Frequency Domain Heart Rate Variability Indices Research Articles

Heart Rate Variability in Military Pilots During Flight: A Scoping Review.

Piloting an aircraft is a complex multitasking activity that involves managing information in a nonautomatic way and generates a high workload (psychological, cognitive, and physical) for the pilot. The excess of these demands can result in decreased performance and may impair flight safety. Heart rate variability (HRV) has been used in recent studies as a method to investigate operator's workload in complex environments. This measure can assess the stress and recovery ability of the autonomic nervous system. However, a better understanding of flight influence on the pilot's autonomic modulation is necessary. Therefore, this scoping review aims to systematically map the studies related to changes in the autonomic modulation in military pilots during flight, in order to characterize their workload at different times and flight profiles. A literature search was conducted using MEDLINE (by PubMed), SCOPUS, and LILACS databases. Recent records (2002-2022) that analyzed HRV in military pilots during flight were included. Meanwhile, studies in which piloting activity was not performed were excluded. The study was conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guideline extension for Scoping Reviews and the Updated Methodological Guidance for the Conduct of Scoping Reviews. A total of 298 records were obtained, of which 19 were included in the scoping review. The studies analyzed flights performed in high- and low-performance aircrafts, helicopters, and flight simulators, using time domain, frequency domain, and nonlinear HRV indices. Real and simulated flights produced significant autonomic changes. Some flights elicited autonomic nervous system responses that persisted up to 5 h after landing. During real flight, the most sensitive indices for identifying variations in pilot workload were root mean square of successive differences between normal heartbeats, standard deviation of interbeat interval of normal sinus beat (SDNN), ratio of low-frequency to high-frequency power, and Poincaré plot standard deviation perpendicular to the line of identity (SD1), whereas the interbeat interval (RR), SDNN, SD1, and Poincaré plot standard deviation along the line of identity (SD2) were the most sensitive indices when comparing segments of simulated flight with different levels of difficulty. This scoping review provided insight into the influence of flight on autonomic modulation in military pilots. Some key themes were highlighted: Increased sympathetic activity during flight, sensibility of different domains of HRV to flight demands, and autonomic changes during recovery time. Future research efforts may allow us to enhance the understanding of pilot's workload limits and to elucidate the optimal postflight recovery time.

Full-Term and Preterm Newborns Differ More Significantly in Photoplethysmographic Waveform Variability than Heart Rate Variability.

Features of cardiovascular autonomic regulation in infants are poorly studied compared with adults. However, the clinical significance of autonomic dysfunction in infants is very high. The goal of our research was to study the temporal and frequency-dependent features, as well as low-frequency synchronization in cardiovascular autonomic regulation in full-term vs. preterm newborns, based on the analysis of their heart rate variability (HRV) and photoplethysmographic waveform variability (PPGV). The study included three groups of newborns: 64 full-term newborns (with a gestational age at birth of 37-40 weeks) with a physiological course of the neonatal adaptation; 23 full-term newborns (with a gestational age at birth of 37-40 weeks) with a pathological course of the neonatal adaptation; and 17 preterm newborns (with a postconceptional age of 34 weeks or more). We conducted spectral analysis of HRV and PPGV, along with an assessment of the synchronization strength between low-frequency oscillations in HRV and in PPGV (synchronization index). We employed several options for the boundaries of the high-frequency (HF) band: 0.15-0.40 Hz, 0.2-2 Hz, 0.15-0.8 Hz, and 0.24-1.04 Hz. Preterm newborns had higher heart rate, RMSSD, and PNN50 values relative to both groups of full-term newborns. Values of SDNN index and synchronization index (S index) were similar in all groups of newborns. Differences in frequency domain indices of HRV between groups of newborns depended on the considered options of HF band boundaries. Values of frequency domain indices of PPGV demonstrated similar differences between groups, regardless of the boundaries of considered options of HF bands and the location of PPG signal recording (forehead or leg). An increase in sympathetic influences on peripheral blood flow and a decrease in respiratory influences were observed along the following gradient: healthy full-term newborns → preterm newborns → full-term newborns with pathology. Differences in frequency domain indices of autonomic regulation between the studied groups of newborns depended on the boundaries of the considered options of the HF band. Frequency domain indices of PPGV revealed significantly more pronounced differences between groups of newborns than analogous HRV indicators. An increase in sympathetic influences on peripheral blood flow and a decrease in respiratory influences were observed along the following gradient: healthy full-term newborns → preterm newborns → full-term newborns with pathology.

