Autonomic Nervous System Indices Research Articles

Heart Rate Recovery Is Impaired After Maximal Exercise Challenge in Pediatric Sickle Cell Anemia

AbstractAbstract ▪3220▪This icon denotes a clinically relevant abstractSlow heart rate recovery (HRR) after exercise, particularly at 1 and 2 minutes during recovery, is a strong indicator of autonomic nervous system (ANS) imbalance and represents an important risk factor for increased cardiovascular morbidity and mortality in the general population. Recent evidence suggests cardiovascular ANS dysfunction and vagal tone impairment also exist in individuals with sickle cell anemia (SCA). Despite the known impact of disease burden on exercise capacity and overall fitness in SCA, post-exercise HRR has not previously been studied in this population. The objective of this study was to examine HRR in the post-exercise recovery phase following maximal exercise testing in a cohort of children and young adults with SCA. Methods We prospectively performed maximal cardiopulmonary exercise testing using a ramp, cycle ergometry protocol in 60 subjects with SCA (hemoglobin SS and S-β0 thalassemia) and 20 controls without SCA or sickle cell trait matched for race and gender. Data from standard 12-lead electrocardiography (ECG) was assessed during a 10-minute recovery phase, and HR and corrected QT (QTc) interval measured from tracings obtained at 1-minute intervals. A single investigator performed all measurements manually using leads II, V5, and V6. Final values were averaged from 3 independent measurements. The difference between maximal HR and both HR at 1-minute (ΔHR1min) and 2-minute (ΔHR2min) recovery was our primary outcome. Between-group differences were compared using Mann-Whitney U testing (IBM, SPSS V20). The relationship between ΔHR1min and exercise parameters was examined using Spearman’s rank correlation coefficient. Results Post-exercise ECG data from 58 subjects with SCA (median age 15.5 years) and 20 controls without SCA (median age 12 years) were interpretable for this analysis. A total of 30/58 (52%) and 22/58 (38%) subjects were male and on hydroxyurea, respectively. There was no significant difference in median baseline HR or QTc interval in subjects versus controls. Median peak HR was also not significantly different in the 2 groups. When compared to controls, subjects with SCA demonstrated significantly lower HR reserve (100 vs. 111 bpm, p = 0.005), representing the difference between peak and baseline HR. Impaired HRR, defined by slower declines in HR during recovery, was also evident among subjects with SCA following maximal exercise challenge. Although the absolute HR measured at each minute of recovery did not differ significantly in the 2 groups, subjects demonstrated significantly smaller median ΔHR1min (21 vs. 33 bpm, p < 0.0001) and ΔHR2min (39 vs. 51 bpm, p = 0.003), even after adjustment for age between groups. Significantly smaller ΔHR values were also noted in subjects at each minute up to 8 minutes throughout recovery. When compared to subjects not on hydroxyurea, subjects on treatment had significantly greater median ΔHR1min (25 vs. 19 bpm, p = 0.037) but similar ΔHR2min. In subjects with SCA, ΔHR1min correlated inversely with age (−0.41, p = 0.001) and directly with peak oxygen consumption (peak VO2) (0.30, p = 0.03) and oxygen delivery (ΔVO2/Δwork rate) (0.46, p < 0.0001), but not with baseline QTc interval or hemoglobin. Through mono-exponential curve fitting, we found that the time constant associated with HR decline over the first 5 minutes of recovery was greater in subjects with SCA versus controls (T = 128 sec, 95% CI [123, 134] versus 104 sec, 95% [97, 110]). Conclusions Compared to controls without SCA, children and young adults with SCA demonstrate impaired HRR following maximal cardiopulmonary exercise testing, as evidenced by smaller decrements in HR at 1 and 2 minutes during recovery and exponential time constants that indicate a longer period of time over which HR declines. Slower HRR is also associated with decreased fitness and measures of oxygen delivery during exercise testing in subjects with SCA. Although the mechanisms are not well understood, prolonged HRR in this population may in part be explained by ANS imbalance, suggesting either inadequate sympathetic withdrawal or suboptimal parasympathetic reactivation in the post-exercise period. Future studies should focus on delineating the role of the ANS in post-exercise HRR and assessing the prognostic potential of this marker as it relates to disease severity and outcomes in SCA. Disclosures:No relevant conflicts of interest to declare.

