What is the adequate sampling interval of the ECG signal for heart rate variability analysis in the time domain?

Sampling rate requirement for accurate calculation of heart rate and its variability based on the electrocardiogram

Objective. To develop analytical formulas which can serve as quantitative guidelines for the selection of the sampling rate for the electrocardiogram (ECG) required to calculate heart rate (HR) and heart rate variability (HRV) with a desired level of accuracy.Approach. We developed analytical formulas which relate the ECG sampling rate to conservative bounds on HR and HRV errors: (i) one relating HR and sampling rate to a HR error bound and (ii) the others relating sampling rate to HRV error bounds (in terms of root-mean-square of successive differences (RMSSD) and standard deviation of normal sinus beats (SDNN)). We validated the formulas using experimental data collected from 58 young healthy volunteers which encompass a wide HR and HRV ranges through strenuous exercise.Main results. The results strongly supported the validity of the analytical formulas as well as their tightness. The formulas can be used to (i) predict an upper bound of inaccuracy in HR and HRV for a given sampling rate in conjunction with HR and HRV as well as to (ii) determine a sampling rate to achieve a desired accuracy requirement at a given HR or HRV (or its range).Significance. HR and its variability (HRV) derived from the ECG have been widely utilized in a wide range of research in physiology and psychophysiology. However, there is no established guideline for the selection of the sampling rate for the ECG required to calculate HR and HRV with a desired level of accuracy. Hence, the analytical formulas may guide in selecting sampling rates for the ECG tailored to various applications of HR and HRV.

Uncertainties in the Analysis of Heart Rate Variability: A Systematic Review

Heart rate variability (HRV) is an important metric with a variety of applications in clinical situations such as cardiovascular diseases, diabetes mellitus, and mental health. HRV data can be potentially obtained from electrocardiography and photoplethysmography signals, then computational techniques such as signal filtering and data segmentation are used to process the sampled data for calculating HRV measures. However, uncertainties arising from data acquisition, computational models, and physiological factors can lead to degraded signal quality and affect HRV analysis. Therefore, it is crucial to address these uncertainties and develop advanced models for HRV analysis. Although several reviews of HRV analysis exist, they primarily focus on clinical applications, trends in HRV methods, or specific aspects of uncertainties such as measurement noise. This paper provides a comprehensive review of uncertainties in HRV analysis, quantifies their impacts, and outlines potential solutions. To the best of our knowledge, this is the first study that presents a holistic review of uncertainties in HRV methods and quantifies their impacts on HRV measures from an engineer's perspective. This review is essential for developing robust and reliable models, and could serve as a valuable future reference in the field, particularly for dealing with uncertainties in HRV analysis.

Effects of anterior thalamic nucleus DBS on interictal heart rate variability in patients with refractory epilepsy

OBJECTIVE

Heart rate variability (HRV) changes were investigated by several studies after resective epilepsy surgery/vagus nerve stimulation. We examined anterior thalamic nucleus (ANT)-deep brain stimulation (DBS) effects on HRV parameters.

METHODS

We retrospectively analyzed 30 drug-resistant epilepsy patients' medical record data and collected electrocardiographic epochs recorded during video- electroencephalography monitoring sessions while awake and during N1- or N2-stage sleep pre-DBS implantation surgery, post-surgery but pre-stimulation, and after stimulation began.

RESULTS

The mean square root of the mean squared differences between successive RR intervals and RR interval standard deviation values differed significantly (p < 0.05) among time-points, showing increased HRV post-surgery. High (0.15-0.4 Hz) and very low frequency (<0.04 Hz) increased, while low frequency (0.04-0.15 Hz) and the LF/HF ratio while awake decreased, suggesting improved autonomic regulation post-surgery. Change of effect size was larger in patients where both activated contacts were located in the ANT than in those where only one or none of the contacts hit the ANT.

CONCLUSIONS

In patients with drug-resistant epilepsy, ANT-DBS might positively influence autonomic regulation, as reflected by increased HRV.

SIGNIFICANCE

To gain a more comprehensive outcome estimation after DBS implantation, we suggest including HRV measures with seizure count in the post-surgery follow-up protocol.

Can Heart Rate Variability (HRV) Be Used as a Biomarker of Thermal Comfort for Mine Workers?

