Ultra-short Heart Rate Variability Research Articles

Exploring Ultra-short Heart Rate Variability Metrics in Patients with Diabetes Mellitus: A Reliability Analysis.

Ultra-short heart rate variability (HRV) metrics represent autonomic tone parameters derived using small epochs of interbeat interval data. These measures have risen in popularity with the advent of wearable devices that can capture interbeat interval data using electrocardiography (ECG) or photoplethysmography. Autonomic neuropathy in diabetes mellitus (DM) is well established, wherein 5-min HRV is conventionally used. Ultra-short measures have the potential to serve as markers of reduced autonomic tone in this patient population. Data of patients with Type I and Type II DM who had presented to our laboratory for autonomic neuropathy assessment were chosen for analysis. One-minute and 2-min epochs were chosen from 5 min of ECG data using standard software. Time domain, frequency domain, and nonlinear measures were computed from 1 to 2 min epochs, and reliability was compared with measures derived from 5-min HRV using intraclass correlation coefficients (ICCs). Data of 131 subjects (79 males, 52 females; mean age = 53.3 ± 12.16 years) were analyzed. All ultra-short HRV measures derived from 1 min to 2 min data showed good to excellent reliability (median ICC values ranging from 0.83 to 0.94) when compared with 5-min metrics. The notable exception was very low frequency (VLF) power, which showed poor reliability (median ICC = 0.43). Ultra-short HRV metrics derived from 1 to 2 min epochs of ECG data can be reliably used as predictors of autonomic tone in patients with DM. VLF power is poorly reproducible in these small epochs, probably due to variability in respiratory rates. Our findings have implications for ultra-short HRV estimation using short epochs of ECG data.

Relationship between ultra-short heart rate variability and short-term mortality in hospitalized COVID-19 patients

ObjectiveTo assess the association between ultra-short heart rate variability (US-HRV) and short-term mortality in patients with COVID-19 and develop prognostic prediction models to identify high-risk patients as early as possible. MethodsA retrospective cohort study was performed on 488 patients diagnosed with COVID-19 and hospitalized in the First Affiliated Hospital of Fujian Medical University from December 2022 to January 2023. 10-s electrocardiogram (ECG) data were available for these patients. The US-HRV parameters including standard deviation of all normal-to-normal R-R intervals (SDNN) and root mean square of successive differences between normal-to-normal R-R intervals (rMSSD) were calculated using Nalong ECG software. The endpoint was short-term mortality, including in-hospital mortality or mortality within 1 week after discharge. ResultsOf the 488 patients, 76 (15.6%) died. The SDNN and rMSSD in the death group were significantly lower than those in the survival group (P < 0.001). The area under the receiver operating characteristic (ROC) curve (AUC) for SDNN and rMSSD to predict mortality was 0.761 and 0.715, respectively. The combined use of SDNN and rMSSD had an AUC of 0.774. The mortality rate in the group with SDNN ≤7.5 ms was higher than that of SDNN >7.5 ms group (P < 0.05). With the decrease of SDNN, the mortality of patients showed an upward trend, and the mortality of patients with SDNN ≤2 ms was the highest (66.7%). Multivariate logistic regression analysis identified SDNN as an independent predictor of prognosis (odds ratio (OR) = 5.791, 95% confidential interval (CI) 1.615–20.765, P = 0.007). The AUC of Model 1 (simple model) was 0.866 (95% CI 0.826–0.905). The AUC of Model 2 (comprehensive model) was 0.914 (95% CI 0.881–0.947). ConclusionSDNN was associated with short-term mortality and provided the additional discriminatory power of the risk stratification model for hospitalized COVID-19 patients.

Mental stress detection from ultra-short heart rate variability using explainable graph convolutional network with network pruning and quantisation

Mental stress detection from ultra-short heart rate variability using explainable graph convolutional network with network pruning and quantisation

Visually assessing work performance using a smartwatch via day-to-day fluctuations in heart rate variability.

