Power spectrum analysis of heart rate fluctuation: a quantitative probe of beat-to-beat cardiovascular control

Heart Rate Variability Modulation Through Slow-Paced Breathing in Health Care Workers with Long COVID: A Case-Control Study

BACKGROUND

Long COVID is a syndrome persisting 12+ weeks after COVID-19 infection, impacting life and work ability. Autonomic nervous system imbalance has been hypothesized as the cause. This study aims to investigate cardiovascular autonomic function in health care workers (HCWs) with Long COVID and the effectiveness of slow-paced breathing (SPB) on autonomic modulation.

METHODS

From December 1, 2022 to March 31, 2023, 6655 HCWs of the University Hospitals of Trieste (Northeast Italy) were asked to participate in the study by company-email. Inclusion/exclusion criteria were assessed. Global health status and psychosomatic disorders were evaluated through validated questionnaires. Heart rate variability was assessed by finger-photoplethysmography during spontaneous breathing and SPB, which stimulate vagal response. Long COVID HCWs (G1) were contrasted with Never infected (G2) and Fully recovered COVID-19 workers (G3).

RESULTS

There were 126 HCWs evaluated. The 58 Long COVID were assessed at a median time because COVID-19 of 419.5 days (interquartile range 269-730) and had significantly more psychosomatic symptoms and lower detectability of spontaneous systolic pressure oscillation at 0.1 Hz (Mayer wave - baroreflex arc) during spontaneous breathing compared with 53 never-infected and 14 fully-recovered HCWs (19%, 42%, and 40%, respectively, P = .027). During SPB, the increase in this parameter was close to controls (91.2%, 100%, and 100%, respectively, P = .09). No other differences in heart rate variability parameters were found among groups.

CONCLUSIONS

Resting vascular modulation was reduced in Long COVID, while during SPB, baroreflex sensitivity effectively improved. Long-term studies are needed to evaluate whether multiple sessions of breathing exercises can restore basal vascular reactivity and reduce cardiovascular risk in these patients.

Attenuated cardiac autonomic function in patients with long-COVID with impaired orthostatic hemodynamics

PURPOSE

Long-coronavirus disease (long-COVID) is associated with initial orthostatic hypotension and postural orthostatic tachycardia syndrome. Whether altered autonomic tone underlies these abnormalities is unknown. We compared autonomic function between patients with long-COVID and healthy controls, and within patients with long-COVID with different orthostatic hemodynamic phenotypes.

METHODS

Patients with long-COVID (n = 94; F = 76; 42 years [36, 53 years] with initial orthostatic hypotension: n = 40; F = 32; 49 years [39, 57 years]; postural orthostatic tachycardia syndrome: n = 29; F = 26; 39 years [33, 47 years]; or no abnormalities: n = 25; F = 18; 42 years [35, 49 years]), and healthy controls (n = 33; F = 25; 49 years [30, 62 years]) completed a 10-min active stand with beat-to-beat hemodynamics. Heart rate variability, blood pressure variability, and baroreflex sensitivity were calculated as indirect measures of cardiovascular autonomic health. Continuous data (median [95% confidence interval]) were analyzed with Mann-Whitney U tests or Kruskal-Wallis tests with Dunn's corrections.

RESULTS

Patients with long-COVID had lower upright high frequency heart rate variability (p = 0.04) and low frequency blood pressure variability (p = 0.001) than controls. Patients with initial orthostatic hypotension had lower supine baroreflex sensitivity compared with patients without abnormalities (p = 0.01), and lower supine baroreflex sensitivity (p = 0.001) and high frequency heart rate variability (p = 0.03) than patients with postural orthostatic tachycardia syndrome. Patients with postural orthostatic tachycardia syndrome had lower upright high frequency heart rate variability (p < 0.001) and baroreflex sensitivity (p < 0.001) compared with patients without abnormalities and lower upright low frequency blood pressure variability (p = 0.04) compared with controls.

CONCLUSIONS

Patients with long-COVID have attenuated cardiac autonomic function. Patients with initial orthostatic hypotension have lower supine baroreflex sensitivity. Patients with postural orthostatic tachycardia syndrome have lower upright vascular sympathetic and cardiac parasympathetic modulation. Long-COVID subgroups do not present with homogeneous pathophysiology, necessitating targeted treatment strategies.

Effects of urination process on heart rate variability

PURPOSE

Heart rate variability (HRV) is used for the assessment of activity of the autonomic nervous system (ANS). As urination is also under the control of the ANS, this study aimed to investigate the usefulness of HRV in the assessment of ANS during the peri-urination period. The psychological effects of sitting on a chair or on the toilet during pre- and post-urination periods were also assessed.

METHODS

Electrocardiogram was used to measure HRV in male participants (n = 40, aged 18-30). They were allowed to drink water to ease urination. At the stage close to voiding, six measurements (each for 90 s) were taken sequentially in sitting position (pre-urination chair, pre-urination toilet, urination, post-urination toilet, post-urination chair, and basal post-urination chair). HRV indices included standard deviation of R-R intervals (SDNN), root mean square of successive differences in R-R intervals (RMSSD), percentage of successive R-R intervals differing more than 50 ms (pNN50), total power (TP), very-low-frequency (VLF), low-frequency (LF), and high-frequency (HF) bands together with the ratio of LF/HF.

RESULTS

HR, SDNN, TP, LF, and LF/HF increased during urination process (P < 0.05), whereas RMSSD, pNN50, and HF increased before urination on toilet (P < 0.05) compared to sitting on a chair before and after urination.

CONCLUSION

HRV indices dynamically reflected the physiological stages of urination. Parasympathetic activity (revealed by pNN50, RMSSD, and HF) increased before urination, whereas sympathovagal balance (revealed by LF/HF) increased during urination. Thus, HRV appears to be a suitable technique for studying physiological and pathological aspects of urination.

Autonomic nervous system and mediating role of respiratory function in patients with ALS

Patients with Amyotrophic Lateral Sclerosis (ALS) exhibit altered patterns of respiratory rate and heart rhythm that are directly related to autonomic nervous system (ANS) activity. This study aimed to analyze the role of the ANS in respiratory function, cognition, functionality, and antioxidant capacity in patients with ALS through a predictive model that assesses the mediating activity of respiration. This quantitative, observational, analytical, and cross-sectional clinical study was conducted using a sample of 75 patients diagnosed with ALS. ANS activity, respiratory function, cognition, functionality, and antioxidant capacity were also measured. Using these values, a structural equation model was developed using AMOS V.23 software. The mediational predictive model showed that increased sympathetic nervous system (SNS) activity, in turn, increased respiratory function, whereas the role of the parasympathetic nervous system in respiration was very weak and had the opposite effect. Furthermore, SNS activity increased respiratory function values, which, in turn, improved functional capacity, cognition, and antioxidant power in patients with ALS, with respiratory function playing a mediating role. The mediating effect of respiratory function was observed primarily between ANS and functional disability. For oxidative stress, respiratory function showed a high mediating effect, such that greater respiratory function corresponded to greater antioxidant capacity. Additionally, for cognitive activity, a moderate direct effect of the ANS was observed; however, it was greatly enhanced by respiratory disability. Finally, differences were only found based on sex, with respiratory capacity and antioxidant power being higher in men.

Classifying metro drivers' cognitive distractions during manual operations using machine learning and random forest-recursive feature elimination

Metro drivers are more likely to trigger accidents if they suffer from cognitive distractions during manual driving. However, identifying metro drivers' cognitive distractions faces challenges as generally no obvious behavior can be found during the distractions. To address the challenge, this paper identifies metro drivers' cognitive distractions based on Electrocardiogram (ECG) signals collected by wearable devices in simulated driving experiments. The ECG signals are processed to generate ultra-short-term heart rate and heart rate variability (HR-HRV) features. The HR-HRV features are extracted by 30-s and 60-s time-windows in driving phase, and 25-s time-windows in parking phase, respectively. Machine learning approaches are developed to identify distractions (binary) and distinguish the degrees of distractions (multi-class). The optimal input features are determined by a random forest and recursive feature elimination (RF-RFE) algorithm. Results show that the DT with only one HR-HRV feature extracted from 30-s time-windows and XGBoost with 20 h-HRV features extracted from 60-s time-windows are optimal models for binary and multi-class classification for distractions during driving phase, respectively. The features including NN20, pNN20, SD1/SD2, Max-HR, Min-HR, and MEDNN are the most critical HR-HRV features associated with distractions. Cognitive distractions in parking phase are difficult to be detected using HR-HRV features.

