Heart Rate Variability Measures Research Articles

Correlation of serum zinc and magnesium with reduced heart rate variability in male Parkinson’s disease patients

Background: Parkinson’s disease (PD) is a neurological disorder associated with altered cardiac autonomic function. Heart rate variability (HRV) analysis is a tool to assess the cardiac autonomic status. Altered serum zinc (Zn) and magnesium (Mg) levels are observed in PD. The serum Zn and Mg alteration is associated with nerve function impairment. Objective: To evaluate the relationship between serum zinc, magnesium, and time domain measures of HRV in male patients with PD. Methods: This observational analytical cross-sectional study was conducted in 2023on 30 newly diagnosed male PD patients aged 50-60 years. In this study, 30 healthy volunteers were the control. The 30 patients were divided into different categories based on serum mineral levels. The HRV was recorded by Power Lab 8/35, AD Instruments, Australia and the time domain measures of HRV were used in data analysis. The serum Zn and Mg levels were measured by atomic absorption spectrophotometry. Independent sample ‘t’ test and Pearson’s correlation coefficient test were used for statistical analysis and p<0.05 was considered statistical significance. Results: Significantly higher mean HR (Heart rate) (p<0.01) and significantly lower mean RR (Normal to normal QRS complex) interval,CVRR (Coefficient variation of RR interval) (p<0.01), SDRR (Standard deviation of the RR intervals), SDSD (Standard deviation of the difference between successive RR intervals), RMSSD (Square root of mean squared differences of successive RR intervals), pRR50% (Proportion of RR interval with duration >50 ms) (p<0.001)were observed in PD patients compared to control. In PD patients, significantly lower (p<0.001) serum Zn and significantly higher (p<0.01) serum Mg were observed compared to control. In addition,significant decrement was observed in SDRR, CVRR (p<0.05), SDSD, RMSSD, and pRR50% (p<0.01) in hypozincemic PD patients compared to normozincemic patients. On correlation analysis, significant positive correlations of serum Zn were observed with SDRR (p<0.05),SDSD (p<0.001), RMSSD (p<0.001) and pRR50% (p<0.01). Moreover,serum Mg was positively correlated with SDRR (p<0.05) in PD patients. Conclusion: Hypozincemia and magnesium were directly related to reduced HRV in male PD patients. J Bangladesh Soc Physiol 2023;18(2): 63-71

Effect of slow breathing exercise on heart rate variability: A non linear analysis in female major depressive disorder patients

Background: Major depressive disorder (MDD) is a mental health problem, associated with cardiac autonomic dysfunction. Cardiac autonomic function (CANF) can be assessed by non linear analysis of heart rate variability (HRV), a simple non-invasive software based analytical method. Yoga based slow breathing exercise (SBE) has role to improve autonomic dysfunction in some disease condition. Objective: To observe the effect of SBE on non linear measures of HRV in newly diagnosed female MDD patients. Methods: The quasi-experimental study was conducted in 2023 on sixty (60) newly diagnosed female MDD patients of 20-40 years aged, collected from the Department of Psychiatry, Bangabandhu Sheikh Mujib Medical University (BSMMU). Among them 30 were assigned with SBE and remaining 30 patients without SBE were followed up after 90 days. Both patient groups received conventional treatment during this period. Thirty apparently healthy female subjects with similar age & BMI were included as control for comparison and they did not perform breathing exercise. Data were taken at baseline and after 90 days in all the subjects. CANF was assessed by analysing non linear (poincare plot) of HRV by using ECG based data acquisition device, Power lab 8/35. Data were expressed as mean±SD. For statistical analysis, ANOVA followed by post hoc Bonferroni test and paired sample “t” test were used. Results: At baseline pulse rate and BP were significantly lower in both group of MDD patients compared to control. The pre-intervention values of standard deviation of short term RR interval variability (SD1), standard deviation of long term RR interval variability (SD2) and ratio of short term and long term RR interval variability (SD1/SD2) were found significantly (p< 0.001) lower in MDD patients compared to healthy control. Following 90 days of SBE, significant (p< 0.001, p< 0.05) rise of these poincare plot parameters was noted in MDD patients whereas no significant changes of these parameters were observed in patients without SBE after 90 days of follow-up. Moreover, the pulse BP almost reached control level though the non linear parameters were still below control level after 3 months of SBE.. Conclusion: Autonomic dysfunction occured in MDD patients SBE can improve cardiac autonomic dysfunction and sympathovagal balance in female MDD patients. J Bangladesh Soc Physiol 2023;18(2): 45-52

