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Aims: To evaluate the acute and chronic effect of an exercise protocol of pelvic floor muscles (PFMs) contraction on the heart period (HP) and systolic arterial pressure (SAP) variabilities and baroreflex sensitivity (BRS) at rest in pregnant women; and to evaluate if this progressive exercise protocol was well‐tolerated by the pregnant women studied. Methods: We evaluated 48 women at 18 weeks of pregnancy by vaginal palpation, vaginal manometry, and cardiopulmonary exercise test. They were divided in control (CG; 31.75 ± 3.91 years) and training groups (TG; 30.71 ± 3.94 years). At 19 and 36 weeks of pregnancy, electrocardiogram and noninvasive peripheral SAP data were collected at rest before and after 10 PFM contractions. TG performed PFMT from the 20th to the 36th week. HP and SAP variabilities were analyzed by spectral and symbolic analysis. The baroreflex was evaluated by cross‐spectral analysis between the HP and SAP series. Results: The groups did not differ in relation to VO2, HP and SAP variabilities, and BRS at the beginning of the protocol. TG increased the endurance of the PFM after training. PFM contraction did not change the HP and SAP variabilities, and BRS at the 18th week. After the training, the TG presented lower SAP mean, lower BF of SAP variability, and higher BRS than CG. Conclusions: Acute PFM contractions did not alter HP and SAP variabilities and BRS, but PFMT resulted in a lower SAP mean and higher BRS in trained pregnant when compared to the untrained. [ABSTRACT FROM AUTHOR]

Background: Children's ability to remain focused on a task despite the presence of emotionally salient distractors in the environment is crucial for successful learning and academic performance. Aims: This study investigated first‐graders' allocation of attentional resources in the presence of distracting emotional, school‐related social interaction stimuli. Moreover, we examined whether such attentional processes were influenced by students' self‐regulation, as indexed by heart period variability, observed classroom climate, or their interaction. Sample: Seventy‐two‐first graders took part in the study. Methods: To assess allocation of attentional resources, students' reaction times on an emotional Stroop task were registered by recording response times to colour frames placed around pictures of distracting emotional, school‐related social interaction stimuli (i.e., emotional interference index). Moreover, heart period variability was measured by recording children's electrocardiogram at rest during an individual session, whereas classroom climate was observed during class activities by a trained researcher. Results: Images representing negative social interactions required greater attentional resources than images depicting positive ones. Heart period variability and classroom climate were each significantly and independently associated with the emotional interference index. A significant interaction also emerged, indicating that among children experiencing a negative classroom climate, those who had a higher basal heart period variability (higher self‐regulation) were less distracted by negative emotional material and remained more focused on a task compared to those with lower heart period variability (lower self‐regulation). Conclusions: Negative interactions require greater attentional resources than positive scenes. Moreover, with a negative classroom climate, higher basal heart period variability is a protective factor. Implications for theory and practice are discussed. [ABSTRACT FROM AUTHOR]

The aim of this study is to define absolute and relative reliability of spectral indices of cardiovascular autonomic control in the supine position in women with fibromyalgia syndrome (FMS). Twenty-three women with FMS (age 48 ± 7 years) took part in the study. ECG, finger blood pressure, and respiration were continuously recorded in all participants at rest in baseline 1 (BL1) and after 15 days from BL1 (BL2). The power spectrum analysis provided two oscillatory components: low frequency (LF, 0.04-0.15 Hz) and high frequency (HF, 0.15-0.4 Hz) from the heart period (HP) variability and the LF oscillatory component from SAP variability (LF). Absolute and relative reliability were rated by 95 % of the limit of random variation and intraclass correlation coefficient (ICC), respectively. No significant differences were observed between BL1 and BL2 for the spectral indices of HP and SAP variabilities. The 95 % limit of the random variation of these indices indicated that the values of repeated measurements were between 22 % higher and 0.2 % lower (more reliable parameter; average of HP variability) and 912.9 % higher and 0.2 % lower (less reliable parameter; LF) than BL1. Conversely, the index of relative reliability (ICC) ranged from 0.23 to 0.70 indicating a good reliability. The spectral indices of cardiovascular autonomic control in women with FMS seem to present good relative reliability. Therefore, these indices can be useful as parameters to quantify if a variation was consistent and accurate in the retest besides adding crucial information for clinical research and clinical evaluation of FMS patients. [ABSTRACT FROM AUTHOR]

