Acute cardiac autonomic and hemodynamic responses to resistive breathing: Effect of loading type and intensity

OBJECTIVES

This study aimed to assess the acute impact of distinct loading breathing types and intensities on cardiac autonomic function and hemodynamic responses in healthy young adults.

METHODS

A randomized, crossover trial involved 28 participants who underwent inspiratory resistive breathing, expiratory resistive breathing (ERB) and combined resistive breathing, each at 30% and 60% of maximal respiratory pressures. Data on heart rate variability (HRV) and hemodynamic parameters were collected during each trial.

RESULTS

The study revealed significant main and interaction effects for both the performed task and the intensity across all measured variables (all p < 0.001). ERB at 60% load demonstrated significantly higher HRV values in the standard deviation of normal-to-normal RR intervals, the square root of the mean squared difference of successive normal-to-normal RR intervals and high-frequency power, as well as significantly lower values in heart rate, stroke volume, stroke volume index, cardiac output, cardiac index, end-diastolic volume and end-diastolic volume index, compared to other loaded protocols (all p < 0.001).

CONCLUSION

These findings highlight the acute effect of type-specific and load-dependent resistive breathing on cardiac autonomic and hemodynamic functions, where ERB at 60% intensity showed the most significant cardiovagal modulation while causing the least hemodynamic alterations.

Effects of continuous supplementation of Acanthopanax senticosus Harms on the cardiac autonomic function of community-dwelling elderly individuals during resting and standing tests: a randomized controlled trial

Background

Cardiac autonomic function (CAF) decreases with aging, and Acanthopanax senticosus Harms (ASH) consumption reportedly induces anti-stress effects. This study aimed to assess the effect of continuous supplementation of ASH on CAF during resting and standing tests in the elderly population.

Methods

This double-blind, randomized controlled trial was conducted in the morning in a laboratory setting and was carried out between June 2017 and July 2017 at Kambaikan, Doshisha University (Karasuma-higashi-iru, Imadegawa-dori, Kamigyo-ku, Kyoto 602-8580, Japan). In total, 28 community-dwelling elderly individuals (mean ± standard deviation = 72.5 ± 4.5 years) were included. Each subject was instructed to consume ASH or placebo supplements twice daily for 4 weeks. An autonomic reflex orthostatic tolerance recorder was used to measure CAF in pre- and post-intervention phases. Parameters were measured in a seated position and included coefficient of variation of R-R intervals (CVRR), low frequency (LF), high frequency (HF), LF/HF ratio, blood pressure, and heart rate (HR). Changes in each parameter were evaluated before and after standing. All parameters were defined as the difference between the mean value obtained in a standing position for 2 min and that obtained in a 2-min seated position.

Results

A two-way analysis of variance revealed a significant group-time interaction effect on CVRR, HF, and ΔLF/HF ratio. Following the intervention, CVRR, HF, LF/HF ratio, systolic blood pressure (SBP), HR, ΔLF/HF ratio, ΔSBP, and ΔHR improved significantly in the ASH group only.

Conclusions

Four-week supplementation of ASH improved CAF in community-dwelling elderly individuals during resting and standing tests.

Clinical Trial Registration

https://center6.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000031218, UMIN Clinical Trials Registry (UMIN000027251).

Heart Rate and Heart Rate Variability in Healthy Preterm-Born Young Adults and Association with Vitamin D: A Wearable Device Assessment

Prematurity has been associated with impaired parasympathetic cardiac regulation later in life. Changes in heart rate (HR) and heart rate variability (HRV) may indicate a risk for future cardiac dysfunction. The putative role of Vitamin D on cardiac autonomic function in individuals born preterm (PT) remains unknown. This study involves monitoring autonomic cardiac regulation and Vitamin D concentrations in 30 PT and 16 full-term (FT) young adults in a free-living context. The PT subjects were born between 1994 and 1997 at Oulu University Hospital. The inclusion criteria were (1) being born ≤ 32 gestation weeks or (2) being born < 34 gestation weeks with a birth weight under 1500 g. Participants wore an Oura ring sleep tracer, a smart ring device, for 2 weeks to monitor cardiac autonomic function. Parameters related to autonomic cardiac regulation, lowest nighttime resting HR, and the root mean square of successive differences (RMSSD) to describe HRV were collected. PT males exhibited a tendency toward lower RMSSD (71.8 ± 22.6) compared to FT males (95.63 ± 29.0; p = 0.10). Female participants had a similar mean RMSSD in the FT and PT groups at 72.04 ± 33.2 and 74.0 ± 35.0, respectively. Serum 25-hydroxyvitamin D concentration did not correlate with cardiac autonomic function parameters. When assessing the lowest resting nighttime HRs and HRVs in a long-term, real-world context, healthy female PT young adults performed similarly to their FT peers. In contrast, the present study's results suggest that male PT young adults exhibit impaired autonomic cardiac function, potentially putting them at risk for cardiovascular disease later in adulthood.

Effect of cardiac rehabilitation therapy on depressed patients with cardiac insufficiency after cardiac surgery

This study aims to analyze the effect of cardiac rehabilitation therapy on cardiac autonomic nervous function in patients with cardiac insufficiency complicated with anxiety depression after cardiac operation to provide a reference for clinical practice. A total of 109 patients subject to cardiac operation in our hospital from January 2020 to March 2023 were enrolled as study subjects, including 50 patients who received conventional rehabilitation therapy (control group) and 69 patients who received cardiac rehabilitation therapy (research group). Before and after treatment, the left ventricular ejection fraction (LVEF) and central venous pressure (CVP) were determined, and the level of N-terminal pro-B-type natriuretic peptide (NT-proBNP) was measured. Low frequency/high frequency (LF/HF), standard deviation of normal to normal (SDNN), and root mean of successive square differences (RMSSD) were measured by a multi-lead ECG system. Self-rating Anxiety Scale (SAS), Self-rating Depression Scale (SDS), Pittsburgh Sleep Quality Index (PSQI), Activity of daily living (ADL), and Barthel Index (BI) were applied for corresponding investigations, as well as the 6-min walk test (6MWT). After treatment, the research group showed higher LVEF, CVP, LF/HF, SDNN, and RMSSD, and lower NT-proBNP, SAS, and SDS than the control group (P < 0.05). Significantly elevated ADL score, BI, and 6MWT and reduced PSQI were observed in both groups after treatment, with more remarkable changes in the research group (P < 0.05). In conclusion, cardiac rehabilitation therapy effectively improved the cardiac function of patients with cardiac insufficiency complicated with anxiety and depression after the cardiac operation and alleviated their negative emotions.

Cardiac Autonomic Activity, Personality Traits, and Academic Performance in First-Year Medical Students: A Gender-Specific Relation

Background It is not always the sincere or hardworking or intelligent student that gets the highest grades. Exploring unknown dimensions that may distinguish academic performance in adolescents/youth migrating from a high school study environment to that of a professional school and in a learning environment without parental supervision for the first time remains important. We hypothesized that cardiac autonomic activity influenced by cognitive domain factors and emotions would predict academic success in them. Further, we investigated which of their personality traits related to academic performance. Exploratory gender-based analysis was included. Methods A prospective cohort study measured first-year medical students' resting heart rate, heart rate variability (HRV), and personality traits (from the self-reported NEO Five-Factor Inventory-3). Spearman's correlation coefficient tested the correlation between the year-end final aggregate marks and assessed parameters, including subgroup analysis based on gender. Regression analyses of variables with academic marks were performed in the entire cohort. Results The aggregate marks of 81 volunteering students (Mage = 18.7, SD = 0.8 years; 42 females, 39 males) as a cohort did not correlate with their resting heart rate or HRV indices. Subgroup analysis revealed a positive correlation between marks and high-frequency power (r = 0.33, p= 0.03) and total power (r = 0.37, p= 0.02) of HRV in females. The marks positively correlated with the personality conscientiousness score (r = 0.32, p= 0.04) and extraversion score (r = 0.34, p= 0.03) in females. Multivariable regression analysis in the entire cohort revealed no significant interactions. Conclusion Academic performance was significantly related to cardiac autonomic modulation and personality traits of conscientiousness and extraversion in female but not male first-year medical students. These results indicate a gender-specific difference in the relation between scholastic performance and HRV in adolescents/youth transiting from high school to professional schools and entering a study environment without parental supervision for the first time. Further our data expands the knowledge base of educational psychology among them.

Cardiovascular response to brisk walking on different surfaces in an innovative senior playground: a randomized trial in older adults

Brisk walking is a simple exercise for older adults. We aimed to assess the cardiovascular response to a short bout of brisk walking on walking loops in an innovative senior playground in Thailand. Twenty older adults were randomly assigned to brisk walking on artificial turf (AT group, n = 10) or an uneven surface (US group, n = 10). We assessed cardiovascular parameters, average walking speed, and rate of perceived exertion. Blood pressure, heart rate, rate-pressure product, and rate perceived exertion were significantly increased, while the mean RR interval of heart rate variability was significantly decreased in both AT and US groups after exercise compared with pre-exercise (p < 0.05). A greater change in systolic blood pressure was observed in the US group than in the AT group (p < 0.05). These data indicated that brisk walking on AT and US increases cardiovascular response. Our findings provide information on planning exercise programs for older adults.

