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In contrast to continuous positive airway pressure (CPAP), the use of adaptive servo-ventilation (ASV) for treatment of central sleep apnoea (CSA) was associated with increased mortality in patients with chronic systolic heart failure (CHF). In order to characterize the interplay between sleep-disordered breathing, CHF and sympathovagal balance (SVB) this study investigated the effect of nocturnal CPAP and ASV on SVB in CSA patients with or without CHF. Thirty-seven patients with ongoing positive airway pressure therapy (CPAP or ASV) for CSA (17 patients with systolic CHF - left ventricular ejection fraction <50% - and 20 patients with CSA but no CHF) underwent evaluation of SVB (spectral analysis of heart rate -HRV- and diastolic blood pressure variability) during full nocturnal polysomnography. The night was randomly split into equal parts including no treatment (NT), automatic CPAP and ASV. Data analysis was restricted to stable N2 sleep. In patients with CSA and systolic CHF, neither automatic CPAP nor ASV showed favourable effects on parameters reflecting SVB during N2 sleep (all p > 0.05). In contrast, in subjects with CSA without CHF automatic CPAP, but not ASV, favourably altered SVB by decreasing the low frequency and increasing the high frequency component of HRV (both p = 0.03). Effects of various modes of positive airway pressure therapy of CSA on SVB during sleep depend on the mode of pressure support and underlying cardiac function. Automatic CPAP but not ASV favourably influences SVB in subjects without CHF, whereas both interventions leave SVB unchanged in patients with CHF. • In CSA patients without CHF CPAP, but not ASV, favourably alters sympathetic drive. • Both CPAP and ASV leave sympathetic drive unchanged in CSA patients with CHF. • ASV does not lead to desired changes in CHF at night from a translational perspective. • These findings contribute to our understanding of the mechanism behind SERVE-HF. [ABSTRACT FROM AUTHOR]

Objectives: Our study aimed to assess the impact of one night of slow-wave sleep (SWS) suppression on glucose tolerance, and explore whether melatonin plays a role in glucose tolerance impairment after SWS suppression.Methods: In sum, 20 volunteers participated in two experimental sessions: a session with SWS suppression during one night's sleep and a session with a regular night's sleep (control). Each session included collecting seven salivary samples. The following morning, an oral glucose tolerance test (OGTT) was performed.Results: SWS suppression effects depended on the individual blood glucose response to the OGTT. During the control session, 'responders' (N = 11), already presented with low glucose tolerance, which further declined after SWS suppression. 'Non-responders' (N = 9) experienced high glucose tolerance in both conditions. Among the responders, SWS suppression led to an increase in melatonin at the moment of awakening, while in non-responders melatonin increased during the first half of the night. In both conditions, responders were characterized by a shorter total sleep time (TST) and less rapid eye movement (REM) sleep. During SWS suppression, they had more non-rapid eye movement (NREM) stage 1 and longer nocturnal wakefulness. Responders and non-responders showed a comparable amount of SWS.Conclusions: This study highlights three key findings: first, SWS suppression leads to an increase in salivary melatonin; second, melatonin's effect on glucose tolerance depends on its secretion timing; and third, durations of REM sleep and nocturnal awakenings, appear to play an important role in melatonin secretion and glucose tolerance, indicating the potential clinical relevance of these findings for type 2 diabetes risk assessment. [ABSTRACT FROM AUTHOR]

Mitigation of cardiac autonomic dysregulation by neuromodulation technologies is emerging as a new therapeutic modality of heart failure (HF). This recent progress has necessitated the identification of a biomarker for the quantification of sympathovagal balance, the potential target of 'neuromodulation' strategies. The currently available autonomic nervous system assessment parameters do not truly reflect the sympathovagal balance of the ventricle. Protein kinase A (PKA) is an intracellular enzyme that plays a major role in the pathophysiology of functional and structural ventricular remodeling in HF. Interestingly, sympathetic and parasympathetic activations exert reciprocal influence on the activity of PKA. The current review attempts to evaluate the potential concept and feasibility of using in vitro assessment of PKA activity as a marker of sympathovagal balance in HF. [Display omitted] [ABSTRACT FROM AUTHOR]

