Term Heart Rate Variability Research Articles

Does dysautonomia contribute to inappropriate sinus tachycardia in patients with post-COVID-19 syndrome?

Abstract Funding Acknowledgements None. Introduction Post-COVID-19 syndrome (PCS) refers to a wide spectrum of health issues experienced by individuals who have previously had COVID-19, starting three months after acute COVID-19 and enduring for a minimum of two months. Approximately 20% of PCS patients encounter inappropriate sinus tachycardia (IST), defined as the mean 24-hour heart rate greater than 90 bpm. IST is often accompanied by symptoms including palpitations and breathlessness that hinder patients in their daily tasks. Previous research has suggested that dysautonomia, a dysfunction in the autonomic nervous system, might underlie most PCS symptoms. Yet, its role in the development of IST within the context of PCS has not been fully investigated. Purpose This retrospective study examines IST prevalence and cardiovascular symptoms in PCS patients. It also assesses cardiac autonomic function through analysing the time and frequency fluctuations between successive heart rates, termed heart rate variability, to investigate the role of dysautonomia in the development of IST in PCS. Methods Patients who continued to experience PCS symptoms 12 weeks after their initial SARS-CoV-2 infection were referred to a multidisciplinary PCS unit at our hospital. Using our electronic patient record system, we identified 685 eligible patients who underwent 24-hour Holter monitoring between March 2020 and February 2023. After excluding patients with various conditions that could affect heart rate, we performed a comparative sub-analysis on 524 patients, dividing them into two age- and gender-matched groups of IST (n=100) and non-IST (n=424). The ECG data extracted from the 24-hour Holter records of these patients were entered into the KUBIOS software for HRV analysis and assessment of sympathetic and parasympathetic activity which could indicate cardiac dysautonomia. Demographic data was analysed using basic descriptive statistics and a chi-square test between the two groups. The normality of each parameter was tested using the Shapiro-Wilk test. Using Mann-Whitney and unpaired t-tests, we statistically analysed the differences between the IST and non-IST groups on the GraphPad Prism software. Results The LF/HF ratio was significantly higher in the IST group (2.78 ± 1.89) compared to the non-IST group (2.15 ± 1.93, p<0.001). The sympathetic nervous system (SNS) index was significantly higher in the IST group (1.50 ± 0.77 versus -0.13 ±0.70, p<0.001), whilst the parasympathetic nervous system (PNS) index was significantly lower in the IST group (-1.75 ± 0.65 versus -0.16 ± 1.61, p<0.001). Conclusions In PCS patients with IST, cardiac dysautonomia leads to a shift in the cardiac sympathovagal balance towards PNS and subsequently increased SNS activity, with a more pronounced effect on the parasympathetic side. Addressing dysautonomia and promoting parasympathetic activity could thereby improve PCS diagnostic and treatment strategies to restore a balanced autonomic regulation of the heart.

Assessment of ultra-short term heart rate variability indices in Obstructive Sleep Apnea

Assessment of ultra-short term heart rate variability indices in Obstructive Sleep Apnea

Heart Rate Variability-Based Prediction of Autonomic Dysreflexia After Spinal Cord Injury.