Osteoarthritis patients exhibit an autonomic dysfunction with indirect sympathetic dominance

BackgroundOsteoarthritis (OA) is a chronic degenerative joint disease causing limited mobility and pain, with no curative treatment available. Recent in vivo studies suggested autonomic alterations during OA progression in patients, yet clinical evidence is scarce. Therefore, autonomic tone was analyzed in OA patients via heart rate variability (HRV) measurements.MethodsTime-domain (SDRR, RMSSD, pRR50) and frequency-domain (LF, HF, LF/HF) HRV indices were determined to quantify sympathetic and parasympathetic activities. In addition, perceived stress, WOMAC pain as well as serum catecholamines, cortisol and dehydroepiandrosterone-sulphate (DHEA-S) were analyzed. The impact of the grade of disease (GoD) was evaluated by linear regression analysis and correlations with clinical data were performed.ResultsGoD significantly impacted the autonomic tone in OA patients. All time-domain parameters reflected slightly decreased HRV in early OA patients and significantly reduced HRV in late OA patients. Moreover, frequency-domain analysis revealed decreased HF and LF power in all OA patients, reflecting diminished parasympathetic and sympathetic activities. However, LF/HF ratio was significantly higher in early OA patients compared to late OA patients and implied a clear sympathetic dominance. Furthermore, OA patients perceived significantly higher chronic stress and WOMAC pain levels compared to healthy controls. Serum cortisol and cortisol/DHEA-S ratio significantly increased with GoD and positively correlated with WOMAC pain. In contrast, serum catecholamines only trended to increase with GoD and pain level.ConclusionsThis prospective study provides compelling evidence of an autonomic dysfunction with indirect sympathetic dominance in early and late knee OA patients for the first time based on HRV analyses and further confirmed by serum stress hormone measurements. Increased sympathetic activity and chronic low-grade inflammation in OA as well as in its major comorbidities reinforce each other and might therefore create a vicious cycle. The observed autonomic alterations coupled with increased stress and pain levels highlight the potential of HRV as a prognostic marker. In addition, modulation of autonomic activity represents an attractive future therapeutic option.Graphical abstract

Post-acute exercise cardiovagal modulation in older male adults with and without type 2 diabetes

PurposeWe examined heart rate variability (HRV) and baroreflex sensitivity (BRS) disease- and age-related response at 10-and 60-min after an acute high-intensity interval (HIIE) and moderate continuous exercise (MICE) in older adults with and without type 2 diabetes mellitus (T2DM) and healthy young adults.MethodsTwelve older male adults with (57–84 years) and without T2DM (57–76 years) and 12 healthy young male adults (20–40 years) completed an isocaloric acute bout of HIIE, MICE, and a non-exercise condition in a randomized order. Time and Wavelets-derived frequency domain indices of HRV and BRS were obtained in a supine position and offline over 2-min time-bins using Matlab.ResultsHIIE but not MICE reduced natural logarithm root mean square of successive differences (Ln-RMSSD) (d = − 0.85; 95% CI − 1.15 to − 0.55 ms, p < 0.001), Ln-high-frequency power (d = − 1.60; 95% CI − 2.24 to − 0.97 ms2; p < 0.001), and BRS (d = − 6.32; 95% CI − 9.35 to − 3.29 ms/mmHg, p < 0.001) in adults without T2DM (averaged over young and older adults without T2DM), returning to baseline 60 min into recovery. These indices remained unchanged in older adults with T2DM after HIIE and MICE. Older adults with T2DM had lower resting Ln-RMSSD and BRS than aged-matched controls (Ln-RMSSD, d = − 0.71, 95% CI − 1.16 to − 0.262 ms, p = 0.001; BRS d = − 3.83 ms/mmHg), 95% CI − 6.90 to − 0.76, p = 0.01).ConclusionsCardiovagal modulation following acute aerobic exercise is intensity-dependent only in adults without T2DM, and appears age-independent. These findings provide evidence of cardiac autonomic impairments in older adults with T2DM at rest and following aerobic exercise.