This study aimed to determine whether heart rate variability (HRV) can express the thermal comfort of mine workers. Eight subjects ran on a treadmill (5.5 km/h) to simulate heavy labor in three kinds of mining environments (22 °C/90%, 26 °C/90%, 30 °C/90%), respectively. Based on the measured electrocardiogram (ECG) data, the HRV of the subjects was calculated. The results showed that the HRV indices changed obviously under different temperature environments. In the neutral and hot environment, except for the LF, TP and LF/HF, there were significant differences in each index. However, there was no significant difference between the cold and neutral environments. The R-R intervals, the very low-frequency power (VLF), pNN20 and SampEN had strong negative correlation with the thermal sensation of people from sitting to work (ρ < −0.700). These indices may be used as thermal comfort predictive biomarkers of mine workers.

Optimizing sampling rate of wrist-worn optical sensors for physiologic monitoring

Introduction

Personalized medicine has exposed wearable sensors as new sources of biomedical data which are expected to accrue annual data storage costs of approximately $7.2 trillion by 2020 (>2000 exabytes). To improve the usability of wearable devices in healthcare, it is necessary to determine the minimum amount of data needed for accurate health assessment.

Methods

Here, we present a generalizable optimization framework for determining the minimum necessary sampling rate for wearable sensors and apply our method to determine optimal optical blood volume pulse sampling rate. We implement t-tests, Bland-Altman analysis, and regression-based visualizations to identify optimal sampling rates of wrist-worn optical sensors.

Results

We determine the optimal sampling rate of wrist-worn optical sensors for heart rate and heart rate variability monitoring to be 21-64 Hz, depending on the metric.

Conclusions

Determining the optimal sampling rate allows us to compress biomedical data and reduce storage needs and financial costs. We have used optical heart rate sensors as a case study for the connection between data volumes and resource requirements to develop methodology for determining the optimal sampling rate for clinical relevance that minimizes resource utilization. This methodology is extensible to other wearable sensors.

Impact of observational error on heart rate variability analysis

An observational error of heart rate variability (HRV) may arise from many factors, such as a limited sampling frequency, QRS complexes detection process, preprocessing procedures and others. In our study, we focused on the first two origins of measurement error. We introduced a model of observational error and suggested universal descriptors for the assessment of its resultant magnitude in terms of time, frequency as well as nonlinear parameters. For this purpose, we applied Monte Carlo simulations which showed that the most sensitive to observational error are: pNN50 (the proportion of pairs of successive RR intervals that differ by more than 50 ms) and markers obtained from frequency analysis. On the other hand, the most resistant are other time domain parameters as well as the short and long-term slopes of Detrended Fluctuation Analysis (DFA). We postulate that the observational error should be considered in population studies, when different recorders are used in the research centres. Additionally, in the case of patients with similar etiology of disease but with different heart rhythms abnormalities the scatter of HRV parameters will also be observed due to the subject's the time series variability.

Enhancing the Robustness of Smartphone Photoplethysmography: A Signal Quality Index Approach

Heart rate variability (HRV) provides essential health information such as the risks of heart attacks and mental disorders. However, inconvenience related to the accurate detection of HRV limits its potential applications. The ubiquitous use of smartphones makes them an excellent choice for regular and portable health monitoring. Following this trend, smartphone photoplethysmography (PPG) has recently garnered prominence; however, the lack of robustness has prevented both researchers and practitioners from embracing this technology. This study aimed to bridge the gap in the literature by developing a novel smartphone PPG quality index (SPQI) that can filter corrupted data. A total of 226 participants joined the study, and results from 1343 samples were used to validate the proposed sinusoidal function-based model. In both the correlation coefficient and Bland–Altman analyses, the agreement between HRV measurements generated by both the smartphone PPG and the reference electrocardiogram improved when data were filtered through the SPQI. Our results support not only the proposed approach but also the general value of using smartphone PPG in HRV analysis.

Design and implementation of an ultra-low energy FFT ASIC for processing ECG in Cardiac Pacemakers

In embedded biomedical applications, spectrum analysis algorithms such as Fast Fourier Transform (FFT) are crucial for pattern detection and has been the focus of continued research. In deeply embedded systems such as cardiac pacemakers, FFT based signal processing is typically computed by Application Specific Integrated Circuits (ASIC) to achieve low power operation. This research proposes a data driven design approach for an FFT ASIC solution which exploits the limited range of data encountered by these embedded systems. The optimizations proposed in this paper uses the simple concept of Hashing and Look-Up Tables (LUT) to effectively reduce the number of arithmetic operations required to perform the FFT of an electrocardiogram (ECG) signal. By reducing the dynamic power consumption and overall energy footprint of FFT computation, the proposed design aims to achieve longer battery life for a Cardiac Pacemaker. The design is synthesized using a 90nm standard cell library, and gate level switching activity is simulated to obtain accurate power consumption results. The proposed optimizations achieved a low energy consumption of 27.72nJ per FFT, which is 14.22% lower than a standard 128-point radix-2 FFT when tested with actual ECG data collected from PhysioNet.

