Time Of Heart Rate Variability Research Articles

Uncovering sympathetic nervous system dysfunction in disorders of consciousness via heart rate variability during head-up tilt test.

Few standardized tools are available for evaluation of disorders of consciousness (DOC). The potential of heart rate variability (HRV) during head-up tilt (HUT) test was investigated as a complementary evaluation tool. Twenty-one DOC patients and 21 healthy participants were enrolled in this study comparing clinical characteristics and HRV time- and frequency-domain outcomes and temporal changes during HUT test. During the 1st-5th min of the HUT, DOC group showed a significant increase and decrease in log low frequency (LF) (p = 0.045) and log normalized high frequency (nHF) (p = 0.02), respectively, compared to the supine position and had lower log normalized LF (nLF) (p = 0.004) and log ratio of low-to-high frequency (LF/HF) (p = 0.001) compared to healthy controls. As the HUT continued from the 6th to the 20th min, DOC group exhibited a significant increase in log LF/HF (16th-20th min) (p < 0.05), along with a decrease in log nHF (6th-10th and 16th-20th min) (p < 0.05) and maintained lower log LF, log nLF, and log LF/HF than controls (p < 0.05). 1st-10th min after returning to the supine position, DOC group demonstrated a significant decrease in log nHF (p < 0.01) and increases in log LF/HF (p < 0.01) and had lower log LF (p < 0.01) and log nLF (p < 0.05) compared to controls. In contrast, the control group exhibited a significant decrease in log nHF (p < 0.05) and increase in log LF/HF (p < 0.05) throughout the entire HUT test. Notably, no significant differences were observed when comparing time-domain outcomes reflecting parasympathetic nervous system between the two groups. HRV during HUT test indicated a delayed and attenuated autonomic response, particularly in the sympathetic nervous system, in DOC patients compared with healthy individuals.

Analysis of the factors of heart rate variability affected after a hypoxia tolerance test as a function of gender

Heart rate variability (HRV), the variation of time intervals between heartbeats, reflects the result of the interaction between the autonomic nervous system and the cardiovascular system. Hypoxia is a stressor that causes changes in HRV and a decrease in arterial oxygen saturation (SaO2). The aim of our study is to analyse if the time and frequency domains of HRV are affected after a hypoxia tolerance test in healthy participants as a function of gender. Material and methods: 23 healthy volunteers (11 women and 12 men) with a mean age of 23.08±2.99 performed a hypoxia tolerance test (11%, 5050 m) with the iAltitude simulator. Heart rate and SaO2 were monitored during the test and HRV frequency domain (FD) and time domain (TD) data were obtained. We analysed the five minutes before and after each session. Outcomes: Simulated altitude-induced hypoxia can cause changes in HRV in a group of healthy individuals. Statistically significant differences were also found between before and after the normobaric hypoxia test in the time-domain variables RRm, SDNN, HRm, HR STD, pNN50. In addition, in women statistically significant differences were found in RMSSD, and in the frequency-domain variables HF and LF/HF. While in males, statistically significant differences were found in SDNN. In both men and women, significant differences were observed in RRm, HRm and pNN50. Conclusion: The differences found in HRV after the hypoxia tolerance test indicate that females show a greater activation of the parasympathetic nervous system compared to males. While males showed greater sympathetic activation. Keywords: Heart rate variability, normobaric hypoxia, stress, autonomic nervous system.

Changes in heart rate variability over time from symptom onset of transient global amnesia

