Standard Deviation Of RR Intervals Research Articles

Acute mental stress and surgical performance.

BackgroundStress has been shown to impact adversely on multiple facets critical to optimal performance. Advancements in wearable technology can reduce barriers to observing stress during surgery. This study aimed to investigate the association between acute intraoperative mental stress and technical surgical performance.MethodsContinuous electrocardiogram data for a single attending surgeon were captured during surgical procedures to obtain heart rate variability (HRV) measures that were used as a proxy for acute mental stress. Two different measures were used: root mean square of successive differences (RMSSD) and standard deviation of RR intervals (SDNN). Technical surgical performance was assessed on the Operating Room Black Box® platform using the Generic Error Rating Tool (GERT). Both HRV recording and procedure video recording were time‐stamped. Surgical procedures were fragmented to non‐overlapping intervals of 1, 2 and 5 min, and subjected to data analysis. An event was defined as any deviation that caused injury to the patient or posed a risk of harm.ResultsRates of events were significantly higher (47–66 per cent higher) in the higher stress quantiles than in the lower stress quantiles for all measured interval lengths using both proxy measures for acute mental stress. The strongest association was observed using 1‐min intervals with RMSSD as the HRV measure (P < 0·001).ConclusionThere is an association between measures of acute mental stress and worse technical surgical performance. Further study will help delineate the interdependence of these variables and identify triggers for increased stress levels to improve surgical safety.

Heart rate variability in type 2 diabetes mellitus: A systematic review and meta-analysis

Background Cardiac autonomic neuropathy in type 2 diabetes mellitus (T2DM) patients is associated with high cardiovascular mortality. Heart rate variability (HRV) is the gold standard to measure cardiac autonomic neuropathy. We aimed to conduct a systematic review and meta-analysis to evaluate the impact of T2DM on HRV parameters. Methods Main databases were searched on 1st October 2017 using the keywords “diabetes” AND (“heart rate variability” OR “HRV”). Included articles reported HRV parameters in T2DM patients and healthy controls measured during 24 hours. Measurements of HRV retrieved were: RR intervals, standard deviation of RR intervals (SDNN), percentage of adjacent NN intervals differing by more than 50 milliseconds (pNN50), square root of the mean squared difference of successive RR intervals (RMSSD), total power, low frequency (LF), high frequency (HF) and LF/HF ratio. Results We included 1356 T2DM patients and 1576 healthy controls. T2DM patients had significantly (P Conclusions T2DM was associated with an overall decrease in the HRV of T2DM patients. Both sympathetic and parasympathetic activity were decreased, which can be explained by the deleterious effects of altered glucose metabolism on HRV, leading to cardiac autonomic neuropathy.

Determination of Optimal Heart Rate Variability Features Based on SVM-Recursive Feature Elimination for Cumulative Stress Monitoring Using ECG Sensor.

Routine stress monitoring in daily life can predict potentially serious health impacts. Effective stress monitoring in medical and healthcare fields is dependent upon accurate determination of stress-related features. In this study, we determined the optimal stress-related features for effective monitoring of cumulative stress. We first investigated the effects of short- and long-term stress on various heart rate variability (HRV) features using a rodent model. Subsequently, we determined an optimal HRV feature set using support vector machine-recursive feature elimination (SVM-RFE). Experimental results indicate that the HRV time domain features generally decrease under long-term stress, and the HRV frequency domain features have substantially significant differences under short-term stress. Further, an SVM classifier with a radial basis function kernel proved most accurate (93.11%) when using an optimal HRV feature set comprising the mean of R-R intervals (mRR), the standard deviation of R-R intervals (SDRR), and the coefficient of variance of R-R intervals (CVRR) as time domain features, and the normalized low frequency (nLF) and the normalized high frequency (nHF) as frequency domain features. Our findings indicate that the optimal HRV features identified in this study can effectively and efficiently detect stress. This knowledge facilitates development of in-facility and mobile healthcare system designs to support stress monitoring in daily life.

