Heart Rate Variability Spectrum Research Articles

Phenotypes of COVID-19-associated dysautonomia in patients requiring veno-venous extracorporeal membrane oxygenation

Background. Patients with novel coronavirus infection (COVID-19) receiving veno-venous extracorporeal membrane oxygenation (VV-ECMO) are typically prone to hemodynamic disorders of various severity. Tachycardia, increased cardiac output, or arterial hypotension affect the effectiveness of VV-ECMO. One of the possible causes of hemodynamic disorders leading to ineffective VV-ECMO may be dysautonomia (DA), which refers to an imbalance of sympathetic and parasympathetic divisions of the autonomic nervous system (ANS). The development of DA in various critical conditions was described previously. Dysautonomia also develops in COVID-19 (COVID-19-associated DA), but it was studied only in stable non-ICU patients. The presented study focuses on COVID-19-associated DA in critical COVID-19 patients requiring VV-ECMO support. The study was aimed at determining COVID-19-associated DA phenotypes, their impact on VV-ECMO effectiveness and disease outcomes. Materials and methods. The study included 20 patients: 12 (60%) females, 8 (40%) males. The patients had an average age of 55 years. All the patients underwent 24-hour Holter monitoring with spectral analysis of heart rate variability (HRV) assessing low-frequency component of the spectrum (LF), the high-frequency component of the spectrum (HF), the LF/HF ratio on days 1, 3, and 5 of VV-ECMO. Diagnostic criteria for COVID-19-associated DA was a decrease in LF/HF 2.28 or an increase in LF/HF 6.94. The diagnostic criteria of predominant tone of sympathetic nervous system (sympathetic tone) was an increase in LF/HF 6.94, while a decrease in LF/HF 2.28 indicated predominant parasympathetic tone. Low sympathetic tone was determined by a decrease in LF 15%, and an increase in LF 40%. Low parasympathetic tone was determined by a decrease in HF 15%, and an increase in HF 25%. The criteria used were based on the results of previous studies. The following parameters were registered in the study population: VV-ECMO weaning, duration of respiratory and VV-ECMO support, length of stay in the intensive care unit (ICU) and in hospital, and disease outcomes. Results. COVID-19-associated DA was diagnosed in all the patients. LF/HF median value was 0.1. HRV spectrum parameters changed significantly over time: on day 5 of VV-ECMO support LF and HF values significantly decreased. The patients were divided into three groups according to the DA phenotype: group 1 (n = 4 [20%]) with normal sympathetic tone and high parasympathetic tone (nShP phenotype); group 2 (n = 14 [70%]) with low sympathetic tone and high parasympathetic tone (lShP phenotype); group 3 (n = 2 [10%]) with low sympathetic tone and normal parasympathetic tone (lSnP phenotype). The latter group was excluded from further statistical analysis due to the small sample size. In group 2, the mean HR was significantly higher compared with group 1. In group 1, VV-ECMO weaning was successful in 50% of cases, whereas in group 2 it was successful in 7.2% (p = 0.04). Conclusions. To determine a dysautonomia phenotype, it is necessary to continuously monitor DA status in COVID-19 patients during VV-ECMO. Tachycardia in COVID-19 patients during VV-ECMO does not exclude the ANS imbalance with a significant predominance of parasympathetic tone over the sympathetic tone. It is this COVID-19-associated DA phenotype that is significantly associated with the unfavorable outcomes.

Phenotypes of COVID-19-associated dysautonomia in patients requiring veno-venous extracorporeal membrane oxygenation