The overall goal of this study was to determine if Parasympathetic Nervous System Activity (PsNS) is a significant biomarker of sensory processing difficulties in children. Several studies have demonstrated that PsNS activity is an important regulator of reactivity in children, and thus, it is of interest to study whether PsNS functioning affects sensory reactivity in children who have a type of condition associated with Sensory Processing Disorders (SPD) termed Sensory Modulation Dysfunction (SMD). If so, this will have important implications for understanding the mechanisms underlying sensory processing problems of children. The primary aims of this project were to: (1) evaluate PsNS activity in children with SMD compared to typically developing (TYP) children, and (2) determine if PsNS activity is a significant predictor of sensory behaviors and adaptive functions among children with SMD. As a secondary aim we examined whether subgroups of children with specific physiological and behavioral sensory reactivity profiles can be identified. Results indicate that the children with severe SMD demonstrated a trend for low baseline parasympathetic activity, compared to TYP children, suggesting this may be a biomarker for severe SMD. In addition, children with SMD demonstrated significantly poorer adaptive behavior. These results provide preliminary evidence that children who demonstrate SMD may have physiological responses that are different from children without SMD, and that these physiological and behavioral manifestations of SMD may affect a child’s ability to engage in everyday social, communication, and daily living skills.

The study examined whether cardiorespiratory fitness modifies cardiovascular responses by normotensive men and women during the Stroop color-word interference test. Independent of age and an estimate of body fatness, fitness level was positively related ( R2 = .39 and .51) to increases in limb blood flow and vascular conductance, coherent with cardiac-vagal withdrawal and a decrease in heart period, among women but not men. Fitness was unrelated to changes in systolic and diastolic blood pressures and muscle sympathetic nerve activity. The augmented hemodynamic responses among fitter women were not consistent with passive vasodilation via withdrawal of sympathetic neural tone. The results encourage further gender comparisons testing whether fitness augments limb blood flow during mental stress by neurohumoral and flow-mediated vasodilatory mechanisms or by increased cardiac output. [ABSTRACT FROM AUTHOR]

Objective: The effect of 12 weeks of high-intensity intermittent exercise (HIIE) on cardiac, vascular, and autonomic function of young males was examined. Methods: Thirty-eight young men with a BMI of 28.7 ± 3.1 kg m and age 24.9 ± 4.3 years were randomly assigned to either an HIIE or control group. The exercise group underwent HIIE three times per week, 20 min per session, for 12 weeks. Aerobic power and a range of cardiac, vascular, and autonomic measures were recorded before and after the exercise intervention. Results: The exercise, compared to the control group, recorded a significant reduction in heart rate accompanied by an increase in stroke volume. For the exercise group forearm vasodilatory capacity was significantly enhanced, P < 0.05. Arterial stiffness, determined by pulse wave velocity and augmentation index, was also significantly improved, after the 12-week intervention. For the exercise group, heart period variability (low- and high-frequency power) and baroreceptor sensitivity were significantly increased. Conclusion: High-intensity intermittent exercise induced significant cardiac, vascular, and autonomic improvements after 12 weeks of training. [ABSTRACT FROM AUTHOR]

