individuals practicing abdominal breathing is Tidal Volume (unstandardized coefficient = 5.007). This was followed by the duration of expiration (coefficient = -3.831) and respiratory minute-volume (coefficient = 4.415), both of which were recorded during resting breathing. In the abdominal breathing model, the most effective predictors were found to be time-related parameters, specifically the frequency of breathing during abdominal breathing (coefficient = -5.953), the duration of the inspiratory phase (coefficient = -4.037), and the duration of the expiration phase (coefficient = -4.194). Conclusions. Abdominal breathing has the potential to normalize sympathovagal balance by adjusting the duration of inspiration or expiration. Further studies should be conducted to investigate the practical application of breathing pattern parameters in restoring the low frequency to high frequency (LF/HF) ratio, particularly in disorders characterized by elevated sympathovagal balance.

Evaluation of an association between maternal prenatal psychological stress and insulin resistance during pregnancy and postpartum

Objectives: Various physiological mechanisms counteract insulin resistance (IR) during normal pregnancy. Psychological stress is a known, independent risk factor for developing IR. Pregnancy-specific psychological stress may cause IR and increase the risk of overt diabetes. Hence, the study aims to evaluate maternal psychological stress using multiple stress markers and their association with changes in IR during pregnancy and postpartum. Materials and Methods: Anthropometric measurements such as height, weight and skinfold thickness were measured using standard techniques. The stress markers were assessed using perceived stress scales (K10 questionnaire), a physiological marker of stress (Heart rate variability [HRV] measures) and biochemical stress markers (Saliva, hair cortisol levels). IR was estimated using homeostasis model assessment-estimated IR (HOMA-IR). The association of stress markers with IR was studied among fifty healthy pregnant women during pregnancy and postpartum. Results: The psychological stress scores and saliva cortisol were significantly higher during pregnancy than postpartum (P = 0.000). A comparison of cardiac autonomic function as assessed by HRV measures shows that high frequency in normalised units (HFnu) was significantly higher during the postnatal period than in the prenatal period (P = 0.000). High frequency (HF) spectral power in absolute units was also significantly higher (P = 0.002) in the postpartum period (2612.30 ± 432.24) when compared with the prenatal period (1446.10 ± 299.15). Low frequency in normalised units (LFnu), low frequency (LF)/HF ratio was significantly higher during the prenatal period than in the postnatal period (P = 0.000). As assessed by HOMA-IR values, IR was significantly higher during the prenatal period than postpartum (P = 0.04). There was a significant positive correlation between prenatal psychological stress scores, HRV parameters (LFnu, LF/HF) and postnatal IR. Conclusion: Pregnancy is associated with higher psychological stress levels and IR than postpartum. Furthermore, the maternal cardiac autonomic marker could predict postnatal IR among healthy pregnant women.

Electromagnetic Fields - Do They Pose a Cardiovascular Risk?

Mobile wireless communication technologies have now become an everyday part of our lives, 24 hours a day, 7 days a week. Monitoring the autonomous system under exposition to electromagnetic fields may play an important role in broading of our still limited knowledge on their effect on human body. Thus, we studied the interaction of the high frequency electromagnetic field (HF EMF) with living body and its effect on the autonomic control of heart rate using Heart Rate Variability (HRV) linear and nonlinear analyses in healthy volunteers. A group of young healthy probands (n=30, age mean: 24.2 ± 3.5 years) without any symptoms of disease was exposed to EMF with f=2400 MHz (Wi Fi), and f=2600 MHz (4G) for 5 minutes applied on the chest area. The short-term heart rate variability (HRV) metrics were used as an indicator of complex cardiac autonomic control. The evaluated HRV parameters: RR interval (ms), high frequency spectral power (HF-HRV in [ln(ms2)]) as an index of cardiovagal control, and a symbolic dynamic index of 0V %, indicating cardiac sympathetic activity. The cardiac-linked parasympathetic index HF-HRV was significantly reduced (p =0.036) and sympathetically mediated HRV index 0V % was significantly higher (p=0.002) during EMF exposure at 2400 MHz (Wi-Fi), compared to simulated 4G frequency 2600 MHz. No significant differences were found in the RR intervals. Our results revealed a shift in cardiac autonomic regulation towards sympathetic overactivity and parasympathetic underactivity indexed by HRV parameters during EMF exposure in young healthy persons. It seems that HF EMF exposure results in abnormal complex cardiac autonomic regulatory integrity which may be associated with higher risk of later cardiovascular complications already in healthy probands.