Alterations in the autonomic and haemodynamic response to prolonged high-intensity endurance exercise in individuals with coronary artery calcification

Endurance exercise is associated with increased life duration and improved life quality. Paradoxically, high exercise intensity is also associated with increased coronary artery calcification (CAC) and a small but significant increased risk of adverse cardiac events during exercise. The mechanisms underlying the development of CAC during prolonged high-intensity endurance exercise are unknown. This study aims to determine if there are differences in cardiovascular haemodynamic measures and heart rate variability (HRV) in individuals with (CAC+) and without CAC (CAC-). Hemodynamic measures from 56 healthy, middle-aged (median [interquartile range] 51 [43-58] years) individuals (41 men/15 women) participating in a 91 km [251.2 [217.2-271.6] min] leisure sport mountain bike race were included in this study. Twenty-five participants (20 men/5 women) were classified as CAC+ based on coronary computed tomographic assessment. Haemodynamic measures and HRV were quantified at the top of the hardest hill (THH) during the last quarter of the race. At the top of THH, CAC+ individuals had significantly higher systolic blood pressure (SBP) (235 [225-245] mmHg vs. 220 [193-238] mmHg, P = 0.008), higher diastolic blood pressure (DBP) (105 [95-110] mmHg vs. 95 [85-110] mmHg, P = 0.006), higher pulse pressure (130 [125-140] mmHg vs. 123 [110-130] mmHg, P = 0.039), higher mean rate pressure product (33,882 [30,872-35,053] bpm × mmHg vs. 31,028 [27,392-33,047] bpm × mmHg, P = 0.028), and larger increase in DBP from baseline (20 [20-30] mmHg vs. 10 [0-20] mmHg, P = 0.001), compared with CAC- individuals. Further, CAC+ participants showed a significant reduction in the low-frequency component of HRV (HRVLF) (6.3 [2.4-11.5] ms2 vs. 12.4 [6.8-20.2] ms2, P = 0.044). In multivariable analysis, HRVLF was an independent predictor of the presence of CAC even after adjusting for established risk factors of atherosclerosis: age, sex, body mass index, maximum heart rate,V ̇ O 2 max ${{\dot{V}}_{{{{\mathrm{O}}}_{\mathrm{2}}}{\mathrm{max}}}}$ , smoking, resting SBP and resting DBP. CAC+ individuals had significant alterations in haemodynamic measures and HRVLF following prolonged high-intensity endurance exercise compared with individuals without CAC. HRVLF was an independent predictor of CAC, suggesting an adverse autonomic response to high-intensity endurance exercise in individuals with CAC.

Future of Sleep Medicine: Novel Approaches and Measures Derived from Physiologic Systems Dynamics (Part I)

We review recent progress in understanding fundamental aspects of physiologic regulation during wake and sleep based on modern data-driven, analytical, and computational approaches with a focus on the complex dynamics of individual physiologic systems. The presented empirical findings indicate that sleep-wake and circadian cycles do not simply modulate basic physiologic functions but influence physiologic systems dynamics simultaneously over a broad range of time scales. The reviewed empirical approaches and derived measures represent novel mechanistic aspects of sleep and wake regulation, and lay the foundation for a new class of diagnostic and prognostic biomarkers in clinical sleep medicine.

The difference in arterial baroreflex sensitivity between the supine and standing positions in healthy subjects

The spectral analysis of heart rate variability (HRV) has long been considered a practical, noninvasive tool to assess autonomic nervous functions that regulate the cardiovascular system. The conventional method, however, has limitations in characterizing transient changes of HRV. We have overcome this problem by adopting the time-frequency analysis method. Using this method, we attempted to clarify differences in the arterial baroreflex (ABR) activity during a transient change in the heart rate between the supine and standing positions in healthy subjects. We found that the ABR gain was significantly greater in the supine position compared to standing, and this gain increase was due to transient increases in 0.15 to 0.20 Hz components of HRV spectral powers caused by enhanced cardiac vagal outflow. Based on these findings, we conclude that the orthostatic stress induced by the postural change from supine to standing markedly reduces the baroreflex gain by suppressing high-frequency cardiac vagal outflow.

Posttraining Dry Cupping Treatment Elevates Heart Rate Variability in Taekwondo Athletes

ABSTRACT

Elite taekwondo (TKD) athletes require physical strength and mastery of complex techniques to excel in a highly competitive environment. This study aimed to investigate the effects of dry cupping posttraining on heart rate variability (HRV) and recovery in TKD athletes. Fourteen male TKD athletes participated in a crossover study and were randomly assigned to either a dry cupping (Group CUP) or a placebo group without cupping (Group PLA) after completing a standardized TKD-specific training program. A 28-day washout period was implemented between the two treatments to minimize potential carryover effects. HRV and rated perceived exertion (RPE) were evaluated at three-time points: before training (Pre), immediately after training (Post), and 30 min after rest or dry cupping (Post30) in both groups. The results indicated that heart rate (HR) at Post and Post30 was significantly higher than at Pre in both groups. Low frequency (LF) and the LF/high frequency (HF) ratio at Post were significantly elevated compared to Pre in both groups. However, at Post30, these values remained significantly higher in Group PLA but not in Group CUP. HF at Post was significantly reduced compared to Pre in both groups, but at Post30, this reduction persisted only in Group PLA and not in Group CUP. Significant differences in the levels of LF, HF, and the LF/HF ratio were observed between Group PLA and Group CUP at Post30. The CUP group also showed significantly lower RPE compared to the PLA group at Post30. In conclusion, dry cupping treatment after TKD training significantly improved HRV parameters and reduced perceived fatigue, suggesting its potential as an effective method for enhancing recovery in TKD athletes.

Cardiac parasympathetic denervation reduces hypoxic tachycardia, baroreflex sensitivity and heart rate variability in humans

The autonomic regulation of heart rate (HR) reactivity to acute hypoxia remains unclear. Parasympathetic cardioneuroablation (PCNA) may serve as a novel model for the analysis of physiological consequences of reduced vagal influence over sinus node in humans. We studied 11 adult patients scheduled for PCNA for the treatment of vasovagal syncope. HR reactivity to hypoxia was studied before and after PCNA with brief nitrogen gas administrations. Each test was followed by an atropine challenge to evaluate the contribution of parasympathetic tone to the resting HR. Additionally, we assessed changes in cardiac baroreflex sensitivity and HR variability following the procedure. PCNA led to partial parasympathetic denervation of sinus node at rest (67.0 ± 20.1%). This translated into a significant change in HR reactivity to hypoxia (0.58 ± 0.21 vs. 0.22 ± 0.13 beats min- 1%SpO2 - 1, p = 0.0001) which was proportional to the degree of cardiac vagal denervation (R = 0.76, p = 0.01). There was no change in peak HR on atropine following PCNA implying unchanged sympathetic input to sinus node. This suggests that HR reactivity to acute hypoxia is significantly influenced by parasympathetic system. Additionally, despite incomplete vagal denervation PCNA resulted in profoundly depressed HR variability and cardiac baroreflex sensitivity. The clinical meaning of the latter should be explored in further studies.

Disruption in Autonomic Nervous Activity Is Associated With Central and Peripheral-Level in Dry Eye With Unstable Tear Film

Purpose

To measure autonomic nerve activity (ANA) in several eye conditions and verify whether ANA modulation is regulated by peripheral or central control in short tear film break-up time dry eye (sBUTDE).

Methods

This study included 23 eyes of 23 patients with sBUTDE (mean age 55.2 ± 16.1 years; range 21-88 years) and 24 eyes of 24 age-matched non-dry eye (DE) controls. An ANA measurement, personality questionnaire, and Ocular Surface Disease Index were administered. ANA was continuously measured for 10 minutes under three conditions: eyes closed, eyes open, and eyes open under ocular surface anesthesia.

Results

The low-frequency (LF)/high-frequency (HF) ratio (LF/HF) with eyes closed was significantly higher in the sBUTDE group than in the control group (P < 0.05). In the sBUTDE group, HF increased and LF/HF decreased with eye opening compared with those in the control group; HF with eyes open decreased with ocular surface anesthesia and reached the same level as that in the control group. Among patients where HF decreased or LF/HF increased with eye opening, 57.1% or 64.3% showed a tendency to return to the ANA state with eyes closed by ocular surface anesthesia, respectively. Factors associated with DE symptoms included break-up time, HF with eyes open, and "openness" (P < 0.05).

Conclusions

ANA modulation can be caused by peripheral, central, or mixed abnormalities in sBUTDE. Furthermore, personality traits may play a role in symptom induction. Understanding the pathogenesis of sBUTDE may aid in the treatment of cases that are refractory to conventional treatments.

Physiological, biochemical, and genome-wide expression patterns during graded normobaric hypoxia in healthy individuals

The regulation of oxygen homeostasis is critical in physiology and disease pathogenesis. High-altitude environment or hypoxia (lack of oxygen) can lead to adverse health conditions such as high-altitude pulmonary edema (HAPE) despite initial adaptive physiological responses. Studying genetic, hematological and biochemical, and the physiological outcomes of hypoxia together could yield a comprehensive understanding and potentially uncover valuable biomarkers for predicting responses. To this end, healthy individuals (n = 51) were recruited and exposed to graded normobaric hypoxia. Physiological parameters such as heart rate (HR), heart rate variability (HRV), oxygen saturation (Spo2), and blood pressure (BP) were constantly monitored, and a blood sample was collected before and after the hypoxia exposure for the hematological and gene-expression profiles. HR was elevated, and Spo2 and HRV were significantly reduced in a fraction of inspired oxygen ([Formula: see text])-dependent manner. After exposure to hypoxia, there was a minimal decrease in HCT, red blood cell distribution width (RDW)-coefficient of variation (CV), mean platelet volume (MPV), platelet distribution width, plateletcrit, eosinophils, lymphocytes, and HDL cholesterol. Additionally, there was a marginal increase observed in neutrophils. The effect of hypoxia was further assessed at the genome-wide expression level in a subset of individuals. Eighty-two genes significantly differed after hypoxia exposure, with 46 upregulated genes and 36 downregulated genes (P ≤ 0.05 and log2-fold change greater than ±0.5). We also conducted an integrative analysis of global gene expression profiles linked with physiological parameters, and we uncovered numerous reliable gene signatures associated with BP, Spo2, HR, and HRV in response to graded normobaric hypoxia.NEW & NOTEWORTHY Our study delves into the multifaceted response to hypoxia, integrating gene expression and hematological, biochemical, and physiological assessments. Hypoxia, crucial in both physiology and pathology, prompts varied responses, necessitating a thorough systemic understanding. Examining healthy subjects exposed to graded normobaric hypoxia, we observed significant shifts in heart rate, oxygen saturation, and heart rate variability. Moreover, genomic analysis unveiled distinct gene signatures associated with physiological parameters, offering insights into molecular perturbations and adaptations to oxygen deprivation.