P129. Morphological changes of the vagus nerve are accompanied by changes of heart rat

Background The physiological regulation of the heart is determined by the interaction between the sympathetic and the parasympathetic nervous system. The parasympathetic efferent fibers originate from the nucleus ambiguous and the dorsal motor nucleus. Together with the afferent fibers from the spinal trigeminal nucleus and the solitary nucleus they form the vagus nerve (VN). The measurement of the heart rate variability (HRV) enables to assess the relative impact of the parasympathetic and sympathetic innervation on the heart with different impact of the right and left VN. Whether morphological changes of the right and left VN are accompanied by functional changes as indicated by altered HRV parameters is currently unknown. Methods Measurement of HRV was performed in 65 healthy subjects (38 women; mean age 52 years, range 23–76 years). RR intervals were measured on electrocardiograms at normal breathing for 10 min under resting and in supine position via the computer-based system ProSciCard (MedSet Medizintechnik GmbH, Hamburg, Germany). Besides heart rate at rest, several indices of the HRV were automatically computed: the standard deviation of RR-intervals (SDNN, higher index indicates higher variability), the root mean square of successive differences (RMSSD, estimate of short-term components of HRV), the number of all RR-intervals/maximal frequency (HRV index, higher index indicates higher variability). In addition, power spectral analyses in the low (ln(LF), 0.05–0.15 Hz) and in the high frequency spectrum (ln(HF), 0.15–0.5 Hz) were performed and the low frequency/high frequency ratio (ln(LF/HF) ratio) as a marker of sympatho-vagal interaction was calculated. In addition, the cross-sectional area (CSA) of the VN was sonographically measured at the level of the thyroid gland. Besides the lateralized assessment of the VN CSA, the ratio between the CSA of the right and left VN was calculated (VN-symmetry index). Results There was no correlation between the right or left VN CSA and heart rate at rest or any other HRV parameter in a correlation analyses adjusted for age and sex. However, we found a correlation between the VN-symmetry index and SDNN (0.30, p = 0.029), RMSSD (0.30, p = 0.027), HRV index (0.26, p = 0.055) and the ln(HF) (0.24, p = 0.085). Conclusions In a cohort of healthy subjects, morphological changes of both VN as represented by the VN-symmetry index are accompanied by functional changes mainly involving the parasympathetic nervous system. Further studies should examine whether this correlation is altered in (e.g.) neurodegenerative or inflammatory diseases involving the VN.

Esmolol indirectly stimulates vagal nerve activity in endotoxemic pigs

BackgroundThere is an increasing interest in beta-blockade as a therapeutic approach to sepsis following consistent experimental findings of attenuation of inflammation and improved survival with beta1 selective antagonist. However, the mechanism of these beneficial effects remains very uncertain. Thus, this study is aimed at investigating the effects of a beta-1 selective blockade on sympathetic/parasympathetic activity in endotoxin-challenged pigs using heart rate variability. The hypothesis is that an adrenergic blockade could promote parasympathetic activity. Indeed, the increase of parasympathetic activity is a mechanism recently described as beneficial in septic states.MethodsFifty-one endotoxin-challenged pigs were studied. After 30 min of endotoxin infusion and 30 min of evolution without intervention, the pigs were randomly assigned the placebo or esmolol treatment and were observed for 200 min. Overall heart rate variability was assessed continuously, in the temporal domain by standard deviation of RR intervals (SDNN, ms),and in the frequency domain by spectral powers of low frequency (LF, ms2 × 103/Hz) and high frequency (HF, ms2 × 103/Hz) bands.ResultsVariations of power in these frequency bands were interpreted as putative markers of sympathetic (LF) and parasympathetic (HF) activity. In LPS treated animals, Esmolol did not increase SDNN, but instead decreased LF and increased HF power.ConclusionThese spectral modifications associated to a beta-blocker treatment after an endotoxemic challenge are interpreted as a significant decrease of sympathetic activity and an indirect increase of vagal autonomic tone.

Fifteen minutes daily physical activity may be a new best target in older adults: The proof cohort study

Aging is associated with a decrease of the activity level of the Autonomic Nervous System (ANS). With aging, the decline in activity coincides with the occurrence of deaths. It is well established that physical activity (PA) is an efficient strategy for successful aging. This work focuses on the regulation of the ANS by PA and their close relationship in the prevention of cardiovascular events. The PROOF (PROgnostic indicator OF cardiovascular and cerebrovascular events) cohort study was designed in 2001 to prospectively assess the predictive value of ANS activity level among a healthy retired French population. PA was assessed every 4 years with self-administered questionnaires and was measured in Metabolic Equivalent of Task (MET)-minutes. We looked at the associated risk of mortality for four categories of weekly PA in MET-minutes, defined as inactive (< 1 MET-min/wk), low (1–499 MET-min/wk), medium (500–999 MET-min/wk) or high (≥ 1000 MET-min/wk). ECG recording were performed every 4 years and SDNN (standard deviation of RR intervals) reflected the regulation of the heart rate by the ANS. Out of the 1011 65-year-old subjects initially included in 2001, the 15 years of follow-up has been currently completed for 688 (68%) subjects, and 89 (9%) deaths were reported. The relative risk of death (all causes) was reduced by 22% (RR = 0.78 [95% CI: 0.25–0.90], P < 0.05) for subjects achieving a low dose of PA compared with an inactive lifestyle. For active subjects even for a low dose of PA, SDNN was stable compared with inactive subjects during the follow-up. Our data from the PROOF cohort suggest that the positive effects of a low dose of PA could thus be, at least partially, explained by its protective impact on ANS activity. ANS up-regulation by the low dose of PA might thus be key for a successful aging.