Transient global amnesia (TGA) often involves precipitating events associated with changes in autonomic nervous system (ANS), and heart rate variability (HRV) reflects the ANS state. This study aimed to investigate HRV changes after TGA. A retrospective analysis of HRV included patients diagnosed with TGA between January 2015 and May 2020. The time and frequency domains of HRV were compared among three groups: early (< 1 week after TGA, n = 19), late (1–4 weeks after TGA, n = 38), and healthy control (HC, n = 19). The Pearson’s correlation between time and time-domain HRV was also examined. The standard deviation of NN intervals (SDNN) (early, 47.2; late, 35.5; HC, 41.5; p = 0.033) and root mean square of successive RR interval differences (RMSSD) (early, 38.5; late, 21.3; HC, 31.0; p = 0.006) differed significantly among the three groups. Post-hoc analysis showed statistically significant differences only in the early and late groups in both SDNN (p = 0.032) and RMSSD (p = 0.006) values. However, the frequency domain with total power, low-frequency and high-frequency powers, and low-frequency/high-frequency ratio did not differ. SDNN (Pearson correlation coefficient =− 0.396, p = 0.002) and RMSSD (Pearson correlation coefficient =− 0.406, p = 0.002) were negatively correlated with time after TGA. Changes in HRV occurred over time after the onset of TGA, with the pattern showing an increase in the first week and then a decrease within 4 weeks.

Evaluation of Fatigue in Older Drivers Using a Multimodal Medical Sensor and Driving Simulator

In recent years, the spread of wearable medical sensors has made it possible to easily measure biological signals such as pulse rate and body acceleration (BA), and from these biological signals, it is possible to evaluate the degree of biological stress and autonomic nervous activity in daily life. Accumulated fatigue due to all-day work and lack of sleep is thought to be a contributing factor to distracted driving, and technology to estimate fatigue from biological signals during driving is desired. In this study, we investigated fatigue evaluation during a driving simulator (DS) using biological information on seven older subjects. A DS experiment was performed in the morning and afternoon, and no significant differences were observed in the change over time of heart rate variability and skin temperature. On the other hand, in the afternoon DS, changes in arousal and body movements were observed based on BA calculated from the three-axis acceleration sensor and fingertip reaction time in a psychomotor vigilance test. It is suggested that by combining biological information, it may be possible to evaluate the degree of fatigue from the presence or absence of arousal and changes in body movements while driving.

Do Longer Exhalations Increase HRV During Slow-Paced Breathing?

Slow-paced breathing at an individual's resonance frequency (RF) is a common element of heart rate variability (HRV) biofeedback training (Laborde et al. in Psychophysiology 59:e13952, 2022). Although there is strong empirical support for teaching clients to slow their respiration rate (RR) to the adult RF range between 4.5 and 6.5bpm (Lehrer & Gevirtz, 2014), there have been no definitive findings regarding the best inhalation-to-exhalation (IE) ratio to increase HRV when breathing within this range. Three methodological challenges have frustrated previous studies: ensuring participants breathed at the target RR, IE ratio, and the same RR during each IE ratio. The reviewed studies disagreed regarding the effect of IE ratios. Three studies found no IE ratio effect (Cappo & Holmes in J Psychosom Res 28:265-273, 1984; Edmonds et al. in Biofeedback 37:141-146, 2009; Klintworth et al. in Physiol Meas 33:1717-1731, 2012). One reported an advantage for equal inhalations and exhalations (Lin et al. in Int J Psychophysiol 91:206?211, 2014). Four studies observed an advantage for longer exhalations than inhalations (Bae et al. in Psychophysiology 58:e13905, 2021; Laborde et al. in Sustainability 13:7775, 2021; Strauss-Blasche et al. in Clin Exp Pharmacol Physiol 27:601?60, 2000; Van Diest et al. in Appl Psychophysiol Biofeedback 39:171?180, 2014). One study reported an advantage for longer inhalations than exhalations (Paprika et al. in Acta Physiol Hung 101:273?281, 2014). We conducted original (N = 26) and replication (N = 16) studies to determine whether a 1:2 IE ratio produces different HRV time-domain, frequency-domain, or nonlinear metrics than a 1:1 ratio when breathing at 6bpm. Our original study found that IE ratio did not affect HRV time- and frequency-domain metrics. The replication study confirmed these results and found no effect on HRV nonlinear measurements.