Assessment of Cardiac Autonomic Function in Women With Polycystic Ovary Syndrome Through Ewing's Battery, Heart Rate Variability Analysis, and Composite Autonomic Symptom Score-31 Scale

Introduction Polycystic ovary syndrome (PCOS) is a frequently occurring endocrine condition prevalent in women of reproductive age characterized by chronic anovulation, hyperandrogenism, insulin resistance, and a low-grade inflammatory state. Patients with PCOS are more vulnerable to developing cardiac and metabolic co-morbidities. Sympathetic overactivity is also reported in PCOS patients. Objective This study aimed to assess cardiac autonomic function in PCOS by Heart Rate Variability Analysis, Ewing's Test, and Composite Autonomic Symptom Scale-31 (COMPASS-31). Methods Thirty female PCOS patients and 30 age-matched control females were enrolled in the study. Both cases and controls were subdivided into sub-groups based on body mass index (BMI) and waist-to-hip ratio (WHR). The cardiac autonomic functions were assessed by the COMPASS-31 questionnaire, Ewing's battery tests, and short-term heart rate variability analysis. Results There was no significant difference in age, BMI, and WHR of both groups. Additionally, cases had a significantly higher low frequency to high frequency (LF/HF) ratio and COMPASS-31 score and also reported more derangement in Ewing's battery test, indicating cardiac autonomic dysfunction in PCOS patients. Conclusion Patients with PCOS are more prone to developing cardiac and metabolic co-morbidities. Early assessment of cardiac autonomic function can prevent future complications with timely interventions. Altered autonomic function in PCOS patients can be due to hyperandrogenism and insulin resistance.

The Cardiac Comeback-Beating Stronger: Exploring the Remarkable Resilience of the Heart in COVID-19 Recovery through Cardiac Autonomic Analysis

Background and Objectives: Analyzing the cardiac autonomic function in COVID-19 patients can provide insights into the impact of the virus on the heart's regulatory mechanisms and its recovery. The autonomic nervous system plays a crucial role in regulating the heart's functions, such as heart rate, blood pressure, and cardiac output. This study aimed to investigate the impact of COVID-19 on heart rate variability (HRV) during a 6-min walk test (6MWT). Materials and Methods: The study included 74 participants, consisting of 37 individuals who had recovered from mild to moderate COVID-19 and 37 healthy controls. The study assessed heart rate variability (HRV) and blood pressure both before and after a 6-min walk test (6MWT). Results: The study found significant differences in a few time domains (SDNN and pNN50) and all frequency domain measures, whereas there were no significant differences in demographic characteristics or blood pressure between COVID-19-recovered individuals and healthy controls at rest. There were significant 6MWT effects on average HR, time-domain (SDNN and pNN50) measures of HRV, and all frequency domain measures of HRV. A significant group × 6MWT interaction was found for SDNN, pNN50, total power, Ln total power, LF, HF, Ln LF, Ln HF, and LF nu. Conclusions: Cardiac Autonomic analysis through HRV is essential to ensure the continued health and well-being of COVID-19 survivors and to minimize the potential long-term impacts of the disease on their cardiovascular system. This suggests that HRV analysis during the recovery phase following exercise could serve as a valuable tool for evaluating the physiological effects of COVID-19 and monitoring the recovery process.

Observational and genetic evidence support a relationship between cardiac autonomic function and blood pressure

Background

It is unclear how cardiac autonomic function, as indicated by heart rate (HR), heart rate variability (HRV), HR increase during exercise, and HR recovery after exercise, is related to blood pressure (BP). We aimed to examine the observational and genetic evidence for a potential causal effect of these HR(V) traits on BP.

Methods

We performed multivariable adjusted linear regression using Lifelines and UK Biobank cohorts to investigate the relationship between HR(V) traits and BP. Linkage disequilibrium score regression was conducted to examine genetic correlations. We used two-sample Mendelian randomization (2SMR) to examine potential causal relations between HR(V) traits and BP.

Results

Observational analyses showed negative associations of all HR(V) traits with BP, except for HR, which was positively associated. Genetic correlations were directionally consistent with the observational associations, but most significant genetic correlations between HR(V) traits and BP were limited to diastolic blood pressure (DBP). 2SMR analyses suggested a potentially causal relationship between HR(V) traits and DBP but not systolic blood pressure (SBP). No reverse effect of BP on HR(V) traits was found. One standard deviation (SD) unit increase in HR was associated with a 1.82 mmHg elevation of DBP. In contrast, one ln(ms) unit increase of the root mean square of the successive differences (RMSSD) and corrected RMSSD (RMSSDc), decreased DBP by 1.79 and 1.83 mmHg, respectively. For HR increase and HR recovery at 50 s, every additional SD increase was associated with a lower DBP by 2.05 and 1.47 mmHg, respectively. Results of secondary analyses with pulse pressure as outcome were inconsistent between observational and 2SMR analyses, as well as between HR(V) traits, and therefore inconclusive.

Conclusion

Both observational and genetic evidence show strong associations between indices of cardiac autonomic function and DBP, suggesting that a larger relative contribution of the sympathetic versus the parasympathetic nervous system to cardiac function may cause elevated DBP.

Effects of Preoperative Sarcopenia-Related Parameters on Cardiac Autonomic Function in Women with Obesity Following Bariatric Surgery: A One-Year Prospective Study

OBJECTIVES

Investigate changes in blood pressure (BP) and heart rate variability (HRV) in women with and without sarcopenia-related parameters who underwent bariatric surgery (BS) during a one-year follow-up.

SUBJECTS AND METHODS

Women were separated into obesity (OB, n = 20) and women with obesity displaying sarcopenia-related parameters (SOP, n = 14) and evaluated before BS and 3, 6, and 12 months after BS. SOP was defined as low handgrip strength (HS) and/or low appendicular skeletal mass adjusted for weight (ASM/wt × 100, %) in the lowest quartile of the sample. ASM/wt × 100, % and HS were significantly lower in SOP than OB over a one-year follow-up of BS (p < 0.05).

RESULTS

There was a reduction in diastolic BP, heart rate (HR), SDHR, LF, and the LF/HF ratio (p < 0.05) and an increase in the HF band in both groups during the follow-up period (p < 0.05). SOP women had reduced root mean square differences of successive RR intervals (RMSSD) and HF band and an increased LF band and SD2/SD1 ratio compared to the OB group during the one-year follow-up (p < 0.05). ASM/wt × 100, % was negatively associated with the LF band (r = -0.24, p = 0.00) and positively associated with the HF band (r = 0.22, p = 0.01). Conversely, HS had no association with LF (r = -0.14, p = 0.09) and HF (r = 0.11, p = 0.19). ASM/wt × 100, % and HS were negatively associated with the LF/HF ratio (p < 0.05).

CONCLUSIONS

Women who underwent BS had an improved HRV over a one-year follow-up. However, the improvement in HRV variables was less pronounced in women with low muscle mass and/or HS during the follow-up period.

The association between bedtime and cardiac autonomic control in community-dwelling older adults - The Yilan study, Taiwan

This study aimed to investigate the association between bedtime and cardiac autonomic function in older adults. This cross-sectional study included community-dwelling older adults aged ≥ 65 years. Self-reported bedtime was categorized as early (< 21:30), intermediate (21:30-22:30), and late (> 22:30). Cardiac autonomic function was evaluated by HRV. The lowest tertiles for each HRV parameter were defined as unhealthy indicators. A total of 3,729 individuals participated, with mean age of 76.3 ± 6.6 years. After controlling for various covariates, late bedtime was associated with a lower risk for unhealthy total power [Odds ratio (OR) = 0.74; 95% confidence interval (CI) = 0.59-0.93] and low frequency power (OR = 0.69, 95% CI = 0.55-0.87) than intermediate bedtime. In contrast, early bedtime was correlated with a higher risk of poor total power (OR = 1.23, 95% CI: 1.05-1.45) and high frequency power (OR = 1.18, 95% CI = 1.00-1.39). When further specifying sleep duration and physical disability into the regression models, the inverse association between late bedtime and unhealthy HRV remained; however, the association between early bedtime and HRV disappeared. Accordingly, we concluded that in terms of cardiac autonomic function, early bedtime in older adults is not necessarily beneficial for their health outcomes, whereas late bedtime may not be detrimental.Abbreviations: ADL: activity of daily living; BMI: body mass index; CI: confidence interval; GARS: the Groningen Activity Restriction Scale; HADS: The Hospital Anxiety and Depression Scale; HF: high frequency power; HRV: heart rate variability; LF: low frequency power; LF/HF: low frequency to high frequency ratio; OR: odds ratios; TP: total power.

Association of physical activity and heart rate variability in people with overweight and obesity: A systematic review

Background: Obesity is a major public health issue globally which is intrinsically linked to reduced heart rate variability (HRV). Physical inactivity and reduced resting HRV are linked to an increased risk of coronary heart disease, while athletes have a greater HRV. However, the exact correlation between physical activity and HRV remains uncertain. This systematic review aims to collect, report, and critically assess the current scientific literature about the association between physical activity and HRV in individuals with higher weight and obesity. Methods: A systematic search was carried out in electronic databases (Medline/PubMed, SCOPUS and CINAHL Plus) to retrieve studies that evaluated the relationship between physical activity and HRV in individuals with higher weight and obesity. Case-control, longitudinal/cohort, cross-sectional and observational studies were included. Using a critical narrative approach, information about the HRV, and physical activity was extracted and synthesized. The study was registered in PROSPERO: CRD42020208018 on October 9 2020. Results: After removing duplicates, 980 title/abstract records were checked for eligibility, and 12 papers were finally included in the narrative synthesis. The included studies contained physical activity as well as HRV in adults with higher weight or obesity with or without comorbidities. A negative relationship between moderate to vigorous physical activity and HRV indices had been found in two studies. There was also a negative relationship between sedentary time and HF (p = 0.049) and LF/HF (p = 0.036), as well as a positive relationship between sedentary time and LF (p = 0.014). Also dose-response association was found between vigorous exercise and higher SDNN, LF power, and HF power in one of the studies. Conclusions: This systematic review revealed a wide range of responses to physical activity and HRV; however, the current evidence uses a variety of approaches to objectively assess physical activity and measure HRV with different equipment.