Badanie przesiewowe pacjentów z chorobą wieńcową w kierunku obturacyjnego bezdechu sennego i ocena jego wpływu na zmienność rytmu zatokowego

Introduction. Obstructive sleep apnea (OSA) is one of the most common sleep disorders, which affects 4% of men and 2% of women in the world population. The disorder can be diagnosed in men and women of all ages; however, its incidence increases with age. Patients with OSA experience increased levels of sympathetic nervous system activity, which is evidenced by the increased catecholamines secretion. They are at an increased risk of developing complications of coronary heart disease (CHD). The aim of the study was to evaluate the influence of results of screening for OSA on the activity of the sympathetic and parasympathetic nervous systems within the scope of selected heart rate variability (HRV) parameters (time-domain and frequency-domain analyses of the HRV) in patients with CHD. Material and methods. Holter recordings of 146 patients aged 43–78 (106 of whom were men) were analysed retrospectively. The patients were divided into four groups on the basis of the estimated apnea–hypopnea index (eAHI), assessed by means of 24-hour recordings of electrocardiogram with Lifescreen Apnea software: &lt; 5 (control group), from 5 to &lt; 15 (mild), from 15 to &lt; 30 (moderate) and ≥ 30 episodes (severe). For each patient, a profile of power spectrum alterations was developed for low frequency (LF) and high frequency (HF) in 60-minute periods between 10 p.m. and 6 a.m. and standard deviation of RR intervals (SDNN) and root mean square of successive differences (rMSSD) values were calculated. The power spectrum in the consecutive one-hour periods was averaged in both groups. In view of the right-skewed distribution of data, the average power spectra were converted into natural logarithms. In order to assess the significance of variations, the natural logarithms of the average values were compared using the univariate analysis of variance (ANOVA). Results. In the examined groups, there were statistically significant differences in the HF band of power spectrum between the control group and the group of patients with mild OSA (p &lt; 0.01), those with severe OSA (p &lt; 0.01) and also between the group with mild and moderate OSA (p &lt; 0.01). In the LF band of power spectrum, the only difference was seen between the group of patients with mild OSA and those with moderate OSA (p &lt; 0.01). In the time-domain analysis of HRV (SDNN, rMSSD), no statistically significant differences between the groups were observed. Conclusions. High frequency band of power spectrum [HF] in frequency-domain HRV analysis could be a more effective parameter to distinguish patients with mild OSA (from 5 to &lt; 15) and severe OSA (≥ 30) in patients suffering from CHD, than the power spectrum for LF or SDNN and rMSSD.

Bitemporal seizure spread and its effect on autonomic dysfunction

ObjectiveAutonomic dysregulation is a possible pathomechanism of sudden unexpected death in epilepsy (SUDEP). Cardiac arrhythmias and autonomic symptoms are most commonly associated with seizures arising from the temporal lobes. The aim of this study was to investigate whether simultaneous seizure activity in both temporal lobes affects the autonomic nervous system differently from seizure activity in one temporal lobe as assessed by heart rate variability (HRV). MethodsElectrocardiography (ECG) and intracranial electroencephalography (iEEG) data from 13 patients with refractory temporal lobe epilepsy who had seizures that propagated electrically from one temporal lobe to the other during video-EEG–ECG monitoring were retrospectively reviewed. The time domain, frequency domain, and nonlinear parameters of HRV were evaluated by analyzing 4-minute-long ECG epochs, sampling from baseline, preictal and postictal periods as well as epochs constituting unitemporal and bitemporal ictal activity. ResultsHeart rate was significantly higher during bitemporal ictal activity compared with all other time points. The time domain and nonlinear parameters of HRV were significantly decreased during bitemporal activity compared with baseline, and multiple components of HRV (standard deviation of RR intervals (SDNN), coefficient of variation (CV), root mean square of successive differences (RMSSD), and standard deviation of short-term variability (SD1)) were significantly lower during bitemporal activity compared with unitemporal activity. Frequency domain analysis showed no significant differences. ConclusionThis study shows that bitemporal seizure activity significantly increases heart rate and decreases HRV, indicating increased autonomic imbalance with a shift towards sympathetic predominance, and this may increase the risk of SUDEP.