Yoga Nidra Relaxation Increases Heart Rate Variability and is Unaffected by a Prior Bout of Hatha Yoga

The measurement of heart rate variability (HRV) is often applied as an index of autonomic nervous system (ANS) balance and, therefore, myocardial stability. Previous studies have suggested that relaxation or mind-body exercise can influence ANS balance positively as measured by HRV but may act via different mechanisms. No studies, to the authors' knowledge, have examined the acute response in HRV to interventions combining relaxation and mind-body exercise. The objective of this study was to compare the acute HRV responses to Yoga Nidra relaxation alone versus Yoga Nidra relaxation preceded by Hatha yoga. This was a randomized counter-balanced trial. The trial was conducted in a university exercise physiology laboratory. Subjects included 20 women and men (29.15±6.98 years of age, with a range of 18-47 years). Participants completed a yoga plus relaxation (YR) session and a relaxation only (R) session. The YR condition produced significant changes from baseline in heart rate (HR; beats per minute [bpm], p<0.001) and indices of HRV: R-R (ms, p<0.001), pNN50 (%, p=0.009), low frequency (LF; %, p=0.008) and high frequency (HF; %, p=0.035). The R condition produced significant changes from baseline in heart rate (bpm, p<0.001) as well as indices of HRV: R-R (ms, p<0.001), HF (ms(2), p=0.004), LF (%, p=0.005), HF (%, p=0.008) and LF:HF ratio (%, p=0.008). There were no significant differences between conditions at baseline nor for the changes from baseline for any of the variables. These changes demonstrate a favorable shift in autonomic balance to the parasympathetic branch of the ANS for both conditions, and that Yoga Nidra relaxation produces favorable changes in measures of HRV whether alone or preceded by a bout of Hatha yoga.

Effects of radiation emitted from mobile phones on short- term heart rate variability parameters

In this study, the effects of radiation emitted from mobile phone (MP) on heart rate variability (HRV) which is accepted a non-invasive indicator of autonomic nervous system (ANS) were investigated with considering the deficiency of previous studies. A randomized controlled study has been designed and utilized with 30 young and healthy volunteers. During the experiment that had three periods, the electrocardiogram (ECG) and respiration signals were recorded and MP was attached to subjects' right ear with a bone. Ten subjects selected randomly were exposed to high -level radiation during the second period (Experimental Group 1). Ten of others were exposed during the third period with maximum level radiation (Experimental Group 2). Ten records were also made while MP was closed as a control. Short -term HRV parameters were obtained and repeated measures ANOVA and suitable post-hoc tests applied to the results. According to the results of the repeated measures ANOVA; there were no significant main effects of groups. However, there were some significant differences in measuring time periods and groups*period interactions. The post-hoc tests showed that mean R to R interval and HF power are significantly changed by maximum radiation emitted from MP. Due to the radiation emitted from MPs at maximum power, some changes may occur in HRV parameters that are associated with increased parasympathetic activity. But, the level of these changes is similar to daily activities as excitement, and stand up.

Effect of pain on autonomic nervous system indices derived from photoplethysmography in healthy volunteers