Enhanced cardiovascular strain is one of the factors that explains degraded aerobic capacity in hot environments. The cardiovascular system is regulated by the autonomic nervous system, whose activity can be indirectly evaluated by analyzing heart rate variability (HRV) and systolic arterial pressure (SAP) variability. However, no study has addressed whether HRV or SAP variability can predict aerobic performance during a single bout of exercise. Therefore, this study aimed to investigate whether there is an association between cardiovascular variability and performance in rats subjected to treadmill running at two ambient temperatures. In addition, this study investigated whether the heat-induced changes in cardiovascular variability and reductions in performance are associated with each other. Male Wistar rats were implanted with a catheter into their carotid artery for pulsatile blood pressure recordings. After recovery from surgery, the animals were subjected to incremental-speed exercise until they were fatigued under temperate (25 °C) and hot (35 °C) conditions. Impaired performance and exaggerated cardiovascular responses were observed in the hot relative to the temperate environment. Significant and negative correlations between most of the SAP variability components (standard deviation, variance, very low frequency [VLF], and low frequency [LF]) at the earlier stages of exercise and total exercise time were observed in both environmental conditions. Furthermore, the heat-induced changes in the sympathetic components of SAP variability (VLF and LF) were associated with heat-induced impairments in performance. Overall, the results indicate that SAP variability at the beginning of exercise predicts the acute performance of rats. Our findings also suggest that heat impairments in aerobic performance are associated with changes in cardiovascular autonomic control. [ABSTRACT FROM AUTHOR]

The brain networks supporting nausea not yet understood. We previously found that while visual stimulation activated primary (V1) and extrastriate visual cortices (MT +/V5, coding for visual motion), increasing nausea was associated with increasing sustained activation in several brain areas, with significant co-activation for anterior insula (aIns) and mid-cingulate (MCC) cortices. Here, we hypothesized that motion sickness also alters functional connectivity between visual motion and previously identified nausea-processing brain regions. Subjects prone to motion sickness and controls completed a motion sickness provocation task during fMRI/ECG acquisition. We studied changes in connectivity between visual processing areas activated by the stimulus (MT +/V5, V1), right aIns and MCC when comparing rest (BASELINE) to peak nausea state (NAUSEA). Compared to BASELINE, NAUSEA reduced connectivity between right and left V1 and increased connectivity between right MT +/V5 and aIns and between left MT +/V5 and MCC. Additionally, the change in MT +/V5 to insula connectivity was significantly associated with a change in sympathovagal balance, assessed by heart rate variability analysis. No state-related connectivity changes were noted for the control group. Increased connectivity between a visual motion processing region and nausea/salience brain regions may reflect increased transfer of visual/vestibular mismatch information to brain regions supporting nausea perception and autonomic processing. We conclude that vection-induced nausea increases connectivity between nausea-processing regions and those activated by the nauseogenic stimulus. This enhanced low-frequency coupling may support continual, slowly evolving nausea perception and shifts toward sympathetic dominance. Disengaging this coupling may be a target for biobehavioral interventions aimed at reducing motion sickness severity. [ABSTRACT FROM AUTHOR]

The present study evaluated the impact of chronic l -citrulline (L-cit) supplementation on resting heart rate variability (HRV) and blood pressure (BP) in obese postmenopausal women. Participants were randomly assign to either an L-cit group (n = 12) or a control group (n = 11). HRV and BP were measured before and after 8 weeks. There were significant decreases ( P < 0.05) in nLF (sympathetic activity), LnLF/LnHF (sympathovagal balance), and BP as well as a significant increase ( P < 0.05) in nHF (vagal tone) following L-cit compared with no changes after control. Our findings indicate that L-cit supplementation improves sympathovagal balance in obese postmenopausal women. [ABSTRACT FROM AUTHOR]

