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Heart rate variability: Origins, methods, and interpretive caveats
Abstract
Components of heart rate variability have attracted considerable attention in psychology and medicine and have become important dependent measures in psychophysiology and behavioral medicine. Quantification and interpretation of heart rate variability, however, remain complex issues and are fraught with pitfalls. The present report (a) examines the physiological origins and mechanisms of heart rate variability, (b) considers quantitative approaches to measurement, and (c) highlights important caveats in the interpretation of heart rate variability. Summary guidelines for research in this area are outlined, and suggestions and prospects for future developments are considered.
... In studies focusing on individuals with post-traumatic stress disorder (PTSD), patients displayed lower high-frequency HRV (HF-HRV) while processing neutral and trauma-related words [13]. HF-HRV, a noninvasive measure of vagal influences on parasympathetic heart innervation [14], reflects the body's adaptive physiological and emotional flexibility in response to immediate needs [10]. Another study on individuals with generalized anxiety disorder (GAD) observed that higher baseline connectivity between the bilateral amygdala and the prefrontal cortex/cingulum acts as a protective factor, leading to smaller decreases in HRV following mood induction [15]. ...
... All participants underwent comprehensive clinical assessments using the Mini International Neuropsychiatric Interview [14,15] and the Hamilton Anxiety Scale [18], following an initial screening involving the Liebowitz Social Anxiety Scale (LSAS) [19], Social Interaction Anxiety Scale (SIAS), Social Phobia Scale (SPS) [20], the brief version of the Fear of Negative Evaluation Scale (B-FNE) [21], and the Beck Depression Inventory (BDI) [22]. The inclusion criteria for the study were as follows: for the SAD group, LSAS ≥ 30, SIAS ≥ 34, and/or SPS ≥ 24; for the control group, SIAS ＜ 34, SPS ＜ 24, B-FNE ＜ 48, and BDI ＜ 21. ...
... We used segments of only 80 seconds to analyze HRV for each condition. However, existing literature suggests that blocks as short as 12.5 seconds are sufficient for HF-HRV analyses [13,14]. Moreover, previous studies have validated the use of concatenated PPG data from individual trials for analysis [49], supporting the validity of our approach. ...
... It can be quantified by various metrics, which fall into the two major categories of time-domain and frequency-domain measurements. Time-domain HRV measurements (e.g., the standard deviation of R-R intervals and root mean square of successive R-R interval differences) compute variability in the series of timing lengths of R-R intervals and are often expressed in original time units (i.e., millisecond) [29,32]. Frequencydomain HRV measures are derived by using the power spectral analysis and calculate the distribution of the power at different frequency bands, including ultra-low frequency (ULF), very-low frequency (VLF), low frequency (LF), and high frequency (HF) [29,32]. ...
... Time-domain HRV measurements (e.g., the standard deviation of R-R intervals and root mean square of successive R-R interval differences) compute variability in the series of timing lengths of R-R intervals and are often expressed in original time units (i.e., millisecond) [29,32]. Frequencydomain HRV measures are derived by using the power spectral analysis and calculate the distribution of the power at different frequency bands, including ultra-low frequency (ULF), very-low frequency (VLF), low frequency (LF), and high frequency (HF) [29,32]. Among those HRV indices, the root mean square of successive R-R intervals (RMSSD) and HF HRV have often been used as the indicators of cardiac vagal control in short-term (3-5 min) electrocardiography (ECG) assessments [29][30][31][32]. ...
... Frequencydomain HRV measures are derived by using the power spectral analysis and calculate the distribution of the power at different frequency bands, including ultra-low frequency (ULF), very-low frequency (VLF), low frequency (LF), and high frequency (HF) [29,32]. Among those HRV indices, the root mean square of successive R-R intervals (RMSSD) and HF HRV have often been used as the indicators of cardiac vagal control in short-term (3-5 min) electrocardiography (ECG) assessments [29][30][31][32]. Further, although there was a debate regarding the sources of other HRV metrics, current researchers generally agree that vagal input is the main source of most HRV metrics, including LF HRV and the ratio of the power of LF to HF HRV (LF/HF ratio) that were historically thought to reflect sympathetic control over cardiac activity [31,33]. ...