Photoplethysmographic pulse wave amplitude (PPGA) and heart rate (HR) can be used to measure cold, nociception-induced autonomic responses, or both. The aim of our study was to correlate the intensity of experimental pain to changes in physiological variables reflecting the autonomic nervous system response to pain. PPGA, HR, and subjective measurements of pain intensity were measured in 29 healthy male volunteers during two heat stimuli (43°C and 48°C) and the cold pressor test (CPT). Surgical pleth index (SPI), autonomic nervous system state (ANSS), and ANSS index (ANSSi) were calculated using PPGA and HR. Pain intensity scores increased on the average by 1.6, 3.5, and 8.1 for the 43°C, 48°C, and CPT stimuli, respectively. The pain intensity scores for all three stimuli groups were significantly different from each other (P<0.001). All three stimuli changed HR, PPGA, SPI, ANSS, and ANSSi values significantly from their respective baseline values (P<0.001 for all). Heat stimuli-induced pain intensity did not correlate with the magnitude of the respective changes in HR, PPGA, SPI, ANSS, and ANSSi. CPT-induced pain intensity correlated with the magnitude of the respective changes in HR, PPGA, SPI, ANSS, and ANSSi. PPGA, ANSSi, ANSS, and SPI differentiated between heat and cold stimuli-induced pain. All three thermal stimuli produced a significant change in photoplethysmograph-derived parameters. All photoplethysmograph-derived parameters appear to be suitable to study autonomic nervous system activation.

Evaluation of the effects of mediastinal radiation therapy on autonomic nervous system

In this prospective study, the effects of mediastinal radiation therapy (RT) on autonomic nervous system (ANS) were investigated by heart rate variability (HRV) analysis that is accepted as a non-invasive indicator of ANS. Study was performed with the eligible patients had a histopathologically confirmed diagnosis of malignant disease with no known congestive heart failure, coronary heart disease, hypertension, valvular cardiac disease or arrhythmia history. Electrocardiograms of 14 voluntary patients were recorded for duration of 5 min just before and after irradiation for the first and the 15th fractions. ANS-related HRV analysis parameters were calculated as which were recommended by Task Force of ESC/NASPE (Circulation 93:1043-1065, 1996). HRV parameters that belong to pre- and post-RT treatment of patients were compared statistically. We found that there is not effect of single-dose radiation on HRV parameter. The mean RRI (782.29 ± 115.65-738.93 ± 111.01, P < 0.014) and HF power of HRVs PSD (156.94 ± 229.37-60.71 ± 77.99, P < 0.045) decreased, and LF/HF ratio (1.38 ± 0.79-2.03 ± 1.25, P < 0.039) increased significantly with 28-Gy external radiation dose. As the effect of cumulative dose was investigated on HRV parameters, the above changes were continued to increase with 30-Gy external radiation dose. We found that mediastinal RT involving heart directly in the radiation field decreased vagal and sympathetic ANS activities, and autonomic balance shifted toward sympathetic dominance.

Development of resting cardiovascular activity during the first 2 years of life differs in breastfed and formula‐fed boys and girls

To investigate whether early infant diet influences cardiovascular development we recorded resting heart‐rate (HR) at 3, 6, 9, 12, and 24 mo in awake healthy children who were breastfed (BF) or fed milk formula (MF) or soy formula (SF) during infancy (n = 83–146/group/age). HR, and indices of autonomic nervous system (ANS) sympathetic [low frequency power (Plf: .04–.15 Hz)] and parasympathetic activity [high frequency power (Phf: .15–.5 Hz)] were determined from power spectral analyses of digitized, artifact‐free recordings and analyzed using ANOVAs with post‐hoc t‐tests. HR decreased and Plf and Phf increased for all groups across the study period. Few within‐group gender differences were found [6 mo Plf: MF girls &gt; boys, p &lt; .05; 12 and 24 mo HR: SF girls &gt; boys, both p &lt; .05]. There were three important diet‐related findings: 1) levels of Plf and Phf were higher in BF than formulafed (FF) groups after 6 mo (p &lt; .001); 2) SF and MF infants did not differ on HR measures; 3) and, group differences were modulated by gender [greater Plf and Phf in FF than BF girls from 9–24 mo (p &lt; .02) and in FF than BF boys at 12 and 24 mo (p &lt; .01)]. Baseline levels of ANS activity influence interactions between the central nervous system and ANS that regulate attention, emotion, cognition and behavior. The present findings suggest early infant diet may contribute to individual differences in these functions.Supported by USDA ARS CRIS 6251‐51000‐006‐03S