Wooden Interiors Improve Heart Rate Variability-Derived Psychophysiological Well-Being: An Acute Cross-Over Study

Mental health is a significant public concern. Given that individuals spend extended periods indoors, understanding the psychophysiological health effects of indoor materials on well-being is crucial. This study compared the effects of wooden and resin plaster rooms on psychophysiological well-being. Well-being was assessed using heart rate variability measurements and an affective well-being questionnaire. Subjective perceptions were also evaluated using a semantic differential questionnaire. The results indicated higher heart rate variability in the wooden room compared to the reference room. Participants breathed about one breath per minute more slowly in the wooden room, with a negative correlation between heart rate variability and respiratory rate. Positive affect was elevated, and negative affect was reduced in the wooden room, which was also perceived more favorably in sensory evaluations. The findings suggest that wooden interiors are preferred over artificial materials, enhancing both physiological and psychological well-being.

Decreased ventricular repolarization variability in one-year-olds of gestational diabetes mothers

BackgroundGestational diabetes mellitus (GDM) is currently the most common medical complication in pregnancy, affecting approximately 13 % of all pregnant women. Although long-term effects on the offspring are still unclear, previous studies indicate ventricular myocardial changes. ObjectivesThe aim of our study was to investigate whether early biomarkers such as QT interval variability (QTV) are sensitive enough to predict these structural changes in children of GDM mothers. MethodsWe focused on children of GDM mothers. Healthy children of mothers without GDM served as controls. All of them were examined at the German Heart Center, Munich, Germany. Heart rate variability (HRV) and QTV measures were extracted from 10 to 15 min Einthoven II electrocardiograms, split into 5 min windows, to characterize the effects of possible autonomic nervous system alterations and cellular ventricular mutations. Results75 children were included in this prospective observational case-control study; 42 of them were children of GDM mothers. The median age at the examination was 12 months (11–13 months). We found decreased QTV as a measure of ventricular repolarization variability in one-year-olds of GDM mothers compared to healthy controls (p < 0.05). ConclusionWe have found increased very low frequency HRV in females and decreased QTV in male children of GDM mothers, which suggests diverse responses and could reflect increased sympathetic tone and altered ventricular myocardium at a cellular level, respectively. Further work is required to understand the long-term significance of these findings in terms of providing an easy-to-use and cost-effective technology for early diagnosis of myocardial damage.

The Validity of Apple Watch Series 9 and Ultra 2 for Serial Measurements of Heart Rate Variability and Resting Heart Rate.

The widespread use of wearable devices has enabled continuous monitoring of biometric data, including heart rate variability (HRV) and resting heart rate (RHR). However, the validity of these measurements, particularly from consumer devices like Apple Watch, remains underexplored. This study aimed to validate HRV measurements obtained from Apple Watch Series 9 and Ultra 2 against the Polar H10 chest strap paired with the Kubios HRV software, which together served as the reference standard. A prospective cohort of 39 healthy adults provided 316 HRV measurements over a 14-day period. Generalized Estimating Equations were used to assess the difference in HRV between devices, accounting for repeated measures. Apple Watch tended to underestimate HRV by an average of 8.31 ms compared to the Polar H10 (p = 0.025), with a mean absolute percentage error (MAPE) of 28.88% and a mean absolute error (MAE) of 20.46 ms. The study found no significant impact of RHR discrepancies on HRV differences (p = 0.156), with RHR showing a mean difference of -0.08 bpm, an MAPE of 5.91%, and an MAE of 3.73 bpm. Equivalence testing indicated that the HRV measurements from Apple Watch did not fall within the pre-specified equivalence margin of ±10 ms. Despite accurate RHR measurements, these findings underscore the need for improved HRV algorithms in consumer wearables and caution in interpreting HRV data for clinical or performance monitoring.