Background: Cardiovascular disease (CVD) is the leading cause of mortality and disability worldwide. While sex differences in CVD have been well documented, the physiological mechanisms of those sex differences remain unclear. As important components of the cardiovascular system, cardiac vagal control and baroreflex serve as mechanisms of sex differences in CVD and are modifiable factors for gender-specific CVD preventions. Methods: Ninety-four healthy adults (18–44 years of age; Mage = 21.09 years; 46 female) were recruited to complete the assessments of heart rate variability (HRV) at a resting baseline and the cardiac timing effect on an R-wave-locked reaction time (RT) task, which were used as the indicator of cardiac vagal control and a novel behavioral measure of baroreflex activity, respectively. HRV metrics (including the root mean square of successive R-R interval differences, high frequency and low frequency heart rate variability, and low frequency-to-high frequency ratio), the cardiac timing effect (the inhibition of RT response at the phase of cardiac systole compared to diastole), and their associations were compared between female and male participants. Results: Female participants showed higher levels of vagally mediated HRV after adjusting for basal resting heart rate. Importantly, the cardiac timing effect on RT responses was positively correlated with vagally mediated HRV among males but not among females. Conclusions: Females and males exhibited different physiological processes to regulate cardiovascular functions and behavioral outcomes. The present findings will help to reduce gender disparities in the preventive care of CVD and improve cardiovascular health for both women and men.
... Cardiac vagal activity (CVA), which represents the dynamic influence of vagally-mediated parasympathetic activity in regulating cardiac function, plays an important role in an individual's resilience to psychophysiological stresses and in preserving homeostasis [1][2][3]. Measuring heart rate variability (HRV) is a noninvasive way to analyze the variations in intervals between successive heartbeats and is primarily utilized to assess CVA [4,5]. Higher restingstate HRV indices, such as the root mean square of successive differences (RMSSD) in the time domain and high-frequency (HF) components in the frequency domain, indicate a greater influence of the vagus nerve on cardiac function, which in turn is associated with greater CVA [4,6]. ...
Developing strategies to enhance cardiac vagal activity (CVA) is essential for improving mood and managing stress. Although hypoxia inhalation may boost CVA, the optimal acute hypoxic conditions remain unclear. Therefore, we aimed to achieve a comprehensive understanding of the hypoxic conditions required to improve CVA and mood following hypoxia. Twenty-one healthy adults participated in both normobaric hypoxic (NH; FIO 2 : 13.5 %) and normoxic (NN; FIO 2 : 20.9 %) conditions. We monitored heart rate variability (HRV), per-cutaneous oxygen saturation (SpO 2), and mood across pre-, hypoxia, and post-sessions and assessed psycho-physiological stress using the Baevsky Stress Index (SI). Under hypoxia, SpO 2 decreased to 88.1 %, accompanied by reductions in vagally-mediated HRV, followed by supercompensation post-hypoxia. Additionally, mood declined during hypoxia but rapidly rebounded, correlating with CVA and SI fluctuations. These results indicate that acute low-dose hypoxic gas inhalation at FIO 2 : 13.5 % enhances CVA and mood post-hypoxia, offering a practical method for building resilience.
... This is plausibly a symptom of the fact that following the physical and mental relaxation induced by Yoga training, students were able to perceive less stress. In fact, HRV is an indicator of the activity of the sympathetic and parasympathetic nervous systems (Bernston et al., 1997;Shaffer et al., 2014;Thayer et al., 2009). Several studies have verified an increase in HRV index activity following meditation training (Ditto et al., 2006;Tang et al., 2009). ...
Introduction: The high-level athletic careers frequently conclude significantly earlier than those in other fields, and at times, despite the considerable efforts exerted, they do not consistently flourish as anticipated. Consequently, numerous athletes concurrently pursue academic pathways to adequately prepare for alternative professional opportunities beyond the realm of sports. Objective: Accordingly, the objective of the current investigation was to examine the efficacy of Yoga in ameliorating the stress levels experienced by student-athletes. Methodology: A cohort of 50 dual-career athletes with ages ranging from 18 to 25 years, was selected from five universities. The participants in the experimental group participated in a Yoga regimen in addition to their standard training protocol. In contrast, the participants within the control group continued to engage in conventional sport-specific training. Preceding and after the Yoga intervention, the students underwent psycho-physiological assessments, including the State Mindfulness Scale (SMS) and vagus-mediated heart rate variability (HRV). Results: The results indicated a significant Time x Group interaction effect for both the SMS and HRV, suggesting a substantial enhancement in the treatment groups. Discussion: This study confirmed that meditative practice through Yoga can be a source of improvement of psycho-physiological parameters in the context of interventions aimed at improving the well-being of dual career students Conclusions: In conclusion, there is a need to support and increase research in this area to have new and adequate information about the reality of the Dual Career and to be able to help student-athletes to reconcile school and sports paths.