Effect of high-intensity interval exercise on renal artery hemodynamics in healthy young adults.

High-intensity interval exercise is useful for sustained exercise; however, its effect on renal artery hemodynamics is unclear. This study aimed to evaluate changes in renal artery blood flow velocity due to high-intensity interval exercise. Ten healthy adults (age, 23.5±1.2 years) completed high-intensity interval exercise and moderate-intensity continuous exercise protocols on separate days. The high-intensity interval exercise protocol (total duration, 26 min) comprised eight sets of high-intensity exercise sessions at 85% maximum oxygen uptake for 1 min, with intervals of 40% maximum oxygen uptake for 2 min between sets. The moderate-intensity continuous exercise protocol comprised 40 min of exercise at 40% maximum oxygen uptake. Renal artery blood flow velocity and natural log-transformed high frequency spectral power (an index of cardiac parasympathetic nervous system activity) were measured before and after exercise. Additionally, exercise enjoyment was measured using a questionnaire. Renal artery blood flow velocity did not significantly differ between protocols or timepoints for either protocol. However, the natural log-transformed high frequency spectral power was significantly lower with high-intensity interval exercise than with moderate-intensity continuous exercise (P<0.001, F=25.97) during exercise and at 10 min after exercise, and it did not return to pre-exercise levels with high-intensity interval exercise. Moreover, there was no significant difference in exercise enjoyment between the two protocols. In healthy young adults, high-intensity interval exercise reduces parasympathetic activity; however, it does not produce any significant changes in renal artery hemodynamics after exercise.

Heart Rate Variability Is Not Associated with Altered Emotional Modulation of Pain or Spinal Nociception.

Heart rate variability (HRV) is a physiological measure of beat-to-beat variation in time between heartbeats that reflects competing influences of the sympathetic and parasympathetic branches of the autonomic nervous system (ANS). Research suggests that both ANS branches, and consequently, HRV, are regulated by the central autonomic network (CAN), a widely distributed and interconnected circuit of cortical, limbic, and brainstem areas that modulate ANS activity to meet environmental demands based on current internal physiological conditions. Given its role in modifying internal states, the CAN has been implicated as an important circuit in emotion regulation, and previous researchers have hypothesized that HRV may be a physiological marker related to emotion regulation ability. Indeed, low HRV has been associated with disorders characterized by emotion dysregulation (i.e., depressive and anxiety disorders.) Thus, the current study was conducted to determine whether HRV (calculated using the root mean square of successive differences [RMSSD] and autoregressive high frequency spectral power), divided into tertiles reflecting low, medium, and high levels of HRV, was associated with altered emotional modulation of pain or spinal nociception (assessed from the nociceptive flexion reflex, NFR) during and emotional picture-viewing paradigm known as emotional controls of nociception (ECON). The sample was comprised of 261 healthy, pain-free men and women. It was hypothesized that low HRV would be associated with altered emotional modulation of pain/NFR relative to the other tertile groups for both measures of HRV, with greater facilitation of pain/NFR during negatively valenced pictures and impaired inhibition of pain/NFR during positively valenced pictures. Multilevel modeling analyses revealed that emotional modulation of pain and spinal nociception were not moderated by HRV. Thus, HRV does not appear to promote amplification of pain and nociception via emotional processes, at least not in healthy individuals. These research results were supported by a grant titled, "Native American Pain Disparities: Exploring Nociceptive Processing Differences" (Project Number: 1R01MD007807-01).

Characterizing the effect of incrementally increasing dry bulb temperature on linear and nonlinear measures of heart rate variability in nonpregnant, mid-gestation, and late-gestation sows.