Chronic Sacral Nerve Stimulation Inhibits Visceral Hypersensitivity in Diarrhea–Predominant Irritable Bowel Syndrome Rats Model

ObjectiveSacral nerve stimulation (SNS) is emerging as a novel treatment for irritable bowel syndrome (IBS). However, its effects are limited, and the underlying mechanisms remain largely unknown. Materials and MethodsIn this study, rats were divided into three groups (n = 12 rats per group): 1) the SNS group; 2) the sham SNS group (the sham group for short); and 3) the control group. The SNS and sham groups were exposed to chronic and acute stress to establish an IBS model. Electrode implantation surgery was performed in rats with the IBS model. The SNS group received electrical stimulation for 30 minutes every day for seven days. Abdominal withdrawal reflex (AWR) was used to evaluate the effect of SNS on visceral sensitivity in diarrhea-predominant IBS (IBS-D) rats. The frequency domain of heart rate variability (HRV) was analyzed to assess the effect of SNS on regulating the autonomic function. The expression of transient receptor potential vanilloid 1 (TRPV1) in the colon, spinal cord, and hippocampus was detected by immunohistochemistry to explore the mechanism of SNS in IBS-D rats. ResultsCompared with the sham group, AWR scores were significantly decreased under different gas volumes of stimulation of 0.4, 0.6, and 0.8 ml for rectal distention in the SNS group (all p < 0.05). However, there was no significant difference <1.0 ml between the two groups (p > 0.05). Compared with the sham group, the frequency domain indexes of HRV were significantly altered. Normalized low-frequency power and low frequency-to-high frequency ratio were significantly decreased, and normalized high-frequency power was significantly increased in the SNS group (all p < 0.05). Moreover, the expression of TRPV1 in the spinal cord and colon in the SNS group was significantly decreased compared with the sham group (both p < 0.05). These results suggested that chronic SNS not only improved the visceral sensitivity and autonomic dysfunction but also decreased the expression of TRPV1 in the spinal cord-gut tissue in IBS-D rats. ConclusionChronic SNS was found to have an inhibitory effect on visceral hypersensitivity in IBS-D rats, providing experimental evidence for its potential clinical application in IBS.

Cardiovascular variations in patients with major depressive disorder versus bipolar disorder

BackgroundDifferentiating depression in major depressive disorder and bipolar disorder is challenging in clinical practice. Therefore, reliable biomarkers are urgently needed to differentiate between these diseases. This study's main objective was to assess whether cardiac autonomic function can distinguish patients with unipolar depression (UD), bipolar depression (BD), and bipolar mania (BM). MethodsWe recruited 791 patients with mood disorders, including 191 with UD, 286 with BD, and 314 with BM, who had been drug free for at least 2 weeks. Cardiovascular status was measured using heart rate variability (HRV) and pulse wave velocity (PWV) indicators via finger photoplethysmography during a 5-min rest period. ResultsPatients with BD showed lower HRV but higher heart rates than those with UD and BM. The PWV indicators were lower in the UD group than in the bipolar disorder group. The covariates of age, sex, and body mass index affected the cardiovascular characteristics. After adjusting for covariates, the HRV and PWV variations among the three groups remained significant. Comparisons between the UD and BD groups showed that the variable with the largest effect size was the frequency-domain indices of HRV, very low and high frequency, followed by heart rate. The area under the receiver operating characteristic curve (AUC) for each cardiovascular variable ranged from 0.661 to 0.714. The High-frequency index reached the highest AUC.Limitations.Cross-sectional design and the magnitude of heterogeneity across participants with mood disorders limited our findings. ConclusionPatients with BD, but not BM, had a greater extent of cardiac imbalance than those with UD. Thus, HRV may serve as a psychophysiological biomarker for the differential diagnosis of UD and BD.

Heart rate variability and haemodynamic function in individuals with hypertrophic cardiomyopathy.

Heart rate variability (HRV) is a measure of cardiac autonomic function. This study: (1) evaluated the differences in HRV and haemodynamic function between individuals with hypertrophic cardiomyopathy (HCM) and healthy controls, and (2) determined the relationship between HRV and haemodynamic variables in individuals with HCM. Twenty-eight individuals with HCM (n=7, females; age 54±15 years; body mass index: 29±5 kg/m2 ) and 28 matched healthy individuals (n=7 females; age 54±16 years; body mass index: 29±5 kg/m2 ) completed 5-minute HRV and haemodynamic measurements under resting (supine) conditions using bioimpedance technology. Frequency domain HRV measures (absolute and normalised low frequency power (LF), high frequency power (HF) and LF/HF ratio) and RR interval were recorded. Individuals with HCM demonstrated higher vagal activity (i.e., absolute unit of HF power (7.40±2.50 vs. 6.03±1.35 ms2 , p=0.01) but lower RR interval (914±178 vs. 1014±168 ms, p=0.03) compared to controls. Stroke volume (SV) index and cardiac index were lower in HCM compared to healthy individuals (SV, 33±9 vs. 43±7 ml‎/beat‎/m², p<0.01; cardiac index,2.33±0.42 vs. 3.57±0.82 L/min/m2 , p<0.01), but total peripheral resistance (TPR) was higher in HCM (3468±1027 vs. 2953±1050 dyn·s·m2 cm-5 , p=0.03). HF power was significantly related to SV (r=-0.46, p<0.01) and TPR (r=0.28, p<0.05) in HCM. Short-term frequency domain indices of HRV provide a feasible approach to assess autonomic function in individuals with HCM. Vagal activity, represented by HF power, is increased, and associated with peripheral resistance in individuals with HCM. This article is protected by copyright. All rights reserved.