To optimize workplace health promotion, a simple method for quantifying allostatic load response is needed. This study examines the feasibility of optimizing objective anxiety and presenteeism monitoring using daily smartwatch-measured ultra-short heart rate variability (HRV). Office workers without diagnosed disease prospectively performed 30 s HRV self-measurement each morning for two months and responded to the State-Trait Anxiety Inventory (STAI) and Work Limitation Questionnaire (WLQ). Logistic regression analysis examined daily HRV parameters in the high-trait anxiety group (HTA, STAI ≥ 40) using mean and variance HRV, age, self-reported gender, and body mass index (BMI). The ideal cutoff value enabled comparison of WLQ using the Mann-Whitney U test. Heart rate variability data were collected for 279 participants (male ratio, 83.9%; age, 42 ± 10 years) who completed questionnaires and monitored HRV for 30+ days. Compared to the low-trait anxiety group, HTA exhibited higher variance of the log-transformed coefficient of component variance of high-frequency component (LnccvHF) and low-frequency per HF (Lnccv L/H), in addition to differences in the means of these HRV parameters. In addition to BMI (odds ratio [OR] = 0.92, p = 0.02) and mean LnccvL/H (OR = 10.75, p < 0.01), the variance of Lnccv L/H was an independent predictor of HTA (OR = 2.39E + 8, p = 0.011). The daily Lnccv L/H dispersion group had a lower WLQ productivity loss score (p = 0.02, r = 0.17). By focusing on HRV dispersion status, this simple and instantly applicable daily HRV monitoring system enables optimized quantitative monitoring of anxiety and productivity.

Heart rate of fire: exploring direct implementation of physiological measurements in realistic shoot/don't-shoot simulations.

Shooting simulations provide an excellent opportunity to train use-of-force decisions in controlled environments. Recently, military and law enforcement organizations have expressed a growing desire to integrate physiological measurement into simulations for training and feedback purposes. Although participants can easily wear physiological monitors in these scenarios, direct implementation into training may not be simple. Theoretical problems exist in the ultra-short heart rate variability windows associated with use-of-force training, and practical problems emerge as existing scenario libraries at training organizations were not designed for physiological monitoring. The current study explored the challenges and possibilities associated with direct implementation of physiological monitoring into an existing library of firearms training scenarios. Participants completed scenarios in a shooting simulator using existing military training scenarios while wearing a device to monitor their heart rate. The results revealed lower heart rate variability (approximately 6%) occurred in scenarios where participants did not have to fire weapons, indicating that don't-shoot scenarios may actually impose more cognitive stress on shooters. Additional evidence further demonstrated how both behavioral and physiological factors could be used concomitantly to predict unintentionally firing on non-hostile actors. However, behavioral measures were more predictive (e.g., β = .221) than physiological measures (e.g., β = -.132) when the latter metrics were limited to specific scenarios. Qualitative results suggest that simply applying physiological monitoring to existing shooting simulations may not yield optimal results because it would be difficult to directly integrate physiological measurement in a meaningful way without re-designing some elements of the simulations, the training procedure, or both. Future use-of-force shooting simulations should consider designing novel scenarios around the physiological measurement rather than directly implementing physiological assessments into existing libraries of scenarios.

Ultra-short heart rate variability over 15 seconds is associated with increased long-term risk of cardiovascular disease