Effect of Physical Exercise on Cardiac Autonomic Modulation in Hypertensive Individuals: A Systematic Review and Meta-analysis

BACKGROUND

Cardiac autonomic dysfunction is associated with hypertension and exercise training (ET) in healthy individuals is found to improve cardiac autonomic modulation (CAM). However, the effects of physical exercise on CAM in hypertensive individuals are under debate.

OBJECTIVE

The aim of the review is to systematically evaluate the literature on the effects of physical exercise on CAM in hypertensive individuals and analyse comparative differences in the effects of exercise between hypertensive and normotensive individuals.

METHODS

Electronic databases, such as Pubmed, PEDro, Scopus, and Web of Science, were systematically searched from inception up to February, 2022, evaluating the effect of ET on CAM either by heart rate variability (HRV), baroreflex sensitivity or heart rate recovery. Fifteen studies were included in the review. The risk of bias was assessed using the Cochrane risk of bias tool version 2 and the risk of bias in studies of intervention (ROBINS-I) tool. The overall quality of evidence was assessed using the grading of recommendations, assessment, development, and evaluation approach. Ten studies were included in the quantitative analysis. The meta-analysis and sensitivity analysis were performed using review manager 5.4.1; publication bias was assessed using Jamovi 2.2.5 software.

RESULTS

The qualitative analysis revealed low to moderate certainty of evidence for ET and moderate for aerobic training. For the effect of overall ET, the analysis revealed that the standardized mean differences (SMD) showed a significant effect of ET on HF (SMD 1.76, p = 0.04) and RMSSD (SMD 1.19, p < 0.0001) and a significant decrease in LF (SMD -1.78, p = 0.04). Aerobic training revealed nonsignificant improvement in HRV parameters. In the comparative analysis, ET did not show a significant difference in improvement between hypertensive and normotensive individuals.

CONCLUSION

This review suggests an improvement in CAM with physical exercise in hypertensive individuals, but the overall effect of ET in hypertensive individuals must be interpreted with caution as the robustness of the data is compromised in the sensitivity analysis of the trials. High-quality future trials focusing on different modes of ET interventions are needed to strengthen the findings of the present review.

Cardiac and Sudomotor Autonomic Function in Subjects with Psoriasis With and Without Metabolic Syndrome

Purpose: Studies have shown that subjects with psoriasis (PsO) are associated with an increased risk of developing metabolic syndrome (MetS), diabetes, and cardiovascular disease. In addition, MetS and diabetes are associated with autonomic dysfunction (AD). The aim of this study was to investigate cardiac and sudomotor autonomic function in subjects with PsO and without diabetes. Methods: A cross-sectional study was performed in 20 subjects with PsO, compared with age- and sex-matched 21 healthy controls, and 20 subjects with MetS. Subjects underwent skin evaluation by dermatologist, glycated hemoglobin (HbA1c), insulin, glucose, and lipid levels, sudomotor function testing with Sudoscan^™ device (Impeto Medical, Paris, France), and cardiac autonomic function testing with ANSAR device (ANX 3.0; ANSAR Group, Inc., Philadelphia, PA). Quality of Life (QOL) and peripheral neurologic function were also assessed. Results: Participants with PsO were significantly more obese, had higher levels of fasting insulin and triglycerides, and were more insulin resistant when compared to controls. Subjects with PsO showed significantly worse cardiac autonomic function when compared to control and MetS groups. Sudomotor function and QOL scores were similar between the groups. Subgroup analysis of PsO subjects without MetS criteria (n = 15) showed persistent significantly deteriorated cardiac autonomic function when compared to the other two groups. Conclusion: This study suggests an association between PsO and cardiac AD, independent of the presence of overt dysglycemia and MetS. Additional larger studies are needed to clarify the significance of these findings and the relationship between PsO, AD, and metabolic disease.

Comparison of Cardiac Autonomic Function in Type 2 Spinocerebellar Ataxia With Normal Control Using Heart Rate Variability as a Tool: A Cross-Sectional Study in Eastern India

BACKGROUND

Spinocerebellar ataxia (SCA) is a disease that refers to a category of inherited ataxias that are characterized by degenerative alterations in the cerebellum, pons, and spinocerebellar tracts. There are several different varieties of SCA and they are classified based on the mutant (altered) gene that causes the disease.

OBJECTIVE

To analyze the cardiovascular autonomic regulation in patients with type-2 spinocerebellar ataxia (SCA-2) from the heart rate variability (HRV) of 20 minutes resting electrocardiogram (ECG) and compare with the age and gender-matched controls.

MATERIALS AND METHODS

HRV of 27 type-2 spinocerebellar ataxia patients was calculated offline from the resting ECG recording and compared with 23 age and gender-matched controls. The HRV was analyzed by HRV software module MLS 310. The frequency and time domain parameters were computed and compared.

RESULT

 Type-2 spinocerebellar ataxia patients have significantly low HRV and parasympathetic activity at rest compared to normal control. The total power in SCA-2 is 13491.63 ± 7660.77 ms2 and the normal control is 21784.76 ± 11008.67 ms2. High-frequency power (HF) which is a marker of parasympathetic activity in SCA-2 is 3823.1 ± 364 ms2 and in normal control is 9006.1 ± 920.64 ms2. The standard deviation of all NN intervals (SDNN), the square root of the mean-squared differences of successive intervals (RMSSD), spectral interval, and delta NN is significantly low in SCA-2.

CONCLUSION

There is decreased parasympathetic tone and low HRV in SCA-2 as compared to normal controls.

Asymmetry and Heterogeneity: Part and Parcel in Cardiac Autonomic Innervation and Function

The cardiac autonomic nervous system (cANS) regulates cardiac adaptation to different demands. The heart is an asymmetrical organ, and in the selection of adequate treatment of cardiac diseases it may be relevant to take into account that the cANS also has sidedness as well as regional differences in anatomical, functional, and molecular characteristics. The left and right ventricles respond differently to adrenergic stimulation. Isoforms of nitric oxide synthase, which plays an important role in parasympathetic function, are also distributed asymmetrically across the heart. Treatment of cardiac disease heavily relies on affecting left-sided heart targets which are thought to apply to the right ventricle as well. Functional studies of the right ventricle have often been neglected. In addition, many principles have only been investigated in animals and not in humans. Anatomical and functional heterogeneity of the cANS in human tissue or subjects is highly valuable for understanding left- and right-sided cardiac pathology and for identifying novel treatment targets and modalities. Within this perspective, we aim to provide an overview and synthesis of anatomical and functional heterogeneity of the cANS in tissue or subjects, focusing on the human heart.

Unclear outcomes of heart rate variability following a concussion: a systematic review

PURPOSE

: To systematically regroup articles that were published since the latest systematic search, but with specific inclusion criteria to help comparison that will offer a focused presentation of methods and results. This will offer a full overview of HRV's behavior at rest and during exercise in adults post-concussion.

METHODS

: The systematic review was conducted using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) method. A computer-based systematic search was conducted in December 2019 through the Pubmed, Scopus and SPORTDiscus databases. A manual search was performed through the reference list of all articles retained. The reliability of the systematic search was assured by having the article selection process entirely repeated by a second author.

RESULTS

: The systematic search yielded a total of 15 articles to be further analyzed. Results show impairment of HRV during exercise for individuals with concussion, heterogenous studies with lack of control over confounding factors and only less than half of the results showing a significant difference between individuals with concussion and controls.

CONCLUSION

: Further research should try standardizing HRV measurement protocols that control confounding factors to allow easier comparison between studies and allows the possibility for an eventual meta-analysis.

The effects of clinical and angiographic aspects of coronary artery disease on the cardiac autonomic function: a single-center prospective cohort study

BACKGROUND

Autonomic malfunction is linked to elevated cardiovascular morbidity and mortality. Various patient characteristics can alter the cardiac autonomic function therefore, using a prospective observational study, we aimed to assess the effects of different clinical and angiographic factors of coronary artery disease (CAD) patients on the cardiac autonomic function evaluated by heart rate variability (HRV) measurement.

METHODS AND PATIENTS

100 patients undergoing coronary angiography when clinically indicated were enrolled. A short-term 5-minute HRV measurement was performed by CheckMyheart™ handheld HRV device manufactured by DailyCare BioMedical Inc, Taiwan. HRV data were fed to CheckMyheart™ 5-min HRV analysis software and interpreted based on the standard methods for HRV measurement as discussed in the Task Force of the European Society of Cardiology (ESC) and The North American Society of Pacing and Electrophysiology (NAPSE). Coronary angiography was done with an emphasis on SYNTAX (SX) score calculation.

RESULTS

The mean age of the recruited patients was 56.89±10.75 years with 85% of them were males and the mean SX score 13.11±8.52. Multivariate regression analysis of the different patient clinical and angiographic characteristics affecting HRV showed that CAD type either single or multi-vessel and SX score were the major independent variables affecting HRV in patients with CAD.

CONCLUSION

The complexity of CAD measured by SX score was the main independent predictor affecting the cardiac autonomic function estimated by HRV measurement.