Heart rate variability metrics and myocardial recovery in heart failure with reduced ejection fraction

PURPOSE

Autonomic dysregulation is observed in heart failure (HF) with reduced ejection fraction (HFrEF). Abnormal heart rate variability (HRV), a measure of such dysregulation, is associated with poor prognosis in HFrEF. It is unknown if novel HRV metrics normalize in the patients with recovered ejection fraction (HFrecEF) compared to persistent HFrEF. The aim of this study was to investigate novel HRV indexes in persistent HFrEF in comparison to HFrecEF METHODS: A standard 10-min electrocardiography measurement was performed in patients categorized in four groups: persistent HFrEF (n = 40), HFrecEF (n = 41), stage A HF (n = 73) and healthy controls (n = 40).

RESULTS

All HRV indexes were significantly different between the four groups. Specifically, novel metrics, such as higher parasympathetic nervous system (PNS) index and lower sympathetic nervous system (SNS) index, were observed in the HFrecEF group compared to the persistent HFrEF group. In multiple logistic regression analysis, higher PNS index (odds ratio [OR] 2.02, 95% confidence interval [CI] 1.17-3.49; p = 0.01) and lower SNS index (OR 0.68, 95% CI 0.52-0.87; p = 0.002) were associated with HFrecEF. Receiver operating characteristic analysis showed that the SNS index had the highest area under the curve (AUC), followed by the PNS index and mean heart rate for the HF phenotype regarding EF recovery (AUC = 0.71, 0.69 and 0.69, respectively).

CONCLUSION

Myocardial functional recovery in HFrEF is associated with improved parasympathetic activity and reduced sympathetic activity, as reflected in the PNS and SNS indexes. These novel metrics can be potentially used to aid in identifying recovered versus non-recovered phenotypes in patients with HFrEF.

Quality in Question: Assessing the Accuracy of Four Heart Rate Wearables and the Implications for Psychophysiological Research

Heart rate (HR) and heart rate variability (HRV) are two key measures with significant relevance in psychophysiological studies, and their measurement has become more convenient due to advances in wearable technology. However, photoplethysmography (PPG)-based wearables pose critical validity concerns. In this study, we validated four PPG wearables: three consumer-grade devices (Kyto2935, Schone Rhythm 24, and HeartMath Inner Balance Bluetooth) and one research-grade device (Empatica EmbracePlus, successor to the widely-used but discontinued Empatica E4). All devices were worn simultaneously by 40 healthy participants who underwent conditions commonly used in laboratory research (seated rest, arithmetic task, recovery, slow-paced breathing, a neuropsychological task, posture manipulation by standing up) and encountered in ambulatory-like settings (slow walking and stationary biking), compared against a criterion electrocardiography device, the Vrije Universiteit Ambulatory Monitoring System (VU-AMS). We determined the signal quality, the linear strength through regression analysis, the bias through Bland-Altman analysis, and the measurement error through mean arctangent absolute percentage error for each condition against the criterion device. We found that the research-grade device did not outperform the consumer-grade devices in laboratory conditions. It also showed low agreement with the ECG in ambulatory-like conditions. In general, devices captured HR more accurately than HRV. Finally, conditions that deviated from baseline settings and involved slight to high movement, negatively impacted the agreement between PPG devices and the criterion. We conclude that PPG devices, even those advertised and designed for research purposes, may pose validity concerns for HRV measurement in conditions other than those similar to resting states.

Non-Invasive Auricular Vagus Nerve Stimulation Decreases Heart Rate Variability Independent of Caloric Load

The vagus nerve is crucial in regulating physiological functions, including the cardiovascular system. While heart rate (HR) and its variability (HRV) may provide non-invasive proxies of cardiac vagal activity, transcutaneous auricular vagus nerve stimulation (taVNS) has yielded mixed effects, with limited research on right branch stimulation. In a randomized crossover study with 36 healthy participants, we investigated taVNS effects on HR and HRV indexed by SDRR, RMSSD, HF-HRV, and LF/HF ratio. To assess the impact of the stimulation side (left vs. right ear) on cardiovascular indices and interaction with the physiological state, we recorded electrocardiograms in four sessions per person, covering three session phases: baseline, during stimulation (taVNS vs. sham), and post-milkshake consumption with stimulation. First, we found moderate evidence against taVNS affecting HR (BF10 = 0.21). Second, taVNS decreased HRV (multivariate p = 0.004) independent of physiological state, with strong evidence for RMSSD (BF10 = 15.11) and HF-HRV (BF10 = 11.80). Third, taVNS-induced changes were comparable across sides and stronger than sham, indicating consistent cardiovascular effects independent of the stimulation side. We conclude that taVNS reduces HRV as indexed by RMSSD, HF-HRV, and SDRR without altering HR, contradicting the assumption that taVNS per se increases cardiovagal activity as indexed by increased HRV due to stimulating vagal afferents. Instead, our results support the role of vagal afferent activation in arousal. Crucially, taVNS on both sides can safely modulate the cardiovascular system without increasing the risk of bradycardia or causing adverse events in healthy participants, offering new treatment possibilities.

The UNICA sleep HRV analysis tool: an integrated open-source tool for heart rate variability analysis during sleep

Heart rate variability (HRV) analysis during sleep plays a key role for understanding autonomic nervous system function and assessing cardiovascular health. The UNICA Sleep HRV analysis (UNICA-HRV) tool is a novel, open-source MATLAB tool designed to fill the gap in current HRV analysis tools. In particular, the integration of ECG and HRV data with hypnogram information, which illustrates the progression through the different sleep stages, eases the computation of HRV metrics in polysomnographic recordings. This integration is crucial for accurate phase-specific analysis, as autonomic regulation changes markedly across different sleep stages. The tool supports single- and multiple-subject analyses and is tailored to enhance usability and accessibility for researchers and clinicians without requiring extensive technical expertise. It implements and supports a variety of data inputs and configurations, allowing for flexible, detailed HRV analyses across sleep stages, employing classical and advanced metrics, such as time-domain, frequency-domain, non-linear, complexity, and Poincaré plot indexes. Validation of the tool against established tools like Kubios and PhysioZoo indicates its robustness and precision in generating reliable HRV metrics, that are essential not only for sleep research, but also for clinical diagnostics. The introduction of UNICA-HRV represents a significant simplification for sleep studies, and its open-source nature (licensed under a Creative Commons Attribution 4.0 International License) allows to easily extend the functionality to other needs.

Joint Analysis of Cardiovascular Control and Shear Wave Elastography to Determine Carotid Plaque Vulnerability

Background/Objectives: Carotid artery stenosis (CAS) is one of the main causes of stroke, and the vulnerability of plaque has been proved to be a determinant. A joint analysis of shear wave elastography, a radiofrequency echo-based wall tracking technique for arterial stiffness evaluation, and of autonomic and baroreflex function is proposed to noninvasively, preoperatively assess plaque vulnerability in asymptomatic CAS patients scheduled for carotid endarterectomy. Methods: Elastographic markers of arterial stiffness were derived preoperatively in 78 CAS patients (age: 74.2 + 7.7 years, 27 females). Autonomic and baroreflex markers were also assessed by means of an analysis of the beat-to-beat fluctuations in heart period and systolic arterial pressure, derived at rest in supine position (REST) and during active standing. Postoperative analysis identified 36 patients with vulnerable plaque (VULN) and 42 with stable plaque (STABLE). Results: Baroreflex sensitivity (BRS) at a respiratory rate decreased during STAND only in VULN patients, being much higher at REST compared to STABLE levels. Autonomic indexes were not helpful in separating experimental conditions and/or populations. The Young's modulus (YM) of the plaque was lower in the VULN group than in the STABLE one. Cardiovascular control and elastographic markers were significantly correlated only in VULN patients. A multivariate logistic regression model built combining YM and BRS at the respiratory rate improved the prediction of plaque vulnerability, reporting an area under the ROC curve of 0.694. Conclusions: Noninvasive techniques assessing shear wave elastography and baroreflex control could contribute to the early detection of plaque vulnerability in patients with asymptomatic CAS.

Tracking autonomic nervous system activity using surface ECG: Personalized, multiparametric evaluation

We present a concise review of the background, pitfalls, and potential solutions for the noninvasive evaluation and continuous tracking of cardiac autonomic nervous system activity (ANSA), using surface-ECG-accessible parameters, including heart rate (HR), heart-rate variability (HRV), and cardiac repolarization. These parameters have provided insights into the dynamics of cardiac ANSA in controlled experiments and have proved useful in risk assessment with respect to sudden cardiac death and all-cause mortality in some patient populations, as well as in implantable device programming. Yet attempts to translate these parameters from the laboratory environment to ambulatory settings have been hampered by the presence of multiple uncontrolled factors, including changes in blood pressure, body position, physical activity, and respiration frequency. We show that a single-parameter-based, simplified cardiac ANSA evaluation in an uncontrolled ambulatory setting could be inaccurate, and we discuss several approaches to improve accuracy. Discerning cardiac ANSA effects in uncontrolled ambulatory environments requires tracking multiple physiological processes, preferably using multisensor, multiparametric monitoring and controlling some physiological variables (e.g., respiration frequency); data fusion and machine-learning-based analytics are instrumental for developing more accurate personalized ANSA evaluation.