The acute effects of joint manipulative techniques on markers of autonomic nervous system activity: a systematic review and meta-analysis of randomized sham-controlled trials

Background

The autonomic nervous system (ANS) interests many chiropractors and manual therapists, because joint manipulative techniques (JMT), e.g. high velocity low amplitude (HVLA) manipulations and mobilizations, appear to produce acute changes in ANS mediated physiology. The complexity of this issue justifies a systematic critical literature review.

Objective

To review the literature comparing the acute changes in markers of ANS activity between JMT applied on spinal or peripheral joints and a sham procedure in healthy or symptomatic subjects.

Method

We searched PsycINFO, PEDro, PubMed, Cochrane library, EMBASE, and Medline up to December 2017. We updated the search with PubMed, Cochrane library, EMBASE, and Medline including July 2018. Inclusion criteria were: randomized sham-controlled trials assessing the effect of JMT on markers of ANS activity; manually applied JMT, regardless of technique, applied on either healthy or symptomatic humans; outcome measurements recorded at baseline and repeated during and/or after interventions. Selection of articles and data extraction were performed independently by two reviewers. The quality of studies was assessed using the Cochrane ‘risk of bias’ tool and a technical check-list. Results were reported narratively with some meta-analyses. The Cochrane GRADE approach was used to assess the certainty of evidence.

Results

Twenty-nine of 2267 studies were included in the synthesis. Mobilizations (oscillatory technique) probably produce an immediate and short-term, bilateral increase in skin sympathetic nerve activity (reflected by an increase in skin conductance) regardless of the area treated (moderate-certainty evidence). It is uncertain whether the sympathetic arousal also explains an increase in respiratory rate (very low-certainty evidence). Our evaluation of the literature suggests that spinal sustained apophyseal glides (SNAGs) mobilization and HVLA manipulation of the spine may have no acute effect on the studied markers of ANS activity (very low- to low-certainty evidence).

Conclusion

Some types of mobilizations probably produce an immediate and short-term, statistically significant increase in skin sympathetic nerve activity when compared to a sham procedure, whereas spinal SNAGs and spinal HVLA techniques may have no acute effect on the studied markers of ANS activity. No region-specific results were noted. The literature suffers from several shortcomings, for which reason we strongly suggest further research.

Electronic supplementary material

The online version of this article (10.1186/s12998-019-0235-1) contains supplementary material, which is available to authorized users.

HEART-RATE BASED SLEEP APNEA DETECTION USING ARDUINO

The purpose of this study was to investigate the use of a cost-effective heart rate monitor sensor and Arduino Uno configuration to accurately detect simulated sleep apnea, through the use of the inter-beat interval (R-R interval). Three separate 30[Formula: see text]min heart rate recordings were taken, each with six simulated sleep apnea events ranging from 20 to 40[Formula: see text]s. The results were gathered and processed to identify the simulated sleep apnea events. In each of the recordings, the simulated sleep apnea events were visible and the key characteristics, surrounding the events, could be recognized. The heart rate monitor sensor and Arduino Uno configuration successfully detected the simulated sleep apnea events through the analysis and processing of the hearts R-R interval.

Transcutaneous Carbon Dioxide Treatment Affects Heart Rate Variability - A Pilot Study

BACKGROUND

The aim of this study was to investigate the effects of carbon-dioxide treatment on heart rate variability (HRV) parameters: mean RR interval (RRI), standard deviation of RR intervals (SDNN), root mean square of successive RR differences (RMSSD); and Porta and Guzik indices, as measures of heart rate asymmetry.

MATERIALS AND METHODS

Twenty patients were enrolled (mean±SD, age=59±7.8 years). Measurements were performed before CO₂ treatment, at the beginning of treatment, at 15 min of treatment, immediately after and 1 h after the treatment.

RESULTS

Significant increase in SDNN was found 1 h after the treatment when compared to that before it (p=0.011). There were no significant changes in other parameters.

CONCLUSION

CO₂ treatment can influence the autonomic nervous system identified by SDNN changes. However, larger studies are required to confirm these results.