Abstract Background Heart rate variability (HRV) is an established cardiac autonomic marker with prognostic value, whose application at scale is limited by the fact it requires relatively long ECG recordings (≥ 5-min). Ultra-short HRV (usHRV) is derived from much shorter recordings and can be measured at scale using standard and wearable ECGs, but its association with cardiovascular events is undetermined. Purpose (1) To validate usHRV measured using 15-second ECGs and (2) To investigate association with multiple outcomes in individuals without cardiovascular disease. Methods Data from the National Survey for Health and Development (N=1,337) was used to assess the agreement between usHRV and standard HRV (which requires ≥5-minute ECGs). Participants from the first visit of the UK Biobank study (2009-2013), without cardiovascular disease and with an ECG (N=51,628, 64% male, median age 58) were recruited to assess association of usHRV with outcomes. Exposures included usHRV time-domain indices RMSSD and SDSD, which measure fast heart rate variations related to cardiac vagal modulation, and usHRV spectral index PHF, which is related to respiratory sinus arrhythmia. Outcomes included incident atrial fibrillation (AF), major adverse cardiovascular events (MACE), stroke and mortality. Results HRV indices RMSSD and SDSD measured in 15-second ECGs showed excellent agreement (median correlation coefficient ≥0.84 and narrow limits of agreement in Bland-Altman analyses, Fig. 1) with indices measured from 6-minute ECGs, while PHF showed good agreement (median correlation coefficient 0.70 and small positive bias). In the UK Biobank, after a median follow-up of 11.5 (11.4-11.7) years, incidence of AF, MACE, stroke, and mortality was 3.8%, 3.9%, 1.7% and 4.3%, respectively. An inverse linear association was found between usHRV and AF and stroke, with hazard ratios between 1.07 and 1.13 for a standard deviation decrease in RMSSD, SDSD and PHF, p&amp;lt;0.05. Non-linear cox regressions (Fig. 2) showed that the association of RMSSD (and SDSD) with MACE and mortality was U-shaped with individuals in the bottom quintiles of usHRV indices showing increased risk with respect to those in the third quintile (hazard ratios between 1.16 and 1.29, p&amp;lt;0.05). Conclusions Cardiac autonomic dysfunction measured with usHRV from 15-second ECGs is associated with increased risk of AF, MACE, stroke, and mortality in individuals without cardiovascular disease. usHRV can be measured from both standard clinical ECGs and novel wearable devices and may have a role to monitor autonomic function at scale and improve understanding and prevention of cardiovascular disease.Fig1: 6-min vs 15-sec HRVFig2: usHRV association with outcomes

Long-term association of ultra-short heart rate variability with cardiovascular events

Heart rate variability (HRV) is a cardiac autonomic marker with predictive value in cardiac patients. Ultra-short HRV (usHRV) can be measured at scale using standard and wearable ECGs, but its association with cardiovascular events in the general population is undetermined. We aimed to validate usHRV measured using ≤ 15-s ECGs (using RMSSD, SDSD and PHF indices) and investigate its association with atrial fibrillation, major adverse cardiac events, stroke and mortality in individuals without cardiovascular disease. In the National Survey for Health and Development (n = 1337 participants), agreement between 15-s and 6-min HRV, assessed with correlation analysis and Bland–Altman plots, was very good for RMSSD and SDSD and good for PHF. In the UK Biobank (n = 51,628 participants, 64% male, median age 58), after a median follow-up of 11.5 (11.4–11.7) years, incidence of outcomes ranged between 1.7% and 4.3%. Non-linear Cox regression analysis showed that reduced usHRV from 15-, 10- and 5-s ECGs was associated with all outcomes. Individuals with low usHRV (< 20th percentile) had hazard ratios for outcomes between 1.16 and 1.29, p < 0.05, with respect to the reference group. In conclusion, usHRV from ≤ 15-s ECGs correlates with standard short-term HRV and predicts increased risk of cardiovascular events in a large population-representative cohort.

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.

Evaluating heart rate variability with 10 second multichannel electrocardiograms in a large population-based sample.