The present study analyzed whether the phase coherency (λ) of respiratory sinus arrhythmia (RSA) is altered by food ingestion in healthy young subjects. After 5 min of resting control, 13 healthy volunteers were asked to eat a solid meal with access to water at their own pace, followed by 5 min of the postprandial state. The R-R interval (RRI), beat-to-beat blood pressure (BP), and respiratory activity were recorded using electrocardiography, a Finapres device, and inductance plethysmography, respectively. The stroke volume was calculated by the pulse-contour method from continuous BP measurement, and the cardiac output (CO) was obtained by multiplying the stroke volume by the heart rate. From the oscillatory signals of RSA and respiration, λ was computed; additionally, frequency domain indexes of the heart rate variability (HRV) were calculated using a short-time Fourier transform. A steady-state 3-min resting period (R), food ingestion period (FOOD), and the first 2-min and the last 3-min of the post prandial period were analyzed separately. We also compared the responses to gum chewing (GUM) and water intake (WATER) using the same protocol on separate days. A shortening of RRI and increases in BP and CO were observed in FOOD compared to R, suggesting a shift of sympathovagal balance toward sympathetic activation. Similar responses but smaller magnitudes were observed in the GUM condition, whereas only transient shortening of RRI was observed in the WATER condition. The HRV indexes did not show any significant changes in response to GUM and WATER but sympathovagal balance was shifted in favor of sympathetic dominance in FOOD. λ decreased during all of the conditions. There was a significant negative correlation between λ and the indirect measure of sympathovagal balance. These results suggest that ingestion of food induces enhanced cardiac sympathetic activity and that a phase coherence of RSA could provide a sensitive measure for evaluating the cardiac autonomic profile. [ABSTRACT FROM AUTHOR]

Studies conducted in major depression (MD) patients have reported a high risk of cardiac morbidity as a result of the relationship between changed cardiovascular activity (CA) and autonomic dysfunctions. The investigation of heart rate variability (HRV) gives valuable idea about variances in autonomic CA of MD patients. To get this knowledge, frequency-domain HRV analysis is frequently performed using Fourier transformation (FT) or discrete-wavelet transformation (DWT) to decompose the data into high-frequency (HF) and low-frequency (LF) bands. Nevertheless, it has been reported that the FT is not useful for nonstationary HRV signals and the DWT does not ensure required frequency boundaries of each band. This study aims to compare the frequency-domain HRV features using wavelet-packet-transform (WPT) with absolutely excellent approximation to required band ranges between the controls and patients. In addition to LF and HF band energies, sympathovagal balance that indicates the variation of sympathetic and parasympathetic activities were compared between two groups. Patients had a significantly lower HF energy, higher values of LF energy and higher LF/HF ratio. Our results recommend that impairments in coordination between parasympathetic and sympathetic behavior in MD patients can be assessed by HRV analysis using WPT with high resolution decomposition for needed bands. [ABSTRACT FROM AUTHOR]

Cardiac autonomic tone can be assessed either by estimating separately vagal and sympathetic tones or by evaluating the net effect of their interaction, the so-called sympathovagal balance (SVB). To compare the most commonly used methods in rats, telemetric recordings of the electrocardiogram were performed in normotensive WKY rats, and in groups of spontaneously hypertensive (SHR) rats that were either untreated or chronically treated with the cholinesterase inhibitor, pyridostigmine, to enhance vagal tone. Cardiac autonomic blockers were administered alone and in combination, so that heart rate (HR) could be measured (1) under resting conditions, (2) with either autonomic branch blocked, and (3) with both branches blocked (which provided intrinsic HR, iHR). SVB was assessed as the ratio of resting HR to iHR. This calculation pointed to a sympathetic predominance in untreated SHRs and even more so in WKY rats, and to a marked vagal predominance in pyridostigmine-treated SHRs. By contrast, the ratio between low and high frequency components (LF/HF) of RR interval spectra did not significantly differ between the groups. Each autonomic tone was quantified as the HR change induced by its selective blocker or as the difference between iHR and HR after blockade of its counterpart. Both pharmacological methods indicated vagal enhancement in treated SHRs, but provided opposite results in terms of vagal vs. sympathetic predominance. These data seriously question the use of the LF/HF ratio as an index of SVB, and the possibility to reliably estimate vagal and sympathetic tones separately through current pharmacological approaches in conscious rats. [ABSTRACT FROM AUTHOR]

