Standard Deviation Of Normal-to-normal RR Intervals Research Articles

Association between obstructive sleep apnea and arrhythmia and heart rate variability among hypertensive patients

BackgroundThe relationship between obstructive sleep apnea (OSA) and the occurrence of arrhythmias and heart rate variability (HRV) in hypertensive patients is not elucidated. Our study investigates the association between OSA, arrhythmias, and HRV in hypertensive patients.MethodsWe conducted a cross-sectional analysis involving hypertensive patients divided based on their apnea-hypopnea index (AHI) into two groups: the AHI ≤ 15 and the AHI > 15. All participants underwent polysomnography (PSG), 24-hour dynamic electrocardiography (DCG), cardiac Doppler ultrasound, and other relevant evaluations.ResultsThe AHI > 15 group showed a significantly higher prevalence of frequent atrial premature beats and atrial tachycardia (P = 0.030 and P = 0.035, respectively) than the AHI ≤ 15 group. Time-domain analysis indicated that the standard deviation of normal-to-normal R-R intervals (SDNN) and the standard deviation of every 5-minute normal-to-normal R-R intervals (SDANN) were significantly higher in the AHI > 15 group (P = 0.020 and P = 0.033, respectively). Frequency domain analysis revealed that the low-frequency (LF), high-frequency (HF) components, and the LF/HF ratio were also significantly elevated in the AHI > 15 group (P < 0.001, P = 0.031, and P = 0.028, respectively). Furthermore, left atrial diameter (LAD) was significantly larger in the AHI > 15 group (P < 0.001). Both univariate and multivariable linear regression analyses confirmed a significant association between PSG-derived independent variables and the dependent HRV parameters SDNN, LF, and LF/HF ratio (F = 8.929, P < 0.001; F = 14.832, P < 0.001; F = 5.917, P = 0.016, respectively).ConclusionsHypertensive patients with AHI > 15 are at an increased risk for atrial arrhythmias and left atrial dilation, with HRV significantly correlating with OSA severity.

Acute Effects of Fatigue on Cardiac Autonomic Nervous Activity.

The onset of fatigue disrupts the functioning of the autonomic nervous system (ANS), potentially elevating the risk of life-threatening incidents and impairing daily performance. Previous studies mainly focused on physical fatigue (PF) and mental fatigue (MF) effects on the ANS, with limited knowledge concerning the influence of physical-mental fatigue (PMF) on ANS functionality. This study aimed to assess the immediate impact of PMF on ANS function and to compare its effects with those of PF and MF on ANS function. Thirty-six physically active college students (17 females) without burnout performed 60-min cycling exercises, AX-Continuous Performance Task (AX-CPT), and cycling combined with AX-CPT to induce PF, MF, and PMF respectively. Subjective fatigue levels were measured using the Rating of Perceived Exertion scale and the Visual Analog Scale-Fatigue. Heart rate variability was measured before and after each protocol to assess cardiac autonomic function. The proposed tasks successfully induced PF, MF, and PMF, demonstrated by significant changes in subjective fatigue levels. Compared with baseline, PMF decreased the root mean square of successive differences (RMSSD) between normal heartbeats (P < 0.001, d = 0.50), the standard deviation of normal-to-normal RR intervals (SDNN) (P < 0.01, d = 0.33), and the normalized high-frequency (nHF) power (P < 0.001, d = 0.32) while increased the normalized low-frequency (nLF) power (P < 0.001, d = 0.35) and the nLF/nHF ratio (P < 0.001, d = 0.40). Compared with MF, PMF significantly decreased RMSSD (P < 0.001, η2 = 0.431), SDNN (P < 0.001, η2 = 0.327), nLF (P < 0.01, η2 = 0.201), and nHF (P < 0.001, η2 = 0.377) but not the nLF/nHF ratio. There were no significant differences in ΔHRV (i.e., ΔRMSSD, ΔSDNN, ΔnLF/nHF, ΔnLF, and ΔnHF), heart rate, and training impulse between PF- and PMF-inducing protocols. Cognitive performance (i.e., accuracy) in AX-CPT during the PMF-inducing protocol was significantly lower than that during the MF-inducing protocol (P < 0.001, η2 = 0.101). PF and PMF increased sympathetic activity and decreased parasympathetic activity, while MF enhanced parasympathetic activity.

Risk assessment of post-myocardial infarction patients with preserved ejection fraction using 45-min short resting Holter electrocardiographic recordings.

