Root Mean Square Of Successive Differences Research Articles

The Effect of Transcutaneous Vagus Nerve Stimulation on Heart Rate Variability during Paced Breathing

PurposeTranscutaneous vagus nerve stimulation (tVNS) is an effective, non‐invasive method of electrically stimulating the vagus nerve without surgical procedures and it is FDA‐approved to treat cluster headache and migraine. One approach of tVNS is to stimulate the auricle branch of the vagus nerve (tVNSab) by sending a small electrical current through the tragus of the ear. Previous evidence indicates that heart rate (HR) is lowered, indices of heart rate variability (HRV) are increased, and muscle sympathetic nerve activity is decreased following 10‐15 min of tVNSab. However, these previous investigations did not control for respiration, which can influence autonomic activity. Thus, we tested the hypotheses that tVNSab would lower heart rate and increase indices of HRV that reflect cardiac parasympathetic activity during paced breathing (PB).MethodsSeven healthy adults (age: 20 ± 3 y; BMI:19 ± 7 kg/m2, 3 women) completed two randomized visits; bilateral tVNSab (pulse width = 200 ms; pulse frequency = 30 Hz) or a time‐control visit (SHAM) in which electrodes were secured on the tragus, but no current was applied. A 3‐lead ECG was utilized to record cardiac rhythm and HR. After baseline (PRE), tVNSab/SHAM was initiated and continued throughout data collection. Data were collected at PRE and during each intervention (STIM) during 5 min of PB. During PB, participants breathed in concert to a metronome set at 15 breaths/min. The root mean square of successive differences (RMSSD) was chosen as a marker of HRV in the time‐domain, while the frequency domain was assessed via low‐frequency (LF) and high‐frequency (HF) power. Additionally, non‐linear HRV analysis was performed using Poincare plots to calculate standard deviation 1 (SD1) and 2 (SD2). Values are reported as mean ± SD.ResultsHR was not different at PRE (tVNSab: 73 ± 15; SHAM: 73 ± 10 bpm; P = 0.92) or during STIM (tVNSab: 74 ± 14; SHAM: 75 ± 11 bpm; P = 0.87). RMSSD was not different at PRE (tVNSab: 69 ± 67; SHAM: 62 ± 46 ms; P = 0.16) or during STIM (tVNSab: 69 ± 70; SHAM: 58 ± 48 ms; P = 0.06) and it did not change in either condition (tVNSab: P = 0.87; SHAM: P = 0.59). LF was different at PRE (tVNSab: 1160 ± 654; SHAM: 1916 ± 1917 ms2; P = 0.01) but not during STIM (tVNSab: 1382 ± 719; SHAM: 1802 ± 1730 ms2; P = 0.14) and it did not change in either condition (tVNSab: P = 0.56; SHAM: P = 0.89). HF was not different at PRE (tVNSab: 784 ± 505; SHAM: 1076 ± 692 ms2; P = 0.70) or during STIM (tVNSab: 1119 ± 804; SHAM: 1015 ± 711 ms2; P = 0.89) and it did not change in either condition (tVNSab: P = 0.46; SHAM: P = 0.99). SD1 was not different at PRE (tVNSab: 48 ± 46; SHAM: 46 ± 38 ms; P = 0.97) or during STIM (tVNSab: 52 ± 49; SHAM: 41 ± 25 ms; P = 0.13) and it did not change in either condition (tVNSab: P = 0.73; SHAM: P = 0.67). SD2 was not different at PRE (tVNSab: 108 ± 69; SHAM: 92 ± 48 ms; P = 0.55) or during STIM (tVNSab: 113 ± 60; SHAM: 105 ± 59 ms; P = 0.89) and it did not change in either condition (tVNSab: P = 0.97; SHAM: P = 0.70).ConclusionsThese preliminary data show that a single intervention of tVNSab did not reduce HR or alter HRV in healthy college‐aged adults during PB. Contrary to our hypotheses, these data indicate that tVNSab does not elicit changes to cardiac autonomic activity that reflect greater cardiac parasympathetic activity in young healthy adults.