Heart rate variability (HRV), defined as the variability of consecutive heart beats, is an important biomarker for dysregulations of the autonomic nervous system (ANS) and is associated with the development, course, and outcome of a variety of mental and physical health problems. While guidelines recommend using 5 min electrocardiograms (ECG), recent studies showed that 10 s might be sufficient for deriving vagal-mediated HRV. However, the validity and applicability of this approach for risk prediction in epidemiological studies is currently unclear to be used. This study evaluates vagal-mediated HRV with ultra-short HRV (usHRV) based on 10 s multichannel ECG recordings of N = 4,245 and N = 2,392 participants of the Study of Health in Pomerania (SHIP) from two waves of the SHIP-TREND cohort, additionally divided into a healthy and health-impaired subgroup. Association of usHRV with HRV derived from long-term ECG recordings (polysomnography: 5 min before falling asleep [N = 1,041]; orthostatic testing: 5 min of rest before probing an orthostatic reaction [N = 1,676]) and their validity with respect to demographic variables and depressive symptoms were investigated. High correlations (r = .52-.75) were revealed between usHRV and HRV. While controlling for covariates, usHRV was the strongest predictor for HRV. Furthermore, the associations of usHRV and HRV with age, sex, obesity, and depressive symptoms were similar. This study provides evidence that usHRV derived from 10 s ECG might function as a proxy of vagal-mediated HRV with similar characteristics. This allows the investigation of ANS dysregulation with ECGs that are routinely performed in epidemiological studies to identify protective and risk factors for various mental and physical health problems.

The Importance of Time-Domain HRV Analysis in Cardiac Health Prediction

Heart rate variability (HRV) is defined as the momentary variation in the end heart rate (EHR) estimated at various intervals (time domains), such as from 2 min (ultra-short HRV) to 24 h (long HRV) intervals. The R peak interval (RRI) between two consecutive beats called momentary heart rate (MHR) provides insight into the impending cardiovascular risk and not the EHR. The autonomic nervous system (ANS) is in charge of maintaining physiological homeostasis by keeping the MHR and in turn the EHR within the normal range of 60–100 bpm. ANS has two components – the sympathetic nervous system (SNS) and the parasympathetic nervous system (PNS). The former increases HR (reduces RRI) while the latter reduces it. Therefore, the RR time-domain-HRV-data (THD) provides better insight into overall health than the EHR. Six types of THDs, e.g., mean-HR, mean-RR, SDNN, SDHR, RMSSD, and pNN50 are discussed in this article.

Non-Invasive Assessment of Ultra-Short Time Heart Rate Variability During Wingate Test

The aim of present study was to investigate the sedentary healthy men’s ultra-short heart rate variability (HRV) during the Wingate Anaerobic Test (WAnT) (30-sec) and parasympathetic reactivation in the first 60-sec after WAnT. The final sample comprised 101 individuals (Mean±SD; Age=28.9±4.8 years, Height=176.5±5.5 cm, Weight=89.8±8.8 kg). Anaerobic powers were measured by WAnT. Heart rate variability (HRV) was then recorded as 60-sec before the test for 30-sec and 60-sec after the test. HRV was measured by Polar V800 GPS Sports Watch with Heart Rate Monitor and Polar H7 band. To compare the testing stages HRV parameters, repeated one-way analysis of variance (ANOVA) was used. Binary comparisons were determined with the Bonferroni test. The relationship between exercise data of heart rate variability and power average watt was assessed by the Pearson correlation test. The Effect Size Cohen's d was calculated. The main finding of this study is that pre-test (60-sec) HRV values continue to drop dramatically during test (30-sec) and post-test (60-sec) measurements (p&amp;lt;0.05). Also, no correlation was observed between performance and HRV data during testing (r=-0.08, p&amp;gt;0.05). In conclusion, the present study was not observed to sign of HRV recovery during 60-sec after the 30-sec WAnT. HRV recorded in the first 60 seconds after maximum anaerobic exercise program in sedentary healthy men may be considered to exhibit an imbalance in the parasympathetic activity of the autonomic nervous system.

Ultra Short Heart Rate Variability Predicts Clinical Outcomes in Patients with a Clinical Presentation Consistent with Myocarditis: A Derivation Cohort Analysis.