Effect of Partition Board Color on Mood and Autonomic Nervous Function

The purpose of this study was to evaluate the effects of the presence or absence (control) of a partition board and its color (red, yellow, blue) on subjective mood ratings and changes in autonomic nervous system indicators induced by a video game task. The increase in the mean Profile of Mood States (POMS) Fatigue score and mean Oppressive feeling rating after the task was lowest with the blue partition board. Multiple-regression analysis identified oppressive feeling and error scores on the second half of the task as statistically significant contributors to Fatigue. While explanatory variables were limited to the physiological indices, multiple-regression analysis identified a significant contribution of autonomic reactivity (assessed by heart rate variability) to Fatigue. These results suggest that a blue partition board would reduce task-induced subjective fatigue, in part by lowering the oppressive feeling of being enclosed during the task, possibly by increasing autonomic reactivity.

Sahaja yoga: A unique adjunctive approach for the management of cardiac arrhythmias?

Sahaja yoga (SY) is a unique meditative technique that has both spiritual and mundane aspects. Although SY has generally been regarded as a practice of spiritual and mental well-being, it is also closely associated with a variety of subtle influences on some organ systems. SY has been suggested to have some beneficial effects in a variety of psycho-somatic diseases [1]. Besides subtle effects throughout the whole body, sympatho-vagal regulation associated with SY technique has been proposed as the direct evidence of its beneficial effects on some organ systems including cardiovascular system etc. As describedbelow,SYpracticemaybe regarded as anadjunctiveoption for the management of a variety of cardiac arrhythmias primarily on the basis of its potential effects on the autonomic nervous system largely through unknown mechanisms. Autonomic imbalance including hyperactivation of sympathetic system has been known to be associated with the occurrence of life threatening conditions including acute coronary syndromes (ACS) and may directly trigger malign arrhythmic events in arrhythmia-prone subjects [2]. Hyperactivation of sympathetic system is also well known to prolong QT interval, and impair some indices of autonomic nervous system including heart rate variability (HRV) and heart rate turbulence (HRT) etc. thatmay serve asmarkers of arrhythmogenesis in susceptible subjects. Therefore, therapeutic strategies aiming at management of autonomic imbalance on topof conventional anti-arrhythmic therapy in arrhythmia-prone subjects have gained particular importance in the recent years. However, therapeutic options including beta blockers, sympathetic ganglion blockage etc. have limited value for the management of autonomic imbalance as these approaches generally

Family conflict, autonomic nervous system functioning, and child adaptation: State of the science and future directions

The family is one of the primary contexts of child development. Marital and parent-child conflict (family conflict) are common and predict a wide range of negative behavioral and emotional outcomes in children. Thus, an important task for developmental researchers is to identify the processes through which family conflict contributes to children's psychological maladjustment, as well as vulnerability and protective factors in the context of family conflict. In the current paper, we aim to advance a conceptual model that focuses on indices of children's autonomic nervous system (ANS) functioning that increase vulnerability or provide protection against psychological maladjustment in the context of family conflict. In doing so, we provide a selective review that reflects the state of the science linking family conflict, children's ANS activity, and child psychological adjustment, and offer directions and guidance for future research. Our hope is to accelerate research at the intersection of family conflict and ANS functioning to advance understanding of risk and resilience among children.

Heavy alcohol use, rather than alcohol dependence, is associated with dysregulation of the hypothalamic–pituitary–adrenal axis and the autonomic nervous system