The primary purpose of this study was to assess the response of autonomic cardiac activity and changes in the arterial oxygen saturation (SpO 2 ) during normobaric hypoxia and subsequent recovery. Heart rate variability (HRV) and SpO 2 were monitored in a supine position during hypoxia (FiO 2 = 9.6%) for 10 min, and normoxic recovery in 29 subjects. Spectral analysis of HRV quantified the autonomic cardiac activity by means of low frequency (LF) (0.05–0.15 Hz) and high frequency (HF) (0.15–0.50 Hz) power transformed by natural logarithm (Ln). Based on the SpO 2 response to hypoxia, the subjects were divided into Resistant (RG, SpO 2 = 80.8 ± 7.0%) or Sensitive (SG, SpO 2 = 67.2 ± 2.9%) group. The SpO 2 and vagal activity (LnHF) significantly decreased during hypoxia in both groups. A withdrawal in vagal activity was significantly greater in SG compared to RG. Moreover, only in SG, a relative increase in sympathetic modulation (Ln LF/HF) during hypoxia occurred. Correlations ( r = − 0.461, and r = 0.595, both P < 0.05) between ΔSpO 2 (delta) and ΔLn LF/HF, and ΔLnHF were found. Based on results, it seems that SpO 2 level could be an important factor that influences the autonomic cardiac response in hypoxia. [ABSTRACT FROM AUTHOR]

Ford et al. provided (via review study) an overview of the psychiatric features associated with encephalitis mediated by autoantibodies targeting neuronal cellsurface antigens and describe indicators of potential immunopathology underlying psychiatric manifestations. In this scientific context of psychiatric manifestations, studies strongly suggest that scientists include heart rate variability assessment in these patients (because this is a way to evaluate the autonomic nervous system's sympathetic and parasympathetic components). Ford's paper has significant clinical relevance and will generate new studies (experimental and observational) on psychiatric manifestations; therefore, we have six suggestions for the authors and other scientists/researchers who will use this article to perform further research using the heart rate variability assessment. Our objective is to contribute to scientific research and help to strengthen the new studies that will emerge. [ABSTRACT FROM AUTHOR]

Abstract: Objectives: To compare the impact of walking with a recreational activity on postprandial glycemia, heart rate variability, and mood state following the dinner meal. Design: Participants with type 2 diabetes (T2D) participated in 3 trials on different days in random order after ingestion of a standardized dinner meal (300 ± 6 kcals). Setting: University clinical testing laboratory. Participants: Twelve participants (9 female, 3 male; 58.7 ± 2.4 years) with uncomplicated T2D not taking insulin or beta-blocker medications. Intervention: Thirty minutes of self-paced walking on a treadmill (TM), 30 minutes of table tennis played continuously against the iPong robot (TT), and 30 minutes of rest (CON) undertaken 30 minutes after the start of ingestion of the same dinner meal on three occasions within a week. Measurements: Blood glucose was measured at 30-minute intervals through 180 minutes starting immediately prior to the dinner meal. Profile of Mood States was completed before and immediately following exercise or rest. Sympathovagal balance (heart rate variability) was measured prior to eating and 30 minutes after trial completion. Results: Compared with TT or CON, TM resulted in significantly lower postprandial blood glucose (P < .05), as well as a greater quantity of physical activity than TT (+72%) or rest (+91%; P < .01). Mean heart rate during TM was significantly greater than during TT (+25.9 beats per minute; P < .01). However, neither mood state nor HRV were significantly different among trials. Conclusions: Thirty minutes of self-paced walking following the dinner meal may be more effective at lowering postprandial glycemia in T2D than a similar duration of table tennis played continuously against a robot. [Copyright &y& Elsevier]

