Functional assessment of heart rate variability: physiological basis and practical applications

doi:10.1016/S0167-5273(02)00057-8

International Journal of Cardiology

Volume 84, Issue 1, July 2002, Pages 1-14

https://doi.org/10.1016/S0167-5273(02)00057-8 Get rights and content

Abstract

The autonomic nervous system dynamically controls the response of the body to a range of external and internal stimuli, providing physiological stability in the individual. With the progress of information technology, it is now possible to explore the functioning of this system reliably and non-invasively using comprehensive and functional analysis of heart rate variability. This method is already an established tool in cardiology research, and is increasingly being used for a range of clinical applications. This review describes the theoretical basis and practical applications for this emerging technique.

Introduction

One of the most interesting non-invasive diagnostic methods increasingly used in medicine is analysis of heart rate variability (HRV). Detailed and sophisticated analysis of fluctuation in heart rate can be used to indirectly assess autonomic control of the heart [1], [2], [3], [4], [5]. Change in the HRV pattern provides an early and sensitive indicator of compromised health [6], [7], [8], [9], [10]. A high variability in heart rate is a sign of good adaptability, implying a healthy individual with well functioning autonomic control mechanisms. Conversely, lower variability is often an indicator of abnormal and insufficient adaptability of the autonomic nervous system, implying the presence of a physiological malfunction in the individual for which further investigations are required to yield a specific diagnosis. Simple analysis of variation in heart rate has been used in clinical practice since the early 1960s, with reduced foetal HRV indicating that clinically significant hypoxia may be developing [11]. In the late 1970s, a reduction in HRV was first correlated with increased mortality and arrhythmic events in survivors of myocardial infarction [12]. More recently, reduced HRV has emerged as a strong indicator of risk related to adverse events in normal subjects [7], [13] and patients with a wide range of diseases [14], [15], [16], [17], [18], [19], reflecting the vital role the autonomic nervous system plays in maintaining health. The purpose of this review is to discuss physiological and technical aspects of HRV analysis, along with an overview of the research and clinical applications of the techniques.

Section snippets

Physiological background of HRV analysis

The cardiovascular system displays features typical of self-organising systems designed to achieve dynamical stability [20]. In the case of the cardiovascular system, stability is achieved by autonomically mediated control of heart rate, blood pressure and other factors which react rapidly to a range of internal and external stimuli such as acute ischaemia, metabolic imbalance and changes in physical or mental activity. In particular, heart rate varies in a complex reactive manner to these

Assessment of HRV by cardiovascular reflex testing

Early techniques for analysis of autonomic activity were based on evaluating heart rate changes evoked by stimulation of cardiovascular reflexes. One of the most widely used early sets for investigation of cardiovascular reflexes was proposed by Ewing et al. The Ewing ‘battery’ of tests includes measurement of heart rate changes induced by deep breathing, Valsalva-manoeuvre, orthostatic load and a hand-grip test [39]. The total Ewing score based on the results of the above tests provides a

Time domain analysis of HRV

These methods use mathematically simple techniques to measure the amount of variability present in a pre-specified time period in a continuous electrocardiogram [1], [21], [22], [23], [42]. After editing to remove non-sinus beats and artefact, the remaining normal to normal R–R intervals are measured and subjected to simple statistical analysis. The most commonly used technique is to plot a histogram of R–R interval duration against the number of R–R intervals in a 24-h period and then to

Frequency domain analysis of HRV

It is difficult to obtain precise physiological data about changes in autonomic function using relatively unsophisticated time domain analysis of HRV. Because of this, investigators have invested considerable time and effort in developing alternative techniques to investigate cyclical changes in HRV. Before this type of analysis can be performed, extensive editing and review of the electrocardiogram by an experienced operator is required to remove/edit non-sinus ectopic beats, pauses, tape

Comparison of time and frequency domain techniques for analysis of HRV

Some time and frequency domain HRV measurements are closely related [42]. Indices that measure beat to beat parasympathetically mediated HRV (rMSSD, sNN50 and high frequency power) and measures of the total amount of variability present in a long-term recording, such as SDNN and total spectral power, are strongly correlated. These time and frequency domain indices can therefore be used interchangeably. The HRV technique chosen for a particular study will depend on a variety of different

New analytical techniques

In the last decade a series of complex techniques have been developed to provide additional information over and above that available from standard time and frequency domain analysis of HRV. Investigators have recently reported on new time domain techniques that provide some information on sympathetic activity [57], [58], [59]. The techniques of peak — through analysis, complex demodulation and acceleration–deceleration oscillation analysis, are closely related and based on similar principles.