Major Depressive Disorder and Chronic Fatigue Syndrome Show Characteristic Heart Rate Variability Profiles Reflecting Autonomic Dysregulations: Differentiation by Linear Discriminant Analysis.

Major depressive disorder (MDD) and chronic fatigue syndrome (CFS) have overlapping symptoms, and differentiation is important to administer the proper treatment. The present study aimed to assess the usefulness of heart rate variability (HRV) indices. Frequency-domain HRV indices, including high-frequency (HF) and low-frequency (LF) components, their sum (LF+HF), and their ratio (LF/HF), were measured in a three-behavioral-state paradigm composed of initial rest (Rest), task load (Task), and post-task rest (After) periods to examine autonomic regulation. It was found that HF was low at Rest in both disorders, but was lower in MDD than in CFS. LF and LF+HF at Rest were low only in MDD. Attenuated responses of LF, HF, LF+HF, and LF/HF to task load and an excessive increase in HF at After were found in both disorders. The results indicate that an overall HRV reduction at Rest may support a diagnosis of MDD. HF reduction was found in CFS, but with a lesser severity. Response disturbances of HRV to Task were observed in both disorders, and would suggest the presence of CFS when the baseline HRV has not been reduced. Linear discriminant analysis using HRV indices was able to differentiate MDD from CFS, with a sensitivity and specificity of 91.8% and 100%, respectively. HRV indices in MDD and CFS show both common and different profiles, and can be useful for the differential diagnosis.

Differential relationship of observer-rated and self-rated depression and anxiety scales with heart rate variability features.

Heart rate variability (HRV) is a known psychophysiological marker for diverse psychiatric symptoms. In this study, we aimed to explore the potential for clinical use of HRV by investigating the interrelationship between HRV indices and clinical measures mainly used to assess depressive and anxious symptoms. Participants who reported depressive and anxious symptoms were designated into the following groups: group 1, clinician-rated and self-rated depression; group 2, only self-rated depression; group 3, clinician-rated and self-rated anxiety; group 4, only self-rated anxiety. Statistical comparisons were performed between these groups to investigate the association between HRV and clinical measures. As a result, HRV variables showed significant correlations only with the clinician-rated assessments. Moreover, both time and frequency domain HRV indices were significantly different between groups 1 and 2, but groups 3 and 4 showed significant differences only in frequency domain HRV indices. Our study showed that HRV is an objective indicator for depressive or anxious symptoms. Additionally, it is considered a potential indicator for predicting the severity or state of depressive symptoms rather than of anxious symptoms. This study will contribute to increasing the diagnostic utility of discriminating those symptoms based on HRV in the future.

Heart Rate Variability Analysis on Electrocardiograms, Seismocardiograms and Gyrocardiograms of Healthy Volunteers and Patients with Valvular Heart Diseases.

Heart rate variability (HRV) is the physiological variation in the intervals between consecutive heartbeats that reflects the activity of the autonomic nervous system. This parameter is traditionally evaluated based on electrocardiograms (ECG signals). Seismocardiography (SCG) and/or gyrocardiography (GCG) are used to monitor cardiac mechanical activity; therefore, they may be used in HRV analysis and the evaluation of valvular heart diseases (VHDs) simultaneously. The purpose of this study was to compare the time domain, frequency domain and nonlinear HRV indices obtained from electrocardiograms, seismocardiograms (SCG signals) and gyrocardiograms (GCG signals) in healthy volunteers and patients with valvular heart diseases. An analysis of the time domain, frequency domain and nonlinear heart rate variability was conducted on electrocardiograms and gyrocardiograms registered from 29 healthy male volunteers and 30 patients with valvular heart diseases admitted to the Columbia University Medical Center (New York City, NY, USA). The results of the HRV analysis show a strong linear correlation with the HRV indices calculated from the ECG, SCG and GCG signals and prove the feasibility and reliability of HRV analysis despite the influence of VHDs on the SCG and GCG waveforms.