Impact of age and sex on heart rate variability and cardiometabolic function in healthy adults

Heart rate variability (HRV) is a non-invasive measure of cardiac autonomic function. A clearer understanding as to whether resting autonomic function represented by HRV could be associated with changes in peak exercise cardiac function remains unanswered. This study evaluated the effect of age and sex on HRV, cardiometabolic function, and determined the correlation between HRV and cardiac function in healthy individuals. Sixty-eight participants (age range: 19–78 years old, females, n = 28) were recruited. Participants were stratified according to age (younger (<40 years old, n = 43, females, n = 17) and older age groups (>55 years old, n = 25, females, n = 11). Firstly, HRV was measured using non-invasive impedance cardiography method (TaskForce, CNSystems, Graz, Austria) and recorded at rest (supine position) for 30 min. HRV measures included: low frequency (LF) power, high frequency (HF) power (both normalised (nu) and absolute units (ms2)) and LF/HF ratio. Participants then completed a progressive cardiorespiratory exercise test using a semi-recumbent cycle ergometer (Corival, Lode, Groningen, Netherlands) with simultaneous gas exchange measurements (Metalyzer 3B, Cortex, Leipzig, Germany). Cardiac function was represented by peak exercise cardiac power output index (CPO). After controlling for body mass index and physical activity, males had significantly higher mean vales of RR interval than females (males = 1043 ± 165; females = 952 ± 128 ms, p = 0.02). There was no significant main effect of age, sex or their interaction on any of the other HRV measures. In younger and older females, resting RR interval had a significant relationship with peak exercise CPO (young females: r = 0.54, p < 0.05; old females: r = 0.81, p < 0.01). There was also a significant relationship between resting HF power and peak exercise CPO in younger females (r = 0.70, p < 0.01). HRV was not influenced by age but RR interval was associated with peak exercise CPO in females regardless of age, whilst HF power was significantly associated with CPO in younger females only.

Feasibility of Early Assessment for Psychological Distress: HRV-Based Evaluation Using IR-UWB Radar.

Mental distress-induced imbalances in autonomic nervous system activities adversely affect the electrical stability of the cardiac system, with heart rate variability (HRV) identified as a related indicator. Traditional HRV measurements use electrocardiography (ECG), but impulse radio ultra-wideband (IR-UWB) radar has shown potential in HRV measurement, although it is rarely applied to psychological studies. This study aimed to assess early high levels of mental distress using HRV indices obtained using radar through modified signal processing tailored to reduce phase noise and improve positional accuracy. We conducted 120 evaluations on 15 office workers from a software startup, with each 5 min evaluation using both radar and ECG. Visual analog scale (VAS) scores were collected to assess mental distress, with evaluations scoring 7.5 or higher classified as high-mental distress group, while the remainder formed the control group. Evaluations indicating high levels of mental distress showed significantly lower HRV compared to the control group, with radar-derived indices correlating strongly with ECG results. The radar-based analysis demonstrated a significant ability to differentiate high mental distress, supported by receiver operating characteristic (ROC) analysis. These findings suggest that IR-UWB radar could be a supportive tool for distinguishing high levels of mental stress, offering clinicians complementary diagnostic insights.