Abstract: The data collected by ambulatory blood pressure monitoring have been studied in the phase-space of R–R interval and blood pressure and their individual distribution quantified by the slope of the regression line through 24-h values. This slope has been termed “ambulatory autonomic reciprocity index” and abbreviated as AARIs and AARId, the “s” and “d” indicating the relation with systolic and diastolic blood pressure respectively. Ambulatory monitoring was performed in 200 normotensive (NT: 135 females) and 200 untreated hypertensive patients (HT: 59 females). The AARIs was: NT: −6.04±2.7 and HT: −4.69±2.4ms/mmHg, respectively (p <0.001); the AARId was: −7.04±2.9 for NT and −5.79±2.8 for HT subjects (p <0.001). When distributed by decades of life the steepest AARIs occurred at the 20–29 decade, while the flattest at the 60–69 decade. At the 60–69 decade and above, the AARIs was similar in both groups (ANOVA o.w. NT: p <0.001; HT: p <0.01). AARIs and AARId were strongly correlated with 24-h variability of R–R interval, either 24-h standard deviation or coefficient of variation (p <0.001), and poorly correlated with 24-h variability of blood pressure. These data suggest that the AARI, when seen in the context of the “Autonomic Space”, may be viewed as a 24-h period index of centrally driven cardiovagal function. Being based on both blood pressure and heart rate measurements, the AARI may become clinically useful to address life style changes and pharmacological treatment of hypertensive patients towards optimal results. [Copyright &y& Elsevier]

The article presents a study that aims to determine whether heart period variability metrics provides added value in determining the need for lifesaving interventions (LSI) in traumatized patients with normal vital signs upon early medical assessment. Heart period variability was analyzed through electrocardiographic recordings collected from 159 patients. Based on the results presented, heart variability seems to have limited value for prediction of LSI in patients with normal vital signs.

The article discusses a study which explored the hypothesis that nontouch therapy such as therapeutic touch (TT) reduces stress to a clinically important degree and is safe to use in preterm infants. The study involved two groups of 10 infants who were enrolled and randomly assigned to treatment or nontreatment groups. It was found that there had been no increase in adverse events in TT group compared with no therapeutic touch (NTT) group.

Abstract: In this paper, we investigated ambulatory sleep heart period variability in panic disorder participants with nocturnal panic (NP) compared to daytime panic attacks only. A time-derived measure of heart period variability (HPV) during sleep was significantly reduced in the NP group (n =32) relative to the daytime panic (n =17) and nonanxious (n =17) control groups. Consistent with previous work, NP participants also reported greater fear of relaxation and sleep than daytime panic and control groups. Based on a neurovisceral model of attention [Thayer, J. F., & Lane, R. D. (2000). A model of neurovisceral integration in emotion regulation and dysregulation. Journal of Affective Disorders, 61, 210–216] that predicts that decreased HPV is related to disregulated behavioral adaptation, we hypothesized that HPV measured during sleep would be most reduced in NP participants. These findings indicate that HPV is related to nocturnal panic disorder insofar as it is measured during sleep. [Copyright &y& Elsevier]

Abstract: Previous studies suggest depression is a risk factor for all cause mortality, with depressed men at greater risk than depressed women. Diminished cardiac vagal control (CVC) in depressed patients has also been found to increase risk of cardiac mortality. Previous research found that depressed women have higher CVC than depressed men suggesting CVC might be related to the discrepancy in mortality rates between depressed men and women. This finding, however, was in the context of a study with several methodological weaknesses. The current study sought to replicate the sex difference in CVC in a sample of 137 medically healthy and clinically diagnosed depressed patients. Main effects of sex and age significantly predicted CVC such that depressed women had greater CVC and CVC decreased with age in the cross-sectional sample. The results suggest greater CVC in depressed women might confer cardioprotective functions, which may partially explain the sex difference in mortality rates in the depressed population. [Copyright &y& Elsevier]

Abstract: The purpose was to examine the effect of verbal response and task difficulty on cardiovascular response to the Stroop task. Heart rate, mean arterial blood pressure, forearm blood flow (FBF), and catecholamine response of 13 males was assessed during 3, 5-min differing versions of the Stroop task. Heart rate, epinephrine, and FBF were significantly greater during Stroop 1 (the color-word conflict task) compared to Stroop 3 (a non-verbal version of Stroop where participants responded cognitively without any oral or behavioural response), whereas mean arterial pressure was significantly greater during Stroop 1 than that of Stroop 2 (slides in monochrome without color conflict) and Stroop 3. Rating of level of difficulty and concentration was lower for Stroop 2 compared to the other two Stroop tasks. These results suggest that performance of the traditional Stroop task caused significant cardiovascular, FBF, and epinephrine reactivity. This reactivity was attenuated during reading of monochrome words and was virtually abolished when performing the Stroop without verbally responding. [Copyright &y& Elsevier]