Myocarditis prognosis varies substantially, hence identification of novel prognostic factors is crucial. The prognostic role of ultra-short heart-rate variability (HRV) in myocarditis remains unknown. In a retrospective study, adult patients admitted to a tertiary hospital due to clinically suspected myocarditis were included. Clinical, laboratory and HRV parameters were assessed as predictors of severe short term complications (heart failure (HF), dilated cardiomyopathy—DCM, ventricular arrhythmia—VA and death), utilizing logistic regression (LR). Accuracy was evaluated with receiver operating characteristic (ROC) curve area under the curve (AUC). HRV indices included standard deviation of normal beat intervals (SDNN) and root mean square of successive differences (RMSSD). 115 patients, aged 34 (±13) years old, were examined. Six patients (5%) developed severe HFrEF. RMSSD was included in a multivariate LR model (RMSSD < 10.72 ms adjusted odds ratio (AOR) 14.056, p-value 0.024). Model classification accuracy was very good, with an AUC of 86%. Eight patients (7%) developed DCM. RMSSD < 10.72 ms was included in a multivariate classification model (AOR 8.826, p-value 0.013); model classification AUC of 82%. HRV did not predict development of VA or death. SDNN and especially RMSSD may be prognostic indicators in myocarditis.

Exploring of cardiac autonomic activity with heart rate variability in long-term kratom (Mitragyna speciosa Korth.) users: a preliminary study.

BackgroundKratom is a psychoactive plant used to enhance productivity among laborers in Southeast Asian countries. Previous findings from in vitro research of mitragynine, a major component of kratom, suggested a possible risk of heart function abnormality. However, the cardiac autonomic function in long-term kratom users with chewing forms has never been studied. This study aimed to investigate heart rate variability (HRV) indices of cardiac autonomic function in long-term kratom chewers (LKC), compared to the control levels, and also to examine the correlation between HRV indices and relevant kratom use factors.MethodA total number of 50 participants consisted of LKC (n = 31) who regularly chewed fresh kratom leaves for at least 2 years and demographically matched control subjects (n = 19). Resting electrocardiogram (ECG) signals were recorded from subjects for 3 min to analyze the ultrashort HRV in the frequency domain. The normalized low frequency (LFn) and high frequency (HFn) were chosen to be the HRV indices to evaluate cardiac autonomic function. The comparison of HRV indices between groups and the correlation between HRV indices and duration and quantity of kratom use was further conducted in statistical analysis.ResultsThe LKC significantly increased LFn together with enhanced HFn compared to the control group tested, indicating that LKC changed cardiac autonomic function with parasympathetic dominance. Furthermore, no significant correlation between the HRV indices and the duration and quantity of kratom use was found, suggesting that the HRV indices were not relevant to these factors. The present study provided scientific-based evidence of cardiac autonomic modulation in long-term kratom chewers. LFn and HFn may be promising cardiac autonomic indicators for monitoring health outcomes in LKC.

Autonomic Nervous System Function After Dynamic Exertion Among Athletes At Medical Clearance Following Concussion

The autonomic nervous system (ANS) is commonly disrupted following sport-related concussion (SRC), and safe return to play/activity (RTP/A) is predicated on physiological recovery of ANS and other inter-related subsystems. Ultrashort (<5 min) heart rate variability (HRV) following exercise may be a proxy measure of ANS function but has predominately been measured following aerobic exertion without sport-specific movements. Dynamic exertion involves rapid change-of-direction tasks at varying intensities to perturb the vestibular and ocular subsystems in addition to the ANS. To date, researchers have yet to examine ultrashort HRV following dynamic exertion among athletes at medical clearance to RTP/A. PURPOSE: Compare age-estimated percentage of heart rate (HR %max) throughout a dynamic exertion assessment, in addition to post-exertion blood pressure and ultrashort HRV outcomes between athletes upon RTP/A from SRC with healthy athletes. METHODS: A sample of 23 (Female = 10, 43.5%) athletes at medical clearance to RTP/A (CONCUSS) and 23 sex-, age-, and sport-matched healthy athletes (CONTROL) completed a 5-min seated rest period prior to and following the dynamic exertion test. The dynamic exertion test is comprised of a12-min treadmill run and a series of functional movements and change-of-direction tasks. The root-mean-square of the successive differences (RMSSD) and standard deviation of successive heart beats (SDNN) were obtained from the final 3-min of pre- and post-EXiT rest periods. Between-group comparisons were conducted with a series of independent sample t-tests for HR %max and blood pressure, and 2X2 (GROUP X TIME) ANOVAs for RMSSD and SDNN. RESULTS: Main effects were observed for GROUP whereby CONCUSS had lower (less variable) RMSSD (p = .049, Ƞp2 = .209) and SDNN (p = .047, Ƞp2 = .212) than CONTROL, and for TIME as a reduction in RMSSD (p < .001, Ƞp2= .740) and SDNN (p < .001, Ƞp2= .760). HR %max and blood pressure were similar between groups (p > .05). CONCLUSION: ANS dysfunction may persist beyond clinical recovery in some athletes returning to sport after SRC. This is the first study to report differences in HRV between recently concussed and healthy athletes after dynamic exertion. Future work should consider the role of ANS function post-exertion to improve medical clearance decision making.