... The LF band reflects a complex mix of sympathetic, vagal, and non-linear influences, showing the input of both the sympathetic and parasympathetic branches [3,25]. Because of this, the significant increase in LFs in the 30 minutes preceding AF is very difficult to interpret on its own. ...
Background: Neuromodulation has been shown to increase the efficacy of atrial fibrillation (AF) ablation procedures. However, despite its ability to influence the autonomic nervous system (ANS), the exact mechanism of action remains unclear. The activity of the ANS via the intracardiac nervous system (ICNS) can be inferred from heart rate variability (HRV). Therefore, this study aims to investigate the significance of changes in the ICNS prior to the onset of AF by analyzing the evolution of HRV in a large new cohort of patients. Methods: We selected and annotated recordings with AF and atrial flutter from our database of 95,871 Holter recordings. Each recording included both sinus rhythm and one or more AF episodes. We computed parameters estimating parasympathetic activity (root mean square of successive RR interval differences (RMSSD) and percentage of successive RR intervals that differ by more than 50 ms (pNN50)), as well as HRV frequential parameters a few minutes before AF onset. To allow a minute-by-minute assessment of the parameter changes, we computed their values over 5-minute sliding windows, starting at 35 minutes before AF onset. Results: The mean age of the whole group of patients was 71.1 ± 11.3 years (range 35-99), the total number of episodes was 1319 on 623 recordings from 570 patients, with an average of 2.1 ± 2.2 episodes per recording (range 1-17) and 2.3 ± 2.6 episodes per patient (range 1-21). The proportion of premature atrial contractions (PACs) increased from 4.8 ± 0.3%, 35 minutes before the onset of AF to 8.3 ± 0.4%, 5 minutes before the AF episode. We measured a statistically significant increase in very-low-frequency (VLF), low-frequency (LF), high-frequency (HF), RMSSD and pNN50 between 35 minutes and 5 minutes before AF onset. Conclusions: Our data suggest that a significant short-term increase in vagal activity precedes most AF events. Dynamic changes in HRV parameters could be considered when determining the optimal neuromodulation strategies. Keywords: atrial fibrillation; heart rate variability; autonomic nervous system; spectral analysis neuromodulation
... Evaluar la actividad del corazón y de todo el sistema cardiovascular (SCV) se vuelve imprescindible, por lo cual, una forma en la que se puede conocer lo que sucede en el SCV, es valorando de manera indirecta al SNA, siendo este el encargado del control de las funciones básicas del cuerpo como: la respiración, el metabolismo, los sistemas cardiovascular, digestivo hormonal e inmune, entre otros. Para evaluar el SNA se puede emplear el análisis de la VFC sugerido en [5]. En 1996 un grupo de expertos (Task Force) unificaron criterios para el análisis de la VFC [6], donde se establecen distintos métodos, entre los que destacan: los de análisis en el dominio del tiempo y de análisis en el dominio de la frecuencia. ...
This paper describes the processing of electrocardiographic (ECG) signals from 16 patients diagnosed with paroxysmal atrial fibrillation and sleep apnea-hypopnea syndrome (SAHS) classified as either moderate or severe by respiratory polygraphy. Processing goes from acquisition up to the analysis of their heart rate variability (HRV), where original computer scripts written in MATLAB R2020b are used within scripts adapted from other research groups. Computer processing included linear resampling, noise suppression, R-wave detection, misidentified peaks correction, tachogram resampling at a constant period and trend removal. Regular sampling is mandatory for Fourier analysis through Welch’s periodogram. Once the spectral power was estimated, the HRV was evaluated before, during and after an apnea episode. The behavior of the HRV was compared to the group of patients with moderate SAHS against those with severe SAHS. When comparing the groups at post-apnea stage, significant differences were found in the normalized low frequency band (LF: 0.04–0.15Hz, p=0.0183), and also in the normalized high frequency band (HF: 0.15–0.4 Hz, p=0.0182), which suggests that in patients with severe SAHS the sympathetic activity is higher (power in LF band), which in turn presupposes that the autonomic nervous system is in frequent alertness, which has been associated with high cardiovascular risk.
... For each 60s, if one R-peak was missing, an R-peak was inserted at a time point halfway between the two adjacent R-peaks. If more than one R-peak was missing, that specific 60-s period was not scored (Berntson et al., 1997). We extracted heart rate and root mean squared successive differences (RMSSD) in heart rate as a measure of heart rate variability (HRV). ...