Holter-Derived Autonomic Function, Arrhythmias and Carbohydrate Metabolism in Patients with Class III Obesity Treated with Laparoscopic Sleeve Gastrectomy

The effects of weight loss following bariatric surgery on autonomic balance, arrhythmias and insulin resistance are still of interest. We prospectively investigated 50 patients with BMI > 40 kg/m², aged 36.5 (18–56) years who underwent laparoscopic sleeve gastrectomy. Among other examinations, all subjects had 24-h Holter monitoring with heart rate variability (HRV) and heart rate turbulence (HRT) evaluation. After a median of 15 months, BMI decreased from 43.9 to 29.7 kg/m², the incidence of hypertension decreased from 54 to 32% (p = 0.04) and any carbohydrate disorders decreased from 24 to 6% (p = 0.02). Fasting insulin concentration and insulin resistance index improved significantly (p < 0.001). Improvements in HRV parameters related to the sympathetic autonomic division were also observed (p < 0.001), while HRT evaluation was not conclusive. The enhancement of autonomic tone indices was correlated with reduction of BMI (SDNN-I r = 0.281 p = 0.04; SDNN r = 0.267 p = 0.05), but not with reduction of waist circumference, and it was also associated with decrease of mean heart rate (OR 0.02, 95%CI 0.0–0.1, p < 0.001). The incidence of arrhythmias was low and similar before and after follow-up. In conclusion, improvement of homeostasis of carbohydrate metabolism and autonomic function is observed in relatively young patients after weight loss due to laparoscopic sleeve gastrectomy.

Sympathetic Effect of Auricular Transcutaneous Vagus Nerve Stimulation on Healthy Subjects: A Crossover Controlled Clinical Trial Comparing Vagally Mediated and Active Control Stimulation Using Microneurography

Introduction: Auricular low-level transcutaneous vagus nerve stimulation (aLL-tVNS) has emerged as a promising technology for cardiac arrhythmia management but is still experimental. In this physiological study, we hypothesized that aLL-tVNS modulated the autonomic nervous balance through a reduction of sympathetic tone and an increase in heart rate variability (HRV). We investigated the muscle sympathetic nerve activity (MSNA) recorded by microneurography during vagally mediated aLL-tVNS and active control on healthy volunteers. Methods: In this crossover, double-blind controlled study, healthy men (N = 28; 27 ± 4 years old) were assigned to aLL-tVNS applied to cymba and lobe (active control) of the right ear. Each participant was randomly allocated to the three sequences (5 Hz, 20 Hz, and active control-5 Hz) during one session. MSNA signal was recorded at rest, during voluntarily apnea and aLL-tVNS. Sympathetic activity was expressed as: 1) number of bursts per minute (burst frequency, BF) and 2) MSNA activity calculated as BF x mean burst amplitude and expressed as changes from baseline (%). RR intervals, HRV parameters and sympathetic activity were analyzed during 5 min-baseline, 10 min-stimulation, and 10 min-recovery periods. Mixed regression models were performed to evaluate cymba-(5—20 Hz) effects on the parameters with stimulation. Results: During apnea and compared to baseline, BF and MSNA activity increased (p = 0.002, p = 0.001, respectively). No stimulation effect on RR intervals and HRV parameters were showed excepted a slightly increase of the LF/HF ratio with stimulation in the cymba-5Hz sequence (coef. ± SE: 0.76 ± 0.32%; p = 0.02). During stimulation, reductions from baseline in BF (Coef. ± SE: −4.8 ± 1.1, p < 0.001) was observed but was not statistically different from that one in the active control. Reduction of MSNA activity was not significantly different between sequences. Conclusion: Acute right cymba aLL-tVNS did not induce any overall effects neither on heart rate, HRV nor MSNA variables on healthy subjects when compared to active control. Interestingly, these findings questioned the role of active controls in medical device clinical trials that implied subjective endpoints.

Immediate effect of Kapalbhathi pranayama on short term heart rate variability (HRV) in healthy volunteers

OBJECTIVES

Kapalbhathi Pranayam (Kapal = forehead; bhati = shining) is a breathing exercise that has been practiced to cleanse the frontal brain in traditional practices like yoga. Still, there exists a dearth of literature on the effect of Kapalbhathi pranayama on physiological systems. So this present study was carried out to find the immediate effect of "kapalbhathi Pranayam" practice for the period of 5 min on cardiac autonomic function among the healthy volunteers.

MATERIALS AND METHODS

Apparently 50 healthy volunteers includes both sex were participated. They were randomly divided into Pranayama (n-25) and control (n-25) group. Pranayama group was practiced kapalbhathi pranayama 5 min (5 cycles) and control group was allowed to do normal breathing (12-16 breath/min). Lead II ECG was recorded for 5 min using simple AD converter before, immediately after practice and 20 min of recovery period.

RESULTS

One way Analysis of variance (ANOVA) followed by post hoc test was done using R statistical software. There was a significant (p < 0.05) parasympathetic withdrawal (Root Mean Square of the Successive Differences (RMSSD) - p < 0.04 and HF n.u - p < 0.05) was found in the pranayama group immediately after practice and its was changed to parasympathetic domination (RMSSD - p < 0.04 and HF n.u - p < 0.05) after 20 min of recovery period.

CONCLUSION

The present study suggested that though there was parasympathetic withdrawal immediately after practicing kapalbhathi pranayama, 20 min after the recovery period showed a parasympathetic domination in the pranayama group subjects. However, further studies are required to warrant the findings of this study.

Exercise based assessment of cardiac autonomic function in type 1 versus type 2 diabetes mellitus

Background

Cardiac autonomic neuropathy (CAN) is a complication of diabetes mellitus (DM) that is associated with increased mortality. Exercise-based assessment of autonomic function has identified diminished parasympathetic reactivation after exercise in type 2 DM. It is postulated herein, that this would be more prominent among those with type 1 DM.

Methods

Sixteen subjects with type 1 DM (age 32.9 ± 10.1 years), 18 subjects with type 2 DM (55.4 ± 8.0 years) and 30 controls (44.0 ± 11.6 years) underwent exercise-based assessment of autonomic function. Two 16-min submaximal bicycle tests were performed followed by 45 min of recovery. On the second test, atropine (0.04 mg/kg) was administered near end-exercise so that all of the recovery occurred under parasympathetic blockade. Plasma epinephrine and norepinephrine levels were measured at rest, during exercise, and during recovery.

Results

There were no differences in resting or end-exercise heart rates in the three groups. Parasympathetic effect on RR-intervals during recovery (p < 0.03) and heart rate recovery (p = 0.02) were blunted in type 2 DM. Type 1 DM had higher baseline epinephrine and norepinephrine levels (p < 0.03), and exhibited persistent sympathoexcitation during recovery.

Conclusions

Despite a longer duration of DM in the study patients with type 1 versus type 2 DM, diminished parasympathetic reactivation was not noted in type 1 DM. Instead, elevation in resting plasma catecholamines was noted compared to type 2 DM and controls. The variable pathophysiology for exercise-induced autonomic abnormalities in type 1 versus type 2 DM may impact prognosis.

Relation of vascular dilator function and cardiac autonomic function with coronary angiography findings in patients with non-ST segment elevation acute coronary syndrome

BACKGROUND

A sizeable number of patients with a diagnosis of non-ST segment elevation acute coronary syndrome show non-obstructive coronary artery disease. In this study we assessed whether differences in vascular and cardiac autonomic function exist between non-ST segment elevation acute coronary syndrome patients with obstructive or non-obstructive coronary artery disease.

METHODS AND RESULTS

Systemic endothelium-dependent and independent vascular dilator function (assessed by flow-mediated dilation and nitrate-mediated dilation of the brachial artery, respectively) and cardiac autonomic function (assessed by time-domain and frequency-domain heart rate variability parameters) were assessed on admission in 120 patients with a diagnosis of non-ST segment elevation acute coronary syndrome. Patients were divided into two groups according to coronary angiography findings: (a) 59 (49.2%) with obstructive coronary artery disease (≥50% stenosis in any epicardial arteries); (b) 61 (50.8%) with non-obstructive coronary artery disease. No significant differences between the two groups were found in both flow-mediated dilation (5.03 ± 2.6 vs. 5.40 ± 2.5%, respectively; P = 0.37) and nitrate-mediated dilatation (6.79 ± 2.8 vs. 7.30 ± 3.4%, respectively; P = 0.37). No significant differences were also observed between the two groups both in time-domain and frequency-domain heart rate variability variables, although the triangular index tended to be lower in obstructive coronary artery disease patients (30.2 ± 9.5 vs. 33.9 ± 11.6, respectively; P = 0.058). Neither vascular nor heart rate variability variables predicted the recurrence of angina, requiring emergency room admission or re-hospitalisation, during 11.3 months of follow-up.

CONCLUSIONS

Among patients admitted with a diagnosis of non-ST segment elevation acute coronary syndrome we found no significant differences in systemic vascular dilator function and cardiac autonomic function between those with obstructive coronary artery disease and those with non-obstructive coronary artery disease.

Heart Rate Variability and Stress Recovery Responses during a Training Camp in Elite Young Canoe Sprint Athletes

Training camps are typical in elite Canoeing preparation, during which, the care to assure adaptation to avoid undesired fatigue is not always present. This study aimed identifying a specific sex response in perceived training loads, recovery and stress balance, and cardiac autonomic responses. Twenty-one elite athletes (11 males and 10 females) of the Portuguese Canoeing National team participated in the investigation. The daily HRV (lnRMSSD) was monitored. The (RESTQ-52) questionnaire was used to access the recovery and stress state. The 10-day training camp was composed of two consecutive 5-day periods (P1 and P2). Data analyses were performed using confidence limits, effect size, and magnitude-based inference. In the females, Session rating of perceived exertion (sRPE), lnRMSSD, and its coefficient of variation did not change between P1 and P2. However, in males, lnRMSSD showed a small reduction from P1 to P2. Also, sRPE was higher in males over the training period, with a possibly small difference at P2. Regarding RESTQ-52, total stress most likely increased with large and very large differences in males and moderate differences in females during the training period. Male canoeists undertook higher perceived training loads than females, with a consequent higher level of total perceived stress and lnRMSSD during a 10-day training camp.