Cardiac remodeling in patients with heart failure with mildly reduced ejection fraction and metabolic disorders: association with biomarkers and autonomic nervous system parameters

Aim. The high prevalence of obesity in a cohort of patients with heart failure and mildly reduced ejection fraction (HFmrEF) determines the relevance of clarifying the role of biomarkers and autonomic imbalance in myocardial remodeling, taking into account metabolic risk factors.Material and methods. We examined 19 men with postinfarction cardiosclerosis and class II HFmrEF (median age 62 years), overweight/class I-II obesity, type 2 diabetes in 53/47%, 48% of cases, respectively, who received therapy. The biomarker panel included N-terminal pro-brain natriuretic peptide (NT-proBNP), galectin-3, pro-collagen I C-terminal propeptide (PICP), N-terminal propeptide of procollagen type III (PIIINP), C-terminal telopeptide of type I collagen, matrix metalloproteinase-9 (MMP-9), tissue inhibitor of matrix proteinase-1 (TIMP-1), leptin and adiponectin. Heart rate variability (HRV) and turbulence were obtained using 24-hour Holter monitoring. We assessed the time and frequency domains of HRV (24 h) and 5 min recordings of wakefulness at rest, calculated TO (turbulence onset) and TS (turbulence slope).Results. Significant positive associations of leptin and TIMP-1 levels with left ventricular hypertrophy markers were confirmed. Positive correlations of peak e' with following HRV indicators were revealed: SDNN (r=0,68; p=0,02) and RMSSD (r=0,69; p=0,003). Lower TS values were associated with higher index parameters of left ventricular mass (p&lt;0,05 for all). Associations of biomarkers with autonomic nervous system (ANS) were observed: MMP-9 with RMSSD (r=0,54) and pNN50 (r=0,51); TIMP-1 with TO (r=0,46); PICP/PIIINP ratio with HFn (5 min) (r=-0,49); NT-proBNP/adiponectin ratio with SDNN (r=-0,49); leptin level with TS (r=-0,54) (p&lt;0,05 for all).Conclusion. In patients with HFmrEF of ischemic origin and additional metabolic risks, serum biomarkers of fibrosis, adipokines, and ANS parameters are associated mainly with markers of increased left ventricular filling pressure. The study results predetermine the further search for potential risk-stratification markers of unfavorable myocardial remodeling and prognosis in large samples of patients with metabolic deviations and HF with EF &gt;40% against the background of modern drug therapy.

Features extraction from cardiac-related signals: comparison among different measurement methods

Heart Rate (HR), Heart Rate Variability (HRV), and cardiac time intervals are clinically relevant parameters, which can be assessed from the analysis of electrocardiogram (ECG). Some aspects of cardiac activity can be investigated also by means of different noninvasive and non-intrusive measurement methods, such as phonocardiograph (PCG), photoplethysmograph (PPG), and vibrocardiograph (VCG). However, the standard processing algorithms (i.e., Pan & Tompkins) do not allow to fully characterize waveforms different from ECG. In the past, some of the authors have already demonstrated the efficiency of a novel processing procedure for the precise HR measurement from the above-mentioned signals. In the present work, data processing procedure has been improved and deeply extended to assess HRV parameters and time intervals from all the signals acquired on an extended experimental campaign, involving 26 subjects, on whom ECG, PPG, PCG, and VCG signals were simultaneously measured. Results prove that this approach can overcome the drawbacks of standard algorithms and can be widely applied to signals of different nature to derive HR, HRV, and time intervals. As regards HR measurement, PPG proved to be the most accurate measurement method (±1.2 bpm), followed by VCG (±1.6 bpm) and PCG (±2.5 bpm). For HRV analysis in the time domain, the use of the proposed methodology allows to obtain clinically relevant parameters statistically comparable to the ECG ones. Finally, the measurement of QT interval by applying personal calibration lines allows to obtain results comparable to the gold standard technique, i.e., ECG (maximum percentage deviation reduced from 10.9% up to <4.3% in VCG).

Mood Disorder Severity and Subtype Classification Using Multimodal Deep Neural Network Models.