Autonomic dysreflexia (AD) is a common autonomic complication of spinal cord injury (SCI) characterized by a sudden increase is blood pressure triggered by peripheral stimulation, such as bladder distention. Iatrogenic AD events often occur during various medical procedures including urodynamic assessments (UDSs) used to evaluate lower urinary tract (LUT) function in individuals with SCI. To date, there are no established clinical practices that would allow early detection of the development of episodes of AD. Heart rate variability (HRV) is a reliable and non-invasive metric for evaluating autonomic regulation of the cardiovascular system, with demonstrated utility in people with SCI during UDSs. We aim to provide a comprehensive evaluation of cardiovascular function during UDS-induced AD using ultra-short-term HRV analysis and identify changes in cardiovascular dynamics to predict the onset of AD. We assessed cardiovascular data in a total of 24 participants with sensorimotor complete SCI above T6 (17 males, 7 females, median age = 43 [36-50] years) who experienced AD during UDS. We used continuous electrocardiographic recordings to evaluate HRV in 60 sec overlapping windows during filling cystometry. The mean of "normal-to-normal" heartbeats (meanNN), its standard deviation (SDNN), and the root mean square of successive differences (RMSSD) were calculated and used in all subsequent analyses. We found that SDNN and RMSSD diminished during the early phase of bladder filling and sharply increased during AD. Using the lowest point of statistical variability in heart rate (i.e., SDNN), we were able to predict AD events within 240 sec (percentile 25-percentile 75: 172-339 sec) before the first systolic blood pressure peak after AD onset (sensitivity = 0.667; specificity = 0.875). Our results indicated a temporary increase in sympathetic activity during the early phase of bladder filling, which is followed by an increase in parasympathetic outflow to the heart when AD occurs. These findings have significant clinical implications that extend beyond the context of UDS and demonstrate the importance of identifying early changes in HRV in order to accurately predict AD episodes in people living with SCI.

Reliability and Validity of Kubios HRV Smart Phone Application as Measures of Heart Rate Variability

Introduction: Heart rate variability (HRV) analysis has given a non-invasive way for assessing cardiac autonomic control. Reduced HRV is an independent indicator of poor prognosis in both heart disease patients and the general population. Aim/Objective: To establish reliability and validity for Kubios HRV smart phone application. Materials and methods: Fifty (n =50) office workers volunteered for the study, with 10 females and 40 males ranging in age from 30 to 50 years (Mean age =38.4±5.6). To evaluate Intra and Inter-rater reliability and validity the of HRV parameter, R-R intervals comparing simultaneous recording from ECG and Kubios HRV app, at different three times (day1,day2 &day3) one day apart and by two different trained examiners in the same participants. Each participants rested in supine for 10 minutes prior to the assessment and was instructed to remain relaxed, breathe properly, and refrain from talking and sleeping during the measurement. The RR intervals (R-R) were recorded during a 5 min period in supine position using ECG and polar H10 monitor with Kubios HRV smartphone application. Results: Kubios HRV smart phone application shows excellent reliability, Intra-rater (α =0.868) and Inter-rater (α =0.890) and Validity (r = 0.94) with R-R intervals calculated from ECG. Conclusion: The Kubios HRV smart phone application provides an accurate and reliable alternative to the ECG for acquiring inter-beat interval time series data. The Kubios HRV app gives an R-R interval that can be used for short term HRV analysis in office workers from steady resting conditions, supporting the selection of this approach of evaluation in research and clinical practise.

HEART RATE VARIABILITY DURING PHYSICAL EFFORT IN PATIENTS WITH METASTATIC OVARIAN CANCER AND CONCOMITANT OBESITY

Introduction. One of the main factors affecting postoperative outcomes in patients with advanced ovarian cancer is the cardiopulmonary status. Several studies have reported that preoperative multifactorial rehabilitation and physical fitness can lead to reduced postoperative morbidity, mortality, shorter length of stay, and improved quality of life in cancer patients. The issue of adaptability to physical activity of overweight and obese patients who undergoing debulking surgery is insufficiently studied. The study of compensatory changes that occur in physically inactive obese patients remains relevant, especially against the background of neoadjuvant chemotherapy, in the conditions of preoperative preparation with ERAS-recommended physical activity.
 The aim of the study is to determine the differences between women with advanced ovarian cancer and obesity compared to women with normal weight in terms of heart rate variability during exercise. To assess the adaptive capabilities to physical activity of patients with advanced ovarian cancer and obesity at the stage of preoperative preparation, who undergoing debulking surgery.
 Result. Achieved METs, peak HR, CI, and HR recovery were higher in nonobese women, whereas training had no significant effect in obese women. Women who had already received neoadjuvant CT achieved a lower level of MET (6.8 ± 3.2 vs. 8.9 ± 4.1; P < 0.001). Also, peak HR and CI were lower in women after neoadjuvant CT (126±27 vs. 138±20; P = 0.001 and 0.65±0.22 vs. 0.71±0.22; P = 0.001, respectively). BMI was a significant predictor of exercise capacity only in the obese subgroup, whereas age, peak HR, and prior adjuvant HT were always significantly associated with METs achieved.
 Conclusions. No significant difference was found between trained and untrained women with comorbid obesity in HR behavior or physical capacity. Different heart rate behavior in patients of this group is thus explained by obesity as such, regardless of the degree of physical training.