Effects Of Exercise Training With Dietary Restriction On Arterial Stiffness, Central Hemodynamic Parameters And Cardiac Autonomic Function In Obese Adolescents

PURPOSE

This study aimed to assess the effects of exercise with dietary restriction on arterial stiffness, central hemodynamics, and cardiac autonomic function in obese adolescents.

PATIENTS AND METHODS

Twenty-one obese adolescents completed a 6-week exercise and dietary program. Body composition and metabolic parameters were measured. Carotid-femoral pulse wave velocity (cfPWV) and brachial-ankle pulse wave velocity (baPWV) were used to assess central and systemic arterial stiffness, respectively. Using applanation tonometry, the analyses of central hemodynamic parameters [central blood pressure, heart rate (HR), augmentation index normalized at 75 bpm (AIx75), and subendocardial viability ratio (SEVR)] were performed. To determine cardiac autonomic function, heart rate variability (HRV) was analyzed by standard deviation of normal R-R intervals (SDNN), root mean square of successive R-R interval differences (RMSSD), percentage of successive R-R intervals that differed by >50 ms (pNN50), total power (TP), low-frequency (LF) and high-frequency (HF) power, and LF/HF ratio.

RESULTS

Following the intervention, obese adolescents had reductions in body mass index, body fat percentage, brachial systolic and diastolic blood pressure, and HR; and they had shown improvements in lipid profiles. There were reductions in both cfPWV and baPWV following the intervention. Moreover, there were reductions in AIx75, aortic systolic and diastolic blood pressure and an augmentation in SEVR after intervention. The intervention increased cardiac autonomic function (determined by increased SDNN, RMSSD, pNN50, HF, and reduced LF/HF). Furthermore, we observed a correlation between increased cardiac autonomic function (SDNN, RMSSD, pNN50 and HF) and increased central hemodynamics, as measured by SEVR and AIx75.

CONCLUSION

Obese adolescents had increased central hemodynamics and autonomic function with reduced arterial stiffness after exercise and dietary restriction. Moreover, a positive correlation between an enhancement of cardiac autonomic function and an augmentation in central hemodynamics was found after the intervention.

The Impact of a Ballet and Modern Dance Performance on Heart Rate Variability in Collegiate Dancers

Heart rate (HR) variability (HRV) is a useful tool for assessing cardiac autonomic function and identifying potential readiness to perform in athletic populations, but has yet to be investigated in dance populations. As such, HRV may be able to provide valuable insight into the preparedness of dancers and the demands of performance in a collegiate dance population. 29 female dancers were monitored leading up to and following a dance performance. Analysis of HRV focused on the square root of the mean squared differences of the successive RR intervals (RMSSD). A one-way ANOVA, with Bonferroni post-hoc, paired with magnitude-based-inferences (MBI) with effect sizes (ES) were used to analyze changes during the Winter Dance Concert, while the Recovery-Stress Questionnaire for Athletes (REST-Q Sport) measured the frequency of stress of dancers. When compared to baseline (69.8 ± 1.7 bpm), mean (HR) was increased at both pre-show recordings (76.5 ± 2.1 bpm and 75.6 ± 1.8 bpm). In contrast, RMSSD was significantly diminished (p < 0.05) at both pre-show recordings (40.6 ± 28.4 ms and 40.5 ± 21.8 ms) as compared to baseline (70.3 ± 38.4 ms). Dancers reported increased (p < 0.05) self-efficacy before the second show and at 36 h post-concert. As expected, Dance Exposure (DE) increased significantly (p < 0.05), while Academic Exposure (AE) was similar, during the week leading up to the dance concert. The results suggest dancers responded to concert dance performances similarly to other athletic populations approaching intense competition by exhibiting decreased parasympathetic activity prior to the dance performances, which returned to baseline values 36 h after their performances. Given the increase in self-efficacy, these fluctuations may indicate a readiness to a performance comparable to athletes.

Autonomic Nervous System Activity for Risk Stratification of Emergency Patients With Pneumonia

BACKGROUND

Community-acquired pneumonia (CAP) causes appreciable morbidity and mortality in adults, especially in those ≥65 years of age. At hospital admission, an immediate and reliable risk assessment is necessary to detect patients with possible fatal outcome.

OBJECTIVE

We aimed to evaluate markers of the autonomic nervous system based on an electrocardiogram to predict mortality in patients with CAP.

METHODS

For this purpose, the deceleration capacity (DC) of heart rate was calculated in 253 patients who presented to the emergency department with CAP. The 30-day mortality rate was defined as the primary endpoint (PEP). The secondary endpoint was the total mortality within 180 days.

RESULTS

PEP was reached in 33 patients (13%). The DC, measured in milliseconds, was significantly lower in patients who reached the PEP than in those who did not (2.3 ± 1.5 ms vs. 3.6 ± 2.3 ms, p = 0.004). The DC was also significantly lower in nonsurvivors than in survivors at the time of the secondary endpoint (2.3 ± 1.5 ms vs. 3.7 ± 2.4 ms, p < 0.001). Our results indicate that DC is an independent predictor of 30- and 180-day mortality.

CONCLUSION

DC was independently associated with death from CAP in our study. As a practical consequence, DC could be useful in triage decisions. Patients with certain high risks could benefit from adjuvant treatment and special medical attention.

Association of size-fractionated indoor particulate matter and black carbon with heart rate variability in healthy elderly women in Beijing

Associations between size-fractionated indoor particulate matter (PM) and black carbon (BC) and heart rate variability (HRV) and heart rate (HR) in elderly women remain unclear. Twenty-nine healthy elderly women were measured for 24-hour HRV/HR indices. Real-time size-fractionated indoor PM and BC were monitored on the same day and on the preceding day. Mixed-effects models were applied to investigate the associations between pollutants and HRV/HR indices. Increases in size-fractionated indoor PM were significantly associated with declines in power in the high-frequency band (HF), power in the low-frequency band (LF), and standard deviation of all NN intervals (SDNN). The largest decline in HF was 19% at 5-minute moving average for an interquartile range (IQR) increase (24 μg/m³ ) in PM_0.5 . The results showed that smaller particles could lead to greater reductions in HRV indices. The reported associations were modified by body mass index (BMI): Declines in HF at 5-minute average for an IQR increase in PM_0.5 were 34.5% and 1.0% for overweight (BMI ≥25 kg/m² ) and normal-weight (BMI <25 kg/m² ) participants, respectively. Moreover, negative associations between BC and HRV indices were found to be significant in overweight participants. Increases in size-fractionated indoor PM and BC were associated with compromised cardiac autonomic function in healthy elderly women, especially overweight ones.

Age-related decline in cardiac autonomic function is not attenuated with increased physical activity

Age and physical inactivity are important risk factors for cardiovascular mortality. Heart rate response to exercise (HRRE) and heart rate recovery (HRR), measures of cardiac autonomic function, are strong predictors of mortality. The present study defined the effect of age and physical activity on HRRE and HRR. Healthy women (N=72) grouped according to age (young, 20-30 years; middle, 40-50 years; and older, 65-81 years) and daily physical activity (low active <7500, high active >12,500 steps/day) performed a maximal cardiopulmonary exercise test. The HRRE was defined as an increase in heart rate from rest to 1, 3 and 5 minutes of exercise and at 1/3 of total exercise time, and HRR as the difference in heart rate between peak exercise and 1, 2, and 3 minutes later. Age was associated with a significant decline in HRRE at 1 min and 1/3 of exercise time (r= − 0.27, p=0.04, and r=−0.39, p=0.02) and HRR at 2 min and 3 min (r=−0.35, p=0.01, and r=−0.31, p=0.02). There was no significant difference in HRRE and HRR between high and low-active middle-age and older women (p>0.05). Increased level of habitual physical activity level appears to have a limited effect on age-related decline in cardiac autonomic function in women.

Modulation of Cardiac Autonomic Function by Fingolimod Initiation and Predictors for Fingolimod Induced Bradycardia in Patients with Multiple Sclerosis

Objective: It is well-known that initiation of fingolimod induces a transient decrease of heart rate. However, the underlying cardiac autonomic regulation is poorly understood. We aimed to investigate the changes of autonomic activity caused by the first dose of fingolimod using a long-term multiple trigonometric spectral analysis for the first time. In addition, we sought to use the continuous Holter ECG recording to find predictors for fingolimod induced bradycardia.

Methods: Seventy-eight patients with relapsing-remitting multiple sclerosis (RRMS) were included. As a part of the START study (NCT01585298), continuous electrocardiogram was recorded before fingolimod initiation, and until no <6 h post medication. Time domain and frequency domain heart rate variability (HRV) parameters were computed hourly to assess cardiac autonomic regulation. A long-term multiple trigonometric regressive spectral (MTRS) analysis was applied on successive 1-h-length electrocardiogram recordings. Decision tree analysis was used to find predictors for bradycardia following fingolimod initiation.