The subtype diagnosis and severity classification of mood disorder have been made through the judgment of verified assistance tools and psychiatrists. Recently, however, many studies have been conducted using biomarker data collected from subjects to assist in diagnosis, and most studies use heart rate variability (HRV) data collected to understand the balance of the autonomic nervous system on statistical analysis methods to perform classification through statistical analysis. In this research, three mood disorder severity or subtype classification algorithms are presented through multimodal analysis of data on the collected heart-related data variables and hidden features from the variables of time and frequency domain of HRV. Comparing the classification performance of the statistical analysis widely used in existing major depressive disorder (MDD), anxiety disorder (AD), and bipolar disorder (BD) classification studies and the multimodality deep neural network analysis newly proposed in this study, it was confirmed that the severity or subtype classification accuracy performance of each disease improved by 0.118, 0.231, and 0.125 on average. Through the study, it was confirmed that deep learning analysis of biomarker data such as HRV can be applied as a primary identification and diagnosis aid for mental diseases, and that it can help to objectively diagnose psychiatrists in that it can confirm not only the diagnosed disease but also the current mood status.

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.

Comparison of the effects of moxibustion and acupuncture of combined "Biao-Ben" acupoints on intestinal sensitivity and autonomic nervous system function in rats with diarrhea-predominant irritable bowel syndrome.

To compare the effects of moxibustion and acupuncture of combined "Biao-Ben" acupoints (Biao indicates pathogenic factors of disease, Ben refers to body constitution) on a rat model of irritable bowel syndrome with diarrhea (IBS-D). Forty female SD rats were randomly divided into 4 groups：normal group, model group, moxibustion group, and acupuncture group, with 10 rats in each group. The IBS-D rat model was established by administering acute-chronic stress combined with folium sennae gavage for 28 days. Rats in the moxibustion group received moxibustion at bilateral "Zusanli"(ST36), "Guanyuan"(CV4), and "Neiguan"(PC6), while those in the acupuncture group received acupuncture at the same acupoints, both for 15 min every time, once a day. The treatments were administered for 21 days. The loose stool rate was observed. Colonic pain threshold and colonic distension threshold were measured by a self-made balloon catheter. Total distance traveled and grid crossing numbers were observed by open field test. Heart rate variability(HRV) time domain indexes SDANN and PNN50 were acguired by using electrophysiological recorder. Histopathological changes in the colon tissue were observed after HE staining. Contents of interleukin-6(IL-6), IL-8, and tumor necrosis factor-alpha(TNF-α) in serum were detected by ELISA. Compared with the normal group, rats in the model group showed increased loose stool rate(P<0.05), decreased pain threshold and distension threshold(P<0.05), reduced total distance traveled and grid crossing numbers in the open field test(P<0.05), decreased HRV time domain indexes SDANN and PNN50(P<0.01, P<0.05), and elevated levels of serum IL-6, IL-8, and TNF-α contents(P<0.05). Compared with the model group, the moxibustion group and acupuncture group showed decreased loose stool rate(P<0.05), increased total distance traveled and grid crossing numbers in the open field test(P<0.05), increased pain threshold and distension threshold(P<0.05), increased SDANN and PNN50 (P<0.05), and decreased levels of serum IL-6, IL-8, and TNF-α contents(P<0.05). Compared with the acupuncture group, the moxibustion group showed further decreased loose stool rate(P<0.05), increased total distance traveled and grid crossing numbers in the open field test(P<0.05), increased pain threshold and distension threshold(P<0.05), increased SDANN and PNN50(P<0.05), and decreased levels of serum IL-6, IL-8, and TNF-α contents(P<0.05). No significant pathological changes were observed in the colon tissue of rats in each group. Moxibustion of combined "Biao-Ben" acupoints is more effective in regulating HRV and serum IL-6, IL-8, and TNF-α contents in the IBS-D rat model. Based on the combined "Biao-Ben" acupoints method, moxibustion has better therapeutic effects on IBS-D than acupuncture.