Self-recorded heart rate variability profiles are associated with health and lifestyle markers in young adults.

To quantify associations between self-recorded heart rate variability (HRV) profiles and various health and lifestyle markers in young adults. Otherwise healthy volunteers (n = 40, 50% male) recorded 60-s, post-waking HRV with a cost-free mobile application in supine and standing positions for 7days. The 7-day average and coefficient of variation (CV, reflects daily fluctuation) for the mean RR interval and root mean square of successive differences (LnRMSSD) were assessed. 7-day sleep duration and physical activity profiles were characterized via wrist-worn accelerometer. Subsequent laboratory assessments included aerobic fitness ([Formula: see text]O2peak) and markers of cardiovascular, metabolic, and psychoemotional health. Associations were evaluated before and after [Formula: see text]O2peak adjustment. Bivariate correlations (P < 0.05) demonstrated that higher 7-day averages and/or lower CV values were associated with higher activity levels and superior cardiovascular (lower systolic and diastolic blood pressure [BP] and aortic stiffness [cf-PWV]), metabolic (lower body fat percentage, fasting glucose, and low-density lipoprotein cholesterol [LDL-C]), and psychoemotional health (lower perceived stress) markers, with some variation between sexes and recording position. In males, associations between HRV parameters and cf-PWV remained significant following [Formula: see text]O2peak adjustment (P < 0.05). In females, HRV parameters were associated (P < 0.05) with numerous cardiovascular (systolic and diastolic BP, cf-PWV) and metabolic (fasting glucose and LDL-C) parameters following [Formula: see text]O2peak adjustment. Higher or more stable supine and standing HRV were generally associated with superior health and lifestyle markers in males and females. These findings lay groundwork for future investigation into the usefulness of self-recorded ultra-short HRV as a health-promoting behavior-modification tool in young adults.

The Effect of High-Altitude Acclimatisation on Ultra-Short Heart Rate Variability.

IntroductionHigh-altitude (HA) exposure affects heart rate variability (HRV) and has been inconsistently linked to acute mountain sickness (AMS). The influence of increasing HA exposure on ultra-short HRV and its relationship to gold standard HRV measures at HA has not been examined.MethodsThis was a prospective observational study of adults aged ≥ 18 years undertaking a HA trek in the Dhaulagiri region of the Himalayas. Cardiac inter-beat-intervals were obtained from a 10-s recording of supra-systolic blood pressure (Uscom BP+ device) immediately followed by 300 s single lead ECG recording (CheckMyHeart device). HRV was measured using the RMSSD (root mean square of successive differences of NN intervals) at sea level (SL) in the United Kingdom and at 3,619, 4,600, and 5,140 m at HA. Oxygen saturations (SpO2) were measured using finger-based pulse oximetry. The level of agreement between the 10 and 300 s RMSSD values were examined using a modified Bland–Altman relative-difference analysis.ResultsOverall, 89 participants aged 32.2 ± 8.8 years (range 18–56) were included of which 70.8% were men. HA exposure (SL vs. 3,619 m) was associated with an initial increase in both 10 s (45.0 [31.0–82.0]) vs. 58.0 [33.0–119.0] ms) and 300 s (45.67 [33.24–70.32] vs. 56.48 [36.98–102.0] ms) in RMSSD. Thereafter at 4,600 and 5,140 m both 10 and 300 s RMSSD values were significantly lower than SL. From a total of 317 paired HRV measures the 10 and 300 s RMSSD measures were moderately correlated (Spearman r = 0.66; 95% CI: 0.59–0.72; p < 0.0001). The median difference (bias) in RMSSD values (300 s − 10 s) was −2.3 ms with a lower and upper limit of agreement of −107.5 and 88.61 ms, respectively with no differences with altitude. Overall, 293/317 (92.4%) of all paired HRV values fell within the 95% CI limits of agreement. Neither HRV method was predictive of AMS.ConclusionIncreasing HA affects ultra-short HRV in a similar manner to gold-standard 300 s. Ultra-short HRV has a moderate agreement with 300 s measurements. HRV did not predict AMS.