Autonomic nervous system and postural control regulation during orthostatic test as putative markers of physical resilience among community-dwelling older adults

IntroductionWe examined whether autonomic nervous system (ANS) and postural control regulation during orthostatic test reflect physical resilience by studying their associations with maximal walking speed and mortality. MethodsThe participants were community-dwelling Finnish men (n = 303) and women (n = 386) aged 75, 80, and 85 years at baseline. Systolic and diastolic blood pressure (BP), heart rate, heart rate variability (HRV), respiratory rate, and postural sway were obtained using a digital sphygmomanometer, a single-channel ECG, and thigh- and chest-worn accelerometers. Linear and Cox regression models were used to estimate the associations of the physiological indices with maximal 10-m walking speed and 5-year mortality separately for sexes. ResultsBetter maintenance of BP under orthostatic stress was associated with faster walking speed in women and lower mortality hazard in men. Greater HRV in terms of low frequency power and lower respiration rate in supine position and smaller orthostatic changes in these were associated with faster walking speed especially in women. Less postural sway after standing up was associated with faster walking speed in women (−0.057, SE 0.022, p = 0.011) and more postural sway with increased mortality hazard in men (HR 1.71, 95 % CI 1.20–2.43) even after controlling for BP responses. ConclusionsIn addition to ANS regulation at rest and under stress, adaptation of postural control system to orthostasis may be used in quantifying older adults' physical resilience. Wearable sensors capturing stimulus-response patterns and natural fluctuations of body functions may provide opportunities to monitor and incorporate different subsystems' resilience also in free-living conditions.

Reliability of carotid-femoral arterial waveforms for the derivation of ultra-short term heart rate variability in injured British servicemen: An inter-rater reliability study.

In this study, the comparative precision of carotid versus femoral arterial waveforms to measure ultra-short term heart rate variability (HRVUST) following traumatic injury was investigated for the first time. This was an inter-rater reliability study of 50 British servicemen (aged 23-44 years) with non-acute combat-related traumatic injury (CRTI). Paired continuous arterial waveform data for HRVUST analysis, were simultaneously sampled at the carotid and femoral arterial sites (14-16 seconds) during pulse wave velocity (PWV) measurement. HRVUST was reported as the root mean square of the successive differences (RMSSD). Following the determination of the superior sampling site (carotid versus femoral), the blinded inter-rater agreement in RMSSD for the preferred site was quantified using the Intra-class Correlation Coefficient (ICC) and the Bland-Altman plot. The mean age of participants was 34.06±4.88 years. The femoral site was superior to the carotid site with a significantly higher number of reliable signals obtained (Fisher's Exact test; p<0.001). The inter-rater agreement in femoral-derived RMSSD was excellent [ICC 0.99 (95%CI: 0.994-0.997)] with a moderate level of agreement (mean difference [bias]: 0.55; 95% CI: -0.13-1.24 ms). In this study, we demonstrated that the femoral artery is a more reliable site than the carotid artery for HRVUST measurement and post-trauma risk stratification following CRTI.

Long-term changes in heart rate and electrical remodeling contribute to alternans formation in heart failure: a patient-specific in silico study.