Risk stratification for sudden cardiac death in post-myocardial infarction (post-MI) patients remains a challenging task. Several electrocardiographic noninvasive risk factors (NIRFs) have been associated with adverse outcomes and were used to refine risk assessment. This study aimed to evaluate the performance of NIRFs extracted from 45-min short resting Holter ECG recordings (SHR), in predicting ventricular tachycardia inducibility with programmed ventricular stimulation (PVS) in post-MI patients with preserved left ventricular ejection fraction (LVEF). We studied 99 post-MI ischemia-free patients (mean age: 60.5 ± 9.5 years, 86.9% men) with LVEF ≥40%, at least 40 days after revascularization. All the patients underwent PVS and a high-resolution SHR. The following parameters were evaluated: mean heart rate, ventricular arrhythmias (premature ventricular complexes, couplets, tachycardias), QTc duration, heart rate variability (HRV), deceleration capacity, heart rate turbulence, late potentials, and T-wave alternans. PVS was positive in 24 patients (24.2%). HRV, assessed by the standard deviation of normal-to-normal R-R intervals (SDNN), was significantly decreased in the positive PVS group (42 ms vs. 51 ms, p = .039). SDNN values <50 ms were also associated with PVS inducibility (OR 3.081, p = .032 in univariate analysis, and 4.588, p = .013 in multivariate analysis). No significant differences were identified for the other NIRFs. The presence of diabetes, history of ST-elevation MI (STEMI) and LVEF <50% were also important predictors of positive PVS. HRV assessed from SHR, combined with other noninvasive clinical and echocardiographic variables (diabetes, STEMI history, LVEF), can provide an initial, practical, and rapid screening tool for arrhythmic risk assessment in post-MI patients with preserved LVEF.

Heart Rate Variability and Chronotype in Young Adult Men.

Whether morning heart rate variability (HRV) predicts the magnitude of its circadian variation in the absence of disease or is influenced by chronotype is unclear. We aimed to quantify associations between (1) morning HRV and its diurnal change, and (2) morning HRV and a Morningness-Eveningness Questionnaire (MEQ)-derived chronotype. Resting electrocardiograms were obtained in the morning and evening on separate days in a counterbalanced order to determine the mean RR interval, root mean square of successive differences (RMSSD), and standard deviation of normal-to-normal RR intervals (SDNN) in 23 healthy men (24.6 ± 3.4 yrs; body mass index: 25.3 ± 2.8 kg/m2). The MEQ was completed during the first laboratory visit. Morning RMSSD and SDNN were significantly higher (Ps &lt; 0.05) than evening values. Morning RMSSD and SDNN were associated with their absolute (Ps &lt; 0.0001), and relative diurnal changes (Ps &lt; 0.01). No associations were observed between HRV parameters and the MEQ chronotypes (Ps &gt; 0.09). Morning HRV was a stronger determinant of its evening change than chronotype. Greater diurnal variation in HRV was dependent on higher morning values. Strategies to improve basal HRV may therefore support healthier cardio-autonomic circadian profiles in healthy young men.

Heart rate variability: a novel biomarker for agitation propensity in Alzheimer’s disease?

AbstractBackgroundAgitation, a common symptom in Alzheimer’s disease (AD), may be related to impaired emotion regulation capacity with involvement of autonomic networks. Heart rate variability (HRV), an index of integrity of neural networks involved in autonomic function and emotion regulation, could be a potential marker of agitation propensity. We investigated the cross‐sectional and longitudinal association between HRV and agitation prevalence in AD using the Atherosclerosis Risk in Communities (ARIC) Study cohort that followed up participants from 1987–2013.MethodParticipants at ARIC visit 5 who were clinically diagnosed with dementia (or MCI that subsequently progressed to dementia) primarily or wholly attributed to AD were included. Agitation at visit 5 was defined based on the Neuropsychiatric Inventory agitation/aggression subscale alone, or a composite score comprising agitation/aggression, irritability, disinhibition, and aberrant motor behavior subscales. HRV measures at visits 1–5 were the root mean square of successive differences in R‐R intervals (RMSSD) and standard deviation of normal‐to‐normal R‐R intervals (SDNN) obtained from resting, supine, standard twelve‐lead electrocardiograms. The associations between agitation and visit 5 HRV or visit 1–5 change in HRV (defined as individual slope coefficients from mixed effects models) were assessed using simple regression models.ResultsAmong 456 participants who had dementia during the study, N = 302 received a primary diagnosis of AD, of whom N = 120 were classified with pure AD (see Flowchart). In the pure AD subgroup, a 0.1 log‐unit higher RMSSD (odds ratio = 1.14 [1.03‐1.29]) and positive RMSSD change over the preceding two decades (odds ratio = 2.23 [1.24‐4.38]) were associated with agitation point prevalence after accounting for heart rate (change), age, sex, cognitive status, study site and race. A 0.1 log‐unit change in HRV approximated the observed difference in HRV with each decade of age. The associations persisted after accounting for use of medications with autonomic effects.ConclusionThe finding that higher HRV was associated with agitation point prevalence in N = 120 participants clinically diagnosed with dementia solely due to AD supports the potential use of HRV as a biomarker of agitation propensity, and autonomic dysfunction as a target of treatment. Future studies are needed to explore this relationship alongside measures of emotion regulation and locus coeruleus‐noradrenergic system integrity.