Impact of supportive therapy modalities on heart rate variability in cancer patients - a systematic review

Purpose: To systematically review literature for interventional studies and their impact on autonomic dysfunction assessed by heart rate variability in cancer patients.Methods: Research was conducted using the databases Medline/Pubmed, Scopus, and Web of science from their inception to October 2017. Original articles with an interventional design that reported changes in at least one heart rate variability parameter as outcome parameter were included and described.Results: Ten studies were identified as eligible for subsequent analysis. The main application field in oncological therapy setting was music therapy intervention, Traditional Chinese Medicine related treatments, exercise interventions, relaxation, and myofascial release techniques. Breast cancer was the most frequently described single cancer entity. Heart rate variability recording was performed with standard electrocardiography devices or wearable heart rate monitors, within a time range between 5 and 20 min and a sampling rate varying from 200 to 1000 Hz. No adverse events were reported in all studies.Conclusions: Supportive therapy modalities may have the potential to enhance vegetative functioning. In this context, heart rate variability analysis appears to be an easily applicable and safe method to evaluate cancer related autonomic dysfunction. More large prospective multicentre randomised controlled trials are needed.Implication for rehabilitationMost cancer patients face autonomic dysfunction due to the disease itself the applied treatments or combination of both.HRV measurement is an easy and safe method to asses autonomic dysfunction.Supportive treatments targeting on an elevation of the vagal tone and autonomic balance in general might have beneficial effects for cancer patients.

Experimental study on the human thermal comfort based on the heart rate variability (HRV) analysis under different environments

In order to study the human thermal comfort under different environments, the electrocardiogram (ECG) data of 6 subjects were recorded continuously under 60 environments composed by different air temperature, relative humidity and air speed that were created by an environmental chamber. Based on the ECG data, the frequency-domain method was adopted to obtain the heart rate variability (HRV) results. Among the HRV indices, the ratio of the low frequency power and high frequency power of the HRV analysis results (LF/HF), which reflects the balance of the autonomic nervous system, was selected as an indicator of the thermal comfort in the study. And the effects of air temperature, relative humidity and air speed on LF/HF were scrutinized. Meanwhile, a questionnaire survey was conducted during the experiment to evaluate the thermal comfort of the subjects. And the relationships between mean LF/HF and thermal sensation, mean thermal comfort were established based on the survey. The results showed that different LF/HF was observed under different environments, and that the air temperature had the most significant effects on LF/HF. The changes in the air temperature could easily lead to the excitation of the sympathetic nerve that could promote the activities of the thermoregulatory effectors thus thermal discomfort. Additionally, the fitting curves illustrating the relationships between LF/HF and thermal sensation and thermal comfort showed that the higher LF/HF yielded thermal discomfort, while the low LF/HF indicated a thermally acceptable state.

Comment on 'Photoplethysmography sampling frequency: pilot assessment of how low can we go to analyze pulse rate variability with reliability?'

Accurate pulse rate detection is essential for reliable pulse rate variability analysis. On the other hand, minimizing the sampling frequency is essential to reduce the amount of data and computational needs, and consequently the power consumption of mobile/wearable devices, extending their operating hours. Determining the variability of physiological parameters needs a new paradigm since there is a limited possibility of calculating an average eliminating random error of measurement. Finding the optimal sampling rate depends on the actual investigation, the expected variability and variability-changes of the study-population in order to get valid HRV parameters.

Reply to 'Comment on Photoplethysmography sampling frequency: pilot assessment of how low can we go to analyze pulse rate variability with reliability?'

In his Comment, Hejjel argued that some contents previously published by us were inappropriate for the statistical analysis of pulse rate variability due to high inter-individual dispersion. He also claimed that data collection over 5 min for short-term HRV analysis and data collection for an abnormal range of people were required. In order to give our perspective on these issues, we will discuss and clarify some of the existing literature and our own work on this subject, underlining the difference between electrocardiogram and photoplethysmogram.