Researchers have documented that exposure to different kinds of psychosocial stressors can lead to emotional difficulties and, further, that heightened reactivity to stress can moderate these associations. Recently, investigators have distinguished among threat, deprivation, and unpredictability as different dimensions of early life stress (ELS). It is not clear, however, whether reactivity in specific stress response systems functions as a diathesis to lead to emotional difficulties following exposure to these dimensions of ELS. In this study (N = 154) we examined whether stress reactivity, assessed across different psychobiological systems during the Trier Social Stress Test, is a unitary or multidimensional construct, and if reactivity differentially moderates the associations between ELS dimensions and adolescents’ susceptibility to emotional and behavioral problems two years later. A factor analysis conducted on stress reactivity measures yielded two factors: one composed of reactivity in heart rate, heart rate variability, and cortisol, and one composed of reactivity in skin conductance and self-reported mood. These two factors independently moderated the associations between early unpredictability and subsequent emotional problems. For each factor, the combination of higher unpredictability and higher stress reactivity predicted higher emotional problems; stress reactivity factors were not significant moderators of the effects of threat and deprivation. Our findings suggest that increased stress reactivity, assessed across several domains of functioning, functions as a diathesis that interacts with ELS characterized by unpredictability to predict subsequent mental health difficulties in adolescents and, further, that low stress reactivity buffers against mental health difficulties in adolescents who have experienced unpredictability early in life.
Discrimination (unfair treatment due to group membership) is relatively common among adolescents and has been linked to poor sleep and physical health. Individual differences in physiological functioning may moderate these associations. A sample of 323 youth (48% boys, 52% girls; 58.5% White, 40.9% Black, M age = 17.38 years, SD = 10.18 months) participated. Adolescents reported on discrimination and health, wore actigraphs to measure sleep, and came to the laboratory to assess respiratory sinus arrythmia reactivity (RSA-R) to two stressful tasks. Results indicate that discrimination was directly associated with health. Furthermore, discrimination interacted with RSA-R to predict sleep and health. Discrimination was related to more sleep activity and poorer health when RSA increased relative to baseline (augmentation), and better sleep quality (higher efficiency, fewer long wake episodes), when RSA decreased relative to baseline (suppression). Findings support the importance of examining physiological regulation as a protective/vulnerability factor when attempting to explicate relations between discrimination and health.
Contemporary findings reveal that autonomic control of dually innervated visceral organs does not lie along a single continuum extending from parasympathetic to sympathetic dominance. Rather, a bivariate autonomic space bounded by sympathetic and parasympathetic axes is the minimal representation necessary to capture the modes of autonomic control. We here empirically instantiate a quantitative bivariate model for the chronotropic control of the heart in humans. This model provides a more comprehensive characterization of psychophysiological response than simple measures of end-organ state and permits a differentiation of behavioral states and processes that would otherwise remain obscure. The model also illuminates and subsumes general principles such as the law of initial values and reveals a fundamental physiological rationale for the selection of heart period over heart rate as a metric for cardiac chronotropy. The present article also considers strategies for psychophysiological investigations within the autonomic space model, the limitations of these methods, and analytical tools for assessing their validity.
BL The first book devoted to human baroreflexes A comprehensive review of baroreflex involvement in human diseases, this book places the most recent understanding of human physiology solidly in the context of knowledge from animals. This book secures a place for human studies in the understanding of baroreflex physiology and pathophysiology and celebrates the advances made. By describing clearly the existing deficiencies in the understanding of baroreflex mechanisms, it points a way for future research in this exciting and important area of medical science. Nerve endings in the walls of the carotid sinuses and the aortic arch transduce arterial pressure changes and provide the central nervous system with a steady stream of encoded information. On the basis of this information, efferent autonomic neural activity is modulated finely, and the neurohumoral milieu of the heart and blood vessels is adjusted on a second-to-second basis. The arterial baroreflex may be the most important of the cardiovascular control mechanisms, because the baroreflex, above all other reflex mechanisms is the one whose speed is most adequate to respond rapidly to the abrupt transients of arterial pressure that occur in daily life. This book will help to fix a place for human studies in the understanding of baroreflex physiology and pathophysiology. It is intended as a celebration of the advances that have been made and, by describing clearly the existing deficiencies in the understanding of baroreflex mechanisms, it points a way for future research in this exciting and important area of medical science.
A unique text, relating the dramatic advances of modern neurobiology to the understanding of the structure and function of the autonomic nervous system. Written by an international group of distinguished scientists, it provides a clear view of the central neuronal components involved in autonomic control. Its scope is wide, ranging from anatomical pathways and molecular pharmacology to the perceptual qualities of autonomic sensation and their potential in modifying behaviour. The approach is mildly didactic, and combines concise background information with discussion of the latest research findings. It is richly illustrated with line drawings that concisely summarize concepts presented in the text.