Background. Patients with novel coronavirus infection (COVID-19) receiving veno-venous extracorporeal membrane oxygenation (VV-ECMO) are typically prone to hemodynamic disorders of various severity. Tachycardia, increased cardiac output, or arterial hypotension affect the effectiveness of VV-ECMO. One of the possible causes of hemodynamic disorders leading to ineffective VV-ECMO may be dysautonomia (DA), which refers to an imbalance of sympathetic and parasympathetic divisions of the autonomic nervous system (ANS). The development of DA in various critical conditions was described previously. Dysautonomia also develops in COVID-19 (COVID-19-associated DA), but it was studied only in stable non-ICU patients. The presented study focuses on COVID-19-associated DA in critical COVID-19 patients requiring VV-ECMO support. The study was aimed at determining COVID-19-associated DA phenotypes, their impact on VV-ECMO effectiveness and disease outcomes. Materials and methods. The study included 20 patients: 12 (60%) females, 8 (40%) males. The patients had an average age of 55 years. All the patients underwent 24-hour Holter monitoring with spectral analysis of heart rate variability (HRV) assessing low-frequency component of the spectrum (LF), the high-frequency component of the spectrum (HF), the LF/HF ratio on days 1, 3, and 5 of VV-ECMO. Diagnostic criteria for COVID-19-associated DA was a decrease in LF/HF 2.28 or an increase in LF/HF 6.94. The diagnostic criteria of predominant tone of sympathetic nervous system (sympathetic tone) was an increase in LF/HF 6.94, while a decrease in LF/HF 2.28 indicated predominant parasympathetic tone. Low sympathetic tone was determined by a decrease in LF 15%, and an increase in LF 40%. Low parasympathetic tone was determined by a decrease in HF 15%, and an increase in HF 25%. The criteria used were based on the results of previous studies. The following parameters were registered in the study population: VV-ECMO weaning, duration of respiratory and VV-ECMO support, length of stay in the intensive care unit (ICU) and in hospital, and disease outcomes. Results. COVID-19-associated DA was diagnosed in all the patients. LF/HF median value was 0.1. HRV spectrum parameters changed significantly over time: on day 5 of VV-ECMO support LF and HF values significantly decreased. The patients were divided into three groups according to the DA phenotype: group 1 (n = 4 [20%]) with normal sympathetic tone and high parasympathetic tone (nShP phenotype); group 2 (n = 14 [70%]) with low sympathetic tone and high parasympathetic tone (lShP phenotype); group 3 (n = 2 [10%]) with low sympathetic tone and normal parasympathetic tone (lSnP phenotype). The latter group was excluded from further statistical analysis due to the small sample size. In group 2, the mean HR was significantly higher compared with group 1. In group 1, VV-ECMO weaning was successful in 50% of cases, whereas in group 2 it was successful in 7.2% (p = 0.04). Conclusions. To determine a dysautonomia phenotype, it is necessary to continuously monitor DA status in COVID-19 patients during VV-ECMO. Tachycardia in COVID-19 patients during VV-ECMO does not exclude the ANS imbalance with a significant predominance of parasympathetic tone over the sympathetic tone. It is this COVID-19-associated DA phenotype that is significantly associated with the unfavorable outcomes.

Cardio-Metabolic Indices in Relation to Serum Vitamin D Levels among Middle-Aged Adults

A plethora of research showed that vitamin D deficiency is one of the most prevalent dietary inadequacies in India. The condition is addressed as hypovitaminosis-D and often intervenes with the occurrence of diseases like cardio-metabolic disease. Though several epidemiological studies have supported this fact, there is an insufficiency of rational data to support the fact. Hence the current study investigates the relationship between vitamin D levels and markers of cardio-metabolic diseases among middle-aged adults. This study recruited 100 healthy middle-aged adults, and the participants underwent evaluation of their anthropometric measurements, Heart Rate Variability (HRV), and serum vitamin D levels. Analysis was done by taking consideration of total power (TP), absolute, and normalized power of high-frequency (HF), and low-frequency (LF) power spectrum including their ratio (LF/HF) as HRV indices. Data analysis was performed using the Pearson correlation test. Data analysis showed a negative correlation between vitamin D and anthropometric measurements and a positive correlation with cardiac sympathovagal balance as determined by waist circumference and LF/HF ratio. However, there was no discernible correlation between vitamin D levels and the BMI, fat percentage, Systolic Blood Pressure (SBP), Diastolic Blood Pressure (DBP), absolute power spectrum of HRV. The results of this study conclude that serum vitamin D levels affect central obesity and cardiac sympathovagal balance, indicating low levels of serum vitamin D might contribute higher risk for cardiovascular diseases.