Caffeine and Citrate Aurantium Supplementation Alter Resting Cardiac Autonomic Function but Not During Recovery

PURPOSE: To examine the combined effects of the pre exercise complex Citrate Aurantium and Caffeine (CA+C) on cardiac autonomic activity following ingestion and immediately after high-intensity anaerobic exercise in habitual caffeine users. METHODS: Ten physically active males (25.1± 3.9 years; mass 78.7± 9.5kg) who habitually consume caffeine (≥ 1 serving a day [95mg] 4 days a week) participated. This was a double-blind crossover design, where either a CA+C or a placebo capsule was consumed followed by a 45-min ingestion period, a repeated Wingate protocol, and a 45-min recovery period. Cardiac autonomic activity was assessed through Heart Rate (HR), plasma epinephrine (E) and norepinephrine (NE), and markers of Heart Rate Variability (HRV): root mean squared of successive R-R differences (RMSSD); Standard Deviation of R-R intervals (SDNN); High-Frequency (HF); Low-Frequency (LF); and its ratio (LF:HF). Markers were taken at four time points: pre-Ingestion (PRE-ig), 40-45-min post (Post- ig); Wingate recovery (PRE-rcv), 40-45-min post recovery (Post-rcv). RESULTS: Markers that violated normality were naturally log transformed prior to further analysis (ln). Pre-planned comparisons were performed to assess differences between pre and post time points as well as the corresponding time point of the other trial within their respected phase. During the CA+C trial, an increase in HR, lnSDNN, lnLF, EPI, and NE were observed at Post-ig when compared to Pre-ig (p≤0.05). Significant differences were observed in all markers, except LF:HF, during the CA+C and PLA trials from the Pre-rcv to Post-rcv (p≤0.05). CONCLUSION: The consumption of CA+C stimulates sympathetic activity during rest (e.g. ingestion phase) without influencing parasympathetic activity. CA+C provides no influence over cardiac autonomic recovery.

Heart rate variability in type 2 diabetes mellitus: A systematic review and meta-analysis.

BackgroundCardiac autonomic neuropathy in type 2 dibetes mellitus (T2DM) patients is frequent and associated with high cardiovascular mortality. Heart rate variability (HRV) is the gold standard to measure cardiac autonomic neuropathy. We aimed to conduct a systematic review and meta–analysis to evaluate the impact of T2DM on HRV parameters.MethodsThe PubMed, Cochrane Library, Embase and Science Direct databases were searched on 1st October 2017 using the keywords “diabetes” AND (“heart rate variability” OR “HRV”). Included articles had to report HRV parameters in T2DM patients and healthy controls measured during 24 hours with a Holter–electrocardiogram. Measurements of HRV retieved were: RR–intervals (or Normal to Normal intervals—NN), standard deviation of RR intervals (SDNN), percetange of adjacent NN intervals differing by more than 50 milliseconds (pNN50), square root of the mean squared difference of successive RR intervals (RMSSD), total power, Low Frequency (LF), High Frequency (HF) and LF/HF ratio, as per Task Force recommendations.ResultsWe included twenty-five case-control studies with 2,932 patients: 1,356 with T2DM and 1,576 healthy controls. T2DM patients had significantly (P<0.01) lower RR–intervals (effect size = –0.61; 95%CI –1.21 to –0.01), lower SDNN (–0.65; –0.83 to –0.47), lower RMSSD (–0.92; –1.37 to –0.47), lower pNN50 (–0.46; –0.84 to –0.09), lower total power (–1.52; –2.13 to –0.91), lower LF (–1.08; –1.46 to –0.69]), and lower HF (–0.79; –1.09 to –0.50). LF/HF did not differ between groups. Levels of blood glucose and HbA1c were associated with several HRV parameters, as well as Time from diagnosis of T2DMConclusionsT2DM was associated with an overall decrease in the HRV of T2DM patients. Both sympathetic and parasympathetic activity were decreased, which can be explained by the deleterious effects of altered glucose metabolism on HRV, leading to cardiac autonomic neuropathy.