The Effects of Acute Cannabidiol on Autonomic Balance

A recent poll indicates that at least one third of Vermont state’s population has used hemp‐based products such as Cannabidiol (CBD). This non‐psychoactive compound is one of 700 chemicals derived from the Cannabis sativa plant and is both legal and widespread for distribution in the state of Vermont, however very little work has been done to investigate its physiological effects at recreationally‐relevant doses. We hypothesized that in apparently healthy adults, acute CBD favorably affects the autonomic nervous system and that this would be evident by an increase in heart rate variability (HRV). HRV is a non‐invasive method used to analyze autonomic balance. Though scientific studies are lacking, anecdotal reports of athletes self‐administering CBD have indicated a positive effect on HRV. Using a randomized, double‐blind, placebo‐controlled crossover study, we examined a narrow age range of adults (average 20.9 ± 0.3 yrs), administered varying acute recreationally‐relevant doses of CBD (0, 25mg, 50mg, 200mg), and characterized baseline cardiovascular variables (heart rate, blood pressure, HRV) at rest. Results indicate that such doses do not affect resting heart rate or blood pressure, however increasing dose appears to increase standard deviation of interbeat intervals (SDNN) and root mean square of successive differences (RMSSD). Such changes reflect an increase in HRV, indicative of elevated parasympathetic activity. This work contributes to the framework of understanding potential therapeutic uses and/or risk factors of CBD, particularly as it relates to healthy individuals.

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.

Stress Management Intervention for Leaders Increases Nighttime SDANN: Results from a Randomized Controlled Trial.

Stress management interventions aim to reduce the disease risk that is heightened by work stress. Possible pathways of risk reduction include improvements in the autonomous nervous system, which is indexed by the measurement of heart rate variability (HRV). A randomized controlled trial on improving stress management skills at work was conducted to investigate the effects of intervention on HRV. A total of 174 lower management employees were randomized into either the waiting list control group (CG) or the intervention group (IG) receiving a 2-day stress management training program and another half-day booster after four and six months. In the trial, 24 h HRV was measured at baseline and after 12 months. Heart rate (HR), root mean square of successive differences (RMSSD), standard deviation of normal-to-normal intervals (SDNN), and standard deviation of the average of normal-to-normal intervals (SDANN) were calculated for 24 h and nighttime periods. Age-adjusted multilevel mixed effects linear regressions with unstructured covariance, time as a random coefficient, and time × group interaction with the according likelihood-ratio tests were calculated. The linear mixed-effect regression models showed neither group effects between IG and CG at baseline nor time effects between baseline and follow-up for SDANN (24 h), SDNN (24 h and nighttime), RMSSD (24 h and nighttime), and HR (24 h and nighttime). Nighttime SDANN significantly improved in the intervention group (z = 2.04, p = 0.041) compared to the control group. The objective stress axis measures (SDANN) showed successful stress reduction due to the training. Nighttime SDANN was strongly associated with minimum HR. Though the effects were small and only visible at night, it is highly remarkable that 3 days of intervention achieved a measurable effect considering that stress is only one of many factors that can influence HR and HRV.

Abstract P216: Association Of Heart Rate Variability With The Risk Of Heart Failure And Its Sub-types In Post-menopausal Women: A Longitudinal Cohort Study

Background: Previously our research findings revealed that low heart rate variability, a measure of autonomic imbalance, is associated with increased incidence of coronary heart disease (CHD) and heart failure (HF) in a cohort of post-menopausal women. Since CHD is strongly associated with HF, we investigated the effect of CHD on relationship of HRV and HF subtypes, i.e., heart failure with reduced ejection fraction (HFrEF) and heart failure with preserved ejection fraction (HFpEF), in post-menopausal women. Methods: Total of 28,603 post-menopausal women free of baseline CHD, HF and cardiac arrhythmias enrolled in Women’s Health Initiative (WHI) study, were followed for incident hospitalized CHD, HF and its subtypes (HFrEF vs HFpEF). Using multivariate cox proportional hazard model, we estimated the association of above outcomes with baseline quartiles of HRV measures; SDNN (standard deviation of normal-to-normal RR interval) and RMSSD (root mean square of successive difference of RR interval) produced by 10-second twelve-lead ECG on enrollment. We then evaluated the relationship between HRV and HF subtypes stratified by incident CHD. Results: A total of 2279 incident CHD and 1562 incident HF events occurred during a median follow-up duration of 17.5 years. After adjusting for incident CHD in a multivariate cox proportional model, association of low SDNN and RMSSD with incident HF remained significant (SDNN HR 1.19, CI 1.05 - 1.35; RMSSD HR 1.13 (1.00 - 1.29). However, in stratified analysis low SDNN was associated with increased incidence of HFpEF only among participants without incident CHD (HR 1.29, CI 1.05 - 1.58) and not in those with incident CHD (HR 1.06, CI 0.77 - 1.47). Whereas low SDNN was associated with increased incidence of HFrEF only among participants with incident CHD (HR 1.44. CI 1.05 - 1.98) and not in those without incident CHD (HR 1.18, CI 0.87 - 1.61). Conclusion: Post-menopausal women with low HRV who develop CHD have an increased risk of HFrEF while those who don’t develop CHD have an increased risk of HFpEF. The relationship between autonomic imbalance and HF subtypes is dependent on CHD status.