Analysis of heart rate indices at different levels of sleepiness

The objective detection of sleepiness through physiological indices is crucial for ensuring transportation and industrial safety. As gadgets become more commonplace for measuring heart rate, it is important to identify valid indices that correlate with the level of sleepiness. Research indicates that time-domain and frequency-domain heart rate indices align with levels of alertness and sleepiness [e.g., 1, 2]. The aim of this paper is to identify heart rate indices that correlate with varying degrees of evening sleepiness in vivo, whether low or high. The data analyzed in this paper was obtained from 32 recordings from the SSDD (Subjective Sleepiness Dynamics Dataset) collected at the UNN Cyberpsychology Laboratory since 2022. The experiment was designed in the following manner: participants put on a heart rhythm sensor (Polar H10) at 7:40 PM in their homes and connected it to a smartphone app. Participants then completed a self-reported questionnaire in the electronic system. Starting at 8:00 PM, and every 30 minutes thereafter, the participant recorded data on the subjective level of sleepiness via the Karolinska (KSS) and Stanford (SSS) sleepiness scales up until the time of the participant’s bedtime. The selection of 32 recordings met specific criteria: all participants went to bed between 10:30 and 11:00 PM and completed both the KSS and SSS on time at each time point (08:00, 08:30, 09:00, 09:30, and 10:00 PM). For each time point, an integral sleepiness score was calculated according to the formula: sl=(KSS/10+SSS/7)/2. The 4-minute rhythmogram recordings corresponding to the time points of KSS and SSS filling were chosen for analysis. Data were processed in Jupyter Notebook. Heart rhythm indices, including time-domain, frequency-domain, and nonlinear indices, were computed for each time point from the rhythmogram — NN-interval sequence — using the “hrv-analysis” package. The study employed Student’s t-test to compare indices for varying levels of sleepiness based on integral scores, where “low level” was defined as sl 0.45 and “high level” was defined as sl 0.55. Additionally, the Pearson criterion was used to evaluate the correlation between sl and heart rate indices at each time interval. The indices responsible for the variability of the NN-interval sequence, namely NNi_50 (p=0.027), NNi_20 (p=0.007), and pNNi_20 (p=0.024), exhibited lower values during periods of “low” sleepiness (N=54) as compared to “high” sleepiness (N=58). Moreover, we observed that the autonomic balance index, i.e., the ratio of the power of the heart rate variability spectrum in the low-frequency band to that in the high-frequency band, was higher during ‘high’ sleepiness (p=0.015). Analysis revealed that correlations between integral sleepiness score and heart rate indices were present only for the 08:30 PM time point. Correlations of sl with the NN-interval range (R=–0.388; p=0.028), the severity of sympathetic regulatory circuit activity (R=–0.383; p=0.031), and the nonlinear cardiovagal index (R=–0.359; p=0.043) were found. Thus, it can be inferred that increased sleepiness is associated with decreased heart rate variability indices, along with decreased functioning of the autonomic nervous system overall.

Evaluation of autonomic disorders in miners with vibration disease

Introduction. Autonomic disorders in the form of autonomic neuropathy develop in vibration disease already at the early stages. As the disease progresses, the compensatory mechanisms of autonomic regulation are depleted, which leads to a worse prognosis for life and an increased risk of sudden cardiac death in patients with a severe degree of autonomic neuropathy. 
 The aim of the study was to evaluate the severity of autonomic disorders and the preservation of compensatory reserves of autonomic regulation in patients with vibration disease. 
 Materials and methods. One hundred thirty six miners with a proven diagnosis of vibration disease and 60 apparently healthy men of similar age without complaints and who had never worked under the conditions of exposure to industrial vibration were examined. Heart rate variability was analyzed at rest and during an active orthostatic test.
 Results. A decrease in the spectral parameters of heart rate variability in the patients with vibration disease was revealed. In a subgroup of the patients with an initially low level of very low frequency oscillations (less than 30 ms2/Hz), a decrease in the non-linear entropy index (less than 180) was determined; when performing an active orthostatic test, the power of very low frequency spectrum oscillations in the patients of this subgroup decreased by more than 50% of the initial values. In all patients with vibration disease under orthostatic load, a decrease in the oscillations of high and low frequencies of the spectrum of heart rate variability was revealed, whereas in the control group, the low frequency oscillation power remained at the initial level.
 Limitations. The study was limited to the evaluation of spectral and non-linear indices of heart rate variability in 136 miners with vibration disease. 
 Conclusion. The criteria for a severe course of autonomic neuropathy in the patients with vibration disease were identified: an initial decrease in the power of very low frequency oscillations and a non-linear entropy index of heart rate variability, as well as a decrease in the power of very low frequency oscillations by more than 50% during an orthostatic test. According to these criteria, in 40.4% of the miners with vibration disease, pronounced violations of the autonomic support with a lack of compensatory mechanisms of autonomic regulation were found to be detected.