Autonomic Nervous System Activity before Atrial Fibrillation Onset as Assessed by Heart Rate Variability

Background

Neuromodulation has been shown to increase the efficacy of atrial fibrillation (AF) ablation procedures. However, despite its ability to influence the autonomic nervous system (ANS), the exact mechanism of action remains unclear. The activity of the ANS via the intracardiac nervous system (ICNS) can be inferred from heart rate variability (HRV). Therefore, this study aims to investigate the significance of changes in the ICNS prior to the onset of AF by analyzing the evolution of HRV in a large new cohort of patients.

Methods

We selected and annotated recordings with AF and atrial flutter from our database of 95,871 Holter recordings. Each recording included both sinus rhythm and one or more AF episodes. We computed parameters estimating parasympathetic activity (root mean square of successive RR interval differences (RMSSD) and percentage of successive RR intervals that differ by more than 50 ms (pNN50)), as well as HRV frequential parameters a few minutes before AF onset. To allow a minute-by-minute assessment of the parameter changes, we computed their values over 5-minute sliding windows, starting at 35 minutes before AF onset.

Results

The mean age of the whole group of patients was 71.1 ± 11.3 years (range 35-99), the total number of episodes was 1319 on 623 recordings from 570 patients, with an average of 2.1 ± 2.2 episodes per recording (range 1-17) and 2.3 ± 2.6 episodes per patient (range 1-21). The proportion of premature atrial contractions (PACs) increased from 4.8 ± 0.3%, 35 minutes before the onset of AF to 8.3 ± 0.4%, 5 minutes before the AF episode. We measured a statistically significant increase in very-low-frequency (VLF), low-frequency (LF), high-frequency (HF), RMSSD and pNN50 between 35 minutes and 5 minutes before AF onset.

Conclusions

Our data suggest that a significant short-term increase in vagal activity precedes most AF events. Dynamic changes in HRV parameters could be considered when determining the optimal neuromodulation strategies.

Comparison of 1-hour floatation-REST versus conventional napping on heart rate variability in active individuals

Objectives

This study aimed to investigate the short-term effects of a 1-hour floatation-resting environmental therapy (FLO) versus conventional napping (NAP) on heart rate variability (HRV) in highly trained individuals.

Methods

20 non-fatigued participants underwent a prospective randomised interventional study comparing the impacts of FLO and NAP on both supine and standing HRV. Measurements were taken before and after each intervention under controlled conditions, and subjective experiences were assessed through questionnaires.

Results

FLO and NAP were associated with changes in HRV parameters but did so differently. NAP significantly enhanced supine parasympathetic activity, as evidenced by increased log-transformed root mean square of successive differences (p=0.02) and power spectral density (p=0.03) relative to heart rate (HR) values, confirming its effectiveness in promoting autonomic recovery. In contrast, despite being better perceived regarding subjective well-being (p=0.04), FLO conferred no significant changes in supine root mean square of successive differences and decreased power spectral density relative to HR (p=0.02). However, post-intervention comparisons were not statistically different. While supine HR decreased significantly following both interventions, standing HR measurements showed a non-significant increase for FLO compared with NAP (p=0.056).

Conclusion

In highly trained individuals, FLO and NAP demonstrated minimal impact on acute autonomic function. NAP appears more effective for enhancing short-term parasympathetic activity, while FLO provides a more enjoyable experience. These findings underscore the importance of personalised recovery strategies and emphasise the need for further research into individual responses and the long-term effects of these interventions.

Comparison of the impact of carotid endarterectomy and stenting on autonomic and baroreflex regulations: a one-year follow-up randomized study

Patients with carotid stenosis can receive indication for either carotid endarterectomy (CEA) or carotid artery stenting (CAS), with both techniques having an impact on the autonomic function and baroreflex control.Seventy carotid stenosis patients randomly assigned to CEA or CAS were enrolled. After exclusion of some recordings, 33 CEA (age 67.79 ± 5.32 yrs, 26 males) and 25 CAS (age 70.32 ± 3.63 yrs, 14 males) were admitted to analysis. Autonomic and baroreflex sensitivity markers were derived from the analysis of heart period and systolic arterial pressure spontaneous variability derived in supine position and during active standing (STAND), before (PRE) the intervention and after a 6 and 12-month follow-up (FU6, FU12).CEA had a preserved response of autonomic and baroreflex control to STAND in PRE and FU6, suggesting an early improvement. CAS had a similar response at PRE but a blunted one at the follow-ups. When directly compared, the two groups had a similar autonomic function, with CAS having a reduced baroreflex control in PRE and lower autonomic function at FU6. All the differences disappeared at the long-term follow-up, showing a similar long term effect of the surgical procedures, suggesting that CEA and CAS induced a similar long-term impairment of autonomic and baroreflex controls.

Linking brain-heart interactions to emotional arousal in immersive virtual reality

The subjective experience of emotions is linked to the contextualized perception and appraisal of changes in bodily (e.g., heart) activity. Increased emotional arousal has been related to attenuated high-frequency heart rate variability (HF-HRV), lower EEG parieto-occipital alpha power, and higher heartbeat-evoked potential (HEP) amplitudes. We studied emotional arousal-related brain-heart interactions using immersive virtual reality (VR) for naturalistic yet controlled emotion induction. Twenty-nine healthy adults (13 women, age: 26 ± 3) completed a VR experience that included rollercoasters while EEG and ECG were recorded. Continuous emotional arousal ratings were collected during a video replay immediately after. We analyzed emotional arousal-related changes in HF-HRV as well as in BHIs using HEPs. Additionally, we used the oscillatory information in the ECG and the EEG to model the directional information flows between the brain and heart activity. We found that higher emotional arousal was associated with lower HEP amplitudes in a left fronto-central electrode cluster. While parasympathetic modulation of the heart (HF-HRV) and parieto-occipital EEG alpha power were reduced during higher emotional arousal, there was no evidence for the hypothesized emotional arousal-related changes in bidirectional information flow between them. Whole-brain exploratory analyses in additional EEG (delta, theta, alpha, beta and gamma) and HRV (low-frequency, LF, and HF) frequency bands revealed a temporo-occipital cluster, in which higher emotional arousal was linked to decreased brain-to-heart (i.e., gamma→HF-HRV) and increased heart-to-brain (i.e., LF-HRV → gamma) information flow. Our results confirm previous findings from less naturalistic experiments and suggest a link between emotional arousal and brain-heart interactions in temporo-occipital gamma power.

Contactless and short-range vital signs detection with doppler radar millimetre-wave (76-81 GHz) sensing firmware

Vital signs such as heart rate (HR) and respiration rate (RR) are essential physiological parameters that are routinely used to monitor human health and bodily functions. They can be continuously monitored through contact or contactless measurements performed in the home or a hospital. In this study, a contactless Doppler radar W-band sensing system was used for short-range, contactless vital sign estimation. Frequency-modulated continuous wave (FMCW) measurements were performed to reduce the influence of a patient's micromotion. Sensing software was developed that can process the received chirps to filter and extract heartbeat and breathing rhythm signals. The proposed contactless sensing system eliminates the need for the contact electrodes, electric patches, photoelectric sensors, and conductive wires used in typical physiological sensing methods. The system operates at 76-81 GHz in FMCW mode and can detect objects on the basis of changes in frequency and phase. The obtained signals are used to precisely monitor a patient's HR and RR with minimal noise interference. In a laboratory setting, the heartbeats and breathing rhythm signals of healthy young participants were measured, and their HR and RR were estimated through frequency- and time-domain analyses. The experimental results confirmed the feasibility of the proposed W-band mm-wave radar for contactless and short-range continuous detection of human vital signs.

Cardiovascular effects of early maternal separation and escitalopram treatment in rats with depressive-like behaviour

Depression and cardiovascular diseases are two of the world's major health problems. Escitalopram (ESC) is widely used because of its safety in relation to other drugs in that class; however, it can affect the cardiovascular system. The present study evaluated the cardiovascular parameters of depressive-like male rats and the cardiovascular effects of ESC treatment on that condition. The EMS protocol consisted of separating the litter from the dam for 3 h over 13 days. Animals were anesthetized with tribromoethanol (250 mg/kg, intraperitoneally) and the catheters were inserted into the femoral and into the femoral vein. Depressive-like rats showed an increase in the pressor response to phenylephrine (Emax:depressive = 50.36 ± 2.997 mmHg; non-depressive = 39.51 ± 3.328 mmHg; p < 0.05) and a reduction in the EC50 (depressive = 0.6203 ± 0.03005 μg/kg; non-depressive = 0.7320 ± 0.03519 μg/kg; p < 0.05) with no change in the other cardiovascular parameters. After treatment with ESC, a reduction of intrinsic heart rate was observed in the depressive-like rats (control: 342 ± 6 bpm; ESC: 316 ± 5 bpm; p < 0.05). In addition, ESC treatment increased the bradycardic (control: -97.81 ± 8.3 bpm; ESC: -137.1 ± 12.31 bpm; p = 0.0236; t = 2.502) during the baroreflex response, caused by an increase in cardiac parasympathetic modulation in the heart, in depressive-like rats (p < 0.001). The findings suggest that depressive-like rats showed cardiovascular changes, and that ESC treatment was able to reverse these changes, suggesting that ESC has a good safety profile for depressive patients with cardiovascular disease due to increased parasympathetic modulation.