Towards better reliability in fetal heart rate variability using time domain and spectral domain analyses. A new method for assessing fetal neurological state?

ObjectivesFetal heart rate variability (FHRV) has shown potential in fetal surveillance. Therefore, we aimed to evaluate the reliability of time domain and spectral domain parameters based on non-invasive fetal electrocardiography (NI-FECG).MethodNI-FECG, with a sampling frequency of 1 kHz, was obtained in 75 healthy, singleton pregnant women between gestational age (GA) 20+0 to 41+0. The recording was divided into a) heart rate pattern (HRP) and b) periods fulfilling certain criteria of stationarity of RR-intervals, termed stationary heart rate pattern (SHRP). Within each recording, the first and the last time series from each HRP with less than 5% artifact correction were analyzed and compared. Standard deviation of normal-to-normal RR-intervals (SDNN), root mean square of successive differences (RMSSD), high frequency power (HF-power), low frequency power (LF-power), and LF-power/HF-power were performed. A multivariate mixed model was used and acceptable reliability was defined as intraclass correlation coefficient (ICC) ≥ 0.80 and a coefficient of variation (CV) ≤ 15%. Based on these results, the CV and ICC were computed if the average of two to six time series was used.ResultsFor GA 28+0 to 34+6, SDNN and RMSSD exhibited acceptable reliability (CV < 15%; ICC > 90%), whereas GA 35+0 to 41+0and 20+0 to 27+6 showed higher CVs. Spectral domain parameters also showed high CVs However, by using the mean value of two to six time series, acceptable reliability in SDNN, RMSSD and HF-power from GA 28+0 was achieved. Stationarity of RR-intervals showed high influence on reliability and SHRP was superior to HRP, whereas the length of the time series showed minor influence.ConclusionAcceptable reliability seems achievable in SDNN, RMSSD and HF-power from gestational week 28. However, stationarity of RR-intervals should be considered when selecting time series for analyses.

Low Heart Rate Variability Predicts Poor Overall Survival of Lung Cancer Patients With Brain Metastases.

BackgroundThe aim of this prospective study was to evaluate the association between heart rate variability (HRV) and overall survival of lung cancer patients with brain metastases (LCBM).MethodsFifty-six LCBM patients were enrolled in this study. Five-minute electrocardiograms were collected before the time to first brain radiotherapy. HRV was analyzed quantitatively by using the time domain parameters, i.e., the standard deviation of all normal-normal intervals (SDNN) and the root mean square of successive differences (RMSSD). Survival time for LCBM patients was defined as from the date of HRV testing to the date of death or the last follow-up.ResultsIn the univariate analysis, SDNN ≤ 13 ms (P = 0.003) and RMSSD ≤ 4.8 ms (P = 0.014) significantly predicted poor survival. Multivariate analysis confirmed that RMSSD ≤ 4.8 ms (P = 0.013, hazard ratio = 3.457, 95% confidence interval = 1.303–9.171) was also an independent negative prognostic factor after adjusting for mean heart rate, Karnofsky performance status, and number of brain metastases in LCBM patients.ConclusionDecreased RMSSD is independently associated with shorter survival time in LCBM patients. HRV might be a novel predictive biomarker for LCBM prognosis.

Characterizing the effect of incrementally increasing dry bulb temperature on linear and nonlinear measures of heart rate variability in nonpregnant, mid-gestation, and late-gestation sows.