Individuals with chronic heart failure (CHF) have an increased risk of ventricular arrhythmias, which has been linked to pathological cellular remodeling and may also be mediated by changes in heart rate. Heart rate typically fluctuates on a timescale ranging from seconds to hours, termed heart rate variability (HRV). This variability is reduced in CHF, and this HRV reduction is associated with a greater risk for arrhythmias. Furthermore, variations in heart rate influence the formation of proarrhythmic alternans, a beat-to-beat alternation in the action potential duration (APD), or intracellular calcium (Ca). In this study, we investigate how long-term changes in heart rate and electrical remodeling associated with CHF influence alternans formation. We measure key statistical properties of the RR-interval sequences from ECGs of individuals with normal sinus rhythm (NSR) and CHF. Patient-specific RR-interval sequences and synthetic sequences (randomly generated to mimicking these statistical properties) are used as the pacing protocol for a discrete time-coupled map model that governs APD and intracellular Ca handling of a single cardiac myocyte, modified to account for pathological electrical remodeling in CHF. Patient-specific simulations show that beat-to-beat differences in APD vary temporally in both populations, with alternans formation more prevalent in CHF. Parameter studies using synthetic sequences demonstrate that increasing the autocorrelation time or mean RR-interval reduces APD alternations, whereas increasing the RR-interval standard deviation leads to higher alternans magnitudes. Importantly, we find that although both the CHF-associated changes in heart rate and electrical remodeling influence alternans formation, variations in heart rate may be more influential.NEW & NOTEWORTHY Using patient-specific data, we show that both the changes in heart rate and electrical remodeling associated with chronic heart failure influence the formation of proarrhythmic alternans in the heart.

Pattern of Heart Rate Variability in Somatoform Disorder and Its Association with Anxiety level: An Analytical Study

Background: Somatoform disorder (SD), nowadays considered as the most frequent psychiatric diagnosis in general practice has strong association with anxiety. Though there are a handful of studies showing heart Rate variability (HRV) in SD patients, as such no studies according to author’s knowledge had been addressed to the anxiety component hidden in the SD patients applying HRV tests so far. Aims: Aim of the current study was assess the presence and extent of Heart rate variability in SD patients and to find out it’s possible relationship with their anxiety level. Materials and Methods: An analytical observational cross-sectional study was done among fifty newly diagnosed somatoform disorder patients of eighteen to forty years age attending Psychiatry OPD and fifty age and sex matched healthy control. After assessing their anxiety level using State Trait Anxiety Inventory, Short term Heart rate Variability tests were performed. Appropriate Statistical tests were applied using SPSS 20 version. Results: The SD patients showed reduced heart rate variability as SDNN and RMSDD were less, LF and LF/HF ratio were more in them than controls and significant differences were there. Both SAS and TAS scores were more in cases and there was positive correlation of TAS score with LF and LF/HF ratios. Conclusions: The results of this study actually set an alarm for controlling their symptoms as well as their hidden anxiety underneath, as reduced HRV poses the risk of developing cardiovascular disease and hidden anxiety has influence on heart rate variability.

Impact of Sequential Practice of Kaphalabhati and Nadi Shodhana Pranayama on Heart Rate Variability in Healthy Volunteers