BackgroundHeavy alcohol use as well as alcohol dependence (AD) have been associated with dysregulation of the hypothalamic–pituitary–adrenal (HPA)-axis and the autonomic nervous system (ANS). However, the relative contribution of alcohol use and AD is unclear. MethodsBaseline data were derived from 2947 persons of the Netherlands Study of Depression and Anxiety (NESDA), including non-drinkers (n=498), moderate drinkers (n=2112) and heavy drinkers (n=337). We also distinguished between persons with no lifetime DSM-IV AD (n=2496), remitted AD (>1 year; n=243), and current AD (≤1 year; n=208). ANS measures included ECG-based heart rate (HR), respiratory sinus arrhythmia (RSA, high RSA reflecting high cardiac parasympathetic control) and pre-ejection period (PEP, high PEP reflecting low cardiac sympathetic control). HPA-axis measures included the cortisol awakening response (area under the curve with respect to the ground [AUCg] and increase [AUCi]), evening cortisol and a 0.5mg dexamethasone suppression test, all measured in saliva. ResultsHeavy drinkers showed higher basal cortisol levels (AUCg: p=.02; evening cortisol: p=.006) and increased cardiac sympathetic control (higher HR: p=.04; lower PEP: p=.04) compared to moderate drinkers. Persons with current or remitted AD did not differ from persons without lifetime AD on any of the HPA-axis or ANS indicators (all p>.33). Similar patterns of HPA-axis and ANS activity across alcohol use groups were found in persons with and without lifetime AD. ConclusionsOur findings suggest that current heavy alcohol use, rather than current or remitted AD, is associated with hyperactivity of the HPA-axis and increased cardiac sympathetic control.

Serum HDL-C is Positively Related to CVRR as an Index of ANS, which Relation is Attenuated by Rosuvastatin

An impairment of the Autonomic Nervous System (ANS) has been found in chronic heart failure (CHF). Decreased serum HDL-Cholesterol (HDL-C) level is associated with the progression of atherosclerosis. Few papers report that HDL-C is associated with HRV, which reflects ANS. MIBG is a tool to evaluate ANS, which isn't usually done in clinic. The coefficient of variation of the R-R interval (CVRR) could be used instead of MIBG, which could be obtained easily, even in clinic. So I studied the possible direct correlation between CVRR as one of the parameters of HRV on behalf of ANS and serum HDL-C levels in cardiovascular patients such as hypertention, angina pectoris and heart failure.

Autonomic Nervous System Dysfunction and Inflammation Contribute to the Increased Cardiovascular Mortality Risk Associated With Depression

To investigate prospectively whether autonomic nervous system (ANS) dysfunction and inflammation play a role in the increased cardiovascular disease (CVD)-related mortality risk associated with depression. Participants in the Cardiovascular Health Study (n = 907; mean age, 71.3 ± 4.6 years; 59.1% women) were evaluated for ANS indices derived from heart rate variability (HRV) analysis (frequency and time domain HRV, and nonlinear indices, including detrended fluctuation analysis (DFA(1)) and heart rate turbulence). Inflammation markers included C-reactive protein, interleukin-6, fibrinogen, and white blood cell count). Depressive symptoms were assessed, using the 10-item Centers for Epidemiological Studies Depression scale. Cox proportional hazards models were used to investigate the mortality risk associated with depression, ANS, and inflammation markers, adjusting for demographic and clinical covariates. Depression was associated with ANS dysfunction (DFA(1), p = .018), and increased inflammation markers (white blood cell count, p = .012, fibrinogen p = .043) adjusting for covariates. CVD-related mortality occurred in 121 participants during a median follow-up of 13.3 years. Depression was associated with an increased CVD mortality risk (hazard ratio, 1.88; 95% confidence interval, 1.23-2.86). Multivariable analyses showed that depression was an independent predictor of CVD mortality (hazard ratio, 1.72; 95% confidence interval, 1.05-2.83) when adjusting for independent HRV and inflammation predictors (DFA(1), heart rate turbulence, interleukin-6), attenuating the depression-CVD mortality association by 12.7% (p < .001). Autonomic dysfunction and inflammation contribute to the increased cardiovascular mortality risk associated with depression, but a large portion of the predictive value of depression remains unexplained by these neuroimmunological measures.

