Root Mean Square Of Successive Differences Research Articles

Reduced heart rate variability during mania in a repeated naturalistic observational study.

Bipolar disorder (BD) is a chronic recurrent mood disorder associated with autonomic nervous system (ANS) dysfunction, indexed by heart rate variability (HRV). Changes in HRV between mood states are sparsely studied longitudinally. We aimed to compare HRV of hospitalized manic individuals with their own euthymic selves in a naturalistic observational study. 34 individuals were included, of which 16 were lost to follow-up. Ultimately 15 patients provided reliable heart rate data in both a manic and euthymic state, using photoplethysmography (PPG) sensor wristbands overnight. We calculated HRV measures Root Mean Square of Successive Differences (RMSSD), High-frequency (HF: 0.15-0.40 Hz), Low-frequency (LF: 0.40-0.15 Hz), Very low-frequency (VLF: 0.0033-0.04 Hz), Total power and Sample Entropy in 5-min night-time resting samples. We compared HRV measures by mood state within individuals using paired t-tests and linear regression to control for age and sex. HRV was lower in the manic state when compared to the euthymic state for all HRV metrics (p ≤ 0.02), with large to medium effect sizes (g = 1.24 to 0.65). HRV changes were not significantly affected by age or sex. This longitudinal study provides evidence of lower HRV in manic states compared to euthymia, indicating an association between ANS dysregulation and changes in bipolar mood state. This corroborates previous cross-sectional studies, although the association may be less clear or reversed in hypomanic states. Further investigation in larger longitudinal samples is warranted.

The Influence ofPhysical andMental Health Mediators onthe Relationship Between Combat-Related Traumatic Injury andUltra-Short-Term Heart Rate Variability ina U.K. Military Cohort: A Structural EquationModeling Approach.

Combat-related traumatic injury (CRTI) adversely affects heart rate variability (HRV). The mediating effect of mental and physical health factors on the relationship between CRTI, its severity and HRV has not been previously studied and investigated. A cross-sectional mediation analysis of the ArmeD SerVices TrAuma and RehabilitatioN OutComE (ADVANCE) prospective cohort study was performed. The sample consisted of injured and uninjured British male servicemen who were frequency-matched based on their age, rank, role-in-theater, and deployment to Afghanistan (2003-2014). CRTI and injury severity (the New Injury Severity Scores [NISS] [NISS < 25 and NISS ≥ 25]) were included as exposure variables. HRV was quantified using the root mean square of successive differences (RMSSD) obtained using pulse waveform analysis. Depression and anxiety mediators were quantified using the Patient Health Questionnaire and Generalized Anxiety Disorder, respectively. Body mass index and the 6-minute walk test (6MWT) represented physical health measures. Two mediation pathways between exposure and outcome variables were examined in comparison with the uninjured group using structural equation modeling. Of 862 servicemen, 428 were injured and 434 were uninjured with the mean age at assessment of 33.9 ± 5.4 (range 23-59) years. Structural equation modeling revealed that depression, anxiety, and body mass index did not significantly mediate the relationship between injury/injury severity and RMSSD. However, the 6MWT significantly mediated the relationship between CRTI and RMSSD (27% mediation). The indirect effect of 6MWT on the relationship between injury severity (NISS ≥ 25 vs. uninjured) and RMSSD was -0.06 (95% CI: -0.12, -0.00, P < .05). The findings suggest that greater physical function may improve HRV following CRTI. Longitudinal studies are warranted to further validate these findings.

Machine learning analysis of primary hyperhidrosis for classification of hyperhidrosis type and prediction of compensatory hyperhidrosis.