Typological Features of the Heart Rate Autonomic Regulation under Simulating a Rise to a Height by Using Additional Respiratory Resistance

The aim of this work was to study the indicators of heart rate variability (HRV) under conditions of additional respiratory resistance (ADR), as an imitation of climbing to a height, in young men with different types of autonomic regulation. The study involved 715 young men aged 19 to 24 years. HRV parameters were assessed by the method of variational pulsometry (BioMouse). Each subject passed two tests lasting 5 min: background, and under conditions of DDS. An ETM 2.0 resistive mask was used to simulate climbing (ADS simulation), in three altitudes: 3000, 9000, 18000 feet. Each person performed only one test; the height of the lift was not reported to him. Based on the results of background testing, two groups were created: the OB group – with balanced sympathetic and parasympathetic influences on HRV (stress index 25–100 c.u., VLF above 240 ms2), the PT group – with a moderate predominance of parasympathetic (vagal) influences (stress index below 25 c.u., VLF above 500 ms2). In the background testing, the OB group was characterized by higher values of the Bayevsky indices (IVR, VPR, PAPR), reflecting the predominance of sympathetic tone, and the PT group had higher values of the variation range of the duration of R–R intervals, RMSSD, SDNN, pNN50%, which are considered markers of increased vagal tone, and the total power of the HRV spectrum TP. Under conditions of ADR, without taking into account the height of the simulated rise, in the OB group, an increase in indicators correlated with vagal activity was revealed: the range of R–R intervals, RMSSD, SDNN, the HF range in the HRV spectrum, with a decrease in the Baevsky indices (IVR, VPR, PAPR, stress index). The increase in spectral measures of HRV associated with sympathetic activity (LF%) ant TP reached the level of statistical significance only when simulating an ascent to an altitude of 18 000 feet. In the PT group, the changes were oppositely directed: a decrease in correlates of vagal activity and an increase in sympathetic tone, regardless of the height of the lift. However, in both groups, the range of R–R intervals increased the most at 9000 feet, which is critical for the development of mountain sickness. Differences in the autonomic regulation of the cardiovascular system in young men determine the direction and severity of shifts in HRV indicators when simulating a rise to a height. In the OB group under conditions of ADR, when simulating a rise to insignificant heights, the indicators associated with vagal activity increase, with an increase in the height of the rise, an increase in parameters reflecting the sympathetic tone joins them. In the PT group, an expected increase in sympathetic tone was found at all altitudes.

Resting-state EEG as a potential indicator to predict sleep quality in depressive patients

ObjectivesTo investigate the changes in sleep quality, heart rate variability (HRV) and resting-state electroencephalogram (rsEEG) in patients with major depressive disorder (MDD), and to explore whether HRV and rsEEG may be served as more convenient tools to assess sleep quality in MDD patients. MethodWe included a total of 91 subjects (46 healthy controls and 45 MDD patients) and compared their sleep quality, HRV and power spectra of rsEEG. Correlation analyses were conducted to discuss the relationship between HRV and seven factors of PSQI. Multiple linear regression model was used to examine whether absolute band power could predict sleep quality in MDD patients. ResultsWe found higher PSQI scores and lower levels of HRV in depressive individuals compared with healthy controls. In MDD patients, sleep latency was negatively correlated with RMSSD and HF. Delta, theta, and alpha band power of rsEEG were higher in MDD patients. Regression analyses showed delta band power of TP8, as well as theta, alpha band power of AF3 predicts PSQI score of MDD patients. ConclusionsThe findings of our study show that some aspects of sleep problems had negative correlations with parasympathetic activity and the regression model supports that the band power of rsEEG may be used as a potential indicator to evaluate the sleep quality in MDD patients. SignificanceCortical hyperarousal may be one of the reasons leading to poor sleep quality of MDD patients. And resting-state EEG can be used as a potential indicator for clinical assessment of MDD patients' sleep quality.

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.