A Single Session of Autogenic Training Increases Acute Subjective and Physiological Sexual Arousal in Sexually Functional Women

Heart rate variability (HRV) has recently been associated with female sexual function (Stanton, Lorenz, Pulverman, & Meston, 2015). Below-average HRV was identified as a possible risk factor for sexual arousal dysfunction and overall sexual dysfunction in women. Based on this newly established relationship between HRV and female sexual function, the present study examined the effect of autogenic training to increase HRV on acute physiological and subjective sexual arousal in women. Specifically, vaginal pulse amplitude (VPA), an index of genital sexual arousal, and subjective sexual arousal were assessed in 33 sexually functional women, aged 18 to 27, before and after a short session of autogenic training. Autogenic training, a relaxation technique that restores the balance between the activity of the sympathetic and the parasympathetic branches of the autonomic nervous system, has been shown to significantly increase HRV (Miu, Heilman, & Miclea, 2009). After autogenic training, significant increases in both VPA (p <.05) and subjective sexual arousal (p <.005) were observed. Moreover, change in HRV from pre- to postmanipulation significantly moderated changes in subjective sexual arousal (p <.05) when it was measured continuously during the presentation of the erotic stimulus. This cost-effective, easy-to-administer behavioral intervention may have important implications for increasing sexual arousal in women.

Noncontact measurement of emotional and physiological changes in heart rate from a webcam

Heart rate, measured in beats per minute, can be used as an index of an individual's physiological state. Each time the heart beats, blood is expelled and travels through the body. This blood flow can be detected in the face using a standard webcam that is able to pick up subtle changes in color that cannot be seen by the naked eye. Due to the light absorption spectrum of blood, we are able to detect differences in the amount of light absorbed by the blood traveling just below the skin (i.e., photoplethysmography). By modulating emotional and physiological stress-that is, viewing arousing images and sitting versus standing, respectively-to elicit changes in heart rate, we explored the feasibility of using a webcam as a psychophysiological measurement of autonomic activity. We found a high level of agreement between established physiological measures, electrocardiogram, and blood pulse oximetry, and heart rate estimates obtained from the webcam. We thus suggest webcams can be used as a noninvasive and readily available method for measuring psychophysiological changes, easily integrated into existing stimulus presentation software and hardware setups.

Photoplethysmography sampling frequency: pilot assessment of how low can we go to analyze pulse rate variability with reliability?

Pulse rate variability (PRV) analysis appears as the first alternative to heart rate variability analysis for wearable devices; however, there is a constraint on computational load and energy consumption for the limited system resources available to the devices. Considering that adjustment of the sampling frequency is one of the strategies for reducing computational load and power consumption, this study aimed to investigate the influence of sampling frequency (f _s) on PRV analysis and to find the minimum sampling frequency while maintaining reliability. We generated 5000, 2500, 1000, 500, 250, 100, 50, 25, 20, 15, 10, 5 Hz down-sampled photoplethysmograms from 10 kHz-sampled PPGs and derived time- and frequency-domain variables of the PRV. These included AVNN, SDNN, SDSD, RMSSD, NN50, pNN50, total power, VLF, LF, HF, LF/HF, nLF and nHF for each down-sampled signal. Derived variables were compared with heart rate variability of the 10 kHz-sampled electrocardiograms, and then statistically investigated using one-way ANOVA test and Bland-Altman analysis. As a result, significant differences (P  <  0.05) were found for SDNN, SDSD, RMSSD, NN50, pNN50, TP, HF, LF/HF, nLF and nHF, but not for AVNN, VLF and LF. Based on the post hoc tests, it was found that the NN50 and pNN50, SDSD and RMSSD, LF/HF and nHF, SDNN, TP and nLF analysis had significant differences at f _s  ⩽  20 Hz, f _s  ⩽  15 Hz, f _s  ⩽10 Hz; f _s  =  5 Hz, respectively. In other words, a significant difference was not seen for any variable if the f _s was greater than 25 Hz. Consequently, our pilot study suggests that analysis of variability in the time and frequency domain from pulse rate obtained through PPG may be potentially as reliable as that derived from the analysis of the electrocardiogram, provided that f _s  ⩾25 Hz sampling frequency is used.

Vagal Activity During Physiological Sexual Arousal in Women With and Without Sexual Dysfunction

Recently, heart rate variability (HRV) level has been found to be a risk factor for female sexual dysfunction. Low HRV was a significant predictor of female sexual arousal dysfunction and overall sexual dysfunction. Building upon this finding, the present study examined whether differences in vagal activity between sexually functional and sexually dysfunctional women may be driving the association between low HRV and female sexual dysfunction. Specifically, respiratory sinus arrhythmia (RSA) was assessed before, during, and after physiological sexual arousal in 84 women, aged 18 to 47, to examine potential differences in vagal activity between sexually functional and sexually dysfunctional women. Significant differences in vagal activity between these two groups were observed (p =.02). These findings provide additional specificity to the recently established relationship between HRV and female sexual function while also proposing a mechanism to target during treatments for sexual dysfunction.