Although sympathectomy is highly effective for improving symptom, compensatory hyperhidrosis (CH) is a major issue. In this study, characteristics of primary hyperhidrosis were investigated in terms of the heart rate variability (HRV) parameters. Classification of hyperhidrosis type and prediction of CH after sympathicotomy were also determined using machine learning analysis. From March 2017 to December 2021, 128 subjects who underwent HRV tests before sympathicotomy were analyzed. T2 and T3 bilateral endoscopic sympathicotomy were routinely performed in patients with craniofacial and palmar hyperhidrosis, respectively. Data collected age, sex, body mass index (BMI), hyperhidrosis type, symptom improvement after sympathicotomy, the degrees of CH after sympathicotomy, and preoperative HRV findings. The independent risk factors associated with the degree of CH after sympathicotomy were investigated. Machine learning analysis was used to determine classification of hyperhidrosis type and prediction of the degree of CH. Preoperatively, patients with palmar hyperhidrosis presented with significantly larger standard deviation of normal-to-normal (SDNN), root mean square of successive differences (RMSSD), total power (TP), and low frequency (LF) than patients with craniofacial hyperhidrosis after controlling for age and sex (P=0.030, P=0.004, P=0.041, and P=0.022, respectively). More sympathetic nervous predominance was found in craniofacial type (P=0.019). Low degree of CH had significantly greater RMSSD (P=0.047), and high degree of CH showed more sympathetic nervous predominance (P=0.006). Multivariate analysis showed the type and expansion of sympathicotomy were significant factors for CH (P=0.001 and P=0.028, respectively). The neural network (NN) algorithm outperformed and showed a 0.961 accuracy, 0.961 F1 score, 0.961 precision, 0.961 recall, and 0.972 area under the curve (AUC) for classification of hyperhidrosis type. The random forest (RF) model outperformed showed a 0.852 accuracy, 0.853 F1 score, 0.856 precision, 0.852 recall, and 0.914 AUC for prediction of the degree of CH. The present study showed the machine learning algorithm can classify types and predict CH after sympathicotomy for primary hyperhidrosis with considerable accuracy. Further large-scale studies are needed to validate the findings and provide management guidelines for primary hyperhidrosis.

Long-term stability of respiratory sinus arrhythmia among adults with and without a history of depression.

Respiratory sinus arrhythmia (RSA) is an index of parasympathetic nervous system activity reflecting respiratory influences on heart rate. This influence is typically measured as high frequency heart rate variability (HF-HRV) or root mean square of successive differences (RMSSD) of adjacent inter-beat intervals. Examining the long-term stability of its measurement is important as levels of resting RSA have been conceptualized as a marker of individual differences; in particular, of an individual's autonomic regulation and affect-related processes, including emotion regulation. At present, it is not known if resting RSA levels reflect stable differences over a long-term period (i.e., >1 year). Even less is known about how RSA stability differs as a function of depression history and whether it relates to depression risk trajectories. In the present study, we examined the 1.5-year test-retest reliability of resting RSA using the intraclass correlation coefficient (ICC) in 82 adults: n = 41 with a history of depression (ever-depressed); n = 41 controls with no depression history (never-depressed). HF-HRV was fairly stable in both groups (ever-depressed ICC = 0.55, never-depressed ICC = 0.54). RMSSD was also fairly stable in ever-depressed adults (ICC = 0.57) and never-depressed controls (ICC = 0.40). ICC values for both indices did not differ between groups per overlapping 95% confidence intervals. Therefore, RSA stability as assessed by both frequency (HF-HRV) and time domain (RMSSD) measures was not attenuated by a depression history. Implications and the need for future research are discussed.

Effect of gait on, and repeatability of heart rate and heart rate variability measurements in exercising Warmblood dressage horses

Abstract Heart rate variability (HRV) is a non-invasive measurement of the balance between the sympathetic and parasympathetic innervation to the myocardium. Used as an indicator of health, welfare and fitness level, its measurement during exercise has been suggested to be helpful in sport horses. The aims of this study were to assess the within- and between-day repeatability of time-domain HRV-measurements during exercise, and to evaluate the effect of gait (as a factor of increasing exercise intensity) on HRV. Heart rate (HR), root mean square of successive differences (RMSSD) between normal heartbeats and the standard deviation of normal (R-R) intervals (SDNN) were assessed during a standardised exercise test (SET) on five consecutive days in a sample of 21 healthy Warmblood dressage horses. All variables showed good between-day repeatability (Spearman’s rank correlation coefficient), while only RMSSD showed reliable within-day repeatability (Wilcoxon signed-rank test). Increase of exercise intensity was significantly associated with increased HR and decreased RMSSD and SDNN, with a negative correlation between HR and the two HRV-measurements. HR and HRV values varied significantly with intensity of exercise (rest, walk, trot, canter and whole SET), though HRV at rest was not different to that at walk, and HRV at trot was not different to that at canter. In conclusion, the results of this study support the use and show the repeatability of time-domain HRV-measurements during exercise in Warmblood dressage horses. Further investigation for use of HRV in other equestrian disciplines, levels and health state is warranted.