Characterizing the sow physiological response to an increased heat load is essential for effective heat stress mitigation. The study objective was to characterize the effects of a 400-min heating episode on sow heart rate variability (HRV) at different reproductive stages. HRV is a commonly used noninvasive proxy measure of autonomic function. Twenty-seven sows were enrolled in the study according to their gestation stage at time of selection: 1) nonpregnant (NP; n = 7), 2) mid-gestation (MID; 57.3±11.8 d gestation; n = 11), and 3) late-gestation (LATE; 98.8±4.9 d gestation; n = 8). The HRV data utilized in the study were collected from each pig as the dry bulb temperature in the room increased incrementally from 19.84±2.15 °C to 35.54±0.43 °C (range: 17.1-37.5 °C) over a 400-min period. After data collection, one 5-min set of continuous heart rate data were identified per pig for each of nine temperature intervals (19-20.99, 21-22.99, 23-24.99, 25-26.99, 27-28.99, 29-30.99, 31-32.99, 33-34.99, and 35-36.99 °C). Mean inter-beat interval length (RR), standard deviation of r-r intervals (SDNN), root mean square of successive differences (RMSSD), high frequency spectral power (HF), sample entropy (SampEn), short-term detrended fluctuation analysis (DFAα1), and three measures (%REC, DET, LMEAN) derived from recurrence quantification analysis were calculated for each data set. All data were analyzed using the PROC GLIMMIX procedure in SAS 9.4. Overall, LATE sows exhibited lower RR than NP sows (P < 0.01). The standard deviation of r-r intervals and RMSSD differed between each group (P < 0.01), with LATE sows exhibiting the lowest SDNN and RMSSD and NP sows exhibiting the greatest SDNN and RMSSD. Late-gestation sows exhibited lower HF than both MID and NP sows (P < 0.0001), greater DFA values than NP sows (P = 0.05), and greater DET compared to MID sows (P = 0.001). Late-gestation also sows exhibited greater %REC and LMEAN compared to MID (P < 0.01) and NP sows (all P < 0.01). In conclusion, LATE sows exhibited indicators of greater autonomic stress throughout the heating period compared to MID and NP sows. However, temperature by treatment interactions were not detected as dry bulb increased. Future studies are needed to fully elucidate the effect of gestational stage and increasing dry bulb temperature on sow HRV.

Study of heart rate variability to assess autonomic dysfunction in patients with chronic obstructive pulmonary disease of a tertiary care hospital of West Bengal: A cross-sectional comparative study

Background: Chronic obstructive pulmonary disease (COPD) is one of the major causes of morbidity and mortality throughout the world. COPD and its complications also lead to a large number of deaths every year in our country. Cardiac arrhythmias and sudden cardiac death are the major complications of COPD leading to death and disability. Such cardiac complications are often a result of autonomic dysfunction. Aims and Objectives: This study aims to find out the autonomic dysfunction in moderate COPD patients by comparing their heart rate variability (HRV) parameters with age and sex matched healthy controls. Materials and Methods: After obtaining approval from the Institutional Ethics Committee, 48 patients of moderate COPD and 54 healthy subjects were assessed and compared with respect to their HRV parameters which included Mean RR, Mean HR, SDNN, NN50, pNN50, root mean square of successive differences (RMSSD), high frequency (HF), low frequency (LF), LF/HF ratio, and SD2/SD1 ratio. Results: It was found that in comparison to healthy controls, patients of moderate COPD had significant alteration in the following HRV parameters – Mean HR (P: 0.001), RMSSD (P: 0.002), SDNN (P: 0.015), NN50 (P: 0.001), pNN50 (P: 0.000), HF (NU/normalized unit) [P: 0.033], HF (%) [P: 0.002], LF (NU/normalized unit) [P: 0.033], LF (%) [P: 0.012], and LF/HF (P: 0.033). Conclusion: As there is a significant alteration of several HRV parameters in moderate COPD patients, we conclude that HRV measurement may subserve as a simple and non-invasive tool to assess autonomic dysfunction in patients of COPD at the earliest.

Efficacy of Non-contact BallistocardiographySystem to Determine Heart Rate Variability.

Background:Functions of the autonomic nervous system have cardinal importance in day-to-day life. Heart rate variability (HRV) has been shown to estimate the functioning of the autonomic nervous system. Imbalance in the functioning of the autonomic nervous system is seen to be associated with chronic conditions such as chronic kidney disease, cardiovascular diseases, diabetes mellitus, and so on.Purpose:To evaluate the efficacy of a non-contact ballistocardiography (BCG) system to calculate HRV parameters by comparing them to the parameters derived from a standard commercial software that uses an electrocardiogram (ECG).Methods:Current study captured an ECG signal using a three-channel ECG Holter machine, whereas the BCG signal was captured using a BCG sensor sheet consisting of vibroacoustic sensors placed under the mattress of the participants of the study.Results:The study was conducted on 24 subjects for a total of 54 overnight recordings. The proposed method covered 97.92% epochs of the standard deviation of NN intervals (SDNN) and 99.27% epochs of root mean square of successive differences (RMSSD) within 20 ms and 30 ms tolerance, respectively, whereas 98.84% of two-min intervals for low-frequency (LF) to high-frequency (HF) ratio was covered within a tolerance of 1. Kendall’s coefficient of concordance was also calculated, giving a P < .001 for all the three parameters and coefficients 0.66, 0.55, and 0.44 for SDNN, RMSSD, and LF/HF, respectively.Conclusion:The results show that HRV parameters captured using unobtrusive and non-invasive BCG sensors are comparable to HRV calculated using ECG.