Heart rate variability and autonomic nervous system imbalance: Potential biomarkers and detectable hallmarks of aging and inflammaging

The most cutting-edge issue in the research on aging is the quest for biomarkers that transcend molecular and cellular domains to encompass organismal-level implications. We recently hypothesized the role of Autonomic Nervous System (ANS) imbalance in this context. Studies on ANS functions during aging highlighted an imbalance towards heightened sympathetic nervous system (SNS) activity, instigating a proinflammatory milieu, and attenuated parasympathetic nervous system (PNS) function, which exerts anti-inflammatory effects via the cholinergic anti-inflammatory pathway (CAP) and suppression of the hypothalamic-pituitary-adrenal (HPA) axis. This scenario strongly suggests that ANS imbalance can fuel inflammaging, now recognized as one of the most relevant risk factors for age-related disease development. Recent recommendations have increasingly highlighted the need for actionable strategies to improve the quality of life for older adults by identifying biomarkers that can be easily measured, even in asymptomatic individuals. We advocate for considering ANS imbalance as a biomarker of aging and inflammaging. Measures of ANS imbalance, such as heart rate variability (HRV), are relatively affordable, non-invasive, and cost-effective, making this hallmark easily diagnosable. HRV gains renewed significance within the aging research landscape, offering a tangible link between pathophysiological perturbations and age-related health outcomes.

Autonomic reactivity to mental stress is associated with cardiovascular mortality

Aims

The mechanisms linking acute psychological stress to cardiovascular disease (CVD) mortality are incompletely understood. We studied the relationship of electrocardiographic measures of autonomic dysfunction during acute mental stress provocation and CVD death.

Methods and results

In a pooled cohort of 765 participants with stable CVD from two related studies, we collected Holter data during standardized laboratory-based mental stress testing with a speech task and followed them for events. We assessed autonomic function using low-frequency (LF) heart rate variability (HRV) in 5-min intervals before, during, and after stress induction, and specifically examined changes from rest to stress. We employed cause-specific survival models to examine its association with CVD and all-cause mortality, controlling for demographic and CVD risk factors. The mean (SD) age was 58 (10) years, 35% were women, and 44% self-identified as Black. After a median follow-up of 5.6 years, 37 (5%) died from CVD causes. A stress-induced LF HRV decrease (67% of sample), vs. increase, was associated with a hazard ratio (HR) of 3.48 (95% confidence interval-3.25, 3.73) for CVD mortality. Low rest LF HRV (bottom quartile) was also independently associated with CVD mortality, HR = 1.75 (1.58, 1.94), vs. normal rest LF HRV (upper three quartiles). The combination of stress-induced LF HRV decrease and low rest LF HRV was associated with HR = 5.73 (5.33, 6.15) vs. the normal stress/rest LF HRV reference. We found similar results with HF HRV.

Conclusion

Stress-induced LF HRV decrease and low rest LF HRV are both independently and additively associated with a higher CVD mortality risk. Additional research is needed to assess whether targeting autonomic dysfunction may improve CVD outcomes.

Relationship between autonomic nervous function and brain functions such as memory and attention

This study aimed to evaluate the relationship between autonomic nervous function (ANF) and cognitive abilities, such as memory and attention, using the Kana pick-out test (KPT). The participants were 11 female college students aged 21 years old. Each participant completed the KPT ten times, during which their ANF was assessed via heart rate variability analysis. During the KPT, participants circled Japanese vowels in a 400-character story written in hiragana. We measured attention using the KPT score and assessed memory using a memory score based on ten descriptive questions about the story. Statistical analysis revealed a significant positive correlation between higher KPT and memory scores, indicating a link between memory and attention. The parasympathetic sinus modulation marker, high-frequency component power (HF), decreased during the kana-picking task (Interval B) and recovered during the subsequent content verification task (Interval C). In Interval A (before the kana-picking task), the HF showed a positive correlation with both the KPT and memory scores. Additionally, a positive correlation was observed between HF and memory scores during interval B. Other autonomic nervous indices, including low-frequency component power (LF), total power (TP), and LF/HF ratio, also showed significant correlations with KPT and memory scores. Our findings strongly suggest that ANF is intricately connected to cognitive functions, such as memory and attention. This indicates that monitoring ANF could provide a novel methodology for assessing learning and occupational efficiency.

Heart Rate Variability and Interoception in Periodic Limb Movements in Sleep: Interference with Psychiatric Disorders?

Periodic limb movements in sleep (PLMS) are a prevalent disorder characterized by rhythmic, involuntary movements of the lower limbs, such as dorsiflexion of the ankle and extension of the big toe, occurring in periodic intervals during sleep. These movements are often linked to disrupted autonomic nervous system (ANS) activity and altered interoception. Interoception involves perceiving internal bodily states, like heartbeat, breathing, hunger, and temperature, and plays a crucial role in maintaining homeostasis and the mind-body connection. This review explores the complex relationships between PLMS, heart rate variability (HRV), ANS dysregulation, and their impact on psychiatric disorders. By synthesizing the existing literature, it provides insights into how ANS dysregulation and altered interoceptive processes, alongside PLMS, contribute to psychiatric conditions. The review highlights the potential for integrated diagnostic and therapeutic approaches and presents a cause-and-effect model illustrating the mutual influence of psychiatric disorders, ANS dysregulation, PLMS, and interoception.

Reduced heart rate variability is related to fluctuations in psychological stress levels in daily life

Laboratory-based studies have shown that psychological stress caused by response to various stressors triggers acute changes in the cardiovascular system. A better understanding is needed of the emerging evidence on temporal associations between psychological stress and cardiovascular responses in natural settings. This study examined the association of psychological stress and heart rate variability (HRV) in daily life, at high resolution over 2 weeks, taking the effect of physical activity into account. Participants (n = 34) completed ecological momentary assessments (EMA) 6 times per day, reporting levels of perceived stress, low-arousal negative affect (LNA), and high-arousal negative affect. Chest-mounted heart-rate monitors were worn to assess HRV. Multilevel models were used to examine the association between psychological stress levels and preceding/subsequent HRV. Reduced time domain HRV measures (mean and standard deviation of R-wave to R-wave intervals) during the prior hour predicted higher levels of perceived stress. Frequency domain HRV measures higher low to high frequency (LF/HF) and lower HF to total power (HF nu) ratios during the preceding 10 min predicted higher perceived stress levels, suggesting the dominance of sympathetic nervous system activity. EMA reports of higher perceived stress levels were associated with reduced time domain HRV measures during the following 10 min. On the other hand, higher LNA were related to increased HRV measures, such as lower LF/HF and higher HF nu during the following hour. The dynamic associations observed may have therapeutic implications for 'just-in-time' interventions in the management of daily stress and cardiovascular health.

Orienteering Is More than Just Running! Acute Effect of Competitive Pressure on Autonomic Cardiac Activity among Elite Orienteering Athletes

Background and Objectives: Orienteering is a sport characterized by high physical exertion and intense mental demands, which increase susceptibility to errors. Understanding the impact of such errors on psychophysiological responses, particularly on heart rate variability (HRV), is essential. This study aimed to investigate the relationship between psychophysiological indicators and checkpoint errors made by elite orienteers during official competition. Materials and Methods: Fifty-three orienteers participated in this study, and their performance was continuously monitored and recorded by using a global positioning system (GPS) and HRV data. Errors made during the orienteering events were identified and analyzed. HRV data were examined in three temporal segments: before, during, and after the identified and standardized errors. Results: The analyses indicated that errors significantly impacted HRV indices across multiple domains: the time domain, frequency domain, and nonlinear domain. Additionally, a significant effect of sex on the normalized the root mean square of successive differences (r-MSSD) before and after the error was observed. Conclusions: The findings of this study underscore the significant impact of errors made by orienteers on cardiovascular responses, as evidenced by measurable alterations in HRV metrics. Cardiovascular activity, represented by the HRV, can provide useful information for coaches and sport psychologists to adopt effective training programs for athletes.

Influence of autonomic nervous dysfunction on eating during hemodialysis sessions: An observational study

Although some studies have indicated that eating during hemodialysis may induce hypotension and cardiovascular events, some patients still consume food during their treatment. This prospective study was conducted to determine whether the need to eat during hemodialysis treatment was related to abnormal glucose metabolism and autonomic nerve dysfunction. Seventy patients were enrolled in this study, and their demographic features and various laboratory parameters were analyzed. At each routine hemodialysis visit, predialysis, intradialysis, and postdialysis blood pressure measurements were systematically conducted. A 24-hour ambulatory electrocardiogram (ECG) was performed during the hemodialysis interval, and heart rate variability (HRV) values were calculated. Additionally, whether the patients ate during the hemodialysis treatments was recorded. Another 20 people who underwent physical examinations during the same period and were matched for sex and age were included in the control group. The HRV values of the hemodialysis patients were generally lower than those of the control group. Univariate analysis revealed significant differences in sex, age, calcium antagonist use, blood calcium levels, insulin levels, diastolic blood pressure (DBP) measurements, and HRV indices between hemodialysis patients who ate and those who did not eat during hemodialysis (P < .05), whereas there were no significant differences in diabetes status or in the hemoglobin, albumin, blood glucose and C-peptide levels (P > .05). Multivariate analysis revealed that low values for very low frequency (VLF) and postdialysis DBP were risk factors for fasting intolerance during hemodialysis treatments. Autonomic dysfunction may affect whether hemodialysis patients tolerate fasting during dialysis. VLF evaluation may provide information that can be used to develop a more reasonable intradialytic nutritional supplementation method.