Heart rate variability of elite female rowers in preparation for and during the national selection regattas: a pilot study on the relation to on water performance.

To comprehensively analyze elite female rowers, evaluating acute changes in HRV and subjective psychometrics during the NSR. Five elite female rowers (26 ± 2 years, 180 ± 8 cm, 82 ± 8 kg, 19 ± 6%fat) were recruited and tracked prior to and during NSR I and II. Morning HRV measures were completed using photoplethysmography (HRV4training) along with self-reported levels of fatigue, soreness, rating of perceived exertion, mentally energy and physical condition. Significant decreases were observed in log transformed root-mean square of successive differences (LnRMSSD; p = 0.0014) and fatigue (p = 0.01) from pre-to-during NSR, while mental energy (p = 0.01), physical condition (p = 0.01), and motivation (p = 0.006) significantly increased. These psychometric measures returned to pre-NSR levels, at post-NSR (all p < 0.05), though HRV remained slightly suppressed. NSR on-water performance was not correlated to LnRMSSD or the change in LnRMSSD (p > 0.05). HRV and psychometric measures are sensitive to the stress of elite rowing competition in females. However, HRV was not associated with on-water rowing performance during an elite rowing competition.

Stress recovery at home: Effects of the indoor visual and auditory stimuli in buildings

In order to explore the potential contribution of the visual and auditory environment on the mental stress recovery of people in indoor environment, the visual, auditory, and visual-auditory stimuli were selected to design 3 kinds of restorative environments, under which the subjects experienced the baseline stage, the stress-induction stage, and the recovery stage, in sequence. The stress was induced with the continuous high frequency noise at 70–80 dB. The Electrocardiogram (ECG) data of the subjects were recorded during the whole experiment, and the heart rate variability (HRV) analysis was conducted, producing the mean heart rate (HR), the root mean square successive difference (RMSSD), as well as the ratio of low to high frequency power (LF/HF). The stress level was evaluated with these indexes during the whole experiment. Results showed that mean HR and LF/HF were higher than that of the baseline after the stress-induction, while the mean RMSSD was significantly lower than the baseline level, which implied the stress rise was resulted from the stress-induction stage. In addition, it was found that the mean HR and LF/HF reduced after the participants experienced the visual, the auditory and the visual-auditory restorative environments, but the mean RMSSD increased, which suggested the attenuated stress level. Furthermore, it was observed that the RMSSD was the most sensitive to the stress. Based on that, the time for the stress-recovery was estimated with the mean RMSSD. Results showed that the visual and visual-auditory stimuli produced better acute recovery effect than that of the auditory, but in the long run the auditory stimulus could bring the most stress reduction, followed by the visual stimulus. This study produced a potential solution for the stress recovery at home, which could be important for the improvement of the mental health, cognitive performance and the productivity of the occupants.

A Real-Time Evaluation Algorithm for Noncontact Heart Rate Variability Monitoring.

Noncontact vital sign monitoring based on radar has attracted great interest in many fields. Heart Rate Variability (HRV), which measures the fluctuation of heartbeat intervals, has been considered as an important indicator for general health evaluation. This paper proposes a new algorithm for HRV monitoring in which frequency-modulated continuous-wave (FMCW) radar is used to separate echo signals from different distances, and the beamforming technique is adopted to improve signal quality. After the phase reflecting the chest wall motion is demodulated, the acceleration is calculated to enhance the heartbeat and suppress the impact of respiration. The time interval of each heartbeat is estimated based on the smoothed acceleration waveform. Finally, a joint optimization algorithm was developed and is used to precisely segment the acceleration signal for analyzing HRV. Experimental results from 10 participants show the potential of the proposed algorithm for obtaining a noncontact HRV estimation with high accuracy. The proposed algorithm can measure the interbeat interval (IBI) with a root mean square error (RMSE) of 14.9 ms and accurately estimate HRV parameters with an RMSE of 3.24 ms for MEAN (the average value of the IBI), 4.91 ms for the standard deviation of normal to normal (SDNN), and 9.10 ms for the root mean square of successive differences (RMSSD). These results demonstrate the effectiveness and feasibility of the proposed method in emotion recognition, sleep monitoring, and heart disease diagnosis.

The effect of being married on heart rate variability, an indicator of autonomic dysfunction: A retrospective study.