Characterizing the sow physiological response to an increased heat load is essential for effective heat stress mitigation. The study objective was to characterize the effects of a 400-min heating episode on sow heart rate variability (HRV) at different reproductive stages. HRV is a commonly used noninvasive proxy measure of autonomic function. Twenty-seven sows were enrolled in the study according to their gestation stage at time of selection: 1) nonpregnant (NP; n = 7), 2) mid-gestation (MID; 57.3±11.8 d gestation; n = 11), and 3) late-gestation (LATE; 98.8±4.9 d gestation; n = 8). The HRV data utilized in the study were collected from each pig as the dry bulb temperature in the room increased incrementally from 19.84±2.15 °C to 35.54±0.43 °C (range: 17.1-37.5 °C) over a 400-min period. After data collection, one 5-min set of continuous heart rate data were identified per pig for each of nine temperature intervals (19-20.99, 21-22.99, 23-24.99, 25-26.99, 27-28.99, 29-30.99, 31-32.99, 33-34.99, and 35-36.99 °C). Mean inter-beat interval length (RR), standard deviation of r-r intervals (SDNN), root mean square of successive differences (RMSSD), high frequency spectral power (HF), sample entropy (SampEn), short-term detrended fluctuation analysis (DFAα1), and three measures (%REC, DET, LMEAN) derived from recurrence quantification analysis were calculated for each data set. All data were analyzed using the PROC GLIMMIX procedure in SAS 9.4. Overall, LATE sows exhibited lower RR than NP sows (P < 0.01). The standard deviation of r-r intervals and RMSSD differed between each group (P < 0.01), with LATE sows exhibiting the lowest SDNN and RMSSD and NP sows exhibiting the greatest SDNN and RMSSD. Late-gestation sows exhibited lower HF than both MID and NP sows (P < 0.0001), greater DFA values than NP sows (P = 0.05), and greater DET compared to MID sows (P = 0.001). Late-gestation also sows exhibited greater %REC and LMEAN compared to MID (P < 0.01) and NP sows (all P < 0.01). In conclusion, LATE sows exhibited indicators of greater autonomic stress throughout the heating period compared to MID and NP sows. However, temperature by treatment interactions were not detected as dry bulb increased. Future studies are needed to fully elucidate the effect of gestational stage and increasing dry bulb temperature on sow HRV.

Similar Supine Heart Rate Variability Changes During 24-h Exposure to Normobaric vs. Hypobaric Hypoxia.

Purpose: This study aimed to investigate the differences between normobaric (NH) and hypobaric hypoxia (HH) on supine heart rate variability (HRV) during a 24-h exposure. We hypothesized a greater decrease in parasympathetic-related parameters in HH than in NH.Methods: A pooling of original data from forty-one healthy lowland trained men was analyzed. They were exposed to altitude either in NH (FIO2 = 15.7 ± 2.0%; PB = 698 ± 25 mmHg) or HH (FIO2 = 20.9%; PB = 534 ± 42 mmHg) in a randomized order. Pulse oximeter oxygen saturation (SpO2), heart rate (HR), and supine HRV were measured during a 7-min rest period three times: before (in normobaric normoxia, NN), after 12 (H12), and 24 h (H24) of either NH or HH exposure. HRV parameters were analyzed for time- and frequency-domains.Results: SpO2 was lower in both hypoxic conditions than in NN and was higher in NH than HH at H24. Subjects showed similarly higher HR during both hypoxic conditions than in NN. No difference in HRV parameters was found between NH and HH at any time. The natural logarithm of root mean square of the successive differences (LnRMSSD) and the high frequency spectral power (HF), which reflect parasympathetic activity, decreased similarly in NH and HH when compared to NN.Conclusion: Despite SpO2 differences, changes in supine HRV parameters during 24-h exposure were similar between NH and HH conditions indicating a similar decrease in parasympathetic activity. Therefore, HRV can be analyzed similarly in NH and HH conditions.

Heart Rate Variability During a Standard Dive: A Role for Inspired Oxygen Pressure?