We have demonstrated previously that transfer function analysis can be used to precisely characterize the respiratory sinus arrhythmia (RSA) in normal humans. To further investigate the role of the autonomic nervous system in RSA and to understand the complex links between respiratory activity and arterial pressure, we determined the transfer functions between respiration, heart rate (HR), and phasic, systolic, diastolic, and pulse arterial pressures in 14 healthy subjects during 6-min periods in which the respiratory rate was controlled in a predetermined but erratic fashion. Pharmacological autonomic blockade with atropine, propranolol, and both, in combination with changes in posture, was used to characterize the sympathetic and vagal contributions to these relationships, as well as to dissect the direct mechanical links between respiration and arterial pressure from the effects of the RSA on arterial pressure. We found that 1) the pure sympathetic (standing + atropine) HR response is characterized by markedly reduced magnitude at frequencies greater than 0.1 Hz and a phase delay, whereas pure vagal (supine + propranolol) modulation of HR is characterized by higher magnitude at all frequencies and no phase delay; 2) both the mechanical links between respiration and arterial pressure and the RSA contribute significantly to the effects of respiration on arterial pressure; 3) the RSA contribution to arterial pressure fluctuations is significant for vagal but not for sympathetic modulation of HR; 4) the mechanical effects of respiration on arterial pressure are related to the negative rate of change of instantaneous lung volume; 5) the mechanical effects have a higher magnitude during systole than during diastole; and 6) the mechanical effects are larger in teh standing than the supine position. Most of these findings can be explained by a simple model of circulatory control based on previously published experimental transfer functions from our laboratory.
1 Stationary Time Series.- 2 Hilbert Spaces.- 3 Stationary ARMA Processes.- 4 The Spectral Representation of a Stationary Process.- 5 Prediction of Stationary Processes.- 6* Asymptotic Theory.- 7 Estimation of the Mean and the Autocovariance Function.- 8 Estimation for ARMA Models.- 9 Model Building and Forecasting with ARIMA Processes.- 10 Inference for the Spectrum of a Stationary Process.- 11 Multivariate Time Series.- 12 State-Space Models and the Kalman Recursions.- 13 Further Topics.- Appendix: Data Sets.
Carotid baroreceptors of nine healthy young men and women were stretched or compressed with neck suction or pressure, before and after beta-adrenergic and cholinergic blockade, to evaluate several nonlinearities of sinus node baroreflex responses. Sinus node inhibition was related linearly to the intensity of brief baroreceptor stimuli over a range extending from carotid-distending pressures of about 101 +/- 5 (mean +/- SE) to 160 +/- 6 mm Hg (the subject's average systolic pressure was 108 +/- 2 mm Hg). Sinus node response to sustained (5 seconds) neck suction or pressure were strikingly asymmetrical. Responses were abolished by atropine, or by atropine and propranolol. Propranolol alone augmented sinus node responses to both neck suction and pressure. These results suggest that, in normal human subjects, sinus node responses to abrupt alterations of afferent baroreceptor traffic are nonlinear and are mediated by fluctuations of efferent cholinergic activity. Most of the observed nonlinear behavior of the integrated reflex can be explained on the basis of known properties of afferent and central portions of the baroreflex arc.
The heart period (R-R) variability power spectrum presents two components, at low (LF; similar to 0.10 Hz) and high (similar to 0.25 Hz) frequencies, whose reciprocal powers appear to furnish an index of sympathovagal interaction modulating heart rate. In addition, the LF component of the systolic arterial pressure variability spectrum furnishes a marker of sympathetic modulation of vasomotor activity. The contribution of spinal and supraspinal neural circuits to the genesis of these rhythmic oscillatory components remains largely unsettled. Therefore we performed spectral analysis of R-R and systolic arterial pressure variabilities in 15 chronic neurologically complete quadriplegic patients (QP) and in 15 control subjects during resting conditions, controlled respiration, and head-up tilt. At rest, in seven QP the LF component was undetectable in both cardiovascular variability spectra; in two QP this component was present only in R-R variability spectrum, whereas the remaining six showed a significantly reduced LF in both signals. In QP, the LF component, when present, underwent paradoxical changes with respect to controls, decreasing during tilt and increasing during controlled respiration. In five QP in whom the recording session was repeated after 6 mo, a significant increase in LF was observed in both variability spectra. These data confirm the finding that a disconnection of sympathetic outflow from supraspinal centers can cause the disappearance of the LF spectral component. However, LF presence in some QP supports the hypothesis of a spinal rhythmicity likely to be modulated by the afferent sympathetic activity.