Is 50 Hz high enough ECG sampling frequency for accurate HRV analysis?

With the worldwide growth of mobile wireless technologies, healthcare services can be provided at anytime and anywhere. Usage of wearable wireless physiological monitoring system has been extensively increasing during the last decade. These mobile devices can continuously measure e.g. the heart activity and wirelessly transfer the data to the mobile phone of the patient. One of the significant restrictions for these devices is usage of energy, which leads to requiring low sampling rate. This article is presented in order to investigate the lowest adequate sampling frequency of ECG signal, for achieving accurate enough time domain heart rate variability (HRV) parameters. For this purpose the ECG signals originally measured with high 5 kHz sampling rate were down-sampled to simulate the measurement with lower sampling rate. Down-sampling loses information, decreases temporal accuracy, which was then restored by interpolating the signals to their original sampling rates. The HRV parameters obtained from the ECG signals with lower sampling rates were compared. The results represent that even when the sampling rate of ECG signal is equal to 50 Hz, the HRV parameters are almost accurate with a reasonable error.

Test-Retest Reliability of Pediatric Heart Rate Variability: A Meta-Analysis

Heart rate variability (HRV), an established index of autonomic cardiovascular modulation, is associated with health outcomes (e.g., obesity, diabetes) and mortality risk. Time- and frequency-domain HRV measures are commonly reported in longitudinal adult and pediatric studies of health. While test-retest reliability has been established among adults, less is known about the psychometric properties of HRV among infants, children, and adolescents. The objective was to conduct a meta-analysis of the test-retest reliability of time- and frequency-domain HRV measures from infancy to adolescence. Electronic searches (PubMed, PsycINFO; January 1970-December 2014) identified studies with nonclinical samples aged ≤ 18 years; ≥ 2 baseline HRV recordings separated by ≥ 1 day; and sufficient data for effect size computation. Forty-nine studies (N = 5,170) met inclusion criteria. Methodological variables coded included factors relevant to study protocol, sample characteristics, electrocardiogram (ECG) signal acquisition and preprocessing, and HRV analytical decisions. Fisher's Z was derived as the common effect size. Analyses were age-stratified (infant/toddler < 5 years, n = 3,329; child/adolescent 5-18 years, n = 1,841) due to marked methodological differences across the pediatric literature. Meta-analytic results revealed HRV demonstrated moderate reliability; child/adolescent studies (Z = 0.62, r = 0.55) had significantly higher reliability than infant/toddler studies (Z = 0.42, r = 0.40). Relative to other reported measures, HF exhibited the highest reliability among infant/toddler studies (Z = 0.42, r = 0.40), while rMSSD exhibited the highest reliability among child/adolescent studies (Z = 1.00, r = 0.76). Moderator analyses indicated greater reliability with shorter test-retest interval length, reported exclusion criteria based on medical illness/condition, lower proportion of males, prerecording acclimatization period, and longer recording duration; differences were noted across age groups. HRV is reliable among pediatric samples. Reliability is sensitive to pertinent methodological decisions that require careful consideration by the researcher. Limited methodological reporting precluded several a priori moderator analyses. Suggestions for future research, including standards specified by Task Force Guidelines, are discussed.

Heart rate variability measure in breast cancer patients and survivors: A systematic review

PURPOSE

In the current study, we aimed to review literature findings showing the clinical importance of cardiac autonomic modulation assessed by heart rate variability analysis in breast cancer (BC) patients and survivors.

METHODS

We conducted a systematic review according to The PRISMA Statement in Medline, Scopus and Web of Science (_-2015) databases. The search was limited to articles in English language, published in peer-reviewed journals, and with adult age samples only (e.g., women, patients, or survivors, diagnosed with BC in any stage). We included observational studies and randomized trials. Detailed heart rate variability analysis (instruments, data collection protocol, and analysis methods) was required. Search terms included autonomic nervous system, heart rate variability, sympathetic and parasympathetic nervous system, autonomic dysfunction, vagal nervous and breast neoplasms, breast cancer and breast tumor.

RESULTS

Twelve studies were included in this review. The clinical importance of cardiac autonomic modulation assessed by heart rate variability analysis in BC patients and survivors is demonstrated by association with effects of BC surgery, and treatments, and the adverse effects of surgery and treatments on survivors (e.g., cardiotoxicity, fatigue, and stress).

LIMITATIONS

The strength of evidence of included studies is low: small samples size and heterogeneity, presence of confounders, and observational studies design.