Ultra-short heart rate variability and Poincaré plots

The short-term heart rate variability records of 5 minutes are currently considered very extensive compared to other indicators of health and well-being of people, such as body weight, blood glucose, blood pressure, etc. To find records of indicators less than 5 minutes, ultra-short heart rate variability, equivalent to the short-term heart rate variability, samples registers of 5 minutes is used to extract SS (stress score index) and S / PS (sympathetic/parasympathetic ratio) from the Poincaré diagram and correlate with the time and frequency domain of a group of subjects. To do this, the electrocardiographic signals were recorded for 300 seconds at rest then, the cardiotachograms (RR series) were calculated and used as a gold standard, and cardiotachogram were also calculated at intervals of 60, 90, 120, 180, and 240 seconds to perform the analysis of concordance with the gold standard. We use concordance analysis: Spearman, Bland, and Altman correlation, and Cliff's delta. This study set out to, that the indicator S/PS -- proposed for the analysis of the autonomic balance -- could be regarded as an alternative for traditionally be used LF/HF (Low Frequency / High Frequency) of the frequency domain or SD21 (SD2 / SD1) of the graphic Poincaré domain. In addition, the SS times within records of 120 seconds, were equivalent to those of short-term HRV and S/PS of 90 seconds. This finding, while preliminary, suggests that a reduction in measurement times will make it possible to increase the use of heart rate variability analysis. In future investigations, it might be possible to use these indicators in different populations and use of different pre-processing methods.

Effects on Heart Rate Variability of Stress Level Responses to the Properties of Indoor Environmental Colors: A Preliminary Study.

Color is the most potent stimulating factor affecting human vision, and the environmental color of an indoor space is a spatial component that affects the environmental stress level. As one of the methods of assessing the physiological response of the autonomic nervous system that influences stress, heart rate variability (HRV) has been utilized as a tool for measuring the user’s stress response in color environments. This study aims to identify the effects of the changes of hue, brightness, and saturation in environmental colors on the HRV of two groups with different stress levels—the stress potential group (n = 15) and the healthy group (n = 12)—based on their stress level indicated by the Psychosocial Well-being Index (PWI). The ln(LF), ln(HF), and RMSSD values collected during the subjects’ exposure to 12 environments colors of red and yellow with adjusted saturation and brightness, were statistically analyzed using t-test and two-way ANOVA. The results show that the HRV values in the two groups did not significantly vary in response to the changes in hue, brightness and saturation. The two groups’ stress factors distinguished according to the stress levels by the PWI scale affected the In(LF) parameter, which demonstrates that the PWI index can be utilized as a reliable scale for measuring stress levels. The ultra-short HRV measurement record and the use of a sole In(LF) parameter for stress assessment are regarded as the limitations of this study.