Investigating attentional scope as a novel indicator of emotional state in animals

In humans, contrasting emotional states can lead to a broadening or narrowing of attentional scope. Whether this is also the case in animals has yet to be investigated. If confirmed, measurement of attentional scope has potential as a novel cognitive method of welfare assessment. In this study, we therefore aimed to investigate a test of attentional scope as a measure of emotional state in animals. We did this by inducing four putatively different emotional states in dogs (N = 10), varying in valence (positive, negative) and arousal (high, low), in two different reward contexts (food rewards in Experiment 1, social rewards in Experiment 2) and then assessing dogs’ behavioural responses in a test of attentional scope. We also recorded heart rate variability (HRV) parameters as additional confirmatory affective indicators. In Experiment 1, the dogs showed a narrowing of attentional scope after the induction of both positively valenced emotional states. That dogs were in a positive state was supported by the reduced Standard Deviation of normal-to-normal R-R intervals (SDNN) and the reduced Low Frequency (LF) and Very Low Frequency (VLF) HRV. In Experiment 2, when responses to social rewards were examined, we did not detect any statistically significant differences in attentional scope between the emotional states, but dogs had a slightly narrow attentional scope in the negatively valenced emotional states. The LF tended to be reduced in the high arousal positive treatment. In conclusion, our study provides the first indication that emotional states can also alter attentional scope in animals. The results justify further investigation of this approach for use in animal welfare assessment, although additional studies are needed to refine predictions.

Effect of 4-day Online Breath Meditation Workshop on Ballistocardiography-based Sleep and Cardiac Health Assessments among Medical Professionals of a Tertiary Care Hospital in North India during COVID-19.

Medical professionals (MPs) are facing stress, sleep deprivation, and burnout due to pandemic-related high patient inflow and consistent work shifts. Yoga and meditation are feasible, cost-effective, evidence-based, and well-accepted tools having multifold mental and physical health benefits. In this ongoing open-label single-arm trial, we assessed changes in sleep, heart rate variability (HRV), and vitals before and after a 4-day online breath meditation workshop (OBMW) among 41 MPs at a tertiary care hospital in northern India during COVID-19 pandemic. Outcomes were assessed at baseline and after the 4-day workshop using a ballistocardiography-based contactless health monitoring device. The workshop was conducted online. Two participants were excluded due to a lack of adherence. A highly significant increase was seen in total sleep duration (p = 0.000) and duration of deep sleep (p = 0.001), rapid eye movement (REM) sleep (p = 0.000), and light sleep (p = 0.032). HRV outcomes of the standard deviation of normal-to-normal R-R intervals (SDNN) and root mean square of successive differences between adjacent normal heartbeat (RMSSD) also improved significantly (p = 0.000) while heart rate reduced significantly (p = 0.001). No significant change was observed in breath rate, total time awake, or in the low-frequency by high-frequency (LF/HF) spectrum of HRV. Four days of OBMW improved sleep and HRV among MPs, strengthening the fact that yoga and meditation can help induce psychophysical relaxation and prove to be an effective tool to combat stress and sleep deprivation. As the stakeholders in patient care, that is, MPs are healthy, it will further improve patient care and reduce the chance of medical errors.

Interleukin-33 and soluble suppression of tumorigenicity 2 in scleroderma cardiac involvement

