A Quantitative Systematic Review of Normal Values for Short-term Heart Rate Variability in Healthy Adults

David Nunan, Ph.D.; Gavin R. H. Sandercock, Ph.D.; David A. Brodie, Ph.D.

Disclosures

Pacing Clin Electrophysiol. 2010;33(11):1407-1417. 

In This Article

Abstract and Introduction

Abstract

Heart rate variability (HRV) is a known risk factor for mortality in both healthy and patient populations. There are currently no normative data for short-term measures of HRV. A thorough review of short-term HRV data published since 1996 was therefore performed. Data from studies published after the 1996 Task Force report (i.e., between January 1997 and September 2008) and reporting short-term measures of HRV obtained in normally healthy individuals were collated and factors underlying discrepant values were identified. Forty-four studies met the pre-set inclusion criteria involving 21,438 participants. Values for short-term HRV measures from the literature were lower than Task Force norms. A degree of homogeneity for common measures of HRV in healthy adults was shown across studies. A number of studies demonstrate large interindividual variations (up to 260,000%), particularly for spectral measures. A number of methodological discrepancies underlined disparate values. These include a systematic failure within the literature (a) to recognize the importance of RR data recognition/editing procedures and (b) to question disparate HRV values observed in normally healthy individuals. A need for large-scale population studies and a review of the Task Force recommendations for short-term HRV that covers the full-age spectrum were identified. Data presented should be used to quantify reference ranges for short-term measures of HRV in healthy adult populations but should be undertaken with reference to methodological factors underlying disparate values. Recommendations for the measurement of HRV require updating to include current technologies.

Introduction

In 1996, the European Society for Cardiology and the North American Society of Pacing and Electrophysiology supported a Task Force which issued a seminal paper: "Heart rate variability: Standards of measurement, physiological interpretation and clinical use" (Circulation, 1996; 93, 1043–1065). Reference normal values for short-term measures of heart rate variability (HRV) in healthy adults were published as an appendix to the paper. Some of these values, however, were approximated from studies involving small sample sizes. As a result, these data are considered as "unsuitable for definite clinical conclusions to be drawn from."[1] The Task Force stressed the need for large prospective population studies to establish normal HRV standards including age and sex subsets. This need was considered greatest for HRV values obtained from short-term recordings.

The interest in HRV as a measurement of autonomic function lies in its clinical importance. A reduced HRV is a powerful and independent predictor of an adverse prognosis in patients with heart disease[2–4] and in the general population.[5,6] Despite the important prognostic power of HRV, it is still not a widely used tool in clinical settings. Key issues relating to this fact include the most appropriate analysis method(s), the recommended length of electrocardiogram recordings, and the conditions in which they should be assessed.[7] Arguably an additional key factor is the lack of agreed normative values for HRV, without which classifying "abnormal" HRV remains difficult. In the majority of other clinically health-related measures (e.g., blood pressure, heart rate, forced vital capacity), established norms are routinely compared to provide an indication of current health status. There is no clear explanation why this is not the case for HRV.

Since 1996, publications assessing and reporting both 24-hour and short-term HRV in healthy and clinical populations have increased. Pinna and colleagues[8] report an increase in the number of yearly publications from 391 to 584 in the period 2000 to 2006, respectively. Taylor and Studinger[9] reported an average of 10 articles related to HRV published weekly during 2005. These "newer" studies provide a potential source of normative data for common HRV measures in healthy populations. Moreover, by comparing values between publications, it may be possible to identify factors contributing to discrepancies in HRV values.

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