Abstract: The autonomic nervous system (ANS) is modulated by sleep and wakefulness. Noninvasive assessment of cardiac ANS with heart rate variability (HRV) analysis is a window for monitoring malfunctioning of cardiovascular autonomic modulation due to sleep deprivation. This study represents the first investigation of dynamic ANS effects and of electrophysiological and subjective sleepiness, in parallel, during 40h of prolonged wakefulness under constant routine (CR) conditions. In eleven young male healthy subjects, ECG, EEG, EOG, and EMG chin recordings were performed during baseline sleep, during 40h of sleep deprivation, and during recovery sleep. After sleep deprivation, slow-wave sleep and sleep efficiency increased, whereas HRV – global variability and HRV sympathovagal balance – was reduced (all p<0.05). Sleep-stage-dependent analysis revealed reductions in the sympathovagal balance only for NREM sleep stages (all p<0.05). Comparison of the daytime pattern of CR day one (CR baseline) with that of CR day two (CR sleep deprivation) disclosed an increase in subjective sleepiness, in the amount of unintended sleep, and in HRV sympathovagal balance, with accompaniment by increased EEG alpha attenuation (all p<0.05). Circadian rhythm analysis revealed the strongest influence on heart rate, with less influence on HRV sympathovagal balance. Hour-by-hour analysis disclosed the difference between CR sleep deprivation and CR baseline for subjective sleepiness at almost every single hour and for unintended sleep particularly in the morning and afternoon (both p<0.05). These findings indicate that 40h of prolonged wakefulness lead in the following night to sleep-stage-dependent reduction in cardiac autonomic modulation. During daytime, an increased occurrence of behavioral and physiological signs of sleepiness was accompanied by diminished cardiac autonomic modulation. The observed changes are an indicator of autonomic stress due to sleep deprivation — which, if chronic, could potentially increase cardiovascular risk. [Copyright &y& Elsevier]

Abstract: Background: Treatment with positive airway pressure devices improved signs and symptoms of obstructive sleep apnea syndrome (OSA); however, auto-adjusting positive pressure (APAP) device was not as effective as continuous positive airway pressure (CPAP) in reducing arterial blood pressure and insulin resistance. The role played by autonomic cardiac regulation remains to be clarified. We aimed to test the effects of CPAP and APAP on autonomic regulation and cardiorespiratory coupling during sleep. Methods: We retrospectively analyzed full-night polysomnographic studies. 19 patients newly diagnosed with severe OSA (AHI>30) and 7 obese subjects without OSA (CON) were enrolled. Each OSA subject was assigned to CPAP or APAP treatment and underwent a sleep study after 1week of treatment. Spectral and cross-spectral analyses of heart rate variability (HRV) and respiration were performed to assess autonomic profile and coherence (K2) between respiration and HF oscillation during sleep in CPAP, APAP and CON groups. Results: In CPAP and CON, LFnu and LF/HF, markers of sympathetic modulation, decreased from N2 to N3 and increased during REM sleep (p<0.001), while in APAP group, sympathetic modulation was significantly higher compared with those of CPAP and CON during all sleep stages. K2 values were lower in APAP compared with those in CPAP and CON. Conclusion: APAP treatment was characterized by a greater sympathetic activation and it was associated with a lower cardio-respiratory coupling compared with CPAP. This might account for the different effects on cardiovascular risk factors induced by the two treatments. [Copyright &y& Elsevier]

Abstract: A link between exaggerated chemoreceptor sensitivity and hypertension has been documented in the spontaneously hypertensive rat (SHR) but has also been questioned when comparisons with normotensive strains other than the Wistar Kyoto (WKY) rat are made. To further evaluate the link between hypertension and chemoreflex sensitivity, changes in cardiorespiratory variability in response to three successive bouts of 5min of hypoxia (21%→10%) were evaluated in conscious male SHR, and WKY and Sprague Dawley (SD) rats (n=7–8/group). In response to the first bout of hypoxia, the change in respiratory frequency (RF) was greatest in the SHR, but the increase in mean arterial pressure (MAP) was similar in both SHRs and WKY rats and all strains demonstrated a similar rise in heart rate (HR). All strains showed some level of response accommodation during subsequent bouts of hypoxia. Spectral analysis of HR variability identified a significant difference in high frequency (HF) power between strains during hypoxia, including an increase in HF power in the WKY rats, a decrease in the SHRs and little overall change in the SD rats. Alternatively, all strains demonstrated a rise in systolic arterial pressure (SAP) variability in the low frequency (LF) range in response to hypoxia but the increase was greatest in the SHR. Since SAP LF power is linked to vasosympathetic tone, these results support the hypothesis that essential hypertension is linked to exaggerated sympathetic responses to chemoreceptor stimulation but confirm that estimation of augmented reflex function cannot be determined by quantifying simple changes in MAP or HR. [Copyright &y& Elsevier]