Heart rate variability (HRV) is a noninvasive assessment that reflects the autonomic functions of the heart and is known to be impaired in many diseases. In our study, we aimed to investigate the relationship between HRV and being married. The study included 104 patients, between the aged 20 to 40 years were included in the study. The patients were divided into 2 groups as 53 healthy married (group 1) and 51 healthy unmarried (group 2). 24-hour rhythm Holter recordings were performed on all married and unmarried patients. Group 1 had a mean age of 32 ± 5 years and 47.2% men, and group 2 had a mean age of 30 ± 5 years and 54.9% men. Standard deviation of normal to normal (SDNN) was 150 ± 40 versus 128 ± 30 ( P = .003), SDNN index was 66 ± 20 versus 56 ± 12 ( P = .004), the square root of the mean of the squares of the differences of the adjacent root mean square of successive differences (RMSSD) was 37 ± 10 versus 30 ± 10 ( P < .001), percentage of successive R-R intervals that differ by more than 50 milliseconds (PNN50) was 13.5 ± 7 versus 8.5 ± 7 ( P = .001), HF was 450 ± 270 versus 225 ± 130 ( P < .001) found to be significantly less in the group 2. LF/HF ratio was 1.68 ± 0.65 versus 3.31 ± 1.56 ( P < .001) found to be significantly higher in the group 2. In our study, it is possible to say that the sympathetic system effect on the heart was more dominant and the HRV was lower in the unmarried group.

Influence of 12 weeks of basketball training on college students' heart function.

This study aims to investigate the influence of 12 weeks of basketball training on college students' heart function. The subjects were 30 college male basketball players. Carry out 8-week interval training, monitor the training load and interval time of athletes, and strictly control the heart rate during the interval. Before and after training, we used safe and effective experimental instruments - without any damage to the athletes - to detect the relevant indicators of the athletes' physiological functions; hence we compared and analyzed the various indicators before and after training. The time domain indexes Root Mean Square of Successive Differences (RMSSD), Statistically Determined Spatial Drift (SDSD), percentage of NN50 in the total number of NN intervals (PNN50), and Standard Deviation of all NN intervals for all 5-min segment (SDNN) after training were significantly higher than those before training, and the differences were statistically significant (p<0.05). Average (Avag) and Statistically Determined Allocation Weights (SDAW) after training were significantly higher than those before training, the difference was statistically significant (p<0.05); Asymmetry (Asym) and Tension index (TI) were significantly lower than those before training, the difference was statistically significant (p<0.05), Application Information Index (ApInf) had no significant difference (p>0.05). There was no significant difference in shooting hit rate (p>0.05). The speed of the 8-character dribble in the whole field after training was significantly lower than that before training, and the differences were statistically significant (p<0.05). There was no significant difference in average jump height, maximum jump height, average time in the air, and best jump time in the air after training (p>0.05). For the test of athletes' explosive power, five vertical jumps in situ were selected for testing, and the jump height and time in the air of each vertical jump were counted to calculate the maximum and average values of five vertical jumps. The results showed that there was no significant change in the explosive force of the athletes' lower limbs after training. The reason may be that strength training needs to follow the principles of heavy load, specialization, exercise sequence and reasonable interval. The intermittent training method used during training is not specialized in strength training, and the reasonable interval of strength training was not considered in the training process. Intermittent training can increase the tension of the cardiac vagus nerve of college basketball players, increase the cardiac reserve function and the load that the heart can bear, so that the cardiac function can be improved well. It can improve the cardiopulmonary function and aerobic work ability of college basketball players. It can improve the adjustment ability of the heart, lungs, liver, and other organs of college basketball players. It also can increase the load intensity that the central nerve can bear and improve the function of the central nerve and autonomic nerve. The anti-fatigue ability of athletes can be improved. It can improve the speed quality of college basketball players.

Prognostic implications of ultra-short heart rate variability indices in hospitalized patients with infective endocarditis.