Practical applications of HRV analysis

In the last two decades, analysis of HRV has been extensively applied to the investigation of normal physiology. Prior to the HRV era, investigation of autonomic physiology required the use of complex highly invasive techniques in animal models or imprecise reflex based tests in humans. The use of HRV analysis has provided a simple reproducible method of non-invasive autonomic assessment. This has helped to clarify the role of the autonomic nervous system in regulating the cardiovascular

Conclusions

The autonomic nervous system plays a major role in normal physiological function and in the pathogenesis of many medical disorders. Measurement of HRV provides an easily applied non-invasive method of assessing autonomic function. Time domain techniques are mathematically simple and easy to apply to clinical quality ambulatory electrocardiograms. Frequency domain techniques are more complex and technically demanding, but provide more physiological information. Recent advances in computing hold

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Effects of exercise training on heart rate variability in individuals with lower extremity arterial disease and claudication: A systematic review
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To perform a systematic review of studies assessing the effects of regular exercise on heart rate variability (HRV) in individuals with lower extremity arterial disease (LEAD) and symptoms of claudication.
A systematic search in the electronic databases MEDLINE, Embase, and Scielo, was conducted and updated on January 21, 2023. Randomized clinical trials investigating patients with LEAD and IC, assessing ≥ 4 wk of exercise interventions, and reporting at least one HRV measure (e.g., time or frequency domains) at baseline and follow-up were included. Two reviewers independently screened studies for inclusion, performed data extraction, and quality assessment of included studies.
Data from 7 trials were included (i.e., 5 walking, 1 resistance, and 1 isometric handgrip training), totaling 327 patients (66% males; range: 61 - 68 yr; ankle brachial index: 0.4 - 0.7). Following exercise training, three studies investigating walking training reported an increase in parasympathetic modulation indices and/or a decrease in sympathetic modulation indices (n = 2) as well as an increase in non-linear indices (n = 1).
The current evidence is weak, and larger randomized controlled trials are needed to confirm the efficacy of exercise training in improving HRV. Additionally, the high divergence in the methodology of studies indicated the need for standard tools to improve the quality of HRV measurements in exercise trials. It is recommended to use standard procedures in future trials investigating HRV.
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Telemetry devices and pacemakers were implanted in beagle dogs (n = 6). HF was induced by ventricular pacing. Cardiac hemodynamics, plasma catecholamines and parameter describing the ANS ((heart rate variability (HRV), deceleration capacity (DC), and baroreflex sensitivity (BRS)) were continuously measured at baseline, during HF conditions and during recovery phase.
The pacing regime led to the expected depression in cardiac hemodynamics. Telemetric assessment of the ANS function showed a significant decrease in Total power, DC, and Heart rate recovery, whereas BRS was not significantly affected. In contrast, plasma catecholamines, revealing sympathetic activity, showed only a significant increase in the recovery phase.
A precise diagnostic of the ANS in the context of HF is becoming increasingly important in experimental models. Up to now, these models have shown many limitations. Here we present the continuous assessment of the autonomic function in the progression of HF. We could demonstrate the advantage of highly resolved ANS measurement by HR and BP derived parameters due to early detection of an autonomic imbalance in the progression of HF.
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The aryl hydrocarbon receptor (AhR), a classic “environmental sensor”, has been found to play an important role in cognitive and emotional function. Recent studies showed AhR deletion led to an attenuated fear memory, providing a potential target against fear memory, whether it is the consequence of attenuated sense of fear or memory ability deficit or both is unclear. Here this study aims to work this out. The freezing time in contextual fear conditioning (CFC) reduced significantly in AhR knockout mice, indicating an attenuated fear memory. Hot plate test and acoustic startle reflex showed that AhR knockout did not change the pain threshold and hearing, excluded the possibility of sensory impairments. Results from NORT, MWM and SBT showed that deletion of AhR had little effects on other types of memory. But the anxiety-like behaviors reduced both in naïve or suffered (tested after CFC) AhR knockout mice, showing that AhR-deficient mice have a reduced basal and stressful emotional response. The basal low-frequency to high-frequency (LF/HF) ratio of the AhR knockout mice was significantly lower than that of the control group, indicating lower sympathetic excitability in the basal state, suggesting a low level of basal stress in the knockout mice. Before and after CFC, the LF/HF ratio of AhR-KO mice tended to be significantly lower than that of WT mice, and their heart rate was significantly lower; and the AhR-KO mice also has a decreased serum corticosterone level after CFC, suggesting a reduced stress response in AhR knockout mice. Altogether, the basal stress level and stress response were significant reduced in AhR knockout mice, which might contribute to the attenuated fear memory with little impairment on other types of memory, suggesting AhR as a “psychologic sensor” additional to “environmental sensor”.