Results: Most of the HRV parameters representing parasympathetic activities began to increase since the second hour after fingolimod administration. These changes of autonomic regulations were in accordance with the decline of heart rate. Baseline heart rate was highly correlated with nadir heart rate, and was the only significant predicting factor for fingolimod induced bradycardia among various demographic, clinical and cardiovascular variables in the decision tree analysis.

Conclusions: The first dose application of fingolimod enhances the cardiac parasympathetic activity during the first 6 h post medication, which might be the underlying autonomic mechanism of reduced heart rate. Baseline heart rate is a powerful predictor for bradycardia caused by fingolimod.

The effects of baroreflex activation therapy on blood pressure and sympathetic function in patients with refractory hypertension: the rationale and design of the Nordic BAT study

OBJECTIVE

To explore the effects of baroreflex activation therapy (BAT) on hypertension in patients with treatment resistant or refractory hypertension.

METHODS

This investigator-initiated randomized, double-blind, 1:1 parallel-design clinical trial will include 100 patients with refractory hypertension from 6 tertiary referral hypertension centers in the Nordic countries. A Barostim Neo System will be implanted and after 1 month patients will be randomized to either BAT for 16 months or continuous pharmacotherapy (BAT off) for 8 months followed by BAT for 8 months. A second randomization will take place after 16 months to BAT or BAT off for 3 months. Eligible patients have a daytime systolic ambulatory blood pressure (ABPM) of  ≥145 mm Hg, and/or a daytime diastolic ABPM of  ≥95 mm Hg after witnessed drug intake (including  ≥3 antihypertensive drugs, preferably including a diuretic).

RESULTS

The primary end point is the reduction in 24-hour systolic ABPM by BAT at 8 months, as compared to pharmacotherapy. Secondary and tertiary endpoints are effects of BAT on home and office blood pressures, measures of indices of cardiac and vascular structure and function during follow-up, and safety.

CONCLUSIONS

This academic initiative will increase the understanding of mechanisms and role of BAT in the refractory hypertension.

Music Improves Subjective Feelings Leading to Cardiac Autonomic Nervous Modulation: A Pilot Study

It is widely accepted that listening to music improves subjective feelings and reduces fatigue sensations, and different kinds of music lead to different activations of these feelings. Recently, cardiac autonomic nervous modulation has been proposed as a useful objective indicator of fatigue. However, scientific considerations of the relation between feelings of fatigue and cardiac autonomic nervous modulation while listening to music are still lacking. In this study, we examined which subjective feelings of fatigue are related to participants' cardiac autonomic nervous function while they listen to music. We used an album of comfortable and relaxing environmental music, with blended sounds from a piano and violin as well as natural sound sources. We performed a crossover trial of environmental music and silent sessions for 20 healthy subjects, 12 females, and 8 males, after their daily work shift. We measured changes in eight types of subjective feelings, including healing, fatigue, sleepiness, relaxation, and refreshment, using the KOKORO scale, a subjective mood measurement system for self-reported feelings. Further, we obtained measures of cardiac autonomic nervous function on the basis of heart rate variability before and after the sessions. During the music session, subjective feelings significantly shifted toward healing and a secure/relaxed feeling and these changes were greater than those in the silent session. Heart rates (ΔHR) in the music session significantly decreased compared with those in the silent session. Other cardiac autonomic parameters such as high-frequency (HF) component and the ratio of low-frequency (LF) and HF components (LF/HF) were similar in the two sessions. In the linear regression analysis of the feelings with ΔHR and changes in LF/HF (ΔLF/HF), increases and decreases in ΔHR were correlated to the feeling axes of Fatigue-Healing and Anxiety/Tension–Security/Relaxation, whereas those in ΔLF/HF were related to the feeling axes of Sleepiness–Wakefulness and Gloomy–Refreshed. This indicated that listening to music improved the participants' feelings of fatigue and decreased their heart rates. However, it did not reduce the cardiac LF/HF, suggesting that cardiac LF/HF might show a delayed response to fatigue. Thus, we demonstrated changes in cardiac autonomic nervous functions based on feelings of fatigue.

Distinguishing bipolar II depression from unipolar major depressive disorder: Differences in heart rate variability

OBJECTIVES

Bipolar II (BPII) depression is commonly misdiagnosed as unipolar depression (UD); however, an objective and reliable tool to differentiate between these disorders is lacking. Whether cardiac autonomic function can be used as a biomarker to distinguish BPII from UD is unknown.

METHODS

We recruited 116 and 591 physically healthy patients with BPII depression and UD, respectively, and 421 healthy volunteers aged 20-65 years. Interviewer and self-reported measures of depression/anxiety severity were obtained. Cardiac autonomic function was evaluated by heart rate variability (HRV) and frequency-domain indices of HRV.

RESULTS

Patients with BPII depression exhibited significantly lower mean R-R intervals, variance (total HRV), low frequency (LF)-HRV, and high frequency (HF)-HRV but higher LF/HF ratio compared to those with UD. The significant differences remained after adjusting for age. Compared to the controls, the patients with BPII depression showed cardiac sympathetic excitation with reciprocal vagal impairment, whereas the UD patients showed only vagal impairment. Depression severity independently contributed to decreased HRV and vagal tone in both the patients with BPII depression and UD, but increased sympathetic tone only in those with BPII depression.

CONCLUSIONS

HRV may aid in the differential diagnosis of BPII depression and UD as an adjunct to diagnostic interviews.

Relationship between inflammatory and coagulation biomarkers and cardiac autonomic function in HIV-infected individuals

AIM

To examine the relationship between inflammatory and coagulation biomarkers and cardiac autonomic function (CAF) as measured by heart rate variability in persons with HIV.

MATERIALS & METHODS

This analysis included 4073 HIV-infected persons from the Strategies for Management of Antiretroviral Therapy study. We examined the association between IL-6, high-sensitivity C-reactive protein (hsCRP) and D-dimer with heart rate variability measures (SDNN and rMSSD), both cross-sectionally and longitudinally.

RESULTS

Cross-sectional analysis revealed significant inverse associations between IL-6, hsCRP and d-dimer with SDNN and rMSSD (p < 0.01 for all comparisons). However, longitudinal analysis failed to show a significant association between baseline IL-6, hsCRP and d-dimer with change in CAF over time.

CONCLUSION

Cross-sectionally, higher levels of inflammatory and coagulation biomarkers were associated with lower levels of CAF in the Strategies for Management of Antiretroviral Therapy trial. Although deterioration in CAF was observed during followup, baseline levels of inflammatory and coagulation markers were not predictive of the decline in CAF over time.

Lower heart rate variability predicts increased level of C-reactive protein 4 years later in healthy, nonsmoking adults

BACKGROUND

Inflammation and vagally mediated heart rate variability (vmHRV) have been implicated in a number of conditions including diabetes and cardiovascular disease. Consistent with the inflammatory reflex termed the 'cholinergic anti-inflammatory pathway', numerous cross-sectional studies have demonstrated negative associations between vmHRV and inflammatory markers such as C-reactive protein (CRP). The only prospective study, however, showed the opposite: higher CRP at baseline predicted higher high-frequency heart rate variability (HF-HRV) at follow-up. Thus, additional studies are needed to examine the prospective association between vmHRV and CRP.

METHODS

Healthy employees participated in a voluntary on-site health assessment. Blood samples and ambulatory heart rate recordings were obtained, and night-time HF-HRV was calculated. Useable heart rate data were available in 2007 for 106 nonsmoking employees (9% women; age 44.4 ± 8 years), all of whom returned for an identical follow-up health assessment in 2011. Bootstrapped (500 replications) bivariate (r) and partial Pearson's correlations (ppc) adjusting for sex, age and body mass index at baseline (2007) were calculated.

RESULTS

Zero-order correlations indicated that higher HF-HRV was associated with lower levels of CRP at both time-points (2007: r = -0.19, P < 0.05; 2011: r = -0.34, P < 0.001). After adjustment, HF-HRV remained a significant predictor of CRP (ppc = -0.20, P < 0.05).

CONCLUSION

In this study, we have provided in vivo support for the cholinergic anti-inflammatory pathway in humans. Cardiac vagal modulation at baseline predicts level of CRP 4 years later. Our findings have important implications for the role of vmHRV as a risk factor for cardiovascular disease morbidity and mortality. Interventions targeted at vmHRV might be useful in the prevention of diseases associated with elevated systemic inflammation.

Impaired cardiac autonomic functions in apparently healthy subjects with vitamin D deficiency

OBJECTIVES

Vitamin D (VitD) deficiency affects the cardiovascular system via endocrine, paracrine, and autocrine pathways. Limited data are available regarding cardiac autonomic dysfunction in VitD deficiency. The aim of this study was to assess the cardiac autonomic functions by using heart rate recovery index (HRRI) and heart rate variability (HRV) in apparently healthy subjects with VitD deficiency.

METHODS

A total of 24 VitD deficient and 50 age-, gender-, and body mass index-matched VitD sufficient healthy participants who admitted to outpatient clinics at a tertiary centre were enrolled. All study participants underwent Treadmill exercise test and 24-hour Holter recording to assess cardiac autonomic functions. HRRIs were calculated by subtracting first, second, and third minute heart rates during recovery period from maximal heart rate.