Efficiency of the transcranial magnetic stimulation in the treatment 
 of occupational polyneuropathy

Introduction. In occupational polyneuropathies, along with sensory and autonomic disorders, excessive sensory input can lead to the development of excitation foci in various parts of the central nervous system, clinical significance of which is currently insufficiently studied.
 The aim of the study was the evaluation of the clinical effects of the transcranial magnetic stimulation in the dorsolateral zone of the prefrontal cortex in mine workers with occupational polyneuropathy. 
 Materials and methods. There were examined thirty six workers of coal mining enterprises of Kuzbass with a proven diagnosis of polyneuropathy of the upper extremities, the average age was 50.2±3.7 years, and the average work experience was 23.4±3.5 years. To confirm polyneuropathy, the parameters of sensory conduction along the nerves of the upper extremities were investigated using electroneuromyography, nerve conduction velocity along the median and ulnar nerves was determined. The assessment of autonomic rcontrol was carried out using spectral analysis of heart rate variability. The functional brain status was determined by an electroencephalogram.
 Results. The patients complained of pain in the extremities, numbness and paresthesia. According to electroneuromyography, there was a decrease in the nerve conduction velocity along the somatic sensory nerves of the upper extremities, a reduction in the power of oscillations in all frequency ranges of the heart rate variability spectrum, which was more pronounced in the high frequency range. Transcranial magnetic stimulation of the prefrontal cortex zone of the right hemisphere was performed with a stimulus with a frequency of 1 Hz for 5 min, over a course of 5 procedures, after which a statistically significant increase in the average nerve conduction velocity along the somatic sensory nerves of the upper extremities, and a rise in the spectral parameters of the heart rate variability were observed. An increase in the alpha rhythm index at the electroencephalogram indicated an amplification of the integrative brain activity, which provided a wide range of regulatory processes. The patients noted a decrease in the intensity of pain, the severity of sensitive disorders, and improvement in general well-being.
 Limitations. The study is limited to the number of mine workers with a proven diagnosis of upper extremity polyneuropathy, without cardiac arrhythmias, structural damage and metal implants in the brain.
 Conclusion. Transcranial magnetic stimulation of the dorsolateral zone of the prefrontal cortex is effective in correcting sensory and autonomic disorders in occupationally caused polyneuropathy by activating suprasegmentary autonomic centers involved in systemic adaptation processes. It is promising to further expand the list of stimulation targets and create effective protocols for the use of transcranial magnetic stimulation.

Features of Heart Rate Variability in Male and Female Wistar Rats

In this study, we investigated the heart rate variability (HRV) of awake male and female Wistar rats using a non-invasive technique of electrocardiosignal recording. We established significant differences in the value of HRV indicators in groups of animals differing in spectral parameters (total power of the spectrum (TP), high-(HF) and low-frequency (LF) components of the spectrum). The following HRV indicators were shown to be highly informative: statistical (SDNN — the standard deviation of the complete array of RR intervals, RMSSD — the square root of the standard deviations of successive RR intervals, CV — the coefficient of variation) and spectral (TP, HF, LF, VLF is a very low–frequency component of the HRV spectrum, LF/HF is the vagosympathetic interaction index, IC — centralization index). The data obtained should be taken into account when advancing the existing methodology for studying the pathogenetic mechanisms of HRV changes and determining the prognostic value of these HRV parameters.

Природа общей мощности спектра и очень низкочастотных волн кардиоинтервалограммы с позиций адаптации организма человека к двигательной активности (обзор)

It is known that heart rate variability (HRV), evaluated using interval electrocardiography (ECG), reflects the influence of the autonomic nervous system (АNS) and biologically active substances on cardiac activity. For this reason, interval ECG method is widely used in sports, as it reveals the mechanisms of human adaptation to motor activity. This article analyses data on the median values of the total power (TP) of the HRV spectrum and absolute and relative power of very low frequency (VLF) waves on the interval electrocardiogram in athletes recorded in the supine position. We chose these three indicators out of more than 30 others due to their informativeness and due to the debatable issue of the nature of VLF waves. Literature data and unpublished results of our studies allow us to conclude that the values of these indicators in athletes depend on a number of factors, including type of sports (being especially high in sports building aerobic endurance), level of athletic skill (being maximum in elite athletes) as well as volume and intensity of training. In elite skiers, the values of these three indicators tend to change in the course of the training year, increasing in the preparatory phase, staying at a high level or even increasing during the competitive phase, and decreasing in the transition phase, which is determined by the relevant dynamics of the training volume throughout the year. The authors believe that the increase in the values of these three HRV indicators points to the growing influence of the parasympathetic division of ANS and non-neuronal acetylcholine on cardiac activity under heavy training volumes. According to the authors, the values of these three indicators reflect the level of aerobic motor activity (the higher they are, the higher this activity).