Heart Rate Variability Monitoring in Special Emergency Response Team Anaerobic-Based Tasks and Training

The Law enforcement profession is known to impart high stress. Members of Special Weapons and Tactics (SWAT) teams are allocated particularly demanding law enforcement operations and may therefore attain high fitness levels but may accumulate excessive stress. Heart rate variability (HRV), an assessment of time differences between heartbeats, likely indicates holistic load in field settings. To date, though, little research measuring HRV has been conducted involving SWAT units. The purpose of this study was to explore HRV measurements following (1) annual firearms qualification and (2) potential stress exposure with respect to completion time on an anaerobically taxing obstacle course. Officers with greater obstacle course performance were hypothesized to also exhibit greater HRV. HRV was also expected to stratify personnel more effectively than heart rate. Prospective 3-lead ECGs were obtained from a cohort of male SWAT operators (n = 15) with 5.2 ± 4.3 years of experience at three time points throughout one training day. HRV was assessed by time, frequency, and non-linear domains. Differences between baseline and post-training values were significant as assessed by the Wilcoxon signed-ranks test for heart rate, SDRR, LF, HF, and SD2. An enter-method linear regression model predicted post-training HF HRV by obstacle course time; r2 = 0.617, F (1,6) = 9.652, p = 0.021. Anaerobic performance may be highly valuable in SWAT units. HRV analysis may also be beneficial in measuring the psychophysiological impact of SWAT activities.

Associations between Sleep Duration and Autonomic Nervous System Regulation in Patients with Probable Alzheimer's Disease: A Cross-Sectional Pilot Study.

In this study, we aimed to investigate the relationships between sleep duration and autonomic nervous system (ANS) regulation. This cross-sectional pilot study included 27 older patients with probable Alzheimer's disease who were hospitalized at a psychiatric center. We measured heart rate variability to assess ANS regulation at night, evaluated dementia severity via the Clinical Dementia Rating scale, and obtained sleep duration data from sleep diaries maintained by psychiatric nurses. The data were analyzed using repeated-measures generalized linear models with age, sex, dementia severity, hypertension status, and medication use (antipsychotics) as covariates. A sleep duration of 6-9 h per night compared to shorter than 6 h was associated with a greater increase in parasympathetic nervous system activity (p = 0.03), and a sleep duration longer than 9 h was associated with a decrease sympathovagal balance (p = 0.02). In addition, we observed an inverted U-shaped association between sleep duration and ANS regulation. In this pilot study, we demonstrated that a sleep duration of 6-9 h per night may be beneficial for ANS regulation; however, the present study involved only a few participants and had some limitations. Additional research with a larger cohort is needed to confirm these findings.

Epigallocatechin gallate enhances sympathetic heart rate variability and decreases blood pressure in obese subjects: a randomized control trial

This study aimed to investigate effects of epigallocatechin gallate (EGCG) on blood pressure (BP) and autonomic nervous system, indicated by 5-min heart rate variability (HRV) measurement in obese subjects, and determine correlations of BP with metabolic factors. In a double-blind, randomized controlled trial, obese subjects (n = 30) were randomly allocated to receive 150 mg EGCG (n = 15) or placebo (n = 15) twice a day without dietary restrictions. After 8-week EGCG treatment, systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP) significantly decreased, while the low-frequency (LF) to high-frequency power (HF) ratio (LF/HF ratio) significantly increased (P < 0.05 all), indicating a shift toward sympathetic dominance, either directly or indirectly after BP lowering. SBP had positive correlations with obesity parameters, leptin, insulin, and insulin resistance but had a negative correlation with insulin sensitivity. DBP was positively correlated with age and HF in normalized unit, but negatively correlated with height and LF in ms2. High-density lipoprotein cholesterol (HDL-C) was negatively correlated with SBP, DBP, and MAP reflecting its protective effect against elevated BP. In conclusion, the 8-week EGCG treatment decreased BP and increased the LF/HF ratio, reflecting increased sympathetic activity, either a direct EGCG effect or an indirect compensatory response following BP reduction.

Heart rate variability in horses with and without severe equine asthma.