Association of preprocedural ultrashort-term heart rate variability with clinical outcomes after transcatheter aortic valve replacement: A nested, case-control, pilot study.

ABSTRACTBackground:Because heart rate variability (HRV) has been linked to important clinical outcomes in various cardiovascular disease states, we investigated whether preprocedural ultrashort-term HRV (UST-HRV) differs between 1-year survivors and nonsurvivors after transcatheter aortic valve replacement (TAVR).Methods:In our single-center, retrospective, nested pilot study, we analyzed data from patients with severe aortic stenosis undergoing TAVR. All patients had preprocedural UST-HRV measured before the administration of any medications or any intervention. To investigate whether preprocedural HRV is associated with 1-year survival, we performed a logistic regression analysis controlling for Kansas City Cardiomyopathy Questionnaire 12 score.Results:In our parent cohort of 100 patients, 42 patients (28 survivors and 14 nonsurvivors) were included for analysis. Root mean square of successive differences (RMSSD) and standard deviation of NN intervals (SDNN) were lower in patients who survived to 1-year post TAVR compared to nonsurvivors [10 (IQR 8–23) vs 23 (IQR 17–33), P = 0.04 and 10 (IQR 7–16) vs 17 (IQR 11–40), P = 0.03, respectively]. Logistic regression demonstrated a trend in the association of preprocedure RMSSD with 1-year mortality and a 5% higher risk of 1-year mortality with each unit increment in UST-HRV using SDNN (OR 1.05; 95%CI 1.01–1.09, P = 0.02).Conclusion:Our data suggest an inverse relationship between preprocedural UST-HRV and 1-year survival post-TAVR. This finding highlights the potential complexity of HRV regulation in chronic vs acute illness. Prospective studies are needed to validate our findings and to determine whether UST-HRV can be used for risk stratification in patients with severe aortic stenosis.

Relationship Between Heart Rate Variability and Pulse Rate Variability Measures in Patients After Coronary Artery Bypass Graft Surgery.

Background: Heart rate variability (HRV) and pulse rate variability (PRV) measures are two kinds of physiological indices that can be used to evaluate the autonomic nervous function of healthy subjects and patients with various kinds of illness.Purpose: In this study, we compared the agreement and linear relationship between electrocardiographic signals (ECG)-derived HRV and photoplethysmographic signals (PPG)-derived right hand PRV (R-PRV) and left hand PRV (L-PRV) measures in 14 patients over 1 year after coronary artery bypass graft (CABG) surgery.Method: The ECG and PPG signals of the patient were recorded simultaneously for 10 min in a supine position. The last 512 stationary RR intervals (RRI) and peak-to peak intervals (PPI) of pulse wave were derived for data analysis. Bland-Altman plot was used to assess the agreement among HRV and both hand PRV measures, while linear regression analysis was used to examine the relationship among corresponding measures of HRV, R-PRV, and L-PRV.Result: The results revealed significant differences in total power (TP), very low-frequency power (VLF), low-frequency power (LF), high-frequency power (HF), and normalized VLF (VLFnorm) among HRV, R-PRV, and L-PRV. Bland-Altman plot analysis showed good agreements in almost all measures between R-PRV and L-PRV, except insufficient agreement was found in LF/HF. Insufficient agreements were found in root mean square successive difference (RMSSD), normalized HF (HFnorm), and LF/HF indices between HRV and L-PRV, and in VLFnorm, HFnorm, and LF/HF indices between HRV and R-PRV. Linear regression analysis showed that the HRV, R-PRV, and L-PRV measures were all highly correlated with one another (r = 0.94 ~ 1; p < 0.001).Conclusion: Though PRV measures of either hand are not surrogates of HRV measures, they might still be used to evaluate the autonomic nervous functions of CABG patients due to the moderate to good agreements in most time-domain and frequency-domain HRV measures and the strong and positive correlations among HRV and both hands PRV measures in CABG patients.