Introducing outdoor office work to reduce stress among office workers in Sweden

Abstract Background Office workplace stress is concerning as it leads to adverse and chronic health outcomes. Outdoor office work (OOW), an innovative practice may address these challenges as being outdoors has potential benefits. This study aims to assess stress among office workers that are working in their normal indoor office compared to practicing OOW and identifying facilitators and barriers for doing OOW. Methods In a feasibility study, 9 office workers were asked to work indoors the 1st week and OOW for at least 30 minutes per day during the 2nd week. They wore a heart rate variability (HRV) monitor (FirstBeat BG3) for 2 weeks while at work to assess objective stress. Subjective stress was assessed via daily surveys using a scale of 1 to 10 from “not stressed at all” to “very stressed”. They were instructed to use the app “Our Voice Discovery Tool” to take photos of facilitators or barriers to practicing OOW. Subjective stress data was analysed using paired sample t-test in SPSS 28. Photos were categorised into themes. Analysis of HRV time and frequency parameters is underway. Results Preliminary findings show statistically significant decrease in stress scores between week 1 (M = 4.42, SD = 1.43) and week 2 (M = 3.74, SD = 1.31) t(7)=1.91, p=.049 (one-tailed), mean decrease in self-rated stress was .68 with a 95% confidence interval ranging from -.12 to 1.43. The Cohen's d (.67) indicated a medium effect size. Picture analysis revealed themes related to “convenience/comfort”, equipment/facilities”, and “weather” as barriers. Out of 76 pictures, most themed “nature”, both indoor and outdoor, were marked as positive experiences. Conclusions Reduction in subjective stress from week 1 to week 2 suggests OOW's potential as useful method to reduce work-related stress. Picture analysis suggests, to ensure a healthier milieu for office workers, conditions conducive to OOW such as outdoor work facilities and green spaces in offices’ vicinity may need to be facilitated by employers. Key messages • Outdoor office work (OOW) may reduce workplace stress, potentially improving employee health, well-being, and productivity. • Employers should facilitate outdoor workspaces and green areas to promote healthier office environments.

Revisiting nonlinearity of heart rate variability in healthy aging

Aging is commonly regarded as a physiological process in which the dynamic complexity of physiological time series and organ systems is gradually lost. This notion is derived from the identification of a decline of nonlinear measures with the advance of aging. However, additional research on cardiovascular control studied through heart rate variability (HRV), i.e., the instantaneous changes in heart rate, shows that despite the constriction of its statistical distribution, the nonlinear organization remains present in advanced age. Here, we used surrogate data testing to investigate the presence of nonlinear information in HRV time series from a publicly available database of 1121 healthy human subjects from 18 to 92 years old. We also studied the influence of basic clinical features, such as sex, body mass index (BMI), and mean heart rate (HR), on such nonlinear information. We found that the percentage of nonlinear time series after 30 years of age diminishes significantly (p < 0.01). Furthermore, larger BMI and HR are associated with the presence of more linear information in HRV, while the female sex is associated with the manifestation of nonlinear information. This work provides a common background for the contextualized interpretation of nonlinear testing and shows that the nonlinear content of HRV time series diminishes through aging.

IC87201, a PSD-95/nNOS Inhibitor, Ameliorates Heart Rate Variability in the Rat Model of Middle Cerebral Artery Occlusion

Objective: Assessment of heart rate variability (HRV) is a non-invasive and reliable method to evaluate autonomic disorders after cerebral ischemia. The present study was conducted to investigate the therapeutic potential of IC87201 in reducing post-stroke cardiac dysfunction. Materials and methods: Cerebral ischemia was induced by the middle cerebral artery occlusion (MCAO) method in 15 anesthetized adult male rats in three MCAO, MCAO+ DXM, and MCAO+ IC87201 groups, for one hour. Electrocardiogram was recorded before, and 48 hours after ischemia and drug administration, and HRV parameters were calculated from R-R intervals. In the treatment groups, IC87201 and Dextromethorphan hydrobromide monohydrate (DXM) were injected after an ischemic period. Results: After brain ischemia, the R-R interval decreased and consequently heart rate increased. The R-R intervals were used to extract the HRV frequency and time domains, including normalized low frequency (LF), high frequency (HF), LF/HF ratio, and standard deviation of R-R interval (SDRR). Normalized LF and LF/HF ratio enhanced 48 hours after ischemia, while normalized HF and SDRR significantly reduced compared to the pre-ischemic state. All HRV parameters had returned to their pre-ischemic level 48 hours after IC87201 and DXM administration, except SDRR, which recovered only in the IC87201 administered group. Conclusion: Based on our findings, it can be concluded that cerebral ischemia significantly worsens HRV parameters as a result of sympathetic overactivity. These changes were reversed by administering DXM and IC87201, but IC87201 has generally been more effective in lowering lesions. As a result, IC87201 can be introduced as an effective substance for the treatment of post-ischemic cardiac side effects.