Day-night patterns in heart rate variability and complexity: differences with age and cardiopulmonary disease.

Heart rate variability (HRV) measures provide valuable insights into physiology; however, gaps remain in understanding circadian patterns in heart rate dynamics. We aimed to explore day-night differences in heart rate dynamics in patients with chronic cardiopulmonary disease compared with healthy controls. Using 24-hour heart rate data from patients with chronic obstructive pulmonary disease (COPD) and/or heart failure (n = 16) and healthy adult controls (older group: ≥50 years, n = 42; younger group: 20-49 years, n = 136), we compared day-night differences in conventional time and frequency domain HRV indices and a multiscale-entropy-based complexity index (CI1-20) of HRV among the 3 groups. Twenty-four-hour HRV showed significant day-night differences (marked with "△") among younger healthy (mean age: 34.5 years), older healthy (mean age: 61.6 years), and cardiopulmonary patients (mean age: 68.4 years), including change in percentage of adjacent intervals that differ > 50 ms (△pNN50), high frequency (△HF), normalized low frequency (△nLF), ratio (△LF/HF), and △CI1-20. Among these, △LF/HF (2.13 ± 2.35 vs 1.1 ± 2.47 vs -0.35 ± 1.25; P < .001) and △CI1-20 (0.15 ± 0.24 vs 0.02 ± 0.28 vs -0.21 ± 0.27; P < .001) were significant in each pairwise comparison following analysis of variance tests. Average CI1-20 was highest in younger healthy individuals and lowest in cardiopulmonary patients (1.37 ± 0.12 vs 1.01 ± 0.27; P < .001). Younger healthy patients showed a heart rate complexity dipping pattern (night < day), older healthy patients showed nondipping, and cardiopulmonary patients showed reverse dipping (night > day). As measures of 24-hour variability, traditional and complexity-based metrics of HRV exhibit large day-night differences in healthy individuals; these differences are blunted, or even reversed, in individuals with cardiopulmonary pathology. Measures of diurnal dynamics may be useful indices of reduced adaptive capacity in patients with cardiopulmonary conditions. Ma Y, Chang M-C, Litrownik D, Wayne PM, Yeh GY. Day-night patterns in heart rate variability and complexity: differences with age and cardiopulmonary disease. J Clin Sleep Med. 2023;19(5):873-882.

HEART RATE VARIABILITY IS AFFECTED IN YOUNG ADULT CELIAC PATIENTS, INDICATING AUTONOMIC DYSFUNCTION AND INCREASED CARDIOVASCULAR RISK

Aim: Celiac Disease (CD) is a common autoimmune disease that can present at any age with varied symptoms. Cardiac involvement including vascular and arrhythmic disturbances has an important prognostic value in patients with autoimmune disorders. The aim of this study was to evaluate the effects of CD on cardiovascular autonomic functions by measuring the indices of heart rate variability (HRV).&#x0D; Materials and Methods: Ninety-one CD patients and the ninety-three healthy volunteers were included in the study. We examined both time domain and frequency domain indices of HRV measured by 24-hour ambulatory electrocardiography.&#x0D; Results: All of the time domain and frequency domain HRV parameters, with the exceptions of low frequency power and low frequency to high frequency ratio, were significantly lower in patients with CD compared to the control (p &lt; 0.01). This difference retained for most of the HRV parameters when daytime and nighttime HRV parameters were compared separately. Correlation analysis revealed significant associations of HRV parameters with hemoglobin and ferritin levels and with duration of CD (p &lt; 0.01). No correlation was found between HRV parameters and anti-tissue transglutaminase IgA and IgG levels which indicate the activity of the disease.&#x0D; Conclusion: The study confirmed that patients with CD have reduced HRV, indicating the presence of objective autonomic dysfunction and increased cardiovascular risk.

Effect of Prenatal Yoga on Heart Rate Variability and Cardio-Respiratory Synchronization: A Prospective Cohort Study.