Heart rate variability (HRV) indices based on 24-hr electrocardiograph recordings have been used in clinical research studies to assess the aggregate activity of the autonomic nervous system. Although 24-hr HRV is generally considered noninvasive, use in research protocols typically involves considerable data collection and processing expenses and substantial participant burden. The purposes of this research methods evaluation were to describe the relationships between 24-hr minimum heart rate (HR) and several 24-hr time domain HRV indices (Ln SDNN, Ln SDANN, Ln SDNNIDX, Ln RMSSD, and Logit50) across several research data sets (normal women, normal men, children enrolled in a study of recurrent abdominal pain, women with irritable bowel syndrome, sudden cardiac arrest survivors, and heart failure patients) and to explore the possibility that 24-hr minimum HR might serve as a simpler alternative or adjunct to HRV measures in some situations. The correlations of global HRV measures (e.g., Ln SDNN, Ln SDANN) with 24-hr minimum HR were consistently larger (typical r ∼ -.80) than with average HR (typical r ∼ -.50). In repeated measurements, change in minimum HR was also correlated with change in general HRV (typical r ∼-.60). However, modest differentiation of minimum HR and HRV measures was noted in patients taking certain classes of cardiac medications (e.g., antiarrhythmics, beta blockers). Twenty-four-hour mini mum HR is correlated with general time domain HRV measures and might be useful as a simpler proxy, surrogate, or auxiliary variable in some clinical research applications, especially those in which participants are not receiving cardiac medications. [ABSTRACT FROM AUTHOR]

Physiological and behavioral correlates of anger dysregulation in adults were evaluated in the context of marital stress. Fifty-four married couples participated in a series of laboratory procedures that included electrocardiogram measures during a 15-min marital conflict interaction and an interview assessing their inability to regulate anger (anger dysregulation). Results from the multivariate regression analyses indicated that the nature of the couple's relationship, rather than individual levels of anger dysregulation, predicted lower parasympathetic cardiac activity (indexed by high-frequency heart period variability) and shorter cardiac interbeat intervals. Anger dysregulation, rather than the dyadic relationship, was predictive of greater displays of angry behavior during the marital conflict interaction. The importance of contextual factors in stress processes, such as stress due to marriage, are discussed in light of research linking poor marital quality to greater health risks for women than for men. [ABSTRACT FROM AUTHOR]

Abstract: Objective: The aim of this study was to examine the effects of breast feeding on autonomic nervous system (ANS) response to stressors. Methods: Sympathetic and parasympathetic activities were examined before, during, and after standard laboratory stressors in women who were either exclusively breast feeding (n=14) or nonexclusively breast feeding (n=14), and in non-postpartum controls (n=15). Results: Mothers who breast fed exclusively showed greater levels of parasympathetic cardiac modulation and slower heart rate (HR) throughout the session and less HR increase and preejection period (PEP) shortening to mental arithmetic (MA) than did nonexclusive breast feeders and controls. Nonexclusive breast-feeders showed greater electrodermal reactivity to, and greater differences in skin conductance response (SCR) frequency between baseline and recovery from cold pressor (CP) than did either exclusive breast-feeders or controls. Sympathetic activity was negatively related to the number of breast feedings and positively related to bottle feedings. Conclusion: Breast feeding shifts maternal ANS balance toward relatively greater parasympathetic and lesser sympathetic activity; the opposite occurs with bottle feeding. The frequency of feeding also is a critical factor in determining breast feeding effects on maternal ANS function. [Copyright &y& Elsevier]