Interleukin (IL)-33 is part of the IL-1 family of cytokines and soluble suppression of tumorigenicity 2 (sST2) is part of the family of IL-1 receptors. In systemic sclerosis (SSc), IL-33 and sST2 are involved in cardiac manifestations such as diastolic dysfunction (DD), autonomic dysfunction (AD) and right ventricular–pulmonary arterial coupling assessed by tricuspid annular plane systolic excursion (TAPSE)/systolic pulmonary artery pressure (sPAP). Serum levels of IL33 and sST2 were assessed in 50 SSc patients and 14 healthy controls (HC). Clinical assessment, echocardiography and heart rate variability (HRV) analysis were performed in SSc patients. Serum levels of IL-33 and sST2 were significantly higher in SSc patients than HC. A linear positive correlation between modified Rodnan skin score and IL33 was observed. Serum values of sST2 were higher in SSc patients with DD than in patients without DD [15403 pg/ml (12,208–19,941) vs 8556 pg/ml (6820–11,036), p < 0.001]. sST2 showed a negative correlation with standard deviation of normal-to-normal RR intervals (SDNN) (r = − 0.281, p < 0.05) and positive correlation with low frequency/high frequency (LF/HF) (r = 0,349, p < 0.01). Negative linear correlation exists between sST2 and TAPSE/sPAP (r = − 0.398, p < 0.01). Serum levels of IL-33 and sST2 are higher in SSc patients than HC. Serum levels of sST2 are a potential marker of DD, AD and right ventricular–pulmonary arterial coupling.

Decreased Nighttime Heart Rate Variability and Progression of White Matter Hyperintensities of Presumed Vascular Origin. A Prospective Study in Community-Dwelling Older Adults

ObjectivesEvidence on the role of autonomic dysfunction on white matter hyperintensities (WMH) progression is limited. This study aims to assess the impact of a low nighttime heart rate variability (HRV) on WMH progression in community-dwelling older adults. Materials and methodsFollowing a prospective longitudinal study design, all individuals aged ≥60 years enrolled in the Atahualpa Project Cohort from 2012 to 2019 were invited to receive baseline HRV determinations through 24-h Holter monitoring, together with clinical interviews and brain MRIs. These individuals were periodically followed by means of annual door-to-door surveys, and those who also received brain MRIs at the end of the study (May 2021) were included in the analysis. Poisson regression models, adjusted for relevant confounders, were fitted to assess the incidence rate ratio (IRR) of WMH progression according to nighttime standard deviation of normal-to-normal R-R intervals (SDNN). ResultsThis study included 254 individuals aged ≥60 years (mean age: 65.4 ± 5.9 years; 55% women). The mean nighttime SDNN was 116.8 ± 36.3 ms. Follow-up MRIs showed WMH progression in 103 (41%) individuals after a median follow-up of 6.5 years. In unadjusted analyses, nighttime SDNN was lower among participants who developed WMH progression than in those who did not (p < 0.001). A Poisson regression model, adjusted for relevant covariates, disclosed a significantly inverse association between nighttime SDNN and WMH progression (IRR: 0.99; 95% C.I.: 0.98–0.99; p = 0.014). ConclusionsStudy results show an inverse association between nighttime SDNN and WMH progression, and provide support for the role of sympathetic overactivity in this relationship.

Towards better reliability in fetal heart rate variability using time domain and spectral domain analyses. A new method for assessing fetal neurological state?

ObjectivesFetal heart rate variability (FHRV) has shown potential in fetal surveillance. Therefore, we aimed to evaluate the reliability of time domain and spectral domain parameters based on non-invasive fetal electrocardiography (NI-FECG).MethodNI-FECG, with a sampling frequency of 1 kHz, was obtained in 75 healthy, singleton pregnant women between gestational age (GA) 20+0 to 41+0. The recording was divided into a) heart rate pattern (HRP) and b) periods fulfilling certain criteria of stationarity of RR-intervals, termed stationary heart rate pattern (SHRP). Within each recording, the first and the last time series from each HRP with less than 5% artifact correction were analyzed and compared. Standard deviation of normal-to-normal RR-intervals (SDNN), root mean square of successive differences (RMSSD), high frequency power (HF-power), low frequency power (LF-power), and LF-power/HF-power were performed. A multivariate mixed model was used and acceptable reliability was defined as intraclass correlation coefficient (ICC) ≥ 0.80 and a coefficient of variation (CV) ≤ 15%. Based on these results, the CV and ICC were computed if the average of two to six time series was used.ResultsFor GA 28+0 to 34+6, SDNN and RMSSD exhibited acceptable reliability (CV < 15%; ICC > 90%), whereas GA 35+0 to 41+0and 20+0 to 27+6 showed higher CVs. Spectral domain parameters also showed high CVs However, by using the mean value of two to six time series, acceptable reliability in SDNN, RMSSD and HF-power from GA 28+0 was achieved. Stationarity of RR-intervals showed high influence on reliability and SHRP was superior to HRP, whereas the length of the time series showed minor influence.ConclusionAcceptable reliability seems achievable in SDNN, RMSSD and HF-power from gestational week 28. However, stationarity of RR-intervals should be considered when selecting time series for analyses.