Equine asthma in severe form (severe equine asthma [sEA]) shares remarkable similarities with human asthma. Human studies detected changes in the autonomic nervous system function in asthmatic patients based on heart rate variability (HRV) analysis. Observational study. To investigate the relationship between sEA and HRV in horses. Twenty horses diagnosed with sEA and 20 asymptomatic (non-sEA) horses were investigated. SEA horses showed clinical signs. The RR intervals of the ECG were recorded for 1 h at rest between 9 AM and 11 AM using a heart rate (HR) monitor. HRV data were calculated using Kubios software. Parameters recorded for the sEA and non-sEA groups were compared using one-way MANOVA model. The significance level was set at α = 0.05. SD2 (mean 99.6 ± SD 25.3 vs. 42.5 ± 17.1), SDNN (82.7 ± 20.7 vs. 41.3 ± 14.3), TINN (398.1 ± 104.9 vs. 209.3 ± 71.9), SD2/SD1 ratio (1.7 ± 0.2 vs. 1.1 ± 0.3), Total power (4740.2 ± 1977.9 vs. 1503.0 ± 1179.3), LF (2415.3 ± 1072.4 vs. 707.4 ± 649.9), SD1 (60.9 ± 15.9 vs. 39.2 ± 14.1), RMSSD (86.0 ± 22.6 vs. 55.3 ± 19.8) and HF (1575.8 ± 902.5 vs. 578.1 ± 491.1) were lower in sEA horses compared with the non-sEA horses (p < 0.01 for each variable). SD2, SDNN, TNN, the SD2/SD1 ratio and Total power showed the greatest discriminatory power in differentiating the sEA and non-sEA groups. Small sample size. Our findings indicate that like humans, asthmatic horses show an overall reduction in autonomic control. A relative increase of the parasympathetic modulation of the heart was also observed. After further investigations, HRV measurement might be a non-invasive approach to monitor autonomic nervous system responses of sEA horses.

Orthostatic testing for heart rate and heart rate variability monitoring in exercise science and practice.

Orthostatic testing, involving the transition from different body positions (e.g., from lying or sitting position to an upright or standing position), offers valuable insights into the autonomic nervous system (ANS) functioning and cardiovascular regulation reflected through complex adjustments in, e.g., measures of heart rate (HR) and heart rate variability (HRV). This narrative review explores the intricate physiological mechanisms underlying orthostatic stress responses and evaluates its significance for exercise science and sports practice. Into this matter, active orthostatic testing (e.g., active standing up) challenges the cardiovascular autonomic function in a different way than a passive tilt test. It is well documented that there is a transient reduction in blood pressure while standing up, leading to a reflex increase in HR and peripheral vasoconstriction. After that acute response systolic and diastolic blood pressures are usually slightly increased compared to supine lying body position. The ANS response to standing is initiated by instantaneous cardiac vagal withdrawal, followed by sympathetic activation and vagal reactivation over the first 25-30 heartbeats. Thus, HR increases immediately upon standing, peaking after 15-20 beats, and is less marked during passive tilting due to the lack of muscular activity. Standing also decreases vagally related HRV indices compared to the supine position. In overtrained endurance athletes, both parasympathetic and sympathetic activity are attenuated in supine and standing positions. Their response to standing is lower than in non-overtrained athletes, with a tendency for further decreased HRV as a sign of pronounced vagal withdrawal and, in some cases, decreased sympathetic excitability, indicating a potential overtraining state. However, as a significant main characteristic, it could be noted that additional pathophysiological conditions consist in a reduced responsiveness or counter-regulation of neural drive in ANS according to an excitatory stimulus, such as an orthostatic challenge. Hence, especially active orthostatic testing could provide additional information about HR(V) reactivity and recovery giving valuable insights into athletes' training status, fatigue levels, and adaptability to workload. Measuring while standing might also counteract the issue of parasympathetic saturation as a common phenomenon especially in well-trained endurance athletes. Data interpretation should be made within intra-individual data history in trend analysis accounting for inter-individual variations in acute responses during testing due to life and physical training stressors. Therefore, additional measures (e.g., psychometrical scales) are required to provide context for HR and HRV analysis interpretation. However, incidence of orthostatic intolerance should be evaluated on an individual level and must be taken into account when considering to implement orthostatic testing in specific subpopulations. Recommendations for standardized testing procedures and interpretation guidelines are developed with the overall aim of enhancing training and recovery strategies. Despite promising study findings in the above-mentioned applied fields, further research, thorough method comparison studies, and systematic reviews are needed to assess the overall perspective of orthostatic testing for training monitoring and fine-tuning of different populations in exercise science and training.