Persistence of respiratory sinus arrhythmia (RSA) has been described in humans during intense exercise and attributed to an increase in ventilation. However, the direct influence of ventilation on RSA has never been assessed. The dynamic evolution of RSA and its links to ventilation were investigated during exercise in 14 healthy men using an original modeling approach. An evolutive model was estimated from the detrended and high-pass-filtered heart period series. The instantaneous RSA frequency (FRSA, in Hz) and amplitude (ARSA, in ms) were then extracted from all recordings. ARSA was calculated with short-time Fourier transform. First, measurements of FRSA and ARSA were performed from data obtained during a graded and maximal exercise test. Influences of different ventilation regimens [changes in tidal volume (V T) and respiratory frequency (FR)] on ARSA were then tested during submaximal [70% peak O2 consumption (VO2 peak)] rectangular exercise bouts. Under graded and maximal exercise conditions, ARSA decreased from the beginning of exercise to 61.9 ± 3.8% VO2 peak and then increased up to peak exercise. During the paced breathing protocol, normoventilation (69.4 ± 8.8 l/min), hyperventilation (81.8 ± 8.3 l/min), and hypoventilation (56.4 ± 6.2 l/min) led to significantly (P < 0.01) different ARSA values (3.8 ± 0.5, 4.6 ± 0.8, and 2.9 ± 0.5 ms, respectively). In addition, no statistical difference was found in ARSA when ventilation was kept constant, whatever the FR-VT combinations. Those results indicate that RSA persists for all exercise intensities and increases during the highest intensities. Its persistence and increase are strongly linked to both the frequency and degree of lung inflation, suggesting a mechanical influence of breathing on RSA. [ABSTRACT FROM AUTHOR]

Objective: To measure the effects of fluoxetine and pemoline on heart period and QT variability. Methods: Healthy volunteers were randomly assigned treatment with 20 mg daily of fluoxetine (n=7), 56.25 mg of pemoline (n=7) or placebo (n=9). Twenty-four-hour Holter ECGs were obtained before and after approximately 8 weeks of double-blind treatment. Results: There were no significant changes in the fluoxetine group. Pemoline was associated with a significant decrease in the high frequency (HF) power (0.15–0.5 Hz, P=.02) and fractal dimension of RR time series (P=.03). QTvi, a measure of QT interval variability, increased in the pemoline group (P=.05). Conclusion: Pemoline, but not fluoxetine, decreases heart period variability (HPV) in the HF power, suggesting a vagolytic effect on cardiac autonomic function. Pemoline is also associated with an increase in QT interval variability, a measure that is sensitive to adrenergic agonists. [Copyright &y& Elsevier]

Vagus nerve stimulation (VNS) has been suggested as an adjunctive treatment for drug-resistant epilepsy when surgery is inadvisable. The overall safety profile of VNS seems to be favorable as only minor adverse effects have been described. The purpose of this study was to determine if cardiac vagal tone is eventually modified by short- and long-term VNS. The effects of short- and long-term VNS were evaluated in seven subjects with intractable epilepsy. Autonomic cardiac function has been carried out by means of a 24-h analysis of RR variability at baseline (t0), 1 month (t1, short-term VNS) and 36 months after VNS initiation (t2, long-term VNS). Frequency- and time-domain parameters were calculated. Periodic cardiological and neurological evaluations were performed.Clinically relevant cardiac effects were not observed throughout the study. Despite the limited number of patients and the variety of data among them, for all the patients, a common trend towards a nocturnal decrease in the high-frequency (HF) component of the spectrum was observed after long-term VNS (mean±S.D.: 40±18 normalized units (nu) at t0, 38±17 nu at t1, 18±10 nu at t2; p<0.05 of t2 vs. either t0 or t1). The day-to-night changes in the power of low-frequency (LF) and HF components were significantly blunted after long-term VNS (LF day-to-night change: +16±13 nu at t0 and +15±8 nu at t1 vs. +3±13 nu at t2, p<0.02; HF day-to-night change: −18±13 nu at t0 and −13±11 nu at t1 vs. +3±12 nu at t2, p<0.003). No significant changes were observed with regard to the time-domain parameters of the heart rate variability.Throughout the neurological follow-up, one subject became seizure-free, three experienced a seizure reduction of >50%, two patients of <50% and one had no changes in his seizure frequency.Our findings suggest that long-term VNS might slightly affect cardiac autonomic function with a reduction of the HF component of the spectrum during night and a flattening of sympathovagal circadian changes, not inducing, however, clinically relevant cardiac side effects. [Copyright &y& Elsevier]