Fetal respiratory movements improve reliability of heart rate variability and suggest a coupling between fetal respiratory arrhythmia and vagal activity.

Fetal heart rate variability (FHRV) reflects autonomic cardiac regulation. The autonomic nervous system constantly adjusts the heart rate to maintain homeostasis. By providing insight into the fetal autonomic state, FHRV has the potential to become an investigational and clinical instrument. However, the method needs standardization and the influence of fetal movements, including fetal respiratory movements, is not well explored. Therefore, in a highly standardized setting, the aim was to evaluate the association between fetal movements and fetal heart rate variability (FHRV) including their impact on reliability. Fetal heart rate was obtained by noninvasive fetal electrocardiography (NI‐FECG) and fetal movements by simultaneous ultrasound scanning in 30 healthy singleton pregnant women on two occasions with a maximum interval of 7 days. The standard deviation of normal‐to‐normal RR‐intervals (SDNN), root mean square of successive RR‐interval differences (RMDDS), high‐frequency power (HF‐power), low‐frequency power (LF‐power), and LF/HF were measured. A multivariate mixed model was used and reliability was defined as acceptable by a coefficient of variance (CV) ≤15% and an intraclass correlation coefficient (ICC) ≥0.80. During time periods with fetal respiratory movements, the highest reliability was achieved. Intra‐ and inter‐observer reliability measurements were very high (CV: 0–9%; ICC ≧ 0.86). Within the same recording, SDNN and RMSSD achieved acceptable reliability (CV: 14–15%; ICC ≧ 0.80). However, day‐to‐day reliability displayed high CV’s. In time periods with fetal respiratory movements, as compared to periods with quiescence RMSSD and HF‐power were higher (Ratio: 1.33–2.03) and LF/HF power lower (Ratio: 0.54). In periods with fetal body movements SDNN, RMSSD and HF‐power were higher (Ratio: 1.27–1.65). In conclusion, time periods with fetal respiratory movements were associated with high reliability of FHRV analyses and the highest values of parameters supposed to represent vagal activity.

Autonomic dysfunction is common in liver cirrhosis and is associated with cardiac dysfunction and mortality: prospective observational study.

Although autonomic dysfunction has been shown to be associated with liver cirrhosis, the prevalence and prognostic implications are unclear. Abnormal heart rate variability (HRV), a measure of autonomic function, has not been well investigated in cirrhosis. To evaluate the prevalence of high-risk HRV parameters in a cohort of cirrhotic patients and their association with cardiac dysfunction and mortality. Prospective observational study conducted in the Federal University of São Paulo. A cohort of 120 patients, comprising 17 healthy controls and 103 cirrhotic outpatients, was evaluated and followed for 10 months. HRV analysis was based on 24-hour Holter monitoring and defined using time-domain and frequency-domain parameters. The HRV parameters were statistically lower in cirrhotic patients than in healthy subjects. High-risk HRV parameters were prevalent, such that 64% had at least one high-risk parameter. Time-domain parameters correlated with Child scores (P < 0.0001). In regression models, HRV parameters were independent predictors of diastolic dysfunction and mortality. During 10 months of follow-up, there were 11 deaths, all of patients with at least one high-risk HRV parameter. Kaplan-Meier analysis estimated low survival rates among patients with standard deviation of normal-to-normal RR intervals (SDNN) < 100. Reduced HRV is prevalent in liver cirrhosis and is related to cardiac dysfunction, severity of liver disease and mortality. Abnormal high-risk HRV parameters are prevalent among cirrhotic patients and are also predictors of mortality. Our findings highlight the need for a more careful cardiac evaluation of cirrhotic patients.

Relationship between vitamin D status and cardiac autonomic neuropathy in prediabetes.

Studies have suggested that vitamin D deficiency is associated with impaired cardiac autonomic nerve function. This study explores the correlation between serum vitamin D and cardiac autonomic neuropathy (CAN) in prediabetes and reveals the protective effect of vitamin D against CAN. In total, 113 patients with prediabetes and definite CAN and 180 with prediabetes but without CAN were enrolled on the basis of their standard cardiovascular autonomic reflex test results. Chemiluminescence was used to measure 25(OH)D, the patients with CAN were divided into four groups, and the heart rate variability (HRV) of the study groups were compared. Relative to the 50≤25(OH)D<75-nmol/L group, the 25≤25(OH)D<50-nmol/L and 25(OH)D<25-nmol/L groups exhibited significant differences in the time and frequency domains of HRV (p< 0.05). Furthermore, we discovered that 25(OH)D is positively correlated with standard deviation of normal-to-normal RR intervals (SDNN) (β=0.566, p<0.05) and negatively correlated with low-to-high frequency ratio (LF/HF) (β=-0.199, p<0.05). A logistic regression reveals that CAN in prediabetes is significantly correlated with the 25(OH)D concentrations of <25 nmol/L (OR, 2.380 [1.208-4.691]; p<0.05) and 25≤25(OH)D<50 nmol/L (OR, 1.875 [1.064-3.751]; p<0.05). Serum 25(OH)D is significantly correlated with CAN in prediabetes, especially in the 25(OH)D <25-nmol/L group. Therefore, vitamin D deficiency may be related to the occurrence of CAN in prediabetes, and appropriate supplementation may provide protection against CAN.