Heart rate variability activity in soccer athletes after a musculoskeletal injury.

The aim of this study is to analyse the adaptations of the autonomic nervous system after a musculoskeletal injury, obtained by measuring heart rate variability in athletes. It was hypothesized that there is an alteration in heart rate variability after a musculoskeletal injury. Cohort study. 15 semi-professional soccer players from three football teams, aged between 21 and 33 (mean age: 29.4 ± 3.31 years), with a recent musculoskeletal injury. Heart rate variability was collected using the Polar m200 and the chest strap H10 in two moments: within 72 h after the injury and between 5 and 7 days after full return-to-play. Results show differences between T1 and T2 (p ≤ 0.05) in low-frequency power (n.u.) (p = 0.001) and high-frequency power (n.u.) (p = 0.001), in low-frequency/high-frequency ratio (p = 0.001) and in high-frequency power (ms2) (p = 0.017) measures. No statistical differences were found in low-frequency power (ms2) (p = 0.233). The low frequency power (n.u.) was significantly lower after injury compared with LF power (n.u.) values after full return-to-play. In high-frequency power there was a significant difference between both moments with high values after injury. The use of heart rate variability therefore seems to be promising to detect an imbalance in the autonomic nervous system and help clinical departments to identify a possible non-traumatic musculoskeletal injury. Further research should be performed considering a wide range of musculoskeletal injuries and to establish baseline values of the athletes.

Heart Rate Variability Estimation based on RFID Tag-Pair in Dynamic Environments

With the rapid development of smart healthcare, accurate Heart Rate Variability (HRV) estimation for the early detection of diseases has become a hot research topic. Advanced work uses the wireless signal to estimate the heartbeat in a contact-free way, which usually cannot separate multiple users or work in a dynamic environment. In this paper, we propose a lightweight heartbeat-sensing method based on RFID tag pairs, which focuses on HRV extraction in a more general sensing scenario. Based on the tag-pair design, we build a novel heartbeat and respiration model to describe the signal relationship between the two tags from the time and space domains. Based on the model, we propose a Calibrated Temporal-Spatial IQ-Shaping-based signal cancellation algorithm to cancel the respiration and extract the heartbeat. To remove the interference in dynamic measurement, we build an IQ-based signal model via a Principal Component Analysis-based interference estimation. To reduce the statistical error in HRV extraction, we further design a neural network to predict the HRV index. We have implemented a system prototype in a real environment with COTS RFID devices. Extensive experiments show that our system can achieve a median RMSSD error of 7.51ms, which satisfies the medical demand in HRV measurement.