Introduction: Heart rate variability (HRV) during underwater diving has been infrequently investigated because of environment limitations and technical challenges. This study aims to analyze HRV changes while diving at variable hyperoxia when using open circuit (OC) air diving apparatus or at constant hyperoxia using a closed-circuit rebreather (CCR). We used HRV analysis in time and frequency domain adding nonlinear analysis which is more adapted to short-time analysis and less dependent on respiratory rate (Sinus respiratory arrhythmia).Materials and Methods: 18 males, 12 using OC (30 mfw for 20 min) and 6 using CCR (30 mfw for 40 min.). HRV was recorded using a polar recorder. Four samples of R-R intervals representing the dive were saved for HRV analysis. Standard deviation of normal-to-normal intervals (SDNN), square root of the mean squared differences between successive RR intervals (rMSSD), and average RR intervals (RR) in time-domain; low frequency (LF) and high frequency (HF) in frequency domain were investigated. Nonlinear analysis included fractal dimension (FrD).Results: SDNN and rMSSD were significantly increased during descent and at depth with OC, not with CCR. Mean RR interval was longer at depth with OC, but only during ascent and after the dive with CCR. HF power was higher than baseline during the descent both with OC and CCR and remained elevated at depth for OC. The LF/HF ratio was significantly lower than baseline for descent and at depth with both OC and CCR. After 30 min of recovery, the LF/HF ratio was higher than baseline with both OC and CCR. Nonlinear analysis detected differences at depth for OC and CCR.Discussion: Increased parasympathetic tone was present during diving. RR duration, SDNN; rMSSD, HF spectral power all increased during the dive above pre-dive levels. Conversely, HF power decreased (and the LF/HF increased) 30 min after the dive. Using FrD, a difference was detected between OC and CCR, which may be related to differences in partial pressure of oxygen breathed during the dive.

Spectral Composition of Body Sway in Persistent Postural-Perceptual Dizziness.

Previous studies in phobic postural vertigo patients showed characteristic frequency changes in body sway fluctuations, raising the question whether similar spectral changes can be also observed in the recently defined syndrome of persistent postural-perceptual dizziness (PPPD). Cross-sectional prospective study. Tertiary referral center. Sixty-one PPPD patients and 41 healthy controls. Static balance was assessed while standing on firm surface with eyes open or closed (conditions 1 and 2) and while standing on foam with eyes open or closed (conditions 3 and 4). Postural sway was analyzed by means of time (sway area and standard deviation) and frequency domain metrics. The latter was based on comparisons of the percentage of energy in each of three frequency bands: low (0-0.5 Hz), middle (0.05-2 Hz), and high frequency (2-20 Hz). Stabilometric time and frequency domain parameters. Time domain metrics deteriorated significantly from conditions 1 through condition 4 in patients and controls. Spectral changes, however, were more abundant in PPPD subjects than in controls. Patients showed increased low frequency, but decreased high frequency spectral power in condition 3 as compared to condition 2. Dizziness Handicap Inventory score was positively correlated with middle frequency and negatively correlated with low frequency fluctuations. We conclude that PPPD patients exhibit a time domain sway pattern in different conditions which is grossly similar to that of controls. However, sensory feedback conditions with equal sway area show unique differences in their spectral content in PPPD patients. Moreover, perceived severity of dizziness is associated with greater body oscillations in the middle frequency band.

Higher energy intake at dinner decreases parasympathetic activity during nighttime sleep in menstruating women: A randomized controlled trial.