Acute effects of exercise on cardiac autonomic function and arterial stiffness in patients with stable coronary artery disease

Objectives. To examine the acute effect of a maximal aerobic exercise effort on aortic, peripheral arterial stiffness and cardiovagal modulation of trained and untrained patients with coronary artery disease (CAD). Design. Cross-sectional study. Methods. Eighteen untrained patients with CAD, 18 trained patients with CAD, and 18 apparently healthy trained subjects were sampled and matched for age and body mass index. Aortic and peripheral stiffness were measured by applanation tonometry estimates of carotid-femoral (cfPWV), carotid-radial (crPWV), and carotid-dorsalis pedis pulse wave velocity (cdPWV), respectively. Cardiovagal modulation was assessed by heart-rate variability (HRV) indices including the standard deviation of normal-to-normal RR intervals (SDNN), root-mean-square of successive differences (RMSSD), and the high-frequency power band (HF). cfPWV, crPWV, cdPWV, and HRV indices were measured at rest, 10 and 30 min following a maximal cardiopulmonary exercise test on a cycle ergometer. Results. No differences were observed between groups at rest nor over time in indices of HRV, cfPWV and cdPWV. Still, main effects of time were observed in cfPWV (p < .001; ɳ 2 = 0.313) and cdPWV (p = .003, ɳ 2 = 0.111), RMSSD (p < .001, ɳ 2 = 0.352), HF (p < .001, ɳ 2 = 0.265) and LF/HF (p = .001, ɳ 2 = 0.239), as cdPWV, RMSSD, and HF were reduced 10 min following exercise, whereas cfPWV and LF/HF were increased. Changes in cPP were associated with changes in HRV from rest to min 10 (HF, r = 0.302), and to min 30 (HF, r = 0.377; SDNN, r = 0.357; RMSSD, r = 0.429). Conclusion. Training level and CAD do not seem to influence arterial stiffness and cardiac autonomic responses to maximal exercise.

Resilience of the hellenic navy SEALs assessed by heart rate variability during cognitve tasks

Abstract Background The interaction between high physical performance under extreme conditions and simultaneous control of the cognitive executive functioning has been a subject of research in literature for the past few decades. Stroop test and Heart-rate variability (HRV), have been verified clinical tools for the assessment of cerebral and autonomic/ cardiovascular stress responses respectively. Purpose The investigation of HRV adaptive response to stress and cognitive stress resilience under extremely strenuous conditions. Methods 34 consecutive subjects were enrolled. Of them, 18 were candidates under intense preparation for their enlistment in the Hellenic Navy SEALs (HNS) and 16 were healthy controls (HC). All subjects underwent stroop tasks, along with mental state and personality examination. HRV variables in time and frequency domains recordings were acquired, during each aforementioned cognitive testing procedure. Results HNS's performance on both cognitive and emotion stroop tasks were equivalent to controls. During the size comparison of the number stroop and emotion stroop, HC had statistically significantly higher power content at different HRV frequency bands compared to HNS participants (p=0.036 and p=0.06 respectively). Finally, in a between group comparison of the psychometric tools, HNS had significantly higher somatization (p&amp;lt;0.01), anxiety (p=0.037) and neuroticism (p=0.047) than HC. Correlation was conducted for each group separately, between the psychometric tools and the measurements of HRV for both number and emotion stroop. Moderate negative correlations were found between SDNN (Standard deviation of normal-to-normal RR-intervals) during the size comparison of number stroop and three out of nine categories of psychometric questionnaire; somatization (r(23)=−0.452, p&amp;lt;0.05), anxiety (r(23)=−0.457, p&amp;lt;0.05) and hostility (r(23)=−0.445, p&amp;lt;0.05) Conclusion The above findings suggest that HNS display flexibility in their autonomic regulation during cognitive and emotional tasks. This characteristic is closely related to problem solving or adaptability skills. Additionally, HRV can be a promising clinical index regarding the assessment of psychophysiological resilience especially in the neurovisceral integration (NVI) model. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Region of Attica

Screening of QTc interval and global autonomic activity in autosomal dominant polycystic kidney disease and atherosclerotic renal artery stenosis hypertensive patients.