Heart Rate Variability in Elite Team Sports: A Systematic Review

Background: Heart rate variability (HRV) is recognized as a crucial indicator of autonomic nervous system function and is valuable in sports science for monitoring athlete health and performance. This systematic review investigates the use of HRV in elite team sports to monitor training adaptations, athlete status, and overall health. The purpose is to consolidate recent findings and provide a comprehensive understanding of HRV's application in elite team sports. Methods: The review was conducted in accordance with PRISMA guidelines and registered in PROSPERO (CRD42023431208). A comprehensive search was performed across PubMed, Science Direct, Web of Science, and Google Scholar, covering studies from January 2013 to November 2023. Studies included involved elite team-sport athletes, with HRV measured immediately after waking. Exclusion criteria were underage athletes, injured athletes, and studies using HRV for different purposes. The review process involved screening titles, abstracts, and full texts, with a final inclusion of 12 studies. Results: Out of 277 identified articles, 12 studies met the inclusion criteria, involving sports such as water polo, rugby, football, basketball, volleyball, handball, futsal, hockey, and rowing. The studies highlighted HRV as a valuable tool for tracking training load adaptations, monitoring athlete readiness, recovery, and mental stress. Daily HRV measurements were commonly used, showing effectiveness in detecting overtraining and ensuring adequate recovery. Various HRV parameters and recording methods were discussed, emphasizing the need for individualized assessment. RMSSD and LnRMSSD were the most commonly used parameters, with variations in recording times and positions. Conclusions: HRV is an effective non-invasive marker for optimizing training regimens and improving athlete health, making it a significant tool in sports medicine. This review provides actionable insights for integrating HRV monitoring into daily training practices, ultimately enhancing athletic performance and preventing overtraining. Standardized protocols for HRV measurement are recommended to ensure consistency and reliability in data collection and interpretation. The findings highlight the need for further research to refine HRV applications and establish best practices in elite team sports

Observational study of the effects of maximal oxygen uptake on cognitive function and performance during prolonged military exercise

IntroductionMilitary operations place high demands on many cognitive functions, and stressful events characterise the military work environment. The study aimed to examine the relationship between cardiorespiratory fitness, stress response, cognitive...

Intra- and Inter-Rater Reliability of Linear and Nonlinear Measures of Short-Term Heart Rate Variability Following Combat-Related Traumatic Injury.

Heart rate variability (HRV) is a marker of autonomic function. However, the reliability of short-term HRV measurement in individuals with combat-related traumatic injury (CRTI) remains undetermined. An intra- and inter-rater reliability study was conducted using a subsample (n = 35) of British servicemen with CRTI enrolled in the ongoing ADVANCE study. A five-minute epoch of single-lead electrocardiogram data collected during spontaneous breathing was used to measure HRV. HRV analyses were independently performed by two examiners using Kubios. Intraclass correlation coefficient (ICC), standard error of measurement (SEM), minimum detectable change (MDC), and coefficient of variance were calculated for linear [root mean square of successive difference (RMSSD), standard deviation of NN interval, low-frequency, high-frequency, total power] and nonlinear (SD1-2, acceleration and deceleration capacities, sample entropy) measures. Bland-Altman %plots were used to assess bias in intra- and inter-rater HRV data. The mean age of participants was 39.3 ± 6.3 years. An excellent ICC score of 0.9998 (95% CI 0.9997, 0.9999) was observed for intra-rater analyses of RMSSD, and similar excellent ICC scores were seen for all other HRV measures. The inter-rater reliability analyses produced an excellent ICC score (range 0.97-1.00). Comparatively, frequency-domain measures produced higher MDC% and SEM% scores than time-domain and nonlinear measures in both inter- and intra-rater analyses. The Bland-Altman plots revealed relatively higher bias for frequency-domain and nonlinear measures than time-domain measures. ECG-related short-term HRV measures were reliable in injured servicemen under spontaneous breathing. However, the reliability appeared better with the time-domain measure than frequency-domain and nonlinear measures in this sample.

The impact of controlled breathing on autonomic nervous system modulation: analysis using phase-rectified signal averaging, entropy and heart rate variability

Objective.The present study investigated how breathing stimuli affect both non-linear and linear metrics of the autonomic nervous system (ANS).Approach.The analysed dataset consisted of 70 young, healthy volunteers, in whom arterial blood pressure (ABP) was measured noninvasively during 5 min sessions of controlled breathing at three different frequencies: 6, 10 and 15 breaths min-1. CO2concentration and respiratory rate were continuously monitored throughout the controlled breathing sessions. The ANS was characterized using non-linear methods, including phase-rectified signal averaging (PRSA) for estimating heart acceleration and deceleration capacity (AC, DC), multiscale entropy, approximate entropy, sample entropy, and fuzzy entropy, as well as time and frequency-domain measures (low frequency, LF; high-frequency, HF; total power, TP) of heart rate variability (HRV).Main results.Higher breathing rates resulted in a significant decrease in end-tidal CO2concentration (p< 0.001), accompanied by increases in both ABP (p <0.001) and heart rate (HR,p <0.001). A strong, linear decline in AC and DC (p <0.001 for both) was observed with increasing breathing rate. All entropy metrics increased with breathing frequency (p <0.001). In the time-domain, HRV metrics significantly decreased with breathing frequency (p <0.01 for all). In the frequency-domain, HRV LF and HRV HF decreased (p= 0.038 andp= 0.040, respectively), although these changes were modest. There was no significant change in HRV TP with breathing frequencies.Significance.Alterations in CO2levels, a potent chemoreceptor trigger, and changes in HR most likely modulate ANS metrics. Non-linear PRSA and entropy appear to be more sensitive to breathing stimuli compared to frequency-dependent HRV metrics. Further research involving a larger cohort of healthy subjects is needed to validate our observations.

A Comparative Analysis of Heart Rate Variability Indices in Patients with Liver Cirrhosis.

Cardiac autonomic dysfunction (AD) in reference to chronic liver disease (CLD) has become widely accepted as a symptomatic burden. This study will be undertaken to measure heart rate variability (HRV) indices and detect the severity of cardiac autonomic dysfunction in CLD patients. This study was conducted on 150 patients with liver cirrhosis and compared with 110 healthy controls. Information concerning medical history, radiological and laboratory findings was extracted for interpretation and association among both groups. The HRV was assessed by recording with a polygraph (RMS Polyrite D, version 1.0), which was based on the principle of electrocardiography. Heart rate variability indices like standard deviation of each interval normal-to-normal (SDNN), percentage of successive RR intervals that differ by >50 ms (pNN50%), high frequency (HF), low frequency (LF), and the LF/HF ratio were found to be remarkably low in cases with CLD in comparison to the healthy control group (p < 0.05). The Child-Pugh (CP) score was class C (10-15) in 52%, class B (7-9) in 30%, and class A (5-6) in 18% of patients. The CP score in CLD patients had a statistically significant negative correlation with SDNN (r = -0.5429, p < 0.001), root mean square of successive differences (RMSSD) (r = -0.375, p < 0.001), pNN50% (r = -0.6037, p < 0.001), HF (r = -0.2033, p = 0.0125), and LF (r = -0.3674, p < 0.001). SDNN, pNN50%, and LF parameters were lowest in alcohol-related CLD, highest in hepatitis C virus (HCV)-related CLD, and intermediate in hepatitis B virus (HBV)-related CLD. Our study concluded that liver cirrhosis patients have reduced HRV compared to healthy individuals. A decrease in HRV highlights people at risk of death. This is a variable that can be used to track patients over time and aid in transplant selection.

Abnormal brain-heart electrophysiology in mild and severe orthostatic hypotension.

This study investigated the changes in cardiocerebral electrophysiology in patients with mild orthostatic hypotension (MOH) and severe orthostatic hypotension (SOH) and their relationship with the severity of orthostatic hypotension, psychiatric symptoms, and cognitive dysfunction. This study included 72 nonorthostatic hypotension (NOH), 17 with MOH, and 11 with SOH. Seated resting-state heart rate variability (HRV) and quantitative electroencephalogram parameters were synchronized and recorded. HRV measures in the time and frequency domains were analyzed, along with the peak frequency and power of the brain waves. Abnormal neuronal activity was found in FP1 in patients with MOH, whereas it was more widespread in FP1, FP2, and O2 in patients with SOH (P < 0.05). Cardiac and cerebral electrophysiological abnormalities were significantly associated with orthostatic hypotension severity, psychiatric symptoms, and cognitive dysfunction. Abnormal EEG activity in patients are mainly manifested in the prefrontal and occipital lobes, especially in patients with SOH. These results may help patients to better understand the mechanisms underlying orthostatic hypotension severity and psychiatric and cognitive impairment in orthostatic hypotension.