The Effect of Forest Video Using Virtual Reality on the Stress Reduction of University Students Focused on C University in Korea

The purpose of this study is to study the effect of forest videos using virtual reality (VR) on the stress of college students. The study subjects were 60 college students who watched two-dimensional (2D) and VR videos, and we compared their control heart rate variability (HRV) and electroencephalogram (EEG). As a result, it was found that the VR group had a positive effect on high frequency (HF), standard deviation of all NN intervals (SDNN), and root-mean-square of successive differences (RMSSD) compared with the control group, and the VR group had a positive effect on HF compared with the 2D group. Second, EEG, a physiological indicator, showed statistical differences in Relative Alpha Power (RA), Relative Beta Power (RB), and Ratio of SMR–Mid Beta to Theta (RSMT) in VR groups in intra-group analysis. Among them, it was investigated that watching forest videos on VR became a state of concentration and immersion due to the increase in RSMT. As a result of the above, it was investigated that forest videos using VR had a positive effect on the physiological stress on college students. Therefore, it is expected that a positive effect will occur if VR is used as an alternative to stress management for college students.

Association of lower heart rate variability with neuroimaging markers for dementia‐related pathology: The Multi‐Ethnic Study of Atherosclerosis (MESA)

AbstractBackgroundLower heart rate variability (HRV), indicating worse cardiac autonomic function, is associated with cardiovascular risk factors for dementia. We hypothesized that lower HRV would be associated with neuroimaging biomarkers for dementia‐related pathology independent of cardiovascular risk factors.MethodDuring MESA Exam 6 (2016‐19), 256 white and African‐American Wake Forest site participants completed 3T brain MRI, and 159 further completed Aβ‐PET imaging. HRV was calculated as standard deviation of normal‐to‐normal intervals (SDNN) and root mean square of successive differences (RMSSD) from 10‐second electrocardiogram at Exam 1 (2000‐02) and Exam 5 (2010‐12). We related continuous (log2‐normalized) HRV to neuroimaging parameters including mean temporal lobe cortical thickness, neurite orientation dispersion and density imaging (NODDI) free water in gray (gmFW) and white matter (wmFW), and presence of cerebral microbleeds (CMBs), lacunes, and Aβ positivity (Pittsburgh Compound B SUVR ≥1.21) using multivariable linear and logistic regression, and examined race and sex interactions. To account for potential non‐linearity, we also considered the association of lowest quartile HRV to neuroimaging markers. Regression coefficients (β [95% CI]; standard deviation units) and odds ratios (OR [95% CI]) are adjusted for age, race, sex, education, systolic blood pressure, body mass index, smoking, hypertension medication use, diabetes, and APOE genotype.ResultIn 254 participants (Exam 6 age 72.2±6.9 years; 58.7% female; 47.2% white) with HRV measurements, lower continuous Exam 1 SDNN (β = ‐0.23 [‐0.39, ‐0.07]) and RMSSD (β = ‐0.19 [‐0.33, ‐0.05]) were associated with higher wmFW. Interactions showed that CMBs were associated with lowest quartile Exam 1 SDNN (OR = 3.76 [1.15, 12.25]) and Exam 5 RMSSD (OR = 3.36 [1.07, 10.54]) in males only (sex interaction P&lt;0.001), and with Exam 1 SDNN (OR = 2.58 [1.04, 6.45]) in African‐Americans only (race interaction P = 0.039). Lower HRV was not associated with cortical thickness or presence of lacunes. In 152 participants with Aβ‐PET, no associations with Aβ deposition were found.ConclusionLower HRV from up to 16 years prior may be associated with increased neuroinflammation as measured by free water in older adults. Associations between HRV and cerebral small vessel disease markers may differ by sex or race.

Prolonged Video-EEG and Heart Rate Variability can Elucidate Autonomic Dysregulation in Infantile Apneic Seizures