Abstract: The comorbidity of major depressive disorder (MDD) and cardiovascular disease (CVD) is among the 10th leading cause of morbidity and mortality worldwide. Thus, understanding the co-occurrence of these disorders will have major public health significance. MDD is associated with an abnormal stress response, manifested in brain circuitry deficits, gonadal dysfunction, and autonomic nervous system (ANS) dysregulation. Contribution of the relationships between these systems to the pathophysiology of MDD is not well understood. The objective of this preliminary study was to investigate, in parallel, relationships between HPG-axis functioning, stress response circuitry activation, and parasympathetic reactivity in healthy controls and women with MDD. Using fMRI with pulse oximetry [from which we calculated the high frequency (HF) component of R-R interval variability (HF-RRV), a measure of parasympathetic modulation] and hormone data, we studied eight women with recurrent MDD in remission and six controls during a stress response paradigm. We demonstrated that hypoactivations of hypothalamus, amygdala, hippocampus, anterior cingulate cortex (ACC), orbitofrontal cortex (OFC), and subgenual ACC were associated with lower parasympathetic cardiac modulation in MDD women. Estradiol and progesterone attenuated group differences in the effect of HF-RRV on hypoactivation in the amygdala, hippocampus, ACC, and OFC in MDD women. Findings have implications for understanding the relationship between mood, arousal, heart regulation, and gonadal hormones, and may provide insights into MDD and CVD risk comorbidity. [Copyright &y& Elsevier]

Abstract: Neurocardiac dysregulation has been reported in schizophrenia. Indices of heart rate variability (HRV) are useful in assessing the status of cardiac autonomic regulation. We explored within-subject changes in HRV indices in acutely ill patients with schizophrenia treated with risperidone. Sixteen medication-naïve or medication-free patients with DSM-IV schizophrenia completed electrocardiogram (ECG) assessments at baseline and after six weeks of treatment with risperidone. Indices of HRV were extracted from 5-min resting ECG recordings and compared to those obtained from control subjects matched for age and gender. Psychiatric and drug-induced extrapyramidal symptoms were assessed by the Positive and Negative Syndrome Scale (PANSS) and the Drug-Induced Extrapyramidal Symptoms Scale (DIEPSS). In comparison with matched controls, patients with acute schizophrenia showed lower values of time-domain measures, lower high-frequency power (HF) and a higher ratio of low to high frequency (LF/HF). In the within-subject analyses, a significant decrease in LF/HF was associated with risperidone treatment. In addition, LF/HF, which initially co-clustered with clinical variables, congregated with other HRV measures after the six-week risperidone treatment. These results indicate that, in the therapeutic process, risperidone treatment may exert a beneficial influence on the sympathovagal imbalance in acute schizophrenia. [Copyright &y& Elsevier]