Background: Pranayama or breath technique is considered as an important component of yoga, which influence wide range of physiological and psychological functions. Practice of Kaphalabhati (KB) and Nadi Shodhana Pranayama (NSP) are known breathing techniques to influence the autonomic functions. The sequential practice of KB and NSP has not been assessed. In this Context, we assessed the immediate effect of combined practice of KB and NSP on autonomic variables in healthy subjects. Materials and Methods: A prospective analytical cross-sectional study was conducted and recruited 28 healthy participants who admitted in SDM Nature cure and Yoga hospital, Dharmasthala for the positive promotion of the health/general well-being. All participants were practiced KB 60 strokes/min for 5 rounds followed by NSP 1:1 ratio, 5 seconds inhalation and 5 seconds exhalation without any retention for 12 rounds. The Heart Rate Variability (HRV) was assessed through MP150 data acquisition system and blood pressure was recorded by using a standard mercury sphygmomanometer. We assessed the BP, Heart Rate (HR), Short term HRV at baseline and immediately after the practice. Results: The mean age (SD) of the participants was 33.29 (6.9). The study showed significant decrease in Systolic blood pressure, Diastolic Blood Pressure and RMSSD. There were borderline changes in the time domain measures (Mean R-R, NN50, pNN50) and reduction in the frequency domain of the HRV (LF, HF, LF/HF). However, the difference was not statistically significant. Conclusion: Immediate effect of sequential practice of KB and NSP in healthy volunteers showed positive effect in reduction of SBP, DBP and RMSSD. It can be included in the routine clinical practice for better outcome in the cardiovascular parameters and for the general well-being. Further studies are requisite to give insight in the underlying mechanism.

CONSEQUENCES OF BRISK WALK, MODERATE INTENSITY CONTINUOUS AND HIGH INTENSITY INTERVAL TRAINING ON SHORT-TERM HEART RATE VARIABILITY IN HEALTHY YOUNG ADULTS

Background: Short term heart rate variability is a time saving non-invasive measure of autonomic nervous system dysfunction. This study was conducted to assess and compare the effect of walking, medium intensity continuous and high-intensity interval training exercise modalities on short-term heart rate variability. Methods: This experimental study was conducted at the Department of Physiology, Islamic International Medical College, Rawalpindi, from August 2018 to August 2019. A total of 31 non-obese, healthy young individuals, free of comorbidities were included in the study. Participants were assigned through randomization to walk for 30 minutes intervention (n=10), medium intensity continuous training (MICT) intervention (n=11) and high-intensity interval training (HIIT) intervention (n=10). Intervention groups completed a total of 24 sessions in 7 weeks. Heart rate variability (HRV) analysis was performed by a 15-minute ECG recording before and after 24 sessions of intervention. ECGs were recorded by using the PowerLab® model 4/25T and the data were analysed using the software LabChart® Pro-8.0 with HRV 2.0 module installed. Results: After 24 sessions of 30-minute brisk walking exercise of 3,000 steps in an open area revealed a significant improvement in some HRV components when compared with pre-intervention levels of mean R-R interval (p=0.02), LFms2 (p=0.02) and LF/HF ratio (p=0.03). No significant differences were recorded after MICT and HIIT interventions among the groups. Conclusion: Compared to MICT and HIIT, a brisk walk in an open area was found to be effective mode of physical activity for improvement of HRV. Pak J Physiol 2023;19(1):21–5

Relationship between combat-related traumatic injury and ultrashort term heart rate variability in a UK military cohort: findings from the ADVANCE study

IntroductionCombat-related traumatic injury (CRTI) has been linked to an increased cardiovascular disease (CVD) risk. The long-term impact of CRTI on heart rate variability (HRV)—a robust CVD risk marker—has not been...

Chemogenetic stimulation of the parasympathetic nervous system lowers hepatic lipid accumulation and inflammation in a nonalcoholic steatohepatitis mouse model