Autonomic function and blood pressure in adolescents born preterm

IntroductionPreterm birth affects 10% of births in the United States. The nervous and cardiovascular systems undergo significant development in the third trimester. The autonomic nervous system (ANS) plays a significant role in regulating heart rate and blood pressure. Parasympathetic nervous activity (PNA) increases throughout the third trimester, and preterm birth is known to result in lower PNA during infancy. Preterm birth is known to put young adults at greater risk of cardiac autonomic dysfunction, hypertension and cardiac hypertrophy. However, little is known about the onset of these cardiovascular abnormalities. Autonomic dysfunction and high blood pressure are associated with increased risk of cardiovascular disease. The purpose of our research is to investigate the long term effects of preterm birth on autonomic function and blood pressure at rest in adolescents born preterm and age‐matched term‐born controls. We hypothesize that preterms will have lower autonomic function, as determined by heart rate variability at rest, and elevated blood pressure compared to term‐born adolescents.Methods21 children born preterm (birthweight &lt;1500 g, gestational age &lt;32 weeks) and 20 children born full term (gestational age &gt;38 weeks) were studied. Heart rate variability measurements were obtained during a 15 minute supine resting period using a 3‐lead ECG. The standard deviation of R‐R interval (SDRR) and the root mean squared of successive differences (RMSSD) were calculated using PowerLab software. Blood pressures were obtained every 2 minutes during a 10 minute supine rest period using a brachial artery cuff, and the mean arterial blood pressure (MABP), systolic blood pressure (SBP), diastolic blood pressure (DBP) were determined. The relationship between MABP and RMSSD was determined using a linear regression. Results between groups were compared using Mann‐Whitney tests.ResultsPreterms had significantly lower birthweights than the controls (1097 ± 274 v 3497 ± 366 g, respectively, p&lt;0.001) and had lower gestational age (27.86 ± 2.10 v 39.74 ± 0.87 weeks, respectively, p&lt;0.001). Preterms had significantly higher MABP (82.2 ± 3.7 v 76.4 ± 4.0 mmHg, respectively, p&lt;0.001), DBP (65.8 ± 4.7 v 59.6 ± 5.1 mmHg, p=&lt;0.001), and SBP than controls (114.8 ± 5.7 v 109.9 ± 4.8 mmHg, p=.009). Preterms had lower HRV, SDRR (69.1 ± 33.8 v 110.1 ± 33.0 ms, p=.008), and RMSSD (58.8 ± 38.2 v 101.5 ± 36.2 ms, p=.012). There was a negative relationship between RMSSD and MABP (r2=0.324, p=0.007).DiscussionOur results demonstrate that adolescents born prematurely have lower HRV and higher resting blood pressure. Both autonomic dysfunction and elevated blood pressure are known to be correlated with increased risk of cardiovascular disease. Furthermore, we found a negative relationship between HRV and blood pressure in our population. Our results suggest that preterm individuals have higher sympathetic activity, and the inverse relationship between HRV and BP suggests that higher sympathetic vascular tone due to autonomic dysfunction leads to elevated BP. The individuals in our study were free of known cardiovascular or respiratory disease, and both groups were very active. Our results suggest that otherwise healthy preterm adolescents are potentially at increased risk of developing cardiovascular disease and further study is warranted.Support or Funding InformationNIH‐NHLBI R01–HL115061This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Influence of waterpipe smoking on cardiac autonomic function at rest and following high-intensity anaerobic exercise

Background: Waterpipe (WP) smoking has been linked to reduced birth weight, genetic damage, and respiratory and cardiovascular disease, possibly via enhanced exposure to carbon monoxide and volatile aldehydes. Objective: The effect of long-term WP smoking on cardiac autonomic function at rest and following exercise was investigated. Methods: Twenty males volunteered and were divided into two groups: WP smokers (WPS) and non-smokers (NSmk). Heart rate variability (HRV) at rest and following (10 mins) Wingate test was examined. Additionally, heart rate recovery (HRR) at 1 (HRR1), 2 (HRR2) and 5 mins (HRR5) post-Wingate test were considered. Results: At rest, the WPS group exhibited a significantly greater heart rate and lower standard deviation of RR intervals. The WPS group experienced a significantly greater peak heart rate while the post-Wingate recovery of HRV, HRR1, and HRR2 were similar between groups. In contrast, HRR5 for the WPS group was significantly greater than for the NSmk group. Conclusions: Long-term WP smoking resulted in an altered resting cardiac autonomic state exemplified by reduced overall HRV, specifically, a decline in vagal activity and/or relative increase in sympathetic activity that may persist during anaerobic exercise but not during early recovery.