The objective was to assess the effects of prenatal yoga on heart rate variability (HRV) and cardio-respiratory synchronization, used as proxies of autonomic nervous system activity. Sixty-nine healthy pregnant women were included; 33 in a yoga group attending at least one 90-min yoga class weekly throughout pregnancy, and 36 controls not involved in formal pregnancy exercise programs. Measurements of the time domain (SDNN, standard deviation of regular R-R intervals, and RMSSD, square root of mean squared differences of successive R-R intervals) and frequency domain (ln(LF/HF), natural logarithm of low-frequency to high-frequency power) HRV indices, as well as cardio-respiratory synchronization indexes were performed once per trimester before and after yoga or 30-min moderate-intensity walk. A statistical comparison was performed using a three-way analysis of the variance (p < 0.05 significant). Both the time domain and frequency domain HRV indices showed significant shifts towards parasympathetic dominance following yoga when compared to the controls throughout pregnancy (p = 0.002 for SDNN, p < 0.001 for RMSSD, and p = 0.006 for ln(LF/HF), respectively). There was a statistically non-significant trend towards higher synchronization between respiratory frequency and heart rate following yoga vs. controls (p = 0.057). Regular prenatal yoga was associated with enhanced parasympathetic activation persisting throughout pregnancy.

Pupillary Responses Reveal Autonomic Regulation Impairments in Patients With Central Serous Chorioretinopathy.

PurposeThis study assessed the autonomic nervous system in patients with central serous chorioretinopathy (CSC) by simultaneously measuring pupillary responses and heart rate variability (HRV).MethodsWe recruited 33 patients with CSC and 26 age- and sex-matched healthy controls. Using a pupillometry and acceleration plethysmography system, we measured the participants’ pupillary light reflex and HRV simultaneously, and compared the following parameters between the two groups: the pupil diameters, diameter changes, and time and frequency domain HRV indices (high frequency power: HF; low frequency power: LF; log LF/HF ratio). Additional data from the Profile of Mood States (POMS) and pupillary responses during mental tasks were also analyzed.ResultsThe CSC group had a significantly lower constriction amplitude and a higher re-dilation ratio compared with the control group, indicating parasympathetic inhibition and sympathetic activation. For the HRV measures, the CSC group demonstrated significantly lower HF and higher LF and log LF/HF ratio, indicative of higher sympathetic activity. The CSC group also showed significantly larger pupil dilation during tasks of moderate difficulty, and higher negative/lower positive POMS mood scores. Further analyses also revealed that the baseline pupil diameter was significantly larger in patients with active as opposed to chronic CSC.ConclusionsPupillary responses and HRV measures both revealed sympathetic activation and parasympathetic attenuation in patients with CSC. Larger pupil dilation during mental tasks in CSC could be a potential marker of psychophysiological stress.

The Impact Of Varying Blood Flow Restriction Cuff Size On Cardiac Autonomic Modulation In Healthy Males

Blood flow restriction (BFR) training is commonly utilized to stimulate skeletal muscle hypertrophy and assist in strength gains in various populations, ranging from healthy, athletic, clinical, and elderly populations. BFR has the potential to influence the sympathetic and parasympathetic interaction by stimulating acute changes in the vascular endothelium, thereby altering cardiac autonomic modulation (CAM). Heart rate variability (HRV) is a non-invasive way to assess changes in CAM. What is unknown is the influence BFR may have on CAM due to the changes in venous and arterial pressure. PURPOSE: To determine if different BFR cuff sizes and materials alter CAM when assessed in healthy young men. METHODS: Twenty healthy males (n = 20 males, Age 25 ± 5 years, HR 66 + 11.3 bpm, SBP 125.1 + 13.4 mmHg, DBP 75.1 + 12.5 mmHg) completed a randomized, counter-balanced, cross-over design that utilized a widely-employed wide rigid (WR) cuff, along with the largest (NE) and manufacturer recommended sizes (NER) of a novel narrow-elastic cuff. HRV was measured in the supine position at baseline and amidst all three BFR cuffs at 80% arterial occlusion pressure using an elastic belt and Bluetooth monitor (Polar H7). CardioMood software was used to process HRV variables high frequency (HF), low frequency (LF), total power (TP) was assessed for frequency domain, and standard deviation of all NN intervals (SDNN) and the square root of the mean of the squares of successive R-R interval differences (RMSSD) for the time domain. The data were analyzed with SPSS using a repeated-measures ANOVA to examine differences between dependent variables, including selected time and frequency domain HRV indices. RESULTS: HRV frequency domain variables LF, HF, LF/HF, and TP, and time domain, SDNN, and RMSSD variables were not significantly altered with WR, NE, or NER cuff protocols when compared to baseline. There were no significant differences between cuff protocols. CONCLUSION: There were no changes in CAM with BFR cuff protocols in healthy young men. The lack of changes indicates that changes in the venous and arterial pressure ratio due to BFR were not great enough to offset the sympathetic and parasympathetic systems.