The aim of the present study was to examine autonomic function in response to negatively and positively valenced pictures under different levels of conscious recognition. Heart period variability (HPV) and heart rate (HR) reactivity were studied in 53 males and females who were being shown pictures of angry and happy faces. The pictures, which were backwardly masked, were presented once every 30 s during a 5-min period and under three conditions (counterbalanced for type of facial expression): below the level of conscious recognition (17 ms), at an intermediate level (56 ms), and at a clearly recognizable level (2370 ms). Analyses of HR power spectrum (for 5 min in each condition) in the high frequency region (HF: 0.15–0.5 Hz) that reflects respiratory sinus arrhythmia, as well as analysis of phasic heart rate responses (7.5 s in 0.5 epochs following every picture presentation) were carried out. The main findings were that HF-power was higher, and cardiac midinterval acceleration lower, in response to angry as opposed to happy faces, a result obtained only for the men, however. No interaction effect between facial expression and the three exposure conditions was found, suggesting that the pictures induced emotional activation both subliminally and supraliminally. The results were discussed in terms of increased attention to aversive stimuli. [Copyright &y& Elsevier]

: ObjectivesThe purpose of our investigation was to examine serial changes in autonomic nervous system activity along with measurements of hemodynamics and cardiac contractility, in assessing the mechanism(s) that underlie neurally mediated cardiac syncope (NMCS) in children.: BackgroundPrevious research that used heart rate variability analysis alone to understand changes in autonomic activity that result in NMCS has provided conflicting results. We performed simultaneous heart rate and blood pressure variability analyses to characterize dynamic alterations in sympathetic and vagal tone during tilt-table testing in 23 children with a history of syncope or frequent dizziness.: MethodsPower spectra of heart rate and blood pressure variability were analyzed using autoregressive modeling. Maximum dP/dT of systolic blood pressure and the electrical-mechanical activation time were used to assess cardiac contractility.: ResultsTilt-table testing was positive in 12 children and negative in 11. Syncope was associated with decreased heart rate, blood pressure and low-frequency (LF) power. Before episodes of syncope, systolic blood pressure dP/dT decreased, and the electrical-mechanical activation time was prolonged. The decrease in blood pressure LF power exceeded and occurred before the decrease in heart rate LF power. Despite similar early increases in LF power to the initial stress of upright tilting, no significant decline in LF power (heart rate or blood pressure) was observed during negative tilt-table tests.: ConclusionsAll of these changes considered in total provide evidence supporting the hypothesis of sympathetic withdrawal/failure, resulting in a decrease in peripheral vascular tone and cardiac contractility, which results in profound hypotension in children with NMCS. [Copyright &y& Elsevier]

SummaryThe long-term acclimation of cardiac rhythms to microgravity was studied in four astronauts aboard the Russian space station MIR during wakefulness and sleep. Sleep polygraphies were obtained between the third and the 30th day in space and, in addition, prior to mission on the ground. From each of the sleep polygraphies, beat-to-beat intervals of cardiac rhythms were determined. The response of heart period and heart period variability to the stimulus microgravity was tested during sleep across sleep stages and during waking. A lengthening of heart period by about 100 ms was found in space compared to measurements on the ground. The slowing of heart rate was more pronounced for non-REM sleep than for REM sleep. A systematic change in heart period in relation to the duration of the stay in space could not be detected. An analysis of heart period variability in the high frequency (respiratory sinus arrhythmia) band supports the hypothesis that the decrease of heart rate under microgravity is produced by an increase in parasympathetic activity. Testing the response of cardiac rhythms to microgravity across distinct behavioural states seems to be a powerful tool to investigate the cardiovascular system. [ABSTRACT FROM AUTHOR]