Sample, Fuzzy and Distribution Entropies of Heart Rate Variability: What Do They Tell Us on Cardiovascular Complexity?

Distribution Entropy (DistEn) has been introduced as an alternative to Sample Entropy (SampEn) to assess the heart rate variability (HRV) on much shorter series without the arbitrary definition of distance thresholds. However, DistEn, considered a measure of cardiovascular complexity, differs substantially from SampEn or Fuzzy Entropy (FuzzyEn), both measures of HRV randomness. This work aims to compare DistEn, SampEn, and FuzzyEn analyzing postural changes (expected to modify the HRV randomness through a sympatho/vagal shift without affecting the cardiovascular complexity) and low-level spinal cord injuries (SCI, whose impaired integrative regulation may alter the system complexity without affecting the HRV spectrum). We recorded RR intervals in able-bodied (AB) and SCI participants in supine and sitting postures, evaluating DistEn, SampEn, and FuzzyEn over 512 beats. The significance of "case" (AB vs. SCI) and "posture" (supine vs. sitting) was assessed by longitudinal analysis. Multiscale DistEn (mDE), SampEn (mSE), and FuzzyEn (mFE) compared postures and cases at each scale between 2 and 20 beats. Unlike SampEn and FuzzyEn, DistEn is affected by the spinal lesion but not by the postural sympatho/vagal shift. The multiscale approach shows differences between AB and SCI sitting participants at the largest mFE scales and between postures in AB participants at the shortest mSE scales. Thus, our results support the hypothesis that DistEn measures cardiovascular complexity while SampEn/FuzzyEn measure HRV randomness, highlighting that together these methods integrate the information each of them provides.

Preliminary study of heart rate variability in Criollo horses for the elucidation of their neurophysiological characteristics of autonomic nerve function.

The Criollo is an Argentine horse breed with a calm temperament. Although its temperament is considered to be related to its neurophysiological characteristics, the details of this are unknown. Therefore, we analyzed the heart rate variability in Criollos as a preliminary study to deepen the neurophysiological understanding of their autonomic function. Electrocardiograms were recorded from Criollos and Thoroughbreds, and the power spectrum of heart rate variability was analyzed. Compared with Thoroughbreds, Criollos showed (i) a significantly higher high-frequency component, which is an index of parasympathetic nerve activity, and (ii) tendency toward a lower ratio of low- to high-frequency power, which is an index of the autonomic balance. These results revealed that parasympathetic nerves might be more active in Criollos compared with Thoroughbreds.

Immediate Effects of OM Meditation on Heart Rate Variability as a Stress Index During Different Phases of Menstruation: A Quasi-Experimental Pilot Study

Introduction: Stress alters normal reproductive function, causing menstrual disorders up to infertility in females. Psychological stress is the most common lifestyle factor found to be associated with menstrual disorders among late adolescence and young adults. Yoga-based OM-meditation has been shown to reduce stress, but its effect on managing stress during different phases of menstruation in young females is not known. Aim: To evaluate if short-term practice of OM-meditation could induce a beneficial modulation in Heart-Rate Variability (HRV), a measure of stress index during various phases of the menstrual cycle in young females. Materials and Methods: A quasi-experimental study was conducted on 20 healthy young females with a normal menstrual cycle, aged between 18-25 years, and pursuing a medicine course at Shri BM Patil Medical College, Karnataka, India, from March 2020 to December 2021. Meditation group participants (n=10) practiced OM-meditation, while control group participants (n=10) relaxed quietly for 10 minutes. Each subject received an intervention thrice during the menstrual, proliferative, and secretory phases. Data was collected before and immediately after every intervention. Body Mass Index (BMI), Blood Pressure (BP), Heart Rate (HR), and HRV were measured. Distribution of data, within-group and betweengroup analysis was done. ANCOVA (Analysis of covariance) was used to determine the differences between groups. Results: Total 20 participants, n=10 in each, Meditation and control group, mean age of participants was 19.2±0.79 and 19.3±0.82 years, and the mean period of MC was 31.1±2.76 and 30.3±2.4 days in the meditation and control groups, respectively. There was no change in the baseline values of BMI, BP, and HR between the two groups, and they were within the normal range. Between-group analysis (ANCOVA) of HRV spectrum showed that OM-meditation had significantly decreased the LowFrequency (LF) component of HRV (p<0.05) and LF/HF ratio (p<0.05), and increased the High-Frequency (HF) component (p<0.05) of HRV during all three phases of MC. Conclusion: The practice of OM-meditation for 10 minutes reduced sympathetic activity and shifted autonomic balance towards parasympathetic dominance. These changes suggest that OM-meditation can reduce mental stress and optimise autonomic regulation during different phases of MC. However, this needs evaluation in a larger trial.