Vascular and autonomic changes in adult cancer patients receiving anticancer chemotherapy.

Chemotherapy is associated with acute and long-term cardiotoxicity. To date, risk assessment has primarily focused on the heart; however, recent findings suggest that vascular and autonomic function may also be compromised. Whether this occurs during chemotherapy treatment remains unknown. Therefore, the present study evaluated carotid artery stiffness, cardiovagal baroreflex sensitivity (cBRS), and heart rate variability (HRV) in cancer patients currently being treated with adjuvant chemotherapy. Eleven current cancer patients receiving adjuvant chemotherapy and 11 matched (1:1) controls were studied. Carotid artery stiffness was assessed via two-dimensional ultrasonography. cBRS was assessed from the spontaneous changes in beat-to-beat time series of R-R interval and systolic blood pressure via the cross-correlation technique. HRV was assessed using the standard deviation of R-R intervals (SDNN) and low (LF) and high (HF) power frequencies. Carotid artery β-stiffness was significantly higher in the cancer patients compared with control participants (8.0 ± 0.8 vs. 6.3 ± 0.6 U, respectively; P = 0.02). cBRS was lower in the cancer patients compared with controls (4.3 ± 0.7 vs. 10.7 ± 1.9 ms/mmHg, respectively; P = 0.01), and all indices of HRV were lower in the cancer patients (SDNN, P = 0.02; LF, P = 0.01; HF, P = 0.02). There was no significant correlation between β-stiffness and cBRS ( P = 0.4). However, LF power was significantly correlated with cBRS (r = 0.66, P < 0.001). Compared with matched healthy controls, cancer patients undergoing chemotherapy demonstrated a significantly higher arterial stiffness and lower cBRS. The previously reported adverse effects of chemotherapy on the heart appear to also influence other aspects of cardiovascular health. NEW & NOTEWORTHY Patients treated with anticancer chemotherapy exhibit an impaired baroreflex control of arterial blood pressure and increased arterial stiffness. These findings hold significant value, in particular as part of a risk-stratification strategy in current cancer patients receiving chemotherapy. This is the first investigation, to our knowledge, to demonstrate an attenuated spontaneous baroreflex control of arterial blood pressure in cancer patients currently undergoing chemotherapy.

Impaired autonomic function in adolescents born preterm.

Preterm birth temporarily disrupts autonomic nervous system (ANS) development, and the long‐term impacts of disrupted fetal development are unclear in children. Abnormal cardiac ANS function is associated with worse health outcomes, and has been identified as a risk factor for cardiovascular disease. We used heart rate variability (HRV) in the time domain (standard deviation of RR intervals, SDRR; and root means squared of successive differences, RMSSD) and frequency domain (high frequency, HF; and low frequency, LF) at rest, as well as heart rate recovery (HRR) following maximal exercise, to assess autonomic function in adolescent children born preterm. Adolescents born preterm (less than 36 weeks gestation at birth) in 2003 and 2004 and healthy age‐matched full‐term controls participated. Wilcoxon Rank Sum tests were used to compare variables between control and preterm groups. Twenty‐one adolescents born preterm and 20 term‐born controls enrolled in the study. Preterm‐born subjects had lower time‐domain HRV, including SDRR (69.1 ± 33.8 vs. 110.1 ± 33.0 msec, respectively, P = 0.008) and RMSSD (58.8 ± 38.2 vs. 101.5 ± 36.2 msec, respectively, P = 0.012), with higher LF variability in preterm subjects. HRR after maximal exercise was slower in preterm‐born subjects at 1 min (30 ± 12 vs. 39 ± 9 bpm, respectively, P = 0.013) and 2 min (52 ± 10 vs. 60 ± 10 bpm, respectively, P = 0.016). This study is the first report of autonomic dysfunction in adolescents born premature. Given prior association of impaired HRV with adult cardiovascular disease, additional investigations into the mechanisms of autonomic dysfunction in this population are warranted.