RESULTS

Mean HRR1 (28.0 ± 8.3 vs 42.8 ± 6.4, P < 0.001), HRR2 (41.1 ± 11.2 vs 60.8 ± 10.4, P < 0.001), and HRR3 (44.9 ± 13.3 vs 65.9 ± 9.8, P < 0.001) were significantly higher in VitD sufficient group compared to VitD deficient group. HRV parameters as, SDNN (P = 0.040), SDANN (P < 0.001), RMSSD (P < 0.001), PNN50 (P < 0.001), and HF (P < 0.001) were significantly decreased in patients with VitD deficiency; but LF (P < 0.001) and LF/HF (P = 0.003) were significantly higher in VitD deficient group. Serum 25(OH)D level was positively correlated with HRRIs (P < 0.001), PNN50, RMSSD, SDANN, and HFnu; negatively correlated with LFnu and LF/HF (P < 0.05). Also, multivariate linear regression analysis showed that serum 25(OH)D level was significantly associated with HRRIs and HRV parameters (P < 0.001).

CONCLUSION

Our study results suggest that cardiac autonomic functions are impaired in patients with VitD deficiency despite the absence of overt cardiac involvement and symptoms. Further studies are needed to elucidate the prognostic significance and clinical implications of impaired autonomic functions in patients with VitD deficiency.

Heart rate variability in unmedicated patients with bipolar disorder in the manic phase

AIMS

Decreased heart rate variability (HRV) has been proposed in bipolar disorder. To date, there has been no adequate study that has investigated resting HRV in unmedicated patients with bipolar disorder in the manic state.

METHODS

To examine whether bipolar mania is associated with decreased HRV, 61 unmedicated patients with bipolar mania and 183 healthy volunteers aged 20-65 years were recruited for this case-control analysis. The Young Mania Rating Scale (YMRS), Clinical Global Impression-Severity, Hamilton Depression Rating Scale (HAM-D), and Hamilton Anxiety Rating Scale (HAM-A) were used for the clinical ratings. Cardiac autonomic function was evaluated by measuring HRV parameters and the frequency-domain indices of HRV were obtained.

RESULTS

Patients with bipolar mania exhibited significantly lower mean RR interval, variance, low-frequency (LF)-HRV, and high-frequency (HF)-HRV but higher LF/HF compared to controls. Decreased HRV (variance) was associated with the YMRS total scores. Both the YMRS total scores and the Clinical Global Impression-Severity scores were positively correlated with the LH/HF ratio and inversely correlated with the HF-HRV. There was no significant correlation between the HAM-D/HAM-A scores and any HRV parameter.

CONCLUSIONS

Bipolar mania is associated with cardiac autonomic dysregulation, highlighting the importance of assessing HRV in manic patients. Further studies examining the influence of anti-manic psychotropic drugs on cardiac autonomic regulation in bipolar mania are needed.

Completion report: Effect of Comprehensive Yogic Breathing program on type 2 diabetes: A randomized control trial

BACKGROUND

Yoga has been shown to be beneficial in diabetes in many studies, though randomized control trials are few. The aim of this randomized control trial was to see the effect of Sudarshan Kriya and related practices (comprehensive yogic breathing program) on quality of life, glycemic control, and cardiac autonomic functions in diabetes. Diabetes mellitus is a risk factor for sudden cardiac death. Cardiac autonomic neuropathy has been implicated in the causation of sudden cardiac death. Therefore, a maneuver to prevent progression of cardiac autonomic neuropathy holds significance.

MATERIALS AND METHODS

A total of 120 patients of diabetes on oral medication and diet and exercise advice were randomized into two groups: (1) Continued to receive standard treatment for diabetes. (2) Patients administered comprehensive yogic breathing program and monitored to regularly practice yoga in addition to standard treatment of diabetes. At 6 months, quality of life and postprandial plasma glucose significantly improved in the group practicing yoga compared to baseline, but there was no significant improvement in the fasting plasma glucose and glycated hemoglobin.

RESULTS

On per protocol analysis, sympathetic cardiac autonomic functions significantly improved from baseline in the group practicing comprehensive yogic breathing.

CONCLUSION

This randomized control trial points towards the beneficial effect of yogic breathing program in preventing progression of cardiac neuropathy. This has important implications as cardiac autonomic neuropathy has been considered as one of the factors for sudden cardiac deaths.

Delayed heart rate recovery is strongly associated with early and late-stage prehypertension during exercise stress testing

BACKGROUND

Heart rate recovery (HRR) has been shown to predict cardiovascular disease mortality. HRR is delayed in hypertension, but its association with prehypertension (PHT) has not been well studied.

METHODS

The study population consisted of 683 asymptomatic individuals (90% men, aged 47±7.9 years). HRR was defined as peak heart rate minus heart rate after a 2-minute rest. PHT was categorized into stage I (systolic blood pressure (SBP) 120-129mm Hg or diastolic BP (DBP) 80-84mm Hg) or stage II (SBP 130-139mm Hg or DBP 85-89mm Hg). Logistic regression was used to generate odds ratios (ORs) for the relationship between HRR and PHT.

RESULTS

The mean HRR was lower in the PHT groups than in those who were normotensive (60 bpm and 58 bpm in stages I and II PHT vs. 65 bpm in normal BP; P <0.01). Persons with PHT were more likely to be in the lowest quartile of HRR compared with those with normal BP (adjusted OR, 3.80 and 95% confidence interval [CI], 1.06, 13.56 for stage II PHT and adjusted OR, 3.01 and 95% CI 1.05, 8.66 for stage I PHT). In a fully adjusted model, HRR was still significantly associated with both stages of PHT.

CONCLUSION

Among asymptomatic patients undergoing stress testing, delayed HRR was independently associated with early and late stages of PHT. Further studies are needed to determine the usefulness of measuring HRR in the prevention and management of hypertension.

Cardiac autonomic function and insulin resistance for the development of hypertension: a six-year epidemiological follow-up study

BACKGROUND AND AIMS

To explore the impact of cardiac autonomic function (CAF) and insulin resistance (IR) on incident hypertension.

METHODS AND RESULTS

In 1996, 1638 subjects finished baseline examination, which included anthropometry, blood pressures, CAF, blood biochemistry, plasma insulin, urine examination and electrocardiogram. CAF included standard deviation of normal-to-normal intervals or RR intervals (SDNN), low- and high-frequency power spectrum (LF and HF), and LF/HF ratio at supine for 5 min, the RR interval changes during lying-to-standing maneuver, and the ratio between the longest RR interval during expiration and the shortest RR interval during inspiration (E/I ratio). We used homeostasis model assessment to define beta cell function (HOMA-B) and insulin resistance (HOMA-IR). In total, 992 non-hypertensive participants completed the follow-up assessment in 2003 and 959 participants were included for the final analysis. Incident hypertension was determined by blood pressure status at follow-up. In unadjusted model, both square root of HOMA-IR (OR:3.37, 95%CI: 2.10-6.64) and HOMA-B (OR:0.996, 95%CI: 0.992-0.999) were related to incident hypertension. In multivariate model, square root of HOMA-IR (OR:1.97, 95%CI: 1.05-3.70), but not HOMA-B, was associated with incident hypertension. After further adjustment for baseline CAF, the positive relationship between the square root of HOMA-IR and incident hypertension disappeared. In contrast, LF/HF ratio (OR:1.18, 95%CI: 1.01-1.37), HF power (OR:0.98, 95%CI: 0.96-0.999), and E/I ratio (OR:0.71, 95%CI: 0.54-0.95) were each independently associated with incident hypertension after further adjustment for HOMA measures.

CONCLUSION

Sympathovagal imbalance with an apparently decreased parasympathetic tone is an important predictor of incident hypertension independent of IR.

Automated assessment of cardiac autonomic function by means of deceleration capacity from noisy, nonstationary ECG signals: validation study

BACKGROUND

Assessment of heart rate variability by means of deceleration capacity (DC) provides a noninvasive probe of cardiac autonomic activity. However, clinical use of DC is limited by the need of manual review of the ECG signals to eliminate artifacts, noise, and nonstationarities.

OBJECTIVE

To validate a novel approach to fully automatically assess DC from noisy, nonstationary signals

METHODS

We analyzed 100 randomly selected ECG tracings recorded for 10 minutes by routine monitor devices (GE DASH 4000, sample size 100 Hz) in a medical emergency department. We used a novel automated R-peak detection algorithm, which is mainly based on a Shannon energy envelope estimator and a Hilbert transformation. We transformed the automatically generated RR interval time series by phase-rectified signal averaging (PRSA) to assess DC of heart rate (DCauto ). DCauto was compared to DCmanual , which was obtained from the same manually preprocessed ECG signals.

RESULTS

DCauto and DCmanual showed good correlation and agreement, particularly if a low-pass filter was implemented into the PRSA algorithm. Correlation coefficient between DCauto and DCmanual was 0.983 (P < 0.0001). Average difference between DCauto and DCmanual was -0.23±0.49 ms with limits of agreement ranging from -1.19 to 0.73 ms. Significantly lower correlations were observed when a different R-peak detection algorithm or conventional heart rate variability (HRV) measures were tested.

CONCLUSIONS

DC can be fully automatically assessed from noisy, nonstationary ECG signals.

Decreased cardiac vagal control in drug-naive patients with panic disorder: a case-control study in Taiwan

INTRODUCTION

Cardiac autonomic dysregulation has been proposed in panic disorder (PD), but the results are mixed. Analyses with larger sample sizes and better methodology are needed.

METHODS

Forty-eight drug-naïve individuals with PD and 202 healthy volunteers were recruited for a case-control analysis. We used the Hamilton Anxiety Rating Scale and the Beck Anxiety Inventory to assess anxiety severity. Cardiac autonomic function was evaluated by measuring heart rate variability (HRV) parameters. Frequency-domain indices of HRV were obtained. The obtained results were evaluated in association with personality traits assessed by the Tridimensional Personality Questionnaire.