Infective endocarditis (IE) is a disease that poses a serious health risk. It is important to identify high-risk patients early in the course of their treatment. In the current study, we evaluated the prognostic value of ultra-short heart-rate variability (HRV), an index of vagal nerve activity, in IE. Retrospective analysis was performed on adult patients admitted to a tertiary hospital due to IE. A logistic regression (LR) was used to determine whether clinical, laboratory, and HRV parameters were predictive of specific clinical features (valve type, staphylococcal infection) or severe short-term complications (cardiac, metastatic infection, and death). The accuracy of the model was evaluated through the measurement of the area under the curve (AUC) of the receiver operating characteristic curve (ROC). An analysis of survival was conducted using Cox regression. A number of HRV indices were calculated, including the standard deviation of normal heart-beat intervals (SDNN) and the root mean square of successive differences (RMSSD). 75 patients, aged 60.3(±18.6) years old, were examined. When compared with published age- and gender-adjusted HRV norms, SDNN and RMSSD were found to be relatively low in our cohort (75%-76% lower than the median; 33%-41% lower than the 2nd percentile). 26(34.6%) patients developed a metastatic infection, with RMSSD<7.03ms (adjusted odds ratio (aOR) 9.340, p = 0.002), incorporated in a multivariate LR model (AUC 0.833). Furthermore, 27(36.0%) patients were diagnosed with Staphylococcus IE, with SDNN<4.92ms (aOR 5.235, p = 0.004), a major component of the multivariate LR model (AUC 0.741). Multivariate Cox regression survival model, included RMSSD (HR 1.008, p = 0.012). SDNN, and particularly RMSSD, derived from ultra-short ECG recordings, may provide prognostic information about patients presenting with IE.

Associations between physical activity and autonomic function during deep breathing test: the Swedish CArdioPulmonary bioImage Study (SCAPIS).

The deep breathing test (DBT) is a sensitive test of cardiovagal function. The aim of this study was to explore associations between physical activity and sedentary time, measured by accelerometer, and autonomic function, using DBT. In the Swedish Cardio-Pulmonary bioImage Study, men and women aged 50-64 were randomly invited from the general population. A total of 4325 subjects who underwent DBT and assessment of physical activity and sedentary time by accelerometery were included. ECG files from 1-min DBT were used to calculate measures of respiratory sinus arrhythmia [RSA; expiration-inspiration (E-I) difference and E/I ratio], heart rate variability [HRV; root mean square of successive differences (RMSSD), standard deviation of heart rates and mean circular resultant]. Low RSA and HRV was defined as the lowest 10% in the population. For accelerometer-assessed physical activity, there were significant associations between high percentage of sedentary time and low E/I (p < 0.01), and low RMSSD (p < 0.01) in an age- and sex-adjusted model, and between percentage of sedentary time and low RMSSD (p = 0.04) in a risk factor-adjusted model. Low RMSSD was less common in those with a high percentage of moderate to vigorous physical activity (p = 0.04, after risk-factor adjustment). These associations became non-significant when further adjusting for heart rate. We report associations between degree of physical activity and indices of autonomic dysfunction in a large population. The relationships were no longer significant after adjustments for heart rate, indicating that the relationship between physical activity and cardiovagal function partly is accounted for by reduced heart rate.

Heart rate variability during social interaction: Effects of valence and emotion regulation

Conceptual models of psychosocial influences on short-term changes (i.e., reactivity) in vagally-mediated heart rate variability (vmHRV) emphasize self-regulatory effort and social threat versus comfort. However, these two general perspectives have been tested separately in nearly all cases, limiting conclusions about the relative importance or possible interactive effects of effortful self-regulation and social stress. The present study compared effects of effort to regulate emotional expression and social stress versus safety on vmHRV reactivity during an interpersonal interaction, in a 2 (self-regulate emotion vs. express emotion freely) × 3 (positive vs. neutral vs. negative interaction valence) × 2 (male vs. female) between-subjects randomized factorial design. A sample of 180 undergraduates (90 women; 69 % White) discussed a current events topic (i.e., human-caused climate change) with a prerecorded partner, presented as a live interaction over a computer. Self-reports of affective responses, self-regulation effort, and appraisals of the partner's behavior, as well as observer ratings of participants' behavior during the interaction, supported the effectiveness of self-regulation and interaction valence manipulations, although the former manipulation may have been somewhat weaker than the latter. Primary analyses of high-frequency heart rate variability (HF-HRV) and root mean square of successive differences (RMSSD) in heart beat intervals recorded at baseline and during the interaction revealed larger decreases in vmHRV during negative than neutral or positive interactions, but no effects of self-regulation instructions. Overall, results indicated more robust effects of social stress on vmHRV reactivity, relative to effects of self-regulatory effort.