&lt;b&gt;Cardiac autonomic profile in cervical spinal cord injury subjects practitioners of the physical exercise

The aim was investigate the time-course of cardiac autonomic response in men with incomplete cervical spinal cord injury (SCI) practitioners or not of physical exercise. Twenty men were separated into three groups: control group without SCI (CON; 28.3 ± 4.5 yrs; 178.4 ± 6.5 cm; 82.1 ± 6.8 kg; n=8), regularly engaged in strength training and low aerobic training; exercise group with cervical SCI (EG, 32.3 ± 4.5 yrs, 175.1 ± 5.3 cm, 73.6 ± 9.6 Kg; n=8) that practiced wheelchair rugby and sedentary group with cervical SCI (SG, 30.8 ± 5.3 yrs, 173.4 ± 10.1 cm, 69.7 ± 7.1 Kg; n=4) who did not practice physical exercise. Heart rate variability variables were calculated from ECG, in rest. CON showed high values compared to EG and SG of: standard deviation of R-R intervals (SDNN), proportion of adjacent R-R intervals differing by more than 50 ms, number of interval differences of successive NN intervals greater than 50 ms, root mean square of successive differences and the high-frequency spectral power. SDNN was significantly lower in EG compared to CON. changes in cardiac autonomic function could be noted in subjects with cervical SCI regularly engaged in an exercise program.

Higher body mass index predicts cardiac autonomic dysfunction: A longitudinal study in adolescent type 1 diabetes.

Obesity is associated with an increased risk of cardiovascular morbidity in adults with diabetes. To examine the predictive role of body mass index (BMI) and adiposity on cardiac autonomic function in childhood onset type 1 diabetes. Two hundred and fifty-three participants with type 1 diabetes (aged 8-30 years) were assessed for diabetes complications at a tertiary hospital, and followed over 7 years (total 922 visits). Heart rate variability (HRV) measures assessed by 10-minute electrocardiography recording using LabChart Pro were standard deviation of RR intervals, time between consecutive QRS complexes, [SDNN], root mean squared difference of successive RR intervals (RMSSD), triangular index (TI), and low to high frequency ratio [LF:HF]. Multivariable generalized estimating equations were used to model the longitudinal associations between HRV measures and clinical variables (BMI standard deviation scores [SDS], waist:height ratio, total daily insulin dose/kg (TDD) and hemoglobin A1c [HbA1c]). At baseline, mean age was 14.4 ± 2.7 years, diabetes duration 7.1 ± 3.7 years, HbA1c 8.3% ± 1.5% (67 ± 16 mmol/mol), and 33% were overweight/obese (BMI ≥85th percentile). At final visit, mean age was 18.5 ± 2.7 years, duration 11.3 ± 3.9 years, HbA1c 9.0% ± 1.8% (75 ± 20 mmol/mol), and 40% were overweight/obese. Adiposity (higher BMI SDS or waist: height ratio) was a significant predictor of worse HRV (lower SDNN, RMSSD; P < .05), while higher HbA1c and TDD predicted all adverse HRV measures (lower SDNN, RMSSD, TI; P < .05) and abnormal sympathovagal balance (higher LF:HF ratio; P < .05). Higher BMI and central adiposity are associated with cardiac autonomic dysfunction in childhood onset type 1 diabetes, after adjusting for HbA1c. Interventions targeting overweight/obesity during adolescence may optimize long-term vascular health in type 1 diabetes.

Transcutaneous Carbon Dioxide Treatment Affects Heart Rate Variability - A Pilot Study.

The aim of this study was to investigate the effects of carbon-dioxide treatment on heart rate variability (HRV) parameters: mean RR interval (RRI), standard deviation of RR intervals (SDNN), root mean square of successive RR differences (RMSSD); and Porta and Guzik indices, as measures of heart rate asymmetry. Twenty patients were enrolled (mean±SD, age=59±7.8 years). Measurements were performed before CO2 treatment, at the beginning of treatment, at 15 min of treatment, immediately after and 1 h after the treatment. Significant increase in SDNN was found 1 h after the treatment when compared to that before it (p=0.011). There were no significant changes in other parameters. CO2 treatment can influence the autonomic nervous system identified by SDNN changes. However, larger studies are required to confirm these results.

Evaluation of Autonomic Nervous System, Saliva Cortisol Levels, and Cognitive Function in Major Depressive Disorder Patients.