Endogenous orexin and hyperacute autonomic responses after resuscitation in a preclinical model of cardiac arrest

Objectives

The study of autonomic responses to cardiac arrest (CA) resuscitation deserves attention due to the impact of autonomic function on survival and arousal. Orexins are known to modulate autonomic function, but the role of endogenous orexin in hyperacute recovery of autonomic function post-resuscitation is not well understood. We hypothesized that endogenous orexin facilitates hyperacute cardiovascular sympathetic activity post-resuscitation, and this response could be attenuated by suvorexant, a dual orexin receptor antagonist.

Methods

A well-established 7-min asphyxial CA rat model was studied. Heart rate (HR) and blood pressure were monitored from baseline to 90-min post-resuscitation. Autonomic function was evaluated by spectral analysis of HR variability, whereby the ratio of low- and high-frequency components (LF/HF ratio) represents the balance between sympathetic/parasympathetic activities. Plasma orexin-A levels and orexin receptors immunoreactivity in the rostral ventrolateral medulla (RVLM), the key central region for regulating sympathetic output, were measured post-resuscitation. Neurological outcome was assessed via neurologic-deficit score at 4-h post-resuscitation.

Key results

A significant increase in HR was found over 25-40 min post-resuscitation (p < 0.01 vs. baseline), which was attenuated by suvorexant significantly (p < 0.05). Increased HR (from 15-to 25-min post-resuscitation) was correlated with better neurological outcomes (rs = 0.827, p = 0.005). There was no evident increase in mean arterial pressure over 25-40 min post-resuscitation, while systolic pressure was reduced greatly by suvorexant (p < 0.05). The LF/HF ratio was higher in animals with favorable outcomes than in animals injected with suvorexant over 30-40 min post-resuscitation (p < 0.05). Plasma orexin-A levels elevated at 15-min and peaked at 30-min post-resuscitation (p < 0.01 vs. baseline). Activated orexin receptors-immunoreactive neurons were found co-stained with tyrosine hydroxylase-immunopositive cells in the RVLM at 2-h post-resuscitation.

Conclusion

Together, increased HR and elevated LF/HF ratio indicative of sympathetic arousal during a critical window (25-40 min) post-resuscitation are observed in animals with favorable outcomes. The orexin system appears to facilitate this hyperacute autonomic response post-CA.

Frequency-Domain Features and Low-Frequency Synchronization of Photoplethysmographic Waveform Variability and Heart Rate Variability with Increasing Severity of Cardiovascular Diseases

Objective-Heart rate variability (HRV) and photoplethysmographic waveform variability (PPGV) are available approaches for assessing the state of cardiovascular autonomic regulation. The goal of our study was to compare the frequency-domain features and low-frequency (LF) synchronization of the PPGV and HRV with increasing severity of cardiovascular diseases. Methods-Our study included 998 electrocardiogram (ECG) and finger photoplethysmogram (PPG) recordings from subjects, classified into five categories: 53 recordings from healthy subjects, aged 28.1 ± 6.2 years, 536 recordings from patients with hypertension (HTN), 49.0 ± 8.8 years old, 185 recordings from individuals with stable coronary artery disease (CAD) (63.9 ± 9.3 years old), 104 recordings from patients with myocardial infarction (MI) that occurred three months prior to the recordings (PMI) (65.1 ± 11.0 years old), and 120 recordings from study subjects with acute myocardial infarction (AMI) (64.7 ± 11.5 years old). Spectral analyses of the HRV and PPGV were carried out, along with an assessment of the synchronization strength between LF oscillations of the HRV and of PPGV (synchronization index). Results-Changes in all frequency-domain indices and the synchronization index were observed along the following gradient: healthy subjects → patients with HTN → patients with CAD → patients with PMI → patients with AMI. Similar frequency-domain indices of the PPGV and HRV show little relationship with each other. Conclusions-The frequency-domain indices of the PPGV are highly sensitive to the development of any cardiovascular disease and, therefore, are superior to the HRV indices in this regard. The S index is an independent parameter from the frequency-domain indices.

Revealing alterations in heart rate fluctuations during the progression of Chagas disease

Introduction

The heart rate variability (HRV) continually evolves throughout life, reflecting modifications in the architecture of the sinoatrial node (SAN) and in the regulation of heart rate by the autonomic nervous system (ANS). Both can be considerably affected by Chagas disease, causing important changes in the complex nature of HRV. We aim to evaluate the ability of an index based on the false nearest neighbors method (FN10) to reflect these changes during disease progression.

Methods

We perform a retrospective, descriptive, and cross-sectional study analyzing HRV time series of participants with Chagas disease. We determine the dependence of FN10 on age and sex in a healthy population, and then evaluate FN10 in individuals with Chagas disease.

Results and discussion

In the healthy population, FN10 has a scaling behavior with age, which is independent of sex. In Chagas disease, some individuals show FN10 values significantly above those seen in the healthy population. We relate the findings to the pathophysiological mechanisms that determine the progression of the disease. The results indicate that FN10 may be a candidate prognostic biomarker for heart disease.

Cardiac autonomic responses to transrectal examination and parlor milking of lame and nonlame dairy cows

We studied the changes in the heart rate variability of lame and nonlame dairy cows in response to transrectal examination (TRE) and parlor milking. We hypothesized that lame cows experience greater stress, manifested in heart rate variability parameters, that serves as an argument to promote more caution in the everyday handling of lame animals. In the study, we selected 55 lame (with lesions on at least one hoof, otherwise clinically healthy, with locomotion scores 4 and 5 of 5-point scores) and 55 nonlame (clinically healthy, with locomotion scores 1 and 2 of 5-point scores) cows. The heart rate, root mean square of successive beat-to-beat intervals (RMSSD), the normalized unit of the high-frequency (HF) component of the spectral analysis and Poincaré measures (SD2/SD1) were compared between lame and nonlame cows during 5 distinct stages of TRE and 7 stages of parlor milking. Heart rate, RMSSD, and SD2/SD1 showed similar patterns during TRE and milking, while HF remained fairly constant during the studied phases. No distinct RMSSD, HF, or SD2/SD1 changes were observed during the phases expected to elicit a stress response. Between-group differences were only observed in terms of HF. Baseline HF was higher in lame cows than in nonlame ones, and such a difference in direction was observed throughout the whole procedure. During milking and TRE, the heart rate, RMSSD, and SD2/SD1 values showed temporal changes in times of higher physical activity: moving to and waiting in the holding pen and moving into the milking stalls in the parlor for preparation in both lame and nonlame cows. The differences in baseline HF (normalized units) between lame and nonlame cows cannot be fully explained based on available information. The lack of a distinct, stress-related change in heart rate variability parameters in both groups can originate in methodological challenges inherent in animal heart rate variability measurements in field conditions.

Publication guidelines for human heart rate and heart rate variability studies in psychophysiology-Part 1: Physiological underpinnings and foundations of measurement

This Committee Report provides methodological, interpretive, and reporting guidance for researchers who use measures of heart rate (HR) and heart rate variability (HRV) in psychophysiological research. We provide brief summaries of best practices in measuring HR and HRV via electrocardiographic and photoplethysmographic signals in laboratory, field (ambulatory), and brain-imaging contexts to address research questions incorporating measures of HR and HRV. The Report emphasizes evidence for the strengths and weaknesses of different recording and derivation methods for measures of HR and HRV. Along with this guidance, the Report reviews what is known about the origin of the heartbeat and its neural control, including factors that produce and influence HRV metrics. The Report concludes with checklists to guide authors in study design and analysis considerations, as well as guidance on the reporting of key methodological details and characteristics of the samples under study. It is expected that rigorous and transparent recording and reporting of HR and HRV measures will strengthen inferences across the many applications of these metrics in psychophysiology. The prior Committee Reports on HR and HRV are several decades old. Since their appearance, technologies for human cardiac and vascular monitoring in laboratory and daily life (i.e., ambulatory) contexts have greatly expanded. This Committee Report was prepared for the Society for Psychophysiological Research to provide updated methodological and interpretive guidance, as well as to summarize best practices for reporting HR and HRV studies in humans.

Heart Rate Variability during Nostril-Regulated Yoga Breathing: A Randomized Crossover Study

Background

Previous studies of nostril-regulated yoga breathing have focused on unilateral breathing with both inspiration and expiration through a specified nostril. However, traditionally described yoga breathing involves inspiration through one nostril and expiration through the other, called suryabhedan pranayama (SBP) (right nostril inspiration) and chandrabhedan pranayama (CBP) (left nostril inspiration). The effects of these practices were investigated here.

Methods

Forty-seven healthy male participants (group mean age ± standard deviation [SD]; 26.34 ± 6.38 years) with prior experience of yoga breathing (group mean age ± SD; 43.64 ± 32.84 months) were randomly assigned to four sessions on separate days: (i) SBP, (ii) CBP, (iii) Breath awareness, and (iv) Quiet rest. The heart rate variability (HRV) and breath rate were recorded pre, during, and post each practice.

Results

There was a significant increase in low frequency (LF) power and SD of NN intervals during SBP and CBP in comparison to the respective preceding (P < 0.05; repeated measures analyses of variance with Bonferroni adjusted post hoc analysis), while LF increased post-CBP alone. During both interventions, there were significant reductions in respiration rate.