0882 The Longitudinal Relationship between Objective Sleep and Cardiovascular Parameters During Pregnancy

Abstract Introduction Growing evidence shows the important role of sleep on cardiovascular health in pregnant women with nearly 50% self-reporting poor sleep quality and 30% insufficient sleep. These sleep disturbances have been associated with adverse perinatal outcomes (e.g., hypertension, preterm births). Many studies have only used self-reported questionnaires during pregnancy. However, a few studies have utilized sleep labs and found that subjective and objective assessments of sleep varied from poor to low associations. The aim of this study was to examine the longitudinal relationship between objective sleep and cardiovascular parameters in pregnant women. Methods Seventeen healthy pregnant women with 88% self-identifying as Hispanic were consented to participate in the longitudinal observation study. Their average age was 27.8 years (SD=4.48). A validated Oura ring was used to daily monitor objective sleep and cardiovascular parameters across the pregnancy, including resting heart rate (HR), heart rate variability (HRV) indicated by RMSSD (root mean square of successive differences) of interbeat intervals, deep, light, and Rapid EYE Movement (REM) sleep, awake time and sleep onset latency. Mixed effects models were conducted to analyze daily changing patterns of these parameters using R-4.2.0 for Mac. Results Over the pregnancy, when deep and light sleep increased by 1 hour, heart rate decreased by 5.55 bpm (p&amp;lt; 0.001) and 1.32 bpm (p = 0.01), respectively; when REM sleep increased by 1 hour, heart rate increased by 2.15 bpm (p =0.049). Conversely, when deep and light sleep increased by 1 hour, RMSSD increased by 10.32 ms (p&amp;lt; 0.001) and 2.93 ms (p&amp;lt; 0.02), respectively; when REM sleep increased by 1 hour, RMSSD decreased by 7.27 ms (p=0.001). There were no significant associations between HR/RMSSD and awake time/sleep onset latency. Conclusion This study appears to be the first to investigate the longitudinal relationship between sleep and cardiovascular parameters among primarily Hispanic pregnant women in the U.S. in a non-lab setting. Our study provides preliminary evidence that longer deep/light sleep and shorter REM sleep may improve cardiovascular health among pregnant women. Support (if any) National Science Foundation grants including the Smart and Connected Communities (CNS: 1831918) and Collaborative Research: Integrative Heterogeneous Learning for Intensive Complex Longitudinal Data (DMS: 2210640).

The relationship between heart rate variability and TNM stage, co-morbidity, systemic inflammation and survival in patients with primary operable colorectal cancer

High vagal nerve activity, reliability measured by HRV, is considered protective in cancer, reducing oxidative stress, inflammation and opposing sympathetic nerve activity. The present monocentric study examines the relationship between HRV, TNM stage, co-morbidity, systemic inflammation and survival in patients who underwent potentially curative resections for colorectal cancer (CRC). Time-domain HRV measures, Standard Deviation of NN-intervals (SDNN) and Root Mean Square of Successive Differences (RMSSD), were examined as categorical (median) and continuous variables. Systemic inflammation was determined using systemic inflammatory grade (SIG) and co-morbidity using ASA. The primary end point was overall survival (OS) and was analysed using Cox regression. There were 439 patients included in the study and the median follow-up was 78 months. Forty-nine percent (n = 217) and 48% (n = 213) of patients were categorised as having low SDNN (< 24 ms) and RMSSD (< 29.8 ms), respectively. On univariate analysis, SDNN was not significantly associated with TNM stage (p = 0.830), ASA (p = 0.598) or SIG (p = 0.898). RMSSD was not significantly associated with TNM stage (p = 0.267), ASA (p = 0.294) or SIG (p = 0.951). Neither SDNN or RMSSD, categorical or continuous, were significantly associated with OS. In conclusion, neither SDNN or RMSSD were associated with TNM stage, ASA, SIG or survival in patients undergoing potentially curative surgery for CRC.