AimsThe role of the parasympathetic nervous system (PNS) in the pathogenesis of nonalcoholic steatohepatitis (NASH) is largely unknown. In this study, the effect of PNS modulation on NASH was investigated using chemogenetics. Main methodsA streptozotocin (STZ) and high-fat diet (HFD)-induced NASH mouse model was used. To activate or inhibit the PNS, chemogenetic human M3-muscarinic receptor coupled with either Gq or Gi protein-containing viruses was injected into the dorsal motor nucleus of the vagus at week 4 and clozapine N-oxide was administered intraperitoneally for a week from week 11. Three groups (PNS-stimulation, PNS-inhibition, and control) were compared in terms of heart rate variability (HRV), histological lipid droplet area, nonalcoholic fatty liver disease activity score (NAS), the area of F4/80-positive macrophages, and biochemical responses. Key findingsThe STZ/HFD-treated mouse model showed typical histological characteristics of NASH. HRV analysis confirmed that PNS-stimulation and PNS-inhibition groups had significantly higher and lower PNS activity, respectively (both P < 0.05). The PNS-stimulation group showed a significantly smaller hepatic lipid droplet area (14.3 % vs. 20.6 %, P = 0.02) and lower NAS (5.2 vs. 6.3, P = 0.047) than the control group. The area of F4/80-positive macrophages was significantly smaller in the PNS-stimulation group than in the control group (4.1 % vs. 5.6 %, P = 0.04). The PNS-stimulation group showed a lower serum aspartate aminotransferase level than the control group (119.0 vs. 356.0 U/L, P = 0.04). SignificanceIn STZ/HFD-treated mice, chemogenetic stimulation of the PNS significantly reduced hepatic fat accumulation and inflammation. The hepatic PNS may play a pivotal role in the pathogenesis of NASH.

Data-driven, patient-specific simulations of long-term heart rate variability and cardiac alternans formation.

Individuals suffering from chronic heart failure (CHF) have a greater risk for death mediated by ventricular arrhythmias, which may be related to changes in heart rate. Heart rate constantly fluctuates from beat-to-beat on a timescale ranging from seconds to hours under physiological conditions, termed heart rate variability (HRV). Individuals with CHF have reduced HRV and faster heart rates, both of which influence the formation of pro-arrhythmic alternans, a beat-to-beat alternation in the action potential duration (APD) and intracellular calcium (Ca) levels. It is unclear how long-term changes in heart rate influence alternans and arrhythmia formation. We obtained sequences of RR intervals (time between successive R waves in an electrocardiogram) from individuals with normal sinus rhythm (NSR) and CHF from a Physionet database. These RR-sequences are used to define the pacing period for a discrete-time coupled map model of APD and intracellular Ca cycling for a single cardiac myocyte, modified to account for human heart rates and pathological Ca-remodeling in CHF. These modifications include fitting human ventricular myocyte APD restitution parameters, including a new term for Ca leak from the sarcoplasmic reticulum (SR), and scaling SR Ca-related parameters. Importantly, this minimal model enables simulation of long-term trends, on the order of 24 hours, in large populations. We find that the alternations in APD and Ca vary over time, such that there are periods with both small and large beat-to-beat differences in both populations. However, the CHF population tends to have a larger alternations magnitude, demonstrating that CHF-associated heart rates promotes more pro-arrhythmic phenomena. Future work will extend this methodology to determine what statistical properties govern the CHF RR-sequences, and further to test to what extent pro-arrhythmic alternans depends on CHF-related changes in heart rate or remodeling.

Predictors of Heart Rate Variability: A Systematic Review

Introduction: The heart has the ability to maintain cardiac output in accordance with the body’s momentarily changing demands by adjusting its rate of contractions and this ability is termed Heart Rate Variability (HRV), which is manifested as a fluctuation of R-R interval in milliseconds on an Electrocardiography (ECG). Maintenance of good HRV levels is significant for the patient population since they influence the prognosis and quality of life. Aim: To identify the predictors of HRV. Materials and Methods: The present study was a systematic and literature review which was based on Preferred Reporting Items for Systematic reviews and Meta-Analysis (PRISMA) guidelines 2020. Randomised Controlled Trials (RCTs) published in English from 2014 to 2021 were identified from Cochrane Library, Science Direct, PubMed, and Google Scholar databases. The keywords with Boolean operators were used as “influencing factors or determinants or predictors and HRV.” The quality assessments of the studies were performed with Cochrane risk-of-bias assessment tool. Narrative syntheses upon the selected studies were done. Results: The significant findings from the nine selected RCTs were summarised. Physical exercise, breathing exercise, diet, music, and mind-body interventions such as yoga and meditation were identified as the factors enhancing HRV or predictors of HRV. Conclusion: The findings of this systematic review strive to facilitate healthcare providers to devise the strategies to support the risk group of low HRV by the implementation of enhancing factors of HRV to achieve a better outcome.