Arterial hypertension (AH) represents a major risk factor for cardiovascular disease and is associated to several complications, such as prolonged corrected QT (QTc) interval and impaired heart rate variability (HRV). Secondary causes of AH include autosomal dominant polycystic kidney disease (ADPKD) and atherosclerotic renal artery stenosis (ARAS), both known to be related to arrhythmic risk and autonomic imbalance. The aim of the study is to evaluate whether global autonomic activity and QTc interval differently affect ADPKD and ARAS hypertensive patients. An observational study was performed on 59 patients: 16 ADPKD patients and 19 diagnosed with ARAS, compared to 24 healthy controls (HC). All patients underwent clinical evaluation, biochemical lab tests, 24-hour electrocardiogram (ECG) and renal Doppler ultrasound. HRV was assessed through the analysis of 24-hour ECG to detect standard deviation of normal-to-normal RR intervals (SDNN). QTc interval was defined as prolonged when > 440 msec. SDNN was significantly lower in ADPKD and ARAS patients than HC (p < 0.0001) and no significant differences were found between ADPKD and ARAS patients (p > 0.05). QTc was found significantly higher in ARAS patients than HC (p = 0.001) and in ARAS patients than ADPKD patients (p = 0.004). The pathogenesis of hypertension in ADPKD and ARAS patients is related to the activation of the renin angiotensin aldosterone system (RAAS). In ADPKD, cyst enlargement leads to kidney ischemia and renin release, associated to endothelial dysfunction, low nitric oxide and sympathetic tone activation. Differently, reduction in renal perfusion pressure activates RAAS and renal adrenergic nerves in ARAS patients. We can speculate that prolonged QTc interval is more present in ARAS vs. ADPKD hypertensive patients due to a greater activation of RAAS. We suggest adding 24-hour HRV evaluation in association with traditional risk factors in course of ADPKD and ARAS hypertension to better stratify cardiovascular risk in these groups of patients.

An Attempt to Predict Changes in Heart Rate Variability in the Training Intensification Process among Cyclists.

Individual changes in resting heart rate variability (HRV) parameters were assessed in seven Polish cyclists during a training process consisting of: a six-week period (P1) of predominantly low- and moderate-intensity training (L-MIT) and a six-week period (P2) where the proportion of high-intensity interval training (HIT) increased. Daily recorded HRV parameters included high-frequency spectral power (HF), square root of the mean squared difference between successive normal-to-normal RR intervals (RMSSD), and standard deviation of normal-to-normal RR intervals (SDNN). In each training microcycle, the average values of HFav, RMSSDav, and SDNNav were calculated individually for each participant. In three cyclists, HF was higher in P2 compared to P1, whereas in one cyclist, HF was higher in P1 than in P2. Each of these four cyclists presented an individual correlation between the average daily duration HIT effort in training microcycles (HITav) and HFav. Cyclists with low baseline values of HRV parameters showed increased activity of the parasympathetic nervous system, while in the cyclist with high baseline values of HRV parameters, an opposite change was observed. In conclusion, changes in resting HRV parameters between period P1 and P2 can be individualised. In the investigated group, it was possible to predict how HRV would change as a result of training intensification on the basis of HRV baseline values.

Wearable Patch Heart Rate Variability Is an Early Marker of Systemic Inflammation During Experimental Human Endotoxemia.