To the interpretation of frequency components of the heart rate variability

Assessing the sympathetic-vagal balance is an important task for predicting shifts in the functioning of the body when adapting to changing external conditions, as well as aging, various pathological processes and therapy. Today, the method of analyzing the spectrum of heart rate variability (HRV) for determining the sympathetic-vagal balance due to its simplicity and non-invasiveness has become widespread both in clinical practice and in experimental studies. The article analyzes the results of our own and literary studies of influence of various effects on hemodynamic parameters, the level of circulating catecholamines, sympathetic nervous activity, the baroreceptor reflex, and also on the components of the HRV spectrum (LF (low frequency), HF (high frequency) and LF/HF). Often different authors under the same impact register different changes. Reasons for this include different doses of drugs, nature/strength of exposure (for stress and exercise), time between drug administration and registration. In addition, the effect of some drugs can be enhanced in the case of pathology, such as hypertension. Based on the comparison of the vectors of changes in the studied parameters, we concluded that, using the frequency analysis of HRV, it is necessary to draw a conclusion about the sympatho-vagal balance with great care due to the ambiguous nature of LF component, but HF component gives information of the tone of the vagus with sufficient accuracy.

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

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

A study of Heart Rate Variability (HRV) in healthy offsprings with parental history of type 2 diabetes mellitus

Introduction: Type 2 diabetes mellitus (T2DM) is a heterogeneous polygenic metabolic disease condition that is caused by insulin resistance leading to hyperglycemia. Since, T2DM is genetically inherited and autonomic dysfunction is its major complications, healthy offsprings of diabetic parents are highly vulnerable to manifest dysautonomia leading to insulin resistance.
 Objectives: We aimed to assess cardiac autonomic function using heart rate variability (HRV) parameters in healthy offsprings having parental history of T2DM.
 Methodology: A comparative cross-sectional study was carried out in the laboratory of department of Physiology enrolling 30 healthy offsprings of non-diabetic parents (Group 1) and 30 healthy offsprings of diabetic parents (Group 2). Anthropometric, biochemical and cardiovascular variables were assessed using standard procedures. Time domain and frequency domain parameters of HRV spectrum were assessed using photoplethysmography principle.
 Results: HRV findings revealed that markers of sympathetic regulation were significantly higher and those of parasympathetic function were significantly reduced in subject group having parental history of T2DM. LF/HF ratio was significantly increased suggesting sympatho-vagal imbalance in offspring of diabetic parents even in their euglycemic state.
 Conclusion: Alteration of cardiovascular autonomic function is found in healthy offspring of diabetic parents, characterized by reduced vagal activity and pronounced sympathetic regulation. Assessment of cardiac autonomic function would help in timely detection of such dysautonomia and reducing the life-threatening effects on offspring having parental history of T2DM.

Abnormal heart rate variability during non-REM sleep and postictal generalized EEG suppression in focal epilepsy