CONCLUSIONS

The heart rate variability analysis could be used as a complementary non-invasive tool for the early diagnosis and better prognosis of autonomic dysfunction, and survival in BC patients. There are many potential clinical applications of heart rate variability analysis in BC patients, and the employment of such approaches could lead to lower impairment of autonomic function in this individuals.

Heart Rate Variability: A Risk Factor for Female Sexual Dysfunction

Heart rate variability (HRV) is a measure of autonomic nervous system activity, which reflects an individual's ability to adapt to physiological and environmental changes. Low resting HRV has been linked to several mental health conditions, including depression, anxiety, and alcohol dependence (Kemp et al. in Biological Psychiatry 67(11):1067-1074, 2010. doi:10.1016/j.biopsych.2009.12.012; Kemp et al. in PloS One, 7(2):e30777, 2012; Quintana et al. in Drug and Alcohol Dependence, 132(1-2):395-398, 2013. doi:10.1016/j.drugalcdep.2013.02.025). HRV has also been used as a method for indexing the relative balance of sympathetic nervous system (SNS) activity to parasympathetic nervous system activity. This balance--in particular, moderately dominant SNS activity--has been shown to play a significant role in women's genital sexual arousal in the laboratory; however, the role of SNS activity in clinically relevant sexual arousal function is unknown. The present study assessed the feasibility of using HRV as an index of women's self-reported sexual arousal function outside the laboratory. Sexual arousal function, overall sexual function, and resting HRV were assessed in 72 women, aged 18-39. Women with below average HRV were significantly more likely to report sexual arousal dysfunction (p < .001) and overall sexual dysfunction (p < .001) than both women with average HRV and women with above average HRV. In conclusion, low HRV may be a risk factor for female sexual arousal dysfunction and overall sexual dysfunction.

Physiological and behavioral indices of emotion dysregulation as predictors of outcome from cognitive behavioral therapy and acceptance and commitment therapy for anxiety

BACKGROUND AND OBJECTIVES

Identifying for whom and under what conditions a treatment is most effective is an essential step toward personalized medicine. The current study examined pre-treatment physiological and behavioral variables as predictors and moderators of outcome in a randomized clinical trial comparing cognitive behavioral therapy (CBT) and acceptance and commitment therapy (ACT) for anxiety disorders.

METHODS

Sixty individuals with a DSM-IV defined principal anxiety disorder completed 12 sessions of either CBT or ACT. Baseline physiological and behavioral variables were measured prior to entering treatment. Self-reported anxiety symptoms were assessed at pre-treatment, post-treatment, and 6- and 12-month follow-up from baseline.

RESULTS

Higher pre-treatment heart rate variability was associated with worse outcome across ACT and CBT. ACT outperformed CBT for individuals with high behavioral avoidance. Subjective anxiety levels during laboratory tasks did not predict or moderate treatment outcome.

LIMITATIONS

Due to small sample sizes of each disorder, disorder-specific predictors were not tested. Future research should examine these predictors in larger samples and across other outcome variables.

CONCLUSIONS

Lower heart rate variability was identified as a prognostic indicator of overall outcome, whereas high behavioral avoidance was identified as a prescriptive indicator of superior outcome from ACT versus CBT. Investigation of pre-treatment physiological and behavioral variables as predictors and moderators of outcome may help guide future treatment-matching efforts.

Pain-related autonomic response is modulated by the medial prefrontal cortex: An ECG-fMRI study in men

BACKGROUND

Our goal was to identify brain structures responsible for pain-related autonomic changes by the correlation of simultaneously acquired functional magnetic resonance imaging (fMRI) and electrocardiogram (ECG) data.

METHODS

Eighteen healthy men (age: 22.89 ± 1.96) were involved. Painful sensation was evoked by heat. Simultaneously recorded brain fMRI and ECG data during pain were compared to data acquired during a non-painful heat sensation. From the ECG data, time- and frequency domain parameters of heart rate variability (HRV) were extracted.

RESULTS

We found that: (1) among the common elements of both pain network and central autonomic network (CAN) only the medial prefrontal frontal cortex (MPFC) showed significant correlation with HRV; (2) the parasympathetic response to the painful stimuli showed a positive, while the sympathetic response a negative association with pain related BOLD-signal change observed in MPFC; (3) time domain parameters of HRV were negatively associated with MPFC activation.