RESULTS

Patients exhibited reduced mean RR interval (816.94 ± 135.92 versus 873.47 ± 143.36 ms, P = 0.014) and HRV levels (Var 6.37 ± 1.32 versus 7.38 ± 0.95, LF 4.90 ± 1.63 versus5.82 ± 1.11 and HF 4.57 ± 1.53 versus 5.62 ± 1.24 [ln(ms2)], all P < 0.001) as compared to controls, which mainly suggested a reduction in cardiac vagal control in PD. The anxiety severity was negatively correlated with HRV levels (r = -0.29 for Var, r = -0.22 for LF and r = -0.28 for HF, all P < 0.001). The harm avoidance score (which has been suggested to be associated with serotonergic activity) was associated with decreased HRV levels (r = -0.22 for Var, P < 0.01, r = -0.14 for LF, P < 0.05 and r = -0.17 for HF, P < 0.01).

DISCUSSION

This study demonstrates that PD is associated with cardiac autonomic dysregulation, highlighting the importance of assessing HRV in PD patients.

Differential association of adiposity measures with heart rate variability measures in Koreans

PURPOSE

Although obesity has been associated with imbalances in cardiac autonomic nervous system, it is unclear whether there are differential relationships between adiposity measures and heart rate variability (HRV) measures. We aimed to examine differences in the relationship between adiposity measures and HRV indices in a healthy Korean population.

MATERIALS AND METHODS

In all, 1409 non-smokers (811 males, 598 females) without known histories of cardiovascular (CV), endocrine, or neurological diseases underwent adiposity measurements [(body mass index (BMI), percentage of body fat mass (PBF), and waist-to-hip ratio (WHR)], the HRV assessment (SDNN, RMSSD, LF, HF, LF/HF, and pNN50), and examination for CV risk factors (fasting glucose, LDL-cholesterol, HDL-cholesterol, triglycerides, hs-CRP, and blood pressure).

RESULTS

Compared with BMI and PBF, WHR was more strongly correlated with each HRV index and more likely to predict decreased HRV (<15 percentile vs. ≥ 15 percentile of each HRV index) in ROC curves analysis. In linear regression analysis, all adiposity measures were inversely associated with each HRV measure before adjusting for age, gender, and CV risk factors (p<0.05). After adjusting for the covariates, WHR was inversely related to RMSSD, LF, and pNN50; PBF with RMSSD, HF, and pNN50; BMI with RMSSD (p<0.05). The inversed association between HRV indices and the gender-specific WHR tertile was significant for subjects with BMI ≥ 25 kg/m(2), but not for those with BMI <25 kg/m(2).

CONCLUSION

WHR and PBF appear to be better indicators for low HRV than BMI, and the association between abdominal adiposity and HRV may be stronger in overweight subjects.

A randomized controlled trial of exercise training on cardiovascular and autonomic function among renal transplant recipients

BACKGROUND

There are conflicting data regarding the effects of renal transplantation (RT) on uraemic autonomic dysfunction. Moreover, no study has examined the impact of physical training on the cardiac autonomic function in RT patients. Thus, we studied the effects of exercise training on heart rate variability (HRV) and arterial baroreflex sensitivity (BRS), which are sensitive markers of cardiac autonomic outflow, in RT recipients.

METHODS

Eleven patients (Exercise group-aged 52.1 ± 5.6 years) were studied before and after 6 months of exercise training. Twelve age- and sex- matched RT patients (Sedentary) and 12 healthy sedentary individuals (Healthy), who remained untrained, served as controls. At baseline and follow-up, all the subjects underwent cardiopulmonary exercise testing for the evaluation of peak oxygen consumption (VO2peak), a tilt test for the evaluation of BRS and baroreflex effectiveness index (BEI) and an ambulatory 24-h Holter monitoring for time- and frequency-domain measures of HRV.

RESULTS

In the exercise group, VO2peak increased by 15.8% (P < 0.05) and all depressed HRV and BRS indices were significantly improved after training. Specifically, the standard deviation of all normal-to-normal (NN) intervals (SDNN) significantly increased by 92.5%, the root-mean-square of the differences between consecutive NN intervals by 45.4%, the percentage value of NN50 count by 58.2%, the high-frequency by 74.8% and low-frequency spectral power by 41.6%, BRS by 43.7% and BEI by 57.3%. None of the variables studied was altered over time in either control group.

CONCLUSIONS

The increased cardiorespiratory fitness by exercise training was associated with an improved BRS function and a modification of the sympathovagal control of HRV towards a persistent increase in parasympathetic tone. These alterations may lead to a better cardiovascular prognosis in RT recipients.

Cardiac autonomic functions in obese children

OBJECTIVE

The autonomic nervous system is assumed to have a role in the pathophysiology of obesity. In this study, we evaluated the autonomic system by measuring heart rate variability (HRV) in obese children.

METHODS

Thirty-two obese and 30 healthy children (mean ages: 11.6±2.0 years and 11.0±2.9 years, respectively) were enrolled in the study. Obesity was defined as a body mass index higher than 97th percentile for age- and gender-specific reference values. All participants were free of any disease and none of them was receiving any medication. Twenty-four-hour ambulatory electrocardiographic recordings were obtained and the time-domain and frequency-domain indices of HRV were analyzed. The study group was evaluated with respect to insulin resistance by HOMA-IR values.

RESULTS

A significant decrease in calculated HRV variables was observed in obese children as compared to controls. The HRV alteration was found in both time-domain and frequency-domain parameters. The subgroup analysis of the study group revealed a significant decrease in all investigated HRV parameters in the insulin-resistant obese children compared to the non-insulin-resistant obese ones.

CONCLUSIONS

Our results indicate that HRV is decreased in obese children, which implies parasympathetic withdrawal and sympathetic predominance. A marked decrease in HRV was observed in insulin-resistant obese children compared to their non-insulin-resistant counterparts. We propose that autonomic imbalance pertaining especially to insulin resistance may be involved in the pathogenesis of obesity in pediatric patients.

Association of heart rate variability in taxi drivers with marked changes in particulate air pollution in Beijing in 2008

BACKGROUND

Heart rate variability (HRV), a marker of cardiac autonomic function, has been -associated with particulate matter (PM) air pollution, especially in older patients and those with cardio-vascular diseases. However, the effect of PM exposure on cardiac autonomic function in young, healthy adults has received less attention.

OBJECTIVES

We evaluated the relationship between exposure to traffic-related PM with an aerodynamic diameter <or= 2.5 microm (PM2.5) and HRV in a highly exposed panel of taxi drivers.

METHODS

Continuous measurements of personal exposure to PM2.5 and ambulatory electrocardiogram monitoring were conducted on 11 young healthy taxi drivers for a 12-hr work shift during their work time (09002100 hr) before, during, and after the Beijing 2008 Olympic Games. Mixed-effects regression models were used to estimate associations between PM2.5 exposure and percent changes in 5-min HRV indices after combining data from the three time periods and controlling for potentially confounding variables.

RESULTS

Personal exposures of taxi drivers to PM2.5 changed markedly across the three time -periods. The standard deviation of normal-to-normal (SDNN) intervals decreased by 2.2% [95% confidence interval (CI), 3.8% to 0.6%] with an interquartile range (IQR; 69.5 microg/m3) increase in the 30-min PM2.5 moving average, whereas the low-frequency and high-frequency powers decreased by 4.2% (95% CI, 9.0% to 0.8%) and 6.2% (95% CI, 10.7% to 1.5%), respectively, in association with an IQR increase in the 2-hr PM2.5 moving average.

CONCLUSIONS

Marked changes in traffic-related PM2.5 exposure were associated with altered cardiac autonomic function in young healthy adults.

Cardiovascular autonomic function in conscious rats: a novel approach to facilitate stationary conditions

BACKGROUND

An experimental setting and software were developed to evaluate cardiovascular autonomic function in conscious rats. A restrained approach was used, which, upon proper habituation, induced little or no stress in the rats and limited motion artifacts.

METHODS

The ECG and arterial blood pressure were recorded. Time- and frequency-domain indices of heart rate variability (HRV) and blood pressure variability (BPV) were calculated. The spontaneous baroreflex sensitivity (spBRS) was estimated using the method of statistical dependence.

RESULTS

The power spectra clearly concentrated in a frequency band with center frequency around 0.4 Hz, the low frequency (LF) component, and one at the respiratory frequency at 1.5 Hz, the high frequency (HF) component. In baseline conditions, a direct association existed between mean R-R and especially HRV parameters denoting vagal modulation such as rMSSD, pNN5, and HF power. Beta-adrenergic blockade by propranolol diminished basal heart rate. Vagal indices increased while there was an exclusive decrease in the low frequency band of HRV. Alpha-adrenergic blockade with phentolamine produced a depressor response with tachycardia, and a clear decrease in the LF component of BPV. Both the LF and HF component in the HRV spectrum were virtually absent. Cholinergic blockade with atropine did not significantly alter BP but induced a clear tachycardia with decreased vagal indices. The HF component of HRV was completely abolished and the LF band was reduced.

CONCLUSIONS

Both alpha- and beta-adrenergic blockade left spBRS virtually unaltered, while cholinergic blockade profoundly diminished spBRS. Spectral fluctuations of beta-sympathetic tone were restricted to the LF range of HRV, while the HF respiratory component represented vagal modulation. The alpha-sympathetic system played a dominant role in the LF oscillations of BPV. A role of the vagus in the HF oscillations of BPV in the rat is questioned. The baroreflex depended mainly on changes in vagal activity.