Direct measurement of vagal tone in rats does not show correlation to HRV

AbstractThe vagus nerve is the largest autonomic nerve, innervating nearly every organ in the body. “Vagal tone” is a clinical measure believed to indicate overall levels of vagal activity, but is measured indirectly through the heart rate variability (HRV). Abnormal HRV has been associated with many severe conditions such as diabetes, heart failure, and hypertension. However, vagal tone has never been directly measured, leading to disagreements in its interpretation and influencing the effectiveness of vagal therapies. Using custom carbon nanotube yarn electrodes, we were able to chronically record neural activity from the left cervical vagus in both anesthetized and non-anesthetized rats. Here we show that tonic vagal activity does not correlate with common HRV metrics with or without anesthesia. Although we found that average vagal activity is increased during inspiration compared to expiration, this respiratory-linked signal was not correlated with HRV either. These results represent a clear advance in neural recording technology but also point to the need for a re-interpretation of the link between HRV and “vagal tone”.

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Resting vagal activity in schizophrenia: Meta-analysis of heart rate variability as a potential endophenotype

The British Journal of Psychiatry ◽

10.1192/bjp.bp.114.160762 ◽

2016 ◽

Vol 208 (1) ◽

pp. 9-16 ◽

Cited By ~ 59

Author(s):

Annika Clamor ◽

Tania M. Lincoln ◽

Julian F. Thayer ◽

Julian Koenig

Keyword(s):

Heart Rate ◽

Heart Rate Variability ◽

High Frequency ◽

Meta Analysis ◽

Random Effect ◽

Vagal Tone ◽

Sensitivity Analyses ◽

Psychotic Symptoms ◽

Vagal Activity ◽

Healthy Controls

BackgroundCardiac vagal tone, indexed by heart rate variability (HRV), is a proxy for the functional integrity of feedback mechanisms integrating central and peripheral physiology.AimsTo quantify differences in HRV in individuals with schizophrenia compared with healthy controls.MethodDatabases were systematically searched for studies eligible for inclusion. Random effect meta-analyses of standardised mean differences were calculated for vagal activity indicated by high-frequency HRV and the root mean square of successive R–R interval differences (RMSSD).ResultsThirty-four studies were included. Significant main effects were found for high-frequency HRV (P = 0.0008; Hedges' g =–0.98, 95% CI −1.56 to −0.41, k = 29) and RMSSD (P<0.0001; g =–0.91, 95% CI −1.19 to −0.62, k = 24), indicating lower vagal activity in individuals with schizophrenia than in healthy controls. Considerable heterogeneity was evident but effects were robust in subsequent sensitivity analyses.ConclusionsGiven the association between low HRV, threat processing, emotion regulation and executive functioning, reduced vagal tone may be an endophenotype for the development of psychotic symptoms.

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The Heart of an Endurance Athlete: Impact of and Recovery After an Ultra-Endurance Event.

10.21203/rs.3.rs-639854/v1 ◽

2021 ◽

Author(s):

Anton Swart ◽

Demitri Constantinou

Keyword(s):

Heart Rate ◽

Heart Rate Variability ◽

Nervous System ◽

Autonomic Nervous System ◽

The Body ◽

Mountain Biking ◽

Vagal Activity ◽

Autonomic Nervous System Dysfunction ◽

Autonomic Nervous ◽

Ultra Endurance

Abstract Background: Acute bouts of ultra-endurance exercise may cause an acute reduction in cardiac function, causing a physiological cascade which releases cardiac biomarkers. This study set out to determine the cardiac stress and recovery of participation in a three-day ultra-endurance mountain biking event of athletes using heart rate variability (HRV) as an outcome measure. Sixteen healthy participants (male and female) participating in a three-day ultra-endurance mountain biking event underwent a five-minute resting electrocardiography (ECG) recording in a supine position. Heart rate variability measurements were recorded two days before the race (baseline testing), after each race day, and at 24-hour post-event (recovery). Results: Time-domain and frequency domain measures showed significant (p≤0.05) changes from baseline in HRV parameters after each race day. The significant changes in HRV parameters reflected an increase in sympathetic activity after each day of the event. Our data revealed that the mean HR and RR variability variables did not return to baseline value after 24-hours of recovery, reflecting autonomic nervous system dysfunction, and that changes persisted for at least 24-hours post-event.Conclusion: Our study shows that competing in an ultra-endurance mountain bike event led to diminished vagal activity and a decrease in HRV throughout the event and persisted for at least 24-hours post-event. The body was under continuous sympathetic dominance during rest as well as during each day of racing, implying each race day can be considered a physiological stress. This may, in turn, cause a disturbance in homeostasis and an increase in autonomic nervous system dysfunction. This has implications for further research, including dysrhythmia risk, and monitoring of athletes in advising a return to strenuous activity.