BackgroundInfantile apneic seizures (IASs) are unexpected life-threatening events. We aimed to determine the utility of prolonged video-electroencephalography (vEEG) and heart rate variability (HRV) in IAS. MethodsThe study included seven infants with apneic seizures captured by vEEG, percutaneous oxygen saturation (SpO2), and electrocardiography (ECG). Interictal, preictal, and postictal HRV of patients and N2 sleep HRV of 10 age-matched controls were determined. ResultsWe analyzed seven vEEGs (duration = 17 to 87 hours) of seven patients aged three to 13 months (mean onset age of apneic event = 6.3 months). Fifteen apneic seizures (one to five per infant) were captured. The initial apneic seizure was captured at 7.5 to 76 hours (mean = 36.6 hours) after vEEG initiation. Ictal rhythmic delta/theta/fast waves were seen over temporal (five patients), central (one), and diffuse areas (one). Ictal SpO2 decreased between 1.5% and 90% (mean = 47.9%). Ictal decreased heart rate (HR) (six seizures) and ictal increased HR (14) was detected. Both decreased and increased HR was observed (five). The preictal low-frequency (LF)/high-frequency (HF) ratio was significantly higher than the interictal LF/HF ratio (P = 0.048). Preictal (P = 0.048), and postictal (P = 0.019) root mean square of successive differences (RMSSDs) of patients were lower than the sleep RMSSD of controls. These results indicated dominant sympathetic activity. RMSSD from interictal to preictal periods tended to be higher in IAS with decreased HR than in IAS with increased HR alone (P = 0.066). The postictal RMSSD showed tendency to be higher in IAS with decreased HR than in IAS with increased HR alone (P = 0.088). The decreased HR and increased RMSSD suggested not only sympathetic activity but also escalated parasympathetic activity in IAS. ConclusionsInfants with unexpected apneic events should be monitored with prolonged vEEG, SpO2, and ECG. Abnormal HRV in infants with apneic seizures might indicate additional autonomic dysregulation in IAS.

Single Slow-Paced Breathing Session at Six Cycles per Minute: Investigation of Dose-Response Relationship on Cardiac Vagal Activity.

The practice of slow-paced breathing (SPB) has been linked to a range of positive outcomes, such as decreasing symptoms of depression, anxiety, and stress, as well as increasing well-being. Among the suggested mechanisms of action, SPB has been shown to increase cardiac vagal activity (CVA). The present study aimed to investigate whether there is a dose-response relationship modulating the effects of SPB on CVA. A total of 59 participants were involved in this study. In a within-subject design, participants attended the lab five times, and realized SPB at six cycles per minute with different durations (5, 10, 15, and 20 min), as well as a control condition without SPB. CVA was indexed via the root mean square of successive differences (RMSSD). During SPB, findings showed an increase in RMSSD in all conditions compared to the control condition. However, no differences were found in RMSSD among the different session durations, during SPB or during the resting measurement completed immediately after SPB. Noteworthily, session duration showed an influence on the spontaneous respiratory frequency in the resting measurement occurring immediately after SPB. Specifically, respiratory frequency appears to decrease with session duration, thus potentially contributing to additional relaxing effects.

Cardiac and Autonomic Dysfunctions Assessed Through Recurrence Quantitative Analysis of Electrocardiogram Signals and an Application to the 6-Hydroxydopamine Parkinson's Disease Animal Model.

A classic method to evaluate autonomic dysfunction is through the evaluation of heart rate variability (HRV). HRV provides a series of coefficients, such as Standard Deviation of n-n intervals (SDNN) and Root Mean Square of Successive Differences (RMSSD), which have well-established physiological associations. However, using only electrocardiogram (ECG) signals, it is difficult to identify proper autonomic activity, and the standard techniques are not sensitive and robust enough to distinguish pure autonomic modulation in heart dynamics from cardiac dysfunctions. In this proof-of-concept study we propose the use of Poincaré mapping and Recurrence Quantification Analysis (RQA) to identify and characterize stochasticity and chaoticity dynamics in ECG recordings. By applying these non-linear techniques in the ECG signals recorded from a set of Parkinson’s disease (PD) animal model 6-hydroxydopamine (6-OHDA), we showed that they present less variability in long time epochs and more stochasticity in short-time epochs, in their autonomic dynamics, when compared with those of the sham group. These results suggest that PD animal models present more “rigid heart rate” associated with “trembling ECG” and bradycardia, which are direct expressions of Parkinsonian symptoms. We also compared the RQA factors calculated from the ECG of animal models using four computational ECG signals under different noise and autonomic modulatory conditions, emulating the main ECG features of atrial fibrillation and QT-long syndrome.

Relationship between heart rate variability and body mass index: A cross-sectional study of preschool children