Assessment of soundscapes using self-report and physiological measures

Soundscape studies evaluate the subjective and objective qualities of an environment and attempt to develop a holistic view of the interplay between the acoustic scene and the listener’s experience. Descriptors are used to express the perception of the acoustic environment, while further subjective and quantitative measures are used as indicators that represent features of the acoustic environment. The relationships between descriptors and indicators for a particular soundscape study are often identified by developing linear statistical models. This work describes an experiment to assess heart rate measures, including ultra short term heart rate variability, within the context of the predictor descriptor framework of a soundscape study. The aim of this work is to provide evidence in support of the psychophysiological basis of measures of affect in soundscape evaluation. In this study 15 participants evaluated a randomly ordered set of 8 soundscape recordings in a repeated measures directed listening experiment. Subjective evaluation of the soundscapes was performed using the self-assessment manikin and a sound classification survey. Participants’ heart rate was measured throughout the experiment with a Polar H10 ECG heart rate monitor. Statistically significant relationships were identified between indicators and descriptors that reflect results present in the literature. However, there were no significant interactions between heart rate measures and self-reported affect or classification scores. Future studies should focus on improving the selection of stimuli and the experiment methodology to boost the sensitivity of the experiment in light of small effect sizes.

Abstract 14985: Artificial Intelligence Based Heart Rate Variability Analysis for Sudden Cardiac Arrest Risk Prediction

Introduction: Sudden Cardiac Arrest (SCA) is an unexpected life-threatening loss of cardiac function potentially leading to sudden cardiac death (SCD). It accounts for a half of cardiac mortality, posing a major public health problem. While SCA can be treated with implantable cardioverter defibrillators (ICD), most (80%) SCDs occur in relatively low risk patients, for whom risk benefit ratio of an ICD is unfavorable. Therefore, novel methods to identify high risk individuals and the time on which their risk is high may facilitate prevention of SCD. Methods : Long (~24h) ECG recordings from individuals who had an SCA on record (n=20), patients with other arrhythmias (n=84) and from healthy individuals (n=17) from PhysioNet databases were analyzed to extract inter beat intervals (IBI). For each step in the IBI series, 120 last IBIs were used to calculate 19 indices that quantify short term heart rate variability (HRV). An artificial intelligence model named temporal convolutional network (TCN) was used to continuously assess the risk of a future VF event based on the current HRV estimate combined with few hours of history of previous HRV estimates. Training and testing of the TCN was done using Leave One Out testing done twice. Patients being classified at any point in the record as high risk were considered high risk. Results : Only patients from the SCA population, and none from the other arrythmia and healthy patients, were classified as high risk (PPV=100%). On average, sensitivity and specificity were 62.5% and 100% respectively Conclusions : In this preliminary retrospective analysis, artificial intelligence based HRV analysis identified risk for a SCA event in the following 24 hours with high specificity. Larger cohort and prospective testing are needed to assess the clinical utility of such systems.

Short term Heart Rate Variability in Rats

Objective: A sustainable animal model is needed to detect Cardiovascular autonomic dysfunctions, which can be assessed by recording electrocardiogram and analysis of heart rate variability (HRV). Therefore, the present study tried to find out the duration for HRV analysis for reliable results.Material and methods: Recording of Electroencephalogram (ECG) is reported in many articles. However, there is no information regarding the duration of ECG to be considered for the HRV analysis. Adult Wistar rat were used for a recording of ECG and HRV analysis. A combination of Ketamine 50 mg/kg and Xylazine 10 mg/kg was used for anesthésia in all the recordings. We analyzed the HRV parameters for all the records with 10 different durations starting from 1 minute to 10 minutes and compared.Results and Discussion: It was observed that, ECG parameters were within normal range while the data from HRV analysis from different duration showed wide discrepancies depending on the duration of ECG recording used for HRV analysis.Conclusion: The minimum duration of eight minutes of recording is likely to produce acceptable data for HRV parameters.