Enhancing the deceleration capacity index of heart rate by modified-phase-rectified signal averaging

Deceleration capacity (DC) of heart rate is a novel indicator of autonomic nervous system (ANS) activity. In this paper, we proposed a modified DC index based on improved phase-rectified signal averaging (PRSA) algorithm. Sinusoidal analysis is applied to elucidate the rationality of the improved PRSA. Then the validity of the modified DC is verified by the databases of chronic heart failure (CHF) patients and control group. Both the conventional and modified DCs are significantly lower in CHF patients than that in the control group (2.12 +/- 2.98 vs. 6.34 +/- 1.92 ms, P < 0.0001 and 5.45 +/- 2.48 vs. 10.64 +/- 1.76 ms, P < 0.0001, respectively). And the modified DC provides higher accuracy in distinguishing CHF than the conventional one (87.4 vs. 82.1%). The results indicate that the suggested technique enhances the performance of PRSA and improves the efficiency of DC in assessing ANS activity in CHF patients.

Exploratory Study of Stress-Buffering Response Patterns from Interaction with a Therapy Dog

ABSTRACTThis exploratory study builds on existing research on the physiological stress response to human–animal interactions in a non-clinical sample of adult dog-owners interacting with their own or an unfamiliar therapy dog under similar conditions. Participants were therapy-dog owners (TDO group; n = 5) interacting with their own dogs and dog owners interacting with an unfamiliar therapy dog (AAA group; n = 5). Following a 30minute baseline period, participants completed a stress task followed by a 30-minute dog interaction and then watched a neutral video for 60 minutes. The outcome variable of interest was the bio-behavioral stress response, measured by systolic and diastolic blood pressure (SBP, DBP), heart rate (HR), salivary cortisol, salivary alpha-amylase, and self-report. Trait anxiety and attitudes toward pets were assessed as moderating variables. Results revealed consistent physiological patterns, showing modest increases with the stressor and decreases from baseline following the intervention, for salivary cortisol, SBP, DBP, HR, and self reported anxiety and stress for both groups. In general, although the TDO group tended to perceive less stress and anxiety during the intervention than the AAA group, greater reductions in physiological measures were observed in the AAA group. Positive attitudes toward pets in the total sample of dog owners were associated with decreased levels of self-reported stress (p < 0.05), salivary cortisol, and SBP, while higher levels of trait anxiety were associated with higher levels of salivary cortisol (p < 0.05). In addition, higher levels of trait anxiety were associated with lower levels of autonomic nervous system indicators of stress (HR; SBP, p < 0.05; DBP, p < 0.05). Results support a buffering effect on the stress response associated with owners interacting with their dogs that may extend to interactions with unfamiliar therapy dogs in AAA, and supports the need for replication studies with larger sample sizes.

Pressure-induced performance decrement in verbal fluency task through prefrontal overactivation: A near-infrared spectroscopy study

Pressure-induced performance decrement in verbal fluency task through prefrontal overactivation: A near-infrared spectroscopy study

Noninvasive Psychophysiological Ambulatory Recordings

Rapid technical developments have greatly facilitated noninvasive 24-hour recording of physiological signals at relatively low costs, including blood pressure, activity of the autonomic nervous system, respiratory behavior, and activity of the hypothalamic-pituitary-adrenocortical axis. Ambulatory noninvasive recordings can be used to study the baseline levels of these physiological variables as well as their reactivity to naturalistic stressors. Levels and reactivity can be compared across groups differing in exposure to risk factors (e.g., stress, genotypes) or used to sharpen the clinical profile of individual subjects (e.g., in panic or somatoform disorders). The focus of the current paper is on the importance of a priori choices in study design and data analysis strategies when ambulatory recording specifically targets the reciprocal relationship between physiological and psychological events. These choices are illustrated with ambulatory-assessed indices of the cardiac autonomic nervous system, blood pressure, respiration, and cortisol secretion.