38 Heart rate variability as a predictor of racing performances in standardbred horses

Heart Rate Variability (HRV) is a non-invasive tool for assessing the autonomic regulation of heart rate through variations in RR-intervals. It reflects the control of parasympathetic and sympathetic autonomic functions in the cardiovascular system. In humans, HRV is used to adjust exercise training for improving performance. Also, some HRV parameters have been correlated to running performance and fitness status. In horses, although HRV has been used to assess behavioral response to stress, little is known regarding its correlation with performance. This experiment aimed to investigate if resting values of HRV correlate to racing performance in Standardbred horses. Forty-eight horses (27 stallions, 4 geldings and 17 mares; 2 to 7 years old; 2 to 95 races run) from Hunter Valley stables were followed over one year. Electrocardiograms were recorded twice (6 mo apart) using heart rate monitors Equimetre (Arioneo, France) for 10 min in the early morning when horses were in individual stalls. Horses did not undergo intense exercise the day before data collection. Analysis of HRV parameters was performed on Kubios HRV software to determine Standard Deviation (SDNN), Root Mean Square of Successive Differences (RMSSD), number of successive intervals differing more than 50ms (pNN50) and Standard Deviation from Poincaré plot (SD1 and SD2). Racing performances (total earnings, earnings perrace, racing time) were collected from LeTrot database for each horse over the whole career, and close to the day of measurement (one month before to 2 mo after). Performance and HRV parameters were correlated using Pearson coefficients, and linear regressions were performed to predict racing performances. Best time in career and close to HRV measurement were negatively correlated to SDNN, RMSSD, pNN50, SD1 and SD2 (P < 0.01; −0.46P < 0.03; 0.27 > r > 0.35). Total earnings and earnings per race during the 3 mo close to HRV measurement were correlated with RMSSD, pNN50 and SD1 (P < 0.05; 0.29 > r > 0.52). Prediction of total earnings and earnings per race from the HRV parameters within 3 mo close to the measure was modest (adjusted R2 = 0.31 and 0.24; P = 0.0004 and 0.0016 respectively). In human athletes, higher HRV parameters indicate greater parasympathetic tone, better training adaptation and increased recovery. In our study, horses with higher HRV parameters possibly also recovered better, as the trainer decided to make them race more (P < 0.01; R > 0.36). Further research focusing on inter-individual variations to accurately track the horses' training and schedule the racing program would be valuable.

Electronic cigarettes exposures modulate Heart Rate and Heart Rate Variability

Background: Despite a lack of empirical data, an unprecedented rise in electronic cigarettes (ECs) has been widely perceived as safe. Multiple studies support a causal link between tobacco cigarette (TC) use and cardiovascular (CV) diseases; however, there is a lack of data with EC use. We have previously shown that chronic and acute EC use decreases heart rate variability (HRV) in humans, likely via increased sympathetic nervous system activation. Objective: We aimed to evaluate HRV effects induced by brief EC exposures utilizing an in-vivo model for freely moving C57BL/6 mice. Methods and Results: Telemetry devices were implanted in the abdomen of six 10-week-old C57BL/6 male mice to monitor electrocardiographic activity continuously. Mice underwent an exposure protocol designed to reflect human vaping topography with two EC exposures, each lasting 15-minutes (4-sec puff/ 26-sec Air) followed by 45-min post-exposure periods. Air (primary control) and PBS (secondary control) were also included, each with their own post-exposure events. During EC exposures, we observed bradycardic effects in heart rate (HR) with the standard deviation of NN intervals (SDNN), root mean square of successive differences (RMSSD), and the proportion of adjacent normalized RR intervals that differed by more than 6 ms (pNN 6 ) significantly (p&lt; 0.05) altered as compared to Air exposures. After EC exposures, SDNN, RMSSD and pNN 6 parameters significantly decreased compared to Air. No significant differences between Air and PBS were observed in these parameters. Frequency domain parameters also indicated significant changes in HRV; the low frequency (LF) and high frequency (HF) bands showed marked increases during and after the EC exposures, while the log (LF/HF) ratio remained relatively unchanged, suggesting a possible coactivation of both parasympathetic and sympathetic branches of the autonomic nervous system. Conclusion: Short-term EC exposures lower heart rate and altered HRV in mice in an acute manner, suggesting that ECs may not be safe as previously assumed. This work was funded by the Tobacco-Related Disease Research Program (TRDRP) which included the High Impact Pilot Research Award [28IP-0036], the Cornelius Hopper Diversity Award Supplement and the Student Research Award Supplement, the UCLA Center for Occupational and Environmental Health (COEH) Student Project Award, and in part by the National Institute of Environmental Health Sciences (NIEHS) via the Student-to-Scientist Bridge program at California State University, Northridge [5R25ES025507]. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