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This systematic review focused on heart rate variability (HRV) responses either during and after a water-based session or training. We included studies that assessed acute (during exercise and recovery) and chronic HRV responses to water-based exercise (WBE). The sample of the studies could be teenage (aged older than 10), with no maximum age limit, regardless of sex, health and level of physical activity. Studies that used compressed air devices (scuba diving), passive hydrotherapy, immersion only after exercise, or immersion without exercise were excluded. We performed this search during the second fortnight of July 2022 using the PubMed, Scopus, CINAHL, Embase, SciELO, SPORTDiscus databases, and a manual search. Two independent reviewers conducted eligibility analysis and data extraction. We used the “risk of bias” table, available in RevMan (Version 5.3), to assess the risk of bias for the selection, detection and attrition domains. The search resulted in 3528 articles, of which 20 became part of this review, totaling 317 subjects (240 in the acute effects analysis and 77 in the chronic analysis). There was great diversity in the characteristics of the exercise among the studies. Seventeen studies analysed the effect of a single exercise session, and three others analysed the chronic effect. Twelve studies compared exercises in- and out-of-water. When compared to the baseline, WBE and land-based exercises (LBE) did not affect parasympathetic modulation in five studies. On the other hand, two studies showed a lower parasympathetic modulation reduction during WBE compared to LBE. During post-WBE recovery, parasympathetic modulation was similar to other moments in seven studies and higher for LBE in only one study. Three studies showed a possible accelerated recovery of HRV indices post-WBE. Chronically, WBE resulted in better parasympathetic modulation in three studies. The assessment of risk of bias resulted in 75% or more of the studies presenting a high or an unclear risk in selection criteria, sample randomization and blinding outcomes for evaluators. Water immersion can influence cardiac autonomic modulation during exercise, with a lower reduction in parasympathetic modulation than LBE. WBE has positive chronic effects on cardiac autonomic modulation in people who have altered functions of the autonomic nervous system, although the number of studies is still scarce.
L’analyse de la variabilité de la fréquence cardiaque (VFC) est une méthode simple et facile pour évaluer le système autonome cardiaque et c’est un indicateur de la condition physique et de la santé. Plusieurs conditions peuvent provoquer des altérations de la VFC et les exercices aquatiques (EA) en font partie compte tenu de ses propriétés physiques.
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Nous avons effectué cette recherche au cours de la deuxième quinzaine d’avril 2020, en utilisant les bases de données PubMed, SciELO et SPORTDiscus, ainsi qu’une recherche manuelle incluant la liste de référence des études que nous avons trouvées. Deux examinateurs indépendants ont effectué une analyse de l’éligibilité et l’extraction des données.
La recherche a abouti à 990 articles (149 de SPORTDiscus, 787 de PubMed, 53 de SciELO et un d’une recherche manuelle) dont 16 ont fait partie de cette revue. Par rapport à la ligne de base, la EA et les exercices terrestres (ET) n’ont pas affecté la modulation parasympathique dans cinq études. D’autre part, deux études ont montré une réduction plus faible de la modulation parasympathique pendant la EA par rapport à la ET. Au cours de la récupération post-EA, la modulation parasympathique était similaire à d’autres moments dans six études, bien que plus élevée pour ET dans une seule étude. Deux études ont montré une possible récupération accélérée des indices VFC post-EA. Chroniquement, EA a entraîné une meilleure modulation parasympathique dans trois études. L’évaluation du risque de biais a abouti à ce que 75 % des études présentent un risque élevé ou incertain dans les critères de sélection et la randomisation de l’échantillon, et des résultats en aveugle pour les évaluateurs.
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Depressive symptoms were present in 62 (35%) and anxiety in 56 (32%) patients. Values of depression and anxiety significantly increased with higher NYHA class (P < 0.001). Depression symptoms were correlated with a reduced 6MWT (411 ± 128 vs. 488 ± 89, P < 0.001), higher heart rate (74 ± 13 vs. 70 ± 13, P = 0.02), higher thyroid stimulation hormone levels (1.8 [1.3–2.8] vs 1.5 [1.0–2.2], P = 0.03) and multiple HRV parameters. Anxiety symptoms were correlated with higher NYHA class and a reduced 6MWT (433 ± 112 vs 477 ± 102, P = 0.02).
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Review articleFunctional assessment of heart rate variability: physiological basis and practical applications