Ultra-short Heart Rate Variability Is Associated With Arterial Stiffness In Young Healthy Individuals

Heart rate variability (HRV), the time-difference between heartbeats, is a convenient marker of autonomic function. Single-day laboratory studies examining associations between HRV and arterial stiffness, a strong predictor of future cardiovascular events and all-cause mortality, have produced mixed results. This may be due to a failure to account for body position or lability in day-to-day HRV. PURPOSE: To assess relationships between self-recorded, multi-day, supine and standing HRV measures with arterial stiffness in young healthy adults. METHODS: Twenty-one males (24 ± 5 yrs; 24 ± 17% body fat) and 20 females (21 ± 3 years; 34 ± 7% body fat) recorded ultra-short (i.e., 60-s), post-waking HRV measures in supine and standing positions for 7 days via a Bluetooth heart rate monitor and smartphone application. Following the HRV measurement period, participants reported to the laboratory in a fasted state during morning hours. Augmentation index for a heart rate of 75 beats per minute (AIx75) via pulse wave analysis, and carotid-femoral pulse wave velocity (cf-PWV) via applanation tonometry were acquired as non-invasive indices of arterial stiffness. Associations between average supine and standing 7-day natural logarithm of the root-mean square of successive differences (lnRMSSDavg), and their coefficients of variation (lnRMSSDcv), with AIx75 and cf-PWV were assessed. RESULTS: Supine and standing lnRMSSDavg were 4.4 ± 0.4 and 3.5 ± 0.5 ms in men, and 4.1 ± 0.6 and 3.1 ± 0.5 ms in women, respectively. Supine and standing lnRMSSDcv were 8.1 ± 3.4 and 10.6 ± 5.4% in men, and 9.8 ± 5.2 and 13.0 ± 4.4% in women, respectively. In men, supine lnRMSSDavg (r = -.62) and standing lnRMSSDcv (r = .55) were associated with cf-PWV (6.2 ± 0.84 m/s; P < 0.05), but no associations were observed between HRV indices and AIx75 (2.2 ± 12.3%; P > 0.05). In women, supine lnRMSSDavg (r = -.52) and lnRMSSDcv (r = .52), and standing lnRMSSDmean (r = -.51) were associated with cf-PWV (5.8 ± 0.5 m/s; P < 0.05), and supine lnRMSSDcv was associated with AIx75 (5.7 ± 9.8%; P < 0.05). CONCLUSIONS: Multi-day, self-recorded, HRV measures were related to cf-PWV in young healthy men and women, and AIx75 in women. More numerous and stronger associations between HRV and cf-PWV vs. AIx75 portend a greater autonomic influence on proximal aortic vs. systemic arterial stiffness.

Ultra-short heart rate variability reliability for cardiac autonomic tone assessment in mesial temporal lobe epilepsy

Autonomic dysfunction in epilepsy is well-described. Heart rate variability (HRV) is a useful method to evaluate autonomic cardiac tone. Cardiac dysfunction may be involved in sudden unexpected death in epilepsy (SUDEP). HRV is a promising biomarker to enlighten the heart-brain axis role in SUDEP, but the required duration for a proper HRV recording in clinical routine remains unknown. This study aimed to verify the reliability of ultra-short HRV indices to evaluate cardiac autonomic tone in patients with epilepsy (PWE). Thirty-nine patients with mesial temporal lobe epilepsy (MTLE) had electrocardiogram recordings during the first day of video-EEG. Pearson’s correlations were performed to evaluate the association between ultra-short HRV indices (five 1-min and five 30-s epochs) with standard time recording (5-min) and ANOVA compared the differences between mean HRV indices across epochs. Time domain (TD) indices showed higher mean r values when compared to frequency domain (FD) indices in 1-min (TD: r 0.80–0.99, FD: r 0.61–0.95) and 30-s epochs (TD: r 0.69–0.99, only high frequency: mean r values of 0.96). ANOVA evidenced that standard deviation of RR intervals and very low frequency means had at least 3 epochs significantly different for 1-min and 30-s epochs. Root mean square of the successive differences of RR intervals (rMSSD) presented higher Pearson’s coefficient values and lower percentage of variation at 1-min or 30-s epochs in comparison to other HRV indices. In conclusion, rMSSD is the most reliable ultra-short HRV index for cardiac autonomic tone assessment in MTLE. The prognostic value of ultra-short HRV for cardiovascular risk evaluation in epilepsy remains to be determined in future studies.