ObjectiveTo identify any relationship between abnormal interictal heart rate variability (HRV) during sleep and the occurrence of postictal generalized EEG suppression (PGES), a potential biomarker of sudden unexpected death in epilepsy (SUDEP), in patients with focal epilepsy. MethodsWe retrospectively reviewed 34 consecutive patients with focal epilepsy, who presented with focal to bilateral tonic-clonic seizures (FBTCSs), 19 with PGES (PGES+) and 15 without PGES (PGES−), and 14 patients without epilepsy as controls. HRV spectrum analysis was performed for periods of 10 minutes during wakefulness, non-REM sleep, and REM sleep. HRV spectra consisted of high frequency (HF) and low frequency (LF) regions. Normalized HF representing parasympathetic activities and normalized LF were compared between the PGES+, PGES−, and control groups for each sleep stage. ResultsThe PGES+ group showed significantly decreased normalized HF and increased normalized LF during non-REM sleep compared to the PGES− (P < 0.05) and control (P < 0.01) groups, but not during wakefulness or REM sleep. ConclusionsAbnormal interictal HRV during non-REM sleep, indicating abnormally decreased parasympathetic activities, was associated with PGES in patients with FBTCS. SignificanceThis study proposes to further investigate the relation between decreased parasympathetic activities and PGES.

Relationship Between Cardiac Autonomic Markers and Degree of Cardiac Reinnervation in Heart Transplant Patients: Insights from a Mathematical Model

<h3>Purpose</h3> Cardiac sympathovagal balance is often assessed using autonomic markers derived from cardiac rhythm, however, their relationship to the degree of reinnervation after heart transplantation is still not fully understood. This study aimed to investigate the influence of various levels of vagal and sympathetic cardiac reinnervation on the respective autonomic cardiac markers using a mathematical model of the human cardiovascular system. <h3>Methods</h3> The model integrates chronotropic and inotropic effects of arterial baroreflex and pulmonary stretch reflex, known as main contributors to heart rate variability. The markers of interest included resting heart rate, bradycardic and tachycardic heart rate response to Valsalva maneuver, root mean square error of normalized RR-intervals (RMSDD), high-frequency (HF) power, low-frequency (LF) power, and total power of the heart rate variability spectrum. To analyze how well different levels of sympathetic or vagal cardiac reinnervation can be discriminated through cardiac autonomic markers, five groups of increasing reinnervation levels were formed. The strength of the relationship between the level of cardiac reinnervation was quantified by Spearman's correlation coefficients. <h3>Results</h3> The results suggest that for assessment of vagal cardiac reinnervation levels <20%, resting heart rate (ρ=0.99, p<0.05), RMSDD (ρ=0.97, p<0.05), and total spectral power (ρ=0.89, p<0.05) may be equally suitable as the commonly used measure of HF-power (ρ=0.88, p<0.05). To assess sympathetic reinnervation, our results suggest that LF/HF-ratio (ρ=0.88, p<0.05) and tachycardic response to Valsalva maneuver (ρ=0.84, p<0.05) may be more suitable than LF-power (ρ=0.82, p<0.05). <h3>Conclusion</h3> Our model reports, for the first time, mechanistic relationships between cardiac autonomic markers and degrees of vagal/sympathetic reinnervation. The results suggest differences in the performance of cardiac autonomic markers to assess vagal and sympathetic reinnervation. Although our analysis is purely theoretical yet, the developed mathematical model can provide important insights into the genesis of autonomic cardiac markers and their relationship to cardiac reinnervation and provide indications for clinical study evaluation. This work is funded by the EU-Project NeuHeart (824071).

Telemedical transport layer security based platform for cardiac arrhythmia classification using quadratic time–frequency analysis of HRV signal

The heart rate variability signal is a valuable tool for cardiovascular system diagnostics. Processing this signal detects arrhythmia during long-term cardiac monitoring. It is also analyzed to recognize abnormalities within the autonomic nervous system. Processing this signal helps in detecting various pathologies, such as atrial fibrillation (AF), supraventricular tachycardia (SVT), and congestive heart failure (CHF). As a beneficial alternative to the commonly used HRV spectrum analysis, quadratic time–frequency analysis of HRV signals could be helpful in heart pathology detection. Indeed, in this study, we have created a client-server paradigm deployed as a telemedical platform for real-time remote monitoring of the cardiovascular function in patients suffering from arrhythmia. This platform detects arrhythmia in real-time by deploying time–frequency analysis, feature extraction, feature selection, and classification of Heart Rate Variability (HRV) signals. We gathered all these functionalities in a Graphical User Interface (GUI) in addition to data acquisition. As a client, a Raspberry Pi Zero ensures data acquisition and connects to a server over TCP/IP that involves a 4G/3G connection encrypted through the transport layer security (TLS). This telemedical tool continuously monitors the heart rate variability. In the case of an alarm, medical professionals may immediately interact with their patients in the hospital or at home.