Previous studies have found more frequent increases in dietary intake and nonrestorative nocturnal sleep during the luteal phase than in the follicular phase, but few studies have investigated how increased energy intake at dinner influences sleep by considering the correlation between female hormone and cardiac autonomic nervous system (ANS) activity. This study examined the effects of energy intake at dinner on ANS activity during nighttime sleep in order to evaluate restorative sleep in healthy women. We also examined whether ANS activity is associated with female hormone dynamics. Twenty-four healthy collegiate women participated in this randomized crossover trial. Each was assigned to receive a High Energy Dinner (HED) or Low Energy Dinner (LED) treatment. Energy ratios of each test meal (breakfast, lunch, and dinner) to total energy intake were 1:1:2 and 1:2:1 for HED and LED treatments, respectively. Each participant wore an ECG recorder before dinner and removed it upon waking the next morning. Power spectral analysis of heart rate variability was used to calculate low frequency (LF), high frequency (HF), and total spectral power (TP). Cardiac sympathetic (SNS) and parasympathetic (PNS) nervous system activity were evaluated as LF/HF and HF/TP, respectively. Mean HF/TP for the entire sleeping period was lower with HED treatment compared to LED treatment (41.7 ± 11.4 vs. 45.0 ± 12.13, P = .034). Intergroup comparisons of the initial 3-h sleeping period revealed that LF/HF (0.87 ± 0.82 vs. 0.66 ± 0.82, P = .013) and HF/TP (45.6 ± 13.9 vs. 51.5 ± 11.8, P = .002) were higher and lower, respectively, with HED treatment compared to LED treatment. Progesterone levels were positively correlated with LF/HF with LED treatment, and negatively correlated with HF/TP with both HED and LED treatments. Higher energy intake at dinner increases and decreases SNS and PNS activities, respectively, resulting in nonrestorative nocturnal sleep. In addition, a negative correlation was observed between progesterone and PNS activity, highlighting the difficulty of increasing PNS activity during sleep in the luteal phase compared to the follicular phase.

Carbohydrate ingestion induces differential autonomic dysregulation in normal-tension glaucoma and primary open angle glaucoma

BackgroundIt is reported that glaucoma may be associated with vascular dysregulation. Normal tension glaucoma (NTG) and primary open angle glaucoma (POAG), which feature different intraocular pressure levels, may manifest differential features of systemic autonomic dysregulation.Methods and resultsWe investigated autonomic regulation to carbohydrate ingestion and postural change in 37 glaucoma patients (19 NTG and 18 POAG) and 36 controls. Subjects were age and gender-matched, normotensive, and had normal comparable insulin sensitivity. Continuous finger arterial pressure and ECG was recorded in supine and standing positions before and after carbohydrate ingestion. Low frequency (LF, 0.04–0.15Hz) and high frequency (HF, 0.15–0.4Hz) spectral power of heart rate and systolic blood pressure variability (HRV and SBPV) were calculated to estimate sympathovagal function. Overall comparison glaucoma (N = 37) and controls (N = 36) showed an increased sympathetic excitation, vagal withdrawal and unstable mean arterial pressure after carbohydrate ingestion in glaucoma patients. Glaucoma severity by retinal nerve fibre layer (RNFL) thickness is positively correlated to autonomic responses (HRV LF power and HF power in normalised units (nu), and HRV LF/HF ratio) after carbohydrate ingestion. Early (30 minutes) following carbohydrate ingestion, SBP LF power and HRV parameters remained unchanged in controls; while POAG showed abnormal autonomic responses, with a paradoxical vagal enhancement (increased HRV HF power in nu) and sympathetic inhibition (decreased HRV LF power nu and HRV LF/HF ratio), and associated hypotension. Later (60–120 minutes) following carbohydrate ingestion, HRV parameters remained unaltered in controls; whereas NTG manifested vagal withdrawal (reduced HRV HF power nu) and sympathetic hyper-responsiveness (increased HRV LF power nu and HRV LF/HF ratio), despite increased SBP LF power in both controls and NTG. Both NTG and POAG exhibited attenuated autonomic responses to postural stress.ConclusionsNTG and POAG both manifest some systemic autonomic cardiovascular dysregulation. However, the two forms of glaucoma respond differentially to carbohydrate ingestion, irrespective of insulin resistance.

Dissonance-based eating disorder program reduces cardiac risk: A preliminary trial.