Reduced heart rate variability (HRV) is associated with overweight and obesity in adults. However, little is known about this relationship in early childhood. We investigated the relationship between resting vagally-mediated HRV and body mass index (BMI) in Australian preschool children. Children were recruited from 13 non-government early learning centres located in Queensland and New South Wales, Australia. From this population-based sample, data from 146 healthy children (58 females) between 3 and 5 years of age (mean age 4.35 ± 0.44 years) were analysed. BMI was calculated from child body weight and height. Physical activity was recorded using an Actigraph wGT3x accelerometer worn at the waist of participants over 3 consecutive days. A Polar H10 chest strap measured seated, resting RR intervals for the calculation of HRV with the root mean square of successive differences (RMSSD) reflecting vagally-mediated activity. The relationship between HRV and BMI was analysed using a linear mixed model adjusted for age, sex and physical activity. Analysis revealed that RMSSD (ln) demonstrated a significant inverse relationship with BMI (β = -0.06; 95% CI = -0.12 – −0.01; p = 0.032), and the model accounted for 23% of the variance in RMSSD (ln). Notably, a one unit increase in BMI resulted in a reduction in RMSDD (ln) of 0.06. This investigation demonstrated evidence for a significant inverse linear relationship between vagally-mediated HRV and BMI in 3 – 5-year-old Australian children, similar to that of adults. Furthermore, this relationship was independent of age, sex and physical activity levels. Results may indicate that the cardiometabolic health of preschool children is, in part, influenced by the relationship between vagally-mediated HRV and weight status.

Heart rate variability and psychosocial symptoms in adolescents and young adults with cancer.

Heart Rate Variability (HRV) is a valid, scalable biomarker of stress. We aimed to examine associations between HRV and psychosocial outcomes in adolescents and young adults (AYAs) with cancer. This was a secondary analysis of baseline data from a randomized trial testing a resilience intervention in AYAs with cancer. Two widely used HRV metrics, the standard deviation of normal to normal beats (SDNN) and root mean square of successive differences (RMSSD), were derived from electrocardiograms. Patient-reported outcome (PRO) survey measures included quality of life, anxiety, depression, distress, and resilience. Linear regression models were used to test associations between HRV and PRO scores. The Wilcoxon rank sum test was used to test differences in median HRV values among participant subgroups. Among the n = 76 patients with available electrocardiograms, the mean age was 16 years (SD 3y), 63% were white, and leukemia/lymphoma was the most common diagnosis. Compared to healthy adolescents, AYAs with cancer had lower median HRV (SDNN [Females: 31.9 (12.8-50.7) vs 66.4 (46.0-86.8), p<0.01; Males: 29.9 (11.5-47.9) vs 63.2 (48.4-84.6), p<0.01]; RMSSD [Females: 28.2 (11.1-45.5) vs 69.0 (49.1-99.6), p<0.01; Males: 27.9 (8.6-48.6) vs 58.7 (44.8-88.2), p<0.01]). There was no statistically significant association between PRO measures and SDNN or RMSSD in either an unadjusted or adjusted linear regression models. In this secondary analysis, we did not find an association between HRV and psychosocial PROs among AYAs with cancer. HRV measures were lower than for healthy adolescents. Larger prospective studies in AYA biopsychosocial research are needed.

Differences in Nervous Autonomic Control in Response to a Single Session of Exercise in Bodybuilders Using Anabolic Androgenic Steroids.

Considering the role of autonomic nerve activity in blood pressure control, this study aimed to investigate the cardiac autonomic nerve responses after an aerobic exercise session in Anabolic Androgenic Steroids (AAS) users. Twenty men (AAS, n = 9; control group, n = 11) performed an aerobic exercise session (60 min, 70 to 80% of HRmax). Heart rate variability (HRV) was assessed before and during a 60-min post-exercise recovery period. RMSSD (root mean square successive difference of the RR intervals) and the LF/HF ratio (low frequency/high frequency spectra) were also evaluated. The Student's t-test for independent samples was used to compare differences between initial group characteristics. Repeated measures ANOVA was used to compare pre- and post-exercise HRV recovery (p < 0.05). AAS had a lower SDNN (standard deviation of the intervals) (40.8 ± 16.8 vs. 71.6 ± 24.7 ms; p = 0.04, d = 1.4) and a higher LF/HF (3.4 ± 2.1 vs. 1.8 ± 0.9%; p = 0.03, d = 0.9) before exercise. AAS and controls had similar RMSSD (14.0 ± 15.8 vs. 18.9 ± 12.1 ms; p = 0.20) and a LF/HF (2.8 ± 1.6 vs. 2.4 ± 1.2 ms; p = 0.41) immediately post-exercise. The between-groups comparison revealed a higher HF/LF at 30 min (4.3 ± 1.4 vs. 2.5 ± 1.3%; p = 0.008, d = 1.3) and 60 min (5.0 ± 2.2 vs. 2.3 ± 0.8%; p = 0.001, d = 1.6) for the AAS group in the recovery time. This study demonstrated impaired parasympathetic activity at rest and immediately after the exercise session as an adverse effect of AAS usage, but similar behavior regarding the restoration of sympathetic activity.