Fast Pace Sun Salutations (FPSS) Yoga Postures Influence Brain waves Activity in Addition to Heart Rate Variability Pattern: A Pilot Study

ABSTRACT Background: Sun salutation (Surya namaskar) is an ancient yogic exercise, which is a combination of 12 different postures rhythmically. Yoga practitioners perform this procedure in a slow as well as fast pace manner. Aim: We undertook this study to find out the immediate changes in heart rate variability (HRV) and brain waves spectrum after the practice of fast pace sun salutation (FPSS). Settings and Design: This prospective interventional observational study was conducted on 30 male healthy subjects in the 30–45 years age group from September 2021 to December 2021 after approval from the Institutional Ethics Committee. Participants gave their written consent in the prescribed format. Materials and Methods: Fourteen rounds of FPSS were performed in approximately 10 min under the guidance of a yoga expert. Brain Tap Dinamika Machine (Advanced HRV Test System, Moscow, Russia) was used to assess different HRV and brain waves parameters before and after FPSS. Statistical Analysis Used: Statistical analysis was done by Student’s paired t-test using GraphPad online software. Results: All independent variables of time and frequency domain analysis of HRV were found to be increased after the intervention. A significant upsurge in low frequency (LF)% as compared to high frequency (HF)% and very low frequency (VLF)% showed a relative increase in sympathetic activity. In brain waves, delta, theta, and alpha were decreased, whereas activities of beta and gamma waves were found to be increased. Conclusions: Increase in both LF and HF components showed that both sympathetic and parasympathetic components have increased. Brain wave analysis suggested increased mental alertness after FPSS.

Nonlinear Dynamics of Heart Rate Variability after Acutely Induced Myocardial Ischemia by Percutaneous Transluminal Coronary Angioplasty.

Several heart rate variability (HRV) characteristics of patients with myocardial ischemia are associated with a higher mortality risk. However, the immediate effect of acute ischemia on the HRV nonlinear dynamical behavior is unknown. The objective of this work is to explore the presence of nonlinearity through surrogate data testing and describe the dynamical behavior of HRV in acutely induced ischemia by percutaneous transluminal coronary angioplasty (PTCA) with linear and recurrence quantification analysis (RQA). Short-term electrocardiographic recordings from 68 patients before and after being treated with elective PTCA were selected from a publicly available database. The presence of nonlinear behavior was confirmed by determinism and laminarity in a relevant proportion of HRV time series, in up to 29.4% during baseline conditions and 30.9% after PTCA without statistical difference between these scenarios. After PTCA, the mean value and standard deviation of HRV time series decreased, while determinism and laminarity values increased. Here, the diminishment in overall variability caused by PTCA is not accompanied by a change in nonlinearity detection. Therefore, the presence of nonlinear behavior in HRV time series is not necessarily in agreement with the change of traditional and RQA measures.

The Role of Morphology and Heart Rate Variability Features in Detecting Arrhythmias from Short ECGs

Detecting heart arrhythmias from short Electrocardiogram (ECG) recordings remains challenging since recordings are short and contaminated by noise. ECG morphology features and Heart Rate Variability (HRV) time and frequency domain features are widely used for classifying short ECG recordings. Here we investigate the relative roles of ECG morphology features and HRV time and frequency domain features in classifying short ECG recordings provided by the 2017 PhysioNet/Computing in Cardiology Challenge. The classification is performed separately by four machine learning models: Logistic Regression, Decision Tree, K Nearest Neighbors, and Convolutional Neural Network (CNN). Our best classification score is obtained using the deep learning 1-dimensional CNN model trained on HRV time domain features combined with ECG morphology features. It gives an overall F1 score of 0.70 and 0.73 for the cross validation and hidden test respectively when considering the average classification performance over all 4 categories: Atrial Fibrillation (AF), normal, other arrhythmias, and noisy signal. We found that HRV time domain features play an important role in detecting AF, normal, and other classes, whereas ECG morphology features play a key role in detecting the noisy class. When HRV frequency domain features are combined with HRV time domain features, they do not improve and often degrade classifications of short ECG recordings compared to classifications using only HRV time domain features. Combining ECG morphology features with HRV time domain features leads to a better classification performance for short ECG recordings. Feature-based deep learning could serve as a viable and less expensive approach for ECG classifications.