We conducted a randomized, controlled preliminary trial to examine the effect of a dissonance-based eating disorder program on eating disorder symptoms and cardiac risk indices in a community sample of women with subclinical and clinical symptoms (N = 47), examining the efficacy of the program in both the indicated prevention and treatment realms. Eating disorder symptoms, body mass index, and biomarkers of cardiac risk were examined in dissonance and assessment-only control conditions at baseline, postintervention, and 2-month follow-up. Specifically, we assessed mean R wave amplitude, QT interval length, vagal tone (high frequency spectral power of heart rate variability), and sympathetic tone (low/high frequency spectral power ratio) via electocardiography (ECG) at each assessment period. We predicted a statistically significant 2 (condition: control, dissonance) × 3 (time: baseline, postintervention, 2-month follow-up) interaction in the mixed factorial MANOVA results. Results confirmed this hypothesis. Eating disorder symptoms and cardiac risk indices decreased significantly among participants in the dissonance condition at postintervention and 2-month follow-up compared with baseline. Results provide support for the efficacy of a dissonance-based program in the reduction of eating disorder symptoms and cardiac risk indices among women with subclinical and clinical eating disorder symptoms. Findings establish the efficaciousness of this dissonance-based approach in the indicated prevention and treatment realms and establish its efficacy in reducing cardiac risk indicators. (PsycINFO Database Record

Cardiac sympathetic index identifies patients with Parkinson's disease and REM behavior disorder

ObjectiveTo compare circadian autonomic fluctuations in patients with Parkinson's Disease (PD) with or without REM sleep behavior disorder (RBD) by using heart rate variability (HRV) analysis. MethodsThis is a case-control study including 20 PD patients with RBD (PD-RBD) and 20 PD patients without RBD (PD). In all patients, we measured the components of HRV in the frequency domain during 24-h with daytime and night time recordings. Selected variables considered were low-frequency (LF) influenced by the sympathetic system and high-frequency (HF) influenced by the parasympathetic system. Moreover, we calculated night-to-day ratio for both LF (cardiac sympathetic index) and HF (cardiac parasympathetic index) spectral components. Video-polysomnography was performed in all patients to diagnose RBD. ResultsBoth nocturnal LF and HF spectral power values were significantly higher in PD-RBD patients than in PD patients (P < 0.001 and P = 0.004 respectively). Moreover, in PD-RBD patients LF and HF values were higher at night than during the day while no difference between night time and daytime values was observed in patients with PD. Cardiac sympathetic index value was significantly higher in PD-RBD patients (median 1.83, range 1.65–3.66) than in PD patients (median 0.93, range 0.44–1.3) without overlap of individual values between groups (accuracy 100%). By contrast, cardiac parasympathetic index had sensitivity of 45% and specificity of 100% for differentiating between PD groups. ConclusionsCardiac sympathetic index distinguishes PD-RBD patients from those with PD on an individual basis, thus representing a valid help in everyday clinical practice for screening of RBD in PD patients.

Oral oestrogen reverses ovariectomy-induced morning surge hypertension in growth-restricted mice.

Perinatal growth restriction (GR) is associated with heightened sympathetic tone and hypertension. We have previously shown that naturally occurring neonatal GR programmes hypertension in male but not female mice. We therefore hypothesized that intact ovarian function or post-ovariectomy (OVX) oestrogen administration protects GR female mice from hypertension. Utilizing a non-interventional model that categorizes mice with weanling weights below the tenth percentile as GR, control and GR adult mice were studied at three distinct time points: baseline, post-OVX and post-OVX with oral oestrogen replacement. OVX elicited hypertension in GR mice that was significantly exacerbated by psychomotor arousal (systolic blood pressure at light to dark transition: control 122 ± 2; GR 119 ± 2; control-OVX 116 ± 3; GR-OVX 126 ± 3 mmHg). Oestrogen partially normalized the rising blood pressure surge seen in GR-OVX mice (23 ± 7% reduction). GR mice had left ventricular hypertrophy, and GR-OVX mice in particular had exaggerated bradycardic responses to sympathetic blockade. For GR mice, a baseline increase in baroreceptor reflex sensitivity and high frequency spectral power support a vagal compensatory mechanism, and that compensation was lost following OVX. For GR mice, the OVX-induced parasympathetic withdrawal was partially restored by oestrogen (40 ± 25% increase in high frequency spectral power, P<0.05). In conclusion, GR alters cardiac morphology and cardiovascular regulation. The haemodynamic consequences of GR are attenuated in ovarian-sufficient or oestrogen-replete females. Further investigations are needed to define the role of hormone replacement therapy targeted towards young women with oestrogen deficiency and additional cardiovascular risk factors, including perinatal GR, cardiac hypertrophy and morning surge hypertension.