The Effect of Breathing Route on Heart Rate Variability—A within Subject Comparative Study

Background: The effect of traffic related emissions on Heart Rate Variability (HRV) has been previously demonstrated. However, the results of different studies on the relationship between ambient pollutants and specifically carbon monoxide (CO) on HRV are inconclusive and appear to reflect personal differences. The differences in methodology including breathing style and participants under study can possibly attribute to this variability. The aim of the present study is to assess the effect of the breathing route (Nasal/Oral) on the relationship between CO concentration and HRV. Methodology: Forty healthy participants (25 females, 15 males) between the ages of 15 - 50 years were included in the study. The participants strolled in a central bus station, staying for 10 minutes in three designated locations alternating nasal and oral breathing. CO concentration and HRV were continuously monitored. Frequency (LnLF, LnHF, LnLF/HF) and time domain (LnSDNN, LnRMSSD) HRV indices were computed. Analysis: MANCOVA, with HRV indices being the dependent variables and CO, gender and age being the independent variables was employed. Results: Significant interaction effects between breathing route and CO, and breathing route and gender on HRV (LnLF/HF) were found (p = 0.04 and 0.01 respectively). Both CO and age were found to affect LnSDNN and LnRMSSD. Conclusion: Breathing route emerges as a possible modifier of the relationship between air pollution and HRV and thus contributes to interpersonal differences obtained in studies investigating the effect of environmental pollution and HRV.

The Association Between Cardiovascular Autonomic Function and Changes in Kidney and Myocardial Function in Type 2 Diabetes and Healthy Controls.

BackgroundThe mechanisms linking cardiovascular autonomic neuropathy, diabetic kidney disease and cardiovascular mortality in type 2 diabetes are widely unknown. We investigated the relationship between baseline cardiovascular autonomic function and changes in kidney and myocardial function over six years in patients with type 2 diabetes and healthy controls.Methods Post-hoc analysis of a cohort study in 24 patients with type 2 diabetes and 18 healthy controls. Baseline determinants were cardiovascular autonomic reflex tests (heart rate response to: standing (30:15); deep breathing (E:I); and the Valsalva test) and time- and frequency-domain heart rate variability indices. Outcomes were changes in estimated glomerular filtration rate (eGFR), albuminuria, myocardial flow reserve (MFR) measured by cardiac 82Rb Positron emission tomography computed tomography (PET/CT), and coronary artery calcium score (CACS).ResultsMean age at inclusion was 61 ± 10 years and 36% were female. Mean follow up time was 6 ± 0 years. A lower response in heart rate to the Valsalva test (corresponding to weaker autonomic function) was associated with a larger decline in eGFR (p=0.04), but not significantly after adjustment for sex, baseline age, smoking status, systolic blood pressure, heart rate, HbA1c, body mass index and baseline eGFR (p=0.12). A higher baseline response in heart rate to standing (30:15) was associated with a larger decline in myocardial flow reserve in the unadjusted analysis (p=0.02) and after adjustment (p=0.02). A higher response in heart rate to the Valsalva maneuver was associated with a larger increase in CACS (p = 0.02), but the association became insignificant after adjustment (p = 0.16).ConclusionA lower response in heart rate to the Valsalva test was associated with a larger decline in kidney function, indicating that autonomic dysfunction may predict future loss of kidney function. However, we did not find any association between lower values in cardiovascular autonomic function at baseline and a worsening in albuminuria, myocardial function, or atherosclerotic burden.

Abstract 11335: Does Reduced Parasympathetic Heart Rate Variability Promote Obesity in Children?