We investigated cardiac autonomic function in 16 patients with panic disorder before and after treatment with paroxetine using Holter ECG records. Our previous data suggest a relative increase in sympathetic activity in patients with panic disorder, especially during sleep. Data for 20 h and awake and sleep periods were analyzed using spectral analysis to quantify absolute and relative heart period variability in ultra low (ULF: <0.0033 Hz), very low (VLF: 0.0033–0.04 Hz), low (LF: 0.04–0.15 Hz) and high (HF: 0.15–0.5 Hz) frequency bands. We also obtained fractal dimensions (FD) for the 20-hour, awake and sleep time series of RR intervals. Paroxetine treatment (19.7 ± 4.7 mg/day for 105 ± 37 days) resulted in a significant improvement in the frequency and intensity of panic attacks and also on the state anxiety inventory. Paroxetine treatment produced a significant decrease of 20-hour absolute HF power, awake absolute LF power and sleep absolute HF power. There was also a significant decrease of FDs after treatment with paroxetine for the sleep period. The decrease in LF and HF powers, and sleep FD is likely due to the antimuscarinic effect of paroxetine. The decrease in day-time LF power may also be due to a decrease in relative cardiac sympathetic activity after paroxetine treatment. [ABSTRACT FROM AUTHOR]

The impact of artifacts on estimates of heart period variability were evaluated by modeling the effects of missed R-waves and spurious R-wave detections in actual and simulated heart period series. Results revealed that even a single artifact, occurring within a 128-s interbeat interval series, can impart substantial spurious variance into all commonly analyzed frequency bands, including that associated with respiratory sinus arrhythmia. In fact, the spurious variance introduced by a single artifact may be greater than that associated with true basal heart period variability and can far exceed typical effect sizes in psychophysiological studies. The effects of artifacts are not related to a specific analytical method and are apparent in both frequency and time domain analyses. Results emphasize the importance of artifact detection and resolution for studies of heart period variability. [ABSTRACT FROM AUTHOR]

Theories that psychophysiological reactivity constitutes a risk factor for coronary artery disease assume that reactivity is a consistent individual characteristic. We tested this assumption by measuring reactivity to three psychologically challenging tasks performed by 22 healthy subjects across different autonomic contexts produced by positional change. Dependent variables included heart rate (HR), low-frequency (LF; 0.04-0.15 Hz) and high-frequency (HF; 0.15-0.50 Hz) heart period variability, and the LF/HF ratio. HR (r = .44, p < .05) and LF/HF ratio (r = .48, p = .03) reactivity were modestly correlated across the different autonomic contexts, but HF and LF power reactivity were not. These findings suggest that HR reactivity to psychological challenge is a modestly consistent characteristic of individuals, despite differences in autonomic context. Although the same is true of cardiac sympathovagal balance, reactivity of HF and LF power were less consistent. [ABSTRACT FROM AUTHOR]

Central to the psychophysiologic reactivity hypothesis of the etiology of coronary artery disease is the assumption that reactivity is an individual characteristic that is stable over time. Although heart rate (HR) and blood pressure reactivity appear to meet this criterion, temporal stability of cardiac autonomic control as measured by analysis of heart period variability (HPV) has not been assessed. In this study, we tested the stability of HPV, measured in both the time and frequency domain, during a quiet, resting baseline and in response to 5-min mental arithmetic and reaction time tasks, in 20 normal subjects measured in three testing sessions during a 9-month period. Stability, assessed by the intra class correlation coefficient (ICC), was excellent for resting baseline measures of HR and HPV, with 1CCs of 0.68-0.86. However, HR and HPV reactivity to either arithmetic or reaction time tasks generally was less stable, with ICCs of 0.17-0.73, in contrast to results of previous studies demonstrating long term stability of HR responses to psychological challenge. Stability of aggregated reactivity scores was only slightly improved. Whether for individual tasks or aggregated measures, reactivity of total and low-frequency measures of HPV was moderately stable but stability of high-frequency HPV reactivity was poor. [ABSTRACT FROM AUTHOR]