Major depressive disorder (MDD) is associated with changes in autonomic nervous system (ANS) and cognitive impairment. Heart rate variability (HRV) and Pulse pressure (PP) parameters reflect influences of the sympathetic and parasympathetic nervous system. Cortisol exerts its greatest effect on the hippocampus, a brain area closely related to cognitive function. This study aims to examine the effect of HRV, PPG, salivary cortisol levels, and cognitive function in MDD patients by using noninvasive techniques. We have recruited MDD patients, diagnosed based on DSM-V-TR criteria compared with healthy control subjects. Their HRV and PP were measured by electrocardiogram (ECG) and photoplethysmography (PPG). Salivary cortisol levels were collected and measured on the same day. MDD patients exhibited elevated values of mean HR, standard deviation of HR (SDHR), low frequency (LF) power, low frequency/high frequency (LF/HF) ratio, mean PP, standard deviation of pulse pressure (SDPP), and salivary cortisol levels. Simultaneously, they displayed lower values of mean of R-R intervals (mean NN), standard deviation of R-R intervals (SDNN), high frequency (HF) power, and WCST scores. Results have shown that the ANS of MDD patients were dominated by the sympathetic activity and that they have cognitive deficits especially in the domain of executive functioning.

The Impact of Respiratory Events on the Autonomic Nervous System during Sleep.

Sleep apnea hypopnea syndrome (SAHS) is an independent risk factor for cardiovascular diseases. However, the pathophysiology between them is not yet clear. This paper seeks to understand how respiratory events impact the cardiovascular system by heart rate variability. We compared the differences between successional pathological respiratory events (PR) and pure normal respiration (NR) during sleep. The transitions between normal and pathological respiration (TR) were also analyzed. Thirteen patients who suffered moderate or severe SAHS were enrolled in this study. The results demonstrate that the beat-to-beat interval (RR interval) mean value and sample entropy are significantly lower during PR than during NR. RR interval standard deviation, the power of very low frequency (VLF) and low frequency (LF), total power, and the low frequency/high frequency (LF/HF) ratio were significantly larger during PR than during NR. However, the high frequency (HF) power was not significantly different between normal and pathological respiration. Additionally, the trends during TR also supported these significant differences. The results indicate that during pathological respiration, as the heart rate and its volatility increase, the complexity of its rhythm decreases. We conclude that the energy of the autonomic nervous system rapidly increases during pathological respiration, especially at the beginning. The HF power does not significantly change to modulate the heart rhythm, but the activity of the sympathetic nervous system will significantly increase, resulting in the imbalance of the LF/HF ratio. In addition to these findings, this paper discusses the influence of arousal on these indices during TR.

Additive effects of heating and exercise on baroreflex control of heart rate in healthy males.

This study assessed the additive effects of passive heating and exercise on cardiac baroreflex sensitivity (cBRS) and heart rate variability (HRV). Twelve healthy young men (25 ± 1 yr, 23.8 ± 0.5 kg/m2) randomly underwent two experimental sessions: heat stress (HS; whole body heat stress using a tube-lined suit to increase core temperature by ~1°C) and normothermia (NT). Each session was composed of a preintervention rest (REST1); HS or NT interventions; postintervention rest (REST2); and 14 min of cycling exercise [7 min at 40%HRreserve (EX1) and 7 min at 60%HRreserve (EX2)]. Heart rate and finger blood pressure were continuously recorded. cBRS was assessed using the sequence (cBRSSEQ) and transfer function (cBRSTF) methods. HRV was assessed using the indexes standard deviation of RR intervals (SDNN) and root mean square of successive RR intervals (RMSSD). cBRS and HRV were not different between sessions during EX1 and EX2 (i.e., matched heart rate conditions: EX1 = 116 ± 3 vs. 114 ± 3 and EX2 = 143 ± 4 vs. 142 ± 3 beats/min but different workloads: EX1 = 50 ± 9 vs. 114 ± 8 and EX2 = 106 ± 10 vs. 165 ± 8 W; for HS and NT, respectively; P < 0.01). However, when comparing EX1 of NT with EX2 of HS (i.e., matched workload conditions but with different heart rates), cBRS and HRV were significantly reduced in HS (cBRSSEQ = 1.6 ± 0.3 vs. 0.6 ± 0.1 ms/mmHg, P < 0.01; SDNN = 2.3 ± 0.1 vs. 1.3 ± 0.2 ms, P < 0.01). In conclusion, in conditions matched by HR, the addition of heat stress to exercise does not affect cBRS and HRV. Alternatively, in workload-matched conditions, the addition of heat to exercise results in reduced cBRS and HRV compared with exercise in normothermia. NEW & NOTEWORTHY The present study assessed cardiac baroreflex sensitivity during the combination of heat and exercise stresses. This is the first study to show that prior whole body passive heating reduces cardiac baroreflex sensitivity and autonomic modulation of heart rate during exercise. These findings contribute to the better understanding of the role of thermoregulation on cardiovascular regulation during exercise.