Fluid Replacement Strategies and Heart Rate Variability Recovery Following Prolonged Exercise in the Heat and Mild Dehydration

Background: In sporting and combat settings, optimal fluid replacement is rarely achieved, exacerbating physiological strain. It is unknown if prescribed fluid replacement following exercise in heat impacts heart rate variability (HRV). Purpose: Compare prescribed drinking (PD) and ad libitum (AL) fluid replacement on HRV following exercise in heat. Methods: Twelve participants (26 ± 5 years, VO2max: 58.44 ± 7.05 mL·kg−1·min−1) completed three trials in heat (36 °C, 36% humidity) on separate days, and were placed into groups, PD or AL. Recovery was assessed ~24 h later (hydration and HRV). HRV time and frequency was measured using a 3-lead electrocardiogram. Two-way repeated measures analysis of variance measured changes in HRV pre-trial, post-trial, and follow-up between groups. Data reported: p-value, mean difference (MD). Results: Fluid consumption was greater in PD during recovery (p = 0.012, MD = 1245 mL). Both groups were euhydrated at follow-up. HRV time (p &lt; 0.001, MD = 24.23) and frequency (p &lt; 0.001, MD = −1.98 ms2) decreased post-trial and increased by follow-up (time, p &lt; 0.001, MD = −32.12; frequency, p &lt; 0.001, MD = 2.38 ms2). HRV was similar between groups (p &gt; 0.05). Conclusions: Replacing ≥60% fluid sufficiently rehydrates and restores HRV 24 h post-exercise in heat and mild dehydration (BML ≤ 3%). Prescribed fluid consumption during recovery was ~30% greater. Additional measures of recovery sensitive to heat strain may provide a more holistic understanding of specific mechanisms of recovery.

The Effectiveness of Utilizing HRV Indices as a Predictor of ACFT Performance Outcomes.

The Army Combat Fitness Test (ACFT) is a performance assessment used by the U.S. Army to assess a cadet's strength, endurance, and agility with a series of six events to ensure that cadets are combat ready. Heart rate variability (HRV) is an instrument that measures cardiac autonomic modulation and has been incorporated to predict the performance of athletes in daily training and competition since acute bouts of exercise alter HRV variables. To assess the applicability of using HRV to predict ACFT score performance outcomes in cadets. Fifty army cadets (n = 36 male; n = 14 female; age = 20.60 ± 3.61 years; height = 173.34 ± 10.39 cm; body mass = 76.33 ± 14.68 kg; body fat percentage = 17.58 ± 5.26%) completed the ACFT and reported for HRV assessment. HRV assessment had the participant lay supine for 5 minutes, and traditional time and frequency domain variables were assessed. A Pearson's correlation and multiple linear regressions were run. HRV time and frequency domains were not significantly correlated in linear regression models except the stress index (SI) and the 2-mile run (2MR). The standing power throw and sprint drag carry were significantly correlated with traditional HRV variables. HRV was not a predictor of ACFT performance for individual events or overall ACFT. The SI presented predictive properties only for 2MR, with no other significant correlations between HRV variables with standing power throw and sprint drag carry. The SI ability to predict 2MR performance outcome via HRV is a promising tool to assess army cadet performance and recovery.