Introduction: Considering the contribution of the autonomic nervous system (ANS) in regulating both energy expenditure and energy intake, assessment of heart rate variability (HRV) may elucidate the etiology and adaptive processes in the development of obesity. Variations in the cardiac ANS are associated with changes in energy balance and eating behaviours, highlighting the potential key function of the ANS in the etiology of obesity. While it is broadly accepted that obesity impacts HRV, potential impacts of HRV patterns on obesity remain unexplored. We hypothesize that certain HRV patterns increase risk of excess weight in children. Methods: Participants included 406 White youth from the QUALITY cohort (56% boys). Children were considered at risk of CVD due to confirmed parental obesity status. Time- and frequency-domain HRV indices derived from short-term ECG recordings (SDNN, RMSSD, pNN50, LF, HF, and LF/HF ratio) were analyzed at baseline (mean = 9.6 years, SD = 0.9). Adiposity at 2-year follow-up was evaluated through dual-energy X-ray absorptiometry. Total body fat (BF) and BF distribution were captured; central adiposity was estimated using the android-to-gynoid ratio. Prospective associations between HRV at baseline and adiposity at 2-year follow-up were estimated using regression models including weights for well-established confounders (difference in adiposity measures over time, sex, age, sexual maturity, and physical activity). Results: 8-10 year olds with a sympathovagal imbalance described by a sympathetic predominance (LF/HF) presented with higher BF (β = 3.32, p &lt; 0.001) and higher android-to-gynoid ratio (β =0.03, p&lt;0.001) at age 10-12 years. Furthermore, lower levels of parasympathetic indices at age 8-10 years predicted higher BF (RMSSD: β = -0.09, p &lt; 0.01; pNN50: β = -0.13, p &lt; 0.01) and higher android-to-gynoid ratio (RMSSD: β -0.001, p &lt; 0.05; pNN50: β = -0.001, p &lt; 0.01) two years later. Conclusions: Impaired cardiac ANS modulation appears associated with the occurrence of childhood obesity two years later. A sympathetic predominance paired with reduced parasympathetic indices in otherwise healthy children may foreshadow pathophysiological processes that lead to obesity and may help to identify intervention targets.

Acute effects of long-distance races on heart rate variability and arterial stiffness: A systematic review and meta-analysis

ABSTRACT This study systematically reviewed and quantified the effects of running a long-distance race (LDR) on heart rate variability (HRV) and arterial stiffness (AS). All types of races of a distance equal to or greater than a marathon (≥42.2 km) were included. A total of 2,220 articles were identified, 52 were included in the qualitative analysis, and 48 were meta-analysed. The standardised mean difference pre- and post-race of various time-domain and frequency-domain indices of HRV, mean arterial blood pressure (MAP), systolic blood pressure (SBP), diastolic blood pressure (DBP) and carotid-femoral pulse wave velocity (cfPWV) was calculated. Regarding HRV, there was a significant decrease in most of the variables considered as markers of parasympathetic activity, indicating a shift of autonomic balance towards a reduced vagal tone. Regarding vascular variables, there was a significant drop in blood pressure and reduced AS. In conclusion, running an LDR seems to have a considerable acute effect on the autonomic nervous system, haemodynamics, and vascular properties. The observed effects could be categorised within the expected acute responses to long-lasting, strenuous exercise.

The effect of moderate versus high intensity exercise on heart rate variability in sedentary office workers

Background: Sedentary behavior is one of the leading modifiable risk factors for cardiovascular disease and all-cause mortality. Physical exercise exerts beneficial physiological effects on cardiovascular fitness. Different grades of physical exercise have different effects on cardiovascular health. Objective: To compare the effect of moderate and high intensity exercise training on heart rate variability (HRV) in sedentary office workers. Methods: This study was conducted on 40 healthy sedentary volunteers aged between 20-40 years of both the genders. Participants were distributed into two groups of 20 subjects each. Subjects of group I and group II performed moderate intensity and high intensity exercise respectively on bicycle ergometer for 12 weeks. Their 5- minute ECG recording was done by three channel physiograph, and frequency domain indices of HRV and heart rate (HR) were analyzed and compared before and after exercise training. Their blood pressure was also recorded and compared before and after exercise training. Independent sample t-test and paired sample ttest were used for statistical analysis. Results: HF, systolic and diastolic blood pressure reduced significantly after exercise in group II (p=0.015, 0.005, and 0.015 respectively) while HR and LF/HF ratio reduced in both group I and group II (p=0.000 for HR, and 0.034, 0.001 for LF/HF). The decrease in HR was greater after high intensity exercise than moderate intensity exercise (p= 0.025). Conclusion: Parasympathetic activity improves after moderate and high intensity exercise but improvement is more after high intensity exercise training. Therefore, high intensity exercise training is more beneficial than moderate intensity exercise training. J Bngladesh Soc Physiol 2021;16(1): 16-23