Hypothetical Link Between Osteopathic Suboccipital Decompression and Neuroimmunomodulation

Emerging evidence has begun to depict the molecular mechanisms by which inflammation is regulated via the vagus nerve. Specifically, inflammation can be controlled by neuroimmunologic circuitry, dependent upon vagal afferent and efferent fibers, operating in a reflexive continuum. This neuro-immune reflex, known as the inflammatory reflex arc, has some control on serum concentrations of numerous molecular mediators of inflammation such as C-reactive protein and interleukin-6. Importantly, both of these inflammatory proteins are elevated in acute ST-elevation myocardial infarction and are associated with worse cardiac sequelae. Suboccipital decompression by osteopathic manual treatment has been demonstrated to enhance vagal output to the heart, as measured by increased high frequency spectral power of heart rate variability, in a statistically significant manner further supported by a significant decrease in the low-/high frequency spectral power ratio among healthy adults compared to sham treatment and time control. Considering this association, we postulate that suboccipital decompression may stimulate the efferent branch of this vagal-mediated reflex, the cholinergic antiinflammatory pathway, thereby suppressing C-reactive protein and interleukin-6 levels post-ST-elevation myocardial infarction. Furthermore, we provide a detailed clinical study that can determine the validity of our hypothesis.

Effects of Cognitive Behavioral Stress Management on Negative Mood and Cardiac Autonomic Activity in ICD Recipients.

Behavioral intervention studies in patients with an implantable cardioverter-defibrillator (ICD) show promise in improving psychosocial outcomes but inconclusive effects on cardiovascular outcome. We assessed the effects of cognitive behavioral stress management (CBSM) on mood state and potentially arrhythmogenic cardiovascular responses to mental stress in ICD patients, in support of further larger scale arrhythmia trials. A total of 103 ICD recipients were randomly assigned to 10-week programs of CBSM or "Patient Education" (ED). Of these, 83 patients continued to either CBSM (n = 44) or ED (n = 39) intervention. Study end points were mood change, heart rate variability (HRV), double product elevation (DP = heart rate × systolic blood pressure) by math and anger-recall stress, and arrhythmia up to 6 months follow-up. Adjusting for multiple testing, CBSM was associated with moderate effect size reductions in tension/anxiety (P = 0.010), anger/hostility (P = 0.020), perceived stress (P = 0.037), and total mood disturbance (P = 0.025), greatest immediately following intervention (P < 0.05), and partially attributable to increased negative mood following ED (P < 0.01). No significant intervention effects on high frequency or low frequency spectral power of HRV, DP responses, or cardiac arrhythmias were demonstrated. CBSM intervention in ICD recipients resulted in reduced anxiety, anger, and perceived stress, not sustained at 6 months follow-up, and without conclusive effect on cardiac autonomic or hemodynamic responses to mental stress, or arrhythmia. Findings support conduct of larger behavioral intervention arrhythmia trial, with consideration of reinforcement training and targeting of subgroup responders to therapy.

Abstract 51: Heart Rate Variability and its Association with Cognitive Decline Over 20 years: The Atherosclerosis Risk in Communities - Neurocognitive Study