Methylphenidate influenced the spontaneous autonomic activity of children diagnosed as hyperactive. There was dose response related reduction in disruptive classroom behavior monitored by the teacher ratings and a parallel decrease in a component of heart period variability, &Vcirc;, derived via spectral analysis of heart period activity. A low dose of methylphenidate, which has been reported to enhance cognitive performance, selectively increased a measure of respiratory-cardiac coupling, Cw, derived via cross-spectral analysis of respiration and heart period activity. It is hypothesized that Cw may be a quantitative manifestation of brainstem integration and &Vcirc; may be a quantitative estimate of effective vagal tone on the heart. [ABSTRACT FROM AUTHOR]

The paper focuses on the most important application problems commonly encountered in spectral analysis of short-term (less than 10 min) recordings of cardiovascular variability signals (CVSs), critically analysing the different approaches to these problems presented in the literature and suggesting practical solutions based on sound theoretical and empirical considerations. The Blackman-Tukey (BT) and Burg methods have been selected as the most representative of classical and AR spectral estimators, respectively. For realistic simulations, 'synthetic' CVSs are generated as AR processes whose parameters are estimated on corresponding time series of normal, post-myocardial infarction and congestive heart failure subjects. The problem of resolution of spectral estimates is addressed, and an empirical method is proposed for model order selection in AR estimation. The issue of the understandability and interpretability of spectral shapes is discussed. The problem of non-stationarity and removing trends is dealt with. The important issue of identification and estimation of spectral components is discussed, and the main advantages and drawbacks of spectral decomposition algorithms are critically evaluated. [ABSTRACT FROM AUTHOR]

The diagnosticity of heart rate for mental workload assessment can be improved with an autonomic space model of sympathetic and parasympathetic nervous system influences on the heart. Methods of deriving autonomic components to estimate the underlying sympathetic and parasympathetic activity needed to identify autonomic modes of control for heart period were examined. Alternative factor extraction and rotation methods were compared using data from a laboratory study that measured the electrocardiogram and impedance cardiogram simultaneously. Principal components analysis with varimax rotation was found to validly estimate the sympathetic and parasympathetic activity when computed on multiple psychophysiological measures obtained from raw EKG data. Use of the method was illustrated with single and dual mental arithmetic and secondorder compensatory manual tracking tasks. Different autonomic modes of control were found for divided attention that were not evident in heart period. Uncoupled sympathetic activation was indicated for divided attention when the mental arithmetic tasks were added to the tracking single tasks, but uncoupled parasympathetic inhibition was indicated for divided attention when the tracking tasks were added to the mental arithmetic single tasks. [ABSTRACT FROM AUTHOR]

Aims: To evaluate the acute and chronic effect of an exercise protocol of pelvic floor muscles (PFMs) contraction on the heart period (HP) and systolic arterial pressure (SAP) variabilities and baroreflex sensitivity (BRS) at rest in pregnant women; and to evaluate if this progressive exercise protocol was well-tolerated by the pregnant women studied., Methods: We evaluated 48 women at 18 weeks of pregnancy by vaginal palpation, vaginal manometry, and cardiopulmonary exercise test. They were divided in control (CG; 31.75 ± 3.91 years) and training groups (TG; 30.71 ± 3.94 years). At 19 and 36 weeks of pregnancy, electrocardiogram and noninvasive peripheral SAP data were collected at rest before and after 10 PFM contractions. TG performed PFMT from the 20th to the 36th week. HP and SAP variabilities were analyzed by spectral and symbolic analysis. The baroreflex was evaluated by cross-spectral analysis between the HP and SAP series., Results: The groups did not differ in relation to VO 2 , HP and SAP variabilities, and BRS at the beginning of the protocol. TG increased the endurance of the PFM after training. PFM contraction did not change the HP and SAP variabilities, and BRS at the 18th week. After the training, the TG presented lower SAP mean, lower BF of SAP variability, and higher BRS than CG., Conclusions: Acute PFM contractions did not alter HP and SAP variabilities and BRS, but PFMT resulted in a lower SAP mean and higher BRS in trained pregnant when compared to the untrained., (© 2020 Wiley Periodicals LLC.)