Early diagnosis and treatment can reduce the risk of organ failure and mortality in systemic inflammatory conditions. Heart rate variability (HRV) has potential for early identification of the onset of systemic inflammation, as it may detect changes in sympathetic nervous system activity resulting from the developing inflammatory response before clinical signs appear. With the use of new methodologies, we investigated the onset and kinetics of HRV changes as well as several inflammatory parameters and symptoms during experimental human endotoxemia, a model of systemic inflammation in humans in vivo. Healthy volunteers were intravenously administered LPS (n = 15) or placebo (n = 15). HRV was determined using a wireless wearable device, and parameters low to high frequency (LF:HF) ratio, root mean square of the successive differences (RMSSD), and standard deviation of normal-to-normal R-R intervals (SDNN)were calculated through 1-min-rolling 6-min windows. Plasma cytokine levels and flu-like symptoms and vital signs were serially assessed. The increase in LF:HF ratio, reflecting sympathetic predominance, was more pronounced in the LPS group compared to the placebo group, with the difference becoming statistically significant 65 min following LPS administration (1.63 [1.42-1.83] vs. 1.28 [1.11-1.44], P = 0.005). Significant between-group differences in RMSSD and SDNN were observed from 127 to 140 min post-LPS administration onwards, respectively. Plasma cytokine levels showed significant between-group differences staring 60 min post-LPS. For symptom score, heart rate, temperature, and diastolic blood pressure, significant differences compared with the placebo group were observed at 90, 118, 120, and 124 min post-LPS, respectively. In a controlled human model of systemic inflammation, elevations in the LF:HF ratio followed very shortly after elevations in plasma cytokine levels and preceded onset of flu-like symptoms and alterations in vital signs. HRV may represent a promising non-invasive tool for early detection of a developing systemic inflammatory response.

Green Exercise: Can Nature Video Benefit Isometric Exercise?

Green exercise is the combination of physical activity and nature exposure, which has been associated with positive effects on psychophysiological health. This study aimed to investigate the effects of nature video viewing on isometric exercise and find a useful practice for green exercise in urban living. In the current study, 18 male subjects were recruited in a randomized crossover trial and underwent a sequence of wall squat exercises. The whole experiment contained three periods of baseline (before exercise), exercise, and recovery (after exercise), and each period lasted for 2 min. A video of forest walking was played in the exercise and recovery periods as treatment, while a black screen was set as control. The Rate of Perceived Exertion Scale (RPE) and Feeling Scale (FS) were employed to measure perceived exertion and affective responses in the exercise period; heart rate (HR) and heart rate variability (HRV) including the standard deviation of normal-to-normal RR intervals (SDNN), the root mean square of successive differences (RMSSD), and the standard deviations of the Poincaré plot (SD1), were recorded in the three periods. Heart rate recovery (HRR) in the recovery period was further calculated based on 30 s and 60 s time frames. Results demonstrated that during the exercise period nature video viewing was associated with better affective responses (median of 1.00 and an interquartile (IQR) of 2.00, p = 0.017), lower perceived exertion (median = 6.00, IQR = 2.00, p = 0.021), and lower HR (median = 89.60, IQR = 20.94, p = 0.01), but the differences in HRV indices between the experimental settings were not statistically significant. In the recovery period, significantly higher values of RMSSD (median = 34.88, IQR = 24.52, p = 0.004), SD1 (median = 24.75, IQR = 17.41, p = 0.003), and HR (median = 84.18, IQR = 16.58, p = 0.001) were observed in the treatment setting, whereas no statistically significant difference was found for HRR. In general, our findings support that nature video viewing may help reduce perceived exertion, increase exercise pleasure, buffer heart rate, and improve cardiac autonomic recovery for wall squat exercising, which implies the potential of nature-based stimuli in green exercise. However, due to the limited research sample, further study may need to include female participants and focus on various populations to confirm the effectiveness of using virtual and environments depicting nature at home or in public exercise places to promote positive exercise experience.

Heart Rate Variability as a Non-invasive Objective Parameter for Predicting the Occurrence of Chemotherapy-induced Peripheral Neuropathy in Patients With Gastrointestinal Cancer.

Chemotherapy-induced peripheral neuropathy (CIPN) is one of the most common chemotoxicities. However, no effective clinical CIPN screening methods have been reported. This study aimed to investigate whether changes in heart rate variability (HRV) could predict the development of CIPN for early symptom control in chemotherapy-prescribed patients with gastrointestinal (GI) cancer. Fifty-five GI cancer outpatients undergoing palliative chemotherapy including taxanes and/or platinum compounds were enrolled. CIPN was diagnosed using National Cancer Institute Common Toxicity Criteria for Adverse Event (NCI-CTCAE). HRV measures were derived from electrocardiogram signals. Twelve weeks after starting chemotherapy, 39 (70.9%) patients who complained of NCI-CTCAE grade 1-3 sensory changes were diagnosed with CIPN. Standard deviation of normal-to-normal R-R intervals (SDNN), high frequency (HF), low frequency (LF), and LF/HF ratio changed significantly during 3 assessment periods. Percentage changes in SDNN and HF were related to the occurrence of CIPN symptoms. A decision tree model indicated that patients with a rapid percentage change decrease in SDNN and HF were CIPN-positive. Using SDNN and HF, our decision tree predicted CIPN occurrence. The changes in HRV may occur earlier than sensory CIPN symptoms.