36 Validation of a smart textile device for heart rate variability in horses at rest

Electrocardiography (ECG) and associated heart rate variability (HRV) are important in the assessment of equine cardiac health, welfare, and performance. Smart textiles have gained popularity as a method to replace standard adhesive electrodes, though limited validation work has been conducted, particularly in veterinary species. Therefore, the objective of this study was to assess the validity of a smart textile ECG device for heart rate (HR) and HRV assessment in horses at rest. Seven mixed-breed, healthy competition horses were recruited for a controlled clinical trial. Horses wore a smart textile ECG device (Skiin Equine) and a standard telemetric device (Televet 100) equipped with adhesive electrodes for simultaneous ECG recordings while unrestrained in stalls for 15 min. Raw data from both devices were analyzed using Kubios Premium to calculate HR and HRV metrics [average and standard deviationof RR intervals, the axial and perpendicular dispersions from the line of identity from the Poincaré plot (SD1 and SD2, respectively), root mean square of successive differences (RMSSD), percentage of successive RR interval differences (pNN50), and oscillations in the very-low frequency (VLF), low-frequency (LF), and high-frequency (HF) bands]. Data were compared using a Bland-Altman analysis with Pearson coefficients. Excellent agreement with small biases were observed between the 2 devices and perfect correlations (r = 1.0, P < 0.0001 for all) were found for all metrics assessed. This study demonstrates that a novel smart textile device can be used interchangeably with the standard telemetric system for assessment of HR and HRV in resting horses.

The Validity of Heart Rate Variability Obtained from Electrocardiography and Blood Pressure in Rats Subjected to Isoproterenol-Induced Heart Ischemia.

Heart rate variability (HRV) is calculated by electrocardiography (ECG-HRV) or blood pressure (BP-HRV). The purpose of this study was to determine the validity of the above methods in rats with normal and ischemic hearts during the baroreflex maneuver. The study was conducted at Shiraz University of Medical Sciences, Shiraz, Iran, in 2021. Sprague-Dawley rats were divided into a sham group and an isoproterenol-mediated cardiac ischemia (ISO) group. Saline and isoproterenol (150 mg/kg) injected subcutaneously for 2 consecutive days in the sham and ISO groups, respectively. Then, the animals were anesthetized with an intraperitoneal injection of sodium thiopental (60 mg/kg), and the femoral artery and vein were cannulated. Baroreflex was activated using an intravenous injection of phenylephrine (10 μg/100 μL saline). ECG, BP, and heart rate (HR) were recorded, and the time domain of HRV and baroreflex gain were calculated. Baroreflex gain in the ISO group (male, weight=275.8±2.8 g, n=8) was lower than that in the sham group (male, weight=258±2.3 g, n=8) (P<0.05). ECG-HRV indicated an increase in the standard deviation of the RR interval (SDRR), the index of overall HRV, and the parasympathetic index of the root mean square of successive differences (RMSSD) in both groups. However, the rise in SDRR and RMSSD in the ISO group was less than that in the sham group (P<0.05). SDRR and RMSSD obtained from BP did not show a difference between the sham and ISO groups, nor did they correspond with the results seen in baroreflex gain. BP-HRV was not as valuable as ECG-HRV in assessing cardiac ischemia.

Autonomic response to early head-up tilt in patients with severe traumatic brain injury: Analysis from a randomized feasibility trial.

Patients with severe traumatic brain injury (TBI) may have autonomic dysfunction, one manifestation of which is orthostatic intolerance. This potentially impairs physical rehabilitation. However, the exact mechanisms remain elusive. In 30 patients participating in a trial of early tilt training versus standard care and 15 healthy volunteers, 5-min electrocardiography was recorded in the supine position and during 70° head-up tilt. Heart rate variability was analyzed by the low- and high-frequency (LF and HF) power, the LF-HF ratio, the total power, the ratio of the standard deviation of normal-to-normal intervals (SDNN), the root mean square of successive differences (RMSSD), the detrended fluctuations, and sample entropy. In patients in the upright compared to the supine position, SDNN (p < 0.001), RMSSD (p < 0.001), and total power (p = 0.004) all decreased, while the remaining variables were unchanged; no long-term differences in heart rate variability in the supine position were found between early tilt training and standard care. In the healthy volunteers, all measures besides SDNN and total power changed significantly between supine and upright position. In patients with severe TBI compared to healthy volunteers, several measures of heart rate variability changed differentially during mobilization from the supine to the upright position.