Ambulatory Assessment

Ambulatory Assessment

Abstract 5647: Autonomic Nervous System Dysregulation in Implantable Cardioverter Defibrillator Patients with Depression and Anxiety

Background : Autonomic nervous system (ANS) dysregulation increases risk of ventricular arrhythmias in patients with implantable cardioverter defibrillators (ICD). ANS dysregulation is common in depression and anxiety, but the relationship between these psychological factors and ANS dysregulation has not been investigated in ICD patients. Methods : ANS indices reflecting parasympathetic control of heart rate were obtained using heart rate variability (HRV) analyses in 44 ICD patients with documented coronary artery disease (age 62±9 yrs; ejection fraction 35.9±12.7%). Ambulatory 24-hr ECG recordings were used to calculate HRV (rMSSD and pNN50). Depression was assessed using the Beck Depression Inventory (BDI) and anxiety using the Taylor Manifest Anxiety Scale (TMA). Validated cut-off scores were used (depression: BDI≥10; anxiety: TMa≥9), and data were analyzed using Analysis of Variance. Results : ICD patients with depression symptoms (n=12) had significantly lower HRV markers of ANS parasympathetic activity (rMSSD:15.2±5.7 ms vs. 25.0±13.4 ms, p=0.002; pNN50:1.8±2.7% vs. 5.6±5.7%, p=0.006) than patients with low depression symptoms (n=32). High anxiety (n=10) was related to lower rMSSD (p =0.014). Comorbid depression and anxiety was associated with substantial HRV reduction (p&lt;0.001) (Figure ). Conclusion : Depression and anxiety in ICD patients are associated with autonomic nervous system dysregulation (reduced HRV markers of parasympathetic control). Reduced parasympathetic activity may therefore contribute to the elevated risk of life-threatening cardiac arrhythmias in ICD patients with depression and anxiety. Figure 1. RMSSD among depression/anexity groups

Effects of strenuous exercise on autonomic nervous system activity in sickle cell trait carriers

This study compared the nocturnal autonomic nervous system (ANS) activity in seven sickle cell trait (SCT) carriers and six subjects with normal hemoglobin in response to exercise Sympathetic and parasympathetic indices of nocturnal ANS were measured in the two groups before and 24 and 48 h after a strenuous exercise consisting of the repetition of three maximal exercise bouts. Global ANS activity decreased 24 h after exercise in both groups and was lower before as well as after exercise in SCT carriers. Indices of parasympathetic activity were lower in SCT carriers at all times, indicating a persistent sympatho-vagal imbalance. Exercise did not cause a rebound in parasympathetic activity in either group, but a rebound was noted for sympathetic index values two days after exercise in SCT group only. The ANS activity was generally lower, and the sympatho-vagal imbalance greater, in SCT carriers compared with control subjects irrespective of exercise and could increase the risk for medical complications in this population.

Autonomic cardiac control of very preterm newborns: A prolonged dysfunction

Background Autonomic nervous system (ANS) activity is fundamental to infant health. ANS activity of preterm newborns seems to be reduced at term equivalent age, but follow-up of ANS activity has rarely been performed in that population during the weeks after birth. The aim of the study was to perform such a follow-up in preterm newborns of different gestational ages, up to their term equivalent ages. Methods Prolonged electrocardiographic recordings were prospectively performed in a group of 39 premature newborns, each week, up to term equivalent age before discharge. Control values were obtained from a group of 19 full-term newborns, recorded at the first week of their life. ANS indices were calculated from recordings during quiet sleep periods by spectral-domain analysis (Fourier transform): Ptot (total power), VLF (very low-frequencies), LF (low-frequencies), HF (high-frequencies), LF/HF ratio, LFnu (normalized low-frequencies) and HFnu (normalized high-frequencies) values. Results Ptot, VLF, LF and HF were significantly lower in the preterm group at birth compared to the control group, while LFnu, HFnu and LF/HF ratio were not significantly different. The results were similar when comparing the control group to any ANS values at a given post-natal corrected age of preterm newborns. Furthermore, preterm newborns did not demonstrate any significant increase in ANS values from birth to theoretical term. Conclusion The finding of substantial reduced ANS activity and failure of maturation in preterm infants up to term equivalent age needs confirming by other research groups, and mechanisms and implications for infant health explored.