Abstract

Introduction

Section snippets

Physiological background of HRV analysis

Assessment of HRV by cardiovascular reflex testing

Time domain analysis of HRV

Frequency domain analysis of HRV

Comparison of time and frequency domain techniques for analysis of HRV

New analytical techniques

Practical applications of HRV analysis

Conclusions

Am J Cardiol

Am J Cardiol

J Diabetes Complications

Comput Methods Programs Biomed

Am J Cardiol

J Auton Nerv Syst

Am J Cardiol

Biol Psychol

Am J Cardiol

Lancet

Auton Neurosci

J Auton Nerv Syst

Int J Cardiol

Int J Cardiol

J Hepatol

Am Heart J

J Am Coll Cardiol

Am J Cardiol

Int J Cardiol

J Auton Nerv Syst

Am J Cardiol

Am J Cardiol

J Auton Nerv Syst

Am J Cardiol

Assessment of autonomic function: reflex testing or variability analysis

J Amb Mon

Heart rate variability

Clin Cardiol

Cardiovascular neural regulation explored in the frequency domain

Circulation

Heart rate variability—standards of measurement, physiological interpretation, and clinical use

Circulation

Heart rate variability from short electrocardiographic recordings predicts mortality from all causes in middle-aged and elderly men. The Zutphen Study

Am J Epidemiol

Low heart rate variability in a 2-min rhythm strip predicts risk of coronary heart disease and mortality from several causes. The ARIC Study

Circulation

Cardiac autonomic function and incident coronary heart disease. A population-based case-cohort study: The ARIC study

Am J Epidemiol

Multiple metabolic syndrome is associated with lower heart rate variability: The Atherosclerosis Risk in Communities Study

Diabetes Care

Impact of reduced heart rate variability on risk for cardiac events: The Framingham Heart Study

Circulation

Electronic evaluation of the foetal heart rate patterns preceding foetal death

Am J Obstet Gynecol

Sinus arrhythmia in acute myocardial infarction

Med J Aust

RR-interval variation, the QT interval index and risk of primary cardiac arrest among patients without clinically recognised heart disease

Eur Heart J

The natural history of diabetic autonomic neuropathy

Q J Med

Heart rate variability in relation to prognosis after myocardial infarction: selection of optimal processing techniques

Eur Heart J

Power spectral analysis of cardiovascular variability in patients at risk for sudden cardiac death

J Cardiovasc Electrophysiol

Prospective study of heart rate variability and mortality in chronic heart failure: results of the United Kingdom Heart Failure Evaluation and Assessment of Risk Trial (UK-HEART)

Circulation

The influence of autonomic neuropathy on mortality in insulin-dependent diabetes

Q J Med

Self-organisation in non-equilibrium systems

Assessment of cardiac autonomic function

Br J Cardiol

Clinical applications of cardiac autonomic assessment

Br J Cardiol

Autonomic assessment of cardiovascular disease

Hosp Med

Sympathovagal balance. A critical appraisal

Circulation

Power spectral analysis of heart rate and arterial pressure variabilities as a marker of sympatho-vagal innervation in man and conscious dog

Review article
Functional assessment of heart rate variability: physiological basis and practical applications