Abstract: Post stress neurovascular responses induced by physical and mental stress are poorly understood. We investigated the time course of cardiovascular and autonomic recovery, induced by orthostatic and mental challenge, using passive head up tilt (HUT) and mental arithmetic (MA), respectively, when applied singly (MA, HUT) or in combination (MA+HUT). Fifteen healthy males participated in three protocols: HUT, MA and combined MA+HUT, with sessions randomized and 2weeks apart. Post stress responses were studied in the first 10min (early; cardiovascular only) and 30min (late), in 2.5min epochs. A detailed analysis of early period was done in 30s epochs. Within the first 2.5min recovery, time courses of heart rate, stroke volume and cardiac output differed significantly, particularly when comparing HUT vs. MA and MA+HUT vs. MA. Additionally, heart rate response differed in HUT vs. MA+HUT. No differences in hemodynamic recovery were seen during the next 2.5min. Late responses of heart rate and cardiac output showed significantly lower values as compared to baseline, especially for HUT and MA+HUT. Recovery of hemodynamic responses, either due to single or combined stress challenges, showed stressor- and time-dependent patterns. Our data provide useful information regarding why longer recovery periods must be assessed and provide novel insights regarding recovery of physical and mental stressors. This may have clinical implications in the development of cardiovascular diseases such as hypertension or myocardial ischemia. [Copyright &y& Elsevier]

Abstract: The neural regulation of circulatory function is mainly effected through the interplay of the sympathetic and vagal outflows. This interaction can be explored by assessing cardiovascular rhythmicity with appropriate spectral methodologies. Spectral analysis of cardiovascular signal variability, and in particular of RR period (heart rate variability, HRV), is a widely used procedure to investigate autonomic cardiovascular control and/or target function impairment. The oscillatory pattern which characterizes the spectral profile of heart rate and arterial pressure short-term variability consists of two major components, at low (LF, 0.04–0.15Hz) and high (HF, synchronous with respiratory rate) frequency, respectively, related to vasomotor and respiratory activity. With this procedure the state of sympathovagal balance modulating sinus node pacemaker activity can be quantified in a variety of physiological and pathophysiological conditions. Changes in sympathovagal balance can be often detected in basal conditions, however a reduced responsiveness to an excitatory stimulus is the most common feature that characterizes numerous pathophysiological states. Moreover the attenuation of an oscillatory pattern or its impaired responsiveness to a given stimulus can also reflect an altered target function and thus can furnish interesting prognostic markers. The dynamic assessment of these autonomic changes may provide crucial diagnostic, therapeutic and prognostic information, not only in relation to cardiovascular, but also non-cardiovascular disease. As linear methodologies fail to provide significant information in conditions of extremely reduced variability (e.g. strenuous exercise, heart failure) and in presence of rapid and transients changes or coactivation of the two branches of autonomic nervous system, the development of new non-linear approaches seems to provide a new perspective in investigating neural control of cardiovascular system. [Copyright &y& Elsevier]

Abstract: Background: Depression is associated with greater cardiac morbidity and mortality. One of the contributory factors for this may be altered cardiac autonomic activity in depression. However, cardiac autonomic involvement in depression remains controversial because of methodological issues. In this study, alteration of cardiac autonomic functions was studied in drug-naive patients with major depression without co-morbidity. Heart rate variability, a sensitive measure of neurocardiac autonomic regulation was used in addition to conventional methods of measuring cardiac autonomic functions. Methods: We recruited 40 patients suffering from major depression, diagnosed based on DSM-IV-TR criteria. Their cardiac autonomic functions were measured using both conventional and heart rate variability measures. These were compared with those of age- and gender-matched healthy controls. Results: Patients with major depression showed significantly lesser Valsalva ratio, maximum/minimum ratio and greater sympathovagal balance than healthy controls indicating decreased parasympathetic and increased sympathetic activity. Conclusions: Depression is associated with alteration of cardiac autonomic tone towards decreased parasympathetic activity and an increased sympathetic activity. It is possible that a common neurobiological dysfunction contributes to both depression and cardiac autonomic changes in the illness. [Copyright &y& Elsevier]

Abstract: Power spectrum analysis of cardiovascular signal variability, and in particular of the RR period (heart rate variability, HRV), is a widely used methodology for investigating autonomic neural regulation in health and disease that can quantify the sympathovagal balance modulating the sinus node pacemaker. In some cases, it can also quantify the neural regulation of other organs or apparatuses. However, use of the correct methodology is crucial to extract the information embedded in the frequency domain. In numerous abnormal conditions, such as essential arterial hypertension, acute myocardial infarction and heart failure, the sympathovagal balance may be altered in basal conditions. However, a reduced responsiveness to an excitatory stimulus is the most common feature that characterizes numerous pathophysiological states. The attenuation of an oscillatory pattern can also reflect an altered target function, thus providing important prognostic markers. The general features of this approach correspond well to the needs of an internist attempting to envisage the involvement of the whole organism in a disease process. [Copyright &y& Elsevier]