Conclusion

The changes in HRV suggest common rather than distinct changes in SBP and CBP suggestive of respiration-related increased cardiac parasympathetic activity. The involvement of both nostrils in SBP and CBP may have contributed to the comparable effects of the two practices.

Heart rate variability modulates memory function in a virtual task

Heart rate variability (HRV) is considered one of the most relevant indicators of physical well-being and relevant biomarker for preventing cardiovascular risks. More recently, a growing amount of research has tracked an association between HRV and cognitive functions (i.e., attention). Research is still scarce on spatial orientation, a basic capability in our daily lives. It is also an important indicator of memory performance, and its malfunctioning working as an early sign of dementia. In this study, a total of 43 female students (M Age = 18.76; SD = 2.02) were measured in their lnRMSSD using the photoplethysmography technique with the Welltory smartphone app. They were also tested in their spatial memory with The Boxes Room, a virtual navigation test. Measures of physical activity were obtained with the International Physical Activity Questionnaire (IPAQ). Correlation analyses and repeated measures ANOVA were performed, comparing participants with high / low lnRMSSD in their spatial performance. Results showed that, at an equal level of physical activity, participants with a higher lnRMSSD were more effective in the early trials of The Boxes Room, being more precise in estimating the correct position of the stimuli. Moreover, a subsequent simple linear regression showed that a higher lnRMSSD was related to a smaller number of errors at the beginning of the spatial task. Overly, these results outline the relationship between HRV and navigation performance in early stages of processing, where the environment is still unknown and the situation is more demanding.

Preventive effect of one-session brief focused attention meditation on state fatigue: Resting state functional magnetic resonance imaging study

INTRODUCTION

The extended practice of meditation may reduce the influence of state fatigue by changing neurocognitive processing. However, little is known about the preventive effects of one-session brief focused attention meditation (FAM) on state fatigue in healthy participants or its potential neural mechanisms. This study examined the preventive effects of one-session brief FAM on state fatigue and its neural correlates using resting-state functional MRI (rsfMRI) measurements.

METHODS

We randomly divided 56 meditation-naïve participants into FAM and control groups. After the first rsfMRI scan, each group performed a 10-minute each condition while wearing a functional near-infrared spectroscopy (fNIRS) device for assessing brain activity. Subsequently, following a second rsfMRI scan, the participants completed a fatigue-inducing task (a Go/NoGo task) for 60 min. We evaluated the temporal changes in the Go/NoGo task performance of participants as an indicator of state fatigue. We then calculated changes in the resting-state functional connectivity (rsFC) of the rsfMRI from before to after each condition and compared them between groups. We also evaluated neural correlates between the changes in rsFC and state fatigue.

RESULTS AND DISCUSSION

The fNIRS measurements indicated differences in brain activity during each condition between the FAM and control groups, showing decreased medial prefrontal cortex activity and decreased functional connectivity between the medial prefrontal cortex and middle frontal gyrus. The control group exhibited a decrement in Go/NoGo task performance over time, whereas the FAM group did not. These results, thus, suggested that FAM could prevent state fatigue. Compared with the control group, the rsFC analysis revealed a significant increase in the connectivity between the left dorsomedial prefrontal cortex and right superior parietal lobule in the FAM group, suggesting a modification of attention regulation by cognitive effort. In the control group, increased connectivity was observed between the bilateral posterior cingulate cortex and left inferior occipital gyrus, which might be associated with poor attention regulation and reduced higher-order cognitive function. Additionally, the change in the rsFC of the control group was related to state fatigue.

CONCLUSION

Our findings suggested that one session of 10-minute FAM could prevent behavioral state fatigue by employing cognitive effort to modify attention regulation as well as suppressing poor attention regulation and reduced higher-order cognitive function.

Effects of Concurrent Training on Resuscitation and Cognitive Performance in Paramedics-A Pilot Study

Paramedics work under physically and cognitively demanding conditions to provide emergency care. As physical fitness could positively impact the quality of patient care, we investigated within a pilot study whether concurrent training (CT) affects work-related performance parameters in paramedics. At baseline (T1), 16 paramedics performed cardiopulmonary resuscitation whereby resuscitation performance (RP; total resuscitation quality, compressions with correct frequency, and correct ventilation), cognitive performance (CP; reaction time, divided attention, and working memory), and heart rate variability (HRV) were assessed (pre-exertion). Then, participants climbed seven floors carrying 20 kg of gear before completing the same assessments again (post-exertion). The baseline testing was followed by a CT intervention (12 weeks, three sessions/week). After the intervention (T2), the two-stage testing was repeated. We analyzed whether the pre-exertion and post-exertion values, as well as the difference between the pre-exertion and post-exertion values, changed from T1 to T2. Nine paramedics (male: N = 7; age = 26.3 (SD = 8.17) years) took part in the study. The comparison of the pre-exertion values showed significantly better reaction times (p = 0.001) and divided attention (p = 0.02) and a trend toward greater working memory and RP parameters at T2. Regarding the post-exertion values, significant improvements in working memory (p = 0.03) and a trend toward improved reaction time, divided attention, and RP occurred at T2. The difference between the pre- and post-exertion values did not change for any parameter from T1 to T2. HRV decreased significantly from pre- to post-exertion (T1: p = 0.01, T2: p = 0.01). These results indicate that CT is a promising training concept to improve RP and CP in paramedics and should therefore be investigated further to increase patient care quality.

The contribution of granger causality analysis to our understanding of cardiovascular homeostasis: from cardiovascular and respiratory interactions to central autonomic network control

Homeostatic regulation plays a fundamental role in maintenance of multicellular life. At different scales and in different biological systems, this principle allows a better understanding of biological organization. Consequently, a growing interest in studying cause-effect relations between physiological systems has emerged, such as in the fields of cardiovascular and cardiorespiratory regulations. For this, mathematical approaches such as Granger causality (GC) were applied to the field of cardiovascular physiology in the last 20 years, overcoming the limitations of previous approaches and offering new perspectives in understanding cardiac, vascular and respiratory homeostatic interactions. In clinical practice, continuous recording of clinical data of hospitalized patients or by telemetry has opened new applicability for these approaches with potential early diagnostic and prognostic information. In this review, we describe a theoretical background of approaches based on linear GC in time and frequency domains applied to detect couplings between time series of RR intervals, blood pressure and respiration. Interestingly, these tools help in understanding the contribution of homeostatic negative feedback and the anticipatory feedforward mechanisms in homeostatic cardiovascular and cardiorespiratory controls. We also describe experimental and clinical results based on these mathematical tools, consolidating previous experimental and clinical evidence on the coupling in cardiovascular and cardiorespiratory studies. Finally, we propose perspectives allowing to complete the understanding of these interactions between cardiovascular and cardiorespiratory systems, as well as the interplay between brain and cardiac, and vascular and respiratory systems, offering a high integrative view of cardiovascular and cardiorespiratory homeostatic regulation.

Short-term heart rate variability: A potential approach to frailty assessment in older adults

Objectives

This study aimed to evaluate cardiac autonomic modulation using short-term heart rate variability (HRV) and compare it among frailty statuses in older Indian adults.

Methods

A total of 210 subjects aged 60 years and above were recruited into three groups: frail (n = 70), pre-frail (n = 70), and non-frail (n = 70) from the outpatient department of Geriatric Medicine at a tertiary care hospital in India. Frailty status was assessed using the Rockwood frailty index (FI) criteria. HRV was derived from a 5-min ECG recording of standard limb leads and assessed using time domain, frequency domain, and nonlinear analysis of cardiac interval variability.

Results

The HRV parameters indicative of parasympathetic modulation such as SDNN, SDSD, rMSSD, NN50, pNN50, absolute HF power, and SD1 were significantly lower in frail subjects compared with both pre-frail and non-frail subjects (P < 0.05). Absolute LF power and SD2 were also lower in frail subjects compared with pre-frail and non-frail subjects (P < 0.05). Measures of sympatho-vagal balance (LF/HF and SD1/SD2 ratios) did not show statistical significance. The FI demonstrated negative correlations with all HRV parameters.

Conclusions

Frail individuals exhibit decreased sympathetic and parasympathetic modulation compared with pre-frail and non-frail individuals, although maintaining a balanced sympatho-vagal state. Furthermore, autonomic modulation declines progressively with increasing frailty.

Improving Prefrontal Oxygenation and Cardiac Autonomic Activity Following Meditation: A Functional Near-Infrared Spectroscopy (fNIRS) Study

OBJECTIVE

The empirical evidence explicitly demonstrates that meditation practice enhances both brain functions and mental well-being. A meditative relaxation approach called the mind sound resonance technique (MSRT) has shown promising effects on children, adolescents, and people with psychological illnesses. This study aimed to investigate the effects of MSRT practice on brain hemodynamics, heart rate variability (HRV), mindfulness, and anxiety levels in college students.

METHODS

Fifty volunteers in all genders (females, n = 30; males, n = 20) aged between 19 and 30 years were chosen from an educational institute and allocated into two groups, i.e., MSRT (n = 25) and supine rest (SR; n = 25). Enrolled participants were measured cerebral hemodynamics and HRV before, during, and after the MSRT or SR practice. The self-reported assessments including state anxiety and mindfulness were assessed before and after the intervention.