CONCLUSIONS

The novelty of our study-compared to previous ECG-fMRI studies-is that we used pain as stimulus and investigated both frequency- and time-domain parameters of HRV. Compared to other stimuli used in earlier studies to activate the CAN, pain sensation can be standardized easier and might allow us to better understand the functional organization of CAN. The results of the current ECG-fMRI study may have direct clinical relevance in understanding the pathomechanisms of several clinical conditions.

PERSPECTIVE

There are some simultaneous ECG-fMRI and ECG-Positron Emission Tomography (PET) studies, but limited information is available about the pain-related brain function-HRV relations. The novelty of our study is that we used pain as stimulus to activate the central autonomic network and investigated both frequency- and time-domain parameters of HRV.

Chronic stress modulates neural and cardiovascular responses during reversal learning

Animal studies have revealed that chronic stress shifts cognitive strategies from the flexible goal-directed action to the simple and rigid habit action. In addition, stress-induced atrophy in the prefrontal cortex and dorsomedial striatum which are involved in the goal-directed action and hypertrophy of the dorsolateral striatum which is critical for the habit action were parallel with the effects of chronic stress on behaviors. The present study tested whether these previous findings in animal studies are compatible in humans by analyzing effects of chronic stress on neural and cardiovascular responses, which are likely important for performing appropriate actions. Twenty healthy men exposed to low or high chronic job stress performed a stochastic reversal learning task, which required cognitive flexibility and the goal-directed action. Regional cerebral blood flow was evaluated during the task using (15)O-water positron emission tomography, and cardiovascular parameters such as blood pressure and heart rate were also measured. During the reversal learning task, whereas participants with low chronic job stress exhibited activity in the anterior caudate, as well as orbitofrontal cortex, ventrolateral prefrontal cortex, insula, and midbrain, which might be related to the goal-directed action, participants with high chronic job stress exhibited no activity in such brain regions. Furthermore, participants with high chronic job stress exhibited less reactivity in diastolic blood pressure, which might be mediated by anterior cingulate cortical activity. These findings, in line with previous studies, suggested that chronic job stress correlates with less activity in brain regions related to the goal-directed action, and insensitive physiological responses in humans.

Heart rate variability in myocardial infarction and heart failure

The need to refine the identification of patients who might benefit from implantation of an implantable cardioverter defibrillator has been risen by the results of many clinical trials on ICD therapy. Traditional parameters such as left ventricular ejection fraction and the presence of non-sustained ventricular tachycardia were not strong enough to achieve this goal with reasonable cost-effectiveness. Heart rate variability (HRV) is one of the most popular parameters used to assess the autonomic tone. HRV has been reported as a strong predictor of cardiovascular mortality. Currently, three different categories of methods in HRV analysis are being used; the time domain, frequency domain, and non-linear dynamic analysis. Both time domain and frequency domain analyses of HRV have been investigated extensively regarding their use as a prognostic marker for cardiovascular mortality. The non-linear dynamic analysis is the latest tool that has shown to have an even higher predictive value than any of the traditional parameters. However, standardized and supporting evidence on this new technique is still lacking. In this article, the current role of HRV in the prediction of cardiovascular mortality in myocardial infarction and heart failure patients has been reviewed.

Heart rate variability: comparison among devices with different temporal resolutions

Several devices based on ECG can acquire beat-to-beat intervals, and some of these devices may be used for heart rate variability (HRV) analysis. Most of these devices and their methods to acquire the beat-to-beat intervals need to be validated for HRV analysis by comparing them against traditional methods. Some of these methods have low temporal resolution, which may be sufficient for certain studies. HRV analysis parameters obtained from two methods differing in temporal resolution were compared to the HRV analysis parameters obtained from a referent method (ECG). One of the methods had a high resolution (<1 ms) and the other method had a low resolution (10 ms). Seven healthy male volunteers participated in the study. The beat-to-beat intervals were collected simultaneously from the three methods and the HRV parameters derived from them were used for our comparisons. The Pearson product-moment correlations were used, which demonstrated an excellent correlation (r > 0.99) in time domain, frequency domain and some non-linear HRV measures. The HRV measures were further analyzed using the one-way repeated-measures analysis of variance (ANOVA) and statistically significant differences were observed in some of the HRV parameters obtained from the low-resolution method, especially the mean RR (p < 0.001) and the mean heart rate (p < 0.001). Since the same software was used for HRV analysis of the three methods, any differences were due to the temporal resolution of the RR intervals measured by the methods. Overall, both the methods correlated very well with the referent method among healthy volunteers in resting conditions and may be used by researchers for HRV studies.