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The heart of an endurance athlete: impact of and recovery after an ultra-endurance event.

10.1101/2020.07.16.20155127 ◽

2020 ◽

Author(s):

Anton Swart ◽

Demitri Constantinou

Keyword(s):

Heart Rate ◽

Heart Rate Variability ◽

Nervous System ◽

Autonomic Nervous System ◽

The Body ◽

Mountain Biking ◽

Vagal Activity ◽

Autonomic Nervous System Dysfunction ◽

Autonomic Nervous ◽

Ultra Endurance

Objectives Our study set out to determine the cardiac stress and recovery of participation in a three-day ultra-endurance mountain biking event of athletes using heart rate variability (HRV) as an outcome measure. Methods Sixteen healthy participants (male and female) participating in a three-day ultra-endurance mountain biking event underwent a five-minute resting ECG recording in a supine position. Heart rate variability measurements were recorded two days before the race (baseline testing), after each race day, and at 24-hour post-event (recovery). Results Time-domain and frequency domain measures showed significant (p≤0.05) changes from baseline in HRV parameters after each race day. Our study found significant changes in HRV parameters, all of which reflected an increase in sympathetic activity after each day of the event. These data also revealed that the mean HR and RR variability variables did not return to baseline value after 24-hours of recovery, reflecting autonomic nervous system dysfunction, and that changes persisted for at least 24-hours post-event. Conclusion Our study shows that competing in an ultra-endurance mountain bike event led to diminished vagal activity and a decrease in HRV throughout the event and persisted for at least 24 hours post-event. The body was under continuous sympathetic dominance during rest as well as during each day of racing, implying each race day can be considered a physiological stress. This may, in turn, cause a disturbance in homeostasis and an increase in autonomic nervous system dysfunction. This has implications for further research, including dysrhythmia risk, and monitoring of athletes in advising a return to strenuous activity.

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Influence of Obesity on Heart Rate Variability in Nurses with Age and Shift Type as Moderators

BioMed Research International ◽

10.1155/2021/8119929 ◽

2021 ◽

Vol 2021 ◽

pp. 1-10

Author(s):

Wen-Pei Chang ◽

Chia-Hui Wang ◽

Yen-Kuang Lin

Keyword(s):

Heart Rate ◽

Heart Rate Variability ◽

Negative Impact ◽

Low Frequency ◽

High Body Mass Index ◽

The Body ◽

Autonomic Nerve ◽

Shift Type ◽

Interaction Term ◽

High Bmi

Obesity is a risk factor of cardiovascular disease-related mortality and may be associated with changes in the autonomic nerve activity. Nurses working shifts and caring for patients are under great mental and physical pressure, and research has proven that these can negatively affect the body. The objective of this study was to examine the influence of obesity in nurses on their heart rate variability (HRV) and determine whether age or shift type moderates this influence. A questionnaire survey and HRV measurements were conducted on nurses at a hospital in Taiwan during a routine employee health checkup. HRV analysis was conducted using a noninvasive HRV monitor for five minutes. A total of 242 nurses with a mean age of 28.98 ± 6.56 years were enrolled in this study. An overly large waist circumference (WC) had a negative impact on high frequency (HF), low frequency (LF), and standard deviation of normal-to-normal interval (SDNN), while an overly high body mass index (BMI) had a negative impact on very low frequency (VLF) and SDNN. The interaction term “overly large WC × age” had a negative impact on HF ( β = − 0.21 , p = 0.010 ) and LF ( β = − 0.18 , p = 0.030 ), whereas the interaction term “overly high BMI×age” had a negative impact on HF ( β = − 0.27 , p = 0.001 ), LF ( β = − 0.19 , p = 0.023 ), and VLF ( β = − 0.17 , p = 0.045 ). The interaction terms “overly large WC × shift type” and “overly high BMI × shift type” did not influence any HRV parameters. As age increased, so did the degree to which the HF and LF of nurses with an overly large WC were lower than normal, and so did the degree to which the HF, LF, and VLF of nurses with an overly high BMI were lower than normal.

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