Diagnostic Efficacy of Ultra-Short Term HRV Analysis in Obstructive Sleep Apnea.

Heart rate variability (HRV) is the standard method for assessing autonomic nervous system (ANS) activity and is considered a surrogate marker for sympathetic overactivity in obstructive sleep apnea (OSA). Although HRV features are usually obtained from the short-term segment method, it is impossible to evaluate rapid dynamic changes in ANS activity. Herein, we propose the ultra-short-term analysis to detect the balance of ANS activity in patients with OSA. In 1021 OSA patients, 10 min HRV target datasets were extracted from polysomnographic data and analyzed by shifting the 2 min (ultra-short-term) and 5 min (short-term) segments. We detected frequency-domain parameters, including total power (Ln TP), very low frequency (Ln VLF), low frequency (Ln LF), and high frequency (Ln HF). We found that overall HRV feature alterations indicated sympathetic overactivity dependent on OSA severity, and that this was more pronounced in the ultra-short-term methodology. The apnea-hypopnea index, oxygen desaturation index, and Epworth sleepiness scale correlated with increased sympathetic activity and decreased parasympathetic activity, regardless of the methodology. The Bland-Altman plot analyses also showed a higher agreement of HRV features between the two methodologies. This study suggests that ultra-short-term HRV analysis may be a useful method for detecting alterations in ANS function in OSA patients.

EXPERIMANTAL RESEARCHES OF OPERATOR-PILOT PERFORMANCE AND DEVELOPMENT OF HIS ACTIONS SUPPORT

Efficiency is an external manifestation of a person’s ability to perform purposeful activities of any kind, including professional activities. The main performance indicator is its level recorded by the on-board monitoring system in terms of heart rate variability (HRV) of the operator-pilot. A feature of the implemented approach in assessing the PL (performance level) indicator (in addition to obtaining a generalized integral indicator at the time of completion of the flight task) is that current indicators are used at different phases of the flight task, due to which the history of PL is tracked in the dynamics of changes in the working state with the identification of situations in which the support is required. Ensuring and maintaining the health (capacity) of the operator-pilot in the remote telepsychophysiological interactive interface mode “Pilot in the cockpit of the aircraft – flight director at the command point” showed the high efficiency of the proposed technology, tested at KPM-V. Such an interface was implemented on the basis of a broadband communication channel – information exchange as part of the KPM-V, and the flight director at the command point (CP) has the opportunity to prototype the situation and its development in order to develop more reliable expert recommendations to the operator-pilot. The interface, including the developed on-board biofeedback system, presents on its monitor of information signs of the external manifestation of the operator’s states in terms of the frequency and nature of respiratory movements. Changes in the structure of the wave respiratory packet spoke about the state of the operator and his performance. Comparison of these data in a single time with the HRV indicators made it possible to qualify the situation as the transition of the operator into a state of working stress, developing fatigue and overwork. The results of a semi-natural experiment with specific expert support (recommendations) of the operator-pilot performing low-altitude flight in difficult weather conditions with the search for objects of interest showed that suggesting a more advantageous maneuver for entering the zone of possible active actions from the CP made it possible to reduce the current level of performance at the time of support, not allow its predicted decrease by 20…30 % and increase the time for making a decision and its implementation by 10…13 s. At the same time, the reliability of the expert forecast of the operator’s PL according to the data of the analysis of the respiratory wave packet on the thermograms of the face was 70…90 %. The conducted cycle of research on the problem of the operator-pilot’s performance, its provision and support is not only of research interest, but can be used in the ergonomic examination of aviation equipment and the design of the crew’s work activities.