Background: Heart rate variability (HRV) reflects activity of the sympathetic and parasympathetic nervous systems. Low HRV is associated with an increased risk of heart disease and mortality, and risk factors for lower HRV are also linked to cognitive impairment. We assessed whether HRV measures are associated with cognitive decline in the Atherosclerosis Risk in Communities (ARIC) study. Methods: We studied 10,623 individuals (23% African-American, 57% female, mean age 54). HRV measures were obtained from 2-minute electrocardiogram rhythm strips in 1987-89 and include the standard deviation of all normal RR intervals (SDNN), root mean square of successive differences (rMSSD), low frequency (LF) and high frequency (HF) spectral power, and the LF/HF ratio. Cognitive function was measured in 1990-92, 1996-98 and 2011-2013 using 3 neuropsychological tests: Delayed Word Recall (DWR), Digit Symbol Substitution (DSS), and Word Fluency (WF). Scores were standardized and their average was used as a test of global cognitive function. HRV measures were log-transformed and we used linear regression models fit with generalized estimating equations to evaluate associations with cognitive performance over time, which was modeled as a linear spline with a knot at year 6 of follow-up. Results: At baseline, lower levels of HRV were significantly associated with reduced scores in all cognitive tests. Lower baseline levels of HRV measures of sympathetic activity (LF and LF/HF ratio) were associated with faster decline in tests evaluating executive function and language (DSST and WF) (table). We did not observe associations between parasympathetic nervous system measures (rMSSD and HF) and cognitive decline. Conclusion: In this large population-based study, markers of cardiac sympathetic dysfunction measured in mid-life were associated with a faster decline in executive function, which is more frequently affected in cognitive impairment of vascular origin. Additional research should explore the mechanism for this association.

Intra-session stability of short-term heart rate variability measurement: gender and total spectral power influence

Cipryan, L., & Litschmannova, M. (2014). Intra-session Stability of Short-term Heart Rate Variability Measurement: Gender and Total Spectral Power Influence. J. Hum. Sport Exerc., 9(1), pp.68-80. Heart rate variability (HRV) has been increasingly analysed under numerous research settings. HRV measurement reliability is, however, still an unresolved issue. The main purpose is to carry out an intra-session stability evaluation of HRV parameters from short-term recordings by means of orthoclinostatic stimulation in a study group which is stratified by gender or Total Power (PT) magnitude. The goal is to make as homogeneous a study group as possible and investigate whether the reproducibility level could be influenced by these factors. The study group consisted of 103 participants (age 22.3 ± 1.2). Standard HRV indexes were computed: PT (total spectral power), PHF (high frequency spectral power), PLF (low frequency spectral power) and LF/HF. Absolute reliability is assessed by the standard error of measurement and 95% limits of agreement; the relative reliability is assessed by the intraclass correlation coefficient. The markedly different standard error of measurement (SEM) between the Male and Female groups was not observed for any HRV parameters. The intraclass correlation coefficient (ICC) values ranged from 0.67 to 0.95 for males and from 0.69 to 0.97 for females. According to the SEM and ICC, there is no difference between the groups of High PT and Low PT. There are not any significant differences in absolute or relative reliability between the more homogeneous study groups and we have therefore

Effects of weight‐reducing chronic vagal nerve stimulation on cardiovascular, autonomic, and respiratory functions (1126.12)

We assessed potential cardiovascular, autonomic, and respiratory adverse effects of chronic vagal nerve stimulation (VNS). In normotensive rats on standard diet, cervical vagal nerve stimulators were turned on 24 h after surgical implantation or remained off (sham) for the remainder of the study (up to 29 days). After one week of VNS, body weight was reduced by 27% while sham‐treated rats had restored pre‐surgical weight. Chronic VNS caused bradycardia that turned into tachycardia when the stimulators were temporarily turned off. VNS also resulted in hypertension that persisted when the stimulators were turned off. Compared to sham rats, high frequency heart rate variability (parasympathetic cardiac modulation) was markedly increased and low frequency systolic blood pressure variability (sympathetic modulation of vascular tone) was reduced when the stimulators were on, but not when they were off. In rats with chronic VNS a gasping‐like breathing pattern was occasionally noted. Furthermore, respiratory effort assessed by high frequency (respiration‐linked) spectral power of systolic blood pressure, was enhanced in rats with chronic VNS when the stimulators were temporarily turned off. In conclusion, weight‐reducing chronic VNS potentially causes reversible bradycardia, sustained hypertension that cannot be explained by elevated sympathetic modulation of vascular tone, and respiratory distress.Grant Funding Source: Supported by NIH (HL084207 KR), ADA (1‐11‐BS‐127, KR), UI Fraternal Order of Eagles Diabetes Center