RESULTS

The results demonstrated that practicing MSRT significantly improved oxygenation (p < 0.05) in the right prefrontal cortex (PFC) and increased low-frequency (LF) (p < 0.05) and decreased high-frequency (HF) (p < 0.05) component of HRV when compared to the baseline. The between-group analysis showed a significant difference between MSRT and SR in the standard deviation of the normal-to-normal (SDNN) (p < 0.05) component of HRV.

CONCLUSION

These crumbs of evidence imply that MSRT sessions may foster the development of anxiety-related coping skills by elevating mindfulness, promoting PFC oxygenation, and modulating HRV in MSRT practitioners.

Reliability of an "At-Home" Method for Monitoring Resting and Reactive Autonomic Nervous System Activity in Children: A Pilot Study

BACKGROUND

Heart rate variability (HRV), an index of the functional status of the autonomic nervous system (ANS), provides an opportunity for early detection of ANS dysfunction. Lower resting, vagally related HRV parameters are associated with increased risk of physical and mental illness. External factors influencing the ANS, such as the testing environment, may impact the interpretation of HRV. This study's main aim was to determine the reliability of HRV resting and reactivity tests performed at home with children aged 4-9 years.

METHODS

Fourteen healthy children (female n = 8) aged 6.8 ± 1.5 years participated. Two HRV tests were performed at home via online supervision 7 days apart using a Polar H10 heart rate monitor. The absolute and relative reliability of the pre-exercise resting (5 min) and sub-maximal exercise step test recovery (4 × 30 s segments) HRV time and frequency domains were calculated.

RESULTS

The Pearson correlation coefficients for day 1 versus day 7 for the vagal activity HRV domains (RMSSD log) at rest and in the first 30 s and 30-60 s of recovery indicated good-to-excellent relative reliability (r > 0.8, p < 0.01). Absolute reliability was moderate for the resting RMSSD log, with a coefficient of variation (CV) of 5.2% (90% CI: 3.9, 7.8%), high for the first 30 s of standing recovery, with a CV of 10.7% (90% CI: 8.2, 15.7%), and moderate for 30-60 s of recovery, with a CV of 8.7% (90% CI: 6.6, 12.9%).

CONCLUSIONS

The findings of this pilot study indicate that the resting and exercise recovery HRV measures of vagal activity can be measured reliably at home in children. This represents a novel "at-home" protocol for monitoring ANS health and development in children.

Vagal predominance correlates with mood state changes of winter-over expeditioners during prolonged Antarctic residence

OBJECTIVE

Winter-over expeditioners in Antarctica are challenged by various environmental and psycho-social stress factors, which may induce psychophysiological changes. The autonomic nervous system (ANS) plays a crucial role in the adaptation process under stress. However, the relationship between ANS activity and the mood states of expeditioners remains largely unexplored. This study aims to uncover the pattern of ANS adjustment under extreme Antarctic environments and provide new insights into the correlations between ANS activity and mood state changes, which may provide scientific data for medical interventions.

METHODS

Fourteen expeditioners at Zhongshan Station participated in this study. The study was conducted during four representative periods: pre-Antarctica, Antarctica-1 (pre-winter), Antarctica-2 (winter), and Antarctica-3 (summer). The heart rate variability (HRV) of the expeditioners was continuously measured for 24 hours to evaluate ANS activity. Plasma levels of catecholamines were tested by ELISA. Mood states were assessed by the Profile of Mood States (POMS) scale.

RESULTS

HRV analysis showed a disturbance of ANS during winter and summer periods. For frequency domain parameters, very low frequency (VLF), low frequency (LF), high frequency (HF), and total power (TP) significantly increased during the second half of the mission. Especially, LF/HF ratio decreased during summer, indicating the predominance of vagal tone. Results of the time domain analysis showed increased heart rate variability during the austral winter and summer. Plasma epinephrine (E) significantly increased during residence in Antarctica. Compared with pre-Antarctica, the vigor, depression, and anger scores of the expeditioners decreased significantly during the austral summer. Notably, the depression score showed a moderate positive correlation with LF/HF, while weak negative correlations with other HRV indicators, including TP, VLF, and LF. Anger score showed a moderate positive correlation with LF/HF and weak negative correlations with the average normal-to-normal (NN) interval, and the root mean square of differences between adjacent RR intervals (RMSSD). Plasma E level weakly correlated with the average NN interval.

CONCLUSION

Prolonged residence in Antarctica increased the ANS activities and shifted the cardiac autonomic modulation towards vagal predominance. The alteration of HRV correlated with mood states and plasma epinephrine levels.

Effects of different winter paddock management of Thoroughbred weanlings and yearlings in the cold region of Japan on physiological function, endocrine function and growth

Effects of different winter paddock management of Thoroughbred weanlings and yearlings in Hokkaido, Japan, which is extremely cold in winter, on physiological function, endocrine function and growth were investigated. They were divided into two groups; those kept outdoors for 22 hr in the paddock (22hr group) and those kept outdoors for 7 hr in daytime with walking exercise for 1 hr using the horse-walker (7hr+W group), and the changes in daily distance travelled, body temperature (BT), heart rate (HR), HR variability (HRV), endocrine function and growth parameters were compared between the two groups from November at the year of birth to January at 1 year of age. The 7hr+W group could travel almost the same distance as the 22hr group by using the horse-walker. The 22hr group had a lower rate of increase in body weight than the 7hr+W group in January. In addition, lower in BT and HR were observed, and HRV analysis showed an increase in high frequency power spectral density, indicating that parasympathetic nervous activity was dominant. And also, changes in circulating cortisol and thyroxine were not observed despite cold environment. On the other hand, the 7hr+W group had higher prolactin and insulin like growth factor than the 22hr group in January, and cortisol and thyroxine were also increased. Physiological and endocrinological findings from the present study indicate that the management of the 7hr+W group is effective in promoting growth and maintaining metabolism during the winter season.

The influence of oral contraceptives on the exercise pressor reflex in the upper and lower body

Previous research has demonstrated that oral contraceptive (OC) users have enhanced cardiorespiratory responses to arm metaboreflex activation (i.e., postexercise circulatory occlusion, PECO) and attenuated pressor responses to leg passive movement (PM) compared to non-OC users (NOC). We investigated the cardiorespiratory responses to arm or leg metaboreflex and mechanoreflex activation in 32 women (OC, n = 16; NOC, n = 16) performing four trials: 40% handgrip or 80% plantarflexion followed by PECO and arm or leg PM. OC and NOC increased mean arterial pressure (MAP) similarly during handgrip, plantarflexion and arm/leg PECO compared to baseline. Despite increased ventilation (VE) during exercise, none of the women exhibited higher VE during arm or leg PECO. OC and NOC similarly increased MAP and VE during arm or leg PM compared to baseline. Therefore, OC and NOC were similar across pressor and ventilatory responses to arm or leg metaboreflex and mechanoreflex activation. However, some differences due to OC may have been masked by disparities in muscle strength. Since women increase VE during exercise, we suggest that while women do not display a ventilatory response to metaboreflex activation (perhaps due to not reaching a theoretical metabolite threshold to stimulate VE), the mechanoreflex may drive VE during exercise in women.

RSA instability in mothers of preschoolers and adolescents is related to observations of supportive parenting behaviors

Respiratory sinus arrhythmia (RSA; a measure of respiratory modulation of vagal control of heart rate) is a dynamic process. For mothers, RSA functioning has been associated with depressive symptoms and coincides with supportive parenting. However, research has largely focused on RSA suppression (i.e., difference score from rest to stress task). The present study examined depressive symptoms and supportive parenting with RSA instability-a dynamic measure of the magnitude of RSA change across a task. In two samples of mothers (N = 210), one with preschoolers (Study 1: n = 108, Mage = 30.68 years, SD = 6.06, 47.0% Black, 43.0% White) and one with adolescents (Study 2: n = 102, Mage = 35.51, SD = 6.51, 75.2% Black), RSA instability was calculated during an interaction task. In both studies, instrumental supportive parenting behaviors were negatively related to RSA instability. Findings provide preliminary support for RSA instability as an indicator of physiological dysregulation for mothers.

Holter study of heart rate variability in children and adolescents with long QT syndrome

OBJECTIVES

This study aimed to retrospectively assess cardiac autonomic activity in children with LQTS, considering genotype, symptoms, sex, age, and beta-blocker therapy (BB) and compare it to healthy controls.

METHODS

Heart rate variability (HRV), using power spectrum analysis, was analyzed in 575 Holter recordings from 116 children with LQTS and in 69 healthy children. The data were categorized into four age-groups and four heart rate (HR) ranges.

RESULTS

In LQT1 and LQT2, increasing HR corresponded to significantly lower low (LF) and high frequency (HF) compared to controls. Total power (PTOT) was lower in all LQT1 age-groups compared to controls at HR 120-140 bpm (1-15 years: p < .01; 15-18 years: p = .03). At HR 80-100, LQT1 patients aged 1-10 years had lower HF than LQT2 patients (1-5 years: p = .05; 5-10 years: p = .02), and LQT2 patients aged 15-18 years had lower HF than LQT1 patients (p < .01). Symptomatic patients aged 10-15 years had lower PTOT at HR 100-120 bpm than asymptomatic patients (p = .04). LQT1 girls aged 10-15 and 15-18 years had a lower PTOT (10-15 years: p = .04; 15-18 years: p = .02) than boys.

CONCLUSION

This study shows a correlation between HR and changes in HRV parameters. At higher HRs, LQTS patients generally had lower HRV values than controls, suggesting an abnormal autonomic response. These results may strengthen the link between physical activity and arrhythmias in LQTS.