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The relationship between the Renin-Angiotensin-Aldosterone System (RAAS) and modulation of the Autonomic Nervous System (ANS) is reported as complex and bidirectional. Thus, the present study aimed to compare autonomous heart control, through symbolic analysis parameters, in the older adults carrying different ACE I/D gene polymorphisms (rs4646994). Two hundred four older adults comprised the study population and were grouped according to the ACE I/D gene polymorphism: II + ID genotype and DD genotype. Successive RR intervals were recorded along 5 min and analyzed with Symbolic Analysis (SA) method. 0 V%, 1 V% and 2 V% patterns were quantified and compared between groups. A linear mixed model analysis was used to determine between-group differences in symbolic analysis parameters (0 V%, 1 V% and 2 V%), taken groups as fixed factor and sex, use of ACE inhibitors and Angiotensin II receptor type I blockers as random factors. The Bayesian analysis was carried out to check the magnitude of the evidence. The results of this study indicate that older adults carrying the DD genotype have statistically greater sympathetic modulation (0 V%) and poor sympathovagal balance (1 V%), but the Bayesian analysis indicate only an anecdotal effect. Sympathetic predominance is recognized a worrying condition, since may predisposes to cardiovascular risk. • The sympathetic portion of the Autonomic Nervous System stimulates renin secretion. • Many elements of the RAAS stimulate the sympathetic and inhibit the parasympathetic activity. • ACE I/D gene polymorphism is associated to hypertension in young people. • Older adults carrying DD genotype exhibited greater sympathetic modulation. • Older adults carrying DD genotype also exhibited poor sympathovagal balance. [ABSTRACT FROM AUTHOR]

Abstract: RR-interval and eight types of mood level were recorded for 48 h from 40 normal male subjects. Sympathovagal balance was evaluated by calculating the normalized high-frequency power (HFnu) of RR-interval variability. The mean mood levels during 6 h before bedtime and the mean HFnu during 3 h after bedtime were compared. The data were normalized individually and the differences from the first night (Δmood and ΔHFnu) were taken. The correlation coefficient between Δdepression and ΔHFnu was −0.53, and that between Δworry and ΔHFnu was −0.44. This implies that both daily depression and worry shift toward sympathetic dominance during subsequent sleep. [Copyright &y& Elsevier]

• Hyperuricemia is associated to negative effects on the cardiovascular system. • Hyperuricemic older adults presented higher sympathetic activity. • Cardioprotection offered by vagal modulation is impaired in hyperuricemic older adults. • Older adults with hyperuricemia presented sympathovagal imbalance. This study aimed to compare heart rate variability (HRV) parameters obtained through symbolic analysis (SA), between older adults with and without hyperuricemia. This is a cross-sectional study including 202 community-dwelling old adults, which was clinically stratified as with or without hyperuricemia, according to the cutoff point of serum uric acid ≥ 6 mg/dL for women and ≥ 7 mg/dL for men. Successive RR intervals were recorded along 5 min and analyzed with SA method. 0 V%, 1 V% and 2 V% patterns were quantified and compared between groups. Comparisons were carried out through parametric or nonparametric tests, according to the data distribution characteristics, evaluated by Kolmogorov-Smirnov test. The significance level was set as p ≤ 0.05 for all statistical procedures. The prevalence of hyperuricemia was 67.8 %, and the hyperuricemic older adults exhibited significant higher values for V0% and lower values for V2% parameters when compared to normouricemic older adults. These results suggesting a sympathovagal imbalance in hyperuricemic older adults, characterized by greater sympathetic predominance (0 V%) and lower vagal modulation (2 V%) at rest conditions. [ABSTRACT FROM AUTHOR]