A Study to Correlate Stress Score with Heart Rate Variability among MBBS Students at a Tertiary Care Center, Jaipur

Introduction: Medical students have high levels of stress that could be due to stressors related to the academic workload, time pressure competency, professionalism, physical, mental, and emotional issues. This study aimed to find out subjective assessment of stress, stressors, and coping strategies and objective assessment of stress with heart rate variability (HRV) and correlate subjective and objective assessment of stress scores among 1st year MBBS students at RUHS College of Medical Sciences. Materials and Methods: Institutional ethical clearance (EC-P-21/RUHS) was obtained after that study was conducted among a total of 150 1st year MBBS students. The students were asked to fill out a validated general health questionnaire (GHQ-12), “medical student stress questionnaire 40,” and a brief COPE inventory to assess stress, stressors, and various coping strategies for subjective assessment and objective assessment done by time and frequency domain parameters of HRV. Results: The mean age was 20.85 ± 1.56. The severity of stress categorized as mild, moderate, high, and severe were 17%, 40%, 13%, and 10%, respectively. The most affected stressor was academic contributed to 80% followed by teaching–learning related, social, intra- and interpersonal, group activities, drive, and desire-related stressors 78%, 75%, 73%, 70%, and 68%, respectively. Overall, the students’ coping strategies were mostly avoidant followed by emotional and problem based. HRV is measured by time domain, i.e., PNN50, standard deviation of normal to normal RR intervals, root mean square of successive differences, and “frequency domain parameters,” i.e., low frequency (LF), high-frequency (HF), and LF/HF ratio. Conclusion: In the present study, a positive correlation was observed between HRV and stress score. More than 75% of RUHSCMS 1st year medical students were suffering from measurable academic stress. Time domain and frequency domain parameters were positively correlated with stress score.

A Study to Assess Changes in Cortisol Level and Heart Rate Variability between Fixed Duty and Shift Duty Health Care Providers in a Tertiary Care HospitalA Cross-Sectional Study

Introduction: Increased demand of service 24 hours around the clock has divided the workers into 2 domains as “Fixed duty” and “Shift duty”. Personals associated with shift duty are increasing in numbers day by day. Shift duty or more specifically night duty is associated with increased stress which results in high morbidity and decrease in work efficiency. Cortisol hormone and Heart Rate Variability (HRV) are useful parameters to determine the effects of stress. Aim: To find any change in cortisol levels, HRV, Athens score among the fixed duty and shift duty healthcare providers. Materials and Methods: A descriptive cross-sectional comparative study was conducted in a tertiary care hospital at Kolkata between July, 15th to Sept, 15th 2021. Predesigned and pretested questionnaire was made and ethical clearance was taken from institutional IEC. Then after taking consent total 120 (60 fixed duty and 60 shift duty) healthcare providers were recruited for the study. Subjects of the study filled up a questionnaire {including Athens Insomnia Scale (AIS)}. After applying exclusion criteria (any cardiovascular, neurological, psychological, sleep disorder) 120 health individuals were taken five minutes short-term HRV (time and frequency domain) recording in supine posture and 4 PM blood sample (for cortisol) were obtained from the participants which was further analysed in Chemiluminescence Immunoassay (CLI). Data was analysed in SPSS version 20.0. Statistical tests like student t-test, Cron bach’s alpha and chi-square tests were applied significant p&lt;0.05 (95% CI). Results: After analysis, shift duty workers showed a significant (p&lt;0.001, Odd’s 10.706) higher chance of having insomnia (Athens score &gt;6) than fixed duty workers. Blood test showed that shift duty workers had significantly high evening cortisol level than fixed duty workers (p= 0.036). The time domain of HRV showed that the parameters like Standard Deviation all NN interval (SDNN) (p=0.001), Mean HR (p=0.037), RMSSD (p &lt;0.001), NN50 (p=0.006), pNN50 (p=0.002) were significantly different in the two groups. Whereas the frequency domain of HRV showed that HF power was lower and LF power (p=0.002), LF/HF ratio (p &lt;0.001) were significantly higher in shift duty workers. Conclusion: The study showed that shift duty workers had comparatively higher stress levels resulting in significantly high sympathetic drive and increased risk of insomnia. This can be associated